texts: What is an analog meter (volt/ammeter) with the needle in the middle called?

texts:
I am making a demonstration which requires me to have access to a small extension that helps me prove Faraday's Law of Induction actually induces a current in a circuit. I want to get an analog volt or ammeter that has the needle in the middle allowing it to go both positive and negative to show that waving a magnet from side to side produces an AC current.

How is this type of meter called? I can only seem to find analog meters that go from zero to positive on amazon and the likes.


texts: Troubleshooting DC motor no load current with power supply

texts: I am trying to characterize a DC motor I harvested from a drill. I am using a power supply (0-30V, 0-5A) and am trying to measure no load current. With my power supply set to 18V (voltage controlled) it won't start unless I help it (give it a twist). This is the case no matter where I set my voltage and current. Once I get it turning, the voltage on my power supply reads below 2V and the motor speed changes only when I change the current limit. Why would this be? Voltage should control speed, no?


texts: Powering Raspberry Pi Zero W and LED-Strip with 24v DC

texts:
I have a RGB LED-Strip from IKEA that is powered with a 24v DC adapter. My Plan is to Power a Raspberry Pi Zero W and the LED-Strip at the same time from the same power source.

My circuit looks like this at the moment:

TLE4271 Datasheet
IRLZ34N Datasheet

I have already sucessfully built part of the circuit without the voltage regulator (according to this tutorial), powering the PiZero seperately via USB.

My main concern is getting the right voltage to the PiZero, if needed I can upgrade the power supply to deliver more current. I am quite a newbie in regards to building circuits so my question is if the TLE4271 is the right tool for the task. As far as I understood the datasheet it should output 5v/550mA for any input <42V.

tl;dr: Can I power a Raspberry Pi with 24v through a TLE4271?


texts:
First of all I'd like to say that I'm quite new in electronics (I'm a software developer) so I might be missing some basic knowledge for which I apologize.

I'm trying to create a DAC using the PCM5122. The datasheet mentions that the charge pump flying capacitor should be a 2.2uF COG Ceramics (I'm guessing COG should be C0G - C zero G).

Now, I've been to my local electronics dealer and he has never heard of a ceramic capacitor with that value. Also Conrad (where I usually get my stuff) doesn't have one. The only place where I can find such a capacitor (SMD) is at Mouser (which will cost me € 20,- on shipping).

My questions are:

Why is this so rare?
Is there a non-SMD variant of this capacitor (I can't find one but maybe I'm not using the correct search terms)?
Can I use something else in stead?


texts: What is the maximum voltage of a Lithium Ion Battery

texts:
My question is about the maximum charge voltage of a Lithium-Ion cell.

I have charged my battery pack with 8.4V (the maximum voltage). The pack is a Samsung ICR18650-26F. The pack has a smart controller with a maximum voltage of 8.5V. This is 4.25V per cell.

I read about this that exceeding 8.5V can degrade the lifetime of the pack. However, the manufacturer don't clarify this detail.

My question: Will this voltage damage the cells or this within the tolerance range.


texts:
I like to control 8 switches (GPIO pins) individually via USB (on/off). To start i have a USB UART adapter (CP2102). By sending a command to the virtual port to control each pin i would like to control each pin.

My question is, how do i bridge from UART to 8 GPIO pins? Is there any IC that could do this?

Or are there better ways of doing this via USB?

I know i can easily do this with a Arduino and a shift register, but i would like to make this truly low budget, with a minimum of overhead.


texts: Does this audio amplifier do differential filtering?

texts:
I was looking at this schematic for a two-channel audio power amplifier.

The amp supports a bridged mode by means of an XLR connector and a switch. When the switch is in the XLR position, pin 2 (Signal+) is sent to the left channel and pin 3 (Signal-) is sent to the right channel and the speaker is connected between the + outputs of the amplifier.

However, as far as I can see, there is no differential stage before the power amplification stage to actually filter any noise from the balanced input. Therefore, any noise that gets onto the input wire will be amplified and sent to the speaker.

Is this correct, or am I missing something?

Here is the amplifier in question:


texts: LCD prints black text on blue screen, but can print white on blue when bugged out

texts:
I am using the esp8266 which can supply 3.3V to power on an LCD 16x2.
However, I am running into trouble regarding the visibility of the LCD's contents. The LCD prints black text on a blue background and it is very dim, and you need to look from a certain angle to see it properly. I tried to make it print out white text on blue background, and eventually the LCD "bugged out" and gave me this (the second picture).

So the LCD is indeed capable of producing white text on blue background, but I haven't been able to do it on command... Does anyone know why this happens, or how I can command it to print white text on blue background?
By the way, I'm programming in the Arduino IDE, and the only functions with respect to the LCD I use are
lcd.begin();
lcd.print();
lcd.write();

// For example
lcd.begin(16,2);
lcd.print("Locked");

The wiring between the esp8266 and the LCD is like this:


texts: I and my friends were trying to make a salt water battery but we cannot find copper strips in our town so is there any other electrode that I can use to make our battery. We have aluminum foil (which is one of our electrode) and what else should we use?


texts: Initial value generator in a circuit (Anfangswertgenerator)

texts:
I am preparing for my electrical engineering exam and I saw this in my script.
I have this first circuit and the requirement is to draw the circuit in Laplace with initial value generator where t > 0
Below that is the solution provided by the professor, but I only have the photo as a solution and not an explanation. I do not understand why is it there and how it is used. What does it mean?
Can someone please explain it to me or tell me how is it called in English so I can search for more literature? Thank you.
Initual circuit:

Solution provided:


texts: BJT schmitt trigger has linear behavior on negative swings

texts:
I am currently building a VCO for an analog synthesizer. The circuit produces a triangle wave by taking a Schmitt trigger output and feeding it into an integrator. The constant output of the Schmitt trigger is integrated to a triangle wave. When the triangle output hits the upper threshold, the Schmitt trigger flips and the output goes negative. However, the lower output is not square. It moves linearly with the triangle input. The entire circuit schematic can be found here,

and the entire article that discusses the circuit in question is linked here.

I have a simulation of the circuit running on falstad.com/circuit/, linked here.

My question is:
Why does the upper trigger work so well, i.e. why is the upper threshold behavior of the circuit constant while the lower threshold behavior is variable (and seems to act like an inverting amplifier with slight nonlinearity?


texts: Why does the op amp output in this circuit have low slew rate?

texts:
I have the following circuit on a bread board (with the exception of using AD820 instead of AD822 - the main difference based on the datasheets seemed to be one versus two op amps in one package).

simulate this circuit – Schematic created using CircuitLab

Simulating the above circuit shows a decent square wave both at input and output. However the actual signal I'm seeing on an oscilloscope is below. Here the slew rate seems to be around 1V/40us, not the 3V/us the datasheet describes.

Things I've tried:

Add the LM358. (The original circuit didn't have this, which caused problems when the square wave went from 0V to 2V. The AD820 was very slow to react to this. Using the LM358 to offset the signal out of saturation helped with that delay.)
Bypass caps on the power rails and LM358 output. Currently I've got a bypass cap on the LM358 output to get rid of high frequency noise (not shown in the schematic). No effect on the actual slew rate.
Replace the AD820 with an LM358. This had an immediate effect and the issue was gone. However I'd prefer the AD820 due to its lower input offset voltage. The final use case here is current sensing (and I happened to have few AD820s around). This was more of an attempt to demonstrate that the breadboard reactance isn't a problem here.
Various loads on the output ranging from 1k to 100k.
Play with the op amp power rail voltage and signal voltage. Most of the experimenting has been done with 5V power supply, +/-1V square wave. I did push the power supply all the way to 10V with no difference in the output (other than it being offset by +5V instead of +2.5V from the ground).
Non-unity gain on the AD820 (10x and 100x non-inverting).
Inverting buffer (-1x gain).

I've also probed the power rails near the AD820 and they were very stable.

The only remaining reason I can come up with myself is that the AD820s I've got are faulty. They are cheap AliExpress specimens after all. If this ends up being the case, is this a common thing with the cheap Chinese chips?

Scope detail on 6.5 V input voltage (probing the AD820 power pins). Note the 500ns scale - The 2 V transition should be fully visible here at 3 V/us.


texts: Why aren't fully asynchronous circuits more prevalent?

texts:
From my understanding, most modern consumer CPU's are based on synchronous logic. Some high-speed applications (signal processing, etc.) use ansync logic for its higher speed.

However, in today's market, speed in consumer products is one of the main selling points (see AMD vs Intel.) Is the development of more complicated lithography faster than adoption of fully asynchronous logic? Or is ansync logic too complicated/impractical for VLSI applications?


texts:
I was recently working on a burglar alarm circuit design in Proteus 8 Professional. I have attached the circuit design below. The problem is when I am simulating the circuit, I am getting the following errors: -

[SPICE] DELMIN increased to 2.77556e-017 due to lack of time precision.
[SPICE] transient GMIN stepping at time=0.249993
[SPICE] TRAN:  Timestep too small; timestep = 3.46945e-018: trouble with node #00005.

How can I resolve them? What changes should I make in the circuit design so that I can simulate my circuit successfully ?

The view of node #00005 is also attached as an image below the circuit design


texts:
I just completed a half bridge smps and had a test run.
The series bulb on input just blink for a second at first and then shut down at it should.
But the output voltage is quite weird because my multimeter is reading about 0.5,3,7,11,7,5,... Volts changing constantly and when I shut it down, the voltage is 27volts in the capacitors.
I have not connected any till now.

Is my multimeter incorrect because I am using a very cheap multimeter? A change I did in the circuit is that I used a full bridge rectifier 35A for output rather than dual-diodes because I don't have any. Can that be a problem too? Also the voltage I calculated for secondary was between 38-40 volts but I am getting 27 volts after shutdown.
Thank you


texts: Phase Shifter: why is simple RC circuit's output 0 when phase is 90 deg?

texts:
I am rereading an electronics book (Fundamentals of Electric Circuits; Alexander) that says that the circuits

 or

have the total impedance

  Z = R + jXc

and that the phase shift is given by

  theta = arctan(Xc/R)

where Xc = -1/wC

It then says:

  We should keep in mind that [these] simple RC circuits ... also
  act as voltage dividers. Therefore, as the phase shift θ approaches
  90◦ , the output voltage Vo approaches zero.

I can see that as theta -> pi/2, Xc/R goes to infinity, meaning that C or R must be very small.  In the second example, if Xc is so much larger than R, then I can see that eventually all the voltage will be across it and none at Vo.  (Is that what he means by voltage divider?) However, in the first example, if C is very small then Xc is very large, and doesn't that mean that all the voltage will be across it and Vo will approach Vi?  Or is C so small that it acts like a short?  If the latter is the case, then why isn't C a short in the second example and all the voltage across R?


texts:
I am figuring out the schematic of an existing e-bike controller. Specifically I am trying to replace an lm317t with a custom made switch regulator that outputs the same voltage. But first I want to understand the current and existing layout. And I am actually failing on this.

