texts: Any tips on designing an audio preamplifier for low frequencies?

texts:
I'm currently trying to design an audio preamp with the purpose of amplifying very faint audio signals (possibly in the microvolt range) from 20-200Hz. I've tried both transistors and op amps for amplification but for some reason I never see any sort of signal when I go below ~80Hz. I'm using an electret condenser microphone CMA 4544PF-W (www.cui.com/product/resource/cma-4544pf-w.pdf).

In order to generate these frequencies, I'm using frequency generator app on my phone (which is accurate according to the oscilloscope I'm using), but I'm not sure if some of the lower frequencies (20-30Hz) are being played. I can feel the 50-60Hz and above playing because they vibrate my phone when I go in that range.

The circuits I've build are:

and

(Note: C2 of the op amp was replaced with a 0.1uF because I didn't have a 4.7uF with me and I'm using a BC547B (www.farnell.com/datasheets/410427.pdf) transistor instead of the 2N3904 (www.sparkfun.com/datasheets/Components/2N3904.pdf) for the second picture)

I've spent a fair amount of time researching transistor preamps and the types of biases and I ended up choosing between the collector feedback and the voltage divider. I'm having difficulty getting a large gain with the voltage divider due to the emitter resistor value, and I can't bypass it with a parallel capacitor because that will essentially turn it into a high pass which is the very opposite of what I want.

For the collector feedback, I've been able to amplify the signal well, but as I said, only above 80Hz.

How can I amplify the signals below 80Hz? I have some ideas what the problem might be but I have no idea which it actually is:

My phone is incapable of generating sounds below 50Hz
My condenser microphone is not sensitive enough to pick up frequencies below 50Hz
Lower frequencies require more amplification to be visible

Another note: for collector feedback circuits, how exactly do you calculate the gain of the circuit? I believe it has to do with the base resistor but I can't find a formula anywhere.


texts: Book Suggestion - How to calculate the power dissipation of a BJT

texts:
I did a exam that asked for "power dissipation" of a given BJT circuit. The question was simple but my professor considered my calculation of dissipated power wrong, because my answer was \$P = V_{CE} \cdot I_C + V_{BE} \cdot I_B\$.

But he told me that the correct answer is \$P = V_{CE} \cdot I_C\$.

Can someone indicate a textbook or a scientific article confirming my answer so I could talk to him again ?

I found some links on the internet confirming my answer, but he would not consider a website...


texts: Diagnose brushless three phase motor controller

texts:
Can I test somehow if my brushless motor controller works? After some time of playing with it and with the three phases motor from old HHD, this pair just stops working.

LED is on, but nothing more works.
The motor seems to be not damaged. After attaching DC to two (from four) input wires, it starts to shudder a little bit, and it can't be moved (spun) by a hand (it's locked). The values of resistance between the inputs also the same as when I was measuring it before the failure.

After attaching the motor to the controller, nothing happens. It can be spun by hand. Can I find out if the controller is damaged with the multimeter?

This is the type on my controller:

https://alexnld.com/product/5v-12v-dc-brushless-motor-driver-board-controller-for-hard-drive-motor-3-4-wire/

(updated link)


texts: How to properly wire a 4.5V LED strip with 12V motors

texts:
I'm modding a Nerf gun (Rapidstrike to be exact), and I put a 3S Lipo in there with 1000 mAh. The circuit right now is a rev switch, trigger switch, switch behind the pusher, battery, pusher motors, and flywheel motors. The switches are 21 amp switches and the motors are all 12V motors. I want to put an LED strip in the blaster, however the LED strip is assumed to be rated at 4.5V (I ripped it out of a Harbor Freight light and it took 3 1.5V batteries. There were no resistors inside the light.), and I'm unsure how I can include the strip in the circuit safely. I assumed I could put a resistor in there, however I didn't really know how to calculate what kind of resistance I needed. I'm familiar with Ohm's law, however I have no idea how I'd calculate the current to be able to get the resistance. In addition, I assumed I could just throw a resistor in by the LED strip, but I'm not sure if this is the proper way to do it. I have an image of how I assumed it might work, but please correct me if I'm wrong:

If this is correct, how much resistance would I need? If not, how can I wire it properly? I have very little electrical engineering experience, so I figured I'd ask the experts here for guidance.


texts:
I have an application where I'll be sending audio data to a codec. The CS4234 fits my needs very well, although with other I2S codecs, there have only been one data in line for the communication.  The CS4234 has two input data lines and two data out lines (SDINx and SDOUTx).

Since I only have one processor that will be communicating with the CS4234 codec, do I need to terminate or do something with the other input/output lines I won't be using?  I don't think I need to do too much since the 2nd SDOUT line is also an address bit set pin (which brings up the question how would the chip know its using two SDOUT lines if the address bit isn't set...odd)

"Bonus" points if you can explain what they mean by low latency data


texts: What's the reason for power-down sequencing in a SOC? Can you damage it in some way?

texts:
Power-on sequencing I understand. But why do power-off sequencing? I could understand if you had to do something before power died, or maybe you just wanted to shutdown I/O before core so that no crazy pins are toggled while you're on your way down.

Is there a situation where you could risk damaging the part?  Only thing I think of there is maybe ESD diodes.


texts: I am trying to get SPI working on an MCU. The SCK on the MCU is labelled \$\overline{SCK}\$ which means it active low but my device has no overline on the SCK. Can I use the same clock. If not what can I do?


texts: Dipole antenna VS. coil for RF transmission or recieving

texts:
Correct me if I am wrong, but all RF light waves are created via a changing electric and magnetic field. But when looking at all kinds of radios and RF circuits, this light wave is always made with a simple wire antenna. Why are coils not used instead? Wouldn't a coil of the same length create a stronger magnetic field thereby creating a more efficient 'antenna' that produces RF waves?

I know that there has to be a reason why coils are not used, but I cannot find an explanation. It makes more sense to me to have a coil creating a fluxuating electric/ magnetic field rather than a piece of wire.

Thanks in advance!


texts: I can't length match the traces from my microcontroller to its 16MHz crystal. The trace length difference is quite different, as you can see. Would this be a problem?


texts: Architecture of speaker (drivers) to get an acceptable level with small dimensions

texts:
I'm trying for a couple of days now how to get a good volume out of a small speaker.
My reference is e.g. an iPhone internal speaker which has a good loudness (up to 100dB) in the higher and middle frequencies. Is this just a result of the speaker housing or are there more important aspects to focus to get this sound clarity?

Actually I tried a lot of speakers which are bigger than iPhone internal ones but I can't get an acceptable loudness. Only if I work with single frequencies (like a piezo beep) —  but if there are more complex sounds, e.g. a bell, it's very quiet.

Compared the same "more complex" sound on my iPhone speaker it sounds fine.

So the question is: What aspects are important to get a good bright sound with a small speaker in a small housing (e.g. a Raspberry Pi box)?


texts: Rising edge of a pulse or one complete pulse needed for 1 step in Stepper motor?

texts:
I'm trying to make a step counter using Hall effect sensor implanted near the rotor of a common hybrid-synchronous(1.8° in full step) stepper motor, and I'm confused as I'm not able to figure out when common stepper drivers executes a step, whether at the rising edge of pulse sent by controller or falling.

Edit: I'm referring to the output of the stepper controller to the stepper driver(Step Signal) not of stepper driver to stepper motor.

Help will be appreciated.


texts:
When out of town I'm thinking of using an LDR with a 555-relay driver to periodically toggle the lights in a few rooms at night, and a thermistor near an incandescent bulb to kill the circuit when the bulb is sufficiently warm/hot.

This will involve placing the LDR, and the thermistor at some distance from the board which will be near the switchboard; a length of 8-12 feet.

In the case of HF/VHF circuits a pair of leads this long are not advised. Are there similar restrictions applicable to a simple driver circuit too?

How long a lead may be used to connect a component to a circuit?


texts: As a student group project, we are going to use Li-Ion batteries to test our charging and balancing circuit. These batteries at risk of explosion. How should we avoid that danger? Is there any intelligent battery cells to use? or any other suggestion?


texts: What effects might an electrolyte leak have on nearby electronic components?

texts: If an electrolytic capacitor were to leak electrolyte on nearby circuit boards, what might the effects be? Short-circuits? Altered impedances? Are there caustic effects? Or is it possible to generalize aluminum capacitor electrolytes to this degree?


texts: Mega 2560 and LCD 1602 got error messages when upload

texts:
I am talking about Mega 2560 and LCD 1602

When I tried uploading the program, it just gave me these error messages:

avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer

the arduino isn't lighting up or anything either.


texts: Wrong voltage measured with a DAQ in presence of a RC filter

texts:
I'm using a DAQ from National Instruments. Testing my LabView software I noticed that when I plug a 1.5V DC battery in the analog input channels if I connect an RC filter (R=56 kΩ, C=10 uF) to the batter then my DAQ instead of measuring the expected voltage it measures a lower value, 1.22V, as if there was a load of about 300 kΩ. The declared imput impedance is instead 144 kΩ and this happens only if I measure the voltage in differential mode, if I measure it in RSE (Reference Single Ended) that doesn't happen (i.e. I read 1.5V). Can you explain why?

Furthermore: in the lower schematic, what is the purpose of the +2.5 Vref and of the resistors?


texts:
We are working on a pipelined processor written in VHDL, and we have some issues with timing, synchronization and registers on the simulator (the code does not need to be synthesizable, because we are going to run it only on the simulator).

Imagine we have two processor stages, A and B, with a pipeline register in the middle:

Processor stage A is combinatorial and does not depend on clock
The pipeline register R, is a register, and therefor, changes its state at clock rising edge.
Processor stage B is a complex stage and has its own state machine, and, therefor, changes its state and does operations inside a VHDL process, governed by clock rising edge.

The configuration would be as follows

   _______   ___   _______
   |     |   | |   |     |
---|  A  |---|R|---|  B  |---
   |_____|   |_|   |_____|

With this configuration, there is a timing problem:

t = 0: A gets data, and does its operations
t = 1: At rising edge, R updates its data with the output of A.
t = 2: At rising edge, B gets the values of R, and updates its status and gives an output.

