texts: Wiring different DC voltages to use 120V AC

texts:
I apologize in advance if this is simple. I've only had an intro to circuits class and all we did was analyze existing circuits, and even that's been a while.

For a design project I'm trying to wire together (theoretically, not in practice) 4 thermoelectric plates (15.4V DC and 1.7 ohms each), 2 computer fans (12V DC and 0.15A each), and 2 door lock motors (12V DC and 2.6A each). To clarify, I don't actually have to do this. I just have to prove that it's possible and show the set-up to make it possible. Ideally, I'd like to wire it all up with a/some AC to DC converters so that everything can run off of a 120V AC wall outlet.

I've done some initial analysis and found the following requirements for a few set-ups:

2x motors in parallel: 12V/5.2A
2x motors in series: 24V/2.6A

2x fans in parallel: 12V/0.3A
2x fans in series: 24V/0.15A

4x Thermoelectric plates in series: 61.608V/9.06A
4x Thermoelectric plates in parallel: 15.4V/36A
2x Thermoelectric plates in parallel then series: 30.8V/18.12A
2x Thermoelectric plates in series then parallel: 30.8V/18.12A

What's got me confused is how to wire everything together since they have different voltages, amperages, or both. I apologize if this is simple, but as a mechanical engineering major, I have almost zero experience or knowledge about anything more than simple circuit analysis.

Any assistance that can be provided would be greatly appreciated.


texts: Amplification circuit for a limited range of output signals

texts:
I have a sensor that puts out a signal between 0 and 25mV. Of that range, I am only interested in the 16mV to 22mV portion. The output should primarily be a DC signal, and the AC response, if any, will most likely be noise. The output of the sensor is fed into a 5V ADC on an Arduino Uno.

It would be rather simple to just pass the signal through an op amp with a gain of 200. However, the resolution of the output would be reduced compared to conditioning the signal such that only the 16mV - 22mV is read by my ADC. I've played with passing the signal through an instrumentation amplifier to boost the 22mV to ~12VDC. Then passing that through a differential amplifier to reduce the maximum signal to 5VDC to be read by the ADC. The minimum signal received was down to about 9mV.

This circuit did not work correctly. I believe it was due to an impedance mis-match. I'm thinking I need a high-impedance differential amplifier to make this work correctly.

I toyed with the idea of using two instrumentation amplifiers (INA114AP), but the math just doesn't work out.

Does anyone have any ideas on how I can accomplish this? I'm sort of out of ideas.

Oh, and this circuit will be used for brewing beer, if that motivates anyone to reply :)


texts: What resistors and capacitors will I need?

texts:
I have 4 LEDs that are rated for 3v-3.2v 20mA. Each LED will be wired in Parallel to a 5v power supply.
When power is applied to the circuit, I would like each LED to turn on with a delay.
The first LED with a 0.1 second delay, the second with 0.2 second delay, the third with 0.3 second delay, and the 4th with 0.4 second delay.
What capacitors, and resistors, will I need to make this possible?
LED gradually lighting up over time is fine.


texts:
Suppose I was given:
$$g(w,x,y,z)=(x+ y ̅+ z ̅  )( w+ y ̅+ z ̅  )( w+ x ̅+ y ̅  )$$
Then I can write it like this:
\begin{align}
g(w,x,y,z)&=(ww ̅+x+ y ̅+ z ̅  )( w+ xx ̅+y ̅+ z ̅  )( w+ x ̅+ y ̅ + zz ̅ )\\
&=(ww ̅+x+ y ̅+ z ̅  )( w+ xx ̅+y ̅+ z ̅  )( w+ x ̅+ y ̅ + zz ̅ )\\
&=(w+x+ y ̅+ z ̅  )\\
&\phantom{=\ }(w ̅+x+ y ̅+ z ̅  )\\
&\phantom{=\ }( w+ x+y ̅+ z ̅  )\\
&\phantom{=\ }( w+ x ̅+y ̅+ z ̅  )\\
&\phantom{=\ }( w+ x ̅+ y ̅ + z )\\
&\phantom{=\ }( w+ x ̅+ y ̅ + z ̅ )
\end{align}
From here how can I write the result using sigma?
It should be:
$$g(w,x,y,z)= ∏ (3,6,7,11)= ∑(0,1,2,4,5,8,9,10,12,13,14,15)$$
But I don't see how we concluded that.


texts: Am I correct? Or does D= V1-20, which allows the value of V1 to be positive?


texts:
I have an electronic socket that I am using and it uses a HLS8L-DC6V-S-C Helishun relay with a minimum release voltage of 0.3 Volts & max operating voltage 4.5 V

Datasheet - http://www.helishun.com/secure/pdt/hls8-t73.pdf

The voltage being applied to this relay in the socket is around 2.4V and the relay is not switching. But I got another unit of the same relay and it worked. Is the first relay damaged or is it due to something else?

Also, what is minimum release voltage? In this case it is 0.3 V, so what is minimum voltage I should apply to the relay to make it switch?

Thanks for your help!


texts: The image below shows a extremely simplified circuit diagram. I do understand the logic behind that. However, the other image(below) is the one i dont understand. It shows a circuit diagram implementing the NAND gate. I do understant how the NAND gates works. However i dont understand the circuit on the left of the image. The truth table shows the correct output of a NAND gate, however, based on the circuit diagram on the left of the image, if A and B is 0 shouldnt the output for Y be 0 as well. I dont understand the symbol beside the Alphabets as well. I dont know how the current in the circuit diagram is flowing as well. Would anyone care to explain how this works? Thank you.


texts:
I need a clipper for a 10 kHz signal to protect an ADC from possible overvoltage. I'm using the usual active circuit (simulation is in multisim):

Unfortunately the result is very bad, the opamp is too slow to respond. I tried adding compensation capacitor C1 but no luck.

The problem is magnified if I give a square wave signal at the input. Then the output gets all the way to Vdd. I also attempted to give the bias voltage as a Vdd source for the opamp but then the diode drop gets in the way messing up the signal. I've tried the circuit in reality and it works like in multisim.

Is there a way to remove the spikes, even in the square wave signal? If possible without significant phase shift.

EDIT: I forgot to mention that the input stage is actually an in-amp,the AD8226 with a slew rate of 0.6V/us.
Also,the C3 cap is there because i have integrated the ADC input filter with the clipper. I suppose that this may slow down the response of the clipper,so i moved it's input to BEFORE R15. No luck again. Seems that LM358 is too slow. A fast opamp solves the problem,but i'm wondering if i can slow down the slew rate of the AD8226? Tried adding a 100pF from it's output to GND but did't help.


texts:
I am a newbie and trying to work out the way to a simple application I have to finish. What I want my Bluegiga WT12 module to do is, just enter to the SPP profile and wait for any initiators and get connected. Then start the data from UART to flow over Bluetooth to the other device. That should be very easy, but I could not find my way in the user guides.

What settings do I need to send via iWRAP commands for my goal?


texts: How should we interpret a electric rotor in short circuit of a induction machine?

texts: I have seen many problems that ask certain data as current or likewise, it ask for nominal conditions and then adds the condition of having the rotor in short circuit, then this would mean for numeric calculations that R'2 is equal to zero ohms? If not, then what does it mean the rotor is shorted?


texts: Pump control - Uni or Bi polar stepper motor

texts:
I am working on a robot that includes several annular gear pumps. We are using the MZR 2521,

manual: (please see section 5.5)
http://www.micropump.com/support_documents/manual_mzr-xx21.pdf

product page:
http://www.micropump.com/product_detail.aspx?ProductID=62

In the description they say that you can run the pump as if it were a stepper motor. This seems like it could be done perfectly with an Arduino, but I was not sure whether to treat it like a Unipolar or Bipolar stepper motor as the setup for each is quite different. Does anyone have any thoughts as to which it might be? Thanks so much.


texts: Replacing simple physical switch by an arduino controlled digital one

texts:
My electronics knowledge is extremely basic, but i have started playing around with Arduino Uno to which i send commands from a C# program. For a next project, i would like to extend my set up in order to use my computer to control a smoke machine similar to the one bellow:

It is a 400W fogger, powered by 220~250V at 50-60Hz. You basically turn it on, and then use the (plugged-in) remote in order to blow smoke (or not). Ideally, i would like to replace the physical switch on the remote and use an Arduino to communicate with the fogger and trigger the smoke blow. I found similar posts (e.g. Replacing a mechnical switch with a digital one), but they seem rather complicated compared to the set up i have at hand. I opened the remote and here is a Fritzing sketchup of its inside:

I saw some posts mentioning the use of relays in order to control the remote state (BLOW or NO BLOW), and i do have a small relay at hand that was shipped together with my arduino kit (1 Channel 5V Relay Module). To my understanding, you have to be careful when using relays since without proper knowledge you can damage your hardware or even harm yourself pretty badly.

I guess i am looking for a few tips or hints from other people (since i am quite a beginner and have nobody around me i can ask for advice) on whether or not using a relay would indeed be a good option. Any other comment or information is of course more than welcomed.

Thanks in advance


texts:
I just started learning about transistors, so I was wondering if I could build a circuit where short circuiting across the load caused a transistor to cut off power (like a fuse).

My idea was that when the resistance across the load diminished (short circuit), the current flowing through the reference resistor would diminish thus turning off the transistor controlling the circuit.

Diagram/Schematic

Forgive me if this question seems to simple, but I searched the forum and can't find anything. I tested this circuit and it does seem to limit the current so I'm wondering why not use this instead of a fuse that gets destroyed by the current?


texts: 555-timer circuit supposed to give 50% duty cycle square wave doesn't

texts:
I wanted to build a circuit that gives 50%-duty-cycle square wave. I built the circuit of figure 4.4.6 from this link which is shown below:

I used the NE555 chip, and used a potentiometer instead of the resistor. The resulting waveform is shown below:

You can see that it's not a 50%-duty-cycle as expected.

What is the reason of that? Charging and discharging are done using the same resistor and capacitor, so on-time and off-time should be equal.


texts:
I’ve been working on a project making a lab bench power supply. I designed the schematic, the layout, got the PCB made by OSH Park and ordered all of the components separately from digikey and have been assembling the components by hand.

The general block diagram goes AC to DC converter using a full bridge rectifier with an isolating transformer, which goes into a shunt FET, leading into a synchronous buck converter (a TI IC), which goes into a high current LDO, which finishes at the output. The shunt FET is driven by an op amp and acts as the current limiter. This whole setup is meant as a max 25V and max 5A adjustable power supply, where the buck-LDO relieves the need of a big heat sink but gives relatively noise free power. Most of the PCB uses SMD components.

When I was putting components down for my AC to DC converter, I noticed some arcing that occurred on the undersides of some of the capacitors. The arcing was shorting the power rail and was clearly visible and could be smelt. Desoldering the capacitor and cleaning the ash residue that was left would fix the problem. The voltage on that line was a max of 35V depending on the load, and I though these components were big enough to not cause an arc (package sizes ranging from 0402 to 1210).

