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Possible Duplicate:
  Arduino has an input value in disconnected pin

I wish to measure the voltage of a 1.5V battery using a microcontroller (supply voltage of 3V).

I thought of connecting the battery on the ADC4 input of the microcontroller, and wrote a program which reads the ADC4.

Initially, I programmed the microcontroller without connecting the battery to ADC4. I was expecting to get a value of 0V (nothing connected to ADC4), but I didn't. Instead, I am getting a higher value which is also fluctuating. I tried to measure the voltage on ADC4 with a voltmeter, but I can't get a reading since it is obviously fluctuating. Why is that happening?


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I know it's been asked 1,000,000 times how/what/why transistors work and I feel like I've read every answer but I still struggle with the basics. The struggle for me is the difference between transistors for switching and transistors for amplifying.

For switching, I gather that the base needs a certain voltage to allow the current to travel through. Say the voltage required is 1.5 volts and you give it 15 volts, does that affect the current between the collector and emitter?

For amplifying... Can only specific transistors amplify and specific ones switch? Also, one of my biggest challenges is grasping exactly how it's amplifying because it feels like something from nothing. I guess a good example logically is an electric guitar. You have a low voltage signal from the guitar and a high current feed to amplify it. Now are you using the power of your high current feed and in a sense mixing it in with you guitar signal to boost it? Also, if you had a pot to adjust the signal amplification, what exactly would you be adjusting, the current or voltage supplied.

Lastly I read that you can increase voltage and current with a transistor. Is this only in the case that the supply is of greater voltage and current that the signal being amplified? Is it possible to increase voltage and current above that of any of the supplies?


texts: Operation Amplifier with Transistor output

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Is there a name for feedback amplifier topologies which include an opamp and transistor in the feed-forward path?. I need to design an amplifier with high bandwidth (almost 100 MHz) and high gain (50) and I think that I am better off getting most of my gain from a transistor.

I'm looking for literature on how to properly bias the transistor.


texts: How to minimize characteristic impedance mismatches caused by vias?

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This question springs from an answer here.

When using stripline configurations for rf signalling, the conductors are routed on an inner layer of the pcb, sandwiched between two ground planes.

I understand that vias cause mismatches in the characteristic impedance, which I would like minimize.  My frequencies are 2.4 GHz and 3.5 GHz.

Which aspects should I consider when carrying rf signals through vias?  For example:

Drill size
Annular ring thickness
Distance from rf source
etc?


texts: TinyFPGA / Lattice Semiconductor --- field-ready, or just hobbyist toys?

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These FPGA chips look interesting, and the Sparkfun TinyFPGA boards with them also look interesting. (e.g., https://www.digikey.ca/product-detail/en/sparkfun-electronics/DEV-14828/1568-1915-ND/)

Typical microcontrollers (MCU) have on-chip flash memory;  I program them (i.e., flash the firmware onto the on-chip flash memory), and voila!  Whenever the MCU gets power, it executes that program.

Does it work like that with these FPGA chips?  Or are they volatile, where I flash them and they operate only as long as they have power?

In case they're volatile --- is it easy (and does it make sense) to have them next to an MCU (presumably connected via I2C or SPI), with the MCU's firmware responsible for flashing the FPGA at boot time?


texts: If I have a Li-Ion battery with 3 terminals and do not wish to monitor the thermal pin do I need to pull it low or high. When I measure the battery from white to red I see positive volts as do I between black and red. I assume therefore that I should either leave the white wire unconnected or connect it to the black (negative) connection. Please can someone either confirm or explain what should be done.


texts: H-Bridge with Darlington BJTs, static shoot-through

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I have built the following H-Bridge with TIP122 and TIP127 Darlington BJTs:

It is made from parts I had around, and I plan to use it for currents up to 2A with a VCC of 12V. Note that 1N4937 diodes are marked as Schottky in the schematic, but in fact they are 'normal' fast rectifier diodes.

The bridge, breadboarded for testing purposes, works as expected in 'forward' (Q1 and Q4 switched on, Q2 and Q3 off), 'reverse' (Q1 and Q4 off, Q2 and Q3 on) and 'free' (Q1-4 off) modes.
Some delay is needed when switching from forward to reverse to let the humble TIPs turn on/off and avoid dynamic shoot-through, but the bridge handles well the 12V VCC and 300mA of current needed by a 'test' DC motor.

On the other hand, when trying to brake the motor by setting Q1-2 off and Q3-Q4 on, one of the two high-side TIP127s turns on and allows a considerable current to pass (more than 1A), thus overheating.

I have breadboarded the circuit several times, swapping and replacing about every component, and the issue is still there. Only one thing seems to change between rebuilds: the high-side TIP127 that turns on when it shouldn't. Sometimes it is the left one, sometimes the right one, and sometimes the braking works as expected, but only until I turn the supply off and on again.
Note that there are not significant resistance paths between VCC points and ground points.

Can the problem have to do with breadboard characteristics (capacitance)? Or are there any latent design flaws in the circuit?


texts: Why does the Vs node always oscillate around the second harmonic in a VCO tail filter?

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Why does the Vs node always oscillate in the second harmonic even if we detune the Cf, Lf tail filter?
Is Acos(2wot) always valid for Vs?
How is it explained?


texts: Why does using a transistor as a switch not work?

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I have a video game controller that I want to control with an Arduino.  The PCB has two pads for each button, and connecting those two pads "presses" the button.  I have attached a picture of what the pads look like.
Right now I am controlling the flow between them using a relay.  But before using a relay, I connected a BJT (a 2N 2222A -1726) having the collector on one pad and the emitter on another pad.  However, this did not work and I can not figure out why.  I am relatively new to electronics so this might be a simple misunderstanding.  The battery that is powering the PCB in the controller is 3.7V 1,300mAh 5Wh.  So my questions are:

Why doesn't the transistor work?
Should I use a relay or a transistor for this purpose?

EDIT: I looked online for a schematic but I could not find any unfortunately, although maybe I am just not looking in the right spot.  The controller is a Nintendo Switch Pro Controller.


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I have a doubt on how exactly a reflex klystron works(as an RF source). In wikipedia it says that,

  The electrons are fired into one end of the tube by an electron gun. After passing through the resonant cavity they are reflected by a negatively charged reflector electrode for another pass through the cavity, where they are then collected. The electron beam is velocity modulated when it first passes through the cavity.

I don't understand how the velocity of the electron is modulated when it passes through the cavity for the first time. It's not clear from the diagram given there. Also what is the purpose of U1?


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I am trying to figure out the natural frequency and the time constants of a transfer function. Ignoring the numerator and using the denominator of the second order characteristic equation:

$$s^2+2\zeta\omega_ns + \omega_n^2 $$

where $$\zeta=0.5, $$ $$\omega_n^2 = \frac{100}{\tau_1},$$

and  $$2\zeta\omega_n = \frac{1+100\tau_2}{\tau_1}.$$

$$s^2+\frac{1+100\tau_2}{\tau_1}s + \frac{100}{\tau_1} $$

How do you find the value of natural frequency without knowing the tau constants?  Is it even possible? It seems I have two equations with three unknowns? EDIT: Am looking for an actual number.


texts: Why would Z/P cancellation with real part > 0 between the plant and the controller make the system unstable?

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Can someone help me verify the claim if there is a zero pole cancellation with real part > 0 between controller Gc and plant Gp, then the system is not stable?

I can't find any literature that confirms or denies this claim.


texts: Couldn't find the answer on the internet. The leads of VZ1 component are directly connected to mains.


texts: Unidirectional vs Bidirectional TVS on USB devices

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Is there a reason to use unidirectional TVS diodes over bidirectional TVS on USB circuit protection apart from cheaper cost? As USB is a DC powered circuit, I feel like unidirectional TVS diode (such as Zener / avalanche diode) is the one to use. However, I'd like to check if this is a reasonable conclusion before I add a pair to my D+/- lines.

Doing some search, I ran into this article which goes into much details about electrical properties of both but failed to mention when or how to use one versus the other.


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I'm using a step-up DC/DC converter (https://www.torexsemi.com/file/xcl101/XCL101.pdf)  in my circuit to boost a 1.5V AAA battery voltage to 3.3V. The 3.3V is powering an audio circuit, and I heard a lot of noise in the audio signal. I suspected the issue was a noisy power supply, so measured the 3.3V voltage on the scope, AC coupled:

Disregarding the spikes, the peak to peak ripple is about 40 mV. Would you expect this level of noise ripple at the output of a DC/DC step up converter?

This is the scope shot when I measured the AC coupled voltage across the battery by itself:

I'm not sure of the cause of the large spike, but it looks unrelated to the constant 40 mV noise on the 3.3V voltage.

This is the configuration I'm using for the 3.3V step up converter (from the datasheet):

The only thing I can think of that might help is using different capacitors. Right now I'm using ceramic 0603 capacitors (https://www.digikey.com/product-detail/en/murata-electronics-north-america/GRM188C81C106MA73D/490-7198-1-ND/3900421). The 3.3V step up converter's datasheet also recommends ceramic 0603 capacitors, however I noticed the specs for them indicate "Low ESL" (https://www.digikey.com/product-detail/en/tdk-corporation/C1608JB1A106K080AC/445-11201-2-ND/3948437). I'm not sure if using this recommended capacitor will make that much of a difference...could this be the problem?


texts: Switch seperate 12V circuit with Rasp Pi Zero

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I'm trying to use a Raspberry Pi Zero to control our apartment unit's buzzer phone (the thing that lets people at the building door in).

There is a momentary push-button that completes a 12VDC circuit, causing the door to be unlocked. I've attached leads so that when I touch them together, it does the same thing as pressing the button.

So far I've tried two approaches to wire this up to a rasp pi.

The first was with a single NPN transistor controlled by one of the +3.3V GPIO pins. Verified the circuit concept by controlling a simple LED circuit with the GPIO high or low.
Then I tried it with the buzzer, hooked the +12V from the buzzer to the collector and the 0V to the emitter. This didn't work, and caused some buzzing in the phone.

Next I tried this Opto-isolator breakout https://www.sparkfun.com/products/9118 in hopes that isolating the two systems would be more straightforward and eliminate the possibility of a ground loop. I also tried this with the LED proof-of-concept circuit. It was noticeably dimmer when going through the opto-isolator vs. not, and it didn't end up working out with the buzzer. I'm thinking it introduces too much resistance.

