texts:
I'm studying filters. In particular, I'm studying low-pass to high-pass filter transformation. I know that you only need to design an equivalent normalized low-pass filter and then, by using a suitable variable transformation, you can obtain the desired high-pass filter. Here a slide of the lecture:

Question: in this slide, the equivalent low-pass filter has an attenuation of 1dB at the normalized frequency 1. How is it possible to apply the Butterworth approximation? Indeed a normalized Butterworth filter necessarily has a 3db attenuation at the normalized frequency 1. It's impossible to have 1dB at the normalized frequency 1 for a normalized Butterworth filter!


texts: For large appliances I usually see a 3-prong plug while smaller electronics will use a 2 prong wall wart with a DC barrel. When designing electronics, how do you know if you'll need an earth ground? Are the two prong designs inherently more dangerous?


texts: Sloppy DC pre-filtering for 24V → 5V 1A Buck converter

texts:
I have done DC converters before, both the curious way (AVRing it) and the lazy engineer's way (applying a datasheet formula) but it was always from nice DC sources with a fairly big filter cap.

Now, just for the reason of size, I'd like to go with a much smaller filter cap on the input, so the DC will have much ripple on it. I imagine this is going to muddle common buck-converter designs.

I'm looking for advice from people who did such a stunt before. What to look for to select a buck converter chip which behaves tame in such a situation?

EDIT: I found it's worth to note, these are many tiny boards needing +5V, and supplied 24VAC from a central distribution.


texts: Systematic construction of the ODE system of a circuit containing opamps

texts:
I want to compute the voltages and currents in a circuit containing R,L,C, opamps and voltage sources. I perfectly understand how to do this for circuits containing only R,L,C and voltage sources, using mesh or nodal analysis. But as soon as a circuit contains an opamp, I'm stuck.

In the literature I found, it is explained only by example (typically the inverting and non-inverting opamp), but no general "algorithm" is given.

Can somebody please explain to me how to construct the DE system for circuits of arbitrary size which contain opamps?


texts: Why do operational amplifiers have an output current limit?

texts:
From Sedra-Smith:

  Another limitation on the operation of op-amps is that their output current is limited to a
  specified maximum. [...] This, of course, has to include both the
  current in the feedback circuit as well as the current supplied to a load resistor.  If the circuit
  requires a larger current, the op-amp output voltage will saturate at the level corresponding
  to the maximum allowed output current.

The meaning of the paragraph is clear, but I still don't get why op-amps have such a limitation on the output current. How can you deduce that from the internal circuitry of an amplifier? For example, if we consider the two-stage CMOS op-amp below, is there a way to calculate the maximum output current?


texts: Unexpected results when trying to amplify voltage across a wheatstone bridge

texts:
I am working on a project, and am trying to amplify the voltage across wheatstone bridge. Here is the diagram:

where \$R_1 = 1,000 \Omega\$

\$R_3 = 10,000 \Omega\$

and \$R_2\$ is a potentiometer, set so that the voltage across the bridge is 10 mV

The gain of the amplifier is simply \$R_3/R_1 = 10\$, so I expect an output voltage at \$V_{out}\$ of 1V.

I do not see 1V out, I see somewhere around 1.5V, and I am certain that whatever the problem is has something to do with the fact that the voltage across my bridge doesn't stay at 10mV when connected to the amplifier. When I connect the bridge to the two leftmost op amps, and check the voltage across the bridge again, it is around 45mV.

Why is this? I've checked my amplifier circuit with classmates and rebuilt it several times, I can't tell what might be wrong. What might be causing such an issue?


texts: Inverting charge pump with boost converter loading characteristics

texts:
I've added a test inverting charge pump to an LMR64010 based boost regulator. This regulator outputs +12V (exact value is 11.88V) from a 7.4V battery pack.

This is a notated image from a Maxim application note showing what I did. The output capacitors are whatever I had handy - 22u and 10u in parallel:

With no attached loads I get a value for -V of -11.65V. The immediate issue I noted was with an attached negative load of 1K for approximately 12mA, the voltage immediately drops off to -6.5V.

Varying the load on the positive side (with a fixed negative load) I get:

Neg Load    Pos Load    Neg output (V)
--------------------------------------
   1k         inf          -6.50
   1k         3.3K         -9.95
   1k         1.0K        -10.30
   1k         500R        -10.38
   1k         250R        -10.40

So a rapid convergence to about -10.30 volts at a load that matched the negative load. Then little or no rate of return below that.

Is this a correct statement then: "an inverting charge pump must have a matching load on the boost converter output".

Is this how I should design the completed circuit (which is providing negative biasing for an opamp - not my design) ? So I'd put a 1K resistor across the +12V rail and then specify that loading (12mA or so) as a max loading for the negative rail?


texts: ATMega328: How to select alternate function on a pin

texts:
This might be an easy question, but I couldn't find an answer to it in the Alternate Port Functions section of the ATMega328 datasheet (page 80)

Take pin PB3 as an example. As well as having a use as a GPIO pin, it is also wired to MOSI, OC2A, and PCINT3. How do you select which signal is wired to PB3?

Specifically, if I wanted to use PB3 as a GPIO pin, but I was using timer2 for some other function (which would have a side effect of setting and/or clearing OC2A), will the two signals interfere, and how would I avoid that?

Thanks


texts:
I have build a circuit:

The power source is a battery. The rectangle (below the amperemeter) is a resistance.

I have measured U (in Volt) and I (in Ampere) for the whole discharge process. Now I would like to calculate the internal resistance of the battery during the discharge process.

How can I do it?


texts: How does an astable multivibrator LED blinking circuit work?

texts:
I am a beginner in electronics. I come to know about the oscillator using RC circuits (capacitor charge and discharge and time constant tells the behavior of circuit).

Then I saw the following circuit that blinks 2 LEDs timely in sequence.
Will somebody explain its working? I know that capacitor will charge and during charging the LED will be off and when they discharge they will turn on the LED.

But why are the transistors there?


texts:
A colleague of mine created the following circuit with the 3x 5A fuses for protecting the power connector pins from oxidizing and melting the connector plastic (we had some cases, when the connector melted a bit, probably because of moving contacts/vibration etc.).

The connector is specified for 8A/pin, we need max. 15A worst case. I suggested him to put in the 15A fuse because of this. I am still unsure, is this protection safe?


texts: Reverse-engineering RS485/Mechatrolink-II front-end design

texts:
I'm trying to reverse-engineer Mechatrolink-II front-end circuitry. Its physical layer is simple RS485 (with isolation transformer) running at ~10Mbps.
Here is the schematic I obtained from the PCB of a Mechatrolink-II-compliant device.

And I have two questions about it.

The transformer

Proteus does not have exact models I needed, so two transformer models (TR1s) actually represent a single "Mechatrolink-exclusive pulse transformer" (http://products.mechatrolink.org/en/product/detail/id=170), in other words, their cores are not separate.

Now suppose I want to attach a sniffer (or even a slave at some point in future) to the existing bus. Obviously, I can't buy this exact transformer (at least less than several hundreds of them), but I've plenty of Ethernet transformers rated for (at least) 10BASE-T, which is, speaking of pulses, roughly the same 10Mbps and the windings are the same too. Can I use them?
Can I omit the isolation transformer altogether during prototyping, taking into account relatively short length of the sniffer's cable and a floating supply (that can share ground with other devices, if needed)?
And also, why Mechatrolink engineers might have chosen to place two windings on the bus side and connect them with a PCB trace, instead of a single winding like in Ethernet?

Two transceiver ICs?

I can't quite understand the purpose of all that RLC-stuff going on after the transformer. If there was only one IC, I would I've thought it's there to correct transformer imperfections (overshoot etc). I've simulated the behavior of the circuit, assuming that the transformer replicates incoming signal good and outputs almost square (<10nS rise/fall time) 100nS pulses (which, as far as I understand, it should, if chosen right).

Here are 3 possible scenarios (scaling Proteus screenshots is always a pain, open them in full size). Upper-left plot is the pulse source, below are U18's A and B, on the right side are U25's A and B, color is consistent.

In any case, U18 will decode the bits just fine, am I right? Then why is there U25? Their receivers' outputs are connected to the same ASIC, U25's Y and Z appear unconnected.
By the way, how does the system distinguish WAIT and a repeating bit (receiver output obviously lacks the third state)? Only by using a fixed (or transmitted) packet length protocol?


texts: Does the Shockley Ideal diode equation involve drift current?

texts:
I've encountered a contradiction in semiconductors.

The ideal diode equation considers saturation current (the current when applied voltage is reverse biased to the diode). I thought that saturation current was due to drift.

However, on the other hand, the derivation of the Schockly ideal diode equation assumes no drift current in the transport equation. See here: https://www.pveducation.org/pvcdrom/solving-for-quasi-neutral-regions

Where is my misunderstanding?


texts:
I want to establish an USART communication between my Atmega32a chip and my computer but there's something I don't understand.
As I read the datasheet the UBRR register is a 12 bit register but is split into two 8 bit registers:UBRRH which cointains the four most significant bits and the UBRRL which contains the eight least significant bits of the USART baud rate;
My question is:Why I have to shift BAUD_PRESCALLER with 8 at right? I don't understand how this all works :(
The example if BAUD_PRESCALLER is 120,in binary it would be:0b01111000 so
0b01111000>>8 = 0b00000000; => Am I wrong somewhere?

void USART_init(void)
{
    UBRRH = (uint8_t)(BAUD_PRESCALLER>>8); <--- this line
    UBRRL = (uint8_t)(BAUD_PRESCALLER);  <-- and this line
    UCSRB = (1<<RXEN)|(1<<TXEN);
    UCSRC = (1<<UCSZ0)|(1<<UCSZ1)|(1<<URSEL);
}

I will atach the datasheet for UBRR register:


texts: Are there risks in connecting the power pins of separate development boards?

texts:
I am connecting the SPI bus pins of two development boards:

NVIDIA Jetson TX1
Cypress C8CKIT-030

They are each connected to their own wall-wart power supplies. I have confirmed that the connected pins are all operating at 3.3v. However, I know that "3.3v" is only in reference to their own grounds.

Are there any potential risks to connecting the VDD (3.3v only) and ground pins between the boards to make sure the voltages match up correctly?


texts: Oscilloscope Probe Compensation Not working

texts:
I just received an Owon SDS7102v 100 MHz oscilloscope.  After checking out the menu structure I decided to compensate the probes.  Channel 2 seems to work fine with either probe.

[Channel 2 properly compensated, 20mV/div]

Channel 1 on the other hand is a different story....  There is quite the hook across the top portion of the square wave.  I get the same result using either probe.  Any ideas what is causing this?  Is the input bad?  Is there anything I can do to try and fix this issue?

I have a warranty but I just received the scope so I'm not too excited about sending it back to China for repair....

