texts: reverse polarity and low voltage protection circuit proposal

texts:
I'm designing my own li-ion single cell protection circuit, whose requirements are the following:

Shall be protected against reverse polarity
Shall disconnect power whenever the voltage battery is too low (around 3.4 or 3.5V)
The disconnection upon low voltage mechanism shall have an hysteresis of around 0.3V
All disconnections shall be made by the high side, to keep common ground reference with the battery pack
Of course, the thresholds for low-voltage disconnection shall be independent from the battery voltage level
The system shall have an LED indicator, which lights up when the power gets disconnected for low-voltage reasons

The circuit will be made with relatively simple parts and comparator(s)
Because all the threshold voltages need to be stable no matter the battery level voltage, I chose to power my analog comparators from a voltage reference, and to create comparison voltages also from this reference.
Since I'll need to turn on and off a P-MOSFET from comparators running on a lower voltage (the reference voltage) than the battery, I need open drain analog comparators.
Since the open collector output driving the MOSFET will be pulled up to the battery voltage, it can screw-up the hysteresis feedback. The only thing I can think of to prevent that is to use a first comparator as the comparison stage, and a second comparator as a buffer stage, which then doesn't need hysteresis, and whose output can be pulled to Vbat without any problem.
I would like to use the same comparators for both the comparison stage and the buffer stage, with both channels in the same chip (a dual channel comparator)
For the LED indicator, the only thing I can think of is to use the output of the buffer stage to drive an N-MOSFET transistor.
With all that in mind, I came with the following parts:

The REF3020AIDBZR: a 2.048V 0.2% voltage reference able to supply up to 25mA
The MCP6547T: a low voltage (1.6V - 5V) open drain dual channel analog comparator with low quiescient current (below 1uA)
I haven't chosen the MOSFETS yet, but I'll go for jelly bean parts, they don't matter that much, as current through them will be quite low. The only constraint it that they will have to be switchable with an absolute Vgs of 3.4V max.

And this is the schematic I came up with (I haven't noted resistors values and tolerances, I'm only interested in the working principle now):

simulate this circuit – Schematic created using CircuitLab

M1 is the reverse polarity protection
M2 acts as the low voltage switch
M3 is the Low-voltage LED NMOS

My concerns are the followings:

The buffer will have to drive 2 MOSFETs when its output is low. Will the input gate capacitance prevent the design from working ? I don't really know if I should use a gate driver or not... (note that switching speed doesn't really matters here)
This design could take a bit of board space due to the 2 comparators and the whole lot of resistors, maybe there is a simpler circuit with less parts I haven't thought of. This circuit, if working, should be okay, but less board space for this protection circuit will make things easier.
Is powering comparators from a voltage reference that clean ? There shouldn't be any issue since the voltage reference is able to supply 25mA, but I'm not sure.
From my point of view, this should work without issues, but If you can confirm this to me, it would be great !

Thanks a lot in advance !


texts: Power a 12V DC wifi-router using 6V relay as switch between two power sources

texts:
I had build a circuit that can provide current to 12-V wifi-router from two different sources (wall-adapter & battery.)

A 6-V relay is used as switch, to supply power from one of the source at a time.

When wall adapter is on:

Problems with the Circuit:

1. As 6V relay is powered by 12V adapter, It gets hotter by the time passes(1 hour or more).

2. When primary power (wall adapter) goes off there is tiny-bit delay in supply the power to wifi router so it gets restarted.

What should I do to overcome these problems?

Q1. How do I step down from 12V to 6V, to power the relay.

Q2. What kind of capacitor be use for the short term power in delay time?

** Upgrade with capacitor & Relay **

I have added 2200µF 16V Capacitor with diode, before the Load to ensure power could be supplied for the 2-3~ seconds delay while switching between sources. unfortunately capacitor is powering the Relay instead of wifi-router. what should I do to ensure isolated current to wifi-router?
Replace the 6V relay with 12V relay.

Note: I am new to electronics that is why I make circuit as simple as possible. I know I had done some blunders in the circuit. Kindly guide me through.


texts:
Refer to this Question: MOSFET Gate Driver Simulation Problem

My Gate Driver datasheet: http://www.irf.com/product-info/datasheets/data/ir2104.pdf

May I ask why there are two capacitors instead of just one hooked up in parallel between Vb and Vs? I am also using a gate driver to drive the FETs of my synchronous buck converter, and I am having similar trouble turning on the high-side FET.  I also have everything hooked up as in the IR2014 datasheet (which I've also attached) except I'm not using any resistors between HO (LO) and the high-side (low-side) FET gate. Maybe this could be my problem, but I can't figure out why that would be so.


texts: IC datasheet and MOSFET selection question

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I am trying to design a buck converter using TI's LM3150 synchronous buck controller and I am wondering how to read some of these specs and how to select MOSFETs based on gate charge:
https://www.ti.com/lit/ds/symlink/lm3150.pdf?ts=1594337765626&ref_url=https%253A%252F%252Fwww.google.com%252F

It says VCC current limit is 65 mA, but why is the current limit is at VCC=0?
Thereotical you should size the MOSFET gate charge and switching frequency so that VCC current limit < (Qc_Total * FSW). However, in the past few days, I saw a couple of TI reference designs (for other power controller ICs) that didn't apply this rule and they paralleled a lot of FETS in each switch. In theory, it wouldn't work if the minimum current limit is really 65 mA (maybe this only happens at the extreme temperatures). Am I not understanding this right? Or maybe their designs are really only "reference" designs and not meant for production?
Thanks.


texts:
i am doing a series LCR experiment for measuring the resonant frequency taking,
R= 100 ohm; L= 40mH; C=0.1uF. I am using a 10KHz audio oscillator having 10V p-p as the input.

I have fixed the input voltage at 3V (rms value). But, on increasing the frequency(say, from 100Hz), the input voltage keeps dropping till I reach the resonant frequency (approx 2KHz)and then increase on increasing the frequency further.

 For example: At 100 Hz, Vi=3V;
             At 2000Hz, Vi=2.2V;
             At 10KHz,  Vi=2.4V

Is something wrong with the circuit? What should be done to stabilise the input voltage,Vi?


texts:
Suppose I have an array:

#define ARRAY_SIZE 576
#pragma udata DATA
float I_1[ARRAY_SIZE]; //My huge array
#pragma udata

And that I access my array like so:

float compute()
{
    float *I_1_ptr = &I_1[0];
    //Somewhere in loop
    I_1_ptr[i] = IL_1 - IO_1 * (exp(Q * V_1/ (NS * N * K * temperature)) - 1.0) - V_1/Rsh;
    //Consider other variables constants.

    return (I_1_ptr[0] + I_1_ptr[1] + I_1_ptr[2] + I_1_ptr[3]);
}

I've seen on search results on Google that Microchip prefer that one should access the array by pointing to it's first element using pointers.

Did I get this right, or how do I access my array I_1?

For some reason, my calculation doesn't work on my array and when I do division by zero, I get NaN.

Thanks.


texts: Relay coil inductance variations vs. temperature

texts: How does relay (something like this https://www.hobbytronics.co.uk/datasheets/songle-12v-relay.pdf) coil inductance changes with increasing/decreasing temperature? And how can we calculate the new value of coil?


texts: Why often is used a varistor 7D471K for 220-240vac surge protection rather than a lower nominal voltage one?

texts:
In my "supposedly" surge protected power stripe there is a varistor for surge protection configured to simply short-circuit the entrance wires in case of surge.

Checking the model it's a MOV-7D471K that on Mouser is reported having the following specs:

Voltage Rating DC: 517 VDC

Clamping Voltage: 775 V

Diameter: 7 mm

Peak Surge Current: 1.2 kA

Surge Energy Rating: 30 J

Capacitance: 105 pF

This has confused me since these values seems to me too high considering that is supposed to protect a 220-240vac max line (European domestic distribution range), and searching on web seems that is often used this MOV for domestic surge protection.

I have seen also that MOV-10D221K seems having values more near to 220-240vac:

Voltage Rating DC: 242 VDC

Clamping Voltage: 360 V

Diameter: 10 mm

Peak Surge Current: 2.5 kA

Surge Energy Rating: 32 J

Capacitance: 450 pF

Why is used MOV-7D471K rather than MOV-10D221K (or some other, suggestion are welcome)? Is my power stripe bad configured or I'm missing something?


texts: Improving the classic 18V mod for guitars

texts:
I am trying to figure out how to use a potentiometer or some form of fader to bring my circuit from 9 V to 18 V, and then back to 9 V without it being permanently one or the other, having to disassemble to change.

I don't want popping from an DPDT switch.

I'm wanting to be able to roll it up to 18 V when I need more headroom and then roll it back down to 9 V for a grittier sound.

What is the most efficient way to do this, what do I need?
Before its mentioned yes the guitar has a gain boost.

Edit: the power source is two 9 V batteries rated at 540 mAh. The current draw is 1.22 mA @ 9 V total. (3 active humbuckers 0.08 mA @ 9 V each with boost preamp 0.98 mA @ 9 V.)

I hope this helps.


texts: Can an electric heat mat cause fake touches on a capacitive screen?

texts:
After installing one of these heated desk mats on my cold work desk, I've noticed some erratic behavior on touchscreen devices I develop software for when they're laid down on the mat. Most noticeable on iphones, when the heat is on, part of the touch grid becomes unresponsive and sometimes receives ghost touches. It happens regardless of device temperature.

I'm posting here in EE, because I have a suspicion the cause might be some sort of electromagnetic interference. I'm happy to move it elsewhere.

There seems to be a cause-effect relationship, because it's happening on multiple devices from different manufacturers. What is going on here?

Here's a video demonstrating the effect:
https://youtu.be/0jz8HaytlEs


texts: I bought a Li-ion battery which was deeply discharged, now what?

texts:
I bought a battery for my laptop from a local store.
When I inserted it into my laptop and tried to power it on, I noticed that it was deeply discharged. Then I connected charger and then it started charging.
To check the battery state I powered it on and found out that battery percentage was zero.
Then I left it for 2 hours and when I came back it was fully charged. Then I checked battery health statics and it was reported that battery is 100% healthy and has charged up to its  nominal capacity.
Now I've these questions.

Is this battery damaged due  being stored in this state for a period of time? If so then why statics report that it's 100% healthy?

What is the proper way to store li-ion batteries in warehouse as they have a self-discharge rate which leads to be fully discharged eventually even if they are 40% charged before storing them?

Does storing battery unused in a warehouse, reduce its 2 - 3 years lifespan?

EDIT:
I just checked one of my old laptops and figured out its battery was also 0% and now does not respond and doesn't recharge. Battery was detached and had been charged to 40% before being detached.


texts: Buck Regulator Running From Car Battery Stability Problems

texts:
I'm running this regulator off of a ~12V car battery. I've set it up almost identically to the 'typical application' schematic and layout that the datasheet suggests to generate a 5 V output, except that I'm using a 22 μH inductor.