If you were doing this, what approach would you take? Is there any way I can modify my approaches to make something work?


texts: how to calculate kickback voltage for the inductor in a RLC circuit?

texts: I am designing an RLC circuit and can anybody suggest the method to calculate theoretically  the kickback voltage produced by the inductor to choose the flyback diode. I have tried simulating the circuit and measured the kickback voltage which was around 110 V in simulation.The following images consists of the circuit diagram IS there any theoretical method for calculating the kickback voltage without simulation. thank you in advance.


texts: How many alternatives does a 14-bit ADC have

texts: I am a bit confused what alternatives are or how to find out how many are in an ADC. The book I have wasn't much help and I need to find this out for a project. Does anyone know the answer or how to find out? thank you.


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Not brilliant pic but bigger
picture from UK vehicle wiring diagram, windscreen wiper motor.


texts: Postmortem: on a PDU with low Power Factor, why did all of our servers reboot?

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I am a Unix SysAdmin with a crude understanding of electricity.

We had this scenario: 4 dual-PSU servers were plugged into a ServerTech Sentry Switched PDU with PIPS with Y cords. The circuit is 208V/30A. Circuit load is under 1A, so that is 8 server-class computer PSUs drawing around 0.1A each. My colleague plugged an additional server (older hardware redeployed) into the PDU. While provisioning this system, he discovered that the four lightly-loaded systems had all rebooted.

We began investigating. This is when we found the Power Factor (PF) on the PDU was 0.75 "WARNING LOW" ... we unplugged half the server PSUs and the PF improved over 0.8. I filed an RMA with the server vendor for our defective PSUs. The vendor then reported to us that PF is low at low load, and that if we want to improve PF we should run the systems at higher load. Running a stress command on one server brings the PDU PF over 0.9.

The question we ask ourselves is:

  Is it reasonable that under these circumstances, that plugging in an additional system should trigger a state of temporary power failure on the low-load systems? Or, does this imply that the PDU or the server PSUs are defective?

As best I can make out, we exposed an edge case for our datacenter practices, and we should make a move to monitor PDU PF, flag when it is low, and take corrective action (like artificial load) when a situation like this occurs.

Addendum:

At Week 29, we had 4x systems with dual PSUs on the circuit, and we connected a new server, which is when the 4x systems rebooted. At Week 31, I disconnected half the PSUs to correct the PF warning. I will introduce PF instrumentation in the future.


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Is anyone aware of any tri-state logic gate families?

8-bit input AND,NAND,OR,NOR,XOR,XNOR with an enable selector?

Or is this too specific and requires a roll your own implementation?


texts: Non-diode OR-ing solution for n equivalent power sources

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I wish to allow powering my circuit using at least one of 3 connectable periphals. For example, my application could have 3 usb ports that each connect to different usb hosts. Any combination with at least one connected periphal should be able to power the circuit, but obviously no current is allowed to flow back into any of the 3 supplies. The circuit should be able to draw 200mA at 5v.

Unfortunately, the voltage drop even from schottky diodes is unacceptable, so OR-ing diodes is not an option.

I've come across a lot of power mux IC's, such as the the LTC4412[1] and TPS22933a[2]. The LTC4412 still requires a diode at one of the power sources, and is only a 2-input solution. Still quite far from ideal. The TPS22933a seems like a better component for me due to the 3 inputs, but the maximum output current is rated at only 50mA (doesn't that make this thing utterly useless?).

Many of these power muxes offer niceties that I do not need:

no need for any kind of load balancing between the power sources
no need for a wide range of input voltages. All of them will be 5v.
no need to source from the highest available voltage source. Bias is fine.
not looking at a 3-input solution per se, expandability to n-inputs is desirable.

Given this, what kind of solution should I be looking at? Is there an IC that nicely accomodates my (seemingly simple) needs?

[1] http://cds.linear.com/docs/en/datasheet/4412fb.pdf

[2] http://www.ti.com/lit/ds/symlink/tps22933a.pdf


texts: Powering TL431 from MCU output possible?

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I'm designing a board with ATmega128 MCU. I have a TL431 reference connected to the ADC_REF pin, with both TL431 and the MCU connected to the same supply, 3.3 V.

Now I realized one problem - since the TL431 is connected directly to the 3.3 V, I don't have any possibility to switch it off to reduce power consumption, while the MCU is in sleep mode.

My solution, I came up with so far, is to power the TL431 from the output pin of ATmega, via a 390R resistor. This would allow me to switch off the reference before the MCU goes into sleep mode. At 3.3 V at the output, the cathode current would be 2 mA, which is sufficient, it should even work for output voltage as low as 2.9V (1 mA cathode current).

Are there some possible problems with this solution?


texts: How do electronic devices keep track of time without power?

texts: There's laptops, PCs, microcontrollers and a lot of other things that can be plugged out and plugged in without a battery. But how does the system clock still keep track of time without anything to power it?


texts: Why does my laptop emit electromagnetic radiation when charging (only)?

texts:
I have an electromagnetic radiation detector that I've been playing with recently, going around the house and testing various appliances, and I noticed something weird.

When I charge my laptop (or phone or tablet, for that matter) they emit electromagnetic radiation. When I don't charge them, they don't emit anything. Even if I use them.

I would expect the laptop to emit something while on battery power, but it doesn't. And I don't understand why it emits only when I charge it since the charger is a few feet away from the laptop.

Is there something in the laptop battery that emits that electromagnetic field? Why doesn't it do the same when the laptop is not charging?

I'm playing with a cheap DT-1130 Electromagnetic Radiation Detector


texts: Connecting linear Hall Effect sensor directly to microcontroller ADC

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I am planning on connecting an Allegro A1318 Hall Effect sensor to a 12-bit ADC on an NXP LPC1751 micro.

My application is to compare relative differences in magnetic fields between various magnets. I don't need to detect a changing magnetic field, so I have no need for a high sample rate. I need to measure up to 60 milliTesla (600 Gauss).

Some output characteristics of the sensor:

The DC output resistance is low (typically less than 1Ω) due to the internal amp, I believe, and I think that's a good thing.

The Output load resistance is specified as 4.7 kΩ minimum. I believe this means the load must be this value (or higher) for the output to remain stable. Likewise, the load capacitance should be less than 10nF.

The typical application circuit shows this \$R_L\$, along with a suggested output capacitor of 4.7 nF.

The ADC characteristics:

ADC interface block diagram:

\$C_{ia}\$ is specified as 15 pF maximum. Does this mean the ADC will "add" 15 pF of capacitance to the line while sampling?

The ADC on the NXP micro is multiplexed between many inputs, but I only need to use a single input. Do I have pay attention to the value of the sampling capacitor inside the micro? (I read through this TI app-note on multiplexed ADCs and I think I don't have to worry about the sampling capacitor really.)

I think I can connect the sensor, with \$R_L\$ = 4.7 kΩ and \$C_L\$ = 4.7 nF, directly to  the microcontroller ADC without using a buffer. Is this correct?

Follow-up: *I implemented this circuit without any loading resistor and it operated just fine. *


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I am reading the datasheet of the HEF4894BT.
First I saw the input clamping current is rated at 10mA and than I saw the input leakage current would be 10mA, too.
I thought the input clamping current is the current at which the IC is getting damaged and the input leakage current is the current which normally flows if I apply 5V or 0V to the input pin.
So 10mA input leakage current is wrong (Typing error)?
I am also wondering about the big amount of the leakage current.
On other datasheets its normally much smaller.


texts: Confusion understanding transient behaviour?

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I am trying to simulate PID controllers in MATLAB Simulink, but I am bit confused by the term "transient behaviour" in how its extreme highlighted forms (aggressive and robust) will affect the system response?

Here in this context, what will be the meaning of aggressive and robust?


texts: Oscilloscope alligator clip vs spring noise

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I am measuring the the power supply rail provided by a small integrated isolated DC-DC converter taking 5v to 15v. The package looks like as follows:

When I measure the output using an oscilloscope probe using an alligator clip for ground I get about 400mVp-p switching noise, but when I use a ground spring on the probe at the same probing locations only around 50mVp-p of noise is present. This can be seen in the photo below:

Is this because the alligator clip lead is picking up noise radiated from the DC-DC converter package as opposed to noise coming through the actual rail?
What can one do to reduce the effect of this phenomenon?


texts: Can one apply 5v to the output/FB pins of an LM2596-5 without causing harm?

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I am currently designing an SMD PCB with an atmega328P. I want to able to feed this circuit using below schematic.

In the past I have had certain heat development issues with arduino boards and all kinds of DC DC converters. The atmega is to be programmed and fed by an ICSP connector. That means I am going to apply 5V to the OUT/FB pin of the LM2596.
Looking at the capacitors and the schottky diode it would be safe. I have however no clue if the LM2596 will do harm. I won't be applying power to the J9 connector at the time of programming.
So with regards to the atmega chip's VCC pin (and the ICSP 5v), should I use an extra schottky diode to be safe or am I just fine without one?


texts: Solid state relay Crydom D1D07 closes and remains closed

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I have a Crydom D1D07 solid state relay and the control side is a +5 V DC on terminal 3 and a +3.4 V DC (don't ask) on terminal 4.

When terminal 4 is switched to ground (from +3.4 V DC) the SSR closes and the output side closes and passes the voltage as expected.

However, when the control side goes back to +3.4 V DC from ground the SSR does not open but remains closed and so the output side continues to pass voltage.

SSR:

The minimum on voltage is 3.5 V DC
Minimum input current is 10 mA for on state
Must turn off voltage is 1 V DC
Impedance is current regulated

It seems the must turn off voltage is not being met.

Adding a 370 Ω resistor to the terminal 4 side corrects this failure above but I still do not see how it does. The math does not compute. I think the voltage goes from 3.4 V DC to 3.7 V DC with the resistor added.


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For battery powered application I would like to control power of GSM module and GPS electrically with a TIP120 because GSM can be up to 2A (max_Ic current) and min < 10mA.

So I would like to know what is the best value of base resistor and the calculation because i learn the electronics by myself. I see on internet the value of 1K, this value can be allow > 500mA for collector emitter ?

My Arduino can be up to 25mA and VCC about 3.4-4.2V ( depend on battery voltage ).

Thanks for your help.


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I consider only an ideal transformer here (no leakage etc.).
Let L1 and L2 be the induction coefficients of the primary and secondary resp., and M be the mutual induction coefficient. Assume that the primary has n1 turns, and the secondary n2 turns.
Finally, assume that the secondary is connected to an (complex) impedance Z. What is the complex impedance of the primary ?
Put in another way, if we see the primary of the transformer whose secondary is wired to Z as a dipole, what is its complex input impedance?
I believe there should be such complex impedance, because all the components are passive and obey common law of induction.
After a lot of research on the web, I found only the following article that would provide approximatively an answer to this question; unfortunately, I found it unclear in many aspects:
Couplage magnétique etc.
Since this question is theoretical, everything I have not specified can be introduced as a parameter, and the question can be reduced if needed.
EDIT: The terms "ideal transformer" are contradictory with the finite values of L1 and L2 given in the question. Indeed, according to several documents, an ideal transformer is one for which L1 and L2 tend to infinity, while the ratio of the wires remains constant.
For such ideal transformers, the answer has been given by user1582568. For non ideal transformers (L1 and L2 have finite values), 3 formulae were derived mathematically in my own answer below: the first one is the general case (but is still theoretical because it neglects the inner resistance of the self, and other type of noises). The second one is for 100% coupling (but finite L1 and L2), and the third one is the ideal transformer already given.