[Channel 1 probe compensation, 20mV/div]


texts: VHDL - testbench hangs due to a problem with nested for loop

texts:
I encountered a problem when trying to simulate a D flip-flop design.

Here's a snippet of my testbench code:

d_ff_tb_process: process
begin
    for D_idx in std_logic range '0' to '1' loop
        input <= D_idx;
        for S_idx in std_logic range '0' to '1' loop
            set <= S_idx;
            for R_idx in std_logic range '0' to '1' loop
                reset <= R_idx;
                wait for 10 ns;
            end loop;
        end loop;
    end loop;

    wait;
end process d_ff_tb_process;

clock <= not clock after 3 ns;

And here's the simulation:

Question:
As you can see, the simulation halts at 70 ns, even though it should stop at 80 ns (simulation time in ModelSim is set to 100 ns). I believe that for some reason wait for 10 ns; is not being executed when D_idx = '1', S_idx = '1', and R_idx = '1'. Why is this happening and how do I fix it? Thanks


texts:
I’ve created an airgun bell target and attached an led light to it which lights up for just a second when the target is hit.  However, I was wondering if there was an easy way to make the light stay on for a few seconds longer with some type of delay. I know nothing about electrical engineering so I maybe over my head already.

I’m using a push button led light from the auto section a Walmart which uses 4 AA batteries.  I cut the push button off and attached one wire to the bell and the other to the paddle.  When the paddle hits the bell the bell dings and the light lights up.


texts: Recording heading with magnetometer that is inside spinning object

texts:
I'm wondering if it is possible to record the heading of an object (call it a ball) that has a 3 axis magnetometer in it? obviously if the ball was still it would be simple, but as the ball is spinning it makes it a lot more difficult.

I'm trying to get the heading direction of the object so I know which direction it is traveling in and if it is experiencing drift due to wind or other external conditions (such as the direction of spin).


texts: What kind of circuit board standoff is this?

texts:
I have a PCB with several broken standoffs like this:

The bottom of the part is where it broke - it used to be a plastic 'foot' that would have been relatively flush to the case that the PCB is mounted in.
It looks like you'd assemble this by inserting from the bottom, first through the case and then through the PCB. It snaps into both.
I've searched on ebay, images, other shopping sites, etc. and haven't found anything similar; probably I'm not using the right search terms. There are plenty of standoffs of other types, but none with this dual snap-in design that I've found. (Not even certain that "standoff" is the correct term).
Thanks


texts: Using p-Channel MOSFET as a Switch to turn load on / off via BeagleBone Black GPIO

texts:
Is this the correct way of using a pMOSFET as a High Side Switch?

I need a Load Device to be turned on/off (Vin Pin). The Load Device requires 5v 700mA power to run.

My logic is, when the beaglebone-black comes on, the GPIO is ON (3.3v High) by default, so the Load (Device) Gets 0v.

Once the board boots up, the startup Script turns the GPIO Pin low, which gives a high signal on the load side.


texts:
Is a computer wired controlled sd card or USB flash drive feasible (like the Scylla cards connected with a laptop in prison break)?
It means there is no storage on the flash drive itself. When a computer reads the flash drive it actually reads from another computer being wired connected with the flash drive.
Can we achieve this function by running software or adding some kind of adaptor to simulate the flash drive storage and the data in it?
Like this scenario, you wanna try a new os on raspberry pi you have to burn the IMG to the sd card. If there is some kind of adaptor you can just connect to the sd card slot and set up a software on your computer, you can just boot the raspberry pi without waiting several minutes to burn an image.
I just found a thread from superuser is-there-software-to-fully-emulate-a-usb-hard-drive.
Update after bobflux answered: At first I thought it would be a hardware-related question but now it's basicly a software-related question.
configure-linux-system-as-an-otg-device
use-a-linux-directory-as-a-usb-otg-device-to-an-android-phone
make-a-computer-act-as-a-virtual-usb-device-for-other-equipments


texts: Build a "gate" that passes only one risinge edge

texts:
Basically, I want to build a circuit that takes an input. When the input is 1, the circuit outputs a 1. However, on the next rising clock, it will output a 0 for the rest of the time, regardless of what the input is.

if input = 000000000100000, output = 000000000100000
if input = 011111, output = 010000


texts:
I am designing a circuit which involves taking readings down in the uV range, anywhere between 90uV and 2mV. I am then needing to sum 2 voltages together to give me my resultant voltage.

I need this as accurate as possible so I decided to use a chopper stabilised op-amp for buffering the low voltage and also as the summing amp as I was impressed with the extremely low offset/drift etc. I thought this would be a much better solution than to use a standard op amp which could introduce potentially large errors in my readings.

The problem I am getting is that the chopper op amps seem to be giving me quite a bit of noise in my readings. Annoyingly, if I switch to a standard op amp, I get clean readings, but they aren't as accurate. If I use the choppers, then I get a noisy reading.

I know they use capacitors to offset the errors, so I would assume that maybe has something to do with it? If it is to do with that, why are these things advertised as having such low offsets if they are noisy in the lower voltage ranges?

If anyone has any suggestions on making it less noisy, I would love to hear it! The things I have tried so far:

1 - Swapping the chopper amps for normal op-amps: Cleaner output, but with larger error.

2 - RC and LC filters on the outputs: Didn't seem to do much at all.

3 - Changed decoupling capacitor values (higher and lower): No difference

4 - Placed different values of capacitor on the output: As the capacitor value increased, the error seemed to get larger annoyingly (perhaps it would have then needed another buffer as I am unsure how good they are at driving capacitive loads)

Any help would be appreciated!

The op amp I am using is the TLC2652AC (which apparently has a 1uV max offset which is what made it so appealing).


texts: If a SoC is given more memory then it is able to use, how does it deal with that?

texts: Say it can only use 2GB's, and is provided 4, does it only use half, or not use any of the ram?


texts: What are important design parameters for Opto-isolators?

texts: I want to use an opto-isolator in my circuit. I found Opto-isolator 6N135 matching with my design voltage requirement. datasheet (http://www.vishay.com/docs/83604/6n135.pdf). But datasheet seems to be confusing. I want to know basic and important design parameters for a opto-isolator (with reference to data sheet). Can someone help me for the same ?


texts:
I'm working on making a detector using a Thermopile. Here's a link to the page and datasheet. Link
I've looked through and am not sure what the values for Ra, Rb, Rc, and Rd are supposed to be. If any value. Does it depend on the application?
What does Vth stand for? VThevenin?
Thanks,
Luke


texts: Logical Effort in complex circuit - Output capacitance

texts:
As part of a VLSI course I was asked to estimate the delay of an ALU, similar to the one described in the picture, using Logical Effort method.
I calculated the delay of the critical path through the ADD/SUB block, but I am not sure how the output capacitance of the multiplexer is calculated. Do I need to take into account all the blocks that enter the multiplexer in order to get the output capacitance needed to calculate the delay through ADD/SUB block only? Or can I just ignore the inactive blocks when calculating the delay of an active block?

Thank you


texts: Need to keep re-soldering SMD resistors on PCB

texts:
I made a PCB to scale a +-100V signal into a 0v to 3.3V signal that I could read using an ADC on a microcontroller(see link for idea.)
I used this solder paste flux to help with the soldering.

After soldering 16 of these, a bunch resistors were shorted. I got some tips from a friend that is good at soldering (use a microscope and go slowly) and got them all working.

Now though every few days a voltage divider will either get stuck at 3.3V or ground or somewhere in the middle.
 If I re-solder the resistors it'll work again. Even if I just reflow the solder on the resistors it will start working again.

Any idea why they keep breaking after a few days?
Any ideas how I can get them permanently working?

The resistors are all 0603 and 0805 footprint.

FYI: I used two 150k ohm resistors instead of one 300k resistor because I was worried about a 100V drop across just one.


texts:
I have a PC which I backup to an external USB3 HDD drive from time to time, I manually connect the drive whenever I "remember" to do the offline backup. I don't want to keep it connected all the time in hope that it won't wear-down fast also protect it from accidental modification.

However, I would like to automate this process as well and have this backup done frequently and I was searching to see if simply disconnecting USB V-BUS is enough and also safe to simulate disconnecting the USB and that it will not cause any issues. I have seen similar questions but couldn't find any that matches my concerns.

I am thinking about using a CMOS P-channel (with bypass caps before and after) to control the Vcc, but the D+, D- and GND will remain connected!
The USB plug is designed so that VCC and GND will connect first before the data lines, in my solution that won't be the case and I don't know what that might lead to.

Will this be safe? or should I just look for USB3 switches instead.


texts: MAX232 chip by TI not functioning correctly?

texts:
I'm trying to use this to convert rs232 levels from my gsm modem to 5v TTL. I was struggling to get it working. So I devised a test to see if I even got any form of communications. My custom Arduino is based on  duemilanove design hence it uses ft232rl. I've unplugged my arduino chip. Now I'm just using the ft232rl ttl pins which are connected to max232. I've connected the T1OUT to R1IN. My theory is I can create a loop back so I should get back whatever I send using the terminal within arduino IDE. I've double quaduple checked my connections using sparkfun and various other sites. But nothing happens. Why?

I get 8.5v on  pin2 and -7.5 on pin 6 and according to the datasheet thats within spec. I've powered it using 5v. I've decoupled the VCC.

If you could come up with some common pitfalls with this chip, I will be extremely grateful. Btw I don't have a rs232 port on my pc.


texts: How do I successfully connect a 3 phase motor using single phase 220 v?

texts:
I have a plastic crusher with a three phase motor and I will like to operate it using single phase 220v.

Can anyone please help me out with instructions on how to connect it?

Also, I want to know if I will be using two capacitors?
(start capacitor and a run capacitor)

Can I also know the exact capacitor(s) value which I will require?

I have attached a picture of the label of the motor, a picture of the motor contactor and a picture of the motor wiring.

Thanks in advance.


texts: Passivity of impedance matrix on the imarinary axis

texts:
According to this paper, Section V-C, a rational impedance matrix Z(s) is the impedance of a passive lumped system if and only if the following four conditions are satisfied:

1) each element of Z(s) is dedined and analytic in \$Re(s)>0\$;

2) \$Z(j\omega)+Z^H(j\omega)\$ is nonnegative-definite for all \$\omega\in R\$;

3) \$Z(-j\omega)=Z^*(j\omega)\$;

4) asymptotically, \$Z(s)\rightarrow As\$ in \$Re(s)>0\$, where \$A\$ is real, constant, symmetric, and nonnegative-definite.

Condition 2 ensures positive dissipated energy. Condition 3 ensures real impulse response in the time domain. My question is about the exact meaning of the fourth condition. For example, suppose I have a one-port which consists of nothing but a series of a positive resistor \$R\$ and a capacitance \$C\$. The input impedance, which is equivalent to the 1x1 impedance "matrix", is simply \$Z(s)=R+1/sC\$. So asymptotically \$Z(s) \rightarrow R\$, which is not in the form of \$As\$, for whatever \$A\$. But this simple one-port is doubtlessly passive. In this case, should we consider the 4th condition as violated? Or, does it actually mean that the asymptotic behavior of \$Z(s)\$ cannot grow faster than \$As\$?


texts:
I'm trying to design a circuit to measure the ambient visible light (380nm to 750nm). Accuracy isn't too important.