We would like to have B changing its state and generating an output at t = 1, but we also need the register in the middle to make the pipeline work.

A solution would be to update the R register on falling edge. But then, we are assuming that all processor stages run in half a clock cycle, and the other half is a bit useless.

How is this problem usually solved in pipelines?


texts: Interfacing Matlab with a NI real time target (cRIO 9073)

texts:
I currently have a control system implemented in Matlab that controls a vehicle. The tracking is performed using an overhead camera, and commands are sent to the vehicle via xbee. I have now added a sensor to the vehicle that interfaces with a National Instruments real-time target (cRIO 9073) and sends measurements to the host computer's virtual instrument over ethernet. I would like to access those measurements from Matlab (running in that same computer) so that I can include them in my control algorithm.

How should I go about doing this? Moving the entire control loop to LabView isn't really an option at this point. Do you have any experience with such a set-up?


texts:
I know how to write accurate delay routines in assembly to run on a PIC microcontroller. The problem I have is creating delays of a arbitrary length.

What I want to do is accept some data which tells me how long to delay for, and then the PIC will write a port high or low for that period of time. So if I have a 1uS delay and a 1mS delay, I can break up the data and find out how many times I need to call each function. for example:

0.123567 Seconds means I would call Delay_1uS 567 times, then Delay_1mS 123 times.

The problem is that all these calls create delays of their own which means that there will be an error is the total delay time.

To combat this I can calculate the incurred delay of the calls and subtract this from the the total delay time. However now the total number of calls is less and thus the incurred delay is less... This seems like some sort or recursive optimization problem that I do not know how to solve. Is there a "best practice" way of doing this?


texts: Running DSPIC33FJ64GP802 at high temperature

texts:
Has anyone run this part to its rated temperature of 150 Celsius?  We are able to run up to and beyond this temperature, but if power is cycled the part will not start reliably.  We have tried running with and without the PLL, with the internal oscillator, a crystal, a high temperature oscillator, and an oscillator outside of the oven, with brownout on and off, and with various circuits on the reset pin and at various frequencies. The part is only using two output compare modules, one UART, one ICD interface, and powering a couple of LED's. All of the other pins are floating. We have monitored the voltage on VCAP and it stays around 2.5 volts. The part recovers after cool down.  We have also tried letting the part soak unpowered for long periods to make sure it is not self heating.

If there are any tricks to make it start or if you have had a similar experience, I would be grateful to hear.

Thanks.


texts: Downscale a 0 - 5volt supply to a millivolt range

texts:
I am currently at keen novice stage in my understanding of electronics so i hope my question makes sense!

I have a project I am working on that requires the simulation of a sensor. The sensor is measured in millivolts and i have to replicate it's values fairly accurately. I have a 10bit DAC with a 5v supply that i can use to control the voltage but this is not accurate enough on its own as the required range is quite specific. I'm looking to achieve a range of +220 to +365 mvolts. I could use a vref value of 365mv into the DAC but i would only be utilising about 40% of the DAC's range.

My question: Is there a way of further scaling the output voltages to utilize the full 10bit range of the DAC, and if so what would be the best and easiest method?

Thanks for the time.

Mylo


texts: Building a BCD to 7-segment using 3x8 decoder

texts:
So.. I know how to build a BCD to 7-segment using 3x8 decoder but the question provides 4-digit binaries and asks to only input 3 of those.. my question is that won't two different digits be regarded as one.. If that's confusing, here's the question:

  Consider a BCD digit \$X_3X_2X_1X_0\$ with \$X_3\$ being the MSB. Design a BCD to
  7-segment converter using two 3x8 decoders and minimum number of
  gates, such that \$X_3\$, \$X_2\$ and \$X_0\$ are applied at the inputs of the
  decoders. The converter should be compatible with a common cathode
  display.

So.. in this case 0 is 0000 and 2 is 0010 but if we don't input \$X_1\$, we're only giving out 0000 in both cases.. so how would the decoder know which is 0 and which is 2? Do I use \$X_1\$ as enabler? And we're not supposed to use anything other than 3x8 decoder, a 7 segment and minimal gates.
I'm really confused here. Please help!


texts: PT100 temperature sensor: meaning of "measuring current" specification

texts:
I'm measuring temperature using a PT100 temperature sensor on a Wheatstone bridge.
As I'm working on a battery powered application, I'm choosing the resistors in the bridge so that only a small current pass through it (to save power).
In my understanding, as long as I can measure the resistance of the RTD it should work, independent of the current flowing through it. Although, I know that the smaller the current, the smaller the signal I'll have to measure. However I'm puzzled by a section of the datasheet referring to a "measuring current". What does this parameter means? Is there a lower limit of the current flowing through the RTD for it to work properly?
This is the relevant section of the datasheet of the PT100 I'm working with:

The full datasheet can be found here.
Thanks


texts: Induction machine: Question regarding field weakening region limited by breakdown torque

texts:
I have a question regarding the entry point to the field weakening region limited by the breakdown torque of an induction machine marked red in the following picture:

Under nominal conditions, this point may be located at (ws1_N, T1_N) where T1_N is the torque at ws1_N. Let's assume instead of P_N one demands only 0.8 * P_N from the motor. What is the formula to calculate the new entry point to this region ws1_new and T1_new based on the nominal values of ws1_N and T1_N?


texts: which is better? 5V or 3.3V as the supply voltage

texts:
I am about to design a new microcontroller based project. I checked all components (few) and all can operate at 3.3V or 5V. the microcontroller itself can also operate at 3.3V or 5V (pic micro at only 4MHz oscillator).

Well, the question is, what are the advantages/disadvantages of using 5V as the positive supply over using 3.3V

All I could think about is that power consumption will be lower when the supply voltage is 3.3V

Thanks a lot


texts: Current limiting resistor on peltier element

texts:
I have a 12v/22A DC switching power supply and 9 peltier elements rated for 12v/6A.

I would like to limit current to 2A per peltier element.

I don't know how to calculate the impedance (in ohms) that I need.

Intuitively, by ohm's law, every peltier element's impedance is 12v÷6A=2Ω and the impedance I'm aiming for is 12v÷2A=6Ω. Does this mean I need a 4Ω current limiting resistor in series with the peltier element?

Also, what power (watt) rating does my resistor need?


texts: Differential Amplifier doesn't output the expected voltage?

texts:
I have the following differential amplifier in simulation. According to the theory I know, the output should be 0.2V - the difference between the two inputs at 2V and 1.8V. What am I misunderstanding here?

EDIT:....
Added some more probes:


texts: Why do some switching regulator ICs have single VCC pin but multiple PGND pins?

texts:
This is a follow up question to Reason of multiple GND and VCC on an IC

I found a switching regulator IC (buck) that has multiple PGND pins and one analog ground (AGND). It has only one VCC pin.
(Sorry, Could not attach a snapshot/datasheet as I could't find a public domain document for the same). Anyways it is a simple buck , with all usual pins + 3 PGND pins.

I understand the need for separate ground for analog circuitry and power circuitry .My doubts are:

What could be the reason for multiple power ground pins?
If this method of multiple ground pins are for higher current capability ( or any other advantage), why is it not followed by many SMPS IC manufacturers? I see many switching regulator ICs ( with similar rating) having single PGND pin.
Also shouldn't the VCC pins have the same count as GND pins?


texts: How to implement AC analysis in a resonant circuit in LTspice

texts:
In previous LTspice simulations, I've set the AC amplitude of the voltage source to 1 and then carried on with the .ac spice directive. How do I setup the AC analysis for this circuit?

Do I set the AC amplitude to 1 for each voltage source or only my 100V DC source? Does setting the AC amplitude to 1 for a particular source set that source as the input voltage?


texts: How can we calculate optimal dimensions for volume of transformer?

texts: I have to design a transformer. First of all, I did calculations for the core that is available in the market. Now I want to optimize the volume of the transformer core and wanted to design my custom transformer?


texts: How can I use a 5200 mAh Li-Po battery to power multiple things?

texts:
I'm building an autonomous car and have a 7.4V 5200mAh 2S Li-Po battery that needs to power the following components:

Brushless DC Motor (Through ESC)
Raspberry Pi 4
Servo motor
Arduino Uno
Another smaller servo

I have bought these DC-DC converters for the purpose of dropping down the voltage to the respective components. Since the Li-Po battery has only one EC-5 power supply cable, I'm not able to figure out what I can use to connect all these electronics in parallel to the battery (Or is it even safe to do so!). I new to electronics and would appreciate any help I can get. Thank you!


texts: Why does my DIY "solar panel circuit" show battery voltage and not solar panel voltage?

texts:
I've got two solar panels set up in series as shown on the below schema. I connect positive on panel A to positive on battery, and negative on panel B to negative on battery. The two panels produce 9V each, and 18V in series on a good sunny day. That's what my multimeter says.

If I disconnect cabling between panels and battery, my multimeter shows that the panels produce about 15V (a bit cloudy today). However, when I connect the cables between panels and battery, my multimeter shows about 12.2V. I believe this is the battery voltage.

Why is it that when I connect my multimeter at point A and B it shows 12.2V (when solar panels are connected to the battery). As you can see on the schema, there's a diode in front of point B. Shouldn't that diode make sure that current from the battery not flows back to the panels?

If this is how it is supposed to work, how do I check the voltage my panels produce when the panels are connected to the battery.


texts: NMOS: what exactly forms the inversion layer

texts:
I have a a question on forming of the inversion layer in NMOS. More specifically, please refer to the following figures

The negative ions (in-mobile) are due to the the accumulation of the positive charges at the gate metal plate that pushes the holes (mobile carriers) downward.  This is the first figure. However, in the second figure, there is electrons moving on top of the negative ions. And I question is, is the mobile electrons forming the inversion layers (connect the source to the drain), or does the in-mobile negative ions forming the inversion layer?

