texts:
I'm looking for a mechanical relay that can run 500 amps when closed. There are solid state solutions for switching such currents (SSRs, IGBTs, etc), and we do use them, but for a low speed H-bridge to polarity-invert some coils, I would rather avoid all the voltage drop of using IGBTs. I would not need to "hot switch" the full 500A, the switching would only take place when no current was running.

Parts that I've come across:

Omron G9EC series: Rated to 200A, with an exhaustive datasheet that looks trustworthy.

Stinger "SGP35" relay: supposedly rated to 500A, but the datasheet doesn't instill much trust. See for yourself: http://www.stingerelectronics.com/productDetails.aspx?ProductId=89&CategoryID=2

Has anybody got experience with either of these, or with other high current mechanical relays?


texts: How to find SMD resistor and capacitor value and correct size

texts:
I'm new to the SMD world and struggling to find an easy and quick way to get the correct SMD resistor and SMD capacitor size and value based on a circuit schematic; any tips will help.
For example, I'm designing this circuit in SMD but don't know how to find the right SMD size, because there are many sizes - (I'm using Altium Designer for PCB design.)

If someone can guide me by looking at the resistors' and capacitors' values from the above diagram and tips on finding the correct size, it would help me further.


texts: What's causing my 12V DC power supply to tick around 5-6Hz?

texts:
I have this lamp which runs off of a 12V DC power supply provided. There's a faint ticking sound coming from the power supply, sort of like the sound and volume of a watch tick, but it's happening around 5-6 times per second. What part of the power supply would cause this audible effect? Is it some kind of switching relay for AC rectification? If it helps, this happens whether it's on or off.

Please note I'm not looking for advice on how to dampen the sound, I'm just curious.


texts: PIN Photodiode gamma detection amplifier circuit - rectangular wave output

texts:
I've been working on a project recently, where I need to build a device which detects gamma radiation and can be used for gamma spectroscopy. I've done some research and found many interesting ways of achieving that but at the end I chose to go with X100-7 PIN Photodiode.

I'm more of a software guy, without much expertise in electronics so as a first step, I've decided to build&test a prototype of the measurement circuit. I've copied 95% of the design proposed by the diode's manufacturer - it can be found here (last page) and my design looks like that:

The only differences between my project and the design from the document are:

C5 in the feedback loop of the second OpAmp, someone told me it's a good idea to limit the bandwidth,
Used AD8639 instead of the ICs proposed by the manufacturer, simply because I've had them in my junk.

So, as you can see on the picture, I'm connecting the diode to J3. I'm powering the whole board with 15V from my regulated power supply - Zhaoxin RXN-1505D. The Jumper J4 is only there to be able to disconnect the second stage amplifier and easily measure the output of the first stage. Normally it stays closed.

So at the moment, all I'm getting on the output is a rectangular wave with Vmax equal to the voltage I'm powering the circuit with. What's more funny, the output stays the same even when there is no diode connected to the circuit.

I tried powering it up with a 9V battery but it stayed the same (wave had an amplitude of 9V).

Normal behavior of the circuit should result in a single voltage impulse every now and then when a gamma particle hits the photodiode, with an amplitude far below the Vcc.

I guess this behavior has something to do with noise - that's why I haven't made this prototype on a solderless breadboard but on a homemade PCB. I know it looks like a mess but my soldering skills aren't something I'm proud of and my hands tend to get shaky sometimes.

So my questions are:

Does any of you have an idea of what might be wrong here?
Is there anything I can do to further investigate the problem? If you'd like me to provide some waveforms from other parts of the circuit I'd be happy to oblige.
Is there any possible hot-fix that I can apply here to get rid of this behavior or should I use some completely different design?


texts: Getting negative energy in a coil (RLC-circuit) after opening the switch

texts:
I've the following circuit:

simulate this circuit – Schematic created using CircuitLab

The switch was 'forever'closed and a certain time \$t=0\$ I open the switch. I tried to find the energy of the coil when I opend the switch over all time that the switch is open:

$$\text{E}_\text{total}=\int_0^\infty\text{P}_\text{L}\left(t\right)\space\text{d}t=\int_0^\infty\text{V}_\text{L}\left(t\right)\cdot\text{I}_\text{L}\left(t\right)\space\text{d}t=$$
$$\int_0^\infty\text{I}_\text{L}'\left(t\right)\cdot\text{I}_\text{L}\left(t\right)\cdot\text{L}\space\text{d}t=\lim_{\text{n}\to\infty}\left[\frac{1}{2}\cdot\text{L}\cdot\text{I}_\text{L}\left(t\right)^2\right]_0^\text{n}=$$
$$\lim_{\text{n}\to\infty}\left(\frac{1}{2}\cdot\text{L}\cdot\text{I}_\text{L}\left(\text{n}\right)^2-\frac{1}{2}\cdot\text{L}\cdot\text{I}_\text{L}\left(0\right)^2\right)\tag1$$

And I found that that is equal to:

$$\text{E}_\text{total}=-\frac{\text{LV}^2}{2\text{R}_1^2}\tag2$$

Where \$\text{V}\$ is the source voltage.

  But that means that the energy in the coil is NEGATIVE when I open the switch? Is that possible or logical? I do not see why.


texts: AVR Measuring frequency using external interrupt - where are my cycles going?

texts:
I'm using an external interrupt to measure the frequency of a signal, the AVR clock is at 8MHz.  I'm essentially counting the ticks between pin toggles using a 16 bit timer (with some handling for overflows for slow signals).

The skeleton code is as follows:

int main(void){
clearbit(DDRD,PD2);
PCMSK3 = 0x00;
setbit(PCMSK3, PCINT26);
setbit(PCICR,PCIE3);
setbit(TIMSK1,TOIE1);
setbit(TCCR1B, CS10);

while(1){
}
return 0;
}

ISR(PCINT3_vect){
    togglebit(PORTD, PD1);
    countl = TCNT1L;
    counth = TCNT1H;
    soverflow = overflow;
    overflow = 0;
    TCNT1 = 0x0000;
    return;
}

/* Overflow timer */
ISR(TIMER1_OVF_vect){
    overflow++;
    return;
}

This works pretty much as desired, however I'm unable to measure anything shorter than around 49 cycles.  The two scope images show the problem.  The yellow trace is from the external oscillator, the blue trace is the pin toggle inside the interrupt handler.  There is nothing in the main loop, and having things there doesn't change the results significantly.  All the variables are uint8_t.  Reading the count in high and low bytes gained a bit of speed (compared to a single 16 bit read/write).

The best I've been able to do is ~95kHz, but I'm curious as to where the lost cycles are going.  The assignments can't be more than a few cycles each and if I understand right, ISR basically calls cli() on entry and sei() on exit, so the only thing that happens is the timer gets reset, the function returns and we wait for the next toggle.

EDIT

void get_count(void){
    uint8_t i=0, oldpin, newpin;
    setbit(TIMSK1,TOIE1);
    setbit(TCCR1B, CS10);
    sei();
    while(getbit(PIND, PD2) != 0){
    continue;
    }
    while(getbit(PIND, PD2) != 1){
    continue;
    }
    TCNT1 = 0;
    while(getbit(PIND, PD2) == 1){
        continue;
    }
    countl = TCNT1L;
counth = TCNT1H;
    TCNT1 = 0;
    soverflow = overflow;
    overflow = 0;
    clearbit(TIMSK1,TOIE1);
clearbit(TCCR1B, CS10);
    cli();
    return;
    }

This gets me down to around around 400kHz before things start getting iffy.  Not sure there's much more I can do to make it lower.  I wait for the pin to transition to 1, start the timer and time how long it takes go to zero, i.e. half a clock cycle.


texts: How to interface Beaglebone with a temperature condtioner with 0-10V as output?

texts:
i have a beaglebone card, a temperature sensor PT100 and a temperature conditionner.
I'm new in beaglebone, as i see the ADC is already in beaglebone but the voltage is mx = 1.8V
With my industrial temperature sensor, i connect the power supply 24Vdc, connect the PT100 then the output will be in 0 to 10V

What circuit do i need to interface the temperature conditioner with beaglebone card?
Should i use a voltage divider? if yes can someone guide to a basic diagram.
Should i use LM317 as voltage regulator?
I found this circuit in internet.
Thank you


texts:
Bit of a newbie question here...

I want to build a battery powered LED light for use outdoors. So basically needs to be pretty bright and last a while.

If I have battery rated like this:

5.0Ah 6V
Discharge current 20 hr rate 250mA
Capacity:
20hr rate (0.25A) 5.0Ah
10hr rate (0.50A) 4.3Ah
5hr rate (1.00A) 3.8Ah
1hr rate (2.70A) 2.7Ah

An LED rated like this (lumens):

Forward Voltage: 3.7V
@ 350mA   : 100
@ 500mA   : 130
@ 700mA   : 185
@ 1,000mA : 250

So I want to create a circuit where I can switch between using 0.25A and 0.5A from the battery.

So, if I were to create a circuit with just the battery and LED, would the LED draw the maximum current it is able to? (lets say that's 1A, so it lasts 5h) Or would the battery dump all it's power into the LED since there is no resistance in the circuit?

To get the circuit running at 0.5A, by Ohms law, I would need to add in a 12 Ohm resistor (I think! - 6V / 0.5A)

Does the addition of the resistor reduce the power drain of the circuit?

Do the resistors regulate the current from the battery in a way that will extend the life of the battery?

Also, if the forward voltage for the LED is only 3.7V in a 6V circuit, how would I go about reducing the voltage for the LED?


texts: Implementing UART flow control in microcontroller

texts:
I'm communicating data from my microcontroller (Teensy) to my Bluetooth module (nRFx) which is also a microcontroller that I can program. I use UART to communicate the data I want to send over Bluetooth from the Teensy to the nRF, but nRF sends Bluetooth data slower than the transmission of data from the Teensy (UART speed faster than Bluetooth speed). Because of this I need to implement hardware flow control so the nRF buffer doesn't overflow.

I have RTS and CTS pins on both microcontrollers and I'm currently writing in Arduino (this might change to nordic's SDK for the nRF). My question is, can I just connect the RTS and CTS pins and "activate" the flow control somehow and it just works? Or do I need to program them my self?

Teensy

nRF


texts: Induction heating circuit also stable with forward or reversed DC current through work coil?

texts:
I have need for an induction heating coil (high frequency and current AC) that can also switched to a steady forward or reversed DC current in order to create a stable magnetic field in the work coil - is there any way of achieving this without giving up on soft switching?

How inefficient would it be to drive an induction heating work coil with a full bridge (as used for dc motors) under logic control instead of using an oscillating circuit? In addition to the extra switching losses from using hard instead of soft switching and the far noisier emissions from the square wave instead of sinusoidal what other bads are there?

Edit:
While I have looked at the question and answers for Can pulsating DC be used for induction heating? despite giving me assurance that it is possible it doesn't help me with how to design an efficient circuit for my use case.


texts:
I am designing a PID controller for my beam steering application. I have lateral position sensor detector (PSD) PSD LINK to detect the position of beam. The problem is that the output of sensor seems to be quite noisy than the required accuracy. The sensor has a resolution of 2.63 micrometers but the noise in sensor seems to be way higher. Here is the sensor output data when beam was stationary..