I've been looking at photodiodes, but I'm not sure how to connect them up.

I need the following requirements from my circuit:

low power
low accuracy
low cost photodiode (e.g. this on digikey)
AD convert signal for uC

I was thinking of some sort of voltage divider with a photodiode in the circuit? Then connecting this to an op amp, before going to the AD pin of a uC.


texts: Experiment with pull up/down resistors gives unexpected results

texts:
The wikipedia article on pull-up/down resistors provides this image:

along with some explanatory text:

  ... the circuit shown [in the picture] uses 5 V logic level
  inputs to actuate a relay. If the input is left unconnected, pull-down
  resistor R1 ensures that the input is pulled down to a logic low. The
  7407 TTL device, an open collector buffer, simply outputs whatever it
  receives as input, but as an open collector device, the output is left
  effectively unconnected when outputting a "1". Pull-up resistor R2
  thus pulls the output all the way up to 12 V when the buffer outputs a
  "1", providing enough voltage to turn the power MOSFET all the way on
  and actuate the relay.

I had enough components on-hand to build this circuit (mostly) and am seeing some unexpected results when I measure it.  So I'd like to describe what I'm seeing and ask some questions about it.

First, I put a Texas Instruments SN7407N chip on a breadboard and powered it with a 5V supply.  This chip names the input side of the buffer A and the output Y.

simulate this circuit – Schematic created using CircuitLab

At this point, if I connect a voltmeter to the circuit at point A (between A and GND), it reads about 1.9V.  The datasheet for the 7407 indicates a low level should be 0.8V and high should be 2V.  So 1.9V is somewhere in between and indeterminate.  Since I haven't connected anything to A, having an indeterminate value at this point seems reasonable.

Strangely, if I measure the voltage at Y, it reads 1.4V.

Q: If a buffer's output is supposed to mirror its input, why does it not read the same 1.9V as A?  Perhaps I shouldn't be concerned since A and Y aren't connected to anything, but I do like to understand what is going on when possible.

The wikipedia article says:

  If the input is left unconnected, pull-down resistor R1 ensures that the input is pulled down to a logic low.

So the next thing I did is connect a 5.1kΩ pull-down resistor R1 to A like so:

simulate this circuit

Now, when I measure the voltage at A, the meter reads 1.6V (a drop of .3V).

Q: Since the pull-down resistor is supposed to create a low-level at the buffer's input, why doesn't it show something closer to 0V at A?

Measuring at Ynow shows .9V, which maintains the roughly .5V difference I saw when nothing was connected, but the voltage at Y still appears to be too high to present a true low condition.

I am aware that the buffer is an open-collector, and now I'm wondering if the reason I'm seeing unexpected results is because Y isn't connected to anything.

So I tie a pull-up resistor R2 to Y like so:

simulate this circuit

Now, when I measure the voltage at A, it still reads about 1.6V.  However, the voltage at Y is now 5V!  Does this represent a high logic level (since it's greater than 2V), or is there an error in the way I've hooked everything up since it is now reflecting exactly the VCC voltage?

I realize I haven't finished the circuit exactly as the one above from Wikipedia shows (i.e. no connected N-channel FET or relay), but the values I see by measurement already don't make sense.

Should I have connected the rest before writing this question?  If the answer is yes, I think I'll be even more confused because that implies the load dictates the logic values (which of course it shouldn't).  I thought I should be able to establish clear states simply with the use of pull-up/down resistors.

Thank you!


texts:
I got some helmet speakers for free from my work. I was hoping to just install them and them plug in a 3.5mm connection to my phone and play away. But the speakers have a mini usb since you "need" some kind of main hub to connect it to. So i was wondering if there is a way to convert it?
My soldering skills are pretty good but I'm not an expert. Maybe cut the wire and solder a 3.5mm wire would that work?
Or if anyone know of any adapter that will work? Best Regards!


texts: calculating transistor base resistance in parallel circuit

texts:
I am trying to use Raspberry Pi GPIOs to turn on and off optocouple switches controlled by transistors.

I really have no idea what I am doing (programming the thing okay. Wiring it? Not so much). I think that the base resistors are my problem, but I really don't know.

There are 20 switches.

Each one is connected to a separate GPIO pin at 3.3 Volt Output. (I have only drawn 3 for clarity)

The Optocouples require 1.2 V at 20 mA.

I really think my problem is the 10k ohm resistors but I don't have a clue how to calculate the needed resistance here.

Please be kind, I know it is a stupidly simple circuit and question.  But I don't know how to go about this.


texts: Is it important to determine the type of solder used on a board, and if so, how?

texts:
I'm asking this in the context of desoldering consumer PCBs, with lead vs. lead-free solder. My concern is twofold:

lead-free solder usually has a higher melting point, so the temperature should be set slightly higher to shorten the desoldering time and hence reduce the total heat transfer.
since solder wets/tins the soldering tip, there's a chance you'll have a solder tip tinned with a different type of solder than the one your are processing, which might be a bad thing.

Are those concerns important enough to consider them when desoldering, and, if so, how can leaded solder be told apart from lead-free solder?

Note that answers with a fairly surefire solution are preferred over heuristics (e.g. visual identification).


texts: How does a NAND gate work? (Very basic question)

texts:
I'll preface this question by saying that I am a software developer just starting to learn the basics of electronics, so it's very likely I'm missing some fundamental intuition here.

Below is a mechanical NAND gate with two switches. I think it's supposed to be obvious that when the switches are closed, the output Q is 0 rather than 1. I don't see why this is.

I see that when the two switches are closed, there is a path from V+ to ground, and that current will flow to ground. But there's also a path from V+ to Q, so won't some current still flow to the output, putting it in a 1 state?

The intuition I'm using (which may be totally wrong) is this:

Current acts like water gushing from V+ down all available paths.
At a junction, current will flow through both paths in an amount inversely proportional to resistance. In this case, both paths have no additional resistance so they should split the current equally.
The boolean equivalent of a 1 is that current is flowing through a point.

Please help me understand what I'm missing! And if you can point me to a book or online resource explaining these fundamentals, that would be very helpful. I've tried looking at a lot of "circuit tutorial" content on Google, but surprisingly haven't been able to resolve my confusion here.


texts: Verify relays soldered onto a circuit board

texts:
Hello
I need to verify a couple of relays for proper functionality. They are soldered onto a PCB as shown in the attached image - labelled RELAY 1 and RELAY 2.

Online tutorials take a stand-alone relay and energize it via a DC power source. Can that be done here i.e. using a DC source to only apply voltage to the appropriate relay terminals while they are still soldered?
What is the normal procedure for verifying relays soldered onto a PCB?

Thanks


texts: Software PWM on a PIC10F202 (looped fading LED)

texts:
I'm currently trying my best to code a software solution for PWM on a PIC20F202 but I have one issue. I'm trying a looped fade out and fade with a LED and it's doing fine and very smoothly but on somewhat regular intervals, there is a hard bump in the fading sequence which I can't explain by any means. I have looked at the code so many times, I checked the contacts on the breadboard, I don't know what else to check for.

/******************************************************************************/
/* Files to Include                                                           */
/******************************************************************************/

#if defined(__XC)
    #include <xc.h>         /* XC8 General Include File */
#elif defined(HI_TECH_C)
    #include <htc.h>        /* HiTech General Include File */
#endif

#include <stdint.h>        /* For uint8_t definition */
#include <stdbool.h>       /* For true/false definition */

#include "system.h"        /* System funct/params, like osc/peripheral config */
#include "user.h"          /* User funct/params, such as InitApp */

/******************************************************************************/
/* User Global Variable Declaration                                           */
/******************************************************************************/

/* i.e. uint8_t <variable_name>; */

/******************************************************************************/
/* Main Program                                                               */
/******************************************************************************/

#define _XTAL_FREQ 4000000

void main(void)
{
    /* Configure the oscillator for the device */
    ConfigureOscillator();

    /* Initialize I/O and Peripherals for application */
    InitApp();

    /* TODO <INSERT USER APPLICATION CODE HERE> */
    const uint8_t MAX = 100;
    uint16_t oncount=1;
    int8_t delta=1;

    TRIS = 0b111101;

        for(;;){

                GPIO = 0b000010;
                for(uint16_t i=1;i<oncount;i++)
                    __delay_us(1);

                GPIO =0;
                for(uint16_t i=1;i<(MAX-oncount);i++)
                    __delay_us(1);

                oncount += delta;

                if(oncount == MAX)
                    delta = delta * (-1);
                if(oncount == 0)
                    delta = delta * (-1);

        }

}


texts: How to solve a circuit network involving a resistor parallel to a voltage source using only nodal analysis?

texts: I have been stuck on this for the past week and this week i just dont seem to find out what am i doing wrong. Please help me spot my mistake. Here you can find  My circuit on multisim. Please provide me with as much details as you possibly can nothing you write will be considered redundant by any word and help is appreciated much.


texts:
I want to measure grid voltage with AMC1200b. I used a resistor voltage divider and I lowered grid voltage from 110v(rms) to 110mv(rms). I fed the 110mv(rms) signal to AMC1200b (for the first side of AMC1200b I used a 5v power supply and for the second side I used an isolated 3.3v power supply). The problem is, based on the datasheet, the gain should be fixed and 8, but it is 4 and I am losing some resolution for sampling.
I also used a filter for the shunt resistor like it was in the datasheet( 2*12ohm resistors + 330pF capacitor).
Could you please let me know what's wrong with the circuit?


texts: Do DC-DC boost converters that accept a wide voltage range always require feedback to maintain constant output voltage?

texts:
I've never taken a formal power electronic course and am trying to learn a little bit about boost converters.

I assume there are different boost converter designs based on what you're trying to do, and I believe I understand the basic principle for a simple step up DC-DC converter, however I'm struggling to understand how different variations operate. Specifically, I'm trying to understand how a boost converter that takes varying DC voltage levels and is able to maintain a constant output voltage.

Referring to this Texas Instruments DC-DC boost converter, you will see that it can take an input ranging anywhere from 0.9 - 6V. There are several different converters apart of the TPS6102x family, and I'm specifically interested in the TPS61025 which accepts a 0.9 - 6V input voltage, but will output a constant 3.3V. Other chips in the family allow for variable voltage output in which you can use a resistor divider to 'program' the output voltage.

In my case of using the TPS61025, I will not be using the 'FB' pin since the chip can't be programmed to output a certain voltage.