With the help of the multimeter I have come up with an schematic which seems to match with what other people has come up as well:

full board schematic here:
https://github.com/KingQueenWong/bmsbattery_s06s_controller_hardware/blob/master/S06S-Controller.PDF

Now, I am really puzzled. When I switch on the board VOut is 15V (according to my multimeter), as expected (it is a well known design where the output is known to be 15V). But how that can be if VIn is connected to VOut through a resistor?

To prove my logic I have moved that to LTSpice:

And as expected, the VOut is basically the VIn plus the resistor drop.

I have checked that the schematic matches with reality 100 of times, and it does (except if I am missing more part, which could be, it is a dense board).

How can this be? What could I miss?

I have opened an issue on that github project, hopefully someone can help.


texts:
I am learning about the VME64 bus. It has only 16-bits of data bus on its P1 connector while no data pins on P2 connector.

Does it means that VME64 is actually a 16-bit bus?


texts: Undervolting BLDC motor on electric bicycle

texts:
I plan to build a DIY electric bicycle using a standard geared BLDC hub motor (36V and 250W rated, 500W peak). To get 36V rated battery, at least 10 Li-ION 18650 cells are to be connected in series (that's how it is usually done). In this case, the battery at maximum charge will give out 42V and will discharge gradually till 30V (limited by a BMS).

Assume that I need to build 9s2p battery. This means that the battery will operate in a voltage range between 37.8V - 27V. Assume that BMS and controller are all good with that.

What will happen to a motor if it's connected to such a battery (with lower voltage compared to 10s2p)? How the maximum speed, torque, efficiency and the lifespan of the motor will be affected? Will power output change or will it be compensated by the increased current?


texts:
I am using IXFK300N20X3 MOSFET for PWM low side switch to heat a piece of metal. The pulse train was 10V(200mA), 100Hz and 0.7% duty cycle. The power supply was in Controlled voltage mode and set at 170V.
The circuit was on a large heat sink and 2 fans were used. The temperatures of the circuit components were measured using thermal-couples and they were below 50% of the max rating.
In constant DC heating scheme, the resistance of the metal changed from 400 mOhms to 6.5 Ohms when applying 9A.
In DC pulsing scheme, at 170V applied voltage, I measured the voltage drop across the load to be 100V using an oscilloscope in math mode. The metal piece was at a constant temperature and at the same temperature (2500K) in constant DC heating, the resistance was 6 Ohms. With that info, I calculated the current to be 100V/6 Ohms = 17A which is reasonable.
However, I assumed the other 70V dropped across the transistor and 4mOhms on resistance, the current = 70V/4mOhms = 17.5kA! Unfortunately, I don't have access to the experiment for another few weeks so I can't make the exact measurements.
Is it correct to assume the 70V drop was entirely across the MOSFET?
Best!


texts:
As someone new to practical RF design (the theory is easy by comparison!), I have a relatively simple question when it comes to matching networks, and it has to do with best practices.

Obviously, a theoretical match is easy to make with software. What I've generally done is measure the antenna, come up with a suitable matching network design. Then starting at the antenna, I add the components one by one measuring resulting impedance from each new component.

It seems to me, the biggest question is what to do when the results are so far off that the remaining component values are meaningless since they assume an intermediate impedance that just doesn't exist in the real circuit.

I guess there are two situations, one where the impedance from the new component is off but at least is along the same reactance/resistance curve. The other of course is where the new impedance is also rotated.

I try to adjust the theoretical matching network to values that produce the same impedance as measured. And sometimes I feel good about the adjustment when, for example, I can be fairly certain its just stray capacitance. Other times I'm not so certain.

What is the best way to proceed in these situations?

  Based on Dakota's comment below, let me clarify.

When putting together a matching network, my approach is to put together a design first using something like JJSmith. Then, starting with the first component at the antenna:

Add the matching component, then measure with a VNA.
If the measured impedance doesn't match the design, adjust the component values until I get the planned impedance at that point in the matching network.
Go back to the Smith chart and adjust the component value (and Q if necessary) in the charting software until the software agrees with the actual reading. Doing so allows me to adjust the component values yet to be added so that once again I'm headed toward the target impedance. It also gives me an idea of the parasitic capacitance and impedance.
Repeat 1-3 until the complete matching network is in, and at the target impedance.
Connect to a sweep generator and see if the antenna and matching network is generally working as I expected. If not, because I kept the Smith chart "in sync" as I built the actual network, I at least have a few clues of which component to tweak if, for example, the circuit isn't resonating at exactly the right frequency.

My question: does anyone have a method that is more efficient. I really appreciate any comments.


texts: SPI Slave Flash programming with two masters question

texts:
I'm looking to make a system that can be upgraded by a customer in the field and I need to know some conceptual thing before I try implementing my current strategy.

Say I have a USB to SPI bridge, some FTDI chip, and I want to be able to program an SPI flash using that. Cool no problem BUT my controller has to boot from the same SPI flash using SPI lines.  So would I be able to just connect everything together?

Here is a picture since I'm not good at explaining these things.

There is a typo on the picture.  The controller isn't being programmed, the SPI flash is.  The controller will boot from the spi flash


texts: Raspberry Pi gets rebooted by an isolated circuit that has a relay (nodemcu)

texts:
I have a Raspberry Pi that is powered by mains from a AC-DC Laptop Charger (with DC Buck regulator).

I also have a DIY Nodemcu (Home Automation project), it has a relay (5V with a control circuit that I got somewhere here and built it[ the relay module itself does use PNP and the nodemcu cannot turn off the relay itself]), they are powered by another AC-DC charger (5V output).

Both of them are connected to a single automatic voltage regulator but, whenever I turn on or off the relay (nodemcu is controlling the relay) with a plugged in Electric Fan as the AC Load, the Raspberry Pi suddenly resets (hardware reset, like shorting the RESET pin on the Board).
I live in SE Asia and we only have 2 prong US like outlet (no grounding, | |), I beleive that they are both live (220V) or maybe each prong are half of the 220V.

Is there any way to determine why this happen? My initial design was to use the same PSU from the RPi and the NodeMCU but I've encountered the problem whenever I cycle the relay, so I used a separate PSU for the nodemcu but I was surprised that the issue persist. The relay module has the glass diode (maybe 1n4148) connected in reverse (protection from spikes?) it is connected to the NodeMCU GPIO D5 with an arduino sketch program that I made.


texts: USB Routing: Switching layers during routing

texts:
I'm working on a standard 4 layer board that involves USB 3.0. I have to route the SS TX/RX pairs as well as D+/D- pairs across a 2.8" PCB. I have found multiple calculators that provide me the information necessary to ensure that I keep the 90 Ohm differential impedance for the trace pairs on the top layer but I'm having trouble understanding what happens when I route the traces to the bottom side of the board.

The differential impedance is largely affected by the distance between the trace and the reference plane underneath. So the distance between the top signal layer and the ground plane (layer 2) might be the standard ~9/10 mil. However, if I route the differential pair on the bottom layer, then the distance between the differential pair and the ground plane becomes ~50 mil - changing the impedance drastically.

On layer 3 I have a 3V3 power plane but in some application notes for example: http://www.ti.com/lit/an/slla414/slla414.pdf it is recommended not to use power plane as reference plane if possible.

Is there something that I am missing here? Or is the only way to route these differential pairs on the bottom layer to make the trace widths super wide to accomodate for the increased height between the reference plane?


texts:
First of all, a little bit of context: I'm designing a single-supply Howland current source using the OPA357 (rail-to-rail 200MHz OPAMP) to delivery 100uA of AC current up to 1MHz. In one of my attempts, I obtained with the following circuit:

As I was designing using frequency domain, I got this response using PSPICE:

Yes, a nasty peak in 100 MHz. Worried about my waveforms, I did transient analysis using square wave signal (1MHz), and I noticed overshoot spikes that happens before transition:

Well, I'm familiar with frequency peaks resulting in overshoots, but I'm certainly not with overshoots happening before transitions. After further investigations, I noticed that this extra current is demanded by the positive input of the OPAMP (when I isolated this input with an ideal buffer, the peaks disappeared).

I solved the problem increasing the size of the resistors, but I'm still not able to understand the behaviour. I don't recall of any conditions that make linear systems behave this way, so I guess that is a non-linear effect of the OPAMP input stage (is a rail-to-rail stage, after all). Anyway, can someone explain to me in which conditions this kind of "pre-transition overshoot" can happen? Is this a linear behaviour? Can you point out how this is happening in my circuit?

Best regards


texts: Defining power supply current specification

texts:
Let's say I'm designing a power supply with input 120-600VAC and output 48V/100mA DC. The load for the 48V output is:

A 3.3V switching regulator
Two LEDS (~2 mA each one)
An ultra low power microcontroller
Some ultra low power op amps
A 48 solenoid with 300 ohm DC resistance. It will be given a 30 ms pulse.

My question is on the solenoid.
48/300 = 160 mA which is greater than my power suppply spec of 100 mA. But the point is that it will be given just a 30 mS pulse. How do I calculate a capacitor that will provide the necessary extra current during the 30 mS pulse? I have to make sure not to have voltage dips during that pulse. Do I need to reconsider my power supply current spec?


texts:
I am trying to develop a basic Zigbee device that can send data back and forth. Now I am facing the problem of not knowing what a basic FCS Frame Control Sequence may be.
There are some fields which are well explained everywhere, but for some I don't know what I should write to them.
See e.g. here: http://www.rfwireless-world.com/Tutorials/Zigbee-MAC-layer-frame-format.html

What are the fields
Frame Pending, Dest Addressing Mode and Source Addressing Mode for? What to write into these fields?
I've searched the web but found nothig that explained this thouroughly. Does anyone have a reference I did not find?
Thanks
Jo


texts: Alternative way to power a mains 12 watt LED

texts:
So I'm pretty excited, I'm about to finish my project but now my problem is I bought a bulb led today and I do not have anymore resources to provide a 60hz 230v to it, since that is its specification.
Wanted to know if my available method can still power it, which is a 10khz to 20khz 230 volt AC supply... An alternative would be a DC voltage at the 200 volts...
So I'm curious if the the led bulb (image attached) would still work at a high frequency input or a DC input as long as it is the required 220v - 240v?
Reason why I ask is because I'm assuming it's using a SMPS thus it would rectify whatever ac voltage I provide before converting it to high frequency ac to be stepped down to the desired LED voltage.... Please feel free to elaborate and discuss. Thank you


texts: What is the FPGA with the highest LEs / $?

texts: Well, what is the FPGA with more Logic Elements per Dollar? I already tried to search some sites but the filters for the products do not include that option.


texts: Can someone verify my EL wire oscillator?

texts:
I'm pretty new to electronics, but my latest project is a circuit with two "frames" of animation that I make out of EL wire, and I want to build a circuit to switch between them every 2-3 seconds or so.