This confuses me if you look at another diagram (below). If you look at the place underneath the oxide, marked as "Induced n-type channel", it is hard for me to tell which is which


texts:
So I am making an audio switch, and I need a switch that takes 3 dual inputs and outputs one of them, or vice versa, taking one dual input and outputting it to one of three outputs. It needs to be an on-on-on switch. I think it is different from a DPDT, a 3PDT and a 4PDT. I have know idea what to search for! Here are the details below, a '•' means a contact and the lines just mean it connects one to another:

OFF

1• •
2• •
3• •
4• •

POSITION 1-   Connections: 1a&2a, 1b& 2b

1• •
 | |
2• •
3• •
4• •

POSITION 2-   Connections: 3a&2a, 3b& 2b

1• •
2• •
 | |
3• •
4• •

POSITION 3-   Connections: 4a&2a, 4b& 2b

1• •
2• •
  \ \
3•|•|
  / /
4• •

If someone could give me a name of a switch that would be great!


texts: MOSFET power dissipation calculations - Diodes Inc. datasheets

texts:
Looking at Diodes Inc. datasheets, I am having trouble following their power dissipation limit calculations for their MOSFETS.

E.g. for DMG4496SSS
http://www.diodes.com/_files/datasheets/ds32048.pdf

They specify on page 1

I_D(max) = 8A @ V_GS=4.5V (with a R_DS(on) = 0.029 ohm)

But then the datasheet also gives on page 2:

Power dissipation P_D = 1.42 W
Junction temperature T_J = 150°C
Thermal resistance R_\theta = 88.49 K/W

And on page 3:

R_DS(on) @ V_GS=4.5V, I_DS=8A approximately 0.024 ohm

To me this looks like one big mess:

P = 0.029 ohm * (8A)^2 = 1.86 W which is significantly larger than the permissible power dissipation of P_D = 1.42 W from page 2
even with the R_DS(on)=0.024 ohm value from page 3, P = 1.54 with is still larger than the permissible power dissipation
the permissible power dissipation figures are at least self-consistent: P_D =(T_J-T_A) / R_\theta = (150°C-25K) / 88.49 K/W = 1.41 W
However, the R_DS(on) vs V_GS and I_D vs V_DS graphs appear to be inconsistent: Looking at the case of V_GS = 3.5 V: In fig 1, the tangent at the point (V_DS=0.5V, I_D=10A) is about 6A/0.5V which seems to imply a R_DS(on) = 0.5V/6A = 0.083 ohm. Looking at fig. 3 however, the R_DS(on) is more like 0.048 ohm at 10A.

How to use Diodes Inc datasheets?

So given the datasheet, how would one calculate I_DS(max) provided some V_GS and some V_DS? E.g. V_GS = 6V and V_DS = 12V.


texts: Data modulation over Bluetooth headset profile?

texts:
What kind of data modulation schemes might be suitable for sending data to/from a Bluetooth audio headset?  e.g. What kind of data modulation would likely survive the audio compression schemes and bandwidths used by the Bluetooth headset or hands-free audio profile?  Assume that any other (non-audio) Bluetooth profile is absolutely not available.  Assume that DSP capable microcontrollers are available on both ends outside the Bluetooth channel for audio data modulation/demodulation.

Are there cheap Bluetooth headphone/headset experimenter kits available for testing this idea?


texts:
When do we have to use a TP circuit breaker, and when do we have to use a TPN breaker, and why?
I am specifically referring to 415 VAC 3 phase, 230 VAC in single phase, 50 HZ.


texts: How does this spectrometer sensor output its data and how to process it?

texts:
I want to this sensor and an Arduino board to obtain the wave length data and log or plot something like the following:

Here it shows how to connect to the Arduino board. But no code and no explanation.
But from the datasheet I don't understand how it functions. How does this sensor output the wave length data and how can I obtain the wavelength data similar to the plot shown above using a microcontroller board such as Arduino board?


texts: How does Sifteo and Scrabble Flash tiles handle proximity and ID?

texts:
Sifteo and Scrabble Flash

These tiles will sense and ID tiles that are adjacent to each other.

On the Sifteo site it mentions proprietary near field sensing technology. How does it work? Does each side of the tile have some sort of reader and communication device?

UPDATE
I think that there's a proximity switch on each side and when another tile is brought close to it; the switch activates a directional radio for each tile so that tiles can transmit information. This is all just a guess.

How can you design a radio that transmits only at short distances? You don't want the signal to go further because it might interfere with other tiles communicating.


texts:
I'm trying to read a number of analogue ports on a PIC16F690. I can read 2 but I can't get it to read the 3rd. ie below, AN1, AN2 work, but AN3 doesn't. Am I doing something wrong with TRISA, ANSEL, ADCON1 or ADCON0? Thanks

TRISA   = 0b00010111;         // all port A:0,1,2,4 as inputs
ANSEL   = 0b11111111;         // RA0->RA1 are Analog
ADCON1  = 0b01010000;         // select ADC clock (500 Khz)

ADCON0  = 0b10000101;         //peripheral 1 - PORT A:1 - AN1
__delay_us(250);
unsigned short nRet;
ADCON0 |= 0x02;             // Start conversion
while(ADCON0 & 0x02)        // wait for conversion
 {
 }
 nRet = ADRESH;
 nRet <<=8;
 nRet += ADRESL;

ADCON0  = 0b10001001;         //peripheral 2 - PORT A:2 - AN2
__delay_us(250);
unsigned short nRet;
ADCON0 |= 0x02;             // Start conversion
while(ADCON0 & 0x02)        // wait for conversion
{
 }
 nRet = ADRESH;
 nRet <<=8;
 nRet += ADRESL;

    ADCON0  = 0b10001101;         //peripheral 2 - PORT A:4 - AN3
    __delay_us(250);
    unsigned short nRet;
    ADCON0 |= 0x02;             // Start conversion

    while(ADCON0 & 0x02)        // wait for conversion
    {
    }
    nRet = ADRESH;
    nRet <<=8;
    nRet += ADRESL;

   return (nRet & 0x3FF);


texts:
I am looking for low power power supply without transformer.

Input \$110V-230V\$,

Output plan to use 7805 regulator IC.

Application demand \$5V/3.V, 150-250mA.  \$

In input side I should be able to give 110VAC /230V AC
I know transformer based design give good isolation.
Whether bridge rectifier with Zener diode serve purpose?
Kindly suggest me some power supply design

Information about some design


texts: Running 20 WS2812 LED strips (80 pixels each) from a single Arduino and 24V Power Supply with Buck Converters

texts:
I am building a matrix with 20 WS2812 LED Strips. Each strip is 80 pixels for a total of 1600 pixels. I want to drive them all from a single Arduino Mega board. To handle the power needs, I have a 24V 15A power source that I then run to 5 buck converters that each power 4 strips.

The data wire runs through all 20 strips but every 4 strips the power is connected to a separate buck converter.

Currently it works but there is flickering across the strips. I'm not sure how to diagnose or fix the problem.

Is this the right way to try to power a large array of pixels?

Thanks for the help, I'm a computer science guy trying to pick up the EE side and am still relatively inexperienced so any help or guidance is very appreciated.

****** UPDATE*****
I've made some progress here. I am now using 4 digital outputs on the arduino. Each output connects to a set of 4 LED strips which is also connected to a buck converter. That eliminates the flickering. So I think it had to do with the data line running through the LED's but the power coming in from the arduino and them not being in sync (at least that's my current hypothesis).


texts: Altium: Error in importing changes to PCB

texts:
When I first imported everything from schematic to a new PCB project, it all went smoothly. But note that I have duplicate schematic sheets that have the exact same circuit, net, I/Os, etc. I tried deleting the duplicate, but it deleted the original along with it. In any case, the first time I imported the schematic to the PCB, I managed not to move the duplicate and it went well.

However now when I go back to the schematic and make some changes then import it back to the PCB project, an error comes up.

First, this pop-up comes up & I clicked OK

Now because I have duplicate schematic sheets, this came up and I selected the actual one.

Once that was done, the engineering changes order panel came up and I validated the changes. These errors came up:

I dont want to continue with these errors because they will appear on the PCB project.


texts: Improving dV/dt turn-on immunity of a mosfet without increasing turn-off time

texts:
I'm designing a solid state battery disconnect switch and I want to improve the mosfets' turn-on immunity (high dV/dt on Vds) without impacting the turn-off time. I don't really care about the turn-on time, it can be 100x slower than turn-off time, no problem.

I came up with this solution:

C1 obviously improves the immunity and D1 should leave the turn-off time the same. Did I miss something? is there a better way to do this?

NB: mosfet's datasheet is available here and the driver's datasheet is here. I'll use a +/- 12 V symmetric supply and the driver will drive 10 mosfets in parallel.


texts: Bidirectional Converter Switching problem on Mosfet

texts:
I want to ask. I designed a bidirectional converter with synchronous buck converter as the circuit configuration.
The problem is, the switching mosfet. When i applied lower voltage at the input (10V), i can produce 5V output. The signal also came smooth. But when i increase the input voltage, i can see clearly that it started to oscillate (when i'm trying to increase it to 14V, i can produce 7V output but the oscillate came out).
Here're the signal at both of the mosfet. Yellow signal represents high side of the mosfet and blue signal represents low side of the mosfet.
Oh yeah, and i used P75NF75 as the mosfet. And TLP250 as the gate driver with 10V VCC.

Schematic from related question

Thank you so much !


texts: Is it okay to connect Supercapacitors as input to Step-up voltage regulator?

texts:
I want to use the maximum energy of the supercapacitor for 3.3 powered circuits. Thus, I thought of using step-up voltage regulator like this
Can I do this? What are the other suggestions?


texts:
I'm looking for a way to partially power an applicance (a fridge freezer for argument's sake) using solar/renewable energy.

I don't expect the couple of hundred watts of solar power to be sufficient to fully power what I have in mind, but wondered if such a device as the following exists or is easily made so as to reduce energy bills but not have to interfere with the incoming mains power supply or investing in a bank of batteries.

What I'm imagining is a solar inverter which plugs into the mains (230V AC) and also takes 12V DC as input (from the panels), and only uses mains power to "top up" any requirements not met by solar, with a 3 pin UK plug socket as output to plug the appliance into?