I initially thought this might be because my soldering iron was too high of temperature and when soldering the components with flux, there would be some solder splashed around the components and that could cause a short. However I reduced the temperature and have been cleaning my board religiously and the same problem persists as I’ve been finishing the buck converter.

Another note is I literally saw a black line spreading between ground and the power rail when I was debugging the arcing problem for the AC to DC converter. It would take around 5-10 seconds for the line to connect ground and power and when it did it would start arcing. The black line looked like spreading lightning.

Any ideas on how to avoid this?

EDIT: Here are is the schematic of the AC to DC and buck converter respectively:

The arcing also occurred when I plugged the thing in, not while soldering. This has only happened on the power-GND caps so far.


texts:
I have a routine for SHA-1 on a few bytes of input that takes 17ms to complete on a 8051-based core (running at 32Mhz). It calls memcpy once but it seems to be the bottleneck (taking almost the whole of the 17ms!).

Does anyone know if there's a way to improve the performance of memcpy?
Thanks


texts: How do I go about solving this and finding the value of v(t)?

texts:
I'm very sorry if the solution turns out to be very basic, but I'm a very recent student and my teacher is less than happy to help.

edit: sorry for not posting my attempted solutions first.

Here is my try, I'm mostly not confident in how to approach v(t) since it is in series with the first 1 ohm resistor, and whether or not I could just find the voltage across the (1 ohm + 1 H) to find v(t), since they're in parallel with each other.


texts: Why we take arbitrary current directions for same circuit

texts:
Can anyone tell me why V2 and V3 are negative. I mean while writing KVL equation if we take current to be flowing in clockwise direction then why

    V2=+2x5

If current flows in clockwise direction(as in KVL equations) then we should write V2=-2x5 according to PSC.


texts: Control many RGBs by color group using transistors instead of using LED Driver ICs

texts:
I have 12 RGB LEDs that I need to control as per the following parameters:
-The bulb is on or off
-Brightness control of each color group (meaning I don't need control over each color of each bulb)

I know this is not very difficult to do using LED Driver chips such as the TLC5940 or TLC5971, but I thought of an alternate approach in order to save on cost and hardware.

As shown in the schematic below, I have 3 PWMs (one for each color), that would allow for brightness control of each color group. There are also 12 digital signals (S1...S12) that can switch an RGB LED bulb on/off (note how S1 goes to RED_1, GREEN_1, and BLUE_1).

So all the MOSFETS are essentially used as switches, and the brightness can effectively be adjusted by an "analog" or variable source.

Would this reduce the hardware required (cost) and make the programming simpler? Are there any limitations or design considerations I should be aware of?


texts:
I have the following code in my microcontroler program:

// Wait for ADC conversion to complete
while ( ( ADCSRA && _BS( ADSC ) ) == _BS( ADSC ) ) {}

Where ADCSRA is a register that will change its value once an analog conversion is completed and where I want to wait for a bit to be clear. This bit indicates conversion completed.

Looking at the resulting assembly code, the whole loop is replace by a single instruction:

in      r24, 0x06       ; ADCSRA

The register is read, but its value isn't even tested!?

How do I have to change my C++ code to instruct the compiler to keep rechecking the register, without unnecessary delaying the program?

I use the avr-gcc toolchain.

EDIT:
I changed the code as follows (Thnx: lhballoti):

while ( ( ADCSRA & _BS( ADSC ) ) == _BS( ADSC ) ) {}

Which changed the assembly code to:

38:   36 99           sbic    0x06, 6         ; 6
3a:   fe cf           rjmp    .-4             ; 0x38 <__CCP__+0x4>

Which apperently solves the problem.

Check this page for the complete program and its disassembled resulting code.


texts: What was the protocol for programming GAL devices?

texts:
What actually has to happen, at a pins and signals level, to program a GAL device? Let's say I have a GAL 22V10, and a .JED file with the desired fuse pattern. The usual way to proceed is to drop the chip into a commercial programmer, load the .JED file, and tell it to go. But what goes on to configure the chip? How are those 'fuses' specified? How are they read back, written, erased?

After some effort with search engines, I don't have anything more concrete than 'PALs are programmed similar to PROMs' to go on. The implication seems to be that if you have a PROM programmer, it doesn't take too much to program a PAL or GAL. Does this mean that with programming voltage applied, you can address the fuses like a memory? Of course GALs are erasable and PROMs were not, so this analogy says nothing about how you'd go about erasing one.

In particular, the project at http://elm-chan.org/works/pgal/report_e.html makes it evident that the hardware is very simple; the only interesting bit being the software to control it. Unfortunately (for me) the commentary in the accompanying software is in Japanese, and the code itself is in 1980's style macro assembler for DOS, so teasing out the protocol looks daunting, as the code to read the .jed file (using DOS-isms) is all mixed up with the programmer I/O. (Not to mention he has his own protocol layered on top, to shift all the parallel bits through those 595s)

And yes, I know the 22v10 is a dinosaur. Let's say I just want to know.


texts: Using triacs to switch more complex equipment than just motors and lights?

texts:
Obviously triacs have been well known to be used in applications which don't really require a perfect sine wave to function.

However, what about say a triac to switch on and off more complicated devices such as phone/laptop chargers, TVs, audio equipment, pretty much everything else that you would find in the average household. I'm guessing it might depend on the front end of the power supply for the equipment, on its tolerance of its input voltage. However, does anyone have any practical experience with this?

What sort of waveform would you see if we switch a triac on, vs a mechanical relay switch? (i.e. triac switched on permanently)

To clarify, I mean a persistent on/off, in the way that a mechanical relay would be used to switch equipment on and off using an electrical signal. Probably a switch on the live line of the mains?


texts: LTSpice simulation of rectifier slows down after short time

texts:
I have the following simple circuit set up in LTspice:

Blue is on the output of the transformer and green from the rectifier.

If I don't include a capacitor this works fine and the simulation goes quickly. If I include the capacitor however the simulation becomes incredibly slow after a few milliseconds. The image shows up until it basically stops simulating at reasonable speed. The time at which it becomes slow seems to depend on the value of the capacitor

What is going on here?

NOTE: Solved by selecting 'alternate' solver in SPICE settings


texts: How to ensure no quiescent current through signal source in a common source amplifier

texts:
Generally,coupling capacitors are used to block the quiescent current in an amplifier from flowing into the source and load. But one of my homework questions required me to ensure that the quiescent current does not flow through the source and load without making use of any capacitors. Basically we had to find a condition on resistors and power supply so that no current flows through the source:

simulate this circuit – Schematic created using CircuitLab

Node 1 is at some VDD and Node2 is at some VSS where both are unknown. If no current were to flow through the source, it means VGS has to equal the voltage obtained from voltage divider principle. When I tried applying this condition to other conditions in the question, I was not getting enough number of conditions to find all values. Are there any additional constraints that I can impose to ensure that the quiescent current does not flow through source and load?


texts: What can be the reason that oscilloscope is showing voltages 10 times more than expected?

texts: I both check via voltmeters and osc. but oscilloscope is showing the values 10 times bigger. For example 5V pulse should be 2.5 mean and voltmeters shows exactly the same but osc. shows 25 V. What can be the reason?


texts:
I want to make a device for medical purposes.

I have a bit of experience with op-amp.

I tried many schemes and this gave better results:

I need a PWM on the frequency of 100kHz currents within ± 0.05mA ~ 2mA with the ability to adjust it using a DAC.

Electrodes are connected to the ear of the patient, I tried to create a skin model of L3, C5, R19.

I get this kind of current diagram:

For me it's very important for the pulses to be rectangular and without emissions, how can I achieve it?

Any of your tips on choosing a scheme and components.


texts: Nodal Analysis - Deriving equations at each node

texts:
I've recently come across a question where I need to solve using Nodal Analysis:

I'm a bit confused about the part where the arrow V1 points in the opposite direction to the voltage source. I've worked on the question and this is what I've come with so far (all in polar form):

I1 = I2 + I3

I4 = I3 + I5

I1 = (10/_0 - V1) ⁄2

I2 = (10/_30 - V1) ⁄j5

I3 = (V1 - V2) ⁄(4 + j4)

I4 = (V2) ⁄(6 - j8)

I5 = (5/_0 - V2) ⁄(5)

And my nodal equations look like this:

At node 1 (Polar Form):

$$ \sqrt{3}*90^\circ = V_1(\frac{3\sqrt{10}}{40}*18.43495^\circ) - V_2(\frac{\sqrt{2}}{8}*-45^\circ)$$

At node 2 (Polar Form):

$$ 1*0^\circ = -V_1(\frac{\sqrt{2}}{8}*-45^\circ) + V_2(0.3867*-6.6666599^\circ)$$

Would this be correct? And does the direction of arrow V1 have any significance?


texts: Chip inductors without voltage rating - how to interpret?

texts:
During the search for a suitable chip inductor I noticed, that many producers don't mention a voltage rating in the datasheet.
How to understand that? Does it mean, as long as I don't exceed the rated current, the voltage doesn't matter?
Or is there some underlying general definition of voltage rating?
Some examples:
https://product.tdk.com/info/en/documents/catalog/inductor_commercial_decoupling_nlcv32-pf_en.pdf
https://www.digikey.com/en/datasheets/taiyo-yuden/taiyo-yuden-wound01_e


texts: How to play a sound in a talking dog toy

texts:
So, my dog has a 'babble ball', which is a toy ball that plays random sounds when she rolls it around. She loves it, but the sounds are cringe-worthy. I would like to essentially remake this, but playing sounds of my own choosing (in this case, sound snippets from Austin Powers films).

Because it all has to fit in a small plastic ball, space is at a premium, so please bear that in mind - for instance, I -cannot- use a shield. Also, the sound quality doesn't have to be exceptional, given the application.

Currently, I'm planning to use a shake switch to detect when the ball is in motion, and ideally use an arduino chip as the brains. The part I'm struggling with is storing, and playing the audio.

The default Internet suggested option seems to be using pwm to play sound off a microsd card.

I do not want to use a playback chip, as I'm trying to use this as an excuse to learn how to do this.

What I would like to ask, is;

A. Could I store the relevant sound bytes on the arduino itself? Either in the sketch, or some sort of on-board memory? Putting a microsd card in for a couple of seconds max of audio seems overkill.

B. If so, how would one go about doing this?

C. Out of curiosity, how would one play a sound file without the use of a microcontroller? I appreciate it would probably always be easier to use one, but I'm interested if there is some sort of dedicated IC for this purpose.


texts: How to simulate temperature of interconnect and VIAs in designed IC?

texts:
How to simulate temperature of interconnect and VIAs in everywhere and any operation conditions of designed IC?
(design in Cadence by TSMC 0.18RF PDK)
Is it possible by Cadence or ADS?


texts: Calculate gain of degenerated common-source stage using small-signal model

texts:
I have difficulties calculating the gain of a degenerated common-source stage, with the output resistance of the MOSFET taken into account. I came up with the SS-model below. I calculated the following:

The gain is defined as \$ A = \frac{v_{out}}{v_{in}} \$, whereas \$ v_{in} = v_1 + v_s \$. I started writing an expression for the current.