The problem is that when we run the starter motor, and also at undetermined points in time when the car is driving, the microprocessor on the board dies -- presumably due to some kind of glitch on the regulated 5 V.

I suspect the problem is noise, but I can't get a proper measurement of it while it is on the car. I'm going to try measure it in lab at some point.

I've got 8-9 0.1 μF bypass capacitors at the microprocessor, but apparently it isn't enough. Another problem might also be because the regulator is running in discontinuous mode most of the time. If I were to redesign it should I put some filters at the input of the regulator? Is this something that is typically necessary?

What's the best fix for this? It's too late for me to add signicant hardware to the PCB, but what would be the best thing to do if I redesigned it?

For reference, this is my layout, (C102 is the input cap, D101 is the catch diode, C106 L101 are the output filter network, R102 is a jumper to the 5V plane). The important loop (catch diode/input cap) is at the bottom.


texts: How to offset an input voltage of 0V ~ 10V to -400mv ~ +400mv?

texts: I have a circuit input which provides a voltage range of 0v to +10v DC. How do I change this output to -400mv ~ +400mv DC ?


texts: Esp8266 nodemcu v3 connection to usb fingerprint scanner

texts:
My project is about making an ioT biometric attendance management using Esp8266 nodemcu and a Morpho usb biometric scanner.
So my question is whether  is it possible to connect a usb fingerprint scanner to esp8266 and send the data to Android app .Actually i want the fingerprint scanner should be connected to Esp8266 module which will act as Access point for Android app and send data to android device through wifi ?

I am attaching the picture of fingerprint scanner


texts:
Building a Z80 computer, would like to boot CP/M from ROM and switch the ROM off after initial boot to make whole 64k RAM available for the CPU.
Solution I've got so far is using a flip-flop to disable ROM (and enable RAM) when a specific address range (0x8000-0xBFFF - i.e. A15=1, A14=0) appears on the bus. CP/M code starts from 0xDC00 so no issues with this approach as far as I can see.
Upon a reset, ROM and RAM2 becomes active, and once the switch occurs RAM1 and RAM2 stays active until the next reset.
1 - I tried to go through every case and it seems to be correct, but do you see any issues with this design?
2 - Can you sport any further simplifications? I feel like I used too many NAND gates :)

Note: This is a follow up to a question on RC.SE, as it was mentioned there, that SE.EE would be more relevant. This solution is partly based on recommendations given previously.
EDIT: Revised version to incorporate MREQ:


texts: Even though the signal gets low several times a second why our eyes are only able to see the bulb glowing all the time

texts: I was learning Pulse Width Modulation and it told me that it just the technique to change the amount of time the signal gets high in one wave, but why am I able to see the bulb glowing at all the time even if the duty cycle is set to 40%.


texts:
I have an LED strip being controlled by an Arduino and powered by a molex connector within my PC. I'd like to have my Arduino connected to my computer via USB 24/7, however when I do this, the molex grounds itself through the USB connection when I toggle the switch to the off position, so the LED strip does not turn off when I want it to. Also, I don't feel comfortable grounding molex through USB. Is there any way around this? I have a reasonable background with electronics, but I'm just not sure what to do in this case, and I couldn't find anything on the internet. Thanks.

simulate this circuit – Schematic created using CircuitLab


texts: How can I add N channel MOSFET for reverse polarity protection?

texts:
I would like to add a reverse polarity protection circuit to protect my circuit from reverse polarity.

I tried to use following circuit at this link

With NMOS FET, I have a little problem. If the voltage is too low the FET isn't turning on and the current flow through the internal diode. But I think the diode isn't in a good direction. If the voltage is high enough e.g. >3V, the MOSFET is turning on and current flow through the MOSFET.


texts: Way of powering Arduino+GSM Modem+Cam off 5V powerbank

texts:
I'm trying to build a circuit, that would turn the Arduino on by a PIR sensor, take the picture by ArduCam, then transfer it onto a webserver.

I got the SW site covered by now, so that is not a big deal:

Arduino turns on, sets up the Camera
Cam takes the picture, goes into low power mode (since 390mA is pretty savage and heats it up quickly, compared to 20mA in low power)
Now GSM modem boots up, which takes about 30-60 seconds for it to fully setup and login to network.
After that, we set up a connection to the server and upload the image from camera memory (without even turning it back up), onto it. Despite specifications, it usually eats about 150-170mA, with spikes of around 200-250mA.
After the transfer is complete, I shutdown the modem.

Now the real deal - hardware connections.
Right now, the GSM modem is stacked on Arduino, and to that is connected the camera. GSM modem has three possible ways of powering it- Vin, 5V and USB. Right now, despite it's stacked, it is also powered by the microusb port from the same powerbank, and that seems to be working, because otherwise it crashes during connection, even if I connect it (that stack) to a single 2.4A port.

I want to make it work like this, except that the Arduino would wake up on signal from PIR motion detector, but not like "through interrupts", but like, cold-boot.

To achieve this, I thought about placing a MOSFET, connected to the output of that PIR, which would work as a switch.
The thing is, it would also need to be "kept alive" by arduino, so basically I thought about some diodes from digital pin and the output from PIR. Am I right in my way of thinking, or there is something I should change. Seemed doable at first, but I got lost in the forest of MOSFETs and diodes. Which ones should I choose? Is there any better way of connecting it than just stacking them?
Also, it's the only possible option of powering it, since it would be in remote location, so no power adapters or some special batteries that would require the second arduino to make use of them.

As for now it seems to be working when its connected to both USB ports. Assuming that I can turn off the modem from Arduino, it shouldn't draw too much power, so basically my question boils down to "What transistor should I choose, that would turn on the arduino on signal from PIR"?

Also I'm attaching a picture where I tried to describe it as best as I could.


texts: I need guidance on designing a 2 kV capacitor charging circuit

texts:
I have to design high voltage circuit for the first time in my life.
Its purpose is to provide enough voltage to make a spark plug ignite a coal powder mixture.
There are some requirements for this circuit:

Capacitor C6's capacitance above 50μF at least.
Make charging time as short as possible (about 50ms to 100ms.)
Charging voltage must be above 2kV.

I followed some circuits from the Internet, and finally I reached this circuit design:

It doesn't work well enough.
Vibrator frequency is about 3kHz to 4kHz, duty cycle is 50%.
I used an ideal transformer in OrCAD - the primary coil is 465μH, the secondary coil is 46500μH.
It takes 200 milliseconds reach to 400V.
I need advice on this problem.


texts: What kind of connector do I need to splice this cable?

texts:
The LCD display on my range hood started to go bad with dead pixels. The manufacturer sent me a replacement part (see photo). I thought swapping out the part would be trivial. The problem is that the connector is way out of reach; I'd have to remove the entire blower assembly to be able to disconnect the old cable and attach the cable of the new part.

So I thought it would be easier to take the cable of the new part and attach the new part to the cable of the old part. Then I ran into my second obstacle: it doesn't look like the connector is meant to come off. The contacts to the wires appear soldered onto the board (see second photo). That's probably why I was not able to detach the plastic part off.

So I'm stuck. As a last ditch effort, I'm thinking that I could cut the cable, strip the wires, and put on a new connector to attach part of the old cable to the new cable. I.e., make 2 cuts and splice old cable to new.

Is this a good idea? If so, what kind of male/female connector do I need? (I'm a software guy so this is all new to me.) With some tips to point me in the right direction, I can do more research online. Thanks!


texts: Led as an input photodiode [Arduino AVR]

texts:
I’m trying to use a LED as a light sensor(input) connected to a Arduino Nano.
I connected the led with the Anode at digital pin 8 (PB0) with a resistance of 56 Ohm and the Cathode at an analog pin A0 (PC0).

    The main idea is to measure the voltage across the parasite capacitance in the LED which was stored during a short 5V pulse(turning PC0 high and then low) in reverse bias.
    First example is very simple.

uint16_t sen_time = 0;    //Variable for counting
void setup() {
  Serial.begin(9600);
  // Setting pin 8 to OUTPUT and the rest to INPUT
  DDRB |= (1 << PB0);   // Setting OUTPUT PB0
  PORTB &=  ~(1 << PB0);   // Setting Anode LOW

  TCCR1B |= (1 << CS10); // Setting timer, no prescaling(f = 16Mhz)
}

void loop() {
/* Reverse bias pulse */
  DDRC |= (1 << PC0);     //Setting A0 to OUTPUT
  PORTC |= (1 << PC0);    //Setting A0 to HIGH
 /* Setting Threestate Cathode */
  DDRC &=  ~(1 << PC0);    //Setting A0 to INPUT
  PORTC &=  ~(1 << PC0);   //Setting A0 to LOW

  TCNT1 = 0;  // Setting timer the moment we turn off
  //Waiting for the led to discharge and counting
  while (analogRead(A0) != 0)
  {
    sen_time++;
  }
  Serial.print("TCNT:");
  Serial.println(TCNT1);
  Serial.print("sen_time:");
  Serial.println(sen_time);    //Print the value
  sen_time = 0;                //Setting the value to 0
}

The results are as follows.
In normal conditions:

In darkness:

In heavy light:

The variable which is incremented sen_time is pretty much accurate, having high values for darkness and low values for heavy light. But I can’t understand why my timer has trash values all way around.

I’m trying to solve it with interrupts(Pin change interrupts) but getting the pin three-stated just triggers the interrupt all way around. Plus the TCNT got trush values whenever I read it. Getting pull-up resistors just keeps the pin high.
Some advices about how to solve this problem preferably with interrupts (due to time restriction on future project). Thank you and I hope to solve it as soon as possible!


texts: Should I assume my LMV324 is counterfeit?

texts:
I just got a bunch of LMV324IDR rail to rail op amps from ebay. I hooked one up and it seems to saturate 1.3v below the supply voltage (at 3.7v for 5v supply).
There is no load at the output of the op amp (just a scope probe, 1MOhm).

This leads me to believe that the op amp might be counterfeit.

Am I right to assume so ? Is there a way to check ?

Edit:
As requested a photo of the chip:


texts:
I want to design CMOS Inverter which gives:

0 volt input --> 5 V output

Any positive input voltage above threshold voltage --> 0 V output.

On simulating, it is giving me alternatively +2.5v and -2.5 at output and wave shape is also distorted. Why is it not giving +5 and 0 volt and why do we have distortion here.

Edit: Setting both signals to DC coupling

Now it is showing 5 V signal at oscilloscope, while the probe shows 2.5 V DC. Strange? and still there is distortion.