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I am currently undertaking a power electronics course. I am analysing the buck-boost converter circuit and cannot find the correct inductor volt-second balance equation.

The circuit is as below

With the switch in position 1 i get the inductor voltage equal to the source voltage V_g

With the switch in position 2 i get the inductor voltage equal to the load voltage, V

But surely this should be a negative voltage as it inverts the voltage but the conventions must be kept the same for KVL?

How does this produce a graph of negative output voltage when there is only positive voltages with this convention?


texts: How long can room light shine on the board after exposure before board becomes useless?

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For the positive photo-resist method of making circuit boards, I use UV blacklight to expose the board (with the artwork on it) for an hour, just so that I can make 100% sure its exposed properly.

Because the photo-resist layer on a circuit board is sensitive to light, what I like to know is, from the time I turn off the UV blacklight (to finish the exposure), how long can room light shine on the board before the board renders useless when it is being developed in a standard PCB developer solution?

or should I be super paranoid and work in a pitch-black environment starting from the moment the board is finished being exposed until I successfully predict the moment that the unwanted photo-resist is removed?

I ask this because I keep failing at making circuit boards from using the standard sodium hydroxide developer, and I'm looking into ordering sodium silicate, but until I get some, I'm trying to understand if working in pitch-dark settings actually makes a difference.

If not, then I'll ditch the sodium hydroxide and wait for sodium silicate.


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There may be several points in this question which may not make sense to a knowledgeable person, so I do thank you for your understanding in advance.

For a computer vision project I wish to process images from a camera array (10s of cameras) simultaneously and we wish to jam image data to GPU memory as fast as possible, with RDMA or NVIDIA's gpuDirect. There exist cameras with SDI outputs and SDI capture pci-e cards with said direct GPU memory access, however, a setup like this may end up being quite expensive.

From the cost aspect USB cameras we are considering seem to be a solution, however, I am yet to find a USB host pci-e card that can support RDMA or gpuDirect.

(1) Have any of you seen a product that can support such direct access schemes? (Maybe something that emulates driver of the camera one end and can directly write to GPU memory via pci-e)

(2) Is what I am looking for even technologically possible?
When I contacted a USB host pci-e card manufacturer I have received the following response that I cannot even interpret:

  All our USB 3 controllers follow the xHCI specification published by
  Intel:
  https://www.intel.com/content/www/us/en/io/universal-serial-bus/extensible-host-controler-interface-usb-xhci.html

  When data is transferred from a usb device, the controller is given a
  list of address/length pairs where the data should be written.  The
  the controller will issues a PCIe MEM_WR to the address it is given
  with the data.  I hope that helps you decide if you can do what you
  want with our host controller

So do you guys think it  is possible or not (By possible I do not mean designing my own custom usb host capable of only doing what have described but with what's available already in market)?


texts:
In the datasheet they mention the MT3608 can handle up to 2A however in some stress tests with a load tester it gets already very hot at 1A. It is so hot, it is impossible to touch the board, all components around it get very hot because it spread all of the heat via paths. The chip itself is that tiny it is almost impossible to attach a heatsink. Because I don't have a second one I have to ask this, is this normal or abnormal?

Board (arrow point at chip and I have the one with protection diode):

Test config:

Battery 18650 2600mah
boost 4.10V to 5.6V (drops down to 4.87 when heated up)
Load 1A

Datasheet:

https://www.olimex.com/Products/Breadboarding/BB-PWR-3608/resources/MT3608.pdf


texts: Is it safe to bypass an LDO by shorting its input and output?

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I am making a programming adapter that will deliver 5V or 3,3V to the target board. I want to use a simple DIP switch to select voltage (I know that an SPDT is the canonical way).

Is it safe to short the input and output of an LDO like LD1117. Internal schematic is on page 3 of the datasheet.


texts: Design a 4-bit PISO shift register with 4 DFFs and 3 AND gates

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I want to design a 4-bit PISO shift register with 4 DFFs and 3 AND gates. I have gone so far that these two designs can be implemented, but I can't go further minimizing it so as to use 3 AND gates for the implementation.

If there is anyone having any suggestions I would appreciate it.

I have thought of another design but I didn't put it here because I think it limits the use of the shift register. Also I think that the second design is not right.

I think that there is another way to be implemented but I am not sure.


texts:
Please see the datasheet of Intel Broadwell-DE.

http://www.intel.com/content/www/us/en/processors/xeon/xeon-d-1500-datasheet-vol-3.html
(Eg datasheet-3 page 26: description of SUSACK_N)
"Intel® Xeon® Processor D-1500 Product Family-based platform doesn’t support Deep Sleep Power state"

What is this deep sleep mode?

Thanks
VT673


texts: Understanding an ultrasonic piezo driver circuit

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[Disclaimer: I'm okay-ish with digital electronics, but somewhat a noob with analog stuff. Since this circuit is a) pretty simple and b) still covers both areas, I was hoping that somebody here could help me clear up a few things].

I came across this circuit for driving an ultrasonic transducer:

originally from http://blog.mbedded.ninja/electronics/components/piezos. A similar circuit is also mentioned in https://electronics.stackexchange.com/a/22058/30433.

This fits my application scenario perfectly, but I have a couple of questions:

Why isn't there a diode between the LC circuit and the supply rail? Wouldn't the coil put some pretty nasty voltage spikes onto the supply rail, too?
As far as I understand, I could just as well use a MOSFET in place of the BJT (as long as it can also deal with the coil's voltage spikes), is that correct? In that case, I can also get rid of R1, correct?
The target frequency in my application is in the range of 19 - 21 kHz (slightly variable, the PWM will be adjusted accordingly). Should I try to tune the LC circuit to the center frequency of 20 kHz, or is that a waste of effort?


texts:
Can you tell me about this circuit elements' name more specifically? Especially number 1 and 10; what are they?

Number 1 text: SCC 068K275V-X2 MPXGMF 40/100/21


texts: The need for a current source in an emitter follower

texts: What is the need for adding a current source (\$I_\text{E}\$) at the output of an emitter follower topology at the emitter leg of the transistor?


texts: How can I find the slope at Vout/Vin at Vin = 0, from the datasheet about Op-amp?

texts:
I'm trying OpenModelica and I'm going to simulate an Op-amp.
(No it's not Windows 95, it's IceWM + Ubuntu 20.04)

But I wonder where I can find the slope Vout/Vin when Vin = 0 in the datahseet?
I have heard that the slope from an Op-amp is so large so not even the datasheet write it out. Is that true? Or can I find it?
Assume that we are using this datasheet:
https://www.mouser.se/datasheet/2/389/cd00001046-1795623.pdf


texts: Why does BLDC shaft magnetic field collapse when commutation occurs

texts:
I'm watching this video to try to understand motor control,
https://youtu.be/WYJWdMV3YMs?t=420
Here the video says that one of three phases would "collapse" in
its field strength when commutation occurs,
I think this is called Inductive Flyback.
Why does this happen?


texts:
I'm using HT (Half Transfer) and TC (Transfer Complete) interrupts in STM32 to do a ping pong buffer. I would like to find the RMS value of the array captured. Sampling frequency is 6 kHz and buffer size is 218. So during HT 108 samples have been captured and during TC the buffer is full with 217 samples. Clock is 16 MHz and I'm using only integers (not floating points). The point is to do all necessary calculations before the buffers fill again (since this is a circular buffer), but I think these are big load for the ISRs. I was trying to do all the calculations in the while(1) loop settings flags for HT and TC, but I noticed like a race conditions between the flags. The algorithm would be as below. Any recommendation on how to do this better?
volatile uint16_t ADC_buffer[218];
volatile int16_t ADC_buffer_zero[109];
//all variables used in the ISR are volatile

Initialize_DMA ();
Initialize_ADC ();

while (1){
}

ISR_HT () {
//Process buffer from 0 to 108
buffer_average(); //find average of samples
buffer_zeroed(); //subtract average from each sample
square_of_samples();
}

ISR_TC () {
//Process buffer from 109 to 217
buffer_average(); //find average of samples
buffer_zeroed(); //subtract average from each sample
square_of_samples();
}


texts: Implementing 3 to 8 decoder using 4 input NOR Gate

texts:
I have deduced the truth table to the required logic function, but I really need some advise on how I could implement it using a 3 to 8 line decoder, an inverter and a 4 input NOR Gate.

A3  A2  A1  A0  Z
0   0   0   0   0
0   0   0   1   1
0   0   1   0   X
0   0   1   1   0
0   1   0   0   X
0   1   0   1   1
0   1   1   0   0
0   1   1   1   1
1   0   0   0   X
1   0   0   1   0
1   0   1   0   X
1   0   1   1   1
1   1   0   0   0
1   1   0   1   1
1   1   1   0   X
1   1   1   1   0


texts: Help needed in selecting the power architecture for my project

texts:
I had some trouble in finalizing the power architecture for my upcoming project.
In a brief summary about the project, I am using a GPS device to acquire location of the vehicle and control two solenoid valves to spray  chemicals according to the location co-ordinates. The device will be turned on/off via a key switch.
Regarding the valves, they will be operated in a complementary manner. Like valve A will be in default on state and valve B will be default off. When valve B will be on, valve A will be off and vice-versa.
There is an additional third relay in the design but that is just as a future provision.
The confusion in architecture revolves around the relay circuits deployed to control these valves. There are two options, either to go ahead with a 5V relay or a 3V relay (coil voltage.)
The overall two architectures I need help in selection with are as below:

In power architecture 2, there is a separate 5V buck that powers the 5V relay's coil and the rest of control circuit is powered via a 3.3V buck.
In power architecture 3, there is a single 3.3V buck that feeds the control circuit along with the 3V relay coils.
Since the vehicle will be moving when the valves will be controlled on/off, the relays will be turned on/off at 5-10 Hz switching frequency.
Option 3 is the cheapest option.
I am worried that if I consider the power architecture 3, there may be issues like the coil switching may create some noise that will affect the supply line and eventually the controllers performance.
Wanted to know about all measures that can be taken to ensure sufficient isolation between the two parts of voltages coming out from the same source.
Though the relays definitely have free wheeling diodes across the coils I am still concerned that there may be some issues, which I wish to understand via the forum here.
The design's PCB will be a four layer board. The overall communication interfaces on the board at their respective speed is as follows:

Two possible ways I could think of are as below:
Option 1 is buck converter output to coils and via a common mode choke to rest of circuitry.