\$ i = g_m v_1 + \frac{v_{out} - v_s}{r_{ds}}\$

Next I used that expression to solve for \$ v_{out} \$.

\$ v_{out} = g_m v_1 R_d+ \frac{R_d}{r_{ds}} v_{out} - \frac{R_d}{r_{ds}} v_{s} \$
\$ v_{out} = (g_m v_1 R_d - \frac{R_d}{r_{ds}} v_{s})/(1 - \frac{R_d}{r_{ds}}) = (g_m v_1 R_d - \frac{R_d}{r_{ds}} v_{in} + \frac{R_d}{r_{ds}} v_{1})/(1 - \frac{R_d}{r_{ds}})\$

And for the gain:
\$ v_{out}/v_{in} = (g_m v_1 R_d - \frac{R_d}{r_{ds}} v_{in} + \frac{R_d}{r_{ds}} v_{1})/((1 - \frac{R_d}{r_{ds}})(v_1 + v_s))\$

But now I have again \$ v_s \$ in the denominator, which I cannot substitute for anything useful. I feel like running in circles. Can someone help me out? What am I doing/approaching wrong?

simulate this circuit – Schematic created using CircuitLab


texts: Open circuit showing 1-15MΩ of resistance on multimeter

texts:
I'm trying to understand a phenomenon I observed while troubleshooting a system.
There are airflow sensors with wires connected to common and normally open so that the circuit closes when air is flowing. The sensors appear to be working as expected, however, when the circuit is open, my multimeter shows fluctuating resistance of about 1-15MΩ at the end of the wires connected to the sensors and ~50ft in length. I've checked the wires by disconnecting from the sensor and checking continuity. I've checked the sensor directly and am getting an open loop as expected. I'm getting the same results with two multimeters.

Any ideas of what I could check or any explanations of what may be happening would be appreciated.


texts: How to retrofit a barrel (coaxial) power connector to make it locking?

texts:
Perhaps this is a bit more of a mechanical question then electronic, I hope it is not off topic. We have all seen the many electronics that use a barrel style DC power connector (I guess sometimes called Coaxial).  I am wondering if there is a device that can retrofit this connector to make it a locking connector or to better lock it in place.

Specifically, I am hoping to find something other than locking down the cable itself, such as via a plastic loop affixed to the back of the chassis.  That works ok but for my purposes I was hoping more for something that would literally lock the barrel connector into its socket.  And again, I am hoping to retrofit existing devices, rather than cut cables / drill new holes.

Perhaps something that increases the friction already holding the barrel in place, such as some sort of small wedge or ring?  Does such a thing exist?


texts:
A piece of lab equipment (an image intensifier) is controlled by voltage in the range of 0..5V (current is expected to be in the range of 10 mA; desired resolution is around 12 bits; no frequency requirements since we won't be changing the voltage much). The internal voltage of the intensifier is set to 500V + (850V - 500V) / 5V * Vc. I would like to make it a part of a larger apparatus, all controlled by a PC. Therefore, I need the PC to control a DAC.

What would be a simple way to do that? Should I look for a microcontroller with a real DAC (not PWM) in 5V range? (Those I found seem to be limited to 3.3V - perhaps I didn't look in the right places?) Should I buy a simpler microcontroller and a separate DAC controlled by I2C? Use a 3.3V DAC with an operational amplifier?

It is not a problem for me to write a PC or uC program, but I don't have any successful circuit building experience, so I would like to optimize for less building complexity.


texts: drive a relay from a 3.3v 2mA max output

texts: I need to drive a relay, but my logic signal is limited to 3.3v with a maximum of only 2 mA.  Can I use a level shifter?  I have a 5V relay with a 125 ohm coil drawing approximately 40 mA.  Any other recommendations?  Should surge suppression diodes be used?  (Using National Instruments VirtualBench digital I/O)


texts: Transferring Circuit to Solderable Mini Breadboard

texts: I have a simple wifi temp/humidity sensor I've set up on an adafruit breadboard, and I'd like to transfer to a perma-proto type board, but the solderable boards I have are a slightly different layout than the adafruit board. There do not appear to be any power rails on the edges so I'm not sure how I may need to rework the circuit for it to function. I'm very much a tinkerer/new to circuits like this so I'm trying to avoid connecting anything in a way that might damage my ESP8266.


texts:
Why are flip-flops (bistable memory devices) called flip-flops?

The Wikipedia entry for flip-flop says that the terms "trigger circuits" and "multivibrators" were used in the past but not the justification for the term "flip-flop".


texts:
The drywall is just starting to go up in my family’s basement project. I’ve been looking into residential light control systems. Some of the ones I’ve seen have been an upwards of $2,000. I’m thinking it'd be much more fun (and cost effective!) to implement my own Arduino-based system.

The real problem lies in the actual control of the lights. Each group of lights will need to be controlled by a switch-based dimmer system. It would be much simpler if the microcontroller was the only point of control. Alas, this is not the case. I’m assuming I need to use a dimmer switch that lets an outside device interface with it. That would avoid the problem completely as the switch and Arduino could both control the lights the Arduino would control the lights through the dimmer switch.

Can anybody recommend a better solution/approach or suggest a dimmer switch that has some kind of “remote” interface?

Update 3/1/2013: I eventually went with an Insteon-based solution using a custom shield from Good Robot. It works great and can be used to control anything Insteon, not just lights. I'll post an answer here when I get a chance to write up something useful.


texts: Prevent stepper-motor heating in constant torque situation

texts: I am using multiple stepper motors in an application where each motor is always resisting some torque, i.e. if I turn off the power to a motor, the applied torque will cause it to rotate and lose its position which I do not want. Therefore, the motors are being run at full power for the duration of the tests (which includes periods of rotation as well as stationary periods). Constantly applying full power causes the motors to heat up rapidly. What techniques are available for using stepper motors under constant torque conditions while minimizing heat production? I am using a Quadstepper board (https://www.sparkfun.com/products/10507) to drive four motors.


texts:
module stimulus;
  wire [3:0] max,med,min;
  reg [3:0] a,b,c;
  reg cin;
  sorting_three three(max,med,min,a,b,c,cin);

  initial begin
    a=4'b0010;
    b=4'b1001;
    c=4'b1010;
    cin=1'b0;
  end
endmodule

The above code giving correct result after Simulation. When I try to view RTL schematic. Its is giving error like:

ERROR:Xst - "stimulus.v" line 22: Module  has no port.
-->

Total memory usage is 123976 kilobytes

Number of errors   :    1 (   0 filtered)
Number of warnings :    0 (   0 filtered)
Number of infos    :    0 (   0 filtered)

Process "Synthesis" failed

How to define port of stimulus( it is test bench)? I think wire and reg is sufficient to define input and output port. If it is not then what correction required to get correct RTL schematic.


texts:
I have a sun battery which produces around 55V / 5A at most. I need to regulate this to 24V. I wanted to use the L7824 family, but they have a maximum DC input voltage of 40V so it would burn down.
I was looking for some eaiser solution for this but couldn't find anything.
Could you recommend a simple regulator circuit that would fit to this sun battery?


texts: Isolated voltage and current measurement

texts:
I'm designing a safety shutoff circuit that monitors several power supplies, both voltage (12V, 24V, 72V) and current (up to 8A). These are entirely independent supplies, so I'd rather not tie the grounds together.

Measuring current of an isolated supply is easy with a hall effect sensor, so this is mostly solved. How would I go about measuring the voltage though?

I'm aiming at a solution that will always provide accurate measurements, even if the voltage is not in spec, so ideally the measurement would not depend on the measured voltage at all. While I expect the majority of cases to be either "no power" or "power good", I think that it is possible for a power supply to be connected in reverse, for the wrong supply to be connected (there are three different voltages in the system), the load to introduce back EMF or similar , so the circuit should tolerate a bit of abuse and ideally still provide valid data.

The simplest approach appears to be another hall effect sensor in line with a medium-sized resistor, but I fear that the large current nearby would disturb the measurement (especially as the measurement current would be fairly small compared). I can place the second sensor at right angles and attempt to get some distance to the other sensor, but I'm somewhat space constrained (20x20mm per channel, and there is also a zener diode and optocoupler here for quick "power good" sensing).

The application here is a CNC mill, which uses different voltages for different stepper motors, so different axes may fail independently. One of the motors has an electromagnetic brake, which should be engaged quickly when the motor's power supply fails, while the motor should not be moved when the brake cannot be released, and coordinated motions should not be attempted when an axis cannot be moved.


texts: Illustrating op amp feedback without control theory

texts:
We are teaching op amps in a high school class, before calculus.  So we can't use control theory to teach how op amps respond.  All the same, I would like to have an intuitive explanation for how a feedback circuit works.  Take the negative feedback, for instance.  Is there a clear way to show how an initial difference of delta between V+ and V- leads to a very large (G(V+ - V-)) difference in the output, which then leads to ...  I'd like to be able to take that argument and show how the voltage of the output converges in addition to the standard virtual short argument.

Can anyone explain it clearly?


texts:
I've got a 555 timer being powered by a 5v rail that is isolated from the 3v rail running a motor driver, which runs a motor.

The 555 is only supposed to fire when it gets the signal from a 38khz infrared detector but it seems to trigger everytime I plug a wire into the 3v rail, or sometimes for no apparent reason at all.

What is going on? Can I give it some buffer room somehow?

Extra info: when the 555 is triggered by the 38khz infrared receiver, it is supposed to tell the driver to spin the motor forward for about 6 seconds. However, the 555 also triggers an infrared LED to try and trigger a photoresistor, and if the light isn't blocked, then the phototransistor is supposed to disable pin 2 of the driver and enable pin 7, thereby reversing the direction the motor will spin for the 6 seconds indicated by the 555. this is so that the device can tell whether to run the motor forward or backwards based on the phototransistor's ability to see light.

a busy cat http://jackvero.com/pictures/schematic.png


texts:
I know this question might sound obvious, but still I cannot find an answer.

What is the purpose and best-fit applications for field effect transistors?

I mean, we have bipolar junction NPN transistors. It can be used to control a high-current circuit with a low-current signal, for example enabling relay through a microcontroller pin output. The most important characteristics (please, no holywars on this statement) is working voltage, hfe and power dissipation. We may assume that a NPN transistor with hfe = 50 for fixed voltage and base-emitter current 10mA passes up to 500mA from collector to emitter. In general, we can say that collector-emitter current is determined by base-emitter current.