I don't want to do any low pass filtering on the sensor data as it will reduce  bandwidth of closed loop system, so I am left out with estimation of actual signals from the noisy data, as I could not reduced this noise further.
Could anyone suggest what kind of estimations or observers should I use? How could I model this sensor? Will system identification in MATLAB help in modelling this sensor anyway? Also the histogram of the noisy data (from above plot) looks to follow Gaussian distribution as shown below.

I read about kalman filtering but I am not sure how to apply it in this particular application. How can I proceed further?

Thank you.


texts: How do you implement wifi with a front-end chip?

texts:
I was looking around for a solution to hook up an application with an MCU to a wifi network. I'm basically looking for a chip that can talk to my MCU via an interface like I2C or SPI and is able to connect to a wifi network so that I can do some IP traffic. I'm okay with putting my own antenna and the necessary RLC stuff on the PCB.

I've found a bunch of really expensive modules which didn't seem very interesting (and were basically a lot bigger than I expected) and I've found the max2831 which looks like it might be good enough for the job.

However the data sheet doesn't contain too much detail about how to actually use the chip, ie. how to send commands to it, what kind of commands there, etc. The manufacturer says that this is just a "WLAN front-end solution", so I'm getting the impression that this chip isn't what I'm looking for, or at least isn't what I expected.

I googled around but didn't find any information about how to actually use this chip to connect to a wifi network and send/receive data.

Could anybody please shed some light on what exactly a "WLAN front-end" means and how to use it to implement the ability to connect to a wifi network?


texts: Do mosfets without protection diode exist?

texts: If they do exist, what is advantage of using them? How often are they used in comparison with mosfets that have integrated diode?


texts: Could you explain me please what does this question exactly want me to find? Or, how should I start solving ?


texts: MCP25625 is not sending CAN messages out from chip

texts:
I was using MCP2515 and now I want to use MCP25625.
I connect the new chip MCP25625 and observe 1st SPI interface and it's working properly because I can read and write register correctly.
The CAN initialization is also set without any error and program starts transmiting CAN messages, but on the other side, I'm unable to receive these messages. The mode is NORMAL and status register return 0.
If anyone has an idea then please share.


texts: a circuit which connect one usb to two cpu

texts: i m looking for a circuit in which a usb can be connected to two cpu via a switch just like KVM switch but the only diffrence is that when one cpu disconnect the usb cable then the switch operated and connect the usb to 2nd cpu.


texts: Selecting a triac for AC dimming with a 5V Arduino

texts:
Im working on a project where I need to dim some ac lights with an arduino using a triac. I would like to be able to use 8A per triac at 120v, and it will be controlled with a 5v Arduino. How do I select a triac for this? I was looking at the BTA24-600BWRG because it is used as a replacement for a product similar to what I am making with the same current ratings, but will it work with a 5V arduino? With the number I need of them it will get kinda expensive so is there a cheaper one I can use? Also what is a good circuit for this (including zero-cross detection)? I have seen a few that use slightly different parts and values.
Thanks!


texts: Li-Poly battery charger with protection - Schematic review

texts:
I need to build a Li-poly battery charger.

The intended schematic of the circuit is as follows:

J1 is connected to the battery.
PMOS connects and disconnects the load to and from the battery
IC charges battery based on Li-poly (CC/CV) requirements
D1 is there to prevent any feedback from battery to USB

The intended operation is as follows:

When USB present and device needs to work, VSupply is directly provided by the USB and PMOS separates the battery from the supply. (R3 ensures PMOS is on when there is no USB) Primary reason for this is not to disturb the proper charging of the battery. Especially battery is in 2.5V level, it needs to be trickle charged to 3V and than maximum current can be applied. However without separating the battery from the supply, I couldn't come up with a way to make this work, hence the PMOS.
I need to find a PMOS that cuts off when Vgs is .5V or so. I haven't checked yet but hopefully it is possible.
My circuit takes less than 500mA at any given time however I cannot gurantee how much current can be allocated to the battery. This is a point I don't know how to deal with. How do I guarantee the bulk of the current goes to device and remaining used for charging? Should I put a resistor between battery and BAT pin of the IC to increase its impedance so that most of the current goes to the load.

Based on datasheet of this device (STC4054),


texts: The documentation for a chip that I'm trying to use says it needs 2.7 to 3.6V. When I use a multimeter and put on probe on Vin and the other on GND I read 1.7V. Is this the correct way to read supply voltage? Does this mean that it's not getting enough voltage?


texts:
First off, let me apologize if this question is too basic for the community - I've searched quite a bit for a solution, but wasn't able to locate anything.

I'm a hobbyist working on a project that would require a circuit to be closed when an object is out of bounds on an inclinometer (basically a curved level) .  I would like to use a rudimentary ball inclinometer (as pictured) over a more complex electronic solution.

I my goal is simple: close a circuit to activate a LED when there is more than a 5 degree bank - or alternatively, open a circuit when the ball leaves the +/- 5 degree range.  I can't seem to locate a device that would accomplish this goal commerically and would like to build it for my own use.  I'm stumped as to how to build this, though it seems as if it would be fairly simple.

My only other requirement is that the solution does not involve magnets, as it will be mounted on metal housing which could effect accuracy.

Thoughts?


texts: What is the most efficient way to effect a voltage drop in a dc cct?

texts:
I have a 24V supply and need to drop the supply voltage to 19V to power a TV set.

The plug pack that powers the TV states the output as 19V and the current at 2.1A

I could use a resistor to drop the voltage but it would need to have a high power rating. Can anyone suggest a cct using easily obtained components to solve this problem?


texts: What's the input resistance of an opto-isolator?

texts:
I need to sense if a 48 volt power supply is supplying voltage or not, I plan on doing this with a opto-isolator and I am happy with the output circuit from isolator.

Can I connect the input of the isolator between 48 and 0 volts, or do I need to add in a extra resistive load to avoid a shortcircuit style scenario?


texts: Does an ideal capacitor dissipate power?

texts:
On several circuit simulators I have seen capacitors with a "Power" figure.

Also, I have wondered how capacitive power supplies work.

Does an ideal, zero resistance, zero leakage, zero inductance capacitor dissipate any power?

See image:

Link to simulation of this schematic


texts: Using more than one voltage regulator in series

texts:
Is there any problem (in addition to a likely loss of current) in using more than one voltage regulator (L7812CV) in series? And is there a real gain in stability?

I ask this because I 'm going to use some high precision components in a car, using it's battery.

Edit.: My bad, I'm new to electrical engineering. I was thinking that voltage regulators are more like a stabilizer. For ex: inputing either 14v or 9v, it will force 12v in output by varying its current. So i guess that this question doesn't make sense.

There's any other way then to stabilize the voltage of a car battery to guarantee 12v?


texts: Where to start when considering making a GPU?

texts:
I saw this video the other day and it got me thinking about how to go about and design something like the GPU. Where would you begin? I'm more just interested in reading about how they work and not making one out of TTL(yet anyway).

I know this sounds like a 'how do you make a programming language' question but any starting points would be good as I have no idea where to start looking.


texts: Oscillations in voltage-controlled current source with MOSFETs and opamp feedback -- Why?

texts:
I have a circuit that should operate as a voltage-controlled push-pull current driver, able to source or sink at least 2A (into a 1 ohm load).  It has unexpected oscillations on the output current.

Circuit components:

U1: LM358P "rail to rail" opamp
Q1, Q2: IRL540NPBF power MOSFET, 36A max
D1: 6A10-B rectifier, 6A max avg forward current

Note: Despite the feedback loop being connected to the noninverting input, the opamp has negative feedback because Q1 and R_D form an inverting amplifier.

Quick description of circuit operation

\$V_{IN}\$ controls the current.  \$V_{IN}=3.3V\$ (roughly) should give \$V_{L}=5V\$ and therefore zero current through \$R_L\$.  This aspect works properly, and the circuit is stable under this condition (no oscillations).  With \$V_{IN} < 3.3V\$, the circuit should sink current from \$V_2\$ through \$R_L\$, D1, and Q1, to GND.  This somewhat works, in that the mean value of \$V_L\$ decreases below 5V (to 4V, etc), but as \$V_L\$ decreases there are increasingly large oscillations in \$V_L\$.  The oscillations are (distorted) square waves at about 86 kHz.  When the mean of \$V_L\$ is \$\approx 4V\$, the oscillation amplitude is \$\approx 1 Vpp\$.

Attempts to diagnose the oscillation

In an earlier version of the circuit I thought the oscillation might be because of delays in the feedback loop, so I followed the instructions here.
I added \$C_F =\$ 100 nF to make the crossover frequency \$f = 1/(2 \pi R_{IN} C_F ) \approx\$ 500 Hz.  This made no significant change to the oscillation.

I have also bypassed the power supplies with the largest capacitors (ceramic and electrolytic) that I had on hand.

Can anyone diagnose the source of the oscillation?  Thanks much!

p.s.  The circuit was inspired by one in Horowitz & Hill 2nd Ed.  See Fig 3.75.


texts: Build Single pole changeover switch from 4066 Single pole, single throw

texts:
I am trying to build this circuit which requires two SPCO switch that go between two voltage values but I only have access to 4066N SPST switches.

I am not sure if there are better alternative designs but the one I came up with was to use two different switches and an inverter for the clock. Apologies for the terrible MS paint drawing.

Edit: That triangle thing on the second IN is a ground, not another opamp.

My question is will this work? I'm wondering if tying the outputs together like that would cause problems but I don't understand the circuit well enough to know for sure.

Also, this is more of a notation question but the first opamp only shows an input into the + terminal. Is the other one grounded by convention or is it trying to say something else?


texts: Will 126v damage a small motor rated for 120v?

texts: I have 252v coming into my building (126 per leg) and a piece of equipment which uses a percentage timer that has a small motor on it which is rated for 120v. Will 126v fry the motor?


texts: How does the TP4056 overdischarge protection work?

texts:
I want to buy this integrated circuit (IC) to charge li-po battery. TP4056 Type-C 1S 3.7V

It looks nice for charging but I am afraid of the overdischarge protection of this IC because in the schematic below it looks out pins and battery pins are shorted so that the battery will be used without any turning off (overdischarge protection) and it will demage my li-po battery. Where am I going wrong, am I seeing it wrong?


texts: Optocoupler TVS Protection for digital input module 24V 220V

texts:
I have two digital input modules that must match:
IEC 61000-4-2 ESD Contact 6kV and Air 8kV
IEC 61000-4-4 EFT 1kV
IEC 61000-4-5 Surge Line to line 0.5kV and Line to Earth 1kV

First module:
32 digital inputs 24VDC

Second module:
16 digital inputs 220VDC

The modules will be placed in metal rack and will pass the tests inside it.

These module don't have any embedded protection and only way to add it is to make an extension board that have TVS, MOV or smth else.