Option 2 is to add ferrite bead on each controller's VCC line. But that would break down the main VCC plane into several small planes which wouldn't be ideal.

What do you guys think?


texts:
Is there a safe or better way of using an AAA battery in place of an AA battery in small electronic devices/ sensors, when in bind like pandemic?

For possible use in small electronic devices without moving parts; remotes (IR, Bluetooth, RF etc) or sensors (temperature/ humidity type sensors) etc.

PS: Not using a motor, so this question title though similar, is not related.

There are plenty of sites/ you tube videos that talk about using an aluminum foil as a connector.

Given how it's a crumpled sheet and not a SOLID type connector, I would think it is subject to weird electrical properties (and hence not recommended), as compared to a SOLID connector.

Only if devices has some kind of "spring loaded" connector which allowed them to use "either" AA or AAA.

:) Wishful

(Although FireStick 4K remote connectors are nice cylinders (spring loaded) & not just thin coiled dpring wires (unless something of that type might help).

https://www.reddit.com/r/LifeProTips/comments/p1ejs/lpt_out_of_aa_batteries_use_aaas_and_tin_foil_in/

Is there a safe, decent, SHAPE/ OBJECT / MATERIAL that can be easily be used in place without the flaws with such hacks with foil?

Update:

So, the solution would revolved around:

Conductive item (preferably solid) to fill in for the Length & not dodge / wiggle around
Non conductive surround/ wrap around stuff to fill in for the Width an prevent dodge / wiggle around

Given the uncertain times ahead of us (this could have impact for 6-12 months on all kinds of supply), I've found both answers useful - and better than Foil ball. Open to more.

PS: We are in an asian city locality surrounded by Hot Zones - even medicine & food are hard to procure. A friends building, one case was detected - police lock down for 2 weeks now.

Is there a safe or better way of using an AAA battery in place of an AA battery in small electronic devices/ sensors, when in bind like pandemic?

Its not the time to be close minded or nit-picky given that both are decent solutions, if one ends up with AAA's at home (due large no of devices) and needs AA in a pinch.

One "adapter-kit" is something to keep, get if one is able to, for longer term, a must have that I was unaware of, given that AAA batteries & devices are common & around

(kinda like have all kids of screwdriver heads even if you rarely use a certain type),

Other - DIY w object or similar from home/ hardware (a bolt in linked SE answer)

Would appreciate more such "DIY" ideas with the decent "electrical properties", better than a foil ball.


texts: What could have caused bridge rectifiers to fail?

texts:
Ok, so I have a pioneer surround sound that I was trying to fix because of one speaker had very low volume. What I changed was a resistor, its the exact same color stripes, but the size is a bit bigger. When tested, the surround sound detected an error and went into protected mode. Until I forced reset it the 2 bridge rectifiers sounded like they exploded and there was leakage. The part number is D5SBA60 silicon bridge rectifier. I was reading online about the cause of it faling and there was 2 reasons. If the fuse did not blow, then I have an open. And if it did blow, then I have a shorted rectifier. The fuse did not open, so does that mean I still have an open in my circuit? What would I have to inspect before replacing the bridge rectifiers? The only thing I could think of is maybe a bad solder joint or could it have been a bad capacitor that leads to that speaker that caused this reaction?

Here is what I changed in blue circle, but the bridge rectifier is not near here.

Here is what I have found, I looked at pin 28 on IC501 (input volume selector) and it looked a bit black and I cleaned with alcohol and this appeared suspicious to me

So now the question is: Is the IC 501 the problem or before it or is resoldering pin for clean connection the solution? This is the most obvious problem I found so could this have been the cause? I checked on the schematics on page 86:

And here is what is going to INSBL2:

Schematics manual: http://www.mediafire.com/file/438o6iwkvfjlacy/Pioneer-VSX-1017TXV-K-Service-Manual.pdf/file
 I forced reset after putting bridge rectifiers and using correct resistor and it turned on, but no volume on speakers. Faulty IC501 (input volume selector)? The reason why the Pioneer system turned on and did not shut down is because I had some sound card loose, the first one I seated correctly was CN501, I turned it on and turned on a few seconds and turned off into protected mode.

Update: I do not have continuity from IC781 pin 1 to C789 positive side, but do have continuity to R797. Is this bad? Here I tested bridge rectifiers, are these good readings? https://youtu.be/GLbh0ko8Fzo


texts: Voltage Multiplier Frequency and Waveform

texts:
Note: I am aware of this question. It is 6 years old and I didn't find an answer there and I didn't want to necro the question.

As part of a school physics project I need a very large voltage.
I will be generating sparks in a low-pressure environment which will require at least 10kV (we still need to test the jars to see how low a pressure we can realistically maintain).

In order to generate the high voltages required I intend to use a Cockroft-Walton Voltage multiplier

simulate this circuit – Schematic created using CircuitLab

I've seen several values for Capacitors dotted around the internet and no explanation for them. According to this video its normal to use a square wave, again, no explanation. Most diagrams I have seen require a load resistor with a high resistance, I assume this is because of the inability for the circuit to produce high currents without discharging the capacitors.

My questions are these:

Is the resistor necessary if I'm using this to drive a spark gap? I would actually quite like the output voltage to drop when there is a load for safety reasons. (My classmates are not as respectful of electricity as I am.)
Are there any good resources with equations describing the relationship between the capacitances and the behaviour of the circuit?
What effect does the shape/frequency of the waveform have on the behaviour of the circuit?


texts:
Is there any difference if I switch places of R3 and C2?
Impedance and frequency response remains same as I understand. Is there something else?

Circuit source: https://www.circuitlib.com/index.php/schematics/product/43-needle-vu-meter/category_pathway-28


texts: Faster refactoring in Altium Designer 19: Quickly converting a circuit fragment to a new sub-sheet

texts:
In the process of refactoring a large schematic sheet into smaller, more manageable, hierarchical sheets in AD19 I have the following process:

Create a new schematic sheet for the sub-circuit and save it
Edit/Refactor/Move Selected Subcircuit to Different Sheet
Copy all connection net labels from new sheet to old
In the new sheet: manually convert net labels to ports
In the old parent sheet: add a sheet symbol, add sheet entries (using Sheet Symbol Actions/ Synchronize Sheet Entries and Ports)
Connect copied net labels to the new sheet symbol

This seems like it should be much faster... in fact, it seems like it should be 1 click in the refactoring menu (like what happens with Part Actions/Push Part to Sheet).  My process works fine, it's just slow and tedious now that I know how to better structure my design.

Is there a better way?  Are there some AD19 features I don't know about that will speed this up?


texts: Significance of the center-tapped transformers in mixer circuits

texts:
How does center-tapped transformer work on the circuit given below?
In analog rectifier circuits, one of ports of the center-tapped transformer is connected to a sinusoidal source while others are driven with a DC source or ground. But in mixer circuits as shown below, the situation is a bit different.
In RF usage of the center-tapped transformers, #1 node is driven with a small signal, "RF"; #3 node is driven with a large signal, "LO"; and together they prensent in #2 and #4 ports.

For example on a single balanced diode mixer center-tapped transformers are used as shown below.

At high side of the LO, D1 conducts while at the lower side of the LO, D2 conducts.
What does transformer do to perform such a operation? How do center-tapped transformers work when there are two sinusoidal sources?


texts:
I am simulating a current step in a buck converter with a resistive load that I designed. I am measuring the response while stepping the current up from 5A to 10A and stepping the current down from 10A to 5A.

It appears that the settling time is around double in the current step down scenario (~6ms) in comparison to the step up scenario (~3ms). Intuitively, I would've expected the settling time to be the same in both scenarios. Does anybody know why is this happening? Thanks.

The circuit:

Inductor current and output voltage in a step up from 5A to 10A:

Inductor current and output voltage in a step down from 10A to 5A:


texts: How to charge backup battery with single regulator?

texts:
Having single LM1117 regulator for 3V, how can I charge it whenever there is Vin and protect from discharging through regulator  whenever Vin is gone? It's for MTK GPS chipset which has VBackup pin.

Update with details:

Goal is to have a backup battery for GPS receiver to work more than 700 days without replacement, since there is no user access to device in order to replace it. Preferable cheap solution like 2032 or smaller battery with holder on PCB.


texts:
I am asking what happens, from the power/current consumption point of view, when I energize a relay.

In theory as relays are coils and like to hold current there shouldn't be a current spike when I energize it. But I am unsure what happens after that when it starts to attract the contact.

Example: If I need to size a transformer for some devices including 24VAC relays I just need to consider nominal power consumption/current of relays or should I consider some increase as for motor devices?


texts: Are TVS diodes necessary if device is not grounded? (i.e. portable)

texts: If I'm working on a battery powered device that has no connection to ground, is it still necessary to guard against voltage spikes?


texts: Puzzling behaviour from two inverters connected together

texts: I'm an electronics newbie and I am puzzled by the behaviour of a circuit I have created. I have connected the output of one inverter to the input of another but the behaviour of the circuit is not what I expected. I've included a schematic and two photos of the circuit. The first photo shows the two inverters unconnected and the circuit behaves as I expect it to, that is, LED1 turns off when I press the tactile button. However, in photo 2 you can see that I have connected the output of the first inverter to the input of the second and LED1 is off, but it should be on. Can you explain what is happening?


texts: SRAM memory cell - what kind of flip-flop

texts:
There is a classic 6T SRAM cell (image from wikipedia):

It looks like (two inverters in opposite directions and interconnected in and out) and works like some flip-flop.

But what kind of flipflop is closest to such SRAM cell? I mean, is it latch or flipflop? Is it SR- or JK- or D- or T-latch/flipflop? It it NOR- or NAND- or Gate- latch?


texts:
I've realised that several ICs with simple components, such as the FDS6690, provide duplicate pins in order to comply with a standard IC package (e.g. SOT23).
My question is - are these pins connected internally or one should do it on the PCB? Can I just use one of the Drain and Source pins?


texts:
I am designing a differential amplifier that will basically help me in measuring the current through a sense resistor of 0.015R.

Now the Vout formula is

$$Vout = {(R_f/R_i)*(V_2-V_1)} $$
\$V_2\$ - non inv voltage,
\$V_1\$ - inv voltage.