To do this, I'm wiring an astable multivibrator to 2 triacs which each connect to EL wire strands 1 and 2. My goal is that when the respective square wave goes high, the base of the triac will go high and allow the inverter's AC voltage to pass through to the EL wire.

Can anyone verify that what I'm doing is reasonable? And any tips as I pick out components?

Thanks much!


texts: Active electric motor for on specify voltage

texts:
Is it possible to power on electric motor ( a little ) only when the input voltage is 1V by example.

The electric motor is supply by another source (9V by example)

With diode?? Or something else?

I'm a very beginner on electronics, please excuse my English, I'm French.

Logic :

Input 0v = Do nothing
Input 1V = Power On electronic motor with 9V supply
When if the voltage is less then 1V power off motor.

Thanks your helps.
Regards

In Summary:

Is it possible to control a 9V DC motor by using only a 1V logic input; provided that the DC Motor is supplied with 9 volts.


texts: What would be the flow chart for this simple state machine in VHDL

texts:
Here I have written a small program to clarify my question. I want to see how to draw flowchart for this piece of VHDL code.
type STATE_T is (STATE_1, STATE_2, STATE_3);
signal MY_STATE : STATE_T;
signal i, j, k : integer;

...

process(CLK)
begin
  if rising_edge(CLK) then
    if RESET_N = '0' then
      i <= 0;
      j <= 0;
      k <= 0;
      MY_STATE <= STATE_1;
    else

      -- default value
      j <= 0;

      case MY_STATE is
        when STATE_1 =>
          if INPUT_1 = '1' then
            i <= 1;
            MY_STATE <= STATE_2;
          end if;
        when STATE_2 =>
          if INPUT_2 = '1' then
            j <= '1';
          end if;
        when STATE_3 =>
          if k < 100 then
            k <= k + 1;
          else
            k <= 0;
          end if;
          MY_STATE <= STATE_1;
        when others =>
          null;
      end case;
    end if;
  end if;
end process;

Now how would the state machine diagram change if the assignment for i was moved into STATE_2:
when STATE_1 =>
  if INPUT_1 = '1' then
    MY_STATE <= STATE_2;
  end if;
when STATE_2 =>
  i <= 1; # i has been moved
  if INPUT_2 = '1' then
    j <= '1';
  end if;


texts: FT230X 3V3OUT pin connected to 3.6V, Safe?

texts:
The FTDI ft230X datasheet states that, for the output pin of the internal LDO:

  When VCC is 3V3; pin 8 is an input pin and should be connected to pin 10. page 7.

Meaning that 3V3OUT of the internal LDO should be connected to the power supply (VCC) when the chip is being powered by 3.3V.

The datasheet also states that the maximum output of the LDO is 3.6V. page 17.

The 3V3OUT is internally connected to some modules(USB transceiver and reset generator). page 13.

I am assuming that since the LDO "may" output 3.6V, that the USB transceiver and reset generator will be fine if connect 3.6V to both the 3V3OUT and VCC pin.

Is this assumption correct?

This is for an application where an input voltage of both 3.3V and 3.6V are possible on VCC.

Clarification:

Ordinarily, when VCC is at 3.6V the LDO will be attempting to regulate down to 3.3V. BUT! since the LDO output is ALSO connected to VCC, there will be no current through the LDO. The LDO may attempt to lower it's output voltage by increasing it's pass element's resistance, but this will have no affect since the output is help at 3.6V.

Is this safe? Having the same voltage on both the input and output of the LDO, that is higher than what the LDO is trying to regulate down to?

(we know that VCCIO, USB transceiver and reset generator can handle 3.6V, so lets forget about that for now)


texts: How can I make a simple circuit to output only after a min input voltage is exceeded?

texts:
Here's my problem....

I am setting up a camera system on a motor coach that is designed to trigger separate cameras when blinkers or backup is engaged.

the problem I'm having is the only accessible trigger voltage line I have goes from 10v when blinker is off up to 24v when blinkers are engaged. The problem is the 10v on the line is engaging my triggers...i need it to be zero until I turn on the blinker and allow the 24v to activate the triggers

So I thought I could build e a simple zener diode circuit to achieve this.... I purchased a 18v zener and some 2k resisters.... but it's been about 15 years since I've been in electronics and I've forgotten how to get the correct values or parts to achieve my goal and how to build a working circuit.

If anyone could help I would greatly appreciate it... my idea worked but when the zener turned on I only output 3v on the backside (anode) of the zener.

Thank you for any advice...

Update:

I actually posted a picture of the circuit I made which actually worked great for me but apparently it didn't show up here.

I did confirm a solid 10v with a DVM when switch is off.
The motor coach runs on 24v  - some systems run by 12v and others 24.
I'm suspect of the 10v being present too because we have a generator being installed and the installer put switches in so you can toggle from Gen power to bus power.  I think he may have hooked up something wrong... but for now this fix works

The circuit which Russel posted (small circuit on left) is almost identical to what I had. except i used 2 zeners (one 11v and the other 13v) one regular diode, a coupling capacitor and a 75 ohm resistor.


texts: How to remove electric noise from a AC-DC power supply

texts:
I'm having a few problem with a digital analyzer. When a probe is connected to an unpowered circuit. I see no reading on my digital analyzer. But once the power supply is plugged even if the circuit isn't powered.

The digital analyzer will read some pulses at around 50 Hz. This renders the digital analyzer completely useless when powering devices from an AC-DC power supply. I tried with multiple power supply at home but none help.

It's enough to connect the digital analyzer probe to the ground node of the power supply while the power supply isn't powering any load.

My guess is that the power supply are letting some AC through and aren't 100% isolated from AC.

I was wondering if there was a way to filter those 50hz spikes without messing with the power supply. I was thinking of a filter that could be connected in between the power supply and the device I'm powering.

Not sure what wasn't clear from the question. I'm not designing a power supply and not designing a digital analyzer either. I'm just trying to use my digital analyzer on something that is powered to an AC-DC power supply (those cheap wart plug).

simulate this circuit – Schematic created using CircuitLab


texts: How can I find the characteristic table of a D Flip Flop?

texts: There is an X ff and the question is about finding the characteristic table of its. What kind of a ff is this? I can't write the logic equition. What are the inputs ? If inputs are c and x, then I need something extra to write the logic equition?


texts: What's the best way to fix this missing solder pad?

texts:
During a repair of a mixer, I had to desolder the XLR output jacks in order to remove the front panel. When I started to resolder them I noticed that an pad (or eyelet? not sure of the difference) is missing. Maybe I damaged it during desoldering and didn't notice? In any case, I'd like to find the most durable way to repair it.

I've looked for solutions, but they all seem to be meant for single-sided PCBs. Ideally I'd like to replace it entirely, but any instructions I found for that look like they require specialized tools.


texts: 3 Xbee Communictaion : A to B and B to C

texts:
For a new project, I am developing a RTK system. Here, I have a device named Base which has to transmit its NMEA data to another device termed as Rover. For communication purpose I have used Xbee S2C Pro.
The data received by Xbee of Base (termed as A) is being transmitted to Xbee of Rover(termed as B). That is communication from A to B takes place.

Now, I want to transmit the data from Rover to another device which is a computer. Also here I have used a Xbee (termed as C) for communication.

Xbee A = Router 1; Xbee B = Coordinator; Xbee C = Router 2;
Xbee A sends data to Xbee B and Xbee B sends data to Xbee A

The NMEA strings given to the Xbee A are as shown :

The data received on Xbee B is as shown :

No data is being received in Xbee C :

However, when I give data to Xbee B through the console window, it gets received by Xbee C

Need a help for this scenario.


texts: Telescopic cascode op amp with input and output shorted

texts:
Could anyone explain why transistors M1 and M2 are in saturation region when Vin < Vb - VTH4 in the telescopic cascode op amp below?

Thank you.


texts:
I am using HDL Designer and have a pretty large design I need to test. I have created a test bench by using HDL Designer itself and did not do it standalone.
Like the title states, I want to know how to use an internal signal to my advantage, for example do if conditions using such a signal.

Now, I have found this solution:
https://stackoverflow.com/questions/40286725/how-can-i-get-internal-signals-to-testbench-in-vhdl-97-and-isim

But I don't know how to use a package in HDL Designer, or how to do step 2 in the above link.

The reason I need to use an internal signal is mainly because I have a state machine and I want to perform actions based on the current state.

The VHDL standard I'm using is VHDL 93. I'm stating this because I saw solutions using VHDL 2008 but it's not applicable to me.

Any ideas?


texts:
I am using an I2C peripheral in PIC18 series running at 100 kHz and I have used pull up resistors of 4.7 k\$\Omega\$ in the process. I then loaded a code with continuous write operation of EEPROM and viewed the SCL line in the scope. The SCL line does not stay always at 100 kHz. It varies from 100 kHz and some times jumps from 24 kHz to 50 kHz and reaches up to 100 kHz...never goes beyond that.

What should be done to  make the SCL line stable at 100kHz? Will changing the pullup resistor make up the loss?


texts:
I have a fairly complex footprint which I have created in Eagle.  Particularly the complexity comes from the number of vias required for the footprint (this is an RF part).  Initially I tried to drop the vias using the through hole pads as a replacement, but when I do this, it will not allow me to select the layers which it goes through, instead it just penetrates the entire board.

This component will be placed on a 4 layer PCB.  Ultimately my goal is to only have the vias go from layers 1-2 and not completely through (1-4).  Should I be using the via tool in the actual board layout?  If so I'm not sure there is an easy way to place the vias after the part is placed in the layout.  Maybe in the footprint I should use markers, and replace the markers with vias in the layout.  Here is a link to the data sheet and the footprint: BPF-A127+


texts: Automotive LED retrofit causing strange phenomenon

texts:
On a whim, I decided to replace the fairly dull incandescent bulbs in my 2011 Ford Taurus with LED retrofit bulbs. This was working fine until I got to dome light over the rear seats. The dome light has three bulbs, 2 of the bulbs have individual switches and sit in rotating mounts on the outside of the unit. The third turns on only when a door is opened, and sits in the center of the unit.

When I replaced all three incandescent bulbs with LED replacements, I found that the outside 2 lights stayed on continuously, were not affected by the switches that were supposed to control them, and stayed on after the car was turned off (the car will cut all power to the interior after a set period of time when the car is locked, and this is the only time that they would turn off).

I know that some cars require a resistor to be soldered inline to LED bulbs in order to function correctly, so I measured the original bulb at 6-ohms and sourced 2 5.1-ohm resistors to solder inline with the outside bulbs. This did not fix the problem.