Note: I have to apply 5 V at input or bigger. Why is that? Threshold voltages of transistors are usually not that big.


texts: Can an X-class safety capacitor be used in series with a load (i.e. where steady current flows through it)?

texts:
Many applications that need a low voltage supply that is not isolated from the mains use a capacitive dropper circuit to get it -- an example is shown in the schematic below.

simulate this circuit – Schematic created using CircuitLab

In this type of circuit, Clim is usually a metallized-film cap (in the 100nF-10uF range depending on current draw) with a 400 or 630WVDC rating.  Can an equal value X-class safety capacitor with a 250 or 275WVAC rating be substituted instead, or would the continuous current flow pose a problem for the X-class capacitor/a hazard to the outside that is greater than the current capacitors used?  Would using an X-class capacitor for Clim provide any benefits over the current non-safety-rated capacitors used in that position, even?


texts: minimalistic digital 2-speed oscillator with 555

texts:
I'm trying to figure out how I can turn a schematic of a one-speed simple 555 astable multivibrator that's available everywhere on the internet to a digitally controlled astable multivibrator in which the output frequency changes depending on the digital input.
More specifically, I need such a circuit to make an elegant programmer because the chip needs a longer pulse for erase and shorter pulse for data writing. (I'm programming AT89C2051). So I want to use a 555 and a transistor along with a high-inpedance or logic low input to choose between a 1.2ms and 10ms delay between each pulse from Q in the 555.
Am I on the right track with the circuit I came up with that's shown below?

EDIT
Ok I included a full circuit.

Yes I can program but I want to make life a little easier for myself considering my last circuit I made was a failure. Now with a few modifications I can make it function like an MS-DOS printer. that way, if my system completely screws up and all I'm left with is a boot disk with no hard drive then I can still use my circuit.
So my question remains the same. Am I on the right track with the 1st circuit shown?


texts: NMOS limiting circuit for Colpitts oscillator

texts:
According to my book, the amplitude of the output sine wave produced by the following Colpitts oscillator should be limited by transistors M1 and M2. We only get a final answer without reasoning and after many hours of trying I still fail to prove the final result.
Can someone please explain how M1 and M2 are limiting Vout?

The actual assignment reads:

In fig. 2, assume the oscillator starts up and reaches a stable steady state in a finite amount of time. Assume the loop gain for small signals is slightly larger than 1. Assume the W/L ratio of M1 and/or M2 (if used) is very large. Assume the supply voltage for the gm block is sufficiently large. In steady state, the peak-to-peak amplitude of vout will be approximately:


texts: What are markings on top of electrolytic capacitors?

texts:
I often see a marking like the following pattern on the top of radial PTH elcos.

What does it mean? Is it an identification of the manufacturer?


texts: Can raspberry Pi 3 and Lidar lite v3 connecting without resistor in circuit?

texts: I recently try to use Lidar Lite v3 with my Rpi 3, and it works with I2C communication. My wiring method is due to offical documentation.  However, what I have learned before is that the gpio pin of RPI can only afford 3.3v working voltage. My Question is that shouldn't I add the resistor in my circuit to prevent from breaking out the pins of my RPI ?


texts: About the heat of the matching circuit of MRF151A

texts:
I output 100W(@100MHz) under the following conditions, but I do not know the reason why the temperature of the device becomes high and the solution.
Source matching: Function generator → Cp(82pF) → Ls(22nH) → Cp(18pF) → MRF151
Load matching: MRF151 → Directional Coupler → Cs(82*2pF) → Ls(13.5nH) → Cp(68+82pF) → Ls(43nH) → Cp(18pF) → Load(121.130 + i17.425 Ohm)*Since the assumed load is around 100Ω, adjust with a matching circuit.
The constant of the matching circuit is the result of changing the element value and performing source and load.
I think it is necessary to know the impedance of Tr in order to find the Q of the matching circuit. How do you find it?
Please give me some advice.
https://cdn.macom.com/datasheets/MRF151.pdf

Supplement
2020-09-01
First, the output load was 50 Ohm for load pull. After that, the output impedance of Tr was calculated back from the matching circuit that outputs 100W. Utilizing the output impedance, I tried to operate with a matching circuit that lowers the Q on the Smith chart to 100 Ohm. However, the output was very low, so the result of load pulling again with a load of 100 Ohm is the matching circuit described when I asked
I forgot to mention the parts that generate heat.
One is a dual directional coupler with a pattern between the transistor and the matching circuit.
The other is not a matching circuit, but a coil placed in the power line.
2020-09-02

fig1 The planned circuit.
2009-09-08
An image of the impedance measurement of each element additionally performed by the spectrum analyzer.
The element between the transistors was removed from the measurement point for measurement.

fig2 Circuit when 100W output.

fig3 circuit diagram

pic1 pcb

pic2 DDC

pic3 C309

pic4 L303

pic5 C311

pic6 L304

pic7 C313

pic8 Simulated impedance in each element.


texts:
I need to drive bi-color LEDs, wired anti-parallel at the far end of a 1.25 m cable.

The LEDs take 15 mA.

To drive this I am planning on using a full-bridge (H-bridge) composed of two logic gate inverters and the LEDs in between. To achieve the current I need the "Ultra-high-speed" (low Rout) gates to be able to drive the 15 mA in steady state. My concern is that the inverters will launch fast edges and the cable length will cause reflections and cause over-voltage/latchup.

The rise times need to be >50 ns to keep the electrical length to 1/10th the wavelength or less:

$$\lambda/10 = 1.25 m => t_{rise} > 42 ns.
$$

My plan is to add a 10 Ohm/ 1nF: $$\tau=68 ns$$ low pass filter to limit the rise time.

Any other ideas?

The stuff inside the dashed line is located 1.25 meters away on a cable.


texts: How is dead time in a half bridge implemented

texts: I was wondering if dead-time in a bridge design is achieved by the turn-on and turn off resistors as shown below, so that the FETs turn on slower and turn off faster, thus avoiding shoot through. Or does this need to be implemented in code?


texts:
I designed this circuit (shown below) to level shift an input PWM (10 kHz 5% duty) signal (from microcontroller, 0/+3V3) to 0 and -12V. When the input PWM is HIGH (+3V3) the output is at 0V while when the PWM is LOW (0V) the output is at -12V.

The circuit operation (actual response graph) can be seen below;

I wish to improve the circuit response hence matching the desired response graph (shown below). I also wish to stay limited to the basic components i.e., resistors, capacitors, transistors (2N3904/2N3906) and opto-couplers (4N25/4N26/4N33). I also need to keep isolation and a small duty cycle PWM input (<= 5%).

Any tips/design changes are greatly apricated, Thanks.


texts: Building a D flip-flop with two D inputs using 3 S-R latches

texts:
"Use three clocked SR latches to build a D flip-flop with two D inputs (D1 and D2 ) and two clock inputs C1 and C2 . Clock C1 takes data D1 and clock C2 takes data D2 ."

Any hints how to start?


texts:
I've been learning to program LPC2148(ARM7) microcontroller, and today I got hold of an LPC1768(Cortex M3) board. By referring it's manual, I tried to make a LED blink program and did it as follows, following the same methods as LPC2148(configuring pin connection block and GPIO registers)
#include <LPC17xx.H>
int main()
{
  int i;
  PINSEL0 = 0;
  FIO0DIR = 0XFFFFFFFF;

  while(1)
  {
     FIO0SET = 0XFFFFFFFF;
     for(i=0; i<100000; i++);
     FIO0CLR = 0XFFFFFFFF;
     for(i=0; i<100000; i++);
  }
}

But got error as PINSEL, FI0SET ... as undefined.
after referring some example codes, I have to use
LPC_PINCON->PINSEL0 = 0X00000000;
LPC_GPIO0->FIODIR

Where does this LPC_GPIO & LPC_PINCON come from?
As per one online tutorial
As per the CMSIS convention, the registers that we saw are grouped into structures. LPC_GPIOx is defined as a pointer to this structure in LPC17xx.h header. These registers are defined as members of this structure. Hence to use any register, for e.g. FIODIR, we must use the arrow “->” operator to de-reference members of structure (since the structure itself is a pointer) to access the register as follows : LPC_GPIO0->FIODIR = some value.
I couldn't find any reference to this in manual.
Is there any documentation available?


texts: Find state space representation with 2 inputs and 2 outputs

texts: I have no problem finding the transfer function with systems of 1 input and 1 output and then I can easily obtain the space state representation, but this exercise requires me to "Find the space state representation of the circuit, assuming the outputs are the currents in R1 and R2". How do I start thinking about this problem?


texts: Under what circumstances would 5V@2.1A be lethal?

texts:
Besides obviously sticking an output of 5V directly to the heart. Are there areas inside the body where resistance in ohms is so low that a 5V electric potential would be fatal?

I got into an argument about this with my roommate after he made a joke about sticking an lightning apple lightning cable directly up his urethra. I told him that his brilliant idea could  cause a nasty shock since internal body resistance is so low. He, however, insisted that the lowest internal body resistance still sits at a few hundred ohms and 5V (5V 2.1A Charger) would not suffice to provide a dangerous current.

Would it be possible for internal resistance in this area to be so low that even 5V or less would be dangerous? Say it took a path up the bladder and through the kidneys and to the heart.


texts: Maximum number of opcodes for a microprocessor

texts:
What is the maximum number of opcodes for the question, the answer is c option, but i think it is option d, because, each address specifies each memory location, there are 16 address lines, which means 2^16 addresses i.e., 2^16 memory locations.

So, if each location contains one opcode, total 2^16 locations contain 2^16 opcodes and it is maximum number of opcodes, but the answer is given as c, which is 2^12 . How is this possible?


texts:
Complete the diagram of sequential circuit whose sequence is given below:

State  a a b c d e f f g f g
Input  0 1 0 1 0 1 1 0 1 0 0
Output 0 0 0 0 0 1 1 0 1 0 0

Draw logic diagram using SR Flipflop.

I do know how to do the excitation table for SR flipflop, But I need some help to understand how to understand the state table. Can someone make it clear?


texts: What does the diode in this D flip-flop "One-shot" do?

texts:
Does this diode help discharge the capacitor once the flip-flop is reset?

Thanks in advanced.

(Image was taken from http://educypedia.karadimov.info/library/oneshots.pdf)


texts: Input of boost converter or charge pump in the energy harvest

texts:
I read some paper about the energy harvest, and lots of paper said the induced voltage from, for example, the thermo-electric harvesting could be as low as tens of millivolts in a realistic case, so their input of boost or charge pump is less than 100 mV.

But in some paper, I found the author will set the input from 30 mV to 300 mV, some paper even set the input to 3V. Why? If the induced voltage is only tens of millivolts, then 100 mV should be unless, because you cannot have this high voltage, higher than 100 mV, to feed the boost or charge pump, then why do  some authors still let the voltage be so high? Maybe induced voltage can be higher than 100 mV in some other kind of harvest. If so,can anyone give me an example?