Based on this (i am using the ISL70218SRH op amp).
Now, the typical gain of this opamp is 130. I want to tune(!!!!) it to give a gain of 100. So Rf = 1000K and Ri = 10K. So gain = (Rf/Ri).

Now - from the Vout formula we can deduce that if the voltage difference (this is the drop across the sense resistor) is 0.03V, then

Vout = 100*0.03V = 3V.Right ?
But, when I do a spice simulation, the Vout is almost 4.8V.

V1 2 0 5
V2 1 0 4
*V2 7 0 3.3
R9 1 2 0.015
*R12 2 0 100000K
R8 1 4 10K
R11 2 3 1K
R7 4 6 166K
R13 3 0 166K
R10 6 0 1K
X1 3 4 1 0 6 ISL70218

.TRAN 1m 300m 1m
*.PLOT TRAN V(3)
.PROBE


texts: Why should I use DC coupling when I'm finding the frequency response of a circuit?

texts: In my last electrical measurements lab I was asked to plot the frequency response of several different filters (high pass, low pass, and band pass) using an oscilloscope. My professor told the class it is crucial that we use DC coupling - why is this the case?


texts: 240V to 110V using a Step-Down Transformer

texts: I was wondering if there is anything I need to be concerned about in regards to using a step-down transformer to power my Weller WES51 soldering iron which is rated at 110V in the UK (mains is 240V in UK).


texts: What resistance/ load do battery testers (AA or AAA) use in Ohms please

texts:
Trying to find out what size resistors (Ohms) a AA or AAA battery tester would use?
Have tried searching but unable to find an answer
I meant testing alkaline and ni-mh 1.5volt and 1.2 volt batteries and by battery tester I mean the devices that normally show whether battery is good low or need replacing.
Basically I am trying to determine what size resistor I should use to test the batteries mentioned earlier. And by size I mean Ohms and Watts


texts: Simulating SMPS with ideal switch in LTSpice?

texts:
Yes, this in a portion of a homework assignment (hence the idealized and slightly asinine problem statement).  Aside from solving the circuit (which I have done), I am supposed to simulate the following circuit using LTSpice.  The problem is that idealized switch in the middle.  I have tried using the voltage controlled switch built into LTSpice, but keep getting errors.

I am expecting a regulated voltage of (roughly) 50V.

I have tried simulated using a BJT with a square wave driving into the gate, but the result is highly dependent upon the voltage applied to the base.  When I simulate with a 5V square wave, I get roughly 18V at the output, but when I simulate with a 50V square wave, I get an output around 42V.

I tried simulating using a FET (similar to above, just swap in the generic NFET model) as well, but out an output in the microvolt range, which clearly isn't correct.  I also tried simulating using a voltage controlled switch, but I keep getting weird errors, I assume because the switch is only designed to be "thrown" once, not at a frequency of 200kHz.  It keeps telling me that it can't find a model for my switch, even though the .op is clearly listed:

If anybody know how to simulate a switch like these, my class mates and I would be very appreciative (especially since the professor simply said 'Ask Google' when I came to him after trying for several hours).

EDIT:

I just tried running the simulation again using an NFET.  It regulates to roughly 19V, which makes me think this isn't work either, consider the diode drop between the 20V source and the output.  I tried several different voltages to the gate, none of which made any difference in the simulation.


texts: Where to properly terminate 4-20mA cable shield in ungrounded low voltage DC system?

texts:
Preface:
I read both: ungrounded chassis shielding
and: RS485: Where to connect the cable shield in a battery-powered system?
A sensor system I'm working on is getting installed in a 20x20' cement room that also unfortunately houses VFDs and large HVAC equipment/fans.
I need to run various 15-20FT analog instrumentation cables from their install location back to the central transmitter box. The transmitter box is fed via an ungrounded 12VDC switching power supply.
The "current loop" part of this question has thrown me off. Traditionally, like in the threads above, you would have a signal wire, shielded and grounded (at the supply ground). Here, my negative return line IS my signal (NOTE: the cable is a single pair + foil jacket)
Presently, the 4-20mA loop is powered directly off the +12VDC input supply, and the return drops its potential across a 200ohm resistor at the signal input pad, to the board "ground" (DC supply ground, not earth).
My concern is: by essentially connecting my shield to the negative supply line, I will be introducing some of that noise from my shield directly to my sensitive analog signal at the board level as all the analog circuitry on the board obviously references this same ground plane. Are these concerns based in fantasy rather then reality? Am I just paranoid? Or are these valid concerns?
Thanks


texts:
So firstly i'd like to say I'm relatively new with electrical engineering, nothing more than backyard experience. However I am a computer programmer so I can grasp the concepts fairly well.

One of the problems I run into quite frequently in automotive modification is the need to change one voltage to another, or rather, translate it.

An example of this could be:(non-specific numerical range as an example)

if (input_voltage == 1.1) { output_voltage = 1.1 }
elseif (input_voltage == 1.2) { output_voltage = 1.7 }
and so on.

Additionally, this scenario may occur: (non-specific numerical range as an example)
if (input_ohm == 1) { output_ohm = 2 }
elseif (input_ohm == 3) { output_ohm = 7 }

An example of my current scenario can seen as follows.
Fuel pump signal supply to the gauge is sent through a potentiometer on a float in the fuel tank. Signal is sent to the analog gauge where its displayed.
Signal range can be anywhere from 0 (empty) to X. If i were to change the gauge, I would need to modify the signal to be within the parameters the new gauge expects while still utilizing the original sending unit.

My question is, is there some kind of user friendly programmable I/O logic board that I can use to achieve these types of conversion, or am I stuck with trying to create some rig of hardware to achieve the result?

Something like this would be perfect:
http://www.phidgets.com/products.php?category=0&product_id=1012_2

However i don't believe this unit can output a regulated voltage, it appears to just be a switch.


texts: Designing a gate voltage for N-channel MOSFETS for H-bridge controller

texts:
We have a project where our 2nd year students build an H-bridge controller from scratch.  They learn a lot about power dissipation.  We have a simplified design using IRF540 for the N-channel, IRF9540 for the P channel.  These are way over-spec for the application, tiny robot motors.  WE use 6V batteries, so to turn on the gate of the N-channel transistors we can use the output of the Arduino, and to turn on the gate of the Pchannel we set gate to 0V, or leave in a high-Z state with a pullup resistor.

This works.  However, we were thinking of extending the exercise to show all N-channel.  That's the way it's done at larger scale because the N-channel has such dramatically better on-resistance.  I think the difference is 0.004 ohms vs. 0.113 ohms, so it's significant.  This would require that we generate Vcc + 5V for the gate.

For a teaching circuit, with a power side of 12V, is there a simple, clean way to generate a tiny current at a voltage 5V higher than Vcc?  We would like to have them build the circuit, not just use a black box.


texts: How does active power factor correction in computer power supplies work?

texts:
I'm not looking for very detailed explanation (although it would be welcome). I'm more looking to intuitively understand how it works.

Basically in computer PSU I have input followed by filters followed by PFC circuit followed by switch followed by  transformer followed by rectified and in the end I have output filtering and consumer. From what I've read the same PWM circuit which controls the switch and regulates voltage at the output also controls the active power factor correction.

What I don't get is the way the power factor is actually corrected.

Here's a picture:

How do those two transistors work here and how would the PFC controller determine that the power factor is bad?

I know that the power factor is usually corrected with coils and capacitors and I see both here, but I don't understand what actually happens when one of the transistors starts to conduct, why two transistors are needed and how that affects the power factor.


texts:
I want to connect diodes in parallel to increase the current carrying capacity. If I connect two diodes in parallel having same rating(same forward voltage drop), does thermal runaway still come in picture?
If forward voltage drop is not going to be same for each diode then why so when I'm using same diode?


texts: smps block diagram and working for isolated topology

texts:
I have seen in most of the block diagrams of SMPS of isolated topologies, that the input AC voltage is first rectified and filtered to DC voltage.
Then, it is passed through a high frequency switch to form a square pulse, which is then stepped up/down using a transformer, after which, it is again rectified and filtered, before giving it to the output.
Also, a feedback is taken from the output, which is given to the controller, which gives the PWM to the high frequency switch.

My question is that, why are we rectifying the AC input in the beginning and then again inverting it to form a square pulse, before it is passed onto the transformer.
Can we directly give the input from the AC mains to the transformer, and then rectify it.


texts: Alternator with torque proportional to angular velocity

texts:
Im interested in buying or designing an alternator/electrical generator that increases torque as rpms increase - is there an alternator design that increases resistance as rpm/angular velocity increases? The alternator is for an exercise bike and would simulate real life pedal resistances.

I intend to collect the energy (however insignificant it is) to do something small like charge my cellphone.


texts:
I've built a circuit on a breadboard comprising a PIC18 reading from and writing to a HM6116 SRAM through a pair of 74HC595 SIPOs and a pair of 74HC165 PISOs. As you might expect, there are a bunch of parallel buses between the components. Here is my schematic:

I'm using the PIC's internal clock + PLL combo, as well as 8MHz hardware SPI with the 4 shift registers. As you can see above, the registers are cascaded to form 16-bit I/O ports for the address and data buses (multiplexed). I wrote some code to test the RAM: basically, write to the first 512 addresses, then read from them and print to the serial port for me to verify. My Proteus simulation works flawlessly.

But after painstakingly building the circuit and running the code, all I read back from the RAM are a bunch of random numbers though some seem to appear more often than others. Now, I've checked the wiring as well as I can (see jumble below), I've reduced the SPI frequency to 500 kHz, added 1 us delays in a few places in case somehow I dont meet setup and hold times (that is, if Proteus doesn't account for them). I still get gibberish.

So what I want to know is: How likely is it that the problem is due to the presence of parallel buses crisscrossing the breadboard and the resultant parasitics or EMI? Any other possibilities? I intend to order a 2-sided PCB, though only as a last resort, since they take time to arrive and are costly, given the size of my circuit. I also intend to add an Intel 8085 and an 8255 I/O chip to the bus eventually.


texts:
I've been reading about signal integrity and went through this site reading about it as well as other references. Alot of the topics deal with a single slave, but not so much multiple slaves.