[Disclaimer: I am not sure about the following statements and making it clear is the purpose of posting this question]:
Ok, now let's take a look at FET transistors. Source-drain current is determined by gate-drain voltage:

The second chart (above letter б) is the dependency of source-drain current of gate-drain voltage. So,

While bipolar junction transistors' "useful" current amplification is determined by current between two pins, FET transistors' current amplification is determined by voltage between two pins;
FET transistor consumes much fewer energy because gate-drain resistance is very high;

Assuming this two statements are correct, I do not quite understand how do I want to use this transistors, and when should I prefer them to bipolar.

Thanks in advance.


texts:
I designed an induction generator in the Maxwell program for wind turbine, it worked.
I selected 4 poles for stator and rotor and 12 slots for both.
Is the number of Poles enough for 1500 rpm speed and number of slots?(for salient poles machine)
Could you draw on the figure and show where the poles are?(for example)


texts: How to reduce power in barebone setup of atmega328p?

texts:
For every 15 minutes once ultrasonic sensor data will be send to the receiver using nRF24L01. I'm using atmega328P with battery power using AAA*3 battery and it should operate at least 15 days. Can someone please suggest me how to reduce power consumption, except the time of reading data from sensor.
I referred number of blog, they using deep sleep mode, but I need to wake up it for every 15 minutes. I can't use watchdog timer since its has only 8 seconds. If I use external RTC for interrupt it added cost in product.
Thank you in advance :)


texts: Using Associativity to Reduce Number of OR Gates

texts:
EDIT: I think I'm probably more confused than I realise. My question could also be phrased as "how was the given diagram constructed from the expression, particularly with reference to the OR gates?"

Say I have the logic expression X = A AND ((B AND C) OR (B AND D) OR (C AND D))

It looks like I need 3 OR gates to handle the possible conditions for the second input to the AND gate.

However, if I add brackets to the expression, like so:

X = A AND (((B AND C) OR (B AND D)) OR (C AND D))

it looks like I can reduce the number of OR gates to just 2.

Is this correct? Is this a standard method of simplifying expressions using the associative property of Boolean algebra?


texts: What's the usage of this type of biasing?

texts:
I'm trying to know What's the usage of this type of biasing BJTs. this is the main schematic. I'm talking about these type of biasing:

Another question to me is this type of biasing for potentiometer:

If the desginer would use pot as a variable resistor(not voltage devider) he/she could use such biasing:

Am I right? then what's the point about this type of biasing?

Edit: Is there any difference between this type of biasing and in this question?


texts:
I am working on the hardware of a boost converter . I will just pose a question on my boost converter since I assume the same knowledge can be applied to my buck converter. Well this is my first converter design and also my first PCB layout design so any positive criticism will be appreciated. I have attached my layout below for everyone to see.
Well firstly is the layout good enough to reduce EMI?
For a maximum 7 A continuous current is 2 mm/78.7 mil enough?
For the system testing, let us say I want to test the inductor current or any other components current What measures can I add to my PCB to perform such test. Is maybe adding a header where the current will flow and then connecting the header with an appropriate size wire where you can place your current probe good practice? Or maybe breaking the track and adding a wire there instead? Any suggestions on this will be appreciated.
Is a single layer design sufficient? In the the case that I do not have a lot of components.
I have to also use voltage and current sensors for my system, how do I incorporate their design within this PCB if I want to have that on a different PCB?
I have added the schematic of the PCB below.


texts:
Suppose I have a feedforward neural network and I already have decided what its directed graph, weights and activation function should be. I want a device than runs this neural network as quickly as possible, with secondary considerations being size of the device, power consumption and cost. What is the best hardware design for this purpose? Have there been cases of say ASICs being built for a particular neural network?
To give a rough idea my network has around one million neurons and ten billion connections.


texts:
I'm looking at this line of solenoids, but I'm not sure how to figure out the electrical characteristics.

If the solenoid is rated at 12VDC, and 3W, does that mean I can strap it across a 12V supply, and the solenoid won't melt? As in the manufacturer built in a 48 Ohm series resistance to limit the current to 0.25A and I don't have to rely on something else in my circuit to limit the current?

Also, assuming I wire it like this:

How long does it take for these things to de-magnetize in general? Microseconds? Milliseconds? It should be determined by the inductance of the coil, but the inductance isn't specified in any kind of solenoid datasheet I can find.


texts: "Stopping" sound after a certain frequency

texts:
A friend has a condition that can cause seizures when listening to frequencies over 1500Hz. To help her out I made a passive first order (RC) low pass filter with a cut-off frequency at ~1300Hz but when testing this I noticed that frequencies of up to 13kHz were still audible.

Obviously what I tried isn't the solution, but with no proper electrical engineering training, I'm struggling with what I should be looking up online regarding keywords and names of circuits.

TL;DR I'm looking for a circuit that will completely cut out frequencies over around 1450Hz with 0 wiggle room for anything over that frequency. Preferably as a DIY solution, but I'm open to all suggestions.

Any circuit names or links that can point me in the right direction is greatly appreciated.

EDIT: Also, would stacking these passive low pass filters eventually achieve what I'm after?

Update (thanks transistor): The general use case is with headphones and listening to music or audio output from a TV etc. She wears noise cancelling headphones when out in public with no music only to dampen outside noise and helps little. This is just a side project to hopefully let her be able to plug into any device with headphones and know that she wont be harmed.

Update 2: Thank you everyone for your help, the general consensus that I received is that it is harder than a simple passive filter. I found this site which lets you specify requirements on a filter and suggests (with some tweaking) a "10th order Chebyshev 0.20 dB (5 stages)". So I'll see how I go. Thanks again for the input, I really appreciate it.


texts:
I am having a tough time here.I want to design a simple transistor switch (obviously operating in saturation) using 2N3904.I want to switch a current of 10mA.

The part in yellow rectangle indicates if assuming saturation I use a base current of 1mA,I can get 10mA at the output.Then there is the part in red rectangle  where i have to find base current by Ic/hFE(min) (I am not even sure why this formula is used here because I am assuming saturation).But here Vce=1V which I don't think is well into saturation.There is a deep loop hole in my understanding somewhere,I know that.


texts:
What is a good value for a pull-down resistor, which when switched, connects to 24v? Is there a formula to derive this?

This is effectively how it's drawn in the schematic (the inverter input's impedance is 650kohm):


texts: Differences between mini USB and micro USB in circuit design?

texts:
Hopefully a quick and silly question -

I am looking to modify a reference design such as this one:

http://www.microbuilder.eu/Files/Projects/LPC1343RefDesign/LPC1343_Schematic_v1.6.pdf

And was wondering if I could replace the Mini USB with a Micro USB without much hastle. What signals / connections would have to change?

Cheers


texts: Digital Signal Analysis: Sinusoid and Filtering problem

texts:
I was wondering if someone could help me derive the answers for (ii) and (iii)? These are exam review problems, not homework, and I have no idea how to solve them. I have been trying to reference my textbook/look for help online but it has been very difficult for me to find examples online similar to this one, so I figured I would give this a shot. The answer I got for (i) was .25 seconds (from getting the frequency of each sinusoid and then finding the greatest factor to get the fundamental). Any help is extremely appreciated!

Edit: I got these answers

$$b = \left[ \begin{array}{lllllllll}
1.7 & 0 & 0 & 3.5e^{-2.1j} & 0 & 0 & 7.9e^{0.8j} & 0 & 5.4e^{1.1j}
\end{array} \right]'$$

$$c = 512$$

But I am not sure why vector b has \$0\$'s in it, can someone explain?


texts:
What happens to the emitter electrons when a BJT is in saturation region?
Do electrons move from the emitter to the collector because of the base being saturated with electrons?
What are the conditions for this to arise?


texts: Calculating gain on Op Amp with AC voltage

texts: I am trying to understand how to calculate the gain when the input is AC voltage. I am familiar with ideal Op Amp calculations, figuring out the voltage will be the same at both input! terminals. But how does this change when the voltage is AC?!


texts: Are there any differences between SMD and THT inductors?

texts:
I wonder if there exist any differences in performance between chip-SMD (like 0805) inductors and THT inductors?
More specifically I need to solder 10 uH 0805 SMD inductor for my bias tee module (like this, sorry for Russian page). However I can't get it right now so I've decided to use this temporarily.
I know that typical max power dissipation is 0.1 W for 0805 form-factor and 0.25 W for small THT inductors/resistors. But I'm unaware if there any other pitfalls exist which could mess my things up. Can anyone give me a hint?


texts: In electromagnetic field theory, we talk about "magnetizing force". Units of magnetizing force is A/m (Amperes per meter). It's obvious that units of force is Newton. So, is amperes per meter equal to Newton?


texts: Add an LED to a low power line (heater thermostat switch)

texts:
I'm a beginner in circuit design and even if it applies to a real situation I'm doing this as an exercise.
After my thermostat broke some months ago I decided to replace it with an AC switch, which for my needs is fine since I really don't need automatic temperature control, manual control is ok.
Sometimes I've thought it would be nice adding an LED attached to it, and even if there's a low current in the switch it I think it's better to put the LED in a separate circuit.  I've imagined this homemade solution using a ferrite core.  I understand that the voltage/current on the secondary would be very weak but...  Might it work?
On the left the as-is circuit, and on the right my modification. A weak or flickering light would be an acceptable result, considering it has no external power source.  I'd prefer this to a battery-powered circuit.
Could it put some impedance load on the AC line or disturb it somehow?  Thanks in advance.


texts: Can a sealed lead acid battery charger work properly with a flooded / wet cell deep cycle battery

texts:
I know that charging sealed / AGM / gel cell lead acid batteries requires a special charger so they don’t get overcharged, overheated, boiled out, and destroyed.

Is it safe to use this special type of charger with a standard deep cycle flooded / wet cell marine or automotive battery?


texts: Pretty new to the EE game here, just playing around with Arduinos and such, so please excuse me if this sounds a bit amateurish. I have a 3.7V LiPo battery, and I was just wondering if I could just hook it up to 5V vcc to charge it. I also have a 3.3v regulator, would it be better to pass it through that first?


texts: Is this flux residue or the PCB is burnt?

texts:
I bought a new laptop, and when I was about to add an SSD, I saw this. The store tells me it's nothing, and if anything, just flux residue from production.

To me, it looks like overheating. That is; a bad connection or something is causing a lot of heat, and thus these brown and dark spots around, especially the leftmost pin, and a black area on the edge of the PCB.

What do you think? Doesn't it look like it is burnt?

ADDED:

Let me add an extreme close up for details:
http://amews.net/ExtremeCloseUp.png

What about the edge - seems like it has been damaged (not a sharp edge anymore) - does that matter?