So getting to my question, when a DC-DC boost converter accepts varying input voltages, can it be assumed that there will always be some kind of internal feedback to maintain that output voltage? If a chip were designed to step up a precise voltage of 1.5V to 3.3V, I would assume that it could be implemented either open loop or closed loop since the chip can make the assumption that it will ONLY have one voltage (1.5V) to ever worry about. However in the case of accepting a wider range of voltage inputs, the chip can make no asssumption.

TLDR: Do DC-DC boost converters that accept a wide voltage range input always rely on internal feedback to maintain a constant voltage output?


texts: Is it a problem with SPI bit-banging or the mode

texts:
After hours of debugging the SPI send bit-banging function and probing, I have come to a point where I could no longer understand whats causing the Si4455-RFIC to always return response of 0x00, including for CTS command. However I have hypotheses for this problem cause, which are:

I believe it would be mainly due to the Si4455 not being able to process the commands and hence returning 0x00
It's not processing the commands because it's having trouble interpreting it, because there is something wrong with my SPI bit-banging function or the data I am sending.

According to the Si4455 datasheet here, it states the following on page 23 regarding the SPI mode of Si4455:

And shows this SPI timing diagram on page 22:

From the above information, it is understood that the host MCU  must put the data on the SDI of Si4455 during the falling edge of clock, so that the Si4455 can read the data on the rising edge of the clock. And the same applies with the Si4455. Based on this, I wrote a function that sends the data (Commands bytes) to the slave device i.e. Si4455 using the simple bit banging method as shown below:

void Spi_Send (unsigned char Spi_Data)
{

  unsigned char index=8,m,maskval=0x80,k;
  m = Spi_Data;
  while(index)
  {
    SPI_CLK_LOW;
    k = (maskval & m);
    while (k == 0X80)
    {
      SPI_SDO_HIGH;
      k = 1;
     }
     while (!k)
    {
      SPI_SDO_LOW;
      k = 1;
    }
    m = m<<1;
    index--;
    SPI_CLK_HIGH;

      }
   SPI_CLK_LOW;
  }

The below scope image shows the command and CTS response transaction that does the following (Yellow Signal -> Data and Blue Signal -> Clock:

  1. Make NSEL Low
  2. Send 0x44 Command -- That takes 8 Clock Cycles
  3. Generate additional 8 Clock Cycle to read CTS Response
  4. Make NSEL High

Below is the scope image of how I am handling the chip select between each transactions to read the CTS response (Yellow -> CS and Blue -> Clock):

We have already built the first prototype and have got this chip to work with the TI CC3200, but for some reason I am having trouble getting it to talk with the ESP8266EX. I'd appreciate if folks can please review the signals in the scope I have attached and assist/advise me as to if there is anything I am missing or, is the way I am handling the signals wrong? If we cannot resolve this issue in this week, then we may be forced to evaluate some other module, which would be sad, since we have got this chip working on our first prototype with TI CC3200.

Update 1: Please see the hardware schematics of the ESP8266EX Launcher Board Here - Jump to Page 42 to 46 for Schematics. Note that there is a 1uF capacitor connected to GPIO 13 i.e MISO line after the reset key. I have removed this capacitor, since it will not allow for SPI communication.

Update 2: I have captured the timing variations comparison between TIcc3200 and esp8266ex signals as shown below, w.r.t Si4455 SPI timing diagram above.


texts:
Professor was teaching us the basics of opamps today, he went quite quickly over the frequency-dependency of opamps.
He said the gain response to frequency was approximately a "first order response", can someone explain what it is and why this is true for opamps?


texts:
I've soldered a DC power pigtail to a string of 5V LED lights. When I connect the pigtail to the appropriate power source all of the lights flash very brightly and briefly just as the male end goes into the female, but then turn off once the male end has gone the slightest bit further into the female.

I've tried holding the male at the very tip of the female opening, but even then the LEDs only flash. I can't find the sweet spot where the LEDs stay on. Probably for the best, as I suspect I'm doing something wrong and that's causing the LEDs to behave this way. I can't figure out what, though, because I successfully turned on a Raspberry Pi using the same pigtail and power adapter, and didn't experience any of the problems that I have with these LEDs.

The pigtail I'm using strangely has the red and black swapped - that is, the red wire is negative and the black is positive.

These are the lights I'm using:
http://www.amazon.com/gp/product/B00B4UKG2W/ref=oh_details_o09_s00_i00?ie=UTF8&psc=1

They're individually addressable RGB, and the DI wire is not connected. I'm just connecting without the DI. Surely the DI doesn't need to be connected? There are five wires to connect: Two positive, two negative, and the fifth the DI. Presumably this is so one can connect without using the DI at all.

I'm very much a beginner at circuitry, but I really want to get this project working. I'm excitedly learning. I've searched, but haven't been able to find anyone else experiencing this problem, much less a solution.


texts:
An N-bit carry lookahead adder, where N is a multiple of 4, employs ICs 74181 (4 bit ALU) and 74182 ( 4 bit carry lookahead generator).

The minimum addition time using the best architecture for this adder is

1) proportional to N

2) proportional to log N

3) a constant

4) None of the above

====================================================

Answer is 2)

I am confused between 2) and 3).
 Not sure, but taking a guess. In a lookahead carry adder, the number of bits is not an issue (if we take an ideal situation by not considering the propagation delay of the logic gates). Unlike the normal adder, where each of the higher full adder needs to wait for the result of the lower adder and thus would take O(N) time for computing a N-bit addition, lookahead carry adder calculates the sum of all the bits at once (if we neglect the propagation delay of the lot more gates needed to implement look ahead carry generator) and thus I would say the minimum addition time would be a constant.


texts: How to determine bandwidth available at USB ports

texts:
I am considering a mini-itx single board computer for a project that makes heavy use of USB. I want to ensure that certain USB devices have enough bandwidth. For example I have a data acquisition board that uses a bulk input but those transfer frames do not have guaranteed bandwidth. By placing this on a dedicated controller then I believe 80-90% of the high-speed bandwidth will be available as 10-20% is allocated for control endpoints. In other words, and if I understand this correctly, there will be enough free frames to support the bandwidth needed by my board.

But I'm looking at block diagrams that show physical USB ports going back to the Intel processor and it's not clear to me how these are tied together internally. There is the ICH that appears to contain EHCIs that will support high-speed. How can I know if my data acquisition board is sharing the bus controller with other devices?


texts: Trouble understanding Verilog decoder logical left shift

texts:
This code is from asic-world:

module decoder_using_assign (
 binary_in   , //  4 bit binary input
 decoder_out , //  16-bit out
 enable        //  Enable for the decoder
);
  input [3:0] binary_in  ;
  input  enable ;
  output [15:0] decoder_out ;

  wire [15:0] decoder_out ;

  assign decoder_out = (enable) ? (1 << binary_in) : 16'b0 ;

endmodule

I can't seem to wrap my head around (1 < < binary_in). binary_in is 4 bits wide, how is the logical left shift producing an output 16 bits wide when enable is true?


texts:
I came accross the folowing question, where the accepted answer contains a formula showing the relation between bit-rate and data-rate for a delta sigma ADC. My question is, why that relation is valid. There is nothing stated regarding clock rate of the ADC in its datasheet. Why is this relation posted in the accepted answer valid? Does that count for all delta sigma ADCs?
Maybe this is a stupid question with an obvious answer, but would really appreciate an answer to make this more clear. A link to an app-note/datasheet containing this formula/explanation is appreciated as well.

Formula:

data_rate = f_clk / 2^(bit)

Question

Datahseet of ADC


texts: CANopen SYNC object and synchronous window length

texts: In CANopen specification there is an object called Communication Cycle Priod [1006h]. This is the time interval between two consecutive SYNC objects. There is also another object called Synchronous Window Length [1007h]. I cannot get these two parameters real-world interpretations. This synchronous window length is for a synchronization interval between nodes? After receving a SYNC object, all nodes are used it as an trigger for update their output values and accept new input from bus? For example, if my control loop wait updated values in each 1 mS, then what should I set my 1006h and 1007h values? Is there a rule for 1006h and 1007h values?


texts: Amplifying signal strength of a u.fl antenna

texts:
I have a mini pcie wlan card which uses a mini pcie to pcie x1 adapter card. The adapter card has 2 threaded male connectors which look exactly like conventional rg6 but smaller. Those lead directly to the wlan chip with standard u.fl connectors.
I have an antenna from a netgear router attached to the larger connector.
My question is: what can I do to increase that antennas signal strength?
Alternatively, I have an antenna from a laptop that has a foam spacer and appears to be very intentionally and carefully designed. What can I use to replace or amplify that?


texts:
I need to "duplicate" a given current: it has to feed two IC's. The context is an OTA (operational transconductance amp) whose gain is controlled by a bias current. Concretely, I am considering the CA3280 (or the modern LM13700). Since I have at my disposal two amplifiers in the same IC, I would like to connect them in parallel in order to halve the noise.

The problem is how to send the same (given) bias current to both amps: if the bias is "incoming" I cannot use a current mirror, since it would behave as a "sink", thus producing a current coming out from the amps. I need a current source instead - kind of "inverting" the current mirror.

Hope the problem is understandable. Any idea?


texts: Constant current power supply and 2 LED - series or parellel?

texts:
I have a very limited understanding of how current works in parallel or in series.  I am trying to connect a pair of LEDs to a constant current power supply (1200ma) in which the power supply automatically adjusts the output voltage according to the current draw.

Which (if any) will result in a brighter output?  Series or parallel configuration?

The LEDs are Cree XP-G2 1A R5 that can handle 1.5A of current.  Of course I don't want to max this out because it will create too much heat.  I have tried both setups and measured the amp draw maxed at 1200ma but I can't tell which is brighter.  Does it even matter in my case?

Any help would be greatly appreciated.


texts: Generate measurable reverse torque with DC motor as a dynamometer

texts: I am trying to use a KBRG 225D regen drive as a dynamometer to apply reverse torque in order to stress my test engine? I am wondering if anyone has experience or guidance? I am not sure how to measure the reverse torque generated by the drive?


texts: Where to find MSP430 & CC430 code examples?

texts: I was googling for some MSP430 code examples (e.g. for SPI) for some time, unable to find anything. Do you happen to know, where to find some examples? They do have some on TI webpage, but very general, and not many of them.


texts: How are high-speed serial signals processed?

texts:
High-speed serial links such as Gb ethernet, PCIe, Firewire, etc support bit rates that suggest signalling frequencies far in excess of typical clocking speed of typical chips. I am wondering how these signals are processed.

Example: SATA supports up to 6 Gb/s on a single pair of differential signalling lines. This suggests a signalling frequency of the order of 6 GHz, right?

While modern processors clock in the vicinity of this, I do not think SATA chips themselves are clocked so high. - Can somebody enlighten me on the design tricks used for processing such high-frequency signals? Are several bits processed within each clock cycle? If so, how?


texts:
I've just started circuit analysis. All the examples, I've seen so far involve using using KCL/KVL or nodal analysis. They all consist of setting up a system of equations and solving them which gives you all the voltages and currents.