Does such a device exist, and if it doesn't is there good reason for it not to exist?

[edit] I've found this http://www.amazon.co.uk/dp/B00C0D8C3W but it's unclear whether it will flow back into the grid?


texts: Why is the audio input from the microphone connected to the inverting input on the TPA6111A2?

texts:
As far as I know, when we connect a signal to the inverting terminal of an op amp, we get an amplified output which is 180 deg out of phase from the input. Going through the datasheet of TPA611A2, the input from the microphone goes to the inverting input. However, the LM386 has the input given to the non-inverting input. Can someone help me out regarding this?

The way I'm interpreting this is that giving the microphone input to the inverting terminal will shift the phase of the sound we want to hear by 180 deg, making it a different waveform from the original signal, changing the sound we'll hear altogether.


texts: Arbitrary switching of a large number of analog signals

texts:
I'm thinking about building a programmable patch bay for analog audio signals. There would be 24 analog inputs x 24 analog outputs with switching of any input to any output. Only one signal at a time per output (no mixing) but any input needs to be routable to any output. Control would be done from a small 8 bit MCU of some type.
I'm having trouble finding a solution for the switching that doesn't involve dozens (hundreds?) of 8 channel multiplexer/switch ICs. I found some 16 channel mux and switching chips, but those are considerably more expensive (and I'd still need a lot of them).
Is there some solution that I'm missing, or are there relatively cheap switching ICs that have 24 inputs (or 24 outputs; I think it could be done either way)?


texts:
I have been looking into the stackexchange searchbar and also I have been searching for a day or two globally, even the "similiar dialog on this website" when I was creating this post.
I have a bit experience with AMTECH and the NC 599 flux to do small stuff (yes there is better flux.)
I am trying to figure out what flux I should use for desoldering an LGA socket on my PCB bench.
I have done some homework around it since its my first to do something like this.
The AMTECH NC 599 flux is no good for rework, RMA 223 is garbage as well as the burning smell as I'm noticing from other people in their postings.
So with all the types of flux, what are your experiences?
I want to do it just about right from the first start with the motherboard i have here.
Can anyone suggest me the right/good flux to desolder the socket in no time so I can replace it with the new one (I know the steps.)


texts: How to limit the current of a short circuit

texts:
I will be turning a relay on from my circuit by sending a signal 500ms to 1000ms long, and i am trying to protect against poor wiring or faulty relay from the user that causes a short circuit on the relay which could blow the fuse on the module

The power supply is rated for 2A and the fuse on the module is rated for 1A. I would like to create a protection that even if there is some short circuit on the relay output the fuse cannot blow,

My solution was to add a resistor on series of the relay, but this would mean that resistor should have atleast 5watt rating for it to survive, or a high value resistance for it to survive. Having a high resistance also might mean that the relay might not turn on because there wont be enough voltage that will cross it.

Paralleling a resistor to the relay seem kinda useless also since the current will not flow to the resistor but to the short instead.

How should i approach this? i possible how can this be done with basic components (resistor,capacitor,diodes etc)


texts: Cutting off metal anchor legs on an HDMI port or Metal connector? What to use?

texts:
I'm looking for some advice on how to cut an HDMI port anchor leg off using some type of miniature cutting wheel. I bought a dentist micro drill, but I'm unsure which type of burs to purchase and type of metal alloy that can cut through this kind of metal.

currently the HDMI port is soldered onto a pcb board already and I can't seem to desolder it that easily as its mounted on 4 legs. The easiest solution i believe is to just cut off the legs.


texts: Looking to make a large surface area 13.56MHz antenna with short range

texts: I wondering about the feasibility of making a 13.56 MHz antenna that would occupy the entire rack of a shelf (5'x2'). The range would need to be small so that it only identifies entities that are sitting on the shelf. I was thinking of using 13.56 because anti collision is more widely used in HF. Is it possible to design this antenna at 13.56 MHz or is it better to do it at a low frequency and find a way to implement anti collision on that? Thanks for the help


texts:
I have a question about PhotoMOS relays like TLP3546A. Is it possible to connect two of these relays in parallel to increase Load current (upto 6A)??
I know there might be issues with Turn On and Turn OFF time


texts: How does a nine volt battery make a spark?

texts:
With a nine volt battery, touching the two terminals together (or using a faulty terminal) will cause a spark roughly where I would want it to be.

How is this possible? Is it ionizing only a very small portion of air surrounding the wires when this happens and it is just more visible? I believe at an extremely small distance, ~300v is the breakdown point of air (often, for example according to Paschen's law) so I do not understand how the battery can do this.


texts: What are some of the segmented displays with the lowest power consumption?

texts:
I have to select a low-power display for a solar-powered digital clock. I have looked into numerous technologies, including e-ink.

However, I was still unable to compare between them due to the lack of online information regarding average power consumption.

I am aware of the existence of solar-powered pocket calculators, which use some kind of 7-segment displays, so I know that it should be possible to build a  time-tracking device that is fully powered by light.

I can accept refresh rates as low as 1 frame per minute, but preferably I would like to have 1 frame per second.

The most stringent specification is power which, ideally, should be 100% supplied by a small solar panel.

Does anyone have a good suggestion for a good low-power display part that seems suitable for these specifications?


texts:
I am working on a part of a project for a university exam and it includes an interface with a touch screen.

The touch screen is a classic resistive four wire, it comes with a display of course. Datasheet is here.

We've chosen the  TSC2003-Q1 from texas instruments, it basically is a SAR adc that can also drive the resistive sheets, we've made the board and all seems to work but I'm having huge issues connecting the touch panel to the board.

The wire coming from the panel is a sort of FPC, you can see it in this photo:

So I've promptly chosen a ZIF FPC connector from molex, as per next photo:

The problem is that the "wire" coming from the panel is not exactly an FPC: they are usually made of plastic and the contacts are copper or some other metal that is chemically deposited on the plastic substrate, but this is different. The contacts seem to be of graphite or something similar and they're very weak, and here comes the problem. I've been very careful inserting and removing the fpc in the connector but the graphite has been scraped away by the contacts, in the first picture you can see clear spots on the dark grey strips, these are NOT metal strips but is the underlying plastic.

So here comes my question: what connector is suitable for this particular type of wire? Soldering is impossible, the plastic melts and the graphite messes up. Connecting another kind of wire to the screen is impossible too, the resistive sheets are part of the cable itself and the traces seems to be just "painted" with some sort of conductive material, just like the tip of the FPC.


texts:
I want to power 20 RGBW LEDs. Each of these lamps and each color channel should be individually controllable with PWM. Since it concerns pure LEDs without internal control I would like to use a PCA9632 for each lampe for each channel. Now each color channel needs about 3.2V at 0.7A. The IC doesn't manage this power of course. Therefore I want to install 4 constant current drivers each.

If I would now take a constant voltage source and connect the lamps parallel to it, a total current of up to 56A could occur which in many respects is very impractical and hardly feasible.

Therefore I would like to use a voltage source with approx. 24V or higher to transfer the power with thinner cables and somehow reduce the 24V to 3.2V or so far that exactly 0.7A flows through the LED.

As far as I can see there are two possibilities.

you could use an AC voltage source and use small transformers to reduce the voltage again.
one uses a DC voltage source and regulates the power via a kind of switching regulator to the 2.24W (0.7A * 3.3V) per colour channel.

But especially with the 2nd point I don't really know what the components are called and what to consider. With the PWM and a kind of switching regulator, radiation problems could also occur?
This kind of problem should have been solved by many people already.  Are there maybe open source designs for similar problems? Maybe there is another approach?


texts: Equations of Calculating Bus Transaction Times in usb2

texts:
I am relatively new to this field and I come up with these equations in chapter 5.11.3 in the document of the USB2 but I don't know how they are justified specially the constants like 2.083 and 3.167. Any help would be appreciated.

High-speed (Input)
    Non-Isochronous Transfer (Handshake Included)
        = (55 * 8 * 2.083) + ( 2.083 * Floor(3.167 + BitStuffTime(Data_bc))) + Host_Delay
    Isochronous Transfer (No Handshake)
        = (38 * 8 * 2.083) + ( 2.083 * Floor(3.167 + BitStuffTime(Data_bc))) + Host_Delay

High-speed (Output)
    Non-Isochronous Transfer (Handshake Included)
        = (55 * 8 * 2.083) + ( 2.083 * Floor(3.167 + BitStuffTime(Data_bc))) + Host_Delay
    Isochronous Transfer (No Handshake)
        = (38 * 8 * 2.083) + ( 2.083 * Floor(3.167 Host_Delay + BitStuffTime(Data_bc))) +

Full-speed (Input)
    Non-Isochronous Transfer (Handshake Included)
        = 9107 + ( 83.54 * Floor(3.167 + BitStuffTime(Data_bc))) + Host_Delay
    Isochronous Transfer (No Handshake)
        = 7268 + ( 83.54 * Floor(3.167 + BitStuffTime(Data_bc))) + Host_Delay

Full-speed (Output)
    Non-Isochronous Transfer (Handshake Included)
        = 9107 + ( 83.54 * Floor(3.167 + BitStuffTime(Data_bc))) + Host_Delay
    Isochronous Transfer (No Handshake)
        = 6265 + ( 83.54 * Floor(3.167 + BitStuffTime(Data_bc))) + Host_Delay

Low-speed (Input)
     = 64060 + (2 * Hub_LS_Setup) + (676.67 * Floor(3.167 + BitStuffTime(Data_bc))) + Host_Delay

Low-speed (Output)
     = 64107 + (2 * Hub_LS_Setup) + (667.0 * Floor(3.167 + BitStuffTime(Data_bc))) + Host_Delay


texts:
Hi I have a small Uc taking samples and sending results powered by a simple solar panel and supercap to get it through most of the night. It works but early in the morning when power is just enough to power the Uc it ends up restarting constantly as the voltage fluctuates on the verge.
I would like a simple circuit that is only on after it reaches a safe voltage ~3.2v. I found this article
Here but it looks lossy for a battery solution that matters in the UA range. could I do somthing similar with a Mosfet that uses nothing when off and next to nothing when on?