I have some ideas but I don't know do I think in right way.
For 24V I use TVS diodes but
1) is nominal right?
2) SMBJ or SMCJ?
3) what is right placement of TVS (1,2,3)?

For 220VDC module there is no such TVS, and I used MOV.

1) For ESD MOV is not the best solution, but what alternative do I have?
2) MOV has rather big Clamping Voltage, is it nominal safe for the module?
3) what is right placement of MOV (1,2,3)?

Any advices?
Thanks!

ltv-354T:http://www.mouser.com/catalog/specsheets/LTV-354T%20Series-1308.pdf


texts:
Wave pipelining (a technique of removing latch overheads by having two or more "waves" propagate through a multi-cycle pipeline stage) has been used in the past for pipelining cache access (HP PA-7000?). Although this design technique has issues similar to those of asynchronous design (immature design and validation tools, scarcity of experienced designers, device testing issues, increased process variation, complex timing variability based on voltage and temperature, and perhaps even increased quantization granularity of transistors [particularly FinFET?]), the variability is more constrained than a fully asynchronous design.

Using wave pipelining to group pairs of pipelines stages would not only remove latches but would also provide a simple way to halve pipeline depth when frequency is halved. (This could be done with latches by eliding the intermediate latches.)

While wave pipelining would be more problematic for a high frequency design where small variations in propagation delay would be a larger fraction of total delay, intermediate performance processors might have sufficient depth to benefit from reduced latch overhead while having sufficient tolerance for variation.

Are the modest potential benefits simply too small to overcome the above mentioned issues?


texts: How to cut the ADD to GND trace on a MPR121 capacitive touch sensor

texts:
I've been trying to setup two MPR121 capacitive touch sensors and from what I understand, I need to cut the PCB trace between the ADD and GND pins. I've tried scraping off a bit between them on the top side of the PCB, but they still are showing being connected on my multimeter.  Where is the proper location on these PCBs for cutting this trace?

Update: The module in question is a XO MPR121 Breakout

The product page has a view of the front, below is a picture I took of the back:

I see now on a product page it mentions the jumpers. I assume these are the pairs of contact pads on the back side. So do I need to cut a trace in between the pair next to ADD and then connect ADD to say SDA with a wire?


texts: Working of optoisolator MOC3041 & triac connection

texts:
1) Pl help me with the working of optoisolator MOC3041 & MOC3020.
   Also its use in ac dimmer apart from isolation

2) Also as triac(BT136) are bidirectional how does the term "reversed" connected gate of  triac come into picture?

3) what is MT & MT1 pin & its significance?

Thank you


texts: What's the difference between a generated hex file and a binary file in embedded systems?

texts:
I have an STM32 project (let's call it blinky). This project is developed using Keil IDE. It blinks an LED every 1 second. When I build it, a HEX file is generated. Let's say I want to upgrade the board using OAD (Over the Air Download). The new code allows the LED to blink every 2 seconds. In order to flash it using the OAD, a bootloader should be present. Let's suppose that this bootloader exists.

My questions are:

In order to generate a binary file and upgrade the board using OAD, what should I do in my Keil project exactly?
Should I just export the project as a binary instead of a hex file?
Are there any other configurations to do?


texts: can somebody give an analogy of what an ampere is?

texts: I'm trying to understand the difference between amperes and watts.  I have a string of LEDs that say require 5W of power and 5amps.  What's a good way to memorize the difference and significance of these two values?


texts: Why does my oscilloscope get no pulse wave when connected to my DAQ board?

texts:
I have created the following LabVIEW GUI to generate a square pulse train waveform:

As you move the frequency and pulse width knobs the waveform changes accordingly (pulse width is now 2ms).

I used the following back panel diagram to drive the logic:

I have a PCIe-6259 DAQ card that is supposed to convert the waveforms above into analog output.

I used this video tutorial to design the wiring diagram logic shown above.

If you look at the "AO Voltage" control in the wiring diagram you will see it has "Dev1/ao1" selected for analog output.

The DAQ is connected to a BNC 2110 that has the Analog Output #1 terminal.

I wired the Analog Output terminal #1 to the oscilloscope to channel 1 but I do not see any square wave pulses. What am I doing wrong?

How do you debug something like this?


texts: PNP instead of NPN in series voltage regulator

texts:
I have a question regarding PNP transistor, since I am not very familiar with it. What would be the difference in the circuit below, if we switched NPN to PNP?

Right now the output voltage is equal to \$U_D\cdot\left(1+\frac{R_4}{R_4}\right)\$

The value of \$R_1\$ is limited by \$R_{1max}<\frac{U_{INmin}-U_D}{I_{Dmin}}\$

I know that for NPN the base's voltage must be positive, while for PNP - negative. But I just don't see how this would affect this circuit.


texts: Factors that effect what current a Synchronous buck enters the Discontinuous mode

texts:
Statement 1: The current at which the Buck SMPS moves into Discontinuous Conduction Mode is not fixed and changes due to different factors.
From what I understood, a Buck SMPS enters discontinuous mode when the output current reaches below the critical current which is equal to half the output ripple current? How can it then enter discontinious mode at different currents and what are these different factors that effect this current
Statement 2: For a fixed output current From a Vout/Vin VS duty cycle plot, You can obtain two different graphs of the SMPS in discontinuous and continuous mode. You can then see when it will enter discontinuous mode
I am currently at home self teaching myself this and do not have access to do this but If I did how exactly would I push the SMPS into discontinuos and continuous when the output current is fixed?


texts: What is the capacitance of this Maytag fridge capacitor?

texts:
I have this capacitor in a Maytag fridge freezer. The fan stops when the fridge is on but works when the freezer alone is on.
I am assuming the problem is the capacitor not bring able to boost power to a higher RPM.  I can not buy the same model so am looking for a replacement.
I can not recognise the capacitance specifications on the label.
It's a starter capacitor for a 230V 60/50Hz 0.05A 1W 1300 RPM motor.
It says its 2x.47u farads but then another X2. Does that make it 1.88u farads? The replacement capacitors for fridges are typically 6uF.


texts: Calculate the effects of cooling fans on a system?

texts: If I have a home-audio receiver that draws a given amount of power (lets say 200W), and its passively cooled reaching a temperature differential of 50F over ambient, how can I calculate how much cooler it should run given a modest airflow like 10CFM?


texts: Connect 90w charger in a laptop in which the charger was 130w

texts:
Is there any permanent damage on the battery or another part if i used a 90w charger on a 130w laptop?

I need to do this, because my new 130w charger arrives only day 9 and I must continue using the laptop.

130W

INPUT: 100-240 V - 2.5 A

OUTPUT: 19.5 V - 6.7 A

90W

INPUT: 100-240 V - 1.5 A

OUTPUT: 19.5 V - 4.62 A


texts: Based on another question recently asked, this package is very common, used in high current LED applications (0.5W ~ 3W). The package includes the led chip, lens, heatsinking, but can vary in light radiation patterns. Very common, they have been around for years if not decade. But I have never found a common package name, unlike other led types (5mm, 3mm, Straw Hat, 1206, 0805, etc). Is there a common name, or even a JEDEC or similar standard to standardize this type of package?


texts:
I'm thinking about making a DIY project (this one).

I'm a complete n00b, I just have some theoretical knowledge about electronics from some university courses, and I'd like to learn some more. I was thinking about avoiding to buy the kit PCB (which is double sided) and, since I have the schematics, trying to replicate it on a stripboard. Is this reasonable, and which workflow should I follow? Make a solderless breadboard prototype based on the PCB design and then a final model on the stripboard or redesigning the layout on a CAD software? I don't know if there is a best practice about this or if it's even possible.

Thank you.


texts: Differences between bldc sensorless motor

texts:
I am designing a driver for a sensorless bldc motor and I have found these two types of motor configurations.
I attach images.

Img 1:

Img 2:

Both are bldc sensorless motors?

How can I know the difference between one physically?

If the 3 power cables and 3 smaller ones come out of a motor, are we talking about the configuration of image 2 and if only 3 of the configuration of image 1 come out?


texts: Discharging Circuit with LED indicators?

texts:
I'd like to create discharging circuit with four LEDs indicating how much charge is left from the discharging battery. It needs to be a low cost solution (no Arduinos; only simple circuit components) I'm not entirely sure how to go about this theoretically; I can only imagine that there would be parallel branches of an LED in series with a resistor. I want each LED to be lit initially and indicate how much of the original voltage/current is left as each LED goes dim:

4 lit LEDs = 100-75% charge
3 lit LEDs = 75-50% charge
2 lit LEDs = 50-25%
1 lit LED = 25-0%
0 lit LEDs = 0% charge left

EDIT: Let's says it's for a 9v battery

Edit #2: Let's say it's a lithium ion rechargeable battery.


texts: Making a light detector using a phototransistor and an open drain comparator

texts:
I want to make a light detector using a phototransistor. To do that I connected a phototransistor and apotentiometer to the open drain comparator as in the diagram below.
When the light is dim, everything is OK, but when light is bright (normally or even slightly bright) then the LED lights even when voltage of the potentiometer is more than 700mV higher than the voltage of the phototransistor.
Specifically, when I turn the potentiometer knob, the voltage between the voltage source and the comparator output rises gradually until it hits maximum around the point where comparator inputs values are equal and then it remains constant.
So my problem is that comparator doesn't work like a step function, but more like a gradually increasing function.
What am I doing wrong?

simulate this circuit – Schematic created using CircuitLab


texts: VHDL - How to reduce signal's dependencies and optimize speed?

texts:
I'm wondering how to optimize comparison a wide counter value with few defined values. Maybe it will be easier if I show it on example - let say there is a receiver that gets data in well defined format - 1004, 8-bit symbols are grouped in one frame. In every CLK cycle one 8-bit symbol appears on receiver input. The last four symbols in frame are sequence number, that helps the receiver to find boundaries of frames. So, useful data that should be forwarded to next module are 1000 symbols. But, these symbols are also grouped in 4 smaller subframes, 250 symbols each one. Subframes are aligned to bigger frame's boundary - 1st symbol of bigger frame is also first symbol of 1st subframe. I would like to filter out sequence symbols in big frame, forward encapsulated data to next module and set additional output signal that shows subframes' beginnings.

My fist idea was to build state machine that looks where are big frames boundaries. If it catches sync sequence few times, it goes to sync state. Then use 10-bit counter that counts every symbols. On counter values 0, 250, 500, 750 would be subframes' 1st symbols (that I can signalise to next module by additional output signal - call it StartOut), and on counter values 1000-1003 the next module should be disabled, to skip sync sequence. Unfortunately this solution is not so good - output signals Enable and StartOut are functions of 10 bits. There are some logic (including 10-bit comparators) that slows down output signals' maximum speed. It becomes more limited if big frame size increases, and 16-bit counter is needed.

Searching StackExchange I found this question: vhdl synthesis optimization: counters in statemachines.
There is shown an idea how to reduce output signal dependency, and make it a function of only one 1-bit signal. But it works rather with counting to one value. Here is a problem of one counter and few values that should be compared with it.