But systems of equations can have no solutions, infinite solutions or one solution. It's impossible for the system of equations to have no solutions in this case, because current must be flowing through the circuit.

But how do we know that the system of equations (assuming you have n equations for n variables) won't have infinite solutions?


texts:
Suppose I have a small (4cmm x 4cmm) 4-layer PCB with standard stack-up of Signal-Vcc-Gnd-Signal. The board is dominated by two QFP-100 (FPGA and uC) on both on top and bottom side of the board with various traces running underneath each of the chips.

Both FPGA and uC are powered from the same 3.3V rail. Now I'm whether I should

simply connect each power pin and associated capacitor to the Vcc plane by vias OR
form a Vcc island on top and bottom side under the ICs and connect this island to the Vcc plane at one point, possibly via a chip bead. The decoupling caps would then connect to the Vcc island and have the other leg connected to the Gnd layer by vias. OR
form a Gnd island on top and bottom side under the ICs and connect it on a single place to the Gnd plane. Each Gnd pin would then connect to the Gnd island and each Power pin would be tied to the Vcc layer by vias. Same for the decoupling caps.

In either of the two last cases the island would inevitably contain some cuts and holes.

There is no exceptionally sensitive analogue circuitry on the board except for the ADC inside the uC. Still I would like to have the supply/ground as quite as reasonably possible.


texts: How to come out of the transcript window of Modelsim which is stuck?

texts:
I am running a Modelsim script and the transcript window gets stuck. I have tried the following to go to the next line in the transcript window without any success.

Simulate > End simulation
Simulate > Break

Any other ways to come out of this/ find out the reason for it?

The TCL script used is as follows.

variable dir .

# Stop simulation if already running one
quit -Sim

# Open project
project open $dir/sim_mesi_isc

vlib work
#vmap work work

# Compile the required Verilog files (For the initial run)
vlog -work work -vopt -nocovercells $dir/mesi_isc_basic_fifo.v
vlog -work work -vopt -nocovercells $dir/mesi_isc_basic_fifo_buggy.v
vlog -work work -vopt -nocovercells $dir/mesi_isc_breq_fifos.v
vlog -work work -vopt -nocovercells $dir/mesi_isc_broad.v
vlog -work work -vopt -nocovercells $dir/mesi_isc_tb_cpu.v
vlog -work work -vopt -nocovercells $dir/mesi_isc.v
vlog -work work -vopt -nocovercells $dir/mesi_isc_breq_fifos_cntl.v
vlog -work work -vopt -nocovercells $dir/mesi_isc_broad_cntl.v
vlog -work work -vopt -nocovercells $dir/mesi_isc_define.v
vlog -work work -vopt -nocovercells $dir/mesi_isc_tb_define.v
#vlog -work work -vopt -nocovercells $dir/mesi_isc_tb_custom.v
vlog -work work -vopt -nocovercells $dir/mesi_isc_tb.v

#-------------------------------------------------------------------------------
# Generate VCD files after simulation
#-------------------------------------------------------------------------------
vsim -novopt work.mesi_isc_tb

# Load the waveform file in the Wave window of Modelsim.
do wave.do

# Run and break just before the instructions generated from the test vectors are executed
run -all

#--------------------------------------------------------------------------------
# Add the signals to the list window
#--------------------------------------------------------------------------------
add list  \
mesi_isc_tb/mesi_isc/clk \
mesi_isc_tb/mesi_isc/rst \
mesi_isc_tb/mesi_isc/mesi_isc_breq_fifos/fifo_0/rd_i \
mesi_isc_tb/mesi_isc/mesi_isc_breq_fifos/fifo_0/ptr_rd \
mesi_isc_tb/mesi_isc/mesi_isc_breq_fifos/fifo_0/ptr_wr \
mesi_isc_tb/mesi_isc/mesi_isc_breq_fifos/fifo_0/fifo_depth \
mesi_isc_tb/mesi_isc/mesi_isc_breq_fifos/fifo_0/status_full \
mesi_isc_tb/mesi_isc/mesi_isc_breq_fifos/fifo_0/wr_i \
mesi_isc_tb/mesi_isc/mesi_isc_broad/broad_fifo/data_o \
mesi_isc_tb/mesi_isc/cbus_cmd0_o \
mesi_isc_tb/mesi_isc/cbus_addr_o

# Write the list to a file
write list -window .main_pane.list.interior.cs.body list_mesi_isc.lst

Update (2-Sep-2019)
I have been using a second screen connected through HDMI cable (in second screen only mode). The above mentioned issue arises when I switch back to my laptop screen (only) and disabling the second screen. When I switch back to the second screen option, the Modelsim window which was stuck resumes the execution and finishes as expected. Waiting for somebody to throw some light on this behavior.


texts: Uninterruptible power supply - How it manages to provide electricity to electronic devices before it shutting down?

texts: I believe there is a lag in time (I think the latency for the switch over can take some milliseconds) when a switch over to the battery backup happens. I understand the electric appliances like motor, bulbs may not have much impact if the latency is less. However when it comes to electronic devices, example a computer processor which has its clocks works for every nanosecond, how will those maintain the working in the UPS latency?


texts:
simulate this circuit – Schematic created using CircuitLab

Can the Direction of current in an inductor in a closed circuit change instantaneously.
The circuit is in steady state for t<0.
The solution says I(0-) = -0.4A and I(0+) = 0.4A
So, is the solution wrong or the direction really changed.


texts: Valve heater voltage without separate windings

texts:
I want to build a simple single-ended valve amplifier from an old TV.

I am facing a problem, that I don't know how to produce the 13V, 300mA supply for the heater.(PCL86)
I am using the mains transformer directly from the old TV. But while other amplifiers I see have a transformer with separate windings for a heater, this one only has one primary and one secondary winding.

The TV obviously had solved this problem somehow, so how could I solve this most easily?


texts:
I am playing around with the FPGA editor and looking at a Spartan3E. When I click the different lines the console displays what I guess is a name for each individual line:

What exactly do these mean? I know there are different line types and I'm guessing the different names (double, OMUX...etc) siginfy the different types but what do the numbers tell me? I can't find anywhere this is documented.

node = OMUX(10200,31745)
node = DOUBLE(9504,39237)
node = DOUBLE(12960,39237)
node = OMUX(10200,31745)
node = OMUX(6744,31745)
node = DOUBLE(9552,39201)
node = HUNIHEX(9408,38995)
node = HUNIHEX(5952,38967)
node = HUNIHEX(13088,39119)
node = HUNIHEX(2496,38883)
node = HUNIHEX(13112,39077)
node = HUNIHEX(2496,38799)
node = HLONG(-1208,39003)
node = HLONG(-1192,38979)


texts:
I have three AA 1,5V@2950mAh Alkaline batteries in series with a discharge rate of 3% per year.
My circuit has a 3V3 LDO that will work until 3V6 is reached, so each battery will need to have at least 1V2.

In order to calculate the battery life for my circuit and check if it is able to last for 2 complete years I have the following conditions:

The circuit consumes 380mA during 4 seconds 8 times a day.
The circuit will then remain at low power mode with a consumption of 1uA.

I have done the following estimation:

Operating duty cycle (per day) = 32 /86400 = 0.00037037
Average current during operation = 380mA x 0.00037037 = 140.740 uA
I consider Low power mode as 1uA 100% of the time
Total average current = 141.740 uA
Operating time = 2950 mAh / 0.141740 mA = 20812.64 h = 867.193 days
Adding discharge rate I'd have --> 867.193 - 867.193 * 0.06 (2 years @ 3%) = 815.162 days

So it seems the batteries will be able to last for the twop required years.

Are these previous calculations correct? For sure I´m missing something...


texts: Is the formula for inductive reactance the same when considering rectified AC?

texts:
Is the formula X\$_L\$ = 2\$\pi\$fL still true for rectified (but unfiltered) AC (in which case the frequency f, and therefore the reactance, would be doubled in the case of full-wave rectification)?

I forgot to add a parasitic resistor in series with the inductor. The inductor is not ideal as depicted in the image above.


texts:
I'm trying to figure out what type of plug is this.
According to this site it is most similar to type A, but the blades are spaced only 10mm apart and they have the same size. According to here one should be bigger and they should be spaced 12.7mm apart, which is not the case.

But then, what is it?


texts:
I am trying to figure out how much water is passing through a funnel, and to do so, I had the idea that I could set it up so the water will spin the shaft of a motor, which I have been led to believe will create a voltage that I can measure.

If this is even possible, which type of motor would I need, and how what sort of range will the voltage be in?


texts: use of power dissipation in transistor and using higher current rated transistor

texts:
I am using using a PNP transistor in one of my application to switch on and off the boost convertor.
My requirement for collector current is 500mA.
My question is does it matter if I use 500mA/600mA/800mA/1A/1.5A collector current rated transistor ?
Because using one with slightly higher value will give some tolerance so I am thinking to go for 1A.
My concern is mainly voltage drop across transistor(emitter to collector).I am operating transistor at 3.3 volt so I can not afford high voltage drop across transistor. So does it even matter ?
NOTE: assume enough base current is provided according to gain.
Another thing I don't understand in datasheet while choosing transistor is power dissipation.
How one can filter that parameter for application.
For example if I have 2 transistor of same rating with only difference is one have power dissipation of 250mW and other 500mW.
Any explanations or pointers will do. I am just trying to understand different parameters of transistor to choose most optimum one.
Thank you.

simulate this circuit – Schematic created using CircuitLab


texts: How much energy is stored in the capacitor after 18us?

texts:
I have the following problem:

Consider the circuit below

The graph shows the current through a \$50 uF\$ capacitor. The initial voltage across the capacitor is \$V_0=10V\$.
How much energy is stored in the capacitor at 18 us?

Okay, so I tried to solve this problem with LT-spice, but I run into a problem.
I simulated the current with Lt-spice and set the initial voltage across the capacitor to 10V.
I then ran a transient analysis on the circuit and got the following two graphs.

The first graph shows me the current and voltage through and over the capacitor. The second graph shows me the power of the capacitor.
From the first graph, I see that the voltage across the capacitor is 10.546V at 18us. From there, I thought to use this formula, to calculate the energy of the capacitor:
\$E=\frac{1}{2} \cdot C \cdot v^2=\frac{1}{2} \cdot 50uF \cdot (10.546V)^2= 2.78 mJ\$
However, from the second graph (the power graph) I see that the integral of the power function is \$E=0.280 mJ\$.
So which answer is right? I hope someone can help me figure this out.


texts:
I want to generate mandelbrot fractal using fpga.
I create module which must calculate mandelbrot iterate for each pixel.
code works great on simulation,but i get unexpected value when debuging on real hardware when n>0

Here is a calculator module,i increment n if done_calc==0 and change x and y if done_calc==1.