texts: Why Rod Core ignition coil in cars instead of E-I core or toroid core?

texts: Why use a Rod Core ignition coil in cars instead of E-I core or toroid core?  It appears the Rod Core coil in an automobile is just a Step-Up transformer.  Why do car manufacturers us a ROD CORE?  Is it superior for DC Pulses?


texts:
What is the best way to drive AC synchronous motor?
I have AC motor like this:

If I connect mains to 0 and 1 terminal it drives CW, if to 2 and 0 - CCW. In my project I have MCU that will drive motor, change rotation direction or stop motor based on signals from sensors. I don't need to control motor speed.
Is it OK in this case just to use electromagnetic relays? Simplified schematic is shown at picture below.


texts:
I am currently trying to impedance match a capacitor as a load. In detail, it is an insulating thin film grown on top of a conductive layer (grounded). We now sputtered small Pt electrodes on top and want to apply a voltage to these. We expect the capacitance in the area of 0.5 - 1 pF and our source has a 50 Ohm impedance. We want to apply square shaped voltage pulses with < 50 ps rise time (20 GHz) and up to 20 ns (50 MHz) length. Thus, the impedance matching circuit has to be very broadband.
Since I am not an electrical engineer, I would be very grateful if you explain any attempts to solve this problem as easy and detailed as possible.
EDIT:
I did the calculation to check the phaseshift of the back reflection. I obtain this graph:

it seems like I have the jump right in my bandwidth (approx 50 MHz to 50 GHz).


texts: Good practices for full-custom IC measurement?

texts:
I am a Junior Analog IC Designer and I want to characterize a full-custom IC. The thing is that I want to do it well and I don't know any reference with good practices and PCB design guidelines for this.

Part of this IC is an OpAmp so I also would like to check references with some background when testing and characterizing these circuits in the lab.

Thanks!


texts:
I am working on a Magnetometer AK8975 being a part of an IMU. Which seems to be very tricky for me. This chip gives a 3D vector as output describing earth's magnetic field at any place on earth or near it.

I tried two types of heading calculation algorithms:
One is simple arctan(-y/x) and another is inclination (pitch) and bank (roll) canceled maths as mentioned in below. Both on inclination and banks give wrong output.

I am able to get the correct heading w.r.t the earth (using simple available open study resources) when it is rotated keeping horizontal w.r.t the ground plan using any of the two algos.

I tried calibration for soft and hard iron errors. I Could plot it in 3D and shows a perfect 3D sphere. Still doesn't work on inclination or declination.

Any pointer will be helpful.

The code and its implementations are as below:

void Compass_Heading()
{
  double MAG_X;
  double MAG_Y;
  double cos_roll;
  double sin_roll;
  double cos_pitch;
  double sin_pitch;

  cos_roll = cos(roll);
  sin_roll = sin(roll);
  cos_pitch = cos(pitch);
  sin_pitch = sin(pitch);

  //// Tilt compensated Magnetic filed X:
  MAG_X = magnetom_x*cos_pitch + magnetom_y*sin_roll*sin_pitch + magnetom_z*cos_roll*sin_pitch;
  //// Tilt compensated Magnetic filed Y:
  MAG_Y = magnetom_y*cos_roll-magnetom_z*sin_roll;
  //// Magnetic Heading

  MAG_Heading = atan2(-MAG_Y, MAG_X) ;

}

Where magnetom_x, #_y and #_z are components of a 3D vector which actually are RAW values from the Magnetometer. roll and pitch are from a mysterious Kalman-filter output from onboard accelerometer and gyroscope. These three sensors are in ATAVRSBIN1. The roll and pitch are ok till this stage.

Now a simple heading calculation according to journal_of_sensors_renaudin et al_2010c.pdf  should have been MAG_Heading = atan2(-magnetom_y, magnetom_x) ; and with compensation as above.

Overall code is simply from OPEN AHRS.

Data in format Roll, Pitch and Yaw.
I rotated the device by my hand only.
First three have been concentrated on only Roll, Pitch and Yaw respectively.
Rest two are first rotated the device around 45 degrees along X (Rolled) then rotated along Magnetometer's local Z. Then same has been repeated with around 45 Degrees rotation along Y (pitched) then rotated along Magnetometer's local Z.

The graphs plotted within the range of -180 to 180 degrees.

Angles in degrees in a file The YAW characteristics on Roll.

Angles in degrees in a file The YAW characteristics on Pitch.

Angles in degrees in a file The YAW characteristics on Yaw itself.

Angles in degrees in a file  The YAW characteristics on Yaw with 45 degrees rolled.

Angles in degrees in a file  The YAW characteristics on Yaw with 45 degrees pitched.

Note: For last 2 pictures:
First kept in home position, that is same for all (refer txt files). Then Rolled 45 degrees then using the plane device (with magnetometer) has been rotated along Magnetometer's Z-axis.

Similarly for last image the device has been pitched 45 degrees then along Magnetometer's Z-axis.

I hope these will help solving my issue.

New developments are as follows:

I worked some on the Heading. I got following output.

csv

csv

csv


texts: Accidental short circuit of lead acid battery, can I still use it / charge it?

texts:
Just a minute ago I accidentally short circuited my lead acid battery. The wiring touched, glowed bright, the plastic around it melted and smoke got released, but I'm not sure from the battery or from the plastic. It smelled like plastic burning, so I'm hoping the latter.

The battery discharged quite a lot and the voltage dropped from ~12.80 volt to around ~12.55 volt.

However, this short circuit lasted only a fraction of a second, the wires only touched and they almost immediately lost contact. The battery seems to still be working, but I'm not sure if it's safe to charge.

Is it safe to assume I can still use it properly? It's the first time I short circuited something like this and it scared me a bit ha.


texts: Low level sine to pulse converter with sharp rising-edges

texts:
I have two circuit simulations: Circuit1 and Circuit2 which are shown in above schematics. For the sake of simplicity I drew them in the same schematics. They share the same 12V voltage source and the same signal input VG1. VF1 is the output for the Circuit1, VF2 is the output for the Circuit2 and VF3 outputs the input signal VG1. Zener diode in Circuit1 is a 6.8V zener. Both circuits use LM2903 comparator.

Circuit2 is the one I had before and it could only convert sine inputs more than 60mV peak to peak.
With a suggestion from my previous question I simulated Circuit1 and this can convert sines around 6mV now.

That was great but when I plotted the results I found out the comparator's pulse outputs are not sharp in mV level inputs. Here is an output for 6mV sine:

As you can see VF2 is hopless. VF1 can handle 6mV sine but the pulses are not sharp.

Another thing I observed for 80mV sine input is that, Circuit2 output is not in phase with input signal but Circuit1 output is. But Circuit2 on the other hand produces sharp pulses unlike Circuit1. Here is the plot:

And finally for 1V sine input, both pulses are quite sharp and they are both in phase with the input signal. And the plot becomes as follows:

It seems like for minimum phase differences and minimum sine inputs better to use Circuit1. But then for mV level sine inputs I'm not happy with the sharpness of the output pulses.

My questions are follows:

1-)What would be a quick fix for Circuit1's sharp-pulse problem without using another op-amp?

2-)If another op-amp is definitely needed, would it be that a Schmitt trigger should be added to the output of Circuit1?

a suggested circuit(waiting to be edited):


texts: Serialize bits from input/output pin with VHDL

texts:
The code below reads 40 bits of data sent in serial from a DHT-11 temperature/humidity sensor and
stores the data in a 5 byte array of RAM.

The code is:

// Return values:

// DHTLIB_OK              0 => OK
// DHTLIB_ERROR_CHECKSUM -1 => Checksum error
// DHTLIB_ERROR_TIMEOUT  -2 => Timeout

int read(int pin)
{

    uint8_t bits[5]; // BUFFER TO RECEIVE
    uint8_t cnt = 7; // bit counter 0..7
    uint8_t idx = 0; // buffer index

    // EMPTY BUFFER
    for (int i=0; i<5; i++) bits[i] = 0;

    // REQUEST SAMPLE
    pinMode(pin, OUTPUT);    // set pin for output
    digitalWrite(pin, LOW);  // write '0'
    delay(18);               // delay 18ms
    digitalWrite(pin, HIGH); // write '1'
    delayMicroseconds(40);   // delay 40 microseconds

    pinMode(pin, INPUT);     // set pin for input

    // ACKNOWLEDGE or TIMEOUT
    unsigned int loopCnt = 10000;
    while(digitalRead(pin) == LOW)
        if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;

    loopCnt = 10000;
    while(digitalRead(pin) == HIGH)
        if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;

    // READ OUTPUT - 40 BITS => 5 BYTES or TIMEOUT
    for (int i=0; i<40; i++)
    {
        loopCnt = 10000;
        while(digitalRead(pin) == LOW)
            if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;

        unsigned long t = micros();  // this function returns the timestamp in microseconds

        loopCnt = 10000;
        while(digitalRead(pin) == HIGH)
            if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;

        if ((micros() - t) > 40) bits[idx] |= (1 << cnt);
        if (cnt == 0)   // next byte?
        {
            cnt = 7;    // restart at MSB
            idx++;      // next byte!
        }
        else cnt--;
    }

    // WRITE TO RIGHT VARS
              // as bits[1] and bits[3] are allways zero they are omitted in formulas.
    humidity    = bits[0];
    temperature = bits[2];

    uint8_t sum = bits[0] + bits[2];

    if (bits[4] != sum) return DHTLIB_ERROR_CHECKSUM;
    return DHTLIB_OK;
}

I'm beginning to FPGA developing, but I can't catch some concepts of VHDL, such as poling
a pin of a FPGA.
For testing, I'm using a Xilinx Spartan 3E with a clock of 50 MHz.

The C function that returns an int (Ok, checksum error, or timeout error).

The equivalent VHDL code doesn't do that, of course, but instead, stores the int in a variable.