Do you have any idea how to improve speed in comparison counter with few constant values?


texts: Connecting varistor and surge arrester in series

texts:
I have a doubt about proper values of MOV and SAR when they are connected in series as suggested in Epcos app notes (see below Fig. 12). For the 230 VAC mains they recommends SAR of 470 or 600 V, but MOV specification is missing. In my current design I'm using 275 VAC MOVs that doesn't makes any problem but possibly also cannot protect the circuit in a proper way. It seems that MOVs voltage has to be cut in half (e.g. 140 VAC) to start protecting when input voltage goes 20% beyond nominal value. There is many guides how to select proper single MOV but without mentioning such connection in series. Any suggestion? I'm also wondering why SAR could be 470 or 600 V in this configuration - just to provide different threshold for ignition?
Thanks.


texts: Resistor placement for Zener diode for over voltage protection

texts:
I have searched in over voltage protection (like MOSFET.) I wanted to use a Zener diode in parallel so it won't dissipate power unless in over voltage protection, but its power is low so I read that I need a resistor to control the current passing through it.
I found people put the resistor in this shape:

This resistor will  dissipate power, so I thought if we can put resistor like this:

In this situation the resistor (R3) will only dissipate in case of over-voltage but in desired voltage current won't pass through zener so won't pass through the resistor.

Is the voltage going to the LED equal to source or to the Zener?
Is the new placement for the resistor right? If wrong, why?
Is there another placement for resistor if this doesn't work ?**


texts: How to autoregulate a TP4056 for maximum solar power extraction

texts:
I'm using a solar panel (6V - 600mA at peak power) to charge a Li-Ion (3.7V) battery using a TP4065. The TP4065 I'm using has this configuration:

Where the value of the resistor Rprog determines the charging current.

The issue is that the current the solar panel provides is proportional to the light it received and the only way to keep extracting the maximum power from the solar panel is to adjust the load to keep to solar panel voltage around 6V which in my case is controlled by reducing the charging current.

What would be the best circuit to automatically adjust the Rprog resistor to keep the TP4056 Vcc at a constant voltage of around 6V?

Here is an example of a solar panel IV curve showing the voltage where the maximum power is extracted.

Here is the charging characteristic of the TP4065

UPDATE 13-02-2015

The voltage a the PROG pin vary between 1V to 0.2V

My project will use an Arduino micro controller. I could use the Arduino to monitor the solar panel voltage and regulate the TP4056 current with the following circuit:

Rprog and Rarduino would be 600 ohms and the 100uF capacitor and Rarduino will act as a low pass filter for the Arduino analog out that output a 3.3V 500Hz PWM signal.

When digital out is 0V, the TP4056 will see a 1.2K resistor and behave normally. As we increase the analog out voltage, the voltage at Rprog will decrease which will decrease the current in the TP4056 PROG pin and finally reduce the battery charging current.

Does this solution can work?


texts: Water level indicator with PNP transistor

texts:
I wanted to create a circuit that Lit's up an LED when water level rises to a certain level.

I have created the following schematics following the https://www.electronicshub.org/water-level-alarm-using-555-timer/
However since the LED lit up even though there was no water i needed to add the R1 resistor.

simulate this circuit – Schematic created using CircuitLab

Now i want to do the opposite. I want the LED to not light up when both probes are connected with water and lit up only when water level drops.

For that i have created a following circuit swapping the BC546B (NPN) with BC556B (PNP) transistor.

simulate this circuit

However this lights the LED when the probes are not connected with water but even shorting them doesn't turn off the PNP transistor (that is LED is still glowing). Removing the R1 and path to ground from base of the PNP makes it glow dimly (it glows more when i hold the water probe) and connecting them then does turn off the PNP.

Why is that ? I thought i can turn off the PNP by applying a small amount of voltage to its base?

How can i fix my circuit so that it works ?

Ps. i have also tried with a darlington PNP transistor TIP 125 and it doesn't work


texts: The role of a transistor in a magnetostrictive oscillator circuit

texts:
Could someone please explain the role of the transistor in this circuit?
I have a feeling it has to do with the LC circuit but I'm not sure and don't understand completely.
The following is an image of the circuit (the transistor is n-type.
It is used in lots of sensors to detect and generate ultrasonic waves.


texts: Is the resistance in a DC Motor constant if the voltage is?

texts: Is resistance in a DC motor constant if both the load and voltage are constant as well?


texts:
What is the standard layout for a 4 layer PCB that everyone follows for a buck converter or similar? I was planning to go like this:

Signal
Vcc
GND
Signal

Since inductors and FETS are noisiest of all I was thinking of having them on the top layer. Second layer for Vcc, bottom layer with the gate signal, voltage feedback, current sense from and to the IC and other routes that are not possible on the top layer. Third would hold the GND plane with no routing. A reasonably large exposed layer on the first and fourth layer for the MOSFETs to dissipate heat. Would this be a bad idea?
Should I have the GND in the second layer to keep the path to GND the shortest? Frequency is 280 kHz with top mount devices. Can we use the second layer for routing other signals like the MOSFET gate?


texts: Connecting batteries in parallel to the existing batteries that are connected in series

texts:
I have 6 12V batteries all the same volt and same amp. I need 48V to use and I connected 4 batteries in series to get the 48V, but two extra batteries are just laying there doing nothing. I thought of adding them also to the system to use without increasing the volt. See the image on how they are connected.

If I connect the batteries as explained in the drawing would work?


texts: LED driver - current monitoring AC or DC side with Arduino

texts:
I have 2 LED strips connected in parallel to the same LED driver (driver is constant current + constant voltage). I have got an Arduino controlling a relay module that switches the lights on or off (on the ac side of the driver - INPUT).I know ideally it should be each strip with its driver, but I can't change that at the moment.

I want to monitor this system with a current transformer (current sensor) but I don't know which side should I monitor. If one of the modules switches off or gets damaged will the output of the driver stay constant even though the load has changed (I'm assuming it does, might be wrong????). What about the supply to the driver? If one of the modules goes off will the driver pull a smaller current from the mains?

These are the sensors I was thinking of using or something similar:

AC side

DC side

Thank you.


texts: Transistor Switch to Pull to Ground (Broadcast GPIO)

texts:
I have a Sonifex Net-log audio recording device.  It can be configured to begin recording on remote input.  From the manual:

  The remote inputs and output can be driven by 5V logic. The inputs are active low.  These can be set to momentary or latching action via the Remote Options screen.

The connection of the Net-Log has four such remote inputs and a common ground plus outputs (which I'm not going to use).  In momentary configuration, pulling an input pin to ground causes recording to start, releasing causes recording to end.

Consider the following diagram:

simulate this circuit – Schematic created using CircuitLab

Pressing SW1 causes recording to begin.

I have designed a CMOS logic circuit with various gates to decide when to record.  The final output stage is a 74HCT08N AND gate.  Originally I had planned to connect the input via a transistor to drive a reed switch to close the input pin to ground but I'm wondering if I can do without the switch part?

My question is, can I achieve this using a simple transistor?  I think this could be implemented as a simple transistor switch but I'm not sure as I don't think any current will flow as such?

Do you think this arrangement will work:

simulate this circuit


texts:
In High-Speed Digital Design, Dr. Johnson illustrates an example of calculating the output impedance of an IC (page 48.). He uses VOL of 0.15 V and VOH of 4.32 V (@ Vcc = 4.5 V) with an Io of 4 mA to compute a typical low state output resistance of 37 Ohm and 45 Ohm for the high state.

In both calculations the current was 4 mA. My question is, is this result only valid for a current draw of 4 mA?

How would I utilize this calcuation in the real world? For example, I'm using NC7WZ16 buffer but plan on putting a series/source terminator at the output. But before I decide on the value of the source resistor I need to know the output impedence of the chip. The datasheet lists this at a Vcc of 3V:

VOL (typ.) = 0.16V @ Io = 16mA. This gives as Rout as 10 Ohm. But, again, is this result only valid for Io of 16 mA? In a typical design today the inputs are very impedance and so I believe that the current draw will be minimal.

Similarly, for the high-state, the impedance is ((3-2.75)/16mA) = 15 Ohm. So does the output impedance change with current draw or does it stay the same and I can utilize the above results?


texts: Finding Op-Amp Output Resistance using Datasheet

texts:
I'm using this TL071 op-amp datasheet and I am trying to find the op-amp output impedance on the datasheet so I can calculate the output impedance when used in amplifier/peak detector circuit. Do I need to calculate the output impedance from one of the other characteristics on the data sheet or am I missing something?

Many thanks in advance!


texts: How does the length of a transformers core affect its properties?

texts:
I often read  mentions of a transformer core's  "cross-sectional area", of how it affects the transformers VA rating (although I can't find any formulas for that).  But I haven't found anything mentioning the length that the magnetic flux must travel.  Does this mean that both of the following cores are equivalent, other than heat dissipation?

How would the inductance, VA rating, and other properties compare between these two toroidal cores?


texts: Is power cycle reset different from reset pin reset?

texts:
I am using custom built arduino uno for a home automation project. Sometimes, the arduino locks up due to electrical noise or sparks in the ac lines. More details here.

I tried conducting some controlled tests to know more about this where I left the module powered up and tried my best to introduce as much noise as possible by turning on/off switches and turning fan regulator knobs. I also tried to zap the circuit using a gas lighter while the circuit was on. I made a setup which allowed me to make sparks jump on any part of the pcb that I wanted. I did this because I couldn't afford a esd simulating gun.

After all this, I was able to make my microcontroller hang up after torturing it for few minutes and I could repeat the hang up process. Success till this part.

Once my micro controller freezes, sometimes I am able to bring it back to normal process by pulling the reset pin LOW but mostly I can't. It's as if reset pin is not working at all. However I am able to bring it back to normal operation by power cycling it.

(Reset pin works fine otherwise when normal code execution is going on. Reset pin has a pullup and protection diode as recommended by atmega datasheet. Decoupling taken care of. Filter caps very close to power pins. Reset pin going LOW has been verified by an oscilloscope as well.)

Is power cycle reset different as compared to reset pin reset? Is this an expected behavior? Can I do something to ensure my reset pin always works in such conditions?


texts: Looking for robust reversible prototyping solutions

texts:
I've recently started making use of Arduino and Teensy microcontrollers to build various one-off pieces of equipment for my work in a neuroscience lab.  Often I find that, after a device has worked well for one project, it needs to be tweaked for the next project in small ways I hadn't anticipated.

My options then come down to:  (a) unsolder everything and re-build, (b) buy the same components again and re-build, or (c) build on a solderless protoboard like this Twin Industries product to start with, and just add/reroute the few connections when necessary.

Options (a) and (b) can get too time-consuming (TBH I'm not that great with a soldering iron). But with (c) I always seem to end up with something too fragile to be relied on (knock it once, and I have to hunt down the loose connection).