This initial numeric values works Flawlessly on python;

Here is ila log,when n=0 test1,test2,xn,yn values is correct but when n=1 values not match expected values.
On simulation everything works as expected

`timescale 1ns / 1ps

module mandelbrot(

    input clk,
    input wire[10:0] x,
    input wire[10:0] y,
    input wire[10:0] n,
    output wire done_calc

    );

parameter  MAX_ITER = 180 , HEIGHT=768 , WIDTH = 1024;
reg  signed [63:0] xb=-64'd33554432 , xl=16777216 , yb=-64'd16777216 , yl=16777216 , xs=49152 , ys=43690;
reg signed  [63:0] x0=64'b0, y0=64'b0, xn=64'b0, yn=64'b0,tmp_yn=64'b0;
reg done_calc_reg=0;
reg[63:0] test1=0;
reg[63:0] test2=0;
reg test=0;
wire [10:0] d_x=x;
wire [10:0] d_y=y;
wire [10:0] d_n=n;
wire [63:0] d_x0=x0;
wire [63:0] d_y0=y0;
wire [63:0] d_test1=test1;
wire [63:0] d_test2=test2;
wire [63:0] d_xn=xn;
wire [63:0] d_yn=yn;
wire d_test=test;

 function   [63:0] mm (input signed [63:0] a ,input signed [63:0] b);
begin
  mm = (a*b)>>>24;
end
endfunction

function   [63:0] f (input signed [63:0] a );
begin
  f=a*(1<<<24);
end
endfunction

function   [63:0] i (input signed [63:0] a);
begin
  i=(a+(1<<<23))>>>24;
end
endfunction

always @(n or x or y) begin

    if(n==0)begin
     done_calc_reg=0;
     x0=xb+x*xs;
     y0=yb+y*ys;
     xn = x0;
     yn = y0;

     end

    test1=mm(yn,yn);
    test2=mm(xn,xn);
    test=(test1+test2)<f(4);
    if(test1+test2<f(4) && n<MAX_ITER)begin

         tmp_yn=2*mm(yn,xn) +y0;
         xn=mm(xn,xn)- mm(yn,yn) + x0;
         yn = tmp_yn;
         done_calc_reg=0;

     end
    else

      done_calc_reg=1;

 end

ila_0 deb(.clk(clk),.probe0(d_y0),.probe1(d_x0),.probe2(d_n),
.probe3(d_x),.probe4(d_y),.probe5(d_test1),.probe6(d_test2),
.probe7(d_xn),.probe8(d_yn),.probe9(d_test)
);

 assign done_calc=done_calc_reg;

endmodule


texts: Reducing voltage in power supply with diodes

texts:
Hello there i am building a variable power supply as a summer project. I have ordered some parts, and want to begin building it. I start with the transformer power supply:

I've ordered a transformer (230 V - 36 V) and i expected it to give a output voltage of 36 V peak (silly me), and then found out the output will be in RMS, i. e. an peak outout of 50,92 V. I can work with this, but the capacitors i've orderes is only rated at 50 V, so this will give me some smoking problems i guess. The rectifying diodes will give a voltage drop of minimum 0,6 V, which is not quite enough to go under 50 V.

Is it possible to just use two diodes extra? As seen in the simulation:

The diodes added is of course D5 and D6. Their only purpose is to lower the voltage, to under 50 V. This will theoretical be enough.

But will i need to go lower in voltage, as the overhead on the WV of the capacitor is too small?

And is the "extra diodes" way even a viable way of doing this?


texts: Need help designing a current controlled source in PSpice?

texts:
The image below shows an electrical network with 8 elements, a current controlled source, a bunch of resistors, one current source and a voltage source.
Although I haven't labeled them, there are 5 interesting junctions in the network.
Four at the middle of each side of the square and one at the center.
I've been having trouble designing the current controlled source in PSpice.
Does any one have an idea on how I would go about designing the current controlled source in PSpice?!

  **UPDATE

This is what I'm trying to simulate in PSpice, but I want to make sure it's right through hand calculations.

I'm not sure whether this is right. Can someone confirm?

If you replace the 3A current with a 2A current and the 15 ohm current with a 10 ohm current this is what I get for I1 and I2 when I run the simulation:
I1 = 2.0A
I2 = -6.8A
Can someone confirm this?


texts:
I would like to hear some comments on my first 2-layer board.
Specificaly if I should go with two grounds (one for 12 V, one for 5 V) or just one big ground plane.
Another thing is the layout of the capacitors for the 7805 [U1] (12 V to 5 V).
Should I add some more vias to the return path after the FET [Q1-3]? And/or generally add more vias? The idea of adding more vias is to have enough more contact between ground and Vcc.
Front Side

Back Side (ground plane)

Back side ("2" grounds)

Schematics

Basicly this uses a Tiny13A to turn some fans on and off.


texts:
I have the front end of a photodiode detector. What is the point of the 3rd Op Amp? The output from U2C gets divided in half from R14 and R18, then it just gets double by U2D again.

Is there a reason for this other than just using the rest of the 4 stage op amp circuitry? Are the two acting as a stabilizer for the signal?

When would you want to use Cascading (I believe this is the correct terminology) Op amps?

Background info: I'm looking to possibly replicate it with as another detector but am asking questions about the circuit since it was designed way before my time. I'm wondering if my detector should use one Op Amp or use cascading op amps.


texts: I need the explanation on a DMM instruction manual

texts:
It's HIOKI DT4211 digital MM
In Electrical Characteristics section it states:

Rated power voltage: 1.5 v DC x2, use LR6 AA Alkaline battery 2x 1.5v

But then...
in Accuracy Table section, it states:

Accuracy warranty period:      1 year

Regulated Power Supply range:    2.4 V +- 0.15 v or more until Bat lights up

What'd 'Regulated power supply range' specification mean?

Does it mean the DMM can also use 2x 1.2 v AA battery supply as long as it doesn't complain warning Bat low ?

And what is 'Accuracy warranty period 1 year' supposed to mean?

Does DMM maker think it'll be likely degraded quickly to lower quality after a year so he may not give a damn anything to be responsible?

Anyone who would sincerely help me, of course I'm so much thankful


texts: FPGA Atlys Spartan 6 output predefined image or string through HDMI

texts:
I need help with displaying a short text on a hdmi display connected to the board (2 characters), I have already experimented with xapp495 but I still don't know how to do this.

I understand that it may be needed to save the characters as images in the memory or maybe in an attached ROM.

Could you instruct me how to achieve this, or maybe provide a premade source code that has this specific function?

Thanks in advance!


texts: How can I edit my quartus project to work with relative paths?

texts:
I have a project in quartus with many files containing full-path-links to other files.
I found a way to make it work on my machine with a different location, but that is the cheat way.
I would like to change all the paths to be relative, so that other engineers won't have the same problems.
What should I do?
If I change all my "C:\projects\filt..." to relative "..." will I ever get newly generated files with full paths when I continue working with it ?
And what should I do when i create a new quartus project (with nios hw and sw) to make full-path-links never appear anywhere?

For example the filt.elf file:
 ...filt_NIOSII_SW.c D:\filt\software\filt_NIOSII ...
For example the filt_NIOSII_SW.o file:
 ... alt_alarm_list D:\filt\software\filt_NIOSII_BSP alt_llist_insert...
For example the libhal_bsp.a file:
 ... filt_NIOSII_SW.c D:\filt\software\filt_NIOSII signed char ...


texts: Non-inverting Lowpass Filter with Capacitor in Feedback

texts:
I am looking for a circuit that I expected to find everywhere but I don't. The "active" lowpass filter I often see in the web uses an RC filter with a buffer in series.

simulate this circuit – Schematic created using CircuitLab

The alternativ version I found quite often is, in my opinion, not a true one pole lowpass but a lowpass shelving filter. The capacitor in the feedback is paired with a parallel resistor.

simulate this circuit

Now my question is, why don't I see the second variant without the additional parallel resistor in the feedback path more often? Are there any major disadvantages to the RC - buffer implementation?


texts: NPN transistor for switching electromagnetic relay

texts:
I have to switch on a relay based on a signal, and for this purpose, I am using an NPN transistor (BC-639G) in open-collector configuration, where the switching signal is applied to the base using a suitable current limiting resistor, and the relay coil sits between the collector and the power supply.
Switching signal frequency is random and is very very low.

simulate this circuit – Schematic created using CircuitLab

We are observing that this transistor is failing very often. The full load current of the relay coil is only 30mA, and the transistor is rated for 1A. We have not been able to pin-point the cause for this apparent failure. An earlier design used MJE802G (NPN Darlington 4A) device, and this kind of failure was not observed then.

Need expert comments on this to get to the bottom of this. All pointers are welcome.

Update from comment to an answer on Sept 8, 2017:

  I forgot to put the diode in the schematic, but there is a 1N4007 diode in that place to allow the relay coil to freewheel when the transistor switches off. The failure (C-E short, or C-E open) is inspite of the above diode.


texts:
I need to bridge two pairs of pins together on an Xbox 360 AV adapter, and the most common method is to solder them together (to fix a rebooting issue). I don't mind doing this, but I'd like to create a video tutorial for other 360 owners that have the same problem, and not every 360 owner knows how to solder.

With that said, is there a way to bridge a connection without soldering (in a way that's easy enough for everyday folks).

Here's a picture of the AV Adapter (minus the casing so you can see the wires and pins)

Image courtesy of this guide I found for what pins to solder.


texts: Who makes polyimide stiffeners for FPCs?

texts:
I have an FPC that is 0.075mm thick and I am trying to find a FPC zero insertion force connector to fit it. The smallest FPC connector I can find on Mouser or Digikey accepts FPC thickness down to 0.18mm (here).

As a result I think I will need to use an FPC stiffener to thicken the FPC to fit the connector. Page 15 of the aforementioned connector's datasheet outline the construction of the FPC including the stiffener and from which I have picked up key terms to search. I have had little experience using stiffeners however upon searching key terms (FPC stiffener, polyimide stiffener, zif connector stiffener etc) have not been able to find manufacturers of them, only materials such as polyimide film on Alibaba.

My question is if I am designing a cable and require a stiffener, who normally manufactures these stiffeners: the connector company (Molex/Hirose/Harwin), the FPC manufacturer (contractor) or the end FPC purchaser and product designer (myself) prior to use in the end product?


texts:
I am a newbie in Eagle and I'm making a RF layout using GCPW.
In the figure below, the pad and the track are in contact. However, the connection still unrouted, why?

It became routed only when the track overpass the pad, but I cannot allow this condition.

Thanks in advance.


texts: Interfacing microcontroller with 1.8V logic

texts:
I am in the process of selecting a microcontroller to interface (~30 signal lines) to an FPGA that operates at 1.8V voltage levels.

I have found NXP's Cortex M0's to operate down to 1.8V which is great, but the bulk of Cortex M3 chips out there have a minimum operating voltage of 2V.

Should I restrict myself to the M0's? Or should I just use level translators? Are there Cortex M3 implementations that have an I/O voltage of 1.8v?