What about the brown color on the connector itself ? I suppose that the connector would not be plugged in while soldering. How should flux end up there then?

http://amews.net/Edge2.jpg


texts:
I recently study LDO with PMOS pass element structures.
I think, Line Regulation and PSRR are the same function of $$ V_{out}/V_{in} $$
Input is PMOS's Source, and output is Drain, it indicates that functions are form of CG Amplifier with negative feedback.
So I could derive a transfer function with small signal Vin,
$$ V_{out}/V_{in} = \frac {(g_{m}+g_{ds})[r_{o}//(R_{f1}+R_{f2})//Z_{L}]}{(1+A_{LG})} $$
where $$ A_{LG} = g_{m}A_{AE}\beta\ Z_{out} $$ $$g_{ds} = 1/r_{o}$$
Here's my question, is it correct to understand that difference between Line Regulation and PSRR is just considering frequency domain?
I think both act same as CG amplifier configuration, and will have same transfer function.


texts:
I have worked through a question and I am unsure if my answer is correct. It is a series RL circuit with a switch that closes at t=0, supplied by a dc source, which I am trying to derive an expression for the current i, when the switch is closed.

Something like the circuit below:

My answer is: i(t) = V/R e^(t/T)

But does this not represent the discharging current as an exponentional decay rather than a growth? I can show all my workings out if it is not correct.

I thought the current when the switch is pressed should be represented by:

i(t) = V/R ( 1 - e^(t/T) )

EDIT

The image below shows the only way I know how to derive an equation for the instantaneous current in this circuit:

Thanks


texts:
Say I have a signal that \$y(t) = s(t) + n(t)\$ where \$s(t)\$ is the desired signal and \$n(t)\$ is the noise signal. I understand that if the mean value is \$0\$, the Signal-Noise-Ratio can be computed with the formula:

\$20log_{10}(\frac{\int s(t)^2 dt}{\int n(t)^2 dt})\$

If say, the mean value for \$s(t)\$ is \$\mu_s\$ and the mean value for \$n(t)\$ is \$\mu_n\$, would the formula for calculating the Signal-Noise-Ratio become:

\$20log_{10}(\frac{\int (s(t)-\mu_s)^2 dt}{\int (n(t)-\mu_n)^2 dt})\$


texts: Other than Voltage, Current and Power, what else can a Phasor describe?

texts:
I've always thought of just these 3 things that a Phasor can describe -- the magnitude and phase of the sine function of these 3, vertically centered at 0 and of the same frequency.

Are there more?


texts: Dealing with voltage spikes in BLDC motor drive

texts:
I drive a BLDC motor with an ESC. When using power from a LiPo battery everything works as expected. When I use a power supply, on rapid stops or slowdowns motor generates voltage spikes, which send my ESC to overvoltage protection.

How can I deal with it? Will a zener diode work with PSU, if it's voltage rating will be higher than PS voltage and power rating enough for heat dissipation?

May be there is another way to do it correctly?

Thanks.

Additional info:
With oscilloscope I am unable to catch spikes on power input, no spikes there. They only show up on motor phase lines. I see PWM signal. I can catch higher voltage than usual there when braking or slowing down.

I have 1300 uF capacitance on the ESC. I use T-Motor MN5212 and 18 inch propeller.

Wires from the PSU to ESC are 10 cm.

Tried without the prop, same result.


texts:
I cant figure out which pin is the number 1 on the potentiometer and variable resistors within this schematic.  I would guess that the circle with a slash through it is pin one but I'm not sure.  Any help would be appreciated.  Thanks in advance!!!  Schematic link below.

http://www.tonehome.de/app/download/10398205/Ibanez_AD100_schematic.pdf


texts:
Background:

I have a hobby of heliographing (sending messages using reflected sunlight), and have a working setup that requires a human to adjust a mirror to follow the sun, interrupt the beam of reflected sunlight to send, and most critically to detect flashes on the horizon to receive.

I am planning to automate the process. Tracking the sun, and interrupting the reflection are pretty straight forward and shouldn't require a processor, but I'm at a loss about detecting a reflection on the horizon.

My best guess so far is using a digital image and looking for bright spots, but that gets me into the realm of image processing and that sounds like a very big time sink.

Problem:
I need to detect a bright reflection far away. The input is a bright point source in a smallish visual area. The output can be any other signal the correlates to the input on tens of millisecond scales.

Does there exist a device or technique to get this done?


texts: Which way does power flow on USB type-c if CC1 and CC2 are not connected?

texts:
I got my hands on some USB type-c Male connectors, but when I tore one apart I saw that there is no pin on CC1 or CC2 and thus no pull-up or pull-down. After doing some research I'm not sure I know if this connector can draw power or source power.

What behavior is defined in this instance?


texts: Can I somehow control a PSU-powered fan using a 4-pin fan output on the motherboard?

texts:
I have a 12V 29.4W 3-wire Delta Electronics fan that I want to power using an EVGA 750 G3 PSU and control via one of the 4-pin fan terminals on an MSI MSI Z390-A PRO ATX LGA1151 motherboard.

Not considering the wattage of the fan, I originally plugged it into a (known working) fan terminal but it of course would not turn (and the BIOS correctly reported the RPM as 0).  Connecting it directly to the PSU is simple enough, but this would result in it turning at full speed at all times.

I am curious if there is a "DIY" way that I can supply the fan with power from the PSU and control how much actually reaches the fan using the output of the motherboard (using something like an optoisolator to keep the motherboard safe).

The motherboard is able to control 4-wire fans using PWM, and 3-wire fans using DC voltage level.

Is there a product or combination of parts that will do this?  I originally asked this on Super User, but it was deemed more appropriate here due to the involvement of DIY electronics.

Thanks in advance!

EDIT:
The 4-pin connectors on the motherboard are indeed keyed to force correct connection of 3-pin plugs.

The BIOS includes a Fan interface that allows you to plot desired RPM vs temperature.  Each fan output can individually be set to either PWM or DC voltage level control.  The motherboard auto-detects what is plugged in (4 or 3 wire) and selects the appropriate setting, but it can be changed manually if desired.

The fan was not purchased through DigiKey, and came terminated with a keyed 3-hole connector (F). It also shipped with a 2-wire (but 4-wide) molex connector (M), unterminated on the opposite end.


texts: How to Use an External ST-Link/V2 with the STM32F4 Discovery Board

texts:
I have a STM32F4 Discovery board and a ST-Link/V2 programmer.

I want to use my own ST-Link (not the embedded one) for programming and debugging the board.

How should I connect the external ST-Link to the board ?


texts: Constant current driver and undervoltage protection for lipos

texts:
I'm searching for a way to drive a couple LEDs with a single-cell LiPo battery, such that the LEDs will be cut off completely when the LiPo voltage drops below, say, 3.3V.
PCB space, component count and price are critical, as the project is low-volume DIY stuff.
Anything else but under-voltage protection is not required, the lipos will be charged when disconnected from the device, and the batteries are not assumed to have any built-in protection circuit.
The LiPo choice is fixed at one cell with low capacity (around 150-350mAh), LED forward voltages will vary, but range from 2.0V to perhaps 2.8V, and I will use multiple of those LEDs (of the same type) in parallel so the total current might get as high as 200mA.
I'm pretty sure there are several good options for this since it seems like a common problem, but I found multiple ways and am unsure what is the best way to do this.
I've researched simple under-voltage detection systems to cut off the LEDs once voltage drops below a threshold, plus a latch since the voltage might rise again after load drops, combined with a constant current driver afterwards. But I'm not sure about startup behaviour, I fear it might be triggered once the battery is connected, and the complexity is quite high. There are two general ways I found to do it.
First, a comparator with integrated latch and voltage reference, however I haven't found an IC that includes both, just references that they exist. My hope is to connect the output to the latch enable to lock the result.
Second, to detect undervoltage with just transistors, with a latch afterwards (either transistors or IC). Unfortunately that's a lot of components and I'm not sure that works as expected
However I also reserched using voltage regulators with adjustable voltage (like the LM137 series) for constant current drivers and found that I might be able to use the voltage drop to cut of the LEDs without a separate undervoltage detection circuit. This would be possible using a LDO with adjustable voltage (not sure if these exists so you can create constant current drivers like with the LM137 series), with a resistor to drop the LiPo voltage down so that the difference between the LED voltage and the desired cutoff voltage coincides with the voltage drop.
However, I haven't found a good choice of IC, since the LM137 voltage drop is too high to power LEDs with a 1S LiPo. Also I am unsure how strong the LiPo voltage difference is once the load is removed - will the voltage regulator start oscillating? I have found a few comments referring to this but I don't know if this is recommended.
What is the recommended way to do this, if there is one? Are any of the ways I mentioned not recommended?
I don't need certification or anything but I don't want people who rebuilt this to start a fire because the LED driver keeps draining the LiPo to a point where it gets dangerous. It should be obvious that the battery is drained, the LEDs off.
Any input is appreciated, thanks!


texts:
I need to have a system where the 74ls93 holds and does not change until they are cleared. Does anyone know of a relatively simple way to do this?
Edit: Nevermind all, figured out how to do it by introducing an AND gate after the clock.


texts:
I am driving a BTB16-600BW triac using a MOC3052 exactly as suggested in the MOC3052 datasheet:

The current into the power triac gate is limited using the highlighted resistor. My triac requires at least 50 mA.

The resistor gets fairly hot during actual operation and no surprise: \$I^2R\$ (RMS) with the 10k resistor I'm using is about 1.2W if my calculations are correct.

Is there a better way to limit the current here, especially one that doesn't involve generating much extra heat? I don't mind spending a few more pennies on a solution that requires less tweaking - in particular, I'd love to just grab a purpose-built DIP6/8 IC that requires only a single additional passive to set the current limit.

I've seen a few circuits using transistors, but I don't have any with a high enough voltage rating, and if I'm going to buy something I'd prefer to buy the most suitable part for the job.


texts: Identifying Moore machine from state diagram

texts:
i am just learning about state machines.
I wanted to ask, if in a moore machine the output depends only on the current state, how can i identify this from a state diagram?

$$\begin{array}{ccc|ccc}
S0&S1&i &S0&S1& o \\
\hline
0&0&0 &0&0&1 \\
0&1&0 &0&1&0 \\
1&0&0 &1&0&0 \\
\textbf{1}&\textbf{1}&\textbf{0} &\textbf{1}&\textbf{1}&\textbf{1} \\
0&0&1 &0&1&0 \\
0&1&1 &1&0&0 \\
1&0&1 &1&1&1 \\
\textbf{1}&\textbf{1}&\textbf{1} &\textbf{0}&\textbf{0}&\textbf{1} \\
\end{array}$$

Clearly changing the inputs from a 0 to a 1 affects the output....
Am i missing something?


texts: How do you store ICs used in hobby electronics?

texts: I've recently started working on a project and I need to find a way to store some ICs that I'm using. I have around five different ICs and someone said I could just put them all together in a small cylindrical tube I have (think a little box medicine pills come in). Wouldn't this damage the ICs? And/or are there better ways to store them?


texts:
Are there any considerations for the polarity of wires on a CCFL tube?