But wait, there's more. In the spirit of testing, I put the incandescent bulbs back into the 2 outside sockets, and they were now staying on (the LED in the middle was still functioning correctly). I had thought the unit may be defective, until I put the LED's back into the outside sockets and put an incandescent bulb in the center socket, and the unit functioned correctly. The LED bulbs were now turning on and off, and even dimming.

Realizing now that the LED bulb in the center socket was the culprit, I soldered in a 5.1-ohm resistor on the ground wire from the center socket — this did not solve the problem and the outside lights went back to being constantly on. So, I soldered in a couple more 22-ohm resistors I had laying around, topping out at a measured 51-ohms. This still had no effect on the outside bulbs, though it did take the incandescent bulb from 12.2v to a rather dim 2.8v and the LED from 12.2v to 9.8v.

To summarize (TLDR):

When center bulb is incandescent, outside bulbs work fine.
When center bulb is LED, outside bulbs always on (don't respond to
switches/turn off with car).
Center bulb functions as intended whether LED or incandescent.
Adding resistors (as specified above) did not change this.
These are the bulbs that were used, they are listed as being canbus friendly and are supposed to not give errors.

2
3
4


texts: Tell me a wire-to-wire connector that is soldered, not crimped

texts:
...because I hate crimpers - I'm just not very good with them! This will be for small electronics projects carrying small loads (5V/12V / 3-5As).
It will be to connect on wire end to another. They must be able to connect/disconnect. Normally 2/4/6 wires to link. The dupont equivalent would be:

Thanks


texts: How to calibrate any magnetometer when sensor is changing the location?

texts:
I found magnetometer calibration is done for soft/hard distortions also for tilt compensation using gyro data as well,

but all of them perform for know step of the procedure (rotating aligned with know axis etc.)

I don't understand when the product is made and when it's used in a different place how to perform the calibration? my application cannot rotate the sensor as above once the product is made (a robot).

is there any other way to calibrate the magnetometer? if the location or environment is changed?


texts: Which options exist for switching the polarity of an output with low leakage?

texts:
In my application, I want to switch the polarity of an output which supplies a controlled current up to 50mA (accuracy 100uA + 1%) at up to 36V. The current sensor is on the low side of the output.

The control circuit I have only works for positive current, but I am also supposed to be able to output negative current, switching between the two at up to 50Hz. I already considered using a different output stage, but it seems to be much easier to achieve the required accuracy with a positive-only current control.

Before the idea of switching with 50Hz was introduced, I planned to use two relays for switching the polarity, like this:

simulate this circuit – Schematic created using CircuitLab

R1 is the shunt the current is measured over, while Q1 is used to control the current.

Obviously, using this to switch the output at 50Hz would create quite some noise, and would also put some wear on the relays.

Now finally here is my question: What alternatives do I have for switching the polarity of this output? I'm aiming for less than 10uA leakage under "typical" conditions, where leakage is the difference between the current through R1 and the current through the outputs. Low resistance would be nice, but isn't particularly important because this all happens inside the current control loop.

One option I am currently looking into is building an H-bridge with MOSFETs. There are fully integrated H-bridges, but they typically seem to use the same voltage supply for the logic as for the high/low side of the bridge, so it looks like I'd have to use discrete transistors.

Are there other, perhaps simpler alternatives?


texts: How was the folded cascode stage used to raise the output resistance of the pnp?

texts:
The second figure is a modified version of the first figure.
In the second figure, how is the folded cascode stage formed by pnp transistors Q3 and Q4 used to raise the output resistance looking into the collector of Q4 to β4*ro4?
I have trouble understanding how β4*ro4 was derived.
The overall output resistance of the amplifier is:
Ro = [β4ro4 || β5ro5/2]
I am referencing "Microelectronic Circuits" by Sedra and Smith, 7th edition page 654.


texts: Optimizing magnetic field force of a coil

texts:
For a personal project, I've done a redesign of Samy Kamkar's MagSpoof project. Basically, it is possible to use an electromagnet, h-bridge, and microcontroller to trick a magnetic card reader into thinking a card was swiped, and feed it arbitrary data. I've designed and soldered up a small PCB that has USB charging, Li-ion pack, and a smaller h-bridge driver (DRV8835 - no fun to solder) than the original.

It works beautifully when running of 5V ISP power, with a ~100 turn coil, 30mm diameter, 30AWG wire. The problem is, when I run it off the lithium ion battery (~3.7v, the battery is connected directly to the h-bridge driver through a switch), the magnetic field doesn't have enough power to transmit meaningful data to the card reader - the card reader simply spits out an error message, indicating it saw something but didn't catch any data. With 5V power and the coil configuration described above, I can hold it more than a couple inches away and still get reliable transmission.

I have since added a boost converter to the board to bump up my voltage to 5V. However, I would like to determine the coil design that will produce the strongest magnetic field.

How do I go about determining this? As I understand it, adding turns will increase field strength, but adding turns will increase the coil's resistance and therefore reduce current. Therefore, there is an optimum number of turns somewhere in the midddle.

How would this value be determined?


texts:
From another stackexchange question it should be possible to have the SPI device select pin always asserted given that the SPI bus only has one slave.

I have other interesting features multiplexed to my SPI device select master, so I would like to get rid of the connection altogether and connect the SPI device select slave to a logic 0V via a pull-down resistor.

Is this feasible?


texts: Is it possible to replace a CC2500 with a CC2531?

texts: I have a working Arduino->CC2500 configuration, and I'd like to know if it's possible to replace that with a CC2531 USB dongle. Does the CC2531 have the ability to form the correct packet structure while operating at the correct frequencies to viably replace the CC2500?


texts:
So I've tried to build a Zeta topology DC-DC converter based on a simple buck converter IC XL4016, which works perfectly in a regular buck topology. However, when hooked up in a Zeta topology as shown on the schematic below, the schematic becomes unstable.

If the output voltage is set using R1 potentiometer to, say, 9V, then everything is more or less fine at input voltages V1 < ~7V and V1 > ~12V except for +-0.5V changes in voltage with the input voltage. When the input voltage is close to the output voltage (V1 > 7V && V1 < 12V), the converter suddenly jumps to ~14-16V output voltage and "latches" in this state - no matter what the input voltage is (even if it becomes beyond the 7-12V range) or the potentiometer position, it stays at that output voltage until the power is cut off or the potentiometer is set all the way to minimum.

So, what could be the problem here both with the output voltage sudden rise and latching and with the output voltage a bit unstable (+-0.5V) outside the "death range"?

XL4016 datasheet: http://www.xlsemi.com/datasheet/xl4016%20datasheet.pdf

P. S. It doesn't seem to be a problem with the maximum/minimum duty cycle: the duty cycle in zeta topology at input voltages close to the output ones becomes close to 50%, not 100% or 0%, and the XL4016 IC claims to be able to hadle the full 0%-100% duty cycle range.

I am using the Mastech HY3005 PSU for the input voltage, by the way.

The schematic works fine in Proteus simulation with the XL4016 IC changed to Lm2576-ADJ (I haven't found anywhere the XL4016 IC model)

simulate this circuit – Schematic created using CircuitLab


texts: Replacing a coffee maker switch with a relay - grounding issue

texts: I'm trying to replace a coffee maker's switch with a relay.  Problem is, I'm not sure how to handle the ground wires going into the switch. Looks like the wires are coming from the power supply and the resistors inside. I can't plug them directly into the relay, so how should I ground these to make it work safely?


texts:
I would like to do a simple undervolatge lockout. I thought a BJT as a switch like this:
In normal conditions I would have 30V (and -30 and the othre rail) and 25 mA to 50 mA. These power rails will be used to make the symetric supply of an OpAmp. It's rated for 10 to 45 volts for its +vcc pin (and -10 to -45 and the -vcc pin).
A great plus would be to have a rail openned if a fault is detected on the other one.
The idea is: when the voltage "In" dropes, the current in Rsense will drop too and thus the BJT will pass in "OFF" mode because the current in its base is too low. Is my thinking correct?
I'm looking for a solution that can be implemented on a postiive voltage rail and on a negative one for a symetric voltage supply. If you have a better idea (that works for postive and negative voltages). It doesn"t have to be only with BJTs.
I'm all ears!
EDIT 20/04: so I did what Math Keeps Me Busy suggested. And it works:

green : Vin  , blue: Vout
I was wondering if it was possible to have a more snappy response when the 10V are reached?
Here is my complete design:

The goal of this thing is to make a split (+/-30V) supply for an OpAmp. The OpAmp is rated for 10 V to 45 V on +Vcc pin and -45 to -10 V on -Vcc pin. It has to be able to handle votlages has high as +/-60V.
Q1 is a pre regulator. LM317 is the voltage regualtor. Q2 is for current regualtion in case of a short. Q6 and Q5 are for the Undervoltage Lockout (if that's the correct name).
The 1200 Ohm resistor acts like a 25mA load.
EDIT: just to clarify. In the end, I don't need this UVLO for my circuit. I missunderstood the opamp's specs. Voltage under 10 V isn't going to damage it. But the solution proposed  by Math Keep Me Busy does work.


texts: How to read values from registers in AS7262 spectral sensor with I2C using STM32H743ZI (STM32CubeIDE)

texts:
I have been trying to read data from AS7262 Spectral Sensor using STM32H743ZI2. I am writing the program using HAL Library. Here is the code that I tried for accessing the registers of the sensor, using the sample code from its datasheet, but there is no data received by the board. Could anyone guide me where I have done the mistake?
Code:
#define AS7262_ADDR 0x49 << 1
#define I2C_AS7262_SLAVE_STATUS_REG 0x00
#define I2C_AS7262_SLAVE_WRITE_REG  0x01
#define I2C_AS7262_SLAVE_READ_REG   0x02
#define I2C_AS7262_SLAVE_TX_VALID   0x02
#define I2C_AS7262_SLAVE_RX_VALID   0x01

uint8_t i2cm_AS7262_read(uint8_t virtualReg)
{
    HAL_StatusTypeDef ret = HAL_OK;
    uint8_t status, d = 0;

    while(1)
    {
        ret = HAL_I2C_Mem_Read(&hi2c1, AS7262_ADDR | 0x01, I2C_AS7262_SLAVE_STATUS_REG, I2C_MEMADD_SIZE_8BIT, &status, 1, 50);
        if (ret != HAL_OK) {
            return ret;
        }
       if ((status & I2C_AS7262_SLAVE_TX_VALID) == 0) {
            return status;
            break;
        }
    }

    ret = HAL_I2C_Mem_Write(&hi2c1, AS7262_ADDR, I2C_AS7262_SLAVE_WRITE_REG, I2C_MEMADD_SIZE_8BIT, (uint8_t*)(&virtualReg), 2, 50);

    while(1)
    {
        ret = HAL_I2C_Mem_Read(&hi2c1, AS7262_ADDR, I2C_AS7262_SLAVE_STATUS_REG, I2C_MEMADD_SIZE_8BIT, &status, 1, 50);
        if (ret != HAL_OK) {
            return ret;
        }
        if ((status & I2C_AS7262_SLAVE_RX_VALID) != 0) {
            break;
        }
    }

    HAL_I2C_Mem_Read(&hi2c1, AS7262_ADDR, I2C_AS7262_SLAVE_READ_REG, I2C_MEMADD_SIZE_8BIT, &d, 2, 50);
    return d;

}


texts: Generating high current negative supplies

texts:
I'm trying to generate a high current negative supply (30A, -2V). This is to be a negative symmetric supply along with a (30A, +2V) rail, with an actively driven ground which I need to be system ground. This also happens to need to be a programmable supply, but let's set that aside for the moment.