Paper example 1(input 30mV~300mV):http://ieeexplore.ieee.org/document/6419064/

Paper example 2 (input 450mV~3V):http://ieeexplore.ieee.org/document/8234200/


texts: Reverse bias I-V characteristics of mosfet

texts:
What is the equation for a N-channel MOSFET's current value (\$I_{DS}\$) given a negative drain-to-source voltage \$V_{DS}\$?
I can find plenty of forward biased I-V curves for the N-MOSFET, but I haven't found any reverse biased ones.


texts: Zynq - Configuring SPI clock to idle high

texts:
I am trying to use the SPI0 component of a Zynq XC7Z010 to read data from a 12-bit rotary encoder which uses an SSI protocol.

I have a small example project set up in Vivado which enables the SPI0 to use EMIO ports and sets the pins I want to use.
I also have the xspips driver working and am able to receive data from the encoder.
The problem I am facing is that I could only set up a clock signal which is idle low, while the encoder expects an idle high clock.

Due to this, the first bits received are unusable, and I had to do some bit-manipulation to recover these bits (the encoder starts repeating the same data again after the 12 bit transmission).

With an oscilloscope I tested out that the sent out clock signal is always idle low, whether the CLK_ACTIVE_LOW option is set or not for the SPI, so I concluded that that option is only for how the Zynq interprets the clock signal.

How can I have a clock signal that is high by default? Do I have to manually invert it in the Vivado generated VHDL wrapper, or is there a simpler solution?

Measured clock signal for a 2 byte transfer when ACTIVE_LOW is enabled:

and when it is disabled:


texts: SPI Reading memory over SPI with Bus Pirate

texts:
I'm trying to learn about SPI and I have a old Bluetooth headset with SPI solder points on it. I've already soldered the corresponding {MISO,MOSI,CS,CLK} pins and connected them to the Bus Pirate correctly. The chip on the headset is a CSR-31315 (9A11U-717AT) which I've found a PDF for (SPI on pg. 74).

The PDF says to perform a read operation all that needs to happen is the CS needs to go from high to low, then a 8-bit read command of 0b00000011 needs to be sent, then the 16-bit address to read needs to be sent. After that it will output on MISO a check word which is composed of {command, address [15:8]} (what is the [15:8] for?) and then finally the contents of the address. Then last take CS high again so it doesn't continue on to print the Address+1 on MISO.

The command I'm feeding to my Bus Pirate is [ 0b11 0x00 0x00 r:16 r:16 ], which I believe should take CS from high to low (it idles high), output 0b00000011 the read command, write the 16-bit address of 0x00 0x00, read the 16bit checkword, read the 16-bit address data, and finally take CS high again. I think that should work but it doesn't.


texts: Are polystyrene capacitors equal to electrolytic ones?

texts: My atari 2600 has no sound, which is a common problem with an easy fix, just replace 2 capacitors. The original capacitors are 820pf polystyrene axial capacitors, and these are a bit tricky to find. Could I just replace these with any other kind of capacitor like an electrolytic or ceramic one? DO they do the exact same thing or are they different?


texts: Kirchoff's law finding the voltage across resistors

texts:
I’ve just started an engineering course, and my 1st module is electrical engineering. Unfortunately my teacher is a 100 years old and hasn’t explained Kirchoff’s law to us in an understanding manor. In this question I’ve been asked to find the voltage across each resistor. Please could someone explain to me how this is done. The simpler the explanation the better, I honestly won’t find it patronising, it would be a great help.
Thanks in advance


texts: Different types of DC Motor with PIC + Bluetooth

texts:
I have an issue with DC motor and Bluetooth.
I'm using PIC PIC18F, TIP 31 NPN transistor as motor driver and 4 x AA rechargeable battery. Each battery is about 1500mAh.
The board has 2 modes, 1.Simple Run and 2.Bluetooh

I have 3 motors and all are in good condition:

Motor A: 2.1 mAh
Motor B: 20 mAh
Motor C: 70 mAh

In "Simple Run" mode, the 3 motors run without an issue.
But when in "Bluetooth" mode with PWM, Motor B had difficulty in running and Motor C had a slight issue. Motor A is perfectly fine.
I have an android app to control the motor using bluetooh.

It looks like the current issue. But I already use 1500mAh battery.Somehow Motor C is run better than Motor B.

What may be the issue?

It looks like the Motor draw away the current from Bluetooth module and the microprocessor. This cause the signal send from the Android App break.

Or could it be the current from the motor fall back / kick back to the board?

Should I should Motor Driver IC instead of using TIP 31?


texts:
I have hooked my HX711 to an ESP8266. I'm now faced with the problem that once I put my ESP into deep sleep mode the GPIO Pin which is hooked to the PD_SCK pin goes low.

This in turn will put the HX711 in "normal mode".

  When PD_SCK Input is low, chip is in
  normal working mode. (Page 5)

How can I keep both devices in power down mode?

  When PD_SCK pin changes from low to high and stays at high for longer than 60µs, HX711 enters power down mode.

I tried to pull up the PD_SCK pin and use the ESP8266 gpio pin as a drain but that did not work. Maybe I did something wrong.

I could introduce an inverting 74xx chip but that just seems wrong. Is there maybe something I overlooked?

https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/hx711_english.pdf


texts:
Is the current sense feedback dependent on how the driver is controlled, PWM or discrete signal.
Will the reading on ADC input differ when controlled by PWM, as we have a duty cycle?
For example if ADC sample rate is big enough is there a possibility we capture the 0 in the PWM period, so we get very variable values through the ADC?


texts: Why aren't power lines replaced when a large tree lands on them? It seems to me the wires have been stretched, thereby decreasing their diameter and increasing their resistance.


texts: What is ΔICC term stands for in datasheet?

texts:
This is the datasheet of the MUX (74LVC1G157) I am working with. While I was doing the power calculation, came to the following parameter, ΔICC.

1) What is this additional supply current stands for?

2) What is the significance of this value?


texts: Why do I measure (almost) no voltage between 230V phase and my body?

texts:
The other day I was experimenting with a multimeter and checked the voltage in one of the electric plug at home. Without surprise I measured around 230V between phase and neutral and also 230V between phase and earth (By earth, I mean the earth wire, the "3rd hole").

Then I tried the measure the voltage between phase and my body by sticking one probe in the phase hole and holding the other in my hand (Might not be the best idea if the meter as a failure or is set to measure current instead of voltage... did it nevertheless...). There I measured around 8V AC. Why ? The voltage between me and the earth should be almost 0V hence the potential difference between me and the phase should be around what I measure between phase and earth wire (230V). Which make sense since if I stick my finger in the plug I'm sure I'll get a nice full 230V shock. So why does the meter indicate such low voltage ?

My guess is that it has something to do with capacitance since Earth (big 'E') capacitance is much higher than my body capacitance and would therefore allow higher alternating current to flow in it than into my body ? (Really fuzzy guess sorry).

Thanks for you help :)


texts:
I’m trying to understand the way PRESET and CLEAR work on a positive edge triggered D flip flop, but I may be missing something that I hope someone can clarify please.

Figure1 below shows the flip flop in question.
I am using red for high and blue for low.
The positive edge detection device is an AND gate with a NOT gate.  The output from the edge detector in this diagram is low so the flip flop cannot have its state changed by a change in D.

Figure2 below is a brief moment when the clock edge is rising.  The output from the edge detector is high so Q changes to match D.

And Figure3 below is another moment when the clock edge is rising, so again Q samples D and changes to match.

As long as PRE and CLR are both high, the flip flop behaves exactly as I would expect.  A three input NAND gates only outputs a 0 when all three of its inputs are high.

But here’s my query.  In Figure4 below, the active low CLR input goes low, while there is a rising edge, so the flip flop is enabled.  The inverse of Q is now high but Q is not set to 0 as I would expect.  There is still a low input to the top right NAND gate, so Q is still high.

In Figure5 below the active low PRE input has been set to low.  This is happening on the rising edge again, while D is low.  It will make Q high as it should, but Q’s inverse is also high.

For the majority of the time there is no rising edge, and the PRE and CLEAR behave correctly, as in Figure6 and Figures7.  I am concerned because a lot of literature (websites etc.) say that the PRE and CLR inputs are asynchronous and completely independent of the input at D, and of the clock.  Can someone please clarify this for me?


texts: Measure the load on a servo very precisely?

texts:
I am trying to make a servo turn a dial. At certain points in the revolution, the dial will "stick" on certain points, where there is more resistance.

I would like the servo to be able to very precisely determine the location of these points. Is this possible?

The position should be accurate to around 1/1000 of a revolution.
The changes in torque I am looking to detect are less than one mN M.
The servo should be able to turn with about 1.5 N m of torque when needed, although precise measurement and positioning is not required when it's doing this.

I've heard that servo load can be approximated by measuring current, but is this accurate enough to detect such small changes?

Would it work to somehow make the servo apply a very constant amount of torque, and infer load from the speed?


texts:
Wonder if someone can help identify this component.
I am certain it is SOT 23-3 after matching another component next to it. I Could be wrong. I think it may be a shunt regulator or something.
The 3V supplied to the pin comes from an LM2931A that provides 5V however there is a voltage divider in between to get 3V. 430 ohms and 680 ohms to ground to get 3 volts.
The 1.99V is the voltage sense and is calculated through another voltage divider from 67.2V. 33680 ohms and 1K to ground to give us 1.99V. The 1.99V Voltage sense goes into Pin 22 ADC7 of an Atmega 8A (32pin) as various input voltages can be used outside of the chip itself. Marked as G1, not C1. I am guessing this component might be an over voltage protection reading up to 2V or it will connect to GND. Cant be an NPN as it is a voltage sense that the atmega needs to know.
Does anyone know what this is?


texts: Setting a simple PWM on atmega328 at certain frequency

texts:
I'm having a hard time to set a 16 bit PWM on atmega328 that works with frequency of 50Hz and have a duty cycle that can be varied. I also have my doubts that if I can have an ADC working together with this 16 bit PWM since both use timer1. There are the auto trigger source selection ADTSX on the register ADCSRB that I supposed should be able to select the clock source for my analog conversion but I've setted and nothing changed, I couldn't have timer1 ISR and analog conversion at same time and I didn't tested for PWM and ADC together because I don't know how to set the PWM.

This is the code just for setting PWM that I've right now:

#include <avr/io.h>

int flag = 0;

ISR(TIMER1_COMPA_vect) {
  if (flag == 0)
    OCR1A = 11;
  else
    OCR1A = 160;
}

int main(void) {
   DDRB |= (1 << DDB1);
   // PB1 as output
  OCR1A = 160;
  // set non-inverting mode
  TCCR1A |= (1 << COM1A1);
  // set 10bit phase corrected PWM Mode
  TCCR1B |= (1 << WGM12);
  // set no prescaler
  TCCR1B |= (1 << CS10);
   while (1)
   {
   }
}

PS: I'll be varying the duty cycle between 1ms to 2ms activating an ESC controlling a brushless motor.


texts: How does "slightly" altering the physical construction of an antenna change its impedance?

texts:
Inspired by Phil's comment on this answer...