Can you please, help me convert the code above to VHDL?


texts:
I'm working on a zero crossing detector using an optocoupler, and to reduce the voltage from the mains (240v 50Hz), I took a little transformer from a 23 Watts CFL:

As I measured it, the secondary gives out 20-25V when open, but only 0.003V when connected to a 1K resistor.

The transformer have markings:

simulate this circuit – Schematic created using CircuitLab

Did I misidentify the component? It's broken?

Edit

I looked at the PCB and the unmarked pin in the "primary" side is unconnected to anything. The pin just sit in a hole in the plastic (no solder, no traces).


texts: What Schottky diode would be contemporary to the 2N2222 transistor?

texts: I'm working on a "retro" discrete design that is meant to use components that were available in the mid-1960s, but are still available today. The main building block I'm using is PN2222 - a cheaper packaged 2N2222 that got introduced in 1962 (!). A 60 year availability of that part is hard to beat. But what about Schottky diodes? What common Schottky part numbers were introduced around that time (say 1960-1969)?


texts:
How do I linearize the graph analog output voltage against distance for IR sensor [GP2Y0A21YK][1]?

This is the non- linear graph, I’m not sure how to make it linear?
  [1]: https://media.digikey.com/pdf/Data%20Sheets/Sharp%20PDFs/GP2Y0A21YK.pdf


texts: Resources for learning about transistor configurations?

texts:
I'm currently taking a circuits class that discusses various transistor amplifier configurations eventually culminating in building an op-amp. This includes various configurations such as the darlington pair, cascades, or cascode transistors. Are there any good online resources I could check out to help me study that you guys know of? I've been looking for awhile now but all my searches overwhelmingly return results for basic circuits 1 classes, and I can't seem to find what I'm looking for.

Thanks in advanced.


texts: Which microcontroller to use to control Yamaha YM2612 arpeggiator?

texts:
Okay guys, I searched the forum and didn't find anything relevant.  Here it is:

I am planning on building an arpeggiator project based on the Yamaha YM2612 IC which was the sound chip used in the Sega Genesis console.  I ordered the chips online and am waiting patiently for them to get here, and meanwhile researching as much as I can to find out what I need to do to make this project work.

My question is: which of these microcontrollers would be the best to use for this project?  (These are the microcontrollers I already own, although I could buy another one if none of the ones I have will work)

*-Arduino Uno R3

-PIC 18

-Raspberry PI

-Arduino Nano

-Teensy x.x* (I do not own one of these but this may be the best option based on other projects I have seen.)

I would guess that the PIC18 would be the best to use since I could program it in assembly language, but I am just now beginning to learn assembly language and C would be much easier for me.  I saw a guy on YouTube who was using an Arduino Uno who built a project like this and it wouldn't run corrently, and he suspected that it was due to latency problems, so maybe the Arduino is out.  Any help here is welcome.

For a little bit of background on the YM2612, it is a 6-channel FM synthesis chip with 4 operators which can be routed in 8 different configurations.  It uses data exchange to write values to its internal registry to alter parameters like attack, decay, sustain, release, frequency, amplitude, etc.  It is suggested to operate at a 7.67 MHz frequency and so I was planning on using an 8 MHz crystal oscillator (resonator) to provide the clock.  Eventually I will integrate this project with a keyboard that outputs midi data (or maybe even bypassing midi, just using the microcontroller to control the chip manually) so I will be leaving this project open for further changes/revisions.

Also this is my first project of this type, I know it could be considered a big bite but I am here to learn.  Any help is welcome, thanks guys

P.S.
Here is a datasheet for the YM2612:
- http://www.datasheetspdf.com/PDF/YM2612/865751/1

...and here is a video of something similar:
- https://www.youtube.com/watch?v=XlDlF1MOaUA


texts: What is the name of this schematic, and what it is used for?

texts:
I've got this schematic of a device I need some information about.  It it was in electronics class I had, but I do not know the name of the schematic.
The problem is, I can pretty much see what it does, it buffers the DataOut signal, when the Enable pin is HIGH, but why do we need the PullUpEnable, and shouldn't it be "PullUpDisable", sice we stop pulling up when it is HIGH.
Can someone tell me if he/she has used this device, or if you know the name of the device and where it is used, so I can make a further google research?


texts: I am working on a project that requires low latency wireless point to point audio transmission at short distance using a digital transmission technique  (ideally 24bit 96khz audio, 30 metre max) at a latency that is less then 5 milliseconds, the lower the better. What wireless protocols and frequency ranges are available that allows this?


texts: AVR USART wait for AVR's reponse to continue text stream

texts:
AVR USART wait for AVR's reponse to continue protocol

I am doing a senior project, and I need to send a large text file line by line to an AVR (atmega32) which will control a piano using ~36 solenoids and shift registers. This needs to be done automatically and very fast. I cannot mannually input the text in the terminal. I need to send 3 strings, line by line to an AVR and wait between each line for a confirmation to continue form the AVR.

The text file is a converted midi file which contains 3 usefull information (the time of the event, the note, and the status (press note or unpress). The text file looks like this:

  213, 25, ON
  321, 25, OFF
  521, 36, ON --> which represents play the Note C at time = 521 ms

  Where the first string is the time of the event, the second is the note and the third is the status of the note

The protocol would need to look like this:

The PC sends 3 string to the AVR. So total of 3 USART transfers.
The PC waits for AVR to send an aknowledgement to continue transfering the next line of text
The AVR plays the "event" on the piano and at the end send a confirmation to the PC to send the next lines of text

How is this achievable?

Why am I doing this?

The problem is that I can't store all the text file in an array of because the AVR is too small(the largest atmega is 512Kb if I recall well)
I need to stream the text file using the terminal (Hyperterminal) line by line.
BUT how to send a line using the terminal, wait until the atmega finished the process --> send a confirmation back to the PC to stream the next line?


texts: Building a motorcycle accessory power connector - Values for capacitors and diodes?

texts:
After finding out that a component I wanted to base a circuit around isn't suitable, I've found a possible replacement part, but I have questions about the values for Cin and Cout capacitors and the D1 diode.

The datasheet under the 'Fixed Circuit' diagram doesn't give me any hints as to the correct values for Cin, Co or D1. From other reading, it looks like a 1N4002FSTR-ND diode would do the job for D1. But how do I work out what I should be using for Cin or Co?

From what I understand, these are used to filter both input and output or stablise things, but I don't understand how you would select appropriate values for a circuit like this.

The circuit I'm trying to build can be seen below:

There is a single 12 V unfiltered output, a 5 V output with a filter (for audio devices but that provides for lower amp functions) and a 5 V unfiltered output for higher current uses (GPS and charging cell phone).

Sorry about the lack of inline images and the absence of an image for the DC-DC component, but as a new user, I'm not able to post images or more links than I have. I will add a comment with a link to the DC-DC component, taken from the datasheet.

The DC-DC component:


texts:
I renamed my .brd file, but when I tried to open it, I got this error message:

Error:

line 1, column 2: Premature end of document.

Is there any way to recover what I've lost?


texts:
I am working AD5259 , its a digital potentiometer.

Its connected to i2c bus on raspberry pi.
But the address of device is not shown. Datasheets says its 0X18.

I guess the device does not respond to general call.

I am kind of stuck on this , any help will be apprecaited.


texts: I'm a little confused by the two terms. What do data rate and data volume mean and what are the differences?


texts: prioritized power path controller for battery backup

texts:
I'm searching for a simple solution for a prioritized power path controller to maintain a system supply line through a rechargable battery when the main supply fails.

My goal is to make the cheapest solution. During a long searching on the internet I came accross Ti's design Dual Power Path Multiplexer Reference Design. It uses a voltage window comparator and two couples of back-to-back mosfet for the changeover.

I studied the circuit (Page 8, Figure 4). carefully and I can see a basic problem here.
Considering the secondary rail a Li-ion battery 3.7V and the primary rail with a significant greater voltage, for example >5V or >12V.
In that case, when the primary rail fails, after the switchover and exactly after the Q1 is fully on (lowest Rds) the battery will see a charged capacitor (C1) with a primary's rail voltage, because when the mosfet is on it does allow the flowing of reverse current. If the load's current is very low, the Capacitor on the load will not discharge enough during the switchover and that remaining amount of voltage may cause damage to the battery.

I found that the problem is solved by ideal diode controllers or ORing controller but I wasn't able to find anything reasonable cheap.
In addition, my circuit (load) demands current above 2.5A.
Unfortunately, some embedded and cheap TI's chip, are capable to handle maximum 2A.

The TI's schematic above, does not implement any solution for reverse current blocking while the mosfets are on.


texts: How do we calculate effective resistance of a NMOS, operating in linear region across drain and source?


texts: PCB ground plane separation between power and analog sections of board

texts:
In this design I have separated the ground plane of the sensing/controlling circuit from the high-power 3-4 amp circuit. This is a current controller.

The ground planes are joined at the sensing resistors and control signal.
The Analog ground is provided by a DC/DC converter common.
The Power ground is the ground of the main power supply.

Did I do this correctly?

Alright so I redesigned the board. I was able to keep all but one trace in the bottom plane. The is also a trench separating some of the high current traces from the control circuit.

I am using both a top and bottom ground plane pour because this board will be made on copper clad; through hole components mounted on top can only be soldered (well) on the bottom layer. Now, this creates ground islands in the bottom layer. I tried to place the vias close to were the components terminate so the ground return path would not be altered that much.

One concern I have is that one of the traces to a BJT base is longer than I want... High input impendence makes it vulnerable to noise. I don't have enough experience making boards to know if this is bad design or not ( shown bellow)


texts:
I'm working on an MRI research project where I need to power my device with a single BNC cable.  Internally my device needs 15V, -8.5V, 5V, 3.3V and 1.2V supplies. The 15V, -8.5V and 1.2V only need 10mA each, but the other two need 500mA.