I'll be working on something soon that will require multiple slave devices (I do not have a number yet), but for the purpose of this question, lets just assume the following

5 slave devices
1MHz clock
Max spacing between any two slaves is 15cm (if this even matters)

Questions

How should MOSI, MISO, CLK be connected (topology) ?
How should MOSI, MISO and CLK be terminated ? I heard that source termination is only good if there is one slave.
Would CS require termination as well ?


texts: How to connect a ENC28J60 or ENC424J600 to a KSZ8091 PHY and from PHY to an unmanged strapped configuration to a KSZ8863 or other switch

texts: How would one go about connecting MAC chip to a PHY and then to a switch for dual ports for daisy chaining? Rather be a strapped configuration for use in unmanaged mode so no need for MCU software changes and extra SPI and chip select lines on PCB for layout. Currently using a PIC24EP running microchips MLA TCP/IP stack using an ENC28J60 to a MagJack. Just looking for a simple solution and or reference design. Microchip has so many different chips and options makes it look to complex. Just want a dumb switch so can have dual ethernet ports instead of just one for daisy chaining devices together. Thanks in advance. Just want to keep the KISS principle.


texts: Can you find one of two resistances in a series circuit from the voltage, one resistance, and the voltage across the unknown resistor?

texts:
So I have a series circuit with two resistors...  One is serving as a current source for the unknown: a variable resistance.

Known are the voltage of the circuit, the fixed resistance, and the voltage across the unknown through an ADC.

Can I find the resistance of the unknown in real time from the voltage from the ADC?


texts: Connection of TRRS microphone not TRRS headset

texts:
I know for headset
T- Left
R- Right
R- mic
S- Ground
But for only microphone
T - unknown ?
R - unknown ?
R - mic
S - Ground
What are those unknown?
I want to plug it to my computer which has separate port for headset and mic.
I already have bluetooth headset. Thinking of buying mic. But most of them only have TRRS plug.
So I am trying to understand TRRS connection of microphone.


texts: KiCAD - Design rules for fabrication boardhouse

texts:
This is my first time designing a PCB with KiCAD.
I plan to send them to JLCPCB for assembly.
There are a ton of parameters to be set like track width, via width etc.
If these are set wrong, then the boardhouse cannot accept the Gerber files for fabrication.
Would the default values from KiCAD work, or do I have to set up specific parameters?
I ask because I think it's better to have this issue fixed early, and having the correct values set up from the beginning, before trying to fix things later.


texts: How to measure the current in a solar powered circuit?

texts:
This seems like a stupidly simple question, yet it's been troubling me for a couple of days.

I have a solar panel connected to an LED and an ammeter all in series.

The LED lights up, and yet the ammeter reads 0 amps? For the record I am using a multimeter that can detect current to the nearest 0.01 amp. (There is a separate jack to read smaller currents down to the nearest microamp but it can be assumed that the fuse is blown as when it is connected the LED no longer lights up and the reading is still 0.)

The purpose of this is to multiply it by the voltage (obtained from a voltmeter in parallel around the solar panel - this works fine) in order to calculate the power of the solar panel.

Help would be appreciated. Thanks in advance.


texts: Designing an ABBA circuit (3 input, 2 output) inputs: (GND, +V, Logic)

texts:
I'm working on a relatively simple Arduino project and want to reach an elegant solution for a circuit. I'm not sure if there is an existing IC for what I want to do, but here is a diagram for what I'm attempting to accomplish.

When googling the solution I found the name to be an ABBA circuit (tagged by minecraft sadly), essentially I have 2 inputs which need to be switched when a 3rd logic trigger is activated. Can I do this with a single device? Or is there a more complex solution?

More stats:
+3V line has ~170 mA of current
Logic Switch is a +5V line with ~47 mA of current (Digital pin)

Thanks for taking a look and I appreciate any help given.


texts: Identification of a threaded connector (on a speed sensor)

texts:
I'm trying to identify the mating connector for this speed sensor. The sensor in itself is a custom CNC job so no datasheet available...

It's got three pins and 5 "grooves". The exterior thread is a tad less than 1/4".

Subsidiary question : I think it is a hall sensor since it has 3 pins and the end is magnetic, any idea how to identify which pin is which?

Thanks by advance!


texts: Newbie Assistance - Understanding Fairy Lights

texts:
I'm VERY new to EE and am learning the basics. My first goal is wiring up some small lights for my son's LEGO projects, and am trying to sort out the basics here.
Right now, I'm attempting to piece together a mental model of how wiring up several LEDs work, mostly vis-a-vis attaching them to an Arduino. I've run into several hurdles here (seemingly a simple project) and keep coming back to the simplicity of a small strand of fairy LED lights.
The output of the Arduino is 5v. I'm comparing it to a strand of fairy lights I have which take 4xAA Batteries, for a total of 6V.
I've read the following:

A white LED needs about 3V to operate, and requites around 20mA of current to have decent brightness.
Each pin of the Arudino can only output safely 20 or 30mA. Thus, I can only safely run 1 LED, maybe 2 if I'm feeling risky, per pin on an Arduino.. Even if they're in parallel.
AA batteries can output about 50mA constant current.. 4 AA batteries would be 200 mA, no?
At the same time, this little pack of fairy lights on 6V can run like 50 white LEDs with no resistor as near as I can tell.

So how does the magic of the fairy lights actually work? What am I missing? Why is it that trying to wire up 6 little LEDs to my son's LEGO house is apparently going to require six separate pin connections, each with a resistor, etc.


texts: Does suface area affect thermal coupling design?

texts: I am building my own thermal couplings for a experiment I am doing at home. I want to build a very small thermal generator with them. At each contact point does the amount of surface area involved in making contact affect the amount of electricity being generated?


texts: Separation of an analog and digital power

texts:
I'm developing mixed analog-digital device for the first time and I'm not quite sure how to manage analog and digital power separation.
The device will contain:

MCU
Digital sensor
ADC
Analog sensors
Wi-fi on the chip

To be exact, the module that I'm using is TA3200R1A

I can't have more than one LDO or SMPS, to physically separate them, so I've been thinking about filter.

A little research of mine showed that the best (?) option is to use Pi-filter. but I'm somewhat worrried about the resonance.

What are the best ways to separate analog and digital power?


texts: Why does the length of an antenna, relative to the wavelength, matter?

texts:
I cannot understand following wikipedia illustration:

It shows the antenna at right angles to the direction of travel of the EM wave.  The wavelength is measured in the direction of travel.  So why does the relative length of antenna to wavelength matter?


texts: Differentiator circuit sees noise on PCB after 2 min

texts:
I'm new to PCB design, and looking for some advice. I designed a PCB shield and I'm seeing a lot of noise in my differentiator circuit. The circuit will run perfectly for about 2 min and then all of the sudden, a bunch of noise will disrupt the reading.

The circuit itself works just fine as tested on a breadboard, but not when its on the PCB. Not sure if this helps, but I've attached an image of the Board schematic as well.

I'm worried about crosstalking and temperature issues with temperature. I'm not sure if this is a common issue and I'd love some advice. Thanks.

EDIT1: Added schematic. The bandwidth I'm looking for is below 1 kHz. The power input is the 3.3 V supply and GND pins connected to my microcontroller (TIVA TM4C123GXL).


texts: Magnitude of fourier transform of AM signal

texts:
I'm taking a basis course in DSP and in class we had an exercise on amplitude modulating signal. we were given a signal \$x(t)\$ with fourier transform \$X^F (f)\$
with magnitude which looks like this:

now, the modulated signal, \$x_{AM}(t)=2x(t)\cos (2\pi f_c t)\$ has fourier transform: \$X^F _{AM}=X^F(f-f_c)+X^F(f-f_c)\$.
then, I saw in class that the magnitude of this fourier transform looks like this:

so it looks to me as if they implied that the relation: $$|X^F _{AM}|=|X^F(f-f_c)|+|X^F(f-f_c)|$$
holds. I think that the correct relation should be with an additional interference term.
Are there hidden assumptions for this signal which makes the above relation correct?
edit: to be more specific, if I write the magnitude of the fourier transform of the AM signal I get:
$$\scriptsize{|X^F _{AM}(f)|=\sqrt{|X^F (f-f_c)|^2+|X^F (f+f_c)|^2+2|X^F (f-f_c)|\cdot |X^F (f+f_c)|\cdot \cos(\angle X^F (f-f_c)-\angle X^F (f+f_c))}}$$
this means that the above relation holds iff \$\angle X^F (f-f_c)=\angle X^F (f+f_c)\$ so, why is it correct generally?


texts:
In the above Question, I am not able to judge the states of the Diode when Vs is at 10V.

Can somebody can explain me, how we can proceed in order to find the Vout.


texts: Barebone ATSAMD21G - start with IO on breadboard

texts:
In my quest to learn about microcontrollers, I did reach a result that for me is pretty exciting: I am able to upload code to a barebone ATSAMD21G, connected to a breadboard, using my ICE programmer. So far I was able to blink a led; which is basically the "hello world" of hardware, from what I understand.
I did write the code in Atmel studio.

Now the next step is to actually do something more, and so I am looking at IO. the SAMD21G uses SERCOM ports; which from what I can read on the datasheet, are programmable via muxing, so you have N pins, and X sercom ports, of which, each one has 5 pads to set IO as SPI, I2C or UART.

Now; the issue that I am facing, is that I can't find a tutorial that walk me through the configuration needed to actually use the microcontroller ports, for IO.

The examples on Atmel site, are related to their breakout board; same goes for other internet sources, that basically refer to their implementation of the SAMD21, without showing how did they actually end up there, with a config file set for the muxing, and with the bootloader on it.

My objective is to learn this, but I am having hard time to do so, since I have just a bare SAMD21, connected to the caps for power, a voltage regulator and the pins coming from the ICE (and a led now, yay!!); so I have no clue about what to do next, since it is not like loading arduino ide and start to code.

Any help would be really appreciated; if it is in detail and aimed at beginners, even better. I am fundamentally going in circle at this point, and learning on the reference board didn't give me any indication about how to do my configuration, sadly.


texts: compare rising edge occured before or after an other edge with verilog

texts:
I would like to write a verilog code to generate RTL level for signal B as in the figure. It has been a long time since I wrote verilog at school so I am quite rusty at this.
Let's say I have two signals A, B as in the picture and I need to generate the signal C with the description below.

The rising edge of signal C is determined as follows:

At the falling edge of signal A if rising edge of signal B is occured before falling edge of signal A.
At the rising edge of signal B if rising edge of signal B is occured after falling edge of signal A.(you may want to look at the picture to understand the rule easier)

The duty cycle of signal C is equal to duty cycle of signal A.

I am stuck at the part to compare whether the rising edge of signal B is occured BEFORE or AFTER falling edge of signal A.
Hope someone could help me on this.


texts: Making a USB port transmit wirelessly via bluetooth

texts:
Background:

I have an interactive board which I connect to my PC via usb. The usb connection of the board via pc is it's source of power. Any touch on the board is transmitted to the PC in the form of mouse movement.

Aim:
I want to make this wireless/via a Bluetooth.

Now,  I have NO knowledge of hardware at all.