Bending the dipole to make it more like a V can also serve to get the impedance to 50 ohms.

Likewise, bending the ground plane leads for a 1/4 wave whip alters the the antenna's impedance.
Backing up a little bit, my understanding of antenna matching is to get the impedance at the feedpoint of the antenna equal to the impedance of the feed line.  With Ohm's Law being V=IR, the antenna should be (or can be) designed such that the voltage and current of the standing wave produces the desired impedance.
I have 2 closely related questions:

Specifically regarding Phil's comment, why does bending a dipole antenna change its impedance?

What's the "mental" model of how an antenna's impedance is determined?  I'm trying to get a better intuition of how slightly changing an antenna (like bending the ground plane leads) changes the impedance


texts: Is there a way to count the number of high inputs with logic gates?

texts:
I have \$2^n\$ inputs \$a_{0}, a_{1} .. a_{2^n}\$, these can be either hich or low, and \$n\$ outputs \$z_{0}, z_{1} .. z_{n}\$, these give out a binary number of how many of the inputs are high.
Is there any simple way to realize this without using half and/or full adders?


texts:
I wanted to build an electric lighter with a 9 V battery. I ordered 32 Gauge Nichrome Wire, a push switch and lots of 9 V batteries.

For testing, I attached aligator clips to the battery and to the wire. The nichrome wire only got a little bit warm, not hot.

I tested the voltage of the battery with a multimeter and it was arround 0.9 volts. The wire was around 1cm long.

What did I do wrong?


texts: LEDs lighting up while being baked inside a reflow oven

texts: This is a board with 80 3535 LEDs on it just after completing the reflow cycle in my home-made reflow oven. Why are the bottom corner LEDs lit up? Rather, how is this happening?


texts: Sending AT Commands to Remote XBee using python-serial

texts:
I have connected coordinator xbee to serial port of beaglebone i.e . tx and rx of beaglebone. My router's D0 pin is connected to relay. I want to remotely disable or enable the D0 pin. For that i am using python-xbee library. What I did is (my python code snippet)

myRouter='\x00\x13\xA2\x00\x40\xE4\x29\xB3'
#For Off
xbee.remote_at(dest_addr_long=myRouter,command='D0',parameter='\x04')
#For switch ON
xbee.remote_at(dest_addr_long=myRouter,command='D0',parameter='\x05')

code is working fine without error but I am not getting the output.
I tried it using without beaglebone i.e. using usb explorer it works. Here is the link of example @ digi.

I am using python-xbee library. What would be the error?


texts:
I am using an AT45DB081E 8-Mbit flash from Adesto (formerly from Atmel).  I am storing 7-byte data records and keep the location of the newest record stored in the last page of flash.  This value is occasionally read (about every 5 minutes) to see if it is different from the address of the next data record to be written.  This allows the microcontroller to check if any new data has been written to the flash or not.

The issue I'm running into is occasionally the location of the newest pointer is read incorrectly.  I'm wondering if reading from the same location over and over is causing some buildup of charge and contaminates the flash cells, but I didn't think flash memories had any limits on read operations.  I have submitted a support ticket to Adesto, but have yet to hear back.

Has anyone else run into this issue?  What have you done to work around it?  For now, I am reading the newest record location twice and making sure the values are the same.  All this did was give less of a chance of seeing the problem, but it still occurs (just less frequently).


texts:
From what I understand, the proof is suggesting that $$i(t) = (\frac{1}{R_1}+\frac{1}{R_2})v(t)$$ implies that replacing the two resistors with 1 resistor of value \$\frac{1}{R_1}+\frac{1}{R_2}\$ won't change anything and voltage across the equivalent resistor will be the same.

I don't understand why this is true. $$i(t) = (\frac{1}{R_1}+\frac{1}{R_2})v(t)$$ implies that if you replace the two resistors with 1 resistor of value \$\frac{1}{R_1}+\frac{1}{R_2}\$ and keep the current across the equivalent resistor the same as the sum of the currents flowing across the two initial resistors, the voltage across the new resistor will be equivalent to the voltages across the initial resistors.

In other words, the proof implies if you replace the two resistors with an "equivalent resistor", and force the current flowing through the equivalent resistor
\$i(t)\$ then the voltage across the equivalent resistor is \$v(t)\$.

Now in the example above, because of the independent current source, the current across the equivalent resistor is forced to be \$i(t)\$, therefore the voltage across it will also be \$v(t)\$. So for the example above, the proof is valid.

Now consider a more complicated circuit, where you have two resistors in parallel, but no independent current source (but instead its part of a more complicated circuit). Therefore if you replace them with an equivalent resistor, there is no guarantee that the current across the equivalent resistor will be equivalent to the sum of the currents across the original resistors, so the voltage might not necessarily be the same.

So why is this a valid proof for all resistors in parallel instead of only resistors in parallel with a independent current source regulating the current across them?

EDIT: I'm essentially having trouble understanding why the implication of the proof isn't the voltage across the equivalent resistance will be vp only if the current across it is identical to the sum of the currents through the two parallel resistors.


texts: Using sensors as an invisible barrier to doorway

texts: Recently I had a pet escape my apartment out the front door without anyone noticing. I was looking for a way to avoid this again by putting some kind of tracker in a collar and a sensor in a door way that will send a notification via ifttt to my phone or to my echo dot. I'm assuming I could do the notification with a raspberry pi but I have no idea what sensor or tracker I'd need for this. Any ideas here?


texts: How to switch a transistor when a radio signal is received?

texts:
I have a circuit which switches on by sending current to the base of one of its transistors. I'm trying to make receiver which can receive signals from a AM transmitter and send current to base of transistor so that circuit can switch on the circuit. I know how can I make AM transmitter. Given that I cannot use any receiver module/chip etc, please suggest a simple circuit design which can serve the purpose.

EDIT: I need a receiver with minimum range of 500-700meters. I have made this AM transmitter. As stated above I'm not trying to send audio signals, the circuit stays on as longs as current is passing through base of transistor. I want the circuit to stay on as long as transmitter is sending signals to receiver. What modifications I have to make in transmitter circuit for that.


texts: Active rectifier and its slew rate limitation..?

texts:
Please help me on this....

The following circuit is of an active rectifier..The inclusion of a diode here signifies a voltage follower for positive Vin voltages ....but for negative Vin diode is off hence the out voltage Vout is zero....and the output of the opamp goes into negative saturation (opamp sinks current for negative Vin cycle)...But here comes a certain slew rate limitation of this circuit...with high-speed signals.The op-amp cannot swing its output infinitely fast, the recovery from negative saturation takes some time, during which the output is incorrect...

In order to deal with it and improved version of the circuit consisting of two diodes is employed as shown in figure 2..
The text says that "The improvement comes because the op-amp's output swings only two diode drops as the input signal passes through zero."...

What does that means...?


texts: Frequency-to-Voltage convertor diagram questions

texts:
I'm relatively new to electronics, but I'm interested in making the Frequency-to-Voltage convertor linked here as part of a larger project linked here.

Here is a diagram of the circuit I want to make:

(Image source: Math Encounters Blog)

Whilst the diagram seems clear enough for me in most places, there were a few things that I would really appreciate if someone could clarify for me:

What is the .tran 10 transistor referred to at the bottom of the diagram?
In the "Larger Project" I linked above, I assume that the positive and negative of the audio signal would go correspondingly to the positive and negative of the "Sensor Interface Output" part of the diagram; is this correct?
I assume that the "Supply Voltage" is, as it hints, a constant voltage needed to supply the circuit. If so, what would this voltage be? 5V? 3.3V?

I would be very grateful if someone could give me some guidance regarding the 3 questions I posed above, as I am new to this sort of electronics.

Thank you in advance.


texts:
I'm Vuong Kha Sieu and i'm 14 years old. I have a great interest in electronics and I wish to seek your help about this question. Please forgive any grammar mistake I made, since I'm not a native Englishman.
Let's assume we have a thyristor with cathode at ground level, anode at 12V. Now we take a 9V battery, connect it (-) terminal to ground, (+) to gate then the thyristor turns on. After that we remove the battery and insert a voltmeter instead, what value shall the voltmeter will indicate??
Sincerely,
Sieu


texts: Is paying extra for "Controlled Impedance" boards necessary?

texts:
I'm doing a bit of RF PCB design, and one of the things that caught my eye is the "Controlled Impedance" option. Checking more boxes always costs more, so I want to know if this is worth the extra money to ensure functionality on arrival. For the RF portion, I'm using 50 ohm microstrip-line on a 4 layer board. (Top layer [1] is signal, top inner layer [2] is a ground plane)

Most board vendors have made their laminate stack-up contents and thicknesses available on their website, and I have been able to calculate the width of the transmission line to my satisfaction using their numbers.

What is the benefit of using
"controlled impedance" or "controlled
dielectric"?
At small distances (about 1/10 wavelength), would the impedance bump matter? (I get about 2 ohms difference in Zo from changing the dielectric constant by +-0.4)
Is this something that should be done for production boards but isn't necessary for one-off prototypes?
Have you ever used this feature?


texts: What is the different bewteen the minimum attenation in butterworth and Chebyshev filter?

texts:
I have desgined n of a low-pass butterworth whose specification  are  fc=1khz , fs=2khz, Amax = 1 db and Amin=40 db. I found that I need to make sure the n gives me larger Amin which = 40db. So I found n = 8 which has A(ws)=42.2db
In other side, when I designed a Chebyshev  for same specification I should find n that gives me A(ws) larger than 20 db why not 40db ? I found n = 3 which have A(ws) = 22dB
I am confused why I do not use n= 5 which have A(ws) = 45.31 db.
I found in some books this sentance "The Chebyshev  reponse rolls off at an ultimate rate of -20db/dec, just ike a Butterworth reponse of the same order" I think this is related to what is above. but I do not understand it. Could you please clarify it.


texts: Reverse voltage protection using N channel MOSFET

texts: I was looking for a reverse voltage protection for the 100 ohm load in the circuit using an N-channel MOSFET, this is my design. The Zener diode is for gate voltage and of 5.1 volts, assuming the MOSFET wont turn on if the gate voltage is 0.7 volts, is the schematic topologically correct? (actual MOSFET parameters may not match)


texts: can I hard wire the output power of a eu solar inverter to a us breaker panel/

texts: I have a hybrid solar Easun inverter/charger rated power 3000va/2400w 230vac 50/60hz self sensing. The unit is set up with single EU 230v self sensing 50/60hz input to charge battery and the output is also single EU 230v self sensing 50/60hz. I wish to use this system as a back up for when the grid goes down and to trick my Solaredge 7600 grid tied inverter into thinking it is tied to the grid so it will turn on when the grid is down and or panel main breaker it switched off and back up breaker is switched on. My question is... Can I convert the EU output to US by connecting the blue and brown output wires of the Easun inverter to the 2 wire 230v breaker (L-1 and L-2) in my US panel box without hooking up the EU ground, trick my Soleredge inverter to turn on as it does when grid tied and maintain 110v to my normal house outlets?  If I cannot connect the Easun inverter this way does anyone know how it can be done, with or without a converter between the output of the inverter and panel breakers input and vice versa.


texts: Control board powered up with reverse polarity. power transistor blown. Is this repairable?

texts: My dog chewed through the power cord. I 'repaired' it not paying attention to polarity. It was a 2A, 9V wall wart type power supply. The motherboard is from an elliptical exercise machine. The one transistor got obliterated. I thought it was going to be hard to remove and replace but when I snipped the 3 legs, the destroyed transistor and a thin thermal pad it was stuck to pulled off. I'm assuming that the black blobs came from thermal grease or similar? Anyway, is this even worth trying to fix? I can solder a bit and can get that same part, but the thermal pad (and its destruction) stuff is new to me. Thoughts appreciated.


texts: What method do wireless routers use to break apart the received wave into different frequencies?

texts:
What method do wireless routers use to break apart the received wave into different frequencies ?