Does anyone know of a more robust solderless prototyping system?  I don't mind if my prototypes end up the size of a shoe boxes rather than cigarette packets, containing the electronic equivalent of Duplo rather than Lego. I'm just looking for something both flexible and robust. I've contemplated making a board that breaks out every Arduino pin to touchproof biomedical connectors but I'd need a way of interfacing small components too.  Are there better solutions out there already?


texts: Jacket diameter of coaxial cable : how to read those documentations?

texts:
Before anything: I am not an electrical engineer: I don't know very much coaxial cables (just the very basics). I need to do some orders of magnitude calculation of heat transport of typical coaxial cable designed for cryogenic systems, over a range of temperatures. I could use the heat transport properties given by the documentations but the problem is that they are usually given for a fixed couple of temperatures at the both ends of the wire. I need to have arbitrary ending temperatures for my purpose.

What I need is then to use the properties of the materials of inner and outter conductor, the property of the dielectric in between, properties of the jacket. In addition to that I need the diameter of those components. Then I will simply use Fourier Heat law to find what I need.

But I have some troubles to understand aspects of documentation.

For example consider the following:

https://www.tek-stock.com/ut-085-ss-ss/

What are the inner and outter diameter of the jacket ? I don't find it. Is it because the jacket is not provided with the rest ?

Consider also this one:

https://www.lakeshore.com/products/categories/specification/temperature-products/cryogenic-accessories/cryogenic-cable

In "Jacket outer dimension", for type C, they give 0.7874 mm × 1.016 mm: what does that mean ? I would expect a diameter (the outer diameter of the jacket). Here they give me a surface as if it was a square.

For type SR the shield diameter and Jacket outer dimension are the same. What does that even mean ? The jacket must have a bigger diameter than the shield.

You see my point: it is probably very basic questions to understand how to read those documentations.


texts:
I was reading

  PLEASE BE AWARE THAT... the moc output MUST BE between the triac pins
  A2 and G it is never written in any datasheets but it MUST be so or
  your triac won't commute ...

https://www.edaboard.com/showthread.php?155997-Using-an-opto-triac-(MOC3020)-to-control-a-mains-lamp

Can anyone confirm this is the case, and also if anything bad happens if I put the MOC between triac pins A1 and G ?

edit

And lastly, any safe way to make the correct wirings on my existing badly wired PCB (meaning MOC is now between pins A1 and G, would like to make it so that it is between A2 and G) ?


texts: How to explain the advantage of Schmitt trigger over comparator for pulse conditioning?

texts:
Above is the unshaped input pulse train. Red line is the set point for the comparator.

I see many pulse conditioning and sharpening circuits use Schmitt triggers instead of comparators.

Imagine the input pulse train is not sharp enough so we need to make it sharper. There are some applications in industry where you need sharp pulses to count frequencies. My question is:

Why not only to use a comparator? Is that because rising and falling edges are sharper in case of Schmitt trigger? Could one explain it in an illustrative manner?


texts: Justification of the choice of colours in monochrome displays

texts:
Why for monochrome displays was chosen green, gray or yellow(amber) colors?

Any reason like red LEDs because it simpler in production.

upd:
Amber for reducing eye strain.
Gray for white imitation.

but why greeen?


texts:
For a school project (Wireless Charging), I have to filter out and display the communication signal (2KHz) between transmitter and receiver from the Power Signal (100KHz). For this I have set up the circuit in ltSpice. I have created an ASK signal (product) as input to the MOSFET driver. Is it correct to select the ASK signal as the input signal?
Should I put it on the SOURCE input of the mosfets.
Unfortunately, I do not get the desired transmission signal on the receiver side. Can anyone help me?[![enter image description here]enter image description here


texts: Transistor absolute maximum Collector-Base voltage more than Collector-Emitter voltage

texts:
In the Microsemi 2N918 NPN RF transistor datasheet, the absolute maximum ratings are given as:

The fact that \$V_{CBO}\$ is so much greater than \$V_{CEO}\$ has me confused. Additionally, the datasheet specifies \$V_{CB}\$ at 25V and 30V for certain parameter test conditions later in the document.

My question is: for a BJT, what in the construction/manufacturing process makes \$V_{CBO} > V_{CEO}\$?


texts: TI RF solution - MSP43x+CC1100 vs. CC1110, toolchain

texts:
I'm looking for low-power RF solution working in sub 1GHz band (868MHz, battery powered, mostly sleeping).  Originally I considered AVR with Digi Xbee 868LP module but doing deeper research I found TI RF solutions. TI offers open source SimpliciTI protocol implementing star wireless topology. Which is not as originally supposed mesh topology but it's simpler and has shorter packet time-to-delivery than multi-hop network (advantage for MODBUS). 868MHz range should be sufficient without multi-hopping and in the worst case even range extender is available, price is convenient as well. RF packet sniffer seems as good debugging tool, completely missing in Xbee.

TI options:

MCU MSP43x + RF module CC1100

MSP is ARM Cortex M3/M4 MCU which offers many variants (including more friendly non-QFN socket) as it is standalone MCU. A certified module CC1100 might be used, e.g. Anaren, to shorten time-to-market and avoid RF issues. Seems besides paid (for-free as crippleware) development tools (CCStudio, IAR) does exist GNU GCC for MSP. It should implement in-system debugging via GDB with MSP-FET. There is also open source Energia project, but authors present it as equivalent of Arduino IDE (which is useless for serious devel so I doubt about Energia).

CC1110 MCU+RF (SimpleLink)

There is not ARM but 8051 core. Seems as low cost solution to implement remote sonsors and control based on SimpliciIT. TI offers evaluation boards including CCDebugger but I cannot find info if does exist a free toolchain. Bundled with crippled IAR EW8051 IDE. Probably missing EnergyTrace power consumption monitor (only MSP feature).

CC1310

Similar as CC1110 but Cortex M3. I'm afraid it's slideware.

Does anybody get working CC1110 with GCC including full in-system debugging ? Are my findings correct?


texts: Why does signed (2's complement) binary multiplication have different procedure than unsigned?

texts:
The 2's complement binary multiplication does not have same procedure as unsigned if the both operands do not have the same sign. What is the logic behind that?

Does special consideration apply to division also when we carry out division with 2's complement numbers?


texts: Choice of P or N channel device as active load

texts:
Essentially, in our electronics textbook Microelectronics by Sedra/Smith, when beginning to discuss IC amplifier design, the topic of active loading comes up before cascoding. Throughout the text, for example, when using an NMOS common source amplifier, it will be biased by an active load PMOS, but the reason for this is never explained. When researching myself, it seems that it doesn’t really matter, as you can always adjust voltages to make a device work, but I must be missing something.
Why is it so ubiquitous to see a PMOS active load in an NMOS common source amp?
I’m assuming it has something to do with the positive power rail and avoiding gain being too high from cascoding, but maybe I’m way off base.


texts: Looking for replacement or datasheet of this component

texts:
I have a burned diode. (I fortunately found an exact same component in the circuit elsewhere to take a photo.) It says 132Y or B2Y

Could you please give me a hint what can I use as replacement?


texts:
I've seen a Verilog example that assigns values to an array as follows :
array = '{'{0,1,2,3},'{4,5,6,7},'{8,9,10,11}};

What's the purpose of the apostrophe (') ?
How will this be any different ?
array = {{0,1,2,3},{4,5,6,7},{8,9,10,11}};


texts: Can logic analyser show high impedance state?

texts: Quick question: are there logic analysers that can show us high impedance state in circuit? I could only find information about different voltage levels for TTL and CMOS, but couldn't find clean information about high impedance.


texts:
Hi! I came across this question in lab, and it's been several years since I last done analog circuits. The voltage gain here in this op-amp should be 0.707 (-3db cut-off), and it asks us to find the capacitance. The way I see it is

V_in/(1000 + 1/jwC) = -V_out/10000

And after performing some simple arithmetic, we will be able to find the capacitance. However, the answer that I'm getting is wrong, so could anyone please show me the workings of how this should be done.

Much thanks fellas!


texts: I have a question about H-bridge power supply: my motor works with 24DC. Do I have to use a switching power supply, or can I use a 24AC with a rectifier and capacitor?


texts: How to determine the physical location on a RS-485 daisy chain / bus topology?

texts:
I am trying to build a "daisy chain" using several Arduinos and MAX485 transceivers. All boards have a temperature sensor attached to it. A 9V battery supply all boards in the chain.

I am trying to figure out a way to identify the physical location of the different boards in the daisy chain, for example, boardA = first, boardD = second, boardB = third, etc.

I could do this manually by being aware where I connect each board in the line. However, this is prone to human error and I want to do this automatically. Besides, I will like to take boards randomly to build networks whenever and wherever I want.

In order to identify the boards in the network I could create a query loop in the master board to call all possible names and get an answer of those boards connected. What I am looking for is also an answer of where they are located in the network.

I was thinking to measure voltage/current drop as an indicator of how close/far they are from the master. However, I am not sure if the drop is big enough or the ADC in the Arduino is accurate enough.

I guess someone has thought about this before, maybe there even are ready-made chips for this. I am not an Electronic Engineer, sorry for my limited knowledge.

Edit, 2018-10-14

More clarification; say that you have the following example:

All the slave boards are set to “listen” mode and wait to be called by the master. The master run a query loop to identify which slaves are on the bus. It asks for A,B,C,D,E, etc. The slaves will verify the call of the master. For this to work, I will have to assign an unique name/address in software to each slave, which is totally fine.

What I want to avoid is to check the name of each slave when I am placing them in the field. Therefore the need to figure out their relative position in the bus line with respect to the master and the other slave boards.

Is this something similar Maxim DS28EA00? Note that it is not only temperature that I am interested. I use temperature sensors as my proof of concept. I could used it to measure pressure, acceleration, etc.

@Transitor
In this case daisy chain = party line or bus topology. I don’t know if I can connect the RS-485 in series. If so, could I collect the name of each device as the data goes across them? This has the disadvantage that if one slave board dies, the rest of the line does too.

TI RS-485 Design Guide

@stark
Can you elaborate more the digital pin idea? Note that all boards are separated between 1-3 meters.

@Andy aka
Can you elaborate more? Could this work in bus topology?

@TimWescott
It is a bus topology. Maybe I used the daisy chain term wrong? Is it possible to do a true daisy chain with RS-485?


texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to get a phototransistor to saturate a BJT so that when a small amount of light is present, the BJT is on. At the moment, there needs to be a lot more light than I would like, so I've been looking for a way to change how much light I need. One thing I've tried is to put two of the phototransistors in series along with a resistor, and found that by pointing one away from the light, I can get a large enough voltage across one of them to saturate the BJT with a small enough amount of light. However, put the BJT B-E in parallel, and the voltage jumps down to below what is needed. I've tried using a resistor in series with the B-E junction, but it still requires the same amount of light as before.
Any suggestions?
Sorry about the poor schematic. I couldn't find any phototransistors, so I used BJT + arrows instead.
Also, it doesn't need to be a bjt, I could get something else if it would work better.


texts:
I'm planning to build something like this: http://www.youtube.com/watch?v=3RGcYiV4hEE
But with an Arduino replaced with the easyUSB chip. Is there any simple solution for that.

Here there is an ADXL335 accelerometer which has analogue outputs and the data is being sent via an Xbee module. Essentially there is no microcontrollers used explicitly at the transmitter's end. I'm expecting this should be possible by just a correct configuration of the Xbee, reading the data on the analogue pins (say D0 to D2) and just setting the RTS pin to high.