I am converting a monitor from 120vAC to 12vDC using a generic inverter (AVT4029; also have AVT4168 not pictured) and LCD driver board.  The CCFL tubes are encased in the assembled display (Samsung LTM230HT01) and I would like to avoid further disassembly for risk of damage.  The CCFL wiring harness is similar to the standard small CCFL connector found in laptops, except the connector has 4 pins on each harness (connector: YEON-HO 35001HS-04L), 2x harnesses on the display so 4 lamps.  Pairs are red/white and blue/gray.  I cut the connector in half so it fits into the generic inverter.  The wires are all of the same gauge.

Edited to add:  the spec sheet for the panel is here http://www.spectrah.com/product/lcd_panel/samsung_lcd_panel/Samsung-LTM230HT01.pdf


texts:
I am new in STM programming and I want to do a simple UART communication but I don't know where to start.Can somebody send a tutorial for stm8l or a full code would be better so I can examine it.

Thx.

Schematics :


texts:
How do you determine how many sensors a microcontroller can use?
My understanding is you can't use C# directly on any microcontroller but you can use C# and communicate over the USB and look for a specific port. Is this true?

In my case i've narrowed down to the three following microcontrollers:

Arduino
Netdurino
AVR

This is what I'm trying to do as a first project and of course, this might not be an easy project.

I want to be able to hook up a thermometer and when the degrees get +-3 of a base temperature open or close a prop window.  Also, I want to be able to store the thermometer information in a MySql Database.

So basically if the base temperature is 80, when the temperature is greater than 83 I want to push open the window.  And if its 77 I want to close the window.

Im not to interested in the exact mechanism that opens and closes the windows, just how to send the signals to open or close it.


texts: Power supply (LED driver) specs: "setup", "rise time" meaning?

texts:
What exactly is meant by the terms "setup" and "rise time" in these specs:

Does it only influence switching at the AC primary side?

I'll use this for a refrigerator light, so it will always be powered.


texts: How is it possible to pull up an op amp's output to its negative or positive rail when its input is floating?

texts:
If signal source is varying between zero and 5V; and if we buffer this signal with an opamp which works with +10V supply or */-10V dual supply, is it then possible to pull up the op amp's output to its around -10V negative or around 10V positive rail when its input is floating(when the signal is decoupled from the opamp's input)? Can you show a topology example?

The following behaviour I mean:

input ---> opamp buffer --> output

10mV ------> opamp buffer ------> 10mV

5V ------> opamp buffer ------> 5V

Floating ------> opamp buffer ------> -opamp's negative rail(-10V) or positive rail +10V (but not zero V)

Edit:

To be more specific the following opamp buffer does not go to positive or negative rail when its input is floating:

So in simulation output is no behaving how I need. how can we modify this to obtain -15V or +15V output (around one of the rail voltages) when the input is floating?

Edit for an answer:


texts: how C2 leads to negative feedback and C1 leads to positive feedback

texts:
C1 and C2 represent stray capacitances.

I was told that C2 leads to negative feedback and C1 leads to positive feedback (pg 371 of Learning the Art of Electronics) and therefore C2 is good while C1 is bad, if your goal is to minimize unwanted oscillations.

I understand that due to the Miller effect, the effective input impedance is much greater due to the amplification effect between the input and output terminals.  I wasn't able to find an intuitive explanation of what C1 and C2 are doing in terms of feedback.

simulate this circuit – Schematic created using CircuitLab


texts: Decoupling Capacitor (High Frequency Spike)

texts:
Wondering if anyone could help me rectify my understanding of decoupling capacitors and their role in suppressing high frequency voltage spikes (particularly increases in supply voltage).

Similar Question.

The answer provided above does not explain to me the inherit nature as to why a decoupling capacitor will suppress these surges.
From my understanding, a capacitor placed at an input pin should shunt excess current through the capacitor proportional to the rate of change of voltage.

If such a transient spike travels down the supply line, shouldn't the voltage seen by the decoupling capacitor and the input pin be identical? The decoupling capacitor serves to shunt current, but the voltage is effectively unchanged.
If the incoming transient spike is seen by the node at the capacitor, shouldn't this same voltage be seen by the input pin?

Forgive my confusion, any insight would be great. Thanks.


texts: Actual power consumtion of xbee series 2 in sleep/power down mode?

texts:
According to user manual and several other official documents from Digi, xbee in the power down/sleep mode can consume as low as 1uA. But somehow such a low power consumption seems simply unachievable on my hands.

The following is my setup:

the DIN,DOUT,CTS,SLEEP_RQ,RESET,RSSI pins are connected to MCU, VCC connected to 3.3V source in tandem with a 10ohm resistor (for current consumption measurement), GND pin connected to ground. All other pins are configured as output as suggested by the manual.

The actual consumption measures at 0.7mA when SLEEP_RQ pin is asserted. Occasionally it can be as high as several mA.

I seem to be not the only person who can beat down sleep current into the realm of uA. The following is a blog post:
http://www.socgadget.com/2011/07/low-power-xbee-module/

I am designing a battery powered sensor network. close to 1mA of power consumption in sleep mode is really a big burden on battery.

I'd like to gather some actual first hand experience. Also if anyone can give me some actual number of Z-wave power consumption in sleep mode would be great. Z-Wave also says in its manual that can be less than 1uA, but I'd like to know the actual number before invest several thousands into it.

Edit: Turning off UART TX line on MCU side seems not to make a difference.

Thanks in advance,


texts: what microphone can recording ultrasound (about 40khz)

texts: I want to record ultrasound then their processing signal on raspberry pi but I don't know type of microphone that can interface with raspberry to can measure ultrasound ( I using MA40s4s ultrasonic of Murata to generate waves). Please give me some how can recording ultrasound


texts: Hooking into Qi charger status LED to power something more

texts:
I have a Qi charging module and I want to light up a higher-power string of LEDs when my phone is charging through it.

The module has a blue status LED to show it's charging, which I think is where I would hook into. My question is, could I use a transistor or relay where the status LED is to switch on my string of lights. Or, should I use some sort of current monitoring on the coil instead of relying on the status LED?

I'm kinda new to hobby electronics so sorry if I've made some silly assumptions along the way.


texts: How does one read a FIFO outside Qsys system using Nios II?

texts: There is a FIFO block that has Avalon interface compatible with Qsys that can be used in Qsys systems. However, in my case there is an external block that generates data that is to be read by a Nios II. The external block has a FIFO interface, thus the signals are basically q, empty and rdreq. I could try to use a PIO block to connect to the external FIFO and write some simple drivers to aid in communication. However, is there a better way to do this? Is it possible to somehow communiate with this external FIFO as if it was in the Qsys block with Avalon MM or Avalon streaming interface?


texts:
I'm building a project using the SparkFun MicroView, which is essentially an ATMega328 + OLED display, and I'm trying to decide what size LiPo to use... I like the size/footprint of the 110mAh battery SparkFun offers. However, I don't know how many amps to expect the MicroView to use. My project will be a simple handheld game, so I would like the battery to last at least 3-4 hours before needing a charge.

Doing the calculations: 0.11Ah / 4h = .0275A = 27.5mA. Is it reasonable for something like the ATMega328 + OLED display to draw around 27mA or less? I also designed my buttons with pull-down resistors, since they are normally open and I don't want them to draw current (albeit minute) while open.


texts: Is there a practical difference between Open Drain and Open Collector outputs, or are the terms used interchangably? If they are indeed different, what are the contexts where each is advantageous? My hunch is that they are functionally equivalent, but Open Drain is implemented with FET technology while Open Collector is implemented with BJT technology.


texts:
I tried CAN communication using PIC18F25K80 and MCP2551. Using two
nodes, I could transmit data from one node to other. But, data was transmitted only when the receiver buffer was set to ignore all errors and both the nodes were configured in 'Normal mode'. And, then I configured the receiving node in the 'Listen only mode' and data was received even when the receive buffer was set to 'Receive all valid messages as per the EXIDEN bit in the RXFnSIDL register'.

But, as the TXERR and IRXIF bits were set in the transmitting node, TXREQ bits was not cleared and the message was continuously sent. What could be the reason that causes these errors?

(I have used the internal RC oscillator set at 64 MHz and the baud rate was set as 100 kbit/s.)


texts: Looking for a transistor to power a load with PWM from a Bluetooth module

texts:
My project is a heating load power with a PWM from a Bluetooth module (BLE113). I managed to do the PWM I want with this module and now I would like to connect the load.
The module give a PWM with 3.3V and 20mA or 4mA (I can choose pin with 20mA or 4mA) and the load is connected to a 3.7V battery, Rl=9O Ohm so the current needed is ~400mA.
The output current of the module isn't enough so my research made me think of a transistor to switch the power of the load. I think it's the best solution.
A good help from electronicsclubs.info give me some specs for the transistor :

if I use the 4mA output : I need a h_FE > 5*Ic/Ib_max = 5*0.4/0.004 = 500
I also need a load for the module output of Rb = 3.3*h_FE/(5*Ic) = 825 Ohm
if I use the 20mA output : I need a h_FE > 100
I also need a Rb = 165 Ohm

I'd like to know if I'm right for this, and which transistor could give me this specs. I looked in the web and I'm a little lost.

I also have some concerns about the transistor tension, because if it's too high, I won't have the 3.7V for the load.


texts: When reading the digital wave from a DAQ, should I be getting the same wave I'm generating to it?

texts:
I am using a DAQ device, which is said to be capable of 400kS/s maximum, and therefore 50kS/s per channel when using all 8 channels. This is listed in the manual of the 1608fs plus DAQ

So I connected a function generator, and I'm sending a square wave of 25kHz, following nyquist theorem, to all 8 channels.

I thought at 50Ks/s sample rate I'll see the square wave in the software, but even at 10kHz from function generator I am not seeing a square wave. I am seeing a square wave more and more as I lessen the frequency, but I'd expect a square wave at 25kHz and below if its capable of the sampling it specifies that it is, am I wrong to expect that? Is it not capable of what it says it can do?


texts:
I am trying to graph the equation VbackEMF = L di/dt

When SW1 is off and has been off since negative infinity, I realize that there is no current in the system.

Now I imagine SW1 being pressed. The switch can probably make a good connection in 0.1 seconds, and current in the circuit without the inductor is 1A.

So here is what I am stuck on. Back EMF = 1 Volt at the first instant.
Well, how does the current ever start moving through the loop if the first instant doesn't allow any current through?

simulate this circuit – Schematic created using CircuitLab


texts: Problems with maxing out DC power supply?

texts:
I have a small switching power supply rated for 1.5A @ 5V, and 1.8A @ 12V.  Input is 100-240V AC.