The various methods which I have used to generate negative supplies in the past have been limited to fairly low currents - maybe about 1-1.5A. I've been looking around, and most discussions or solutions seem to talk only about these kind of low currents.

There's also the virtual ground approach, but at these currents I'm not quite convinced that would be the way to go. There's also the nagging problem of floating the load, which I'm not particularly sure I can do.

I've been looking at the LTM4662EY for the positive rail, which seems to quite nicely fit my requirements. I'm also looking at the LM5170, which seems a little overkill, but I think the bidirection current bit of the circuit might help get me the negative rail as well.

I'm looking for answers to the following questions :

What kind of approach is normally used to generate high current bipolar/split supplies?
Is there something like the LTM4662EY which can generate negative voltages, or some way to get the LTM4662 to generate the negative voltage I want?
What sort of approach should I be using to get the LM5170 to generate negative voltage output.
Any other controllers or application notes or pointers that might help, especially if it seems like I'm barking up the wrong tree.

Any insights would be much appreciated.


texts:
I'm reading Douglas Self's Audio Amplifier Design, and there is a circuit presented with a current source I can't understand.

The source would be the one formed by Q5, Q6 and Q7. If Q6 would be 'flipped', with its emitter on the base of Q7 and its base on the colector of Q7, I would recognize it as a bipolar mirror with base-current compensation, but I can't understand how this one works.


texts:
I've built the circuit shown in the picture on the breadboard. The simulation works as expected but when I build it i don't get any oscillations. I've measured all the DC voltages and they are as expected. The measure hfe of the transistor seems to 216 while I assumed 100 in my calculations.

I've done a continuity check using my multi meter and all seems to be in order. Do you guys have any idea why this might be happening?

BJT is biased at 5mA and Collector voltage at 6V.

Edit1: Added a 10uF capacitor. Also added a 0.1uF emitter bypass capacitor to increase gain. Still no go.


texts: Difference between bit rate and baud rate?

texts:
Everyone seems to have different definitions everywhere I look.

According to my lecturer:

$R_{bit} = \frac{bits}{time} $

$R_{baud} = \frac{data}{time} $

According to manufacturers :

$R_{bit} = \frac{data}{time} $

$R_{baud} = \frac{bits}{time} $

Which is the correct one?


texts: Reading switches without a common ground from Arduino

texts:
I'm trying to interface a steering wheel control interface with an Arduino.

The interface connector has 6 pins, A to F.
These pins are interconnected with 8 push buttons, SW1 to SW8:

simulate this circuit – Schematic created using CircuitLab

These buttons don't have a common ground, so I can't connect them directly to the Arduino.

How can I interface these with the Arduino, in order to know which button is pressed?

What came to my mind is creating a network of resistors, injecting +5V somewhere, and reading an analog value that would be dependent on which button is pressed, but I'm not sure how to do that, or even if it is the best solution.


texts: How do I figure out the exact voltage and current needed for a part?

texts:
Whenever I look for parts in my local electronics store, I come across parts(e.g a speaker), that have just a power rating stated(e.g 2W).

While I know how to calculate power,voltage, resistance etc, how exactly do I figure out the exact current and voltage for the given part?

For example, if the part has a power rating of 2W, and power is calculated via P = V * I ,
the part may be 2V running on 1A, or 4V with a current draw of 0.5A, etc etc.

Is there a way I can find out the exact needed voltage required and current draw if all I'm given is the power rating?


texts: Amplifying signal with Darlington not working

texts:
I'm relatively new to electronics and this is not my usual field of work.

For a bigger project I need to read a flow sensor's (Biotech FCH-C-PA-N) output. The output needs to be processed by an Arduino or Raspberry. The problem I have: The flow sensor's output (a square wave with varying frequency) has a Voltage between 0mV-220mV where the ~220mV represents the HIGH state.

How do I amplify the 220mV to 3.3V (RaspberryPi) or 5V (Arduino)?

I thought about using a darlington-circuit. But even with three Transistors (BC547) somehow I can't read a HIGH state at the microcontrollers input. The darlington circuit doesn't open.

edit: Problem solved

As stated by WhatRoughBeast this sensor works as intended without trying to amplify the signal (which was done wrong by me anyway due to a misunderstanding of the amplifying effect of transistors). It turned out that the used sensor was "FCH-C-PA" and not "FCH-C-PA-N" (I got the wrong manual by the seller). This one uses NPN open collector sinking, so WhatRoughBeast's answer is correct.

The reason why I couldn't get the correct signals at first (after plugging in the pull-up resistor) was a short-circuit at the electrical connection which was encased.


texts: Circuit to pass voltages above a threshold level

texts:
I have a sine wave signal centered around 2.5 volts (1/2 Vcc) in which I require the the upper half only, brought down to 0 volts, so a 2 volt peak-to-peak input around 2.5V would become a half sine wave from 0 - 1 Volts.

I have tried a subtracting amplifier configuration to simply subtract the DC level from the sin wave but this introduces a 0.5 volt to 1 volt DC offset onto the output signal or generates spikes at the start of the output waveform depending on what op amp I use.

Hopefully someone can help or I may have to re-think my design completely.

/******************** Additional information ********************/

Here is the initial schematic I had for this circuit,

The input sine wave of variable amplitude but centred around 2.5 Volts.
R1 and C2 low pass filter the signal at 0.1 Hz to get the DC level which is then buffered by IC1B and used as a reference for all the other operations
IC1A inverts the original signal around the DC level
IC2A and B then subtract the DC level from the inverted and non inverted versions of the signal.

Monitoring the points between sections of the circuit on an oscilloscope showed the expected values at all points except Out A and Out B, which had waveforms as shown in the link below.

the peaks of the waveforms when using a normal LM358 op amp were correct but there seemed to be a 0.5 - 1 Volt floor on the signal, trying an OPA2333 rail to rail op amp as IC2 gave the third waveform with a large spike at the initial phase of the signal which is not really desirable.

unfortunately adding the following active rectifier circuit prior to R4 and R10 did not have any effect on the output with an LM358 and I then managed to kill my only OPA2333 amplifier so can't test if it would have any effect on that.

the signals from Out A and Out B will be used to drive power transistors to source the two halves of a centre tapped transformer.


texts: capacitor discharging through oscilloscope's probe

texts:
I have a device and the output ac voltage is 1-2Vp-p with very low current.
I made a voltage quadrubler with a storage capacitor(output) in order to rectify the voltage and observe how much time is needed to charge the capacitor.

So, while the device's current is very low, if I connect my oscilloscope to the storage capacitor and let the device operates for two hours I will never see the charge waveform because the capacitor discharges through the probe.

Could you suggest me something to stop the flow of the current through the probes.
I thought to connect a resistor parallel to the capacitor and then connect the probes but it didn't work.

I upload a rough layout

Thanks


texts:
Everybody.

I have a doubt. If I use one connector like this:

https://www.data-alliance.net/rp-sma-t-splitter-y-adapter-joiner-join-2-antenna-cables-to-one-connector/

In one board and connect two antennas with the same gain and shape at the same time, my gain will improve or I will just mess with everything?


texts: Is there a way to direct the data to a particular port for this scenario?

texts:
There is a PC program which reads ASCII data from serial port in real time and processes it. The thing is I'm not able to change the code. The program reads the incoming data where one can only set which sections to be logged.

Now there is a sensor device which outputs data via RS485 which I can convert to RS232 and to USB as well. The thing is this device will send data only if it receives request data.

My problem is the PC program is not able to send data but only receives. I need something to trigger(send request to the device) continuously and then send the received data to the PC's port to be read by the program.

Would a micro-controller work in that case as below?:

simulate this circuit – Schematic created using CircuitLab

What other tricks might work in this case?


texts: Google Pixel XL; Anyone know what this middle piece is called and what it does?

texts:
Does anyone know what this middle piece is called in the Google Pixel XL?

Here is the image (I've underlined in blue):

I noticed that it emits infrared light. I think its a proximity sensor but I don't know for sure.


texts:
I have a design project which is an infant incubator. This design consists of Fujitsu's MCU MB90f387s, a potentiometer (for input temperature), HSM20-G (analog temperature and humidity sensor), 2 bulbs, LCD, FAN and relay. I am using ADC of the MCU for the sensor and potentiometer.
The flow of the system is:

read the input temperature
on the bulb or fan until the sensor reads temperature similar to the input temperature.
off the bulb or fan.

The problem is when the MCU turns the relay on (turning on the fan or bulb), there is a voltage drop in the power supply which makes the sensor and the potentiometer's data(reading) change.
A scenario:
Initially, bulb1 off, bulb2 off, fan off

input = 33C, sensor reading 29C
bulb1 and bulb2 on, voltage drops .6V, input reading 30C, sensor reading 25C
sensor reading 27C, bulb1 on, bulb2 off, supply voltage gains .3V, input reading 31C, sensor reading 26C

Explanation:
whenever the mcu turn the bulb on, an amount of voltage drops, if the mcu turn on the other bulb, another voltage drop.
Question:
What is the solution so that the sensor and the input temperature have consistent reading?
i already read this, from arduino forum. Giving another supply (cellphone charger) to the sensor or relay makes the sensor/relay not work.
Please shed me some light about this. thank you.


texts: How are series connected batteries of different voltages (or even same voltages) charged "equally"?

texts:
I am trying to understand conceptually, how a series bank of batteries is charged "uniformly".  Let's take the example of of six 6V AGM batteries for a 36V golf cart.  The charger is 36V nominal but of course will be somewhere between 36V and maybe 43V.  Ok so the electrons from the charger come out of the - (negative) post on the charger, then pass thru the first battery in the series "chain", then pass thru the other 5 batteries, then back to the positive on the charger.  How is it that each battery gets charged about "equally"?  Shouldn't the first battery the charger "sees" get a stronger charge?