On the receiver though, the Xbee, properly configured, is attached to an Arduino Uno board. Now I'm confused. Shall I try and write a program for the Arduino to read the data from the Xbee using the serial communication and then write it to the USB port on the computer or can I use the Arduino board in reset mode as just a serial to USB convertor and do everything on the computer? I'm expecting the latter should be easier, if possible!

Many thanks in advance,


texts: Why are laptops grounded to earth via 1E6 ohm resistance and desktops not?

texts:
I measured a few laptop AC-to-DC adapters.

1E6 ohm between GND pin (goes into the laptop) and earth prong (into the wall).

Desktops are grounded directly to earth: 0 ohm.

Why this difference?


texts: What is the difference between system clock and peripheral clock in case of arm Cortex M4 architecture?

texts: System clock/core clock is the clock that drives the CPU. I understand that different internal peripherals use the oscillators. How do both differ from each other?


texts: Expanding Range Of Analog Values From Temperature Sensor

texts:
I'm trying to build a temperature controlled relay module with an ATtiny45 ( Arduino UNO R3 as ISP ) and a NXP KTY81-222 Temperature Sensor.

The temperature range i want to monitor is 20°C to 30°C.

( data sheet -> http://www.produktinfo.conrad.com/datenblaetter/150000-174999/153653-da-01-en-TEMPERATUR_SENSOR_KTY10_7_KTY81_222.pdf )

My circuit layout looks like this =
( I'm using the Arduino UNO R3 for debugging )

**notice that i've also tryed to "swap" the 1K resistor and the Sensor position to invert the output.

*and the arduino board ->

A0 is the Analog Input 0 of the Arduino.
5V is directly plugged into the 5V Output pin of the arduino.

( later it would be the same on the ATtiny45 using some batteries )

( VCC can be 2.7V to 5.5V )

I've used a household digital thermometer to compare the values from the analog input with the measured °C values.

this is a quick measure table =

Analog -> °C

687 to 690 -> 24.4°C to 25.1°C

707 to 708 -> 36.2°C to 36.5°C

as you can see i have a range from about 20 Analog units that represents a range from about 10°C units.

so what i actually want is to "grow" the range of the analog units to about 200 Analog units for 10°C units range.
the solution should be a good to handle value range, so i can tell the µC to power the relay if temperature is under 24°C, and close the relay if the temperature is over 28°C.

I want 20°C to be an analog value from about 500 and 30°C to be about 700. ( this "range from 500 to 700 would be good enough for me.

i hope i could explain my question well for my bad englisch.


texts: DS3232M Skips seconds when writing to SRAM

texts: I'm using a DS3232M that works great for keeping track of the time until I try to write to the SRAM on the chip. When I use the SRAM it slows the updates of the seconds register or stops them all together. I'm writing 18 bytes to the SRAM once per second and the data is not overwriting the timekeeping registers, but it does seem to be preventing the timekeeping registers from updating. As a side note the 1 Hz output pin is outputting a 1 Hz square wave with a 50% duty cycle when I'm not writing to the SRAM, but when I start writing to the SRAM the duty cycle drops to 33%. Why can't I write to the on board SRAM and keep good time?


texts: Do I have to route VCC and GND signals on PCB if planes are used

texts: I am designi a board where I have a VCC plane and a GND plane.I have decoupling capcitors and was wondering if I should manually connect these decoupling capacitors with a trace since I plan to have a VCC and GND plane? Can I just drop vias directly to the planes at the end?


texts: Does the unit step response not affect the transfer function?

texts: I am still confused, this question says that this figure shows three unit step responses and was asked to find the transfer function. Doesn't the input step responses only affect the output? So to look for the transfer function does not matter how many step unit response?


texts: Power & Reset in momentary switch in analog circuit

texts:
So I am designing a circuit and wanted to implement both power and reset in one momentary switch. What I mean is, if the switch is pressed, it sends a reset signal (4.5v), but if it is held for x seconds, it powers on/off. I figure I might need a 555 timer.
How to do this?

EDIT: Some specifics:

One press when the circuit is off turns it on. It is to reset an IC (so HIGH at 4.5v).


texts: Proximity sensor to measure object presence, speed and orientation

texts:
As depicted in the image, I'm looking for sensors to incorporate in a project where I have to detect object presence in short range (10-100mm), speed (passing from one sensor location to another, 0.1-10m/s), distance and orientation (just roughly). Space is fairly restricted, and I only have the option to detect object from one side. After a fair bit of research, it seems the only option I have is an emitter-and-receiver type of proximity sensor.
LIDARs draws too much power and only good in the long range. It might be an overkill for this purpose, and they also fall in a price range that I can't afford (USD 100+).  Ultrasonic sensors are cheap but may fail detecting object distance if the orientation exceeds a certain angle, as shown in an experiment carried out in this video (VL53L0X vs HC-SR04 experiment).
VCSEL based Time-of-Flight sensor (VL53L1X ToF Distance Sensor) and IR Range Finder (Sharp GP2Y0A21YK0F IR Range Finder (Distance) Sensor) are affordable (USD 10-30) and accurate enough in short distance, and don't seem to be affected by color and orientation of the object. All is nice if the object only moves slow enough.
Detecting object presence at lower speed is not an issue, and so is reading its distance. Orientation can be calculated by changes in distance over time.  But ToF samples only up to 50-60Hz, and IR Range Finder sensor has at update period of just 40ms (or 25Hz sampling rate).  If the object is moving at its maximum speed of 10m/s (which is really not all that fast), a ToF sensor sampling at 50Hz (or 0.02s period) can only trigger a reading if the objects are at least 200mm apart.
Am I looking at the wrong sensors for my application? Or have I misinterpret the specs - as I would expect sensors taking advantage of the speed of light should operate at least some few orders faster than ultrasonic sensors.


texts: What is Platform Bus in Embedded Systems?

texts:
I would want to know what is the Platform bus in SoC . I have seen some device driver implementation in Linux kernel where drivers are registered with platform bus or rather should i say these all called platform driver where devices sits on platform bus.

But what are the platform bus?

Is Amba bus platform bus for ARM bus SoC's?


texts: Temperature it's not read well on microcontroller

texts:
I'm trying to build a thermometer using the ATMega164 microcontroller, but my problem is that it's not displaying temperatures correctly over 32 degrees, what it's the problem? This is how the setup looks like:
And this is my code for the while loop:
while (1)
      {
      // Place your code here
      lcd_clear();
      res=read_adc(0);
      temperature=(res*453)>>10;
      sprintf(buffer, "%f", temperature);

      lcd_puts(buffer);
      delay_ms(1500);

      }
}

ADC Clock frequency: 625.000 kHz
ADC Voltage Reference: 1.1V, cap. on AREF


texts:
Have I obtained the correct simplified transfer function for this RLC circuit?
I am trying to obtain the transfer function for the following RCL circuit. However, the response of the TF that I obtain doesn't correlate to the response of the circuit itself when I simulate it. Please see below:

Therefore, I have obviously done something wrong. I have spent a good couples of days and plenty of scrap papers trying to see where I have missed something, but I keep on arriving at the same answer.
So, in order to save myself the headache of repeatedly doing the same thing only to obtain the same outcome, I've decided to put my dilemma to the community!
Below is my working out from the mid-way point to the end result and if anyone can spot or point out what I have missed, I would really appreciate it.
So the starting expression is:
$$ I_2(s)((\frac{C_2Ls^3+C_2(R_1+R_2)s+1}{C_2Ls^2+C_2R_1s})(\frac{C_1Ls^2+C_1R_1s+1}{C_1s}))-I_2(s)(Ls+R_1)=E_i(s)\tag{1} $$
$$ I_2(s)((\frac{C_2Ls^3+C_2(R_1+R_2)s+1}{C_2Ls^2+C_2R_1s})(\frac{C_1Ls^2+C_1R_1s+1}{C_1s})-(Ls+R_1))=E_i(s) $$
$$ I_2(s)(\frac{(C_2Ls^2+C_2(R_1+R_2)s+1)({C_1Ls^2+C_1R_1s+1})}{(C_2Ls^2+C_2R_1s)(C_1s)})-(Ls+R_1))=E_i(s) $$
$$ I_2(s)(\frac{(C_2Ls^2+C_2(R_1+R_2)s+1)(C_1Ls^2+C_1R_1s+1)-(C_1C_2Ls^3+C_1C_2R_1s^2)(Ls+R_1)}{(C_1C_2Ls^3+C_1C_2R_1s^2)})\tag{2}$$
Expanding the numerator for the positive term
$$ (C_2Ls^2+C_2(R1+R2)s+1)(C_1Ls^2+C_1R_1s+1)$$
$$ (C_2Ls^2)(C_1Ls^2) + (C_2Ls^2)(C_1R_1s) + (C_2Ls^2)(1) + (C_2(R_1+R_2)s)(C_1Ls^2) + (C_2(R_1+R_2)s)(C_1R_1s)+(C_2(R_1+R_2)s)(1)) + (1)(C_1Ls^2) + (1)(C_1R_1s) + (1)(1) $$
$$ (C_1C_2L^2s^4) + (C_1C_2R_1Ls^3) + (C_2Ls^2) + (C_1C_2L(R_1+R_2)s^3) + (C_1C_2R_1(R_1+R_2)s^2) + C_2(R_1+R_2)s + (C_1Ls^2) + (C_1R_1s) + 1 $$
$$ C_1C_2L^2s^4 + C_1C_2R_1Ls^3 + C_2Ls^2 + C_1C_2L(R_1+R_2)s^3 + C_1C_2R_1(R_1+R_2)s^2 + C_2(R_1+R_2)s + C_1Ls^2 + C_1R_1s + 1 $$
$$ C_1C_2L^2s^4 + C_1C_2R_1Ls^3 + C_2Ls^2 + C_1C_2R_1Ls^3 + C_1C_2R_2Ls^3 + C_1C_2R_1^2s^2 + C_1C_2R_1R_2s^2 + C_2(R_1+R_2)s + C_1Ls^2 + C_1R_1s + 1 $$
$$ C_1C_2L^2s^4 + 2C_1C_2R_1Ls^3 + C_2Ls^2 + C_1C_2R_2Ls^3 + C_1C_2R_1^2s^2 + C_1C_2R_1R_2s^2 + C_2(R_1+R_2)s + C_1Ls^2 + C_1R_1s + 1 \tag{3}$$
Expanding the numerator for the negative term
$$ -(C_1C_2Ls^3+C_1C_2R_1s^2)(Ls+R_1)$$
$$ -((C_1C_2Ls^3)(Ls)+(C_1C_2Ls^3)(R_1)+(C_1C_2R_1s^2)(Ls)+(C_1C_2R_1s^2)(R_1))$$
$$ -(C_1C_2L^2s^4 + C_1C_2R_1Ls^3 + C_1C_2R_1Ls^3 + C_1C_2R_1^2s^2)\tag{4}$$
Subtracting \$(4)\$ from \$(3)\$
$$ C_1C_2L^2s^4 + 2C_1C_2R_1Ls^3 + C_2Ls^2 + C_1C_2R_2Ls^3 + C_1C_2R_1^2s^2 + C_1C_2R_1R_2s^2 + C_2(R_1+R_2)s + C_1Ls^2 + C_1R_1s + 1 -C_1C_2L^2s^4 - C_1C_2R_1Ls^3 - C_1C_2R_1Ls^3 - C_1C_2R_1^2s^2 $$
$$ C_1C_2L^2s^4 + 2C_1C_2R_1Ls^3 + C_2Ls^2 + C_1C_2R_2Ls^3 + C_1C_2R_1^2s^2 + C_1C_2R_1R_2s^2 + C_2(R_1+R_2)s + C_1Ls^2 + C_1R_1s + 1 - C_1C_2L^2s^4 - 2C_1C_2R_1Ls^3 - C_1C_2R_1^2s^2 $$
$$ C_2Ls^2 + C_1C_2R_2Ls^3 + C_1C_2R_1R_2s^2 + C_2(R_1+R_2)s + C_1Ls^2 + C_1R_1s + 1 $$
Combining like terms
$$ C_1C_2R_2Ls^3 + (C_1(C_2R_1R_2 + L)+ C_2L)s^2 + (C_2(R_1+R_2) + C_1R_1)s + 1 $$
Therefore, I get
$$ I_2(s)\frac{C_1C_2R_2Ls^3 + (C_1(C_2R_1R_2 + L)+ C_2L)s^2 + (C_2(R_1+R_2) + C_1R_1)s + 1}{C_1C_2Ls^3+C_1C_2R_1s^2} = E_i(s)$$
And I arrive at this final transfer function each and every time:
$$ \frac{I_2(s)}{E_i(s)}=\frac{C_1C_2Ls^3+C_1C_2R_1s^2}{C_1C_2R_2Ls^3 + (C_1(C_2R_1R_2 + L)+ C_2L)s^2 + (C_2(R_1+R_2) + C_1R_1)s + 1} \tag{5}$$
Therefore, if anyone has noted any step(s) that I might have missed, I would really appreciate it, if you could please point it out :)