Suppose I put a load of exactly 1.5A on the PSU, all on the 5V rail, no load on 12V.  Will this cause any problems, and if so, how will I know?  If it works for a few days, does that mean it will work fine for years, or is there some kind of long-term failure in this situation?

In a brief test, I noted that the voltage drops to 4.92V under a 500mA load.


texts:
I have a flex circuit board with 5 LEDs mounted on it.

I have large copper areas attached to the LEDs for improved heat dissipation.

I read here that "With a hatched plane, the moisture can exit the flexible carrier material, whereas it is trapped under solid planes"

This is a different question because it involves LEDs that require solid copper areas for heat dissipation.

Since the copper areas are only on one side of the flex, should I still hatch the copper areas?

If hatching the areas is recommended, how can I calculate the required hatched area for heat dissipation?


texts: Can you get electricity from your mobile phone

texts:
Does someone know if its possible to get energy from your phone (android/ios)? I want to charge a capacitor or a very little Battery and thought about the idea to get this energy from your mobile phone (with a cable which you plug in like the normal charging cable).

Possible or not (please explain)?


texts: Why cable TV frequency range ends at 1 GHz?

texts: Currently frequencies 50-1000 MHz are allocated for TV and data transfers. I understand why there are limitations for aerial or satellite transmissions, but why are they retained for cable transmissions? If a cable provider streams something only through RF cable network, why can't he use whatever frequencies he wants, higher than 1 GHz (ensuring that customers have correct receivers)?


texts: Send responses to GET requests - ESP8266 as webserver

texts:
I recently started working on a project in which I am using an ESP8266 to receive data from my computer or mobile phone. I do the following to set my ESP8266 as a server.

AT+CWMODE=2 //makes the module a AP
AT+CIPMUX=1 //enables multiple connections (needed for the next command)
AT+CIPSERVER=1,80 //starts a server and opens port 80

Now, incomming requests (going to the modules ip-adress in a webbrowser) will be send through the modules serial out:

IPD,0,412:GET /index.php HTTP/1.1
Host: 192.168/4.1

My only issue is that the webbrowser will keep on loading, because it is not getting any response from the server it is trying to reach. I would like the module to be able to send an 'OK' back to the computer so it knows it doesn't have to resend its data. I have tried using

AT+CIPSEND=<id>,2,"OK"

but I haven't got any luck so far..

Does anyone know how this could be done?


texts:
My signal generator drives a 50 ohm coaxial cable, terminated with a 50 ohm to ground at the input of a voltage amplifier.
However, when I look at my input signal over frequency, it doesn't behave as I expected.
When I remove the connection to the amplifier, then it is all fine. I get an almost a straight line, with some +/- 5 mdB curves. This leads me to conclude that the problem comes from the input impedance of the amplifer, changing with frequency, which again leads to an impedance mismatch of the cable.
The frequency range I am interested in goes up to 50 MHz, where there is already a change of 0.5 dB.
The cable has a length of 1 m. The gain of the amplifer is 10. The generator also has a 50 ohm series resistor (Rser.)
What can I do about that, or what is the general procedure for this kind of problem?
See the simulation in LTSpice.

Many thanks!
EDIT: The generator has a DC offset of 300 mV (see SINE(300m) and an AC amplitude of 250 mV.
The parameters for the cable are specified for 1 meter. The only thing to change is the parameter "len" for the length of the cable, the other parameters remains the same.
EDIT 2:
See the following image: I reduced the length of the cable to 0.1 m. Of course, now at f=50 MHz, I only have approx 200 mdB of change.

The next image shows how it behaves when the cable is disconnected from the Input of the Amplifier at a length of 1 m. Only a minimal change of some mdB, which are negligable


texts: Finding total energy for RC discharged capacitor at t = ∞?

texts:
Most Rc circuits are not as severely difficult as this kind of circuit. I'm trying to solve for both the time constant and the voltage V2 across the R2 resistor, both of which will hold the necessary values needed to find the total energy for the capacitor.

However, despite knowing that the time constant is RC, I'm uncertain as to whether I ended up with the right equivalent resistance, Req, that's used to find the time constant. I was under the assumption that with the modified approach I took to find Req, it came out to be 5000 ohms, leading to a time constant of 25 ms. I'm almost certain this part is done right.

For (b), I understood that because a discharging capacitor is involved, the initial voltage for the capacitor would be zero: vc(0-) = 0, such that it would equal vc(t=0), based on the given assumption. Unfortunately, beyond this, I am stuck on where to proceed next in finding vc(0+), V0 (initial voltage) and other key variables needed to solve for V2. My instinct tells me that finding the voltage across the capacitor, Vc(t) is likely to be needed for (c), but I could be wrong about that. For an RC circuit with a discharged capacitor, I am still confused as to how to approach this circuit. And then there is finding the total energy of the capacitor, which I believe is dependent on the voltage across capacitor too?


texts: Is running two voltage regulators in parallel safe?

texts:
Components

Battery (7.5V 6A Max)
D24V25F5 (5V 2.5A step down)
U3V50F12 (12V 5A step up)
Raspberry Pi 3 (5V 2.1A-2.5A)
Motor (12V 3A stall) (Using H-Bridge)

Would the setup be suitable? I much prefer to use one battery instead of two batteries in which one battery runs to each of the voltage regulators. Below I have included a drawing of how I'm going to solder them onto a prototyping PCB.


texts:
My question's subject is the SMPS(PWM) AC/DC converter design used for chargers.
There may be more ways to make what I'm speaking about, so I'll try to narrow the list down.
The circuit works using a current mode PWM controller, SDC606.
It uses a flyback transformer. This is the charger:

By taking a look at the datasheet's controller I found out the circuit is different than a smoothed rectifier with the output connected to a buck converter. The typical application of the IC shows connections to a transformer winding and to an optcoupler.
After measuring the output DC voltage of the charger, I decided to do the same by setting the dial of the DMM to VAC. The display showed 2V,then the valued changed to 0V, then it changed again to 2V and so on. The time period was approximately 1s. This resembled a square wave.
How does this kind of topology, the one used for this charger, work using PWM?


texts:
I need some help with this circuit. I have simplified it in three steps.
The task is to find the current I. The values to e(t), Z1, Z2, Z3, Z4, and the turn ration N1/N2 are known. I'm not quite sure if I have even done the transformer conversion correctly. But my main question is the current I.
Z4 = Z1 + Z3


texts:
I have a device that has a terminal that goes to 5v at certain times. I wish to sense that voltage with an ESP32. I have built this circuit using an optocoupler:

simulate this circuit – Schematic created using CircuitLab

How would this circuit change if I wanted to detect 12v instead? Is it just a matter of switching R2 for a higher value?
I see that voltage dividers can also be used for the same job, but I think that would only work in cases where the sensor and MCU share a common ground. How can I achieve that in this case (if at all I can/should)?

EDIT: As requested, some details of the system.

The MCU is running off 5vdc converted from 8vac provided by a bell transformer connected to the mains (it is already sensing the doorbell using optos).

The device is an alarm panel, that has various terminals to attach motion sensors (that go to 5v) as well as provide signals that the alarm is set or has been triggered (these terminals go to 12v). The panel is connected directly to the mains, but I can see it has a built in transformer, as well as terminals providing ground and 13v.


texts: LM1084, should I leave the copper area connected to the TAB floating?

texts:
I am using the LM1084 in a DDPAK package as a 5V USB voltage regulator on 4-layer board.
The TAB of the package is internaly connected to pin 2 (OUTPUT).

I am not sure what to do with the copper area connected to the TAB. Which of the following options should I choose:

leave the copper area connected to the TAB floating
connect the copper area connected to the TAB to pin 2 (OUTPUT)
use the copper area connected to the TAB as a the primary OUTPUT connection, leave pin 2 floating


texts: I have to switch a signal (uA to nA) between two precision resistors (stability 0.2 ppm/degC). Is this possible to do with electronics? We cannot do it with mech relay contacts because of stability problems (maybe oxide layer etc).


texts: How to obtain negative voltage from positive voltage ?

texts:
My question is simple. I have one power supply which generate 28 volt. I would like to obtain -18V and 18V. I don't want to voltage divider with resistor. I generated 18 V to use regulator. But I couldn't generate negative voltage. Is there any component which does this conversion ? if yes there is, Can I simulate it in multisim ?
Thanks for your coorperation


texts: Increasing gain of PMOS two-stage op-amp

texts:
I am trying to increase the gain of a two-stage PMOS op-amp I have designed below shown in this schematics:

The gain currently hovers slightly below 71dB, but I have to increase it to above 75dB. I am lost at which parameters to tune as some of the parameters seem interlinked to one another, though I am aware overall that Av = gm*rout.

I need to keep the Vswing at above 1.0Vpp, while I have designed on paper, to have Vout = 1.5V.

May I ask for advice on this?

Thank you so much! :)

Update 1: I have managed to get the desired gain after increasing channel width and tuning M6. However, I realized my output swing is not symmetrical and I suspect there is clipping at the bottom. May I ask how should I resolve this? I have tried changing the aspect ratios of M3, M4 and M6 but to no avail.

Update 2: I have further tuned the specs to make the output swing up and down approximately equal, with the new schematics and plot below:


texts: Gate and Drain ringing on a highside MOSFET Driver

texts:
I have designed a high side driven buck-boost converter. When proceeding with the wave forms, I'm getting a considerable amount of ringing in both drain and gate (kindly see the attachments).
To avoid the gate ringing I have tried using Zener Clamp Diodes but didn't work. Currently I'm using 47 ohms gate resistor and yet the ringing is there.
About the drain ringing I still have no clue on what can be done to avoid it.
It would be a huge help if anyone can be of any help. Thanks in advance!

V_DS

V_GS

V_GS Zoomed

Schematic Diagram


texts:
Will this open drain LED driver circuit work ?

The open drain IO is governed by the following equation
0.5 <= V_LED_OUT <= 3.6 V (abs_max)
V_LED_OUT is the voltage from open drain IO pin to ground.
The FPGA is iCE40 Ultra.
LED driver Tech-note. This tech-note provides the governing equations in Appendix-C.
CDBU0520 is a schottky diode with a VF = 0.36 (max) at a IF = 100 mA.
SFT722N-S is the LED with VF= 3.2V (typical) at IF = 20 mA.

When the IO is switched on it can sink upto 24 mA (max). In the ON state of the IO , the voltage at the fpga pin will be (5 - 3.2 - 0.47 - R_drop).
It would always be less than 3.2 in the ON state of the driver. So the above equation is satisfied and there won't be harm to the IO.
In this case , what is the current that will be drawn from the supply ? since diode and LED forward currents are different.

Now , when the IO is tristated , i think the equation would fail. since both the LED and diode would be reverse biased and more than 3.6 V would be available at the IO and it could get damaged. Is this analysis correct ?

When the open drain IO is tristated , what is the voltage at the pin , how to calculate it for the current scenario ?