Here is another way to state my question.  Suppose instead of six 6V batteries, we had three 8V batteries and two 6V batteries all in series.  That is still 36V nominal total.  Suppose the batteries are in this order (8V,6V,8V,6V,8V).  How is it that while charging, you might see 6.9V across each 6V battery but see 9.2V across the 8V batteries?  In other words, how does it "know" to charge each battery the right amount (voltage and current)?  Does the order of the "mixed" voltage batteries matter for charging/discharging?  Would it help to occasionally reorder the batteries so the "first" battery in the chain is changed every month or so, or is that order irrelevant?

When answering this, you can assume that all batteries are AGMs of similar age and health.  Also assume the interconnect wires are thick and of minimal loss and do not get warm.


texts: Driving MOSFET of 3.3 V gate voltage with 1.8V PWM pulse

texts:
My micro-controller is giving a PWM output of 1.8V. I need to drive a MOSFET with typical gate voltage of 3.3V. I am planning to use two cascaded switches (NOT gate configuration).
I have checked checked following IC.

TLP250:- minimum supply voltage should be 10V (I can only use 3.3V)
IR2110:-  Logic '0' input voltage is between 0-6V. (Maximum available
i/p voltage is 1.8)
TC427:-  minimum input voltage for logic '1' is 2.4 V (Maximum available
i/p voltage is 1.8)

Is there any commercially available IC suitable for my application?


texts: Device, Circuit, Component to Manipulate a Relay and an LED Light - Open to Any Ideas

texts:
This is my first post, and I am electronically illiterate - have mercy on me....
THE PROBLEM:
Dealing with an automotive +12V system - and I have a new voltmeter that I'd like to install. In addition to a conventional pointer that swings to a number indicating voltage, it also has a low-voltage warning LED that I would like to utilize. The manufacturer of the instrument offers no kind of mechanism by which to activate the LED warning light, and merely indicates that a "remote relay" or "voltage sensing device" needs to be used to activate the LED warning light.
For what it's worth, the LED by itself starts to illuminate around 2V-3V, and reaches maximum brightness just a bit after that. Assuming the instrument has an internal resistor to manage the current to the LED as it tolerates typical charge voltage in the car, upwards of 14 volts.
What I tried based on my tremendous lack of knowledge, but just trolling around the web, was a relay and a zener diode. The relay is a typical automotive mini-relay, 5 pins (NC/NO). The normally closed contact would energize the bulb as it would be wired to an ignition key switched +12 circuit. With the relay energized, that coil would break the NC connection and kick over to the the NO circuit, which would simply be connected to nothing, but it breaks the circuit proving the +12 to the LED, so LED goes off.
The trick is in energizing the relay. I thought to use a 12V zener diode in reverse bias connected to the contact that would energize the relay via another ignition switched +12 circuit. If the car's charge condition was at least 12v or higher, the zener diode would conduct and trip the relay, killing power to the circuit energizing the LED. Should the charge voltage drop below that roughly 12V, relay de-energizes, and LED illuminates again to indicate a problem.
The relay actually trips at around 6V, and at roughly 13.5V, a likely charging voltage, it's using about 3 watts, 60 milliamps, so I went with a 5 watt diode. The problem is, the diode does not seem to allow enough current through it to trip the relay. I tried it both in series and in parallel as I was told to try it both ways. I used Digi-Key 1N5349BGOS-ND for what it's worth.
So that's what I have tried, simply not having the proper knowledge of how components work, or what would actually be proper for what I need to do. Perhaps this is the completely wrong approach.
I do have a multi-meter as well as a 12V bench top power supply for testing purposes, but lots of electronic ignorance, so open to any and all suggestions. Thank you very much in advance.

simulate this circuit – Schematic created using CircuitLab


texts: Calculating noise voltage of a thermopile for NEP

texts:
I am trying to calculate the noise voltage Vn of a thermopile sensor for NEP.
As according to formula
NEP = Vn/R
Can someone elaborate how would i do that if my thermopile is connected to AD360 amplifier ?


texts: Can AC mains induce a negative voltage in my photodetector circuit?

texts:
A smart meter, such as the one in the picture below emits a red light from an LED based on the power consumption (while I was measuring it, it was around 7 sec on 7 sec off i.e. ~0.25kw).

The emitting LED is labelled 1 Wh/imp, as shown.

I constructed the circuit below on some veroboard:

simulate this circuit – Schematic created using CircuitLab

Datasheet of the op amp I used.

Datasheet of the photodiode I used. (note that the angle of sensitivity is 20 degrees, so it's quite a weak signal, even with a 1MOhm resistor.)

At ambient light (indoors), the circuit registers about +250mV.
Outdoors, it climbs to about +1V max.
If I cover the entire circuit (that is, put the whole thing in a box, seal it from all corners, put it inside a dark wardrobe, I get about +100mV at the output.

Problem:

I stuck the device onto the steel case of the switchboard, with the photodiode directly opposite the red led of the smart meter. I then completely closed the switchboard so that there is no light into the box, with only the probes to my multimeter coming out of it.

I measured approx. -35mV and -55mV. I checked the polarity of my multimeter many times, and the voltage measured is definitely negative (as soon as I open the switchboard the voltage goes back to around +250mV.

As I said earlier, the house is drawing around 250W according to the emitting LED. That's only 1A, and the wires are behind the meter.

The circuit is powered by 4x1.2V batteries, and the mains voltage is 240VAC.

So, why is the circuit reading a negative voltage?

Edit:

I just checked again, and if I set the multimeter to AC, I get 0.3V.


texts: in an enhancement type nmos when a channel is created then a depletion layer should be created under the n-channel which means electrons get a potential barrier to overcome.now is this potential barrier is included in threshold voltage??


texts: If I feed an LM324 with V+ but no ground, what value will I see on the GND pin?

texts: I have an LM324 in my circuit and I connected the V+ pin to 5V, but left GND pin unconnected (floating), so what value will I see on the GND pin?


texts: Is there a standard to connect PIR sensors to own hardware?

texts: Does anybody know if there is a standard to connect PIR sensors to own hardware. E.g., I've seen that V+, GND, VIN (with load resistor) are required, but is this all?


texts: Why does such a lamp and two battery circuit not work?

texts:
Assume I have a lamp and I connect one side to the + pole of one battery, and then the other side to the - pole of another battery (say two batteries of 1.5V). The remaining - and + poles are not connected.
So there is a potential difference between across the lamp, but why does it not turn on? It seems to contradict the basic law of electricity.
Note: I am a newbie in electronics/electricty.


texts: Analog signal exchange between microcontroller and PLC

texts:
Overview

I need to create an analog voltage of 0V-24V for the PLC ( s7-1200) with a
microcontroller with operating voltage 5V.

Approach

I've been doing this research since yesterday. I'll share the results of my research. I need your feedbacks.

First of all, I was uncertain about this. I decided to drive a 24V DC signal with a mosfet. So I'm gonna raise my signal. In my opinion it wouldn't be right to use pwm to drive this mofets. If I drive a mosfet with 0-5v pwm, I would get a 0-24v pwm signal from the mosfet output. So I decided to produce an analog signal. (also 8 bit, 256 step pwm signal would not be sensitive.) What you think about my approches? Am I right?

I've found a lot of methods to produce an analog signal.

Low pass filter. (I read and passed that it has a negative effect on the bandwidth and some things I don't understand.)
R2R ladder (After seeing option 3, I didn't look at that much.)
mcp4725 I2C DAC, ( I liked it very much. It was good to write the signal you want to eeprom with the I2C. Because my analog signals won't change very fast.I don't need high speeds.) Because of this chip's I2C addresses, only two can be used at a time. So I will multiply I2C channels with TCA9548A. I need 16 analog output. After that, I will raise this analog signal with a mosfet.

Yes, I need your comments and suggestions.

Best regards


texts: I have an ebike. I usually charge my lead acid battery for 6 hours until the charger shows green light, and I can travel for 30 Km or so. But since last week, green light indicating full charge appears after only 2.30h, and I can only travel 10 Km max, on low speed. If I try to charge it with another charger, same thing happens. I tried everything, but I can't get the bike to charge after 2.30h. Does anyone know what could be the problem?


texts: How to light a LED using photo transistors output?

texts:
I built a circuit using RPR220 photo sensor to detect the surface displacement caused on a material when external force is applied. I could see the output on a CRO even when there are minute changes on the surface for little forces applied.

Now the issue is, the output of the sensor is very low (appr 0.20mA) and for a maximum surface displacement I could see the change in the output varies between .18mA till .22mA. (the changes in the voltage is also in the milivolts range).

I used a current amplifier circuit that boosted the signal upto 100mA but still the changes in the surface resulted in minute variations at the output (the output varied from 96mA to 102mA).

How can I light an LED whenever there is a change in the average current/voltage value? Is there any logic gate IC that I can use in such a way that even if the signal fluctuates 100mA the output logic is set to one and the LED lights up?

P.S. The sensor was placed at a distance of 6mm from the surface.


texts:
I want to use the sim800l module for a project. The module powers up and I am able to communicate with it via arduino.  Every time I enter the pin the LED stops blinking for a couple of seconds and then the module powers up again.
AT+CPIN?

+CPIN: SIM PIN

OK

This is what I get after entering the correct pin.
Also the LED never blinks slower than once a second so it is not connecting to the network.
I am using a 3.7 lipo battery and a 1000uF capacitor to deal with the 2A spikes but it does not seem to work.
Please help me I am really frustrated.


texts: Can a differential ADC replace an instrumentation amplifier?

texts:
Greeting Everyone ,

I am doing a project of data acquisition system
Let me explain project in simple terms
Step 1)  Sensor :
 A strain gauge type PRESSURE sensor (Wheatstone bridge)Specs : 2mV/V output I am applying +- 5Volts (10 Volts) The output swings from 0mV to 20mV(full pressure)

Step 2) Instrumentation amplifier : Output of the sensor is given to an instrumentation amplifier which i made using 3 OP07 opamps  i have also added a filter at the end of amplifier to reduce noise.Specs : the circuit has two ZERO pots (to adjust Zero output)(Connected at zero net ) and an Gain adjustment pot .Gain adjustment pot is connected at R5

Step 3) ADC : The output from this circuit is gain adjusted (typically gain =100) and given to ADC ADS1115. ADS1115 has capability to take the differential input directly and also has provision for programmable gain Upto 128
                         Which looks something like this :

so i just interface my controller device with the above setup to get data (Data Acquisition ) and plot graphs etc

------Question-------
 Can we  Totally  bypass instrumentation amplifier and directly (maybe add a filter)connect the output of sensor to ADC ?
1) adc will do work of converting the differential signal into binary data
2) We can avoid the instrumentation amplifier circuitry
3)ADC has programmable gain which we can set to 100

Any suggestions and reviews are welcome !
Thank you in advance !!


texts: Dangers of ESD wrist wrap / mat / ground Plug Adapter in an Apartment building?

texts:
I would like to know if there are any dangers when we are using a wrist wrap connected to an ESD mat that is connected to ground on the wall socket in an apartment building.