Does it have anything to do with Fourier Transformations ?


texts: I am using multisim to simulate an inverting summing op amp (LM741CN). I calculate my expected Vout to be the following: -Vout = ((20/2.5)V1) + ((20/5)V2) + ((20/10)V3) + ((20/20)V4). According to my calculations, my Vout with binary input of 0001 should be -1. However, when I measure in Multisim, that is not what I get. Are my calculations incorrect or am I measuring incorrectly?


texts: What is wrong with this butterworth filter, how can it be improved?

texts:
I have designed a 6th order butterworth low pass filter with 20KHz cut off frequency using Sallen Key topology (thanks Andy Aka). The filter is behaving as expected with the cut off frequency and roll-off however, several order of magnitude above the cut off frequency something happens with the frequency response that I do not expect.

Why does the attenuation reduce 110KHz and then become stable after 1MHz?

EDIT:
Today I did some more simulation. I used 2 nonideal opamps and it gave me similar result. Then I used what I consider to be ideal op amp in LTSpice. The symbol is called "opamp" and needs a spice directive to be useable. The result is below:

I initially thought that the ideal opamp does not suffer from the problem I saw with the real op amp. It is true that it does not. However, between 0.6GHz and 0.7GHz I notice a strange behaviour. This is different from what was seen earlier.

I have scaled the values by 10. All R divded by 10 and all C multiplied by 10.

I have now scaled the values by 10 the other way, i.e make resistor bigger.

Edit II:

As requested by Guru I now have more graphs:

Plots with ideal op amp with impedance scaling; upto 10MHz limit.

Plot of the original circuit with an extra RC at the end:

Plot with the OP275 as required by the Guru:

Finally plot of the original design but with buffer in the feedback loop:


texts: Common Mode Rejection Ratio vs Common Mode Voltage

texts:
I'm currently comparing characteristics of some different amplifiers, specifically their CMRR, and I came across this amplifier, which rather than listing an explicit CMRR, merely says:

Maximum Common Mode 1.2 V

As it is, I can't find a CMRR listed anywhere on the website, is this an equivalent statement for CMRR? If so, how would I calculate an equivalent CMRR from this seemingly uninformative statement? I've done a google search and a search on here for any information regarding expressing CMRR as a voltage, but so far no luck


texts: I have read that a significant drawback of telephone lines, one that makes difficult fast digital data transmission is the fact that they are inductively loaded. Now in telephone ADSL lines, are these inductors removed?


texts: I would like to transmit data over the ionosphere with a specific frequency (that will enable the radio waves to bounce on the ionosphere), this frequency might be about 30 MHz. I am wondering how much data will I be able to transfer with this frequency ?


texts: PC recognizes keyboard pcb only as FT232R usb UART but doesnt see atmega32a behind it

texts:
I made my own pcb design for mechanical keyboard. When I wanted to test it, both mac and windows system recognize only FTDI ft232rl chip on pcb but not atmega32a behind it that controls whole keyboard. I installed all ftdi drivers but nothing changes.
What should I do or try next?
-rgb diodes are working, I mean they flash white light, probably feeling 5v usb input, but in firmware default color is white also.


texts: if a standard three-phase 400V AC connection is rectified what DC voltage comes out of it?

texts:
If a standard (in Europe and a large part of the world except North America and Japan) three-phase 400V AC (three lines having 230V RMS voltage if measured to neutral each) mains supply is rectified with a standard 6-diode rectifier like this:

What DC voltage value will come out of the rectifier? How to calculate it having the RMS AC source voltage given?

Are there any other ways to wire diodes to get a different voltage (without using any transformers or anything else then just diodes), what are they and what DC voltage will come out then?


texts:
I bought a random thermistor for a circuit I'm planning to build and it turned out to be a NTC 5D-15.

I'm trying to build this test circuit:

After doing a bit of research, that thermistor resistor value is 5 ohms so I have no resistors with close values so I tried my lower valued resistor and the reading didn't change much regardless of the temperature.

Do I need a resistor very close to 5 ohms to get correct readings?
Isn't the resistor value too low to be able to get correct readings?


texts:
I have an ESD mat and wrist strap.  The wrist strap plugs into a little box that beeps when either the mat or the wrist strap do not have a good connection to ground.

I also have a standard Phihong 5V wall wart.  I have noticed that when the wall-wart is plugged into a device, and the device is sitting on the mat, the box indicates a fault with the mat.  If I touch an exposed ground pad on the device, I get another fault indicator for the operator, as if my wrist strap is improperly grounded.

If I attach a serial cable to the device, this problem vanishes.  I assume this is because the serial cable somehow provides a proper ground to the device.

This happens even if the device is off.  However, the wall-wart is still active; if I turn the wall wart off by flipping the switch on the surge protector, the problem vanishes.

The problem also appears sometimes when I merely approach my mat with the device connected, without even necessarily touching it.

Is there an explanation for this odd behavior?


texts: is the intel quark capable of running an opencv webcam unity application for linux?

texts: I built a fairly simple application in Unity that uses a webcam and opencv to overlay graphics in realtime to a user's face. I am looking for a low cost microcontroller/computer to run the installation and output it to a monitor. I was originally thinking Pi but Unity will only build for x86 architecture. I saw the Udoo x86 but it is ~$200. The Intel Quark seems to be x86, but I'm not sure if it could handle the graphics. Does anyone know if it's possible on this board? Or what specifications I should look for to determine this?


texts:
I have a circuit that runs on 1V up to 15V DC. I want to attach a low-power battery-level (1.5V) device to this supply rail, and have it work over the broadest input range possible (yes, it will cut off before 1V most likely, but I’m okay with that). The device cannot take an input of more than 5V, and preferably I’d like it to not go higher than 2V or so.  It draws on the order of 1µA or less current.

It seems like one simple way to accomplish the goal of limiting voltage and operating as close to the low end as possible is to put a JFET (N-channel) between the supply and the device, with its gate tied to ground.  If the JFET’s threshold is around 2-3V, then once the supply (drain side) goes high enough, the JFET’s resistance will go up, keeping the source side from going higher than about 2V above the gate (ground), and there will still be enough current to power the device. On the source side (i.e. where the device is) I can put a resistive load if the draw isn’t consistent enough.

What I’d like to know is if there is any obvious flaw in this plan, or reason that it might not work as intended. Of course this is highly dependent on the variable pinch-off voltage, but bear in mind I don’t need a precise level; just a way to make sure the voltage doesn’t go too high for the device. I’m only making a few of these, so I can likely tweak a too-high threshold with the load on the device side; I can easily spare up to a few 100 µA without it affecting the rest of the circuit.


texts:
EDIT: My reference in this question to analogue voltages are just how my voltmeter reads and averages the PWM from the Microbit.  Apologies if I'm confusing the matter with this.  The project is using PWM with a varying duty cycle.

I'm trying to power a strip of 12v 5050 LED's using the circuit below.  I'm changing the output of the Micro:bit between 0 and 1023 in steps of 128 to get 9 levels.  At the MOSFET gate I'm getting between 0 and 3.14V in steps of 0.4V and without a load I'm getting between 0 and 12.16V at the drain in steps of 1.5V (the first step is 2V and the last step 0.95V but I assume the response just isn't quite linear).  When I connect the LED strip the drain voltage drops to about 40% of what I am expecting i.e. 0 to 4.75V which makes the LED's barely visible. Can someone explain why this is please?  The power supply is rated at 12v 3A so has plenty of capacity.  The LED's shine at full brightness when connected directly to the power supply.

My electronics knowledge is very basic - some 30+ year old school physics and a lot of Googling so feel free to respond using "for dummies" level answers.

simulate this circuit – Schematic created using CircuitLab


texts:
Im trying to analyze this piece of circuit and the feedback between the second transistors emitter to the base of the first transistor is confusing me. Does anyone have any ideas how to analyze the input/output characteristics and frequency response with it?

Thank you in advance!


texts: SMD desoldering - struggling to get this chip quik stuff working, what am I doing wrong?

texts:
So I have to replace a SMD connector, and although i do have soldering experience, it's all with THT. I watched like 10 different YouTube videos on chip quik, and they all made it look so easy, so i figured I'd give it a try.

I've been trying to practice on an old junk motherboard first, but it feels like I must be doing something wrong.

First, I've noticed that it's pretty much impossible to tin the tip with chip quik, so I've tried both without tinning and tinning with normal solder, with pretty much the same results.

The way SMD soldering is applied with the tip is very new to me. I cover the joints in flux, but when I try to spread the solder out like they do in the videos, it just balls up and doesnt want to stick to any of the pins. I know this issue is usually caused by the joints not being hot enough, but none of the people in any of the videos heated up the joints, they just spread it out over the pins and kept it molten while they pulled the chip off.

After being very delicate, I managed to get the solder distributed over the joints, but when I try to make a second pass to keep the solder molten, it just balls up and pools wherever I put the iron, repelling away from many of the joints.

I have tried messing with my iron temp anywhere from the range of 250c to 400c with pretty much the same results. Have also tried both cone tips and chisel tips.

Could it be a problem with the quality of my tips or am I doing something wrong? It was a really cheap soldering iron but had great reviews and hasn't given me any problems yet. All of the tips I used were either new or only used a once or twice. I know theres probably some better quality tips out there but I'm not even sure how to find ones that fit. Most of the good ones seem to be for Weller irons.

Any input is greatly appreciated. I managed to successfully remove 1 SMD chip so far after some struggle, but all of the other attempts I couldn't even get it to budge.


texts:
I'm using STM32 VCP firmware on STM32F4 discovery. I generated the code with CubeMX and I could successfully integrate it into my Eclipse project. After calling the initialisation functions, the device appears on my PC as virtual com port, so the drivers are fine.