I can't use any inductors and LDOs will produce too much heat for the two big loads.  I have limited ways I can cool the device (can't find any magnet-less fans. :)  My existing design uses a 5V input (on the BNC) and I use 4 different groups of many small charge pumps in parallel to get to the other voltages.  At 5V the BNC is almost maxed out on current (BNCs are for signals of course but, this is crazy MRI land :)

I want to switch to a 16V supply:

LDO down to 15V
Invert and LDO down to -8.5V
Step Down Pump to 8V and LDO to 5.0V
Step Down Pump to 4V and LDO to 3.3V
LDO down to 1.2V

The problem is all the parallel pumps to handle my two 500mA loads. Most commercial charge pumps that I have found, are meant for low current applications in the <50mA range.  This makes sense for the huge collection of devices that operate in this range and the fact that charge-pump efficiency suffers at higher currents.  Just switch to inductor based boost and buck converters, right?  Of course who thinks about MRI, other than folks like me who have to deal.

Has anyone had a good experience building a "medium current" charge pump?  As much as heat is a problem for my device, as it is for many, I can tolerate a charge pump efficiency that is somewhat less than the state of the art.  So I have been thinking about a discrete design using a 555 timer and external "medium current" switches (BJTs,...)

The other thing that I can tolerate and is actually helpful, is lower than "state of the art" charge-pump switching speeds.  I need to be quiet in the 100MHz range.

I have some design flexibility, but would love to start from point of SE wisdom.

Thank you so much for your help.


texts: Why do LEDs in simple battery circuit flash?

texts: I have an LED flashlight with 13 LEDs. Some of the LEDs do not light, but some flash regularly at different rates, and some flash irregularly.  The circuit is simply a resistor in series with the lamps, which are in parallel, and a six volt lantern battery.  I have disassembled the  flashlight, bypassed all contacts, and checked the resistors.  The voltage across the LEDs is a steady 6.04 volts.  Why do they flash?  Posts suggest flashing is not a recognised failure mode of LEDs.


texts: Can a probe with readout actuator be used on a scope without readout feature?

texts:
Some oscilloscopes can detect the attenuation set on the probes in use ("readout"), if the probes have the corresponding protruding activator pin. The probes are mostly offered with or without this feature. The former beeing more expensive.

Can such a probe with readout actuator be used on a scope, which doesn't have this readout feature?

I found a decent probe kit which is only availabe with readout. Also it could be useful should I buy a scope with readout later on.


texts: CircuitMaker warning: How to define ports?

texts:
I created a (for me) fairly big (multisheet) circuit diagram in CircuitMaker. However, I get several warnings/errors after clicking Outputs/Electrical Rules Check. One of them is below; how can I fix it?

[Warning: Net U13_16 contains IO Pin and Output port objects (Port GPIO_LATCH)]

And in another sheet where I use the GPIO_LATCH, I get the error:

[Warning: Net NetU26_12 has no driving source (Pin U26-12, Pin U27-12, Pin U28-12, Pin U29-12)]

Note the GPIO_LATCH is used for SPI and need to be connected from one GPIO pin from the MCU to 4 daisy chained 74HC595 multiplexers.

I also tried flipping the type from input to output and some combinations, but in all cases I get some warning(s).


texts: Theoretical infinite voltage here! Where's the problem?

texts:
Update: Thanks Spehro Pefhany for finding the issue!

I've got a formula deduced which should - in theory - suggest that a battery with no external load connected should have an infinite external voltage, however in practice this obviously isn't the case!
Steps are listed below to get to the conclusion, any ideas where something's amiss?

Consider the following series resistors:

The ratio between \$R_1\$ and \$R_2\$ is the same as \$V_1\$ and \$V_2\$, with \$V_1\$ and \$V_2\$ being the voltage across resistors \$R_1\$ and \$R_2\$, as shown below:

$$
\begin{aligned}
&R_1 : R_2\\\\
=\ &\frac{V_1}{I} : \frac{V_2}{I}\\\\
=\ &V_1 : V_2
\end{aligned}
$$
Therefore, in terms of the two series resistors in the diagram, this equation is valid:
$$
\frac{V_1}{V_2} = \frac{R_1}{R_2}
$$
Now, consider the following schematic of a battery with internal resistance \$R_{\text{int}}\$ (excuse the multiple cells), and external resistor \$R_{\text{ext}}\$:

Resistors \$R_{\text{int}}\$ and \$R_{\text{ext}}\$ and their subsequent voltages can be substituted from the \$\frac{V_1}{V_2} = \frac{R_1}{R_2}\$ formula, into:
$$
\begin{aligned}
&\frac{V_\text{ext}}{V_\text{int}} = \frac{R_\text{ext}}{R_\text{int}}\\\\
\therefore\ &V_\text{ext} = \frac{R_\text{ext}}{R_\text{int}} \times V_\text{int}
\end{aligned}
$$
We've ended up with a formula to calculate voltage across \$R_{\text{ext}}\$, which is the same as the external voltage of the battery.
However, what if \$R_{\text{ext}}\$ were to burn out or be disconnected, but voltage across it (the battery) is still measurable?
Essentially \$R_{\text{ext}}\$ now has a resistance of \$\infty\$, as no current is flowing through, meaning the battery has no external load attached.

Therefore, working out the limit of \$V_{\text{ext}}\$ as \$R_{\text{ext}}\$ approaches \$\infty\$ :
$$
\begin{aligned}
V_{\text{ext}} &= \lim_{R_{\text{ext}}\to\infty} \left(\frac{R_\text{ext}}{R_\text{int}} \times V_\text{int}\right)\\\\
&= \frac{\infty}{R_\text{int}} \times V_\text{int}\\\\
&= \infty \text{V}
\end{aligned}
$$
This is an unusual result, and obviously doesn't work in real life. The math seems alright, but something has to be amiss. Any suggestions?


texts: Can LED be controlled using PWM pin without using a FET in LT3475?

texts:
I am designing a LED driver circuit using LT3475EFE-1#PBF IC for controlling two LEDS. I have a  signal from an I/O pin for LED ON-OFF control which is tied to PWM input (as recommended). Typical circuits tie an NFET to the cathode of LED and the gate is controlled by PWM input.

Can I connect my control signal to PWM pin and perform LED lighting without using a NFET? I don't want to achieve LED dimming control, just switching action is enough.

Any help would be appreciated as I need to design the circuit in mass scale.


texts: How to charge lipo with a laboratory power supply?

texts:
I've bought a good laboratory power supply (0...30V and 0...5A).
I'd like to charge my 3S Lipo Battery Pack with it.

How to do this?


texts: Has anyone got a proven recipe to attenuate wi-fi with a Faraday cage?

texts:
I need to put a domestic wi-fi router in a homemade Faraday cage that will severely attenuate the signal. Has anyone actually DONE this?

There is lots of good advice of what should work, but  few reports of what actually did work.

The nearest, on Youtube, is someone putting the router in three big nested heavy metal trash cans. That works good, but I've got no room for kit that bulky.

A great-sounding suggestion is to cover a box in 2 layers of aluminium foil, so there is high capacitance between the two layers.  I tried this and it didn't work, maybe because I re-used old foil and it wasn't flat enough.

In general aluminium foil is useless - it is like Wile E. Coyote and the Road Runner, the signal just laughs at it.

Perforated metal sheet a few mm thick is meant to work. If no answers here that will be my next attempt, but I'd love to know if anyone has actually done this in any way.

Many thanks


texts: VHDL : how to write data in FIFO (first in first out) and read data with diffrent clocks for the writing and reading?

texts:
So I have this problem . I need data to be saved in a FIFO . but the problem is that the I need different clock for the writing and the reading . for exmaple I need that MY FIFO will write the data in frequency 50 M Hz ,and after the FIFO is full to read this data but with frequency  of 960 Hz . I know that in point of hardware it is not possible because in FIFO you have the same clock for writing and reading . But is there any other way to save data in some sort of memory and then read this data from the memory in different frequency  ?

I drew simple pic of my meaning


texts: Where can i find the datasheet for this component (RF2001)?

texts: Where can I find the datasheet for this component (RF2001)?


texts: How do I increase (multiply) the value of a current sink?

texts:
I have been shown an IC that is a current sink PWM dimmable LED regulator. It happens to be a WS2811. While this works well for low drive currents (up to about 20mA), I was approached with the idea of making it drive power LEDs (~1 amp @ 3 volts).

I immediately thought of using a PNP transistor in this configuration:

simulate this circuit – Schematic created using CircuitLab

While it does demonstrate power gain, the efficiency is terrible!

We would like to make this solution use as few components as possible. Since this is not an opinion-based site, please illustrate examples of highly efficient methods of "multiplying" current sinks, say by a factor of 100. The major constraint is component count.


texts: Convert TTL levels to RS232 of FTDI USBSerial

texts:
Have this small interface FTDI FT232RL to connect a Serial device to the computer via USB.

It has been working well for most of my Serial applications, except today when I tried to use it for a Roboteq controller. While all settings are correct, characters are garbage.

The support tells me the FTDI device use TTL levels (0~3.3/5V) instead of RS232 (-9~+9V). Which seems to be unfortunately correct according to the FTDI doc.

Question

  Is there a simple way to have this FTDI device consider RS232 levels, not TTL? (eg like shorting a couple of pins) The Roboteq device doesn't seem to be configurable in this regard.


texts: Wireless communication between multiple microcontrollers?

texts:
I have 3-6 microcontrollers, up to 2m apart. One of them is designated the server and will be fed sensor data from the others, at least at 100 Hz. (Each data point is just a couple of bytes)

Since the microcontrollers move around, I can't connect them with wires. What's a good wireless solution here?