Lets imagine that in your above neighbor something shorts and releases all the current to the ground cable, and between him and the earth is my flat and the socket that I am using with my ESD mat..... or even, other scenario, like a thunderstorm and some lightning hits a roof rod and all that charge goes down the building and once again I am somehow in the middle....

Is this even possible to happen? Should I worry? Is there anything I can do about it?


texts: For PIC16 how do I switch back to GPIO pin usage from SPI?

texts:
I am trying to program a PIC16F18877
I have some auto generated code that sets up SPI on some pins. (eg RC4) I have a device that is not SPI properly so wish to Bit Bash it. How do I switch the PIN back to GPIO usage? There are PPS registers that control which pins the SPI uses but not sure how to just "turn it off" and switch it back to GPIO usage. I don't want to redirect the SPI somewhere else.

EDIT:
The pin is being driven low when latch is high and tristate is low. There is an external pull up.  Setting tristate high causes the pin to go high, both on the scope and the port register. So the pin is being driven low by the PIC even when SSP1 SSPEN is low?


texts: understanding constant current source circuit

texts:
The circuit is a constant current circuit which charges the capacitor C1. The C1 is periodically discharged through a resistor which is not shown in the image. During discharging, the constant current circuit is isolated (through a mux, not shown in figure).

Here is my understanding.

The capacitor C1 is assumed to be discharged in the beginning.Also, Q1 is assumed to be off.

The negative terminal of opamp now sees 10 V at it hence, the output of opamp goes to 0V. This turns on Q1. So, the current through C1 is through R1, which is 240 uA.

My present question is why i am unable to find the ramping voltage across C1?
It is tied to 5 V from the point at t = 0.

Edit: able to see the ramp. But, unable to understand how it stops at 5 V?

Added image of current and voltage across BJT(Green)


texts: Where should the ground be placed in a full wave bridge rectifier ? I mean if the ground was placed at one end of the load resistor, then won't the other diode (which would be forward biased in one cycle) that leaves from that point( point of contact of the resistor and ground) be cut off since that diode is not having a forward voltage of 0.7 volts ?


texts:
In the following picture:

I have screenshotted a picture of the front end of a phototransistor receiver circuit from Electronic Gadgets for the Evil Genius. It appears to be a phototransistor-based transimpedance amplifier. However, I am having trouble understanding the relationship between the phototransistor's collector current and the output of the amplifier, I1D.

How would I determine the relationship between the collector current and Vout in this circuit? And how would I convert this circuit to a photodiode-based amplifier? Would this improve the signal-to-noise ratio?

I've looked at a few application notes, but what am I missing?

In this circuit, C8 = 0.01 uF and C9 = 470 pF.


texts:
I've been playing with a couple servomotors i got from surplus of pick and place machines.
So far, i've decoded their pinout and i'm working on reading the encoder, here comes the problem:

From what i observed, motor comes fitted with a 4096 cuadrature pulses per revolution +1 index pulse each revolution.
 Doing some testing in the Arduino IDE showed that spinning the motor a little faster and the encoder starts loosing steps...

I decided to migrate the code to AS7 and flush all the Arduino overhead, but the chip seems incapable of dealing with it. Correct me if i'm wrong about the following:

With 2048 cpr (just using the rising pulse of one cuadrature channel) and a rotational speed of 3000rpm, one revolution is complete in 0.02seconds.

Assuming the previous 20mS / 2048ppr we have one rising edge every 0.097mS -> 97uS give or take.

Is that time enought for executing the following ISR?:

#define F_CPU 16000000UL

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdio.h>

volatile int count;

int main(void)
{

    DDRD  = (0<<PORTD2) | (0<<PORTD3)| (0<<PORTD4);
    PORTD = (0<<PORTD2) | (0<<PORTD3)| (0<<PORTD4);
    EICRA = (1 << ISC11) | (1 << ISC01);  // Configure interrupt trigger on rising edge of INT0
    EIMSK = (1 << INT0); //ebable INT0
    sei();

    while (1)
    {

    }
}

ISR (INT0_vect){

    uint8_t i = ((PIND & 0b00010000)>>4);

        if (i == 1) {

            count = count +1;

            }else{

            count = count -1;
        }

    EIFR = (1<<INTF0);
}

If not, how should i do it... Dedicated counter IC?

Thanks

**Edit:**capture of the logic analyzer comparing one revolution (index) to encoder A


texts:
I've written a small program for Arduino, in which it receives a two digit number from serial, for example ""26". Then it set's HIGH voltage to pin 2 with the duration of 6*100. That works fine, except that I also have a LED connected to pin 4, and it's voltage is set to HIGH at start-up, but when Arduino is receiving/sending through serial, it drops the voltage - is that normal?

The code is as follows:

int pts = 4;

String input;

void flash(int pin, int duration){
  Serial.println(pin);
  Serial.println(duration);
  pinMode(pin, OUTPUT);
  digitalWrite(pin, HIGH);
  delay(duration);
  digitalWrite(pin, LOW);
}

void setup() {
  input="";
  digitalWrite(pts, HIGH);
  pinMode(pts,OUTPUT);
  Serial.begin(9600);
}

void parseInput(){
  if(Serial.available()>0){
//digitalWrite(led, LOW);
char incomingByte=(char)Serial.read();
input+=incomingByte;
delay(10);
  }
  else{

if(input!="")
{
  flash(input[0]-'0', (input[1]-'0') *100);
}
input="";
  }
}

void loop()
{
  parseInput();
}


texts: How can someone determine the polarization of an antenna when you have the electric field components in spherical coordinates?

texts: All books define polarization using the field components in cartesian coordinates, i.e., with \$ E_x \$ and \$E_y\$. When we are in spherical coordinates though the thing becomes confusing because the unit vectors \$ \hat{r}, \hat{\theta}, \hat{\phi} \$ do not point towards constant directions and depend on \$\theta, \phi\$


texts: Do I definitely not want to to add a ground wire to this UART connection?

texts: I'm in a bit of a quandary here but it must be a common one.  I have two boards powered from the same battery through a "Y" cable; both boards have voltage regulators on-board. These boards are connected by UART rx and tx. My initial impulse was to add a ground connection for the UART, indeed both boards have a ground pin next to their rx, tx pins.  But now I wonder: would this be the wrong thing to do?  None of these connections is longer than 20cm/8in.


texts: Best way to set up a PT100 temperature probe?

texts:
I'm looking to build a temperature sensing product and want to use a nodeMCU or similar for the MCU module (something with an analog to digital converter), an LCD a PT100 RTD like the one in this photo:

I will need to measure temperature from 200F to 300F approx and I'm trying to find the most cost efficient way to set the PT100 up while still having good accuracy. I've learned some about voltage divider and difference amplifier and such which accompany normal PT100 usage. I would like to spend no more than $7 total on the temp setup, and the PT100 I'm using is already $3 so $4 left to spend on the rest, I'm willing to build some circuits or parts if I have to. to get accuracy within 1 degree F would be nice. Can someone help get me started on the right path? Thanks for any help!


texts: How do modern grid-tie invertes which are commonly found in solar pv panels and wind turbines actually stop islanding from occurring when the utility grid is down? I know there are a lot of methods which are used to prevent islanding but which method is the most common?


texts: What does the condition "f=100Hz" mean for the Gain Bandwidth Product?

texts:
In the LT6003 datasheet you can find the following information:

How do I read the Gain Bandwidth Product? I mean there is a typical bandwidth of 2kHz under the condition of f=100Hz and I'm not sure what this condition could mean.

I also did a practical test with the LT6003:

Simple buffer circuit
Supply voltage of 10V
Input signal: sine wave with 5V offset, 2Vpp

Interestingly the signal looks distorted for frequencies above of 150Hz.


texts:
In one of my circuit, the incoming variable voltage(8.5-24V DC) from the source will be first stepped up to 17V using a boost converter. The same output shall then be stepped down to different voltages for driving PMDC Motors:

Motor: 15.5V, current consumption 1.25A
Motor: 11V, current consumption 800ma

Following options are available:

(1). Single boost supply followed by two buck regulators.

(2). Two boost supplies followed by their respective buck regulators.

(3). Single boost supply followed by single buck regulator that steps down to 15.5V, and then followed by the other linear regulator that steps down to 11V for driving second motor.

The voltage drop from 17V to 15.5V is unavoidable due to diode and other losses. Considering the cost and durability, which option is the best?


texts: How should I step down 220V (ac) to 180V for a DC motor?

texts:
I have many treadmills motor of rating 180V 10A which I would like to use for power tools. Locally we have 220V ac 50Hz.

I thought of using iron-core transformers. But having one for 1800W+ is expensive and bulky.

There are also thoughts of using PWM. I know that high voltages probably help the motors overcome reactance quicker. But the pulsatile currents might decrease the torque. Can this be ameliorated with capacitors or inductors? Or it might run into impracticably large values required?

Another forum post points me to "single SCR in a phase-controlled half wave topology".

What would be the best option? Please point me to a good direction.


texts: Sharp IR distance sensor outputting consistently high voltage

texts:
I am on a steep learning curve, and a bit bamboozled by my sharp distance sensor (data sheet).  I am building a project with two distance sensors that signal an Arduino to operate a servo motor when an object comes into range. This currently works well, except that the sensors are outputting a relatively high voltage all the time, so I have to set a very high cutoff voltage in the Arduino code, or the motor is triggered all the time - eg both sensors are giving the Arduino numbers like 350-450 via the analog Read command (which should be about 1.7 - 2.1V as far as I understand it) all the time.  This means that if I set a cutoff of 550 or 600, the setup works, but only if an object is within 12cm of the sensor (which should be able to detect objects as far away as 80cm).  The sensors are not optically interfering with each other.

I am using an old computer ribbon cable to connect both sensors to the Arduino and I am suspicious that this is somehow causing noise in the output voltage, but the Arduino never seems to be read values less than about 300 (1.4V), and I would have expected noise to give some low readings sometimes.  Any help would be greatly appreciated.  I tried posting a circuit diagram, but as a guest user, the site won't let me.  Also, I'd post the code, but it is embarrassingly messy.  The Arduino and the servo have separate power sources with common ground, the sensors are powered from the regulated 5V Arduino supply, and connected to separate analog pins.


texts: Logic and communicating protocols for the RS485

texts:
I have an RS485 transceiver (reference manual here) attached to an FPGA that I need to program in Verilog. I am wondering what the logic is, for example, to send bytes. Looking at the reference manual (page 8), I understand that it might be:

Set the ON pin (A8) to logic high.
Set to pin DE (driver enable: A4) pin to logic high.
Start writing bytes to pin DI (driver input: A3), and voilà!