From reading online, I would require a HC-06 Bluetooth module to transmit. After that I can pair the bluetooth from a laptop and read data from the port and move mouse.

My doubt is:

How to supply power?

Consider I connect a 5v battery to the Vcc of the module and somehow connect the HC-06 module to the usb of board. Will it be enough to power the board to work?

How to connect usb of board to HC-06 module?

Somehow connect the usb of board to the RX of the module. Or connect the usb of the board to ardunio(if that makes sense I don't know how to do this). Then connect the usb module to the ardunio.

Make provide clear detailed information due to my lack of knowledge.

Edit:
Any references links will be helpful. Using ardunio then usb shield connect to board. But to transfer data via bluetooth then


texts: Mobile WIFI: how close can mobile devices be placed and still have a functional WIFI connection?

texts:
I wish to run a large array (50+) of hacked Android phones as a computing cluster.  They will need to be networked so I plan to use their built-in WIFI radios to talk over a single WIFI network.  (I have looked into having wired network for the phones but it turns out its not very easy or cost effective)

I have not tried any of this out and I would like to get some feedback from the EE community to see if this would even work.

If I have the phones all stacked on top of each other (or maybe 5 stacks with 10 phones each - each stack placed next to one another), and I try to connect to a single WIFI network, will the WIFI connections for each device work at all?


texts: single or multiple interrupt handlers in stm32

texts:
I am coming from 8-bit world to 32-bit world specifically stm32f103.

At present I am only doing study and discussion with my fellows to know the major differences in the two worlds and also to select the IDE/compiler for myself.

Some fellows told me that stm32 have single interrupt handler routine. For example if there are 8 timers then there will be 1 ISR and once I am inside that ISR then I will check each timer to figure out which timer has triggered the interrupt.
Some fellows told me that it is IDE/compiler dependent. If I use Keil then i can use individual ISR for each Timer while if I use Truestudio/Cubemx then there will be 1 ISR as in case-1 above.

Can anyone clarify this?


texts:
I'm a little confused about why these exist and what their distinction between regular positive voltage regulators are.

It seems to me like if I wanted to get -5V from -12V and 0V, that I would connect a normal 7V regulator, with -12V to its GND and 0V to its \$V_{in}\$.

Is the current flowing in the other direction? The positive regulator would fry or cause an open circuit?


texts:
I am fairly familiar with the concept of metastability: You have two asynchronous clock domains, there is no way to guarantee that the data will be setup/held properly when input to a flip flop if it's clocked from a different domain (especially with differing clock frequencies that are not integer multiples of one another). The state of the register output will react unpredictably.

In a slow moving single bit case: Typical design will just pipeline some "protection" registers in the new clock domain before utilizing the signal, giving the metastable state time to resolve.

On a fast moving/wide bus signal it is not as simple. The unpredictable nature of metastability may cause some bits of a bus to settle earlier than others (assuming you can't perfectly match all register input trace lengths and perfectly match the register timings), which can look like glitches. In this scenario, designers can utilize a clock crossing FIFO to reliable pass data back and forth.

So what do the guts of a clock crossing FIFO look like and how does it get around the fundamental issue of asynchronous timing?


texts: Problems in 8W Audio Amplifier using TDA2002

texts:
I have made an amplifier using TDA2002 but it's not working properly.

Pot. R1 is not included in mine as it doesn't make a lot of difference and produces noise when I try to adjust the volume.
How can this be solved?

Above a certain volume set in the music player, the 8 ohm, 3 inch diameter speaker gives out distorted sound.
How can I avoid this?

If the 3.5 mm jack isn't connected to an MP3 player or any audio device, there's a buzzing noise from the speaker.
How is this noise produced and how can it be removed?

A friend suggested that I add resistors in series to the input and the output.  It din't work.
So he suggested that I add a buffer circuit to the input.
Will that help?

EDIT:   I'm using a 5V, 0.7A supply.

Here's the circuit diagram


texts:
In the datasheet of the Texas Instrument AMC1200 isolated amplifier the mention that C3 and C4 can be used to reduce "charge dumping".
What is meant by charge dumping? How useful are C3 and C4 in this scenario?


texts: Should the Unused Contact of a DPDT Relay be Connected in Parallel or Series?

texts:
I am designing a PCB which uses a 5-1462039-6 DPDT relay. I actually only need one of the relay contacts, but this relay was cheaper than any equivalent SPST relay I could find. Is there any advantage to connecting the second relay contact either in parallel (as shown in the picture) or in series? Or would it be better to just use one contact and leave the second unconnected?

I already know that connecting in parallel will not allow me to double the amount of current the relay can handle, since the two contacts might not switch at the exact same moment. One advantage to connecting in parallel I could think of is that if one of the contacts eventually became stuck open, the circuit would still work as long as the other contact still worked. However, if the contacts were more likely to become stuck closed rather than open, it would actually be better to connect them in series instead. Is one of these modes of failure more common in this type of relay, or is there any other advantage to either connecting the second contact in parallel, series, or not at all?

Edit: This relay is used as an auxiliary dry contact output. The user can connect the relay contacts to another device in order to trigger it to do something. The relay will be triggered by some sort of event, turn on for a configurable amount of time (usually no more than a few seconds), then turn off again.


texts: Dangers of building a radio transmitter?

texts:
As an educational project I am interested in building a radio transmitter (either AM or FM, probably AM to start) similar to the ones that you take in the car that can play your iPod.

The car transmitters have terrible range, however, and I want one that I can place in my house and will cover both stories. Ignoring the rage of the FCC (let's just say I'm out in the middle of nowhere), is there a danger of building a higher power transmitter? I've heard stories of large AM antennas being high enough voltage to kill, but I won't come close to that, right?


texts:
Why we use exactly 50 Hz and 60 Hz, instead of 100 Hz or even 400 Hz

1-is it for light

2-is it for the speed of ac motors

Can I use a machine that work in 50 Hz ac network, in 60 Hz network

This picture shows a motor of 15 KW 220-230V /50HZ this motor run a water pumpe
My question is: can this motor work in 60 Hz network without damage
Will it's speed increase


texts: Why does this current inrush circuit not work well?

texts: I've done some research and tried to implement a resistor and relay combination to limit current inrush for my power supply. How can this be improved as I am still seeing a peak of 85A at the smoothing caps?


texts:
I have an assortment of small speakers/piezo elements and I'd like to connect them to an arduino without damaging either. I don't know what characteristics the elements have or what to look for but I do have a basic multimeter.

What should I measure? How do I know which ones to just discard? Otherwise do I need extra resistors in the way? If so, what values?


texts: Open Drain while transmitting data with port direction output

texts:
I am new to this information portal!
However, I have question regarding open drain. I read that, in open drain mode, neither of the devices (slave/master) are allowed to drive the data line HIGH, they can only drive the line low, otherwise there can be cases where it may damage the controller as it may lead to shorting of the circuit. So in order to do this, when Master has to read the data being transmitted from slave, it changes the mode to HiZ mode and changes the direction to input. But my query is let's say master has to transmit the data (say data is 0xA5A5) on the data line which is being shared by the slave also. In such case will it cause any problem if mode is being already in HiZ, port direction as output for transmitting data 0xA5A5.? (i.e while transmitting 0xA5A5 master drives the line high also while being in the HiZ mode). So that when Master has to read the data, then it has do no mode change nor direction change as it's already being in HiZ mode, so that slave can drive the line low.

simulate this circuit – Schematic created using CircuitLab

Thanks


texts:
I read the paper "Simplified Analysis of PWM Converters Using The Model of The PWM
Switch", and I have some questions about the model of DCM (Discontinuous Conduction Mode) flyback.
This is in the DCM condition. and I would like to use PWM switch to model it.

1.) In this paper, about equation(3) I don't know why vac equal to VL, why it doesn't consider the Vin, it looks like neglect the Vin.


texts: How can I make traces end in squares in EAGLE CAD?

texts: Instead of the ending traces like the right one which is a semi-circle. How do I make traces end in flat edges in EAGLE CAD?


texts: Why do GPS receivers have a 1 PPS output?

texts: I was surprised to see that the GPS receiver I'm working with has a pin reserved for outputting a 1 PPS (Pulse Per Second) signal. What is the point of this? Can't the microcontroller easily generate its own 1 PPS signal?


texts: How to isolate charge circuit from drain circuit

texts:
I am installing a 5k winch on a car hauler trailer.  I will power the winch from a deep cycle battery permanently installed on the trailer.  I want to keep the battery charged by connecting it to the charge circuit from my trailer wiring harness.  The issue is that the winch pulls more amps than the charge circuit supplies.  What do I need to do to make sure that the power for the winch only pulls from the battery and not from the charge circuit?  I realize that I could just unplug the trailer from the truck when I use the winch, but I was looking for a more elegant and automatic solution.

Thank you all for your input and help.  It looks like my best solution is a manual switch.  I was REALLY hoping for something more idiot proof, but looks like this idiot will just need to learn to check the switch.

Have a great day


texts: How do I find the -3dB point on a given graph

texts:
I just performed an AC Simulation on QUCS and was asked to find values of gain and phase at low freq. and high freq and at the -3dB frequency point with the roll-off slope. The circuit is an RC circuit as shown below (image was taken from QUCS itself)

My questions are:

When I'm meant to mark low freq. and high freq., do I just mark 1e03 and 1e09? (plots shown below)
What point is the -3dB freq?
How do I get the roll-off slope - do I just calculate the gradient at the -3dB point or do I do something else?

TIA


texts: Locally hatched ground plane to increase differential impedance

texts:
I am designing a flexible PCB to carry two types of differential signals. One is about 1.2Gbps 100R differential impedance, while the other is only 3Mbps, with much more tolerance on the impedance.

It was very hard to achieve a differential impedance of 100R with such a thin dielectric, so it was suggested that I used a hatched ground plane to increase the impedance. However, it's hard to make the high speed pairs properly balanced on all parts on the hatching, since they go around some odd corners. Furthermore, the outer pairs are unbalanced all the way.

As an alternative, I was wondering about literally placing diamonds along the route of the pairs, like this:

This way I could achieve good balance for the whole route, and I could leave the outer pairs with a solid plane, rather than unbalancing them.
Lastly, I wonder if it's worth using circles instead of diamonds to reduce the stress concentration at the corners.

I wonder if what I am trying to do makes sense?


texts:
I am having an issue with clearances around pads and vias in EagleCAD, when milled on a LPKF S63 milling machine.  I am a student myself but in my final year, and helping out by making a small BoosterPack board for the TI Launchpads.