But where can I find the functions in the library, which do the trasmitting and receiving data on the STM32 device? I know this is a very basic question, but I'm looking for them for a long time.


texts: How can i connect two different pots parallel like a normal pot?

texts:
I am trying to make an adjustable power supply with XL4016 module and 24 volt 6,5A SMPS.

I can adjust volt with two pot (fine-course) because it needs two pins. But I couldn't think how to design a coarse / fine replacement for the current pot because it needs three pins for pot. I need middle pot pin too.
How can I connect two pots in place of a normal pot. The module wants to 10k pots.


texts: Corona Discharge Current, Atmospheric pressure discharge!

texts:
There is an atmospheric pressure load (coaxial cylinder and copper wire as main electrode) which high voltage pulses by a Linear transformer driver (LTD) has been released to it.
I think a kind of corona discharge will happen in atmospheric load after applying high voltage pulses. Discharge is happening after breakdown by high potential electrode.
Question: Why if we release two continuous voltage pulse (50ns, 15kV pulse and then after 100ns another 50ns, 15kV pulse), The peak of discharge current in the first pulse is almost twice than 2nd one?
and if we increase the distance between pulses like as (50ns, 15kV pulse then after 1ms another 50ns, 15kV) the peak of discharge current in two pulses are same as each other.
Can anyone explain the relation between time and discharge current in this kind of discharge?Why when distance between pulses are far, the discharge currents have same peak?

Thanks for useful replies. I have to mention some points.
1st of all here in following link (Blue colored phrase) you can see the source of energy.Pulsed Power Generation by Solid-State LTD, It is a linear transformer driver which has 30 modules. These modules have capacitors and MOSFETS as switches and modules are connected inductively and voltage multiplication by inductive voltage adding is our output energy
Please read if you have time. I think the source of energy does not have much effect on the explained results because I have tested the experiment with Resistor as load not this atmospheric discharge load. In resistor case the current peaks are almost same even in 100ns distance. But when it comes to this atmospheric discharge load (A coaxial cylinder and copper wire) current peaks are different in close distance as 100ns. But still I am not sure, It might be some effects of energy source. Our LTD (source of energy) is working based on inductive voltage and we have core and magnetic field there. Would be any effects of core saturation or B-H curve? Simplified picture of load is in here.
If I try to circulate the air, would I receive any different results.
It would be very helpful if you explain/give hints/introduce some useful sources of information on relation between time and current peaks in this case!
Thanks for your time!


texts:
I am trying to make sense of the difference in non-inverting and inverting op-amp based audio "mixers". The circuits are basically summing op-amp amplifiers. Here is the part which I do not understand. (Figure from simulations below)

I simulated both and the main difference is that in the non-inverting case, the other sources act like shorts, but in inverting configurations they do not. Why is that so? Can someone explain?

So basically if I am summing 3 signals from sources and only one is generating a sinusoidal signal with 100 mV amplitude, I get 33 mV at the output of the non-inverting configuration and in the inverting case, I have 100 mV at the output. Why?


texts: How can I make connection on pcb (circuit board) holes without solder (for prototyping)?

texts:
I have a Pro Micro board (very small -- see pic below) and it has connector holes in the printed circuit board.

Best Non-Solder Connection (Easy and Removable)

I'm wondering the best way to make non-solder connections for doing my prototype work.  By best, I mean easily removable while maintaining solid electrical connection.

Are there pre-made connectors for this type of connection?

What Part Is Most Conductive / Best Electrical Connection?

Also, how can I know I have a good connection?  Is it the inside of the hole that has the conductive metal, outside of hole?

Front / Back Separate Traces?

And, are the front and back of the holes electrically connected normally or do they have separate traces normally?

One Idea: Would It work Very Well?

What if I had header pins pushed into a breadboard and then up through those holes?  Then I connect my wire to the top of the header pin?  Would it be a solid enough connection?   Or would it not make enough electrical connection?

ie - would header pins make connection inside of holes and would that be enough electrical connection?

Edit -- I Wish They Made Banana Plugs That Fit This
Wouldn't it be cool if you could use a banana plug type of connector.  Then just plug in each one and put wire in hole and clamp it down?

UPDATE 11-11-2017
Interesting that in the time since I've posted this someone came up with a solution similar to what I was thinking with banana plugs:
Hammer Header Male - Solderless Raspberry Pi Connector
It's really for use on a RPi Zero but it's the type of snap-on header I was interested in at the time.

However, the installation is not easy so it may not be practical.
Take a look at what you have to do to install it :
https://learn.pimoroni.com/tutorial/sandyj/fitting-hammer-headers
Probably easier to just solder on the header pins.


texts: Intermittent Pulses in Anti-phase Step Generator

texts:
I've recently been studying some old circuits, in particular some of the Heathkit circuits and I'm currently looking at this one: IT-1121 Curve Tracer.

Here's a snippet of the step generator which I'm having some trouble with:

The problem is that the pulses from the collector of Q5 are intermittent, but come and go to a pattern.  You can see the pattern clearly when you adjust the oscilloscope timebase to see the pulses over a longer time.  The sketch below shows the pattern:

I'm speculating that the signal crossings are somehow being phase adjusted and are gradually moving upwards and away from the 0V reference point.  This explains the gradual fall off to zero in the pulse pattern.  But I'm not sure.

So, my questions are:

1) What's really happening here and is it "phase jitter" that causing this or something else?

2) If it is phase related, how can this occur since the anti-phase signals are generated off a centre tapped secondary (not quite as specified in the Heathkit circuit, but not far off)?

3) Is there any way to cure this?

UPDATE: I found the problem.  It turned out to be an issue (bug?) with the DSO.  With a longer timebase, unless the acquisition memory is set > 4k the display ONLY shows the undulating pattern in the pulse signals and not the remaining part of the pulse.  The full pulse is shown if the memory is increased.


texts:
I followed this schematic to build an H-bridge:

http://www.pocketmagic.net/2009/03/a-simple-h-bridge-design/#.UqjoLFXxteW

Now, when I first switched it on, I was surprised that the transistors became really hot. I searched for a short in the circuit, but didn't find one. Upon further research, I discovered this was caused by both of my logic inputs being high. Now before this I used an integrated circuit, which had a braking function associated with this input combination. Is it possible to add this functionality to the circuit above and how would I go about doing so?


texts:
I am using an optocoupler and a power triac to switch 120VAC supply to an ~108 watt fan. The datasheet for my optocoupler requires me to snub the optocoupler output when I'm switching an inductive load (which I'm guessing an AC fan is). Why?

I can see you might want to snub the fan itself if you're switching off/on frequently and you don't want the initial voltage and resulting EM spike, but I don't know why I should care to snub the relatively low current through the optocoupler outputs.


texts: Powering a switching power supply with a CTE (centre tapped earth) transformer

texts:
This question is an extension of a previous topic I posted regarding CTE transformers.
I plan to use a switching power supply for an upcoming project, and I want to supply power to it from a CTE transformer. See spec sheet for PSU.
As discussed in my last post, CTE transformers have no neutral output. Instead, they have three contacts, where one is ground, and the other two alternate between -55V and +55V such that the voltage difference between the two contacts is +/-110VAC. The PSU, on the other hand, has a "L" and "N" contact for power. Based on the PSU's spec sheet, 110VAC is well within the input range, and I'm assuming that as long as the voltage difference between the "N" and "L" contacts is in the specified range, the device will work.
Am I correct in this assumption? Or am I going to ruin my PSU?


texts: Power calculation of a transformer using only current and resistance

texts:
If I use \$P = I^2R \$ for primary and secondary will that tell me the effective power being dissipated? Uf I divide secondary power by primary power and multiply by 100%, would that tell me the efficiency of the transformer?

I haven't considered the voltage or phase angle of the primary but since the inductive impedance is allowing the power to return to the source is it okay that I do not consider it in my efficiency calculation?


texts: Is there a network mapping tool for path-loss?

texts: I am not sure if this is the proper forum. I am looking for a tool to evaluate the wireless network performance.For example, given a map where should I put a transmitter/or transmitter plus repeater so that the map area is covered by the transmitter. Another example may be given a map and a transmitter location how the signal strength will vary at the different locations of the map?


texts: How to reduce voltage from a battery to a motor

texts: I have a 14.8v battery and I want to run a motor on 13v. What is the best solution to reduce the voltage from 14.8v to 13v?


texts:
In the explanation, it explains that C2, C3, C4 are for frequency compensating the impedance of C1 which varies according to frequency.

Can someone explain how C2~C4 does it? and why the designer chose particular value for the three capacitors? It seems that he wanted to proportionally match the parallel connected resistor in terms of impedance, but I don't understand why.

Thanks


texts: Is it possible to pulse on a LED strip as the warp engines do on Star Trek TNG?

texts:
I'm trying to activate a LED strip in the same manner and sequence as that of how the activation of the warp engines on the Enterprise in Star Trek TNG.
When activated the following happens-

LED rises in intensity. (hoping to have the rate of this step be adjustable)
LED reaches an intense set peak brightness momentarily (a flash just as the engines pulse on the Enterprise as it moves into warp).
LED brightness output decreases back down to nominal output.

Is this possible and if so how?
Thank you in advance.


texts: Is my understanding of this level shifter correct?

texts:
I am considering using this TI LSF0102 level shifter in my circuit - but would like to understand, based upon its datasheet, if I have my understanding correct.

My aim is to be able to supply 3.3V and shift it up to 5V, in the case that my input is LOW, then my output should be LOW. It needs to handle at least 61.5mA of current, and I need to be able to control 4 channels (in this case I would buy 2 of these chips for this purpose).

I believe I can do the following in the 8 pin LSF0102 DCT or DCU Package.

Pin 1 - GND
Pin 2 - vRefA == 3.3V
Pin 3 - A1 -- input channel 1 (in this case could be 3.3V)
Pin 4 - A2 -- input channel 2 (in this case could be LOW)
Pin 5 - B2 -- output channel for input 2 (in this case would be LOW)
Pin 6 - B1 -- output channel for input 1 (in this case would be 5V)
Pin 7 - vRefB == 5V
Pin 8 - EN = Switch enable input; connect to Vref_B and pull-up through a high resistor (200 kΩ)

I am not sure of the purpose of the EN pin, how is it acting as a switch? How does it work? Additionally, are my other understandings correct?

Is there a better alternative chip for my purpose?

Many thanks!


texts: Alkaline battery performance at -30 Celsius

texts:
I am making an IoT project and planning to power it with alkaline batteries. Their safety and low cost are really appealing. Their low discharge capability is not a problem. The batteries need to be able to supply 500mA to a boost converter, but for only seconds every week. For all the time other than those few seconds, the batteries have to supply around 10uA.