Note that I do have other voltage levels available on the board, but i just need the micro's I/O voltage to be compatible with 1.8V logic.


texts: Unknown component place on a switching converter PCB

texts:
I bought a 220V to 12V converter and behind the PCB there's place for a component named U3:

It's not a AMS1117 series because their output pin is the middle pin, and not a 78XX series because on the PCB input and output are not matching.

What U3 is for?


texts:
It seems this question is a bit tricky. I tried to solve it but since the sources do not have any values, so I cannot prove this is a non inverting summing amp.
I wrote the node equations, as follows.


texts: How to stop annoying informative gray area to appear in Altium?

texts: It is might come across off topic. But, it is somehow related to PCB design. So, I'd like to ask how prevent this information giving gray area to appear and disappear every time I move the mouse on something. It distracts me and covers the areas that I want to investigate more carefully.


texts: the transconductance of cascade MOSFET IF channel length modulation is NOT ZERO

texts: What would the derivation of the cascode MOSFET transconductance in small signal analysis IF THE CHANNEL LENGTH MODULATION IS NOT ZERO, as most examples for the cascode mosfet transconductance say in Behzad Razavi's book is when channel length modulation is set to zero, hence there is no "ro" on the cascode MOSFET and the input MOSFET


texts: What probems may arise with a 200V rated relay conducting 1000V 1A?

texts:
I am going to use a DPST relay to pass a 1A 1000V DC signal of an ESD Human Body Model simulator circuit through it.

I have see many relays, they share a property like maximum DC switching for example 200V (and it is generally higher for AC like 400).

Now my question is, If I get a relay that has 200V DC switching property what kind of problems I will get?

Or can I do like this: I will control the signal and also the relay using a micro controller, so I can be sure that I first turn ON the relay then start the signal. I believe the relay should just work like a shorting wire and cause no problems? Same case also for switching the relay OFF that is I first stop the signal and then turn OFF the relay. Is this approach going to work?


texts: How would I implement an onboard ISP for multiple ARM Cortex M0+ MCUs?

texts:
I've written a lot of firmwares for embedded dev boards like Arduinos and Teensys, but am still  new to PCB design. Right now I'm attempting to bring a multi-MCU design into limited production, and I'm looking for a way to flash the processors on the board through a single interface, and hopefully with a single file. I'm hoping to make this as easy as possible for the user to update in the future.
Last time I did this for a large-scale factory environment, it made sense to just drop a whole Teensy onto my board. But this time I need to miniaturize down to a square board less than an inch and a half on a side. I still like the idea of dropping an open-source board design onto my PCB, and would like to clone three board schematics onto my single board, along with various items for power, an IMU, LED drivers, etc. I can understand if that sounds like a noob thing to do, but from my perspective, it gets the thing up and running faster with very little downside, and my code already relies on open-source, so it makes sense to me.
So I would like to drop in three instances of a dev board design, most likely the Seeeduino Xiao, or possibly the Adafruit Feather. Both use the same Cortex M0 processor, but the feather breaks out more pins. Both of the boards are programmable through USB, as well as something called UF2. But they also both break out SWD pads, which are for serial flashing and debugging. I'm wondering if I can use these to program remotely from an ISP on the board.
I've learned several ways these boards can be programmed, but so far I've been unable to decipher the best way to do it in my end product. Here's some reading I've done so far:
https://learn.adafruit.com/adafruit-feather-m0-basic-proto/adapting-sketches-to-m0
https://learn.sparkfun.com/tutorials/arm-programming/all
https://www.sigmdel.ca/michel/ha/xiao/seeeduino_xiao_01_en.html
https://www.sigmdel.ca/michel/ha/xiao/seeeduino_xiao_sercom_en.html#warning
https://wiki.seeedstudio.com/Arduino-DAPLink/
https://learn.adafruit.com/programming-an-m0-using-an-arduino
https://www.pemicro.com/downloads/flash_algorithm/ARM_SPI_external_flash_alg_download.cfm
Any advice you might offer would go a long way. At this point I'm assuming by cloning in these board layouts, I'll be able to compile for that board as I normally do (VisualMicro for Visual Studio), and somehow produce a binary file that would flash all three processors. But I'm totally green when it comes to this kind of thing. So things that are obvious to you guys, I likely am totally unaware of.
Thanks for your time!


texts: ESP32 driving Solenoid requiring 2A/24V DC with IRF520?

texts:
I am trying to design a circuit, which will drive my home valves which is on 24V and by specifications must supply 2A ( but this is quite suspicious, and probably it is requiring much lower current, but sill I wish to make it fulfill this requirement ).
I found a few circuits, but when I doublechecked them - most of them ends with an issue.
So, just as a precaution I wish to ask peoples which done this eventually for guide.

How to drive IRF520 with ESP32 3.3V output correctly ?


texts:
For a project I'd like three PICs (two slaves PIC18F4620, one master PIC18F46K22) to communicate over the I2C bus. Later on, more slaves may be added (like EEPROM, SRAM, ...). I'm writing the code for these PICs in C using the C18 compiler. I've looked around on the internet a lot, but couldn't find libraries to handle the (M)SSP peripheral. I've read the datasheet of both PICs on the (M)SSP peripheral in I2C mode but couldn't find out how to interface the bus.

So I need master and slave libraries.

What do you recommend? Do you have such a library somewhere? Is it built-in in the compiler and if yes, where? Is there a good tutorial somewhere on the net?


texts: Good quick reference parameters for discrete components

texts:
I'm labeling and binning my discrete components.  I'm putting each component type in an envelope with its part number and a few key values.  The plan is that, when I need (say) an N-channel MOSFET that's at least 100 MHz, I can check the envelopes in my MOSFET bin and find one that meets the bill.  I also want key characteristics that I may need when designing common circuits, such as the voltage drop of a diode.

The first few lines on each envelope say something like "Transistor, NPN, small-signal / 2N2222A", and at the bottom I have a sketch of the package with E, B, C labeled.  I'm using small envelopes, and only have 5-6 lines for key characteristics.  For diodes, for instance, I have IF, VF, VRRM, PD, and TRR, although I'm not confident that I've got the best set of values there.

Obviously, if a characteristic is unusual or in the "Features" section of a datasheet (such as a particularly high frequency), I'd include it on the envelope for that part.  But otherwise, I'd like to come up with a good set of characteristics to include for each common component type (e.g., all my BJTs include hFE).

I'd like to come up with a good set of characteristics for diodes, BJTs, MOSFETs, op-amps, and other common components, like I laid out for diodes above.  Any opinions on the most important characteristics to put on the envelopes?


texts: why is the voltage zero across the resistors in this circuit?

texts: simulate this circuit – Schematic created using CircuitLab


texts:
I have a question regarding the voltage specification of the TSH82 OpAmp: Datasheet.

In the data-sheet, maximum ratings I find (Table 1):

Vcc Supply Voltage  14V
Vid Differential Input Voltage ±2V
Vi  Input Voltage ±6V

The common mode input voltage range on the other hand is defined as (Table 2): Vcc- to (Vcc+ -1.1). Note that the data-sheet of this part does not use the usual Vcc and Vdd nomenclature but uses Vcc- and Vcc+ instead.

Question:

If the common mode input voltage goes basically from negative supply to 1V below positive supply, what does the "Vi Input Voltage ±6V" from table 1 refer to? It seem to contradict with the common mode input voltage range because it's range is much lower when the device is powered from lets say 9V.

Reason I'm asking is, that I want to use one unit as a comparator (save space, reduce cost). Since it's not ideal to use an OpAmp as a comparator I really have to pay attention to these details.


texts: If I am using the 'beta' (dc gain) value of a transistor to calculate Ic and Ib in a bjt transistor , does that mean I have already assumed that the transistor is in active region?


texts: Does SEC/DIV know on oscilloscope always adjust capture sample rate (or acquisition speed)?

texts: I have an oscilloscope called Tektronix TDS 224. I find it confusing how the horizontal SEC/DIV knob actually changes the resolution of acquisition. Is this how most scopes are?


texts: Voltage offset and fluctuating output in transimpedance amplifier circuit

texts:
I am working on an electronics project to design a transimpedance amplifier circuit. It involves an op amp chip in a PCB with a current input, 3.4 KOhm resistor, and the voltage output that I am measuring.

Why might it be that for nearly 20 of the same OPA227P chips, the voltage offset is about .5V? I checked the chip's datasheet and its offset should be 75 uV maximum. The chip is in the PCB, no input, powered by a 12 V source, grounded to a metal table... how can this problem be fixed?
And, why is the voltage output that I see not stabilizing on a single value? It fluctuates up and down a lot and is generally a lot lower than expected, the gain is lesser on a magnitude of 10-100. Is there something that I can do so that the voltage output stabilizes? Why might the gain be so lower than expected, is there something I could do to remedy that?

Thank you for any help!

More details:

Here is a diagram of the circuit:

The chip is being powered by a 12 V source (when I measure its voltage with a multimeter, it's actually 11.84 V). The current input is from a programmable current source. I've been using .1-1.0 mA in .1 mA increments. I've also been checking the current input with a multimeter. The op amp chip model is OPA227P, and it's in a socket which is soldered onto the PCB. I measured the resistance of the resistor, it is 3.398 KOhm. The other leads of the current source are grounded and the ground port of the PCB is grounded, all to a metal table in the lab but on different spots (there is no measurable voltage difference between those points).


texts: How To Detect If Two Voltages Are The Same And Trigger An Output If They Are

texts:
Basically, I'm struggling to design a circuit with the following requirements:

Requirement 1: Output is high (say 5v) when the two input voltages are different. [If it makes it any easier the output voltage only needs to be high when, say, input 2 is lower than input 1. That is the output is 5v when voltage 2 is less than voltage 1.]

Requirement 2: As soon as the 2 voltages are equal, the output shoots down to 0v (grounded/low). [Or as soon as voltage 2 is in a few microvolts or nanovolts below voltage 1, ie they are very close, then the output immediately shoots to 0v.

Requirement 3: Once the 2 input voltages are no longer equal the output goes back to high (5v). [As soon as voltage 2 is out of the microvolts or nanovolts range below voltage 1, ie voltage 2 is below voltage 1 (voltage 2 will never be higher than voltage 1, it can only match it) then the output immediately shoots up to 5v.

I've tried using a basic subtractor using opamps, but you see the 2 input voltages are sinusoidal. This means the difference between the 2 inputs can be very small, and the output as a result, slowly decreases to 0 rather than immediately 'trigger/shoot down' to 0. It would be useful if the output was a steady 5v and as soon as say the 2 inputs are within a very small range of each other (say a few microvolts or nanovolts) then the output immediately drops to 0. Once the two input voltages are no longer in that range, then the output shoots back to 5v.

Thank you!
Any help is appreciated.


texts: Read current from two ground-connected supplies

texts:
I have two separate variable DC PSUs (15V@2A, 20V@4A) from which I read the voltage and current through a microcontroller. For the current reading I use a low-side shunt.