The board will be then be printed by the 1st semester students, and then soldered.  As they are new to soldering I wanted to give them extra clearance room around the pads.  So I have increased the clearance around the pads to 40 mils.  Now when I come to print the milling machine cuts an extra trace so there is 40 mils space from the ground plain, but there is still a small piece of copper left as an island in between.  See the image and the area's marked in red to help with the explanation.

The LPKF is a new machine so not got to grips with it fully, and unsure if I am missing a setting in EagleCAD, or if I need to check for an adjustment on the milling machine.
The next 2 images show the design rules settings, and also a small segment of the board layout in EagleCAD (grid settings 1.27mm).

So basically I want to remove all the excess copper remaining between the ground plain, and the outer edge of the annular ring.


texts:
I have a problem (stm32f407vgt6) with altium input output pin error. I will use 3.3 volt in my mcu that's why I added 5-3.3 voltage regulator in the circuit but I ve taken this error. Details

VCC0 contains Output Pin and Power Pin objects (Pin U1-5,Pin MCU-6,Pin MCU-11,Pin MCU-19,Pin MCU-28,Pin MCU-50,Pin MCU-75,Pin MCU-100)

output of voltage regulator is naturally 3.3 V but altium does not give a chance to use this volt as an input of mcu. what is the solution?


texts: Calculate voltage drop across Linear MOSFET in saturation region

texts:
Considering the below schematic, how is the voltage drop across the MOSFET calculated when it is operated in the saturation region? I am trying to calculate the power dissipated by the MOSFET so that I can choose an appropriate heat sink. RDS(on) is only listed for one V(gs) in the datasheet, but in this use case, the gate voltage will be varied in order to achieve a programable constant current through the MOSFET. For example, see the datasheet for IXTK90N25L2 which is designed to be used in linear mode. The "Input Admittance"  graph in Fig. 7 shows the relationship of V(gs) and I(D) but there is no V(DS) listed.
EDIT: I think I might be misunderstanding what the "Output Characteristics" graph is showing. According to this article, that graph is showing the voltage drop. But I don't understand how that graph is being read. Can anyone explain that?
Based on this article, when in the saturation region, the  drain  current is related  to the gate-source voltage and the threshold voltage and not RDS(on). Does this mean that the RDS(on) is always the same for all V(gs) that are above the threshold voltage? If that is true then the transistor in question would only dissipate 16.2W at its rated 90A (.18V=90A x 0.002 Ohm) but then why is it rated for P(D) = 960W?
After reviewing answers on this site (ie this one) related to MOSFET power ratings, they are all referring to switching losses which does not seem to be relevant here.


texts: Using gate driver MIC4427 with 24V supply

texts:
I would like to control LED strips using MOSFETs. I've got recommendation to use PSMN9R0-30YL and drive it using MIC4427. So I bought these, but right now, I'm unsure about two things - (a) how to actually use it and (b) how much current will this control consume.
(a) The LED strip (and power supply) is made for 24V. However the MIC4427 maximum supply voltage is 18V (absolute maximum according to the datasheet is 22V). I expect I've got bad recommendation, right? Or is there a way how to correctly use this pair of MOSFET with this gate driver? Maybe, if you can recommend me a better alternative to the driver. It's going to be feed with TTL PWM from atmega328 or similar.
(b) What's power consumption when using MOSFETs with gate drivers? Does it depends on PWM frequency?
Thank you for your hints and advices and sorry for little bit stupid question - I'm learning slowly.


texts: DIY Variable Power Supply With DC Motor Controller?

texts:
I currently have a variable DC power supply, a cheapo china one 0-30v 0-5A that can be constant current or constant voltage. It's helped me a lot until my recent project where I need 12v at 30A. A brand-name variable power supply of this capability costs $250-$600 and I'm just a poor college student.

The Question:

If I bought a $40 12v 40A power supply from Amazon or ebay or whatever, could a DC motor controller (PWM type) make that into variable voltage from 0-12V? Obviously there'd be no current readout or constant current capability, but I don't really need that for this project.

The DC motor controller:
http://www.ebay.com/itm/10-50V-40A-DC-Motor-Speed-Control-PWM-HHO-RC-Controller-12V-24V-48V-2000W-MAX-/370962506627?hash=item565f16a383:g:LusAAOxyFjNSORPa

Power Supply:
http://www.amazon.com/uxcell%C2%AE-100-220VAC-12VDC-Switching-Supply/dp/B00H8W6GKQ/ref=sr_1_1?rps=1&ie=UTF8&qid=1456433505&sr=8-1&keywords=12v+40a&refinements=p_85%3A2470955011


texts: Large load connected to small solar panel and battery

texts:
I have a smaller solar panel (say 12v, 0.5 amp and therefore 6 watts) connected to a 12v car battery (assume lead-acid) directly though with the included blocking diode, there is no charge IC attached. In full sun the panel will deliver up to 15v. What happens when a load (It must be assumed that the load isn't particularly voltage sensitive, within reason) in excess of the solar panels output is connected? For the example, lets say the load is 20 watts.

I would imagine that for a small load (below that of the solar panels output) the load would simply use the provided electricity from the solar panel (15v and whatever amperage) and the battery would charge at a lesser rate, however, once this load is exceeded, what occurs? Does the solar panel burnout? Does its voltage output drop? Or Does the battery simply provide a small quantity of current whilst the panel provides the bulk? If the latter is the case, how does this work?

Thanks for any assistance,
Branyon


texts:
RCD-Testers can be used to check if the residual current device (RCD) of the installation is properly working. How to they do this?

I want to build my own RCD-tester. Which circuit can be used to generate a certain fault current? (e.g. 30mA AC or 30mA DC)?


texts: Using a Cap as V_th in Thevenin Equivalent Circuit With Natural Response

texts:
My instructor solved this problem by creating a thevenin equivalent circuit to the right of the capacitor. But what I find odd is how at the end of it, there does not appear to be a thevenin voltage source. Or at least, the capacitor has taken the place of V_thevenin. The cap's initial voltage is of course 4V, but she seems to have used a method that would allow V_th to come out to 0 on the right side..

When I made my own thevenin circuit the usual way, I got the same R_thevenin = 70Ohms. But then I ended up with a V_thevenin = 14V.

Is anyone familiar with my instructor's method? I will of course ask her and update here but I am not currently at the university.


texts: Monitoring USB Keyboard Input with Microcontroller

texts:
I am currently working on a project in which I would like to be able intercept a specific key combination from a standard USB HID keyboard with a microcontroller. The purpose is to use the keyboard to control a peripheral while also being able to use the keyboard as input to a computer.

My thinking is that the peripheral will have a USB input for an HID keyboard, and a USB output, to send the keystrokes to the computer from the peripheral. I am fairly certain that it is not possible to have one keyboard be used with two devices simultaneously, so my thought is that the peripheral will have to intercept all keyboard input, and check for the key combination. Then, it would have to be able to be recognized as an HID by the computer, and send the input to the computer as an HID.

Is this correct? If so, is this feasible to do with a microcontroller like an XMEGA?


texts: Easiest Wifi module/shield to interface with Arduino Fio?

texts:
This is my first time doing any arduino build, and I'm planning to build a digital hydrometer/thermometer for home brewing. I'd like to either run a simple webserver on the arduino or transmit the information to a small server that I'll be setting up. In order for it to fit into my fermentation vessels, the device needs to be less than 2 inches in diameter, although length is not too constraining. This limits me to the Arduino Nano or Fio and smaller modules. I'm thinking of going with the Fio, since the 3.3v output on the Nano isn't powered when running from external power. For Wifi on the Fio, I'm looking at either the XBee Wifi module or the WiFly GSX breakout board. Are there any advantages to one versus the other?

On a more general note, is the Fio a good choice for this project? I'll need to be pulling information from a temperature sensor (I haven't begun researching this yet, so any recommendation of favorite sensors/methods would be welcome) and this liquid level sensor. The project will also need to be battery powered.

tl;dr - XBee Wifi module or WiFly GSX board for interfacing with the Fio?


texts: How do I find transconductance gm in this exercise?

texts:
We have the following exercise :

I have questions regarding a) and b)

For a) the solution is

As for b) you can kinda see it in the above solution that IE=0.5 mA ,I think that this is because IE=I/2 =1/2 =0.5 mA  .In the solution it is also written gm=0.5/25 where 25 is Vt. I dont understand why is gm=IE/Vt in this case when gm is always gm=IC/Vt?


texts: Can I disable a battery powered device by reversing half of its batteries?

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When I have a device that is powered by two batteries, can I disable it by turning one battery around?

For illustration, the purpose is to leave batteries in the device for storage, but it does not have an off switch. There are multiple solutions for this,  but I would like to understand specifically the solution using reversed batteries.

My idea is as follows: By turning around one of two 1.5 V cells, I let the + poles touch in the middle. The voltage between the - poles should now be 1.5 V - 1.5 V = 0 V. Therefore, there is no current through the device.

The problem is: Two batteries may not be perfectly balanced. One of them may be more discharged than the other, so they have different voltages.

It could work if the battery with more charge would be automatically discharged until it reaches the same level. Then, the cells would get into perfect balance, and stay that way even with fluctuations.

Does that make sense? What properties of the device are required?

If it works with two batteries, does it work too with other even numbers of battery cells?


texts: Art of Electronics 2.5 - Transistor saturation

texts:
With reference to the image below the text says

When the switch is closed, the base rises to 0.6 V (base– emitter diode is in forward conduction). The drop across the base resistor is 9.4 V, so the base current is 9.4 mA. Blind application of Rule 4 gives IC = 940 mA (for a typi- cal beta of 100). That is wrong. Why? Because rule 4 holds only if Rule 1 is obeyed: at a collector current of 100 mA the lamp has 10 V across it. To get a higher current you would have to pull the collector below ground. A transistor can’t do this, and the result is what’s called saturation – the collector goes as close to ground as it can (typical sat- uration voltages are about 0.05–0.2 V, see Chapter 2x.) and stays there. In this case, the lamp goes on, with its rated 10 V across it.

Rule 1 is: The collector must be more positive than the emitter.

I’m missing a step - how would a negative collector voltage obey this rule and result in a higher current?


texts: How can I deal with interference from a test RF signal (XM radio) in order to get a live RF signal of the same type?

texts:
I'm located at a manufacturing plant where they have a test XM radio signal. I have a software engineering department located at the same plant that needs to work with a live XM signal.

The plant's test signal covers the whole block, so escaping from it would prove difficult. While discussing with some colleagues, building an open Faraday cage came up as a plausible theory for a solution.

Truth be told, I'm no EE, so I'm flying blind, but something tells me there should be a way to get a live XM signal from my position without having to use ultra-expensive equipment.

Is there a technique or principle that could let me get my live XM signal from my location?