texts: Differences & Similarities between I2C & SPI Analyzers

texts: I am learning about I2C and SPI analyzers and want to know about the differences between the two. What is the difference between their functionality and what are the similarities in these analyzers, if any?


texts:
I'm using the following circuit for a half wave rectifier. I have the following values:
R1 and R2 = 1K,
Vin: 400mv peak to peak, 60 Hz (it's a sine plus noise)
D1 and D2: 1N4007
Op amp: LM 741. Positive supply for op-amp is 5V and ground for negative voltage.

The circuit works as expected with these values (it preserves the positive parts of the input). However, when I add a capacitor or an RC circuit as the load to the Vout node, the output goes to zero, rather than detecting the peaks. I have no idea why this is happening.
I know that it's not a good idea to have the op-amp negative supply connected to ground, but trying it with -12v didn't make any difference. Any comment on how I can detect the peaks is highly appreciated!


texts: Why I had to add buffer to this circuit?

texts: So before adding an op-amp buffer between sensor and the non-inverting input of a schmitt trigger, if the output of the sensor was for example 0.4V, the moment I connected it to the non-inverting input somehow the output of the sensor would suddenly become about 2V. Ater I added the buffer the problem was solved and the output of the sensor didn’t change anymore. So I have done some reading on buffers applications but can’t really understand what’s going on here and why buffer was the solution.


texts: Understanding Solid state relay specifications

texts:
I've been looking for a solid state relay that can switch 240V from a 3.3V signal.
Looking at DigiKey, with a very large selection, I'm not sure how to filter my search (screenshot attached). How do I interpret the "Voltage Input" and "Voltage Load" criteria compared to the coil and switching voltage for regular relay ? (screenshot attached)
The names seem pretty self explanatory but I'm surprised there aren't any 3V DC controlled SSRs - hence the uncertainty


texts: controlling some RGB LED modules with HD74HC254P and 74HC595N ICs

texts:
I got some LED modules dismantled from old festival screen. It would be nice to get them working, but I can't find any info about them, neither I have any idea how to controll them. AFAIK they are made to be used in series on some bus, and each module has level shifter and 4 octal bus transceivers.

Each module is 16x16 pixels, 1 pixels is 4 LEDs (RRGB). But I can't figure out how to drive this thing. Each module is internally splitted into two 16x8 pixels module and each of these has 6 ICs (4x HD74HC245P (octal bus transceiver), HD74HC04P(hex inverter) and 74HC595N(shift register)).
There are also 12-pin connectors (one for in, one for out that connects to the next module, propably made for bunch of modules in series), 1 is GND, the rest 11 are data. It has only label saying P/N 5ml0341122 (which was not found by Google) and "KS-341 Ver1.2" written on PCB

I was not able to find any documentation to this on the internet.  Is there anybody who knows something about these modules?
Thanks.
Some pictures of them: https://photos.app.goo.gl/PH6HjkzokVJ7ovn49

//EDIT: I started to peel off the rubber that covers the LEDs side of PCB. There is one TB62705C for every 8 LEDs. Still had no idea how to drive these, but I think I'm getting close.


texts:
please explain

How is 0.22 dB/km equal to 0.0507 km^(-1)

I tried doing 10 log x = its value in dB but it doesn't work here


texts: If I flick the light switch on and off will it damage the light?

texts: Ive heard that when you flick the light switch on and off repeatedly it damages the bulb.  I know this is certainly not true for LED bulbs,  but Im wondering if and how it damages other kinds of bulbs.  I know that light bulbs run off of ac current so they are turning on and off 120 times a second so I find it hard to believe that this would damage them.


texts: Can i use TL082 in a single supply configuration without any problems?

texts:
I am trying to use this op amp to work with single supply, I know that it is more recommended to go on with a near rail to rail option such as LM324 but I cannot take that route. I've tried to make a simulation on Proteus in its single supply configuration as a non inverting amplifier but i got this weird result on the output. Is this problem related to my interpretation of single supply working mode or is it on Proteus?.

I modified the simulation to work with 30 V in supply pin however i still got an odd result and is negative. How is this possible?. I doubt that you can get negative voltages using positive supplies.


texts: How to get sub-meter or centimeter GPS accuracy?

texts:
I'm thinking about building a gps system for a tractor.
The gps receiver can be placed on the roof of the tractor to minimize interference.
Regular GPS receivers are accurate upto "a few meters". (https://www.adafruit.com/products/746)
I found you can correct your position with a base station. (RTK)

I have seen the Starfire gps receiver getting a good precision (a few cm i think) without basestation. I wonder how they work.

Are there other ways to get a more accurate position?


texts: Finding the current trough resistor in a closed mesh

texts:
In a closed mesh we have:

simulate this circuit – Schematic created using CircuitLab

  The question is to determine the current through the 2nd resistor \$\text{I}_x\$.

My work:

I think of two methodes:

Because the currents that flow into a node must add up to zero, we know that:

$$\text{I}_{\text{R}_1}+\text{I}_x=0=10\cdot10^{-3}+\text{I}_x\space\Longleftrightarrow\space\text{I}_x=-10\cdot10^{-3}\space\text{A}\tag1$$

The voltage across the two resistors must add up to \$10+\left(-5\right)=5\space\text{V}\$, and I lose \$10\cdot10^{-3}\cdot1000=10\space\text{V}\$ across \$\text{R}_1\$ so the thing I've left is \$5-10=-5\space\text{V}\$, so \$\text{I}_x=-\frac{-5}{1000}=\frac{1}{200}=5\space\text{mA}\$

Which of my methods is right?


texts: Difference between the Kinect and PrimeSensor?

texts:
I'm trying to determine if the Kinect or the PrimeSensor is right for general purpose hobbyist work (X10 light control, relay activation, etc).

Does anyone know the difference?


texts:
I am working with a STM32 eval-board from STMicro which includes a ARM Cortex-M4 processor. I need a LUT for cosinus and sinus (read-only variables). I need to manage my RAM memory therefore I want to store these LUT in flash memory.

First: is it better to create a interpolate computation of cosinus/sinus or the FLASH reading is fast enough?

Secondly, how to put the variables in FLASH memory. ST provides some examples, but maybe, for my problem I just need to declare the LUT variables as static const and it will be like code?


texts:
I have a low voltage Marx generator which is connected to a coil inductor, eventually forming an LC oscillator. I want to find a way to switch the circuit on, but because the voltage is low I cannot use spark gaps.

I have studied quite a lot lately and I am thinking of either using a triac driven by an optocoupler, or using a solid state relay. My problem is that I don't think there are any optocouplers that can withstand 5-8 Amperes.

What is your opinion? Is an SSR a better solution?


texts: ESD strike on exposed circuit ground pin

texts:
I've designed a circuit for a battery operated device which has a USB connector externally exposed for charging and data transfer. It is a non-standard, dockable USB connector with no shield connection available and the entire circuit is housed in a plastic casing with no chassis / protective earth possibility, something like the image below:

For ESD protection,I've followed almost the exact design recommendation provided here: http://www.semtech.com/images/promo/Protecting_USB_Ports_from_ESD_Damage.pdf

I can visualize the current path when Vbus, D+ or D- gets hit by a positive or negative ESD pulse i.e. steering diodes forward conduct for negative pulse or divert to the central TVS for positive pulse, please correct if my understanding is off.

However, I'm not sure what would happen if the exposed GND pin itself receives the zap.

Questions:

Will a negative ESD strike on GND pin have the same effect as a positive pulse on Vbus, i.e. break-down of the central avalanche TVS leading to clamping?
In case of a positive ESD strike on GND, will the steering diodes and/or the central TVS forward conduct and pass the entire energy (minus 1 diode Vf drop,if that matters at all) to the rest of the circuit, thereby wrecking havoc!? I tried to depict the situation below:

(Image modified from link cited above)

Solutions that I'm considering:

Disconnect Vbus from the central TVS and introduce a stand-alone bidirectional TVS between Vbus and GND with subsequent reverse voltage protection for the rest of the circuit (to tolerate -Vclamp of the bi-dir TVS). It still may not prevent the steering diodes from conducting, plus there are other unidirectional TVS diodes shunting to GND on other exposed IO pins,which may also forward conduct.
Introduce a ferrite bead between the exposed USB GND and circuit GND for whatever meager impedance it may provide!

Any suggestions / insight is welcome, thank you!

P.S:

Since circuit can draw power from Vbus, series resistors cannot be added in the Vbus-GND loop
Planned test as per IEC 61000-4-2, Level 4 (8/15kV contact/air discharge). Device will be operating on battery power during testing with no USB cable connected,hence all pins would be easily accessible for ESD strikes.


texts: Wiring a 28 segment LED bargraph (to an Arduino)

texts:
I need to control a Barmeter 28 led bargraph via an arduino (Mega). I believe I have found the details of the component here:

http://www.barmeter.com/download/bl28-3005sk04y.pdf

(BL28-3005SK04Y)

I have previously used a SparkFun LED Driver Breakout (TLC5940) to drive animations on smaller bargraphs with each segment having its own anode/cathode pins via the Mega. (This board is still available if required)

But the diagram for this has got me flummoxed. I have rudementary knowledge of electronics, but my strength is in software, and I have no idea how this should be hooked up.