The ground output of the supplies are connected toghether with the uC ground, then each one fed through the shunt resistor to the loads.

I would be interested in a way to somehow connect the load ground leads together and still maintain the separate current reading. I'm assuming that current will flow only through the used power supply so theoretically it should be possible.


texts: ZVS Driver - Why does so much current need to flow through the diodes?

texts:
Here is a diagram for a simple ZVS driver:

So as the voltage one side of the LC circuit goes up, it pulls down the gate of the MOSFET on the opposite side, through the diode (D3 and D4). The current going into the diodes is limited by the 470 ohm resistors, if I'm correct.

However, I don't see why the resistor values are so low. Having such a low value means needing a diode and resistor with higher wattage ratings, and more heating, etc.

Since the pull down resistors are 10kohm, R3 and R4 just have to be lower resistance than the pull down resistors (R1 and R2), say 1kohm, or something like that...are there any problems that would arise from doing that?

EDIT: Ignore the input voltage on the diagram - I will know the voltage beforehand

Also, unrelated, but how do I know the best value for the caps?


texts:
I saw this VGA demo for a 640x480 monitor

http://pumpingstationone.org/2013/04/nerp-fpgaok/

and I would like to run it on my monitor using a Basys-3 FPGA.
The GPIO demo code for the Basys-3 board works on my monitor, so I know it is possible to display it given 1280x1024 resolution, so I decided to modify their code accordingly. The full code is in a zip file which can be downloaded from that link (NERP_demo.zip).

I used values I found from this link
and so the part of their code I modified from the vga640x480.v file looks like this:

// video structure constants

parameter hpixels = 1280;// horizontal pixels per line

parameter vlines = 768; // vertical lines per frame

parameter hpulse = 128;     // hsync pulse length

parameter vpulse = 7;   // vsync pulse length

parameter hbp = 216;    // end of horizontal back porch

parameter hfp = 88;     // beginning of horizontal front porch

parameter vbp = 29;         // end of vertical back porch

parameter vfp = 3;  // beginning of vertical front porch

// active horizontal video is therefore: 784 - 144 = 640

// active vertical video is therefore: 511 - 31 = 480

However, I still can't get their demo to run on my monitor. Before I changed their values, when I tried running the code, my monitor was telling me to switch to 1440x900. After I changed the values, I don't get that suggestion anymore, but the screen is still black. I don't know what to do.


texts: Current in Transformer Primary (Forward Converter)

texts:
I currently read an application note from ON Semiconductor concerning forward converters. Latter explains why one needs core reset in case of the "single-switch" forward converter.

Consider the following slide, especially the graph of the current in the primary side, i.e. the magnetizing inductance.

I know that a transformer can be modeled by an "ideal" transformer with infinite inductance (here X1) plus Lmag on the primary side and some leakage inductance (which was obviously omitted here because the explanations target the primary side effects only?)

I also know that the magnetizing inductance is a model for the energy needed to "allow" a magnetic field to change inside the transformer core (so I suppose it is somehow related to core losses.)

To my question: When Q1 turns off, where is the REAL WORLD path for the current? Since Q1 is open and ILmag cannot be "stopped" immediately, there must be a way for the current to circulate until the magnetizing energy is dissipated.
All the slides I found draw this "circulating path" though Lmag and (for the given picture) the primary side of X1.

I don´t understand that, neither conceptually nor for real-world scenarios.

Conceptually, why would the current circulate through the primary of X1 and Lmag? (is there even a current through an infinite inductor? and if there is, should not the voltage across the inductor then be zero, so no voltage anywhere across the inductor and therefore a short?)

For real-world considerations: Since the primary of X1 is just a model for the ideal transformer and no real thing, where does the current circulate that flows in Lmag?


texts: I'm not experienced with DSP. The few texts I've cracked open pre-suppose a level of sophistication i'm not at yet. Is there some stepping stone to start dabbling or is DSP all or nothing?


texts: How to regulate voltage into two variable outputs?

texts:
I'm thinking of building a control voltage generator for a synthesizer. Basically I want to control two pitch control voltages with variable resistors, something like this:

R1 needs to control only the output of CV1, and R2 only the output voltage of CV2. But with my understanding, if one were to modify the value of R1 this would change the output voltage of CV2, which is obviously undesirable for a pitch control.

Two voltage regulators in parallel seems like overkill for such a simple problem, and I'm not even sure it would work. Is there some other way to make it so that R2 will not affect the output of CV1 and that R1 will not affect the output of CV2?

also, apologies in advance if this is a duplicate question. It seems like a simple, common problem but I've searched quite thoroughly.


texts: Stepper Motor works at 5v, driver explodes at 12v?

texts:
After i salvaged some stepper motors and read alot about them i finally decided to try them out... But before i did i asked:
Simple stepper motor circuit safe?

in the above question you can find datasheet and circuits of the motor i used.

I opted for the Mitsumi M55SP-1N from hp printer
and the ULN2803A as driver.

After finding the 2 coils and the center tap i tested with 5v using a battery.

As expected everything worked fine.

It was time to solder things together. I used 2 channels per chip To be sure to have enough sink and not overheat the chip. I tested everything again with 5v. Perfect.

Now, as the motor is a 12-24v motor i atached a 12v 1.25Ampere powersupply.

The green Light on the powersupply started to dimm as soon as there was current flowing trough the ULN2803. Anyway the motor just made some random noises and unexpected steps.

Even if the whole setup should consume less than 1.25Ampere i decided to power it with a bigger one. So i took a 12v 5A powersupply and turned the motor on.

After 3 erratically stutters the uln2803 exploded.

The only thing i could think of was wrong is the missing Diode between the powersupply and the common of the ULN2803 wich should be optional as the that chip already has alot of protection diodes.

Please help me to understand what i did wrong. I'm not an electrical engineer, i'm just trying to learn new things and i don't want to give up now. i have more uln2803...

here is the finished circuit http://imgur.com/a/tCdwk (2 images) and shematic

simulate this circuit – Schematic created using CircuitLab


texts: Cascade Control System - Multi-Stage Temperature Control

texts:
I am new to the forum, hopefully you can help :)

I am a software engineer trying to put together a control system. My controls background is not strong, I have really only tuned PID loops via trial and error - understand the concepts but not the theory or practice.

Here it goes...

I have a temperature control system where constantly moving fluid must be heated via heat exchanger to keep a process chamber at constant temperature. Find a simple diagram of the system here: https://www.dropbox.com/s/5f784pexc1z1w08/Tank%20Chamber%20Temp%20control.png?dl=0

Fluid enters from reservoir at ambient temperature (20-26 deg C).
Hose passes through a peristaltic pump that can operate from 50 to 400 mL per min.
The fluid passes through a heat-exchanger in a heated water bath ("Tank").  The tank is about 750 mL and heat-exchanger is about 1.5m in length. The Tank temperature is controlled by a "Heater Output" signal (0-100% PWM) and has a "Tank Temp" sensor
Out of the Tank heat exchanger, the fluid flows through a section of about 20" of hose, outfitted with an "Infrared Temp" sensor to the "Chamber".
The Chamber is about 400 mL in volume, insulated, and where the experiment is taking place. "Chamber Temp" is the ultimate process variable we are trying to control. It should stay at the "Chamber SP", typically 37 deg C +/- 0.5 deg C, with a critical limit of never going above 37.5 deg C. This set point of 37 can be set anywhere between 30 and 37 deg C.

The "experiments" are expected to have a warm-up time, then can run anywhere from 30-90 minutes, keeping Chamber Temp at the Chamber SP.

Right now we have a PID-based control process running. There are two stages:

(1) Warm Up - Here, we use the Tank Temp as the process variable and warm up the tank to somewhere near the Chamber SP. Through experimentation, we have found the dead time (time to see any change in PV, when MV is changed) is about 150 seconds. And the time constant is much greater - it takes about 800 seconds to stabilize from 34 deg C to 37 deg C. This stage is relatively straight forward and we can tune a PID loop to keep the tank at a certain SP when pump is off and everything is static...

(2) Chamber Control - Here, is where things get more complicated. When the pump starts running, fluid passes through the water bath, through the Infrared Temp sensor, then in to the Chamber. The goal is to control the Chamber Temp by controlling the Heater Output of the Tank. It has been a challenge to tune the PID loop, as the pump may be at different rates, the tank may be warmer or cooler than the Chamber, and it takes soo long for a change in Heater Output to affect the Chamber Temp. due to the mass of the Tank, time lag, and mass of the Chamber.

My question is around the Chamber Control stage described above:
- Is PID appropriate here? It is VERY slow, long delays, and hard to tune.

Is it best to have one loop using Chamber Temp to manipulate Heater Output? Or to have two "stacked" or cascaded loops where one can observe the Chamber Temp to set a desired Infrared Temp, then a second to use the Heater Output to control Infrared Temp? Or even three?
PV-MV

Chamber Temp - Infrared Temp
Infrared Temp - Tank Temp
Tank Temp - Heater Output

Is there a way I can characterize the system more quantifiably to help tune the loop or give you guys more information?

Thanks,
Peter


texts: Manually Change from one Power Source to Another

texts:
Apologies, this has surely been answered but not in language I can understand.
I have a cooling fan, connected to a Niles AC3 (a voltage triggered power strip), which is connected to the 12V turn on lead of an audio receiver. When the receiver is powered on, the power strip is active and powers the fan, a DC fan that runs off of a mobile phone type transformer to USB.
It is in a closet with my computer. Usually that stays cool enough, but using for extended periods creates a lot of heat.
Is there a switch I can buy so that if my receiver is off, I can manually switch on the fan?
I've been looking at some solutions, usually for generators or nautical applications.
Saw the thread below on using a three way switch, but do not know if that would work for this.

My ideal solution would just be a switch I can flip when the receiver is off but I want the fan on.

Any suggestions or links very welcome.
https://www.garagejournal.com/forum/archive/index.php/t-248408.html


texts: Communication via I2C sensor via CAN bus

texts:
I am wondering if it is possible to implement the following idea:
I want to build a network of sensors, all of them communicate via I2C protocol and all those sensors will send their parameters via CAN bus to the main microcontroller that will handle all those data to execute some determined command.
I know it is necessary to have one microcontroller for each sensor to implement the communıcation between the sensor and the CAN Bus.

My question is, is it possible for the microcontroller (with CAN peripheral) receive those data from I2C protocol "transform" them into CAN protocol and send them to the master microcontroller located in another point from CAN BUS?

Thank you


texts:
I think I understand how a Oscillator works (VCO). One uses an Oscillator when one wants for example a square wave oscillating between sy, \$0\$ volts and \$5\$ volts.

My question is: Is there such a thing as a resistance oscillator?

That is, how can one create a circuit where it is the resistance that changes as a function of a time? Can this be done as a square wave? Sine Wave?