My only problem is the temperature. The device needs to operate at -30 celsius temperatures. I can't find a comprehensive source for the effects of alkaline batteries operating at that temperature. An example of lower temperature performance is in the graph for the Duracell AA Coppertop:

The loss in energy doesn't look too bad there. Another source is less optimistic, especially at lower temperatures like my required -30C:

In ideal conditions, the batteries will last years based on the current draw of my project. However, when it's the coldest month of the winter and they have to endure an average of -10C with a minimum of -30C, I could accept if they survive only 1 month. Also, they still have to be able to provide up to 500mA. Based on this graph,

It seems likely that with internal resistance changing from 0.2 ohms at room temperature to 0.5 ohms at -30C, that is probably possible, but I'm not sure about this either.

TLDR

I would appreciate someone with experience with alkaline batteries giving their opinion on the feasibility of alkaline batteries surviving the -30C minimum, -10C average temperature for at least a month, while being able to source 500mA for a few seconds. Not all batteries are created equal, so maybe some alkalines will be capable of meeting my needs while the average isn't?


texts: Is it possible to emulate an SD as a slave?

texts:
What I want to do is put a dummy SD card (the connector going directly to the device with a cable going to a micro controller) into a device so that when the device tries to write a file the micro controller can intercept it and write it to another location, and then when the device wants to read it you can emulate the files that are supposed to be there except that they are stored on the micro controllers side.

Is there such a project that already exists? Is this even possible (i assume so as thats how most USB sticks work, kind of)? What would I need to do this project?


texts: Single Resistor on Common Cathode Display Is Not Limiting Current (With 1 segment lit)

texts:
Today I did a little test and hooked up my arduino nano to a seven segment common cathode display.

I attached a single 1k resistor to the cathode pin of the display, and then lit a single segment with the 5V pin of the arduino nano. I probed the resistor leads with a multimeter to check the current.

Turns out this did not limit the current at all. Why could that be?

Update: Well I now notice that probing the resistor seems to be causing a short, because the current SHOOTS up like a mother* whenever I probe it. How should I go about measuring the current?


texts: How to determine the best resistance for a weak signal Twin-T notch filter?

texts:
I am designing a 50/60 Hz Twin-T notch filter for a weak (biomedical) signal output from an instrument amplifier (InAmp) to be chained to another active low pass filter. The input frequency range is between 0.1 Hz to ~200 Hz.

Image credit: here

I have come across several designs, using widely different values for \$R\$, often ranging from \$100\ k\Omega\$ to \$10\ M\Omega\$.

I'm getting a quite confused about how these values are best chosen.

On the one hand:

It has been stated that perhaps the circuit would draw less current, but I don't see this, as there is no obvious current sink between the input and the output.
That there is some kind of impedance matching going on. Impedance of what? (The InAmp output or the OA input?)
It may be easier to find matching capacitors when using a larger R, for a given \$f_c = 1/(2 \pi R C) = 50\ Hz \$

On the other hand:

There may be significant thermal noise, for higher R as given by:
\$V_{n(rms)} = \sqrt{4k_BT R\Delta f} \approx 1.623\ \mu V\$ (for R=2.6M, C=1n)
thus approaching that of the signal itself, \$ <100 \mu V\$.
Similarly, using larger R, implies using a smaller C, subsequently increasing the capacitor thermal noise too.
Then I suppose there are all sorts of other noise types (such as 1/f) to consider, but whose relevance to R is not clear.

As you can see, my mind is already clipping long before my signals do.

How can I sort this out to better understand what values for R (or C) to use?

UPDATE

So far it seem that the best choice is trying to keep R as small as possible within reason, probably within 100 kΩ ≤ R < 1 MΩ. This will have the following consequences:

Reduce the thermal noise
Increase the value needed for C, also reducing noise
Noise \$V_n \propto\ \sqrt{I}\$ which implies that SNR improves as well.

What else:

C values are the most limiting, since they are only readily available in the E12 value series, whereas R is in E96 (and even E192.)
C should be > 1 nF due to possible PCB stray capacitance.
C should be of polyester or Mylar type.
R should be of type metal film @ 1% for lowest noise.
I/O impedance is irrelevant, because of the previous and subsequent use of InAmp & OpAmp.
What about RF filtering? (4/5G mobile phone nearby?)


texts:
In one book I found that snippet. Can anyone explain me why the input may go below 0?

There is a text with that pic: "The limit here is one diode drop below
ground, at which point the base of Q3 will forward-bias against the substrate." Why one-diode drop is a limit? Why not two diode drops?


texts: How can I increase the multiplier of a voltage doubler circuit using IC4049?

texts:
I replicated a voltage doubler circuit from this example I found online:
... and as expected, I am getting 12V from a 6V input.  I would like to increase the multiplier to more than 2x, but I am having trouble understanding how I can connect a second IC4049 to do so.  My attempt was to hook up the second IC4049 like so:

pin 1: 6V
pin 8: GND
pins 3, 5, 7, 9: pin 11 of first IC4049
pins 2, 4, 6, 10: negative leg of C2

The output across C3 is still 12V, so it doesn't work.  What is the correct way to connect the two ICs up?


texts: Control the base of a transistor (Current limit)

texts:
I looked at another question here and saw someone talking about different LM317 current limiting methods, and in one of the comments he uploaded this image:

But no one answered the comment and I'm also really curious if this would work? I tried it on a breadboard and it worked exactly as i wanted it too, Any downsides with using this?

Link to other question: Smartest way to use current limit using LM317?


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I am trying to use an electret mic with beaglebone. Instead of making a preamp, I am using a locally made 'audio board'. This is the instruction slip that came with it :

However, I do not understand how to connect an electret mic to this. The "1 core pickup wire to V.c" is supposed to do the job. I'm attaching a picture of the wire :

I tried connecting the outer strand to the ground of the electret mic and the inner strand to the other terminal. The blue wires are supposed to go the speaker. I connected one to the ground of the beaglebone and the other to an analog pin. Reading the pin did not give me any meaningful results (yelling at the mic didn't increase the value).

Assuming (arbitrarily) that the problem is not with the BBB, can I be wiring the audioboard correctly? I gave 6 v power supply to the board. In any case, I do not understand how my configuration (outer strand ground, inner strand other terminal of mic) can be equivalent to that in the instruction (there are sort of 3 lines in the diagram, and a resistor). What, do you think, could be wrong here?


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I am beginner in electronics, I am wonder about microchips that can transmit data between themselves using Bluetooth.
I want to play around with them like the estimate connection, send data, receive and close connection using programming.
I am totally dummy in this area, but I desire to learn it apply my programmers skills.
Could you advise me what to read about such transmitters?
Where to buy them and how to start working?


texts: Parallel transformer output not expected RMS value

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I have a 115V/230V transformer with specifications of: outputs 10V (parallel)/20V (series) and 1.2A (parallel)/600mA (series). Product

I'm no electrical engineer, but I need to get this set up to power my first hobbyist project. The reason for purchasing this particular transformer was due to height restrictions.

From what I understand, I can set this transformer up with 120V in parallel by connecting pins 1/3 to LOAD and 2/4 to NEUTRAL. If I then hook up pins 5/6 and 7/8 in parallel, I will get 10V/1.2A output.

I have a cheap oscilloscope that I am using to measure the transformer output. I hooked it up to the test leads (2Vp-p 1kHz square wave) and it looks like it's working.

simulate this circuit – Schematic created using CircuitLab

When I hook up to the transformer output, I am not getting the expected A/C sine wave. Instead, it looks like the sine wave is cut off at the 5V mark. The measurements are 10.3Vp-p, 4.81 Vrms 60.02 Hz

Is my oscilloscope incorrect or is this the correct output for a 10V parallel transformer? I was expecting a 10 Vrms output (with peaks up to 14.14 V)

I also have a similar 9V AC transformer (single primary single secondary) that produces a similar output. Are my assumptions incorrect about these transformers?


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I am developing an application for a University project on my STM32L1DISCO board with the STM32L152RC MCU.
I have configured the pins and generated the init code via STM32CubeMX. I am using Atollic TrueSTUDIO as the IDE.
The problem is that the generated init code cannot run on my MCU. After spending a lot of time on debugging I found that the problem in the code is this one line using the HAL gpio library:
HAL_GPIO_Init(IDD_CNT_EN_GPIO_Port, &GPIO_InitStruct);
Even though the preceding code is correct,
  GPIO_InitTypeDef GPIO_InitStruct;

  /* GPIO Ports Clock Enable */

 __HAL_RCC_GPIOC_CLK_ENABLE();

  __HAL_RCC_GPIOA_CLK_ENABLE();

__HAL_RCC_GPIOB_CLK_ENABLE();

  /*Configure GPIO pin Output Level */

HAL_GPIO_WritePin(IDD_CNT_EN_GPIO_Port, IDD_CNT_EN_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin : IDD_CNT_EN_Pin */

GPIO_InitStruct.Pin = IDD_CNT_EN_Pin;

GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;

GPIO_InitStruct.Pull = GPIO_NOPULL;

GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;

After stepping through the code line-by-line during debugging, I found that the HAL GPIO Init function does not execute and instead gives the runtime error: "Target not Responding, retrying...".
When I comment the HAL GPIO Init line, the program runs through with no issues.
STM32CubeMX includes the HAL library in the code. On top there is,
include "stm32l1xx_hal.h"
So, I'm not sure what's causing the issue I'm seeing. I would really appreciate your help on this as I don't know what to try next.
Thank you.


texts: Issue understanding pin functions of a programmable current source from manual?

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Here is the link to the manual: https://www.analog.com/media/en/technical-documentation/data-sheets/3092fc.pdf

I am confused about the pin functions, in particular IN and SET (page 8). I gathered that OUT needs to be the current produced, but from the written definition I can't tell the difference between IN and SET.

Is IN just the power going in? In which case, would I provide it 2V and 1mA as specified in electrical characteristics?
And so, would SET be the digital input which switches the component on? So I'd get no OUT as long as SET is 0?

Sorry if they are stupid questions.


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I'm working on a layout in which two chips connect to each other through a 1x PCIe bus. The two chips are on one board.

One of the chips is the Xilinx Spartan6 LX75T so I've been working with the Spartan 6 PCIe User guide http://www.xilinx.com/support/documentation/user_guides/ug672_S6_IntEndptBlock_PCIe.pdf and on page 200 The guide specifies for Chip-to-Chip designs AC coupling capacitors CAN be placed anywhere on the interconnect. This implies that AC coupling is not necessary on chip-to-chip designs.

From my research I believe that the AC coupling is required to isolate the high impedance receiver inputs from any DC offsets that may be introduced by plug in cards. Which makes sense, if a PCI express card were to be plugged in and the TX lines had a DC offset that was different from the host board then it could send a common mode voltage that is out of spec for the receivers, but if I'm sure that this situation will not happen because my signals are between two chips then it seems as though AC caps are not required.

This seems a somewhat trivial problem because it's just two extra caps on the board but if I can avoid them then I also cut down on the vias required to route these traces thus reducing the attenuation on the signals.

Am I missing something? Or is it alright to remove the AC coupling caps for the TX lines?

Dave