Is there any option to get this circuit to satisfy the above equation even in the off state ?

I fundamentally want to understand the circuit operation when IO is tri-stated(OFF). How will the voltage at IO will be less than 3.6(abs_max) ?       If the leakage of diode and LED and IO_buffer determine the voltage at IO pin could you provide elaboration with example either general or specific to this circuit.


texts: How to mitigate change in amplitude when transmitting signal from coil?

texts:
I connected 2 equal coils, one from a function generator and the other to an oscilloscope. The signal is transmitted OK, but the amplitude varies with frequency. How can I mitigate this change in amplitude ?

The whole scope of this test is to transmit the signal from a function generator and read the signal with the oscilloscope over a very short distance (no more than 5cm).

Thanks


texts:
Does VHDL specify how intermediate calculations are handled? For example, I have the following constant defined in one of my entities.

constant MAX_ADDR : integer := (1024*1024*1024*8)/64;

In Aldec's ACTIVE-HDL simulator the constant correctly evaluates to 134,217,728. On the other hand, in Vivado the (1024*1024*1024*8) portion of the calculation appears to overflow the 32bit integer type prior to the division by 64, leading to incorrect synthesis (and several hours of builds, debugging, and frustration).


texts: Why is distilled water used for cleaning circuit boards

texts:
I've been reading up on distilled and deionized water and I've come across conflicting information.

If compared to regular tap water there are little to no minerals, is this the reason they're used because they're "hungry" for ions so they actually strip away any corrosion caused by mineral deposits? (If it's being used a cleaning agent)

That's my take on it and it got me wondering if that then makes distilled/di water corrosive if it's accidentally used on electronics when not intended to as a cleaning agent?


texts: Comparison of Series and Parallel LC Filters for Noise Reduction

texts:
Since there are two basic types of LC circuits that can be used for passing/blocking signals, I'd like to know the differences when using series or parallel LC circuits for noise at a known frequency.

Of course, the parallel LC (tank) circuit is a stop band filter:

and the series LC circuit is a pass band filter:

However, if one wanted to remove a signal with frequency f, one could either use the parallel LC circuit tuned to that frequency to resonantly absorb the signal, or the series LC circuit tuned to that frequency but shorted to ground to preferentially pass that signal to ground.

Which is better to use and why?


texts: Two possible realisations for amplifier network - which is better, when and why?

texts:
Suppose the following transfer function should be realised using idealised components,

\$H(s)=-\frac{s+12}{s+8}\$.

I now define the following functions to act as "building blocks" for a network:

\$\textrm{INV}(Z_1, Z_f) \$ constructs an inverting amplifier configuration with given impedences, where \$Z_f\$ is the impedance in the feedback path.

\$\textrm{INV}_{A_V=n} \$ constructs an inverting amplifier with given voltage gain, \$n\$.

An equivalent \$\overline{\textrm{INV}} \$ is used to construct non-inverting amplifier networks in a similar fashion.

It is clear that \$H(s)\$ can be realised by \$\textrm{INV}(s+8, s+12)\$.

By writing \$H(s) =-1(1+\frac{4}{s+8})\$, this shows that it can also be realised as \$\overline{\textrm{INV}}(s+8, 4)\textrm{INV}_{A_V=-1}\$.

I would presume that the first method would be preferred, due to less energy dissipation (only one amplifier). However, are there any real applications in which the second method would likely yield better results when physical components are taken into account?


texts: 4 quadrature clock vs 2 quadrature clock + falling edges

texts:
I started a digital design - a high precision time counter actually - that will be implemented on a Xilinx FPGA. I will describe it in VHDL.

I read several papers about this subject and I found about that I can use multiphase clocking {0°, 90°, 180°, 270°} in order to reach a higher sampling frequency. I can use the Xilinx IP PLL (clocking generation) for doing the heavy lifting.

The thing that's been puzzling me with multiphase clocks is : why using a four-phase clock in quadrature {0°, 90°, 180°, 270°} when you can just trigger your process on the falling edges of a two-phase clock in quadrature {0°, 90°}?


texts: What is Stray Capacitance and how it can be Avoided

texts: I have learned that especially in RF circuits stray capacitance can mess circuits up.  I have learned that breadboards are a major culprit for this. However I do not know really what it is. What is stray capacitance and second would this board generate stray capacitance?


texts: Why is the positive side said to have a higher voltage than the negative side?

texts:
My question is, are textbooks just saying the positive side of a battery has a higher voltage because mathematically + is higher than - even when, in reality, there is nothing to come out of the positive side?

The whole "convention" is really confusing me because "potential" semantically requires the one having potential being the one to exert power, when in reality, the positive terminal has no power to exert.

Or is my understanding a little off? Please help!


texts:
I am driving a STD3NK80Z-1 MOSFET at a rate of approximately 105kHz using the UCC28700 by TI, and I want to make sure my gate drive circuit is correct. I am going to use the schematic below as a starting point.

First, let's start off with an explanation of the schematic, so we can make sure my understanding is correct.
R1's job is to limit the in-rush current, and keep the drive pin from going over it's current source capacity.
R2's job is to dampen the ringing observed when the gate signal goes from hi to low - basically just solving an RLC circuit.
In my case, the UCC28700 self-limits the source current of the DRV pin to 25mA, so I don't need to worry about placing a current-limiting resistor.
For R2, I found an equation in TI's "Fundamentals of MOSFET and IGBT Gate Driver Circuits"
Rgate,opt = 2*sqrt(Ls/Ciss) -(Rdrv + Rg,i)
I just plugged my numbers into that equation, and got a value of about 6.5 ohms.
At 14V (the drive pin's voltage), 6.5 ohms won't limit the current enough to reduce it below the self-limiting value, so I can just place it in series with the gate pin of the FET.
As a result, I will not need either of the diodes because current can flow through the resistor during the on phase and the off phase. This results in just a single resistor in series with the gate pin of the MOSFET.
My questions are:

Is my understanding of the functionality of the two resistors correct?
Is that a good value for R1?


texts: Getting the desired output voltage swing from the op amp output

texts:
I am designing a microphone preamplifier circuit. I have used op amp OPA 37 which amplifies the signal coming from the microphone to be used by the ADC. The usable voltage range of ADC is 0-2.5V. I am using a 9V power supply and two biasing resistors at the input to obtain the output voltage swing. The bias point is at 4.5V. I want to know what can be done at the output of the op amp to get the bias point at 1.25V so that it can be used by ADC.
In the actual circuit microphone replaces signal generator.


texts: Memory architecture and instruction storage - Naimi: AVR Microcontroller

texts:
LDI R16, 0x25 --> E 2 0 5 --> 1110 0010 0000 0101

Apparently, in AVR, the code and data are stored separately and each
area (code, data area) is accessed by a unique bus.
Now since the Program Counter contains the address to the next
instruction which in this case is LDI: PC --> E (PC points to 'E')
My question is, when loading the data parts (instruction) within 1 clock
cycle, well.. opcode 'E' is directly referred to by the PC. How does the
CPU find the data portion (0010 0000 0101)?
Or have I got it entirely wrong and are the 2 bytes (E + 0010 0000 0101) of the instruction
the 'code' and kept as a single unit in the code area. In which case
what is the data area - is that for instructions that use memory
addresses: eg,

LDS R10, $FFFF
Here code is the bytes for the entire instruction and the data is
probably populated by the assembler from some variable assignment?

Why then does he say:

In Sections 2-2 and 2-3, you learned about data memory space and how to
use the STS and LDS instructions. ?Then the CPU wants to execute the
?LDS
Rn,k? instruction, it puts k on the address bus of the Data Bus, and
receives data through the data bus. For example, to execute ?LDS R20,
0x90?, the CPU puts 0x90 on the address bus. The location $90 is in the
SRAM (see Figure 2-4). Thus, the SRAM puts the contents of location $90
on the data bus. The CPU gets the contents of location $90 through the
data bus and puts it in R20.

WTH? Could someone clearly explain AVR code/data bus architecture and how
instructions are fetched and executed?


texts: Installing (and soldering to) PTFE (teflon) Insulated Terminals

texts:
I am doing a condenser microphone board project. Now I need to install two PTFE insulated terminals (these are in the picture) to a board. The holes are a little larger than the bushing of the terminals.

The question 1. How can I make the terminals stick inside the hole?  Do I need to use some glue or maybe rivet over the short ends of the pins?

The question 2. Is it OK to solder some of the components to the short end of the pin?


texts: how to calculate self discharg %/month for lithiam ion battery?

texts:
I have lithium ion battery have
-C-rating=0.2C
-Max. capacity= 1050mAh
-Nominal voltage = 3.7V
-Maximum voltage = 4.2V

So i want to calculate self-discharge %/month so how i calculate this suggest some stranded equation for this calculation


texts:
I am working on a zigbee wireless remote. MCU datasheet says it operates in wide voltage range of 1.8 to 3.8 volts.

Besides zigbee MCU, there will be a few LEDs and tact switches (fairly simple and straight-forward circuit).

I am leaning towards using a li-po cell in my design. (previous thought was a CR3032 coin cell but moved to li-po for higher capacity and to make it easily rechargeable by any mobile phone usb-c charger. Rechargeable battery appeared to be more user-friendly.).

Are there any major draw-backs in terms of safety and product life just because a li-po cell is present? I am targeting a product life of 5 years or more. Remote will have to be charged every 6 months or so.

Below is the discharge profile of a li-po cell:

The usable capacity of the cell lies in a voltage range of 4.2 volts to 3.6 volts. As such, how do I make the most of it? What kind of voltage regulator will give me best efficiency? Should I just do away with a regular diode? 0.7 V drop keeps me in fairly safe zone.

At full charge, I get 3.5 V and at low charge (3.6 V cut-off), I get 2.9 V. These are very comfortable voltages for my zigbee MCU.


texts: Why are there sensors that encode their readings as serial sequence of PWMs?

texts:
This is a comment of @CuriousCat, but I think it deserves the attention of an actual question:

The sensor used in the original question outputs a serial PWM-style signal like this:

  What's the advantage for a sensor to encode its output in this way rather than the more conventional 4 to 20 mA (I'm used to seeing process sensors use this all the time) converted to digital at the receiving end?

  Is this more accurate?

  Alternatively why not go HART / PROFIBUS etc. ?

Follow-up questions moved to separate question: Are there standards for digital sensor links?


texts:
I have the following code:

constant HALF_RANGE: unsigned(RANGE_WIDTH-1 downto 0) := (RANGE_WIDTH-1 => '1', others=>'0');

where RANGE_WIDTH is a generic of type integer. It does exactly what is should: Generate a constant where the first bit is 1 and the others 0.
The only problem is: It generates a waring using Questa Sim:

(vcom-1073) Non-locally static choice (association #1, choice #1) is allowed only if it is the only choice of the only association.

What does this warning mean? What would be the right way to define such a constant?