EDIT:
I am using the Y80, and need animations that will require all segemnts to appear lit at once.


texts:
In a motor where both the field and armature are wound there are at least two possible control scenarios.

The field winding can be excited with constant current and the armature voltage controlled, this is similar to a common permanent magnet DC motor. There is back EMF generated at the armature.

Alternatively, the armature can be excited with constant current and the field winding controlled. Apparently this configuration allows the torque on the motor to be controlled with a small amount of power at the field winding (and high current at the armature) why does this contrast with the original scenario? Finally, is there any back EMF in the field winding?


texts: What does the COM do on a DC/DC converter?

texts:
I got one of these DC/DC convert chips thats supposed to give a -25/25 V voltage output.

My "RGZ" model seems to be outputting -50/50 V and getting toasty.

I'm not sure what the COM is supposed to be connected to. I thought it was the "common" ground and should be connected to GND but my chip still ain't giving the correct voltage.

I got -VIN at (-5V), +VIN at +5V. What's COM and where do I connect it?

http://www.mouser.com/ds/2/468/RJZ_RGZ-318051.pdf


texts: P9842AB chip data sheet or identification

texts:
I found this chip whilst looking through some old electronics parts I've been left, does anyone know what it is? I am very new to electronics and a cursory Google gives only opertunities to buy more, no data sheets.

The writing on the top says:
F P9842AB
CD4528BCN

With the first "f" being stylised as if it's a brand.

Here is a picture:


texts:
Having read through this post I tried an experiment.

I connected a  Extech sound level calibrator to a Type 4189 microphone. The output sensitivity of the microphone is

50 mV/Pa,-26 dB ± 1.5 dB re 1 V/Pa

This microphone is connected to a Type 2671 preamp. Using a BNC 50 ohm cable the preamp is connected to a signal conditioning amplifier through a 50 Ohm BNC-BNC cable. The output from the amplified is connected to a standard oscilloscope.

The calibrator generates a consistent 1 kHz, 94dB SPL sound. The calibrator was recently calibrated, so the output is assumed to be the standard.

The gain at the signal conditioning amplifier is 100mV/unit.

The Vpp measured at the oscilloscope was 16.2 Vpp. Converting that to Vrms,

Vrms = 16.2/2.828 = 5.72843

Calculating for dBrms = 20*log10(5.72843/0.05012) = 41.1605

Since the gain at the signal conditioner is 100 mV/unit. the dB value is -20 dB.

For dB SPL = 41.1606+94-26-20 = 89.1605.

Would I be wrong in expecting this to have amounted to 94 dB SPL instead? If so, why the discrepancy ? what am I missing?


texts: position control mode of industrial servo motor

texts: I have searched alot about industrial servo motors and their application but the problem is about the pulse command used in position control mode, can I use a 555 timer for the generation of such pulses? Secondly what are the variables affected by the pulse width? Lastly what is the relation between number of pulses and the step angles of the servo motor shaft? I'm using the ASDA-A2 servo drive with 20-bit encoder resolution. http://www.delta.com.tw/product/em/download/download_main.asp?act=3&pid=2&cid=1&tpid=1 for manual


texts: reduce 120v ac supply to 100v without external transformer/device

texts:
1) I need to reduce 120v AC supply to 100v for a japanese piece of equipment which has a AC transformer inside rated at 100v.
There is only one primary (100v AC) and one secondary (30v AC) winding on the 100v transformer.
Device pulls only 4 amps.
The fix has to be internal since it gets moved around a lot.
There isn't very much room inside either.
2) I hesitate to run 100v transformer on 120v AC for any long period.
Am I being overly cautious?


texts: I am trying to understand how my lock-in Stanford RS830 works and therefore I am going trhough the manual. There is however one thing I cannot understand: whyever should I use a minimum dynamical range? For instance, if I set sensitivity to 50uV, I could set dynamical range 37dB, eventhough the instrument can work with a dynamical reserve of 100dB


texts:
I have found this schematic and am confused about the transistor and the diode. I know that the phone voltage is around 3V and the PIC voltage is 5v, and it's a level shifting circuit.

My questions :

Does the transistor have a value like resistor-ohm or like capacitor-farad? I know that it's NPN. Before this, I went to buy and said just NPN but they asking about the code (like BC548), but what if they don't have BC548? What else should I say besides NPN?
Why using a zener with value 3.3V? How can I calculate that value?


texts: How to double the power supplied to an electric motor?

texts:
Need some help here:
Assuming I need to power a toy motor with a 3V battery...
1. Is there any way for me to generate more power to the motor, at the cost of duration? (Run faster but for a while only)
2. Is it possible to "overclock" a battery so that it support a stronger 6v motor (as usual, same performance at cost of duration)


texts: I'm currently trying to learn how binary adders work, but I don't understand what a "carry in" is for. What is the purpose of a "carry in"?


texts:
I have a linear peristaltic pump (salvaged from medical equip. - likely used for dosing, etc). It uses a stepper motor and an optical shaft encoder. I have the motor working but I am confused about getting the wiring for the encoder sorted out. I've already done a search on the number appearing on the part and got no hits.

This is probably very simple - there are 4 wires: red, black, green and white. I don't want to blow the encoder out so I thought I would ask here. Can I assume that:

red Vcc 5v
black: gnd
green: channel A
white: channel B

I'll be using this with an arduino - so would I need pull up (or down) resistors on the signal lines? And if I can't assume the above, is there a way I can determine how to wire this up?

And finally, the encoder wheel has two slots in it - and I am trying to figure out what they mean in terms of pump state. Finding initial position at start? Or pump compression state.


texts:
I need to convert the duty cycle 250Hz (5% to 95% ) into analog voltage from external sensor (PWM sensor with low side output).
See attached circuit .
I use 74HC14 logic to have duty cycle in logic supply voltage range and the 2nd order low pass filter to get analog voltage for ADC.

The issue is that step respond of this filter is 0-95% -> 65ms 0->99% 130ms.
In addition I have the ripple voltage of ~50mV (~ 1% of duty cycle)

DO you have any idea how to have the faster step respond and lower ripple voltage?
I would like to make it as simple as possible.

In addition,  I am thinking about software filter.
Do you have any examples of filter which I could use to have faster step respond and reduce ripple voltage ?

What would be the middle point between filter parameters and  software filtering capability for such signal to get decent accuracy /fast respond?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to build a driver circuit for an ultrasonic transducer for fog making. The circuit is required to generate a 1.6 MHz signal to drive the ultrasonic transducer.

I have found a circuit which seems to be working from here. The author of the video claims that he designed the circuit. Here is the circuit, ( The buzzer symbol is used for the ultrasonic transducer)

I have built the circuit and it works to some extent. I was able to capture an output waveform using my USB Oscilloscope.

The circuit generate a good 1.7 MHz sine wave. However, I am unable to understand what type of oscillator is this. It seems to be a Colpitts oscillator, but I cannot find how to match this with a Colpitts oscillator.

I need to understand the operation of the circuit and how to change/calculate frequency values.

Edit--

Here is the waveform between base and emitter. It has the same frequency


texts:
I would like to be able to capture a signal from my DSO and run it through a simulator to allow me to develop a simple analog preprocessor for a brushless motor speed sensor. Please correct me if I'm wrong, but it appears to me as though Spice-style simulators won't help me here -- they will do DC, sine wave and impulse analysis, but won't simulate the response to an arbitrary waveform.

Is there a (free as in beer) simulator which would help me?


texts: how to calculate the current at the 4 brushless motor

texts:
Motors specification:

380KV

throttle: 50%

Amps 1.6A

Power: 23.68W

thrust: 430G

RPM:2600

Efficiency:18.16 G/W

Temp: 45C

Battery Voltage: 14.8V

Voltage stepped down from 18.62V to 14.8V

Propellers: 15x5CF

Net thrust= 1308 g ( weight of the project)

I would like to know how to calculate the current and the voltage that are marked in the circuit. please let me know if you need more information

Datasheet Link


texts: How can we reduce the amount of energy consumed by a large number of electrical motors in a factory?

texts:
if we suppose we have an electrical installation in which we have 1000 motors, and we want to reduce the amount of energy consumed by those motors.
where can we start and what do we need to do ?
what are the things to focus on ?
and what are some solutions we can give in order to reduce the amount of energy consumed by a particular motor ?
what are some problems that need to fixed while the motor is operating and that can result in consumption reduction if they are eliminated ?

Thank you in advance.


texts: What type of power adapter barrel is this? DC in 12V 3A negative semi circle positive anker

texts:
I cannot find another adapter that fits this specification. (Maybe I do not know the terms.)
It is a positive center, DC in: 12V 3A. The device itself is an Anker AH221. I tried to measure the head, and I think it is 1/10th an inch ~2.5mm.
The symbol is only a half circle--nearly everything on Amazon I find is 3/4th a circle, with https://www.amazon.com/12V-Power-Adapter-Supply-2-5mm/dp/B00447C4HM being an exception. However, it is only 1A, and the reviews claim that a 2.1mm ships instead.


texts:
I have an LED connected to pin RA1 of PIC18F25K20 (powered by 3.3V supply) in the following way:

5V rail -> Resistor (200 Ohm) -> LED Anode -> LED Cathode -> RA1

RA1 : Input -> LED is off
RA1 : Output Low -> LED is ON.

Is this the correct way to connect the LED, as the PIC is powered by 3.3V and LED is connected to 5V?

I initialized RA1 to be an input as shown in the DEVICE_Init routine. Code is written in C language - Microchip C18 compiler.

void main()
{
    DEVICE_Init();
    //wait one second
    while (1)
    {
        TRISA = 0; //led is on
        //wait 2 seconds
        TRISA = 0x06; //led is off
        //wait 4 seconds
    }
}

void DEVICE_Init (void)
{
    OSCCON = 0x73; //PRIMARY INTERNAL OSCILLATOR
    PORTA = 0;
    LATA = 0;
    TRISA = 0x06;           //RA1, RA2 INPUT
    ....
}

When I first power up the chip, the LED turns ON for a fraction of a second and then turn off. My understanding is that the IO pins are input on reset. So why would the LED turn on for a brief moment at power up?


texts:
I have four separate nodes (A, B, C, and D) that will transmit via a common CAN bus.
For a full packet of data to be sent to a node, each CAN controller has to send three times (20 bytes of data).

Node A, B, and C request data from D.

A has a lower ID than B, B has a lower ID than C, but greater than A.

My question is: If A sends its first packet to D and is almost about to send the second packet (delay due to loading of data into transmit registers), and if B detects that the bus is idle, will B begin to send?

Even if B begins to send, if A's transmit buffer has been loaded, will A send? If A sends data, will D receive the data uncorrupted?

Note: I'm thinking of implementing time slots for each node A, B, C (but I won't be using the full potential of CAN).