But this all seems to easy to be true. In particular, I'm wondering what the communication protocol (if any) should be. (For example, I'm thinking of start/stop bits.)


texts:
Trying to work out a simple LED indicator scheme for UART lines(3.3V) and wanted to know if this seemed appropriate. my signals baud rate can be vary from 9600 to 115200. I tried below circuit but not satisfied with the result.

The circuit is working but LED brightness is very low when it comes to high baud rates. How to get same brightness for low and high baud rates??
LED datasheet
Need suggestions on this circuit or any better option with less components?? using micro controller is not an option.


texts: Is this a 0.25% "precision" bleeder resistor?

texts:
In the AC input section of a PCB, I found a resistor (in parallel with an X capacitor) with 5 color bands:

        BLACK - GOLD - YELLOW - GRAY - BLUE(LIGHT BLUE)

Sorry because now I do not have anything to take a picture of it.

It's probably rated 2W and the PCB is made  in Japan.

If I interpret it from left to right, the result is a 400 MOhms 0.25 % resistor. This is clearly wrong for a bleeder.

If I interpret it from right to left, the result is still unreasonable(68.4 Ohm). The precision is unknown as black isn't coded for any tolerance.

How should I interpret this resistor ?


texts: Powering several amplifiers with one power supply

texts:
I need to power 5 industrial amplifiers for a project but I am not sure I can use one power supply for all. Here is the amplifier model I will use:
http://www.hbm.com.pl/pdf/a0114.pdf

And manual says "Supply voltage 15 ... 30 V DC (unregulated)" I also didn't get this. Does it mean I don't need a regualted input?


texts:
I have an FPGA design and the FPGA design has a signal called start which is always high. Here is how it works. I use the computer to send data over RS232 to FPGA, the start signal drops for a cycle and FPGA processes the data, and then FPGA send the data back using RS232. The above procedure repeats for 100 times. There is around 0.02 second gap for each rs232 send and receive.

The negative edge of start signal is used as trigger for the o-scope. For each trigger, the o-scope samples 10K points. The sampling frequency is set as 1GS/S. The FPGA clock is 25MHz.

Every time the start signal drops, I want to capture the waveforms and save each of them to files. (The files are saved on my computer harddrive over ethernet). The acquisition count is infinite. So for 100 negative edges, I should get 100 waveforms (100 files). But the o-scope only generate 3 files and each file only contain one waveform pattern I expect.

Is this because of the acquisition frequency? Or is there any options that can increase the acquisition frequency of the o-scope?

The oscilloscope model is Yokogawa DL7200. Mannual can be downloaded from
energy.ece.illinois.edu/equipment/dl7100.pdf


texts:
I'm trying to build a circuit that output an analog voltage proportional to the duration of a voltage pulse at the input like this:

My idea is to charge a capacitor with a current mirror with a switch controlled by the input pulse.
I have build this circuit so far.

But it has some issues that I would like you to help me with. Here is the output that I got:

First, I need it to start at 0V but it currently starts at 1.7V. I was thinking about shorting it to the ground when my input is at 0V but I don't know how to do it.
Also I would like to control the slope because at this point, it is way too big and it even stops at 2.7V, I think it is because the transistors is not in saturation anymore.
Do you have any advice?
Thank you

So I managed to have a lower slope by increasing the capacitor to 5pF (max allowed values) and also by decreasing the current from the current mirror. Such that my slope stays linear even for impulse of width 250 ns (max values).
Also I got rid of the offset by adding a switch and an inverter like this:

Here is what I got as output:

Which is already better because it enables the circuit to work for successive pulses, as Vout is reset between pulses.
But the main issue is that I wanted to keep my output voltage constant once my first pulse is done and only reset it on the rising edge of the second pulse. And by adding the switch with M6, I don't have the holding principle anymore.
Anyone with an idea to fix it?
Thanks


texts: why the PIV of full wave rectifier is 2vm

texts:
Peak inverse voltage (PIV) is the maximum voltage a diode can handle in reverse bias condition.

Why does the PIV of the diodes in a full wave rectifier need to be 2×Vm?
(where Vm is the peak voltage of the input AC signal.)


texts:
A datasheet indicates that a PoE IEEE802.3af Class 3 (<12,95W) is to power the system.  In my experience with DC devices, it is critical that the power source supplies:

correct voltage at the system terminal and
has the ability to source the required current

When selecting a POE source, is it good practice to confirm with the manufacture spec that the voltage and current provided by the source (I think it is) meets the above 2 criteria?  I am concerned that I did not see a voltage / current requirement in the spec


texts: Can a thermal fuse of a higher rated current be used safely?

texts:
I want to replace a 115°C 250V 2A thermal fuse used in a fan motor. The only fuses available locally are 115°C 277V 15A. Can I use the higher current rated thermal fuse?

Since it is a thermal fuse, I would expect only the temperature to matter...


texts: Trying to determine the SNR of a dirty signal

texts:
I have a dirty sine wave at about 8 Hz, and I want to figure out the SNR using MATLAB.

Would a reasonable approach to answering this question be to generate a clean 8 Hz sine wave in MATLAB and then use that to compare to the dirty signal to find the SNR? My thinking is that the clean sine wave is the ideal we would want.

I am not sure if there would be any phase issues in doing this.

I know MATLAB has an snr function, but I would like to be able to calculate it to compare to the function.

As a reference, the signal with noise could look something like this


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I have a project that uses this two wire RS-232 trick: http://circuitcellar.com/cc-blog/one-wire-rs-232-half-duplex-ee-tip-135/

It combines RX/TX into one wire while the other is ground.

However, I'm worried that if the user wires this thing up backwards, the +15V/-15V RS-232 voltages on SERIAL will be injected on GND(0V) and "let the magic smoke out".  Is there something I can do to protect GND from these voltages?

Here's half of the circuit, the other side would be identical to this, with SERIAL connecting to SERIAL and GND connecting to GND (hopefully) over a distance of about 5 to 30 meters.


texts: Why isn't the final float charge rate = 0 for a fully charged car battery?

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I had cause to charge a  12V    car battery recently.  I used one of these:-

To top up an 80Ah lead acid battery.  It initially started charging at ~4A.  I then left it floating for a couple of days.  The charger instructions clearly state that the float rate will never reach zero.  After 48 hours, the charger ammeter was indicating something like 500mA - 750mA (the meter's pretty poor). It didn't seem to be dropping at any discernible rate so I believe those instructions.

The battery was out of the car on a bench. So my question is where is all the electricity going?


texts: Confusion with the reasons collector area being greater than the emitter region

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Often I come up with the following reasoning when it comes to why collector has larger area than the emitter:

  For less power dissipation collector area should be more. In other
  words, when area is more, resistance is less for a given current and
  hence power dissipation is less.

  Usually base area < emitter area < collector area

But this argument confuses me because the collector and emitter passes almost the same amount of current. What is the point of saying collector needs to dissipate more power hence it needs to have greater area. If Ic and Ie are almost the same why wouldn't both regions dissipate the same power?


texts: 5v relay causing short circuit when turned off

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I am using an Atmega 1284 microcontroller and four 5v electromechanical relays to turn on/off appliances based on some sensors, time, etc. The ATmega has its own 5v power supply in parallel with an 8v supply that I am using for the relays. Both of these power supplies are getting their DC from the same transformer after its been rectified.

I am having an issue where the appliance that I am connecting to the relay shorts the entire circuit when turned off. It turns off the LCD screen and resets all the variables in the program on the Atmega. After about 2 seconds the circuit reboots to the my home screen but all the variables have been reset. I have measured the current coming from one leg of the transformer and before the appliance is turned on the current is at a steady 30ma. After the appliance is turned on it jumps to 70ma. After I turn the appliance off the current drops to about 15-20ma and shorts the Atmega.

I have tried to solve this issue by using an optocoupler/optoisolater in between the signal pin of the Atmega and the transistor just before the relay to try to isolate the branches as much as possible. That hasn't solved the issue. I have read all of the place that isolating the circuits is the best way to go to try to save the Atmega from damage. But how can I isolate the circuits when they technically share the same ground from the transformer? Or is that even the issue here?

Here is the circuit:

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texts: How does an inductor limit a voltage booster?

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I’m making a voltage booster to boost li-ion voltages 3v-4.2v to 5v with high current and a small footprint. I’m using TI’s Webench tool to help. It suggest a 1uH inductor for a 12A load, but if I increased the load to 15A, it recommends an inductor of at least 1.3uH. Out of curiosity,If I tried to run a 15A load through a circuit designed for 12A, what would happen? Would the inductor overheat trying to deliver the current or would it limit the current?

Below is a reference to what I’m making. A few components vary somewhat in value compared my own design, but remains vastly the same.


texts: Smart encoding of 2 dimensional sensor data

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I have a 2D position sensor which returns the pressed locations on it. For example, a sensor that 8x8 sized returns 64 points. It can give up to 1000 frames per second. All data must be send to GUI without lost. One frame consists of 64bytes and 64000bytes must be send in one second. Unfortunately, the communication speed with GUI is not enough for this.

Due to consecutive frames are very similar, i want to send more intelligently. This frames can be likened image/video frames.

How can I turn this similarity into advantage? I have a FPGA that is cyclone2 scale from Altera. Some people knows that this FPGA is not suitable for implementing complex math algorithms.

I need low cost,easy implementable, maybe not most effective but moderate algorithms that can be runs on mid-scale processor. Improvement %30 is acceptable for this work.

Which algorithms/methods are recommended for this work?

Note: Sensor which i use is an analog one, not a 0-1 manner sensor

The question can be changed as follows: What are the low-cost, easy implementable algorithms when encoding similar frames? Without thinking data sizes, please.


texts: Can I add an INA219 voltage\current sensor to this USB powerbank?

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I have a Raspberry Pi Zero in a small robot that I have been powering off a USB powerbank and it works great. Unfortunately when the USB battery goes flat the power is cut and the Pi crashes. I want the Pi to know when the battery is nearly flat and warn me. Ideally it could calculate how many hours of battery life I have left too.

I have bought an INA219 voltage\current sensor. My original idea was to put the 0.1 Ohm shunt in series on the 5V between the USB output of the battery and the Pi. This only tells me the current at the time I sample it, and the voltage feeding the Pi which is largely irrelevant as long as it stays within the USB voltage spec.

Having taken apart my USB powerbank (RavPower RP-PB19), can I put the INA219 between the Lithium ion cells and the boost converter\charging circuitry shown? Specifically, can I cut this red wire in the photo and put each cut end of the wire into the blue screw terminals on the INA219 sensor to be able to read the current cell voltage of 3.6V ish and therefore work out roughly what percentage the batteries have left in them?