My initial idea was Bluetooth, mainly because that's the one solution I'm familiar with, but Bluetooth consumes much power (my circuits will be battery-powered) and Bluetooth modules are expensive.


texts: stm32 keil cannot assign array in interrupt

texts:
I can not assign my array in interrupt.
My main.c function is like this:
volatile uint32_t buffer[BUFFER_LENGTH];
int main(void)
{
  while(1)
  {
    sprintf((char*)string,"%d",buffer[0]);
    BSP_LCD_DisplayStringAt(250, LINE(9), (uint8_t *)string, LEFT_MODE);
  }
}

Interrupt routine is like this:
void EXTI3_IRQHandler(void)
{
    buffer[0] = 100;
}

The display always shows 0!
The strange thing is that when I use a variable instead of an array everything works fine!
uint32_t variable;
int main(void)
{
  while(1)
  {
    sprintf((char*)string,"%d",variable);
    BSP_LCD_DisplayStringAt(250, LINE(9), (uint8_t *)string, LEFT_MODE);
  }
}

void EXTI3_IRQHandler(void)
{
    variable = 100;
}

The display shows 100! Why can't I use array in interrupt routine?


texts: RS-232 and RS-485 software configurability?

texts: I would like to connect a anemometer(RS-485, DB9) to the PC. The PC has a serial port with DB9 connector. I couldn't find the specification of the serial port. Is that RS-232 standard or RS-485? Most commonly used the RS-232, so I assume that is RS-232. Is there a possibility to configure the serial port from RS-232 to RS-485, or I just need a RS-232/RS-485 converter?


texts: Why don't my LED Christmas Lights change color at the same rate

texts: I purchased 100 LED C7 - Color Changing, Candelabra Base, Christmas bulbs. They screw into regular 120 Volt string cords that I used to have 25-5 watt incandescent bulbs in. When the lights first come on, they are all the same same color but after that, they all change colors at different rates; the same order of color but at different rates. I'm sure these are mass produced with all the same parts produced at the same time. So why the different rate of change?


texts: RF Power measurements with Spectrum Analyzer

texts:
I'm trying to learn how to properly measure output power with my spectrum analyzer.   I have a transmitter datasheet that claims 15dBM typical output power with BPSK.   Assuming the matching network is correctly matched to 50 Ohms, and I can configure it for constant transmit mode.  Then if I just plug this transmitter into my SA should I expect to see a peak of 15dBM (well minus any cable loss) or should I expect to see half that because the source impedance is 50 Ohms so it acts like a voltage divider.

Or have I missed the mark entirely and I need to integrate the power over the entire channel width or something like that.

Data sheet is not very helpful it just says what I said above.


texts:
I need to know if this circuit is efficient to transfer most of the current from several identical independent 2 phase dynamos. The converters are all the same and ideal for the voltages no problem with that.

Is this the correct way? Thanks!


texts: Do I need to buffer these sensor outputs in this scenario?

texts:
I'm planning to use this uC board's LCD to read the humidity and temperature sensors' outputs.
Here is the datasheet for the humidity and here is for the pressure sensor.
Since the ADC of the uC is 3.3V range. The sensors are max 5V output so I will use a resistor divider like such as below:

I will measure the precise ratio for the resistor divider above to implement in uC code.
Humidity sensor datasheet has the following figure:

Do I need to buffer the sensor outputs before the divider if I don't want to introduce resistor divider loading error down to 5%? I cannot find the output impedance of the sensors.
EDIT:


texts: I am new to electronics. I have a 2-phase stepper motor. In data sheet was wrote drawing current is 1.5 amps/phase. I want to know is this current the total consumable current for this stepper motor or it should be multiplied by number of phases i.e 2*1.5  = 3 amps ? Thanks in advances.


texts: voltage regulator using L7805CV from Centre Tapped Transformer

texts:
I have a 28V-0-28V, 7Amps centre tapped transformer to supply voltage to my load. Load will be a cell (plates are connected in both series and parralel) used in Chlorinator. I have a voltage regulator L7805CV. The link is below. [http://www.farnell.com/datasheets/2307057.pdf?_ga=2.224828637.639084130.1536017950-602646683.1536017950][1]

What I want is to use the same centre tapped transformer for the voltage regulator to get 5V. From the datasheet I found that Vi for regulator has to be around 10V to get Vout 5V. But the transformer is rated at 28V-0-28V. How can I drop voltage after Bridge rectifier but before feeding on to voltage regulator, Vin?


texts: level shifter alternatives using passives

texts:
I have always used level translators when communicating between 2 systems(or controllers) of different voltage levels. For eg txb0108 is a commonly used one, among a host of others.
Now, why should one use such an ASIC. Why can the same be not done using a voltage dividor or such a simple and cheap component ? What is the major game changing advantage when we use such dedicated ASICs ?
Ofcourse, these ASICs might come power packed with buffers and such facilities, but if it was a straighforward voltage level lowering can the resistors suffice ?


texts: Why is the sensor value at the optocoupler wrong?

texts:
I am using six inductive sensors in my circuit. Four of them are working fine, but two sensors are showing very weird behaviour.
I am using an optocoupler to read their output to the MCU for isolation:

Sensor 1 problem: When I measure the voltage on the optocoupler's phototransistor when there is no output on the sensor it shows only 1.2V, but it should show 3.3V because it is pulled up to 3.3V.
Sensor 2 problem: When there is output from the sensor, the voltage on the optocoupler should be tending to zero, but it stays at 3.2V.
I am using the same circuit for all six sensors.
Pull up resistor value is 4.7K


texts: What can be causing output voltage to drop on LT1763 with very little load?

texts:
On a breadboard, I am using an LT1763 5V regulator connected as per the "Typical Application" diagram on page one of the datasheet (LT1763 DataSheet).  From a benchtop power supply I give 12V at the input and measure a steady 5.011V on the output.

Now, if I add a 10K resistor between the output and ground (which should only draw 0.5mA), the output voltage sinks to around 4.8V. I put an ammeter on the input line and can see that the regulator is only drawing well less than 1mA.  This regulator is rated to 500mA.

I swapped out a 3.3V regulator and see similar behaviour (output voltage drops to well below 3V with the resistor applied). I moved around to another location on the breadboard and still the same.  Checked all the capacitors on my Fluke and they are all good. Tried different input voltages from 6-15V and the behaviour is the same.

There is nothing else connected to this regulator and I am completely stumped.

Any ideas as to what I am missing and why the voltage could be dropping so much?


texts:
I am new with FPGA and timing constraints, so I apologize if the question will sound stupid.
I try to understand timing constraints usage with FPGA.
I have found the following description (in https://fpgawiki.intel.com/wiki/Timing_Constraints):

  In a synchronous design you need to define the clocks used in the
  design. There are three types of clocks you can define:

  Clocks at FPGA clock input PIN
  Virtual clocks which are used to
  describe the clocking of FPGA external registers (external device
  registers)
  Generated clocks which are derived other clocks

  The command for creating clocks at FPGA input pins and virtual clocks is the same.
  The only difference is that you don't specify a FPGA input pin for
  virtual clocks. Because of this they are both listed under
  create_clocks.

I would like to ask:

Is it that "virtual clocks" are not really used in design, but just used for the timing analysis ?
I don't understand what it means to put a timing constrain on a real external pin clock. Is it that the timing constraint will change the real clock (I can't believe that it is possible without using a PLL) ?


texts: I believe DC motors accelerates from 0 to maximum speed when power is applied. Let's say, it takes 5 seconds so that the DC motor could reach the maximum speed given certain power. Is it possible to rotate (or give torque) to the DC motors so it can reach the maximum speed directly (say at half a second)?


texts:
I'm working on a simple front I/O board that connects to a PC motherboard. There is a standard connector in the  "Intel Internal Connector And Cable Specification" that give a pin-out table of the internal motherboard connector. I have verified that my motherboard matches this.

The one thing I am confused about at the moment is the purpose and function of the "ID" pin included in the header.

Obviously, this forms part of some overcurrent protection circuit, but I have no idea what I'm supposed to do with it.

Am I just supposed to ground it? Leave it floating? Put some sort of current shunt on it? Have my own over current detection circuit and use this pin to signal over current events?


texts: Sensor output intentionally coupled to its power supply net

texts:
Fellow EE's,

I've seen a couple of sensors using a coaxial cable connection where one terminal is both power supply to the sensor AND the sensor output itself(AC signal).
The manufacturer datasheet shows the following circuit as an example:

simulate this circuit – Schematic created using CircuitLab

May I ask for your input on the following:

1 - The sensor from this picture has a built-in preamp. What sort of circuit would be used on the preamp to power it and couple the sensor output on the same net without loading the passive filters connected to it?

2 - Is this a common technique? If it is, what's the name used on literature and troughout the industry?

Sensor info: Datasheet


texts: Are there any alternatives for 74LS__ chips?

texts:
A beginners electronics book tells me to get the following:
74LS92 counter chip, 74LS06 open-collector inverter chip, and 74LS27 triple-input NOR chip.

Now, this book is from a couple years back, and I see that these chips are quite expensive on eBay (I have to pay $6 for 2x the first one, e.g.)

So I'm wondering, are there any alternatives to these that would be cheaper/more readily available? How could I know this?


texts: Differential and Multistage Amplifiers(BJT)

texts:
I want to determine the currents in each of the branches.

  I could analyse the current mirror portion and the differential amplifier portion, but facing problem thereafter.

  I could find the collector current of \$ Q_2 \$.But i need to find
  the current through \$ R_C \$ connected to \$ Q_2\$,to find
  \$ v_{O2}\$, which in turn would help me in analysing \$ Q_3\$(ie finding collector and emitter current of \$ Q_3\$ ).

  I dont want to assume that current through base of \$ Q_3\$ is zero.

Parameters:

\$R_1=12k\Omega\$

\$R_C=8k\Omega\$

\$R_E=3.3k\Omega\$

\$ \beta=200\$
\$\$
\$\$
\$\$
\$\$

simulate this circuit – Schematic created using CircuitLab

My attempt:

ANALYZING THE CURRENT MIRROR PART

Let current through \$ R_1=I_1\$
$$I_1=I_{C4}+I_{B4}+I_{B5}$$
(Since \$V_{BE}\$ is same for both transistors and transistors are identical, \$ I_{B4}=I_{B5}\$ and \$ I_{C4}=I_{C5}\$)
$$=I_{C5}+2I_{B5}$$
$$=I_{C5}+2\frac{I_{C5}}{\beta}$$
$$=I_{C5}(1+\frac{2}{\beta})$$
$$I_{C5}=\frac{I_1}{1+\frac{2}{\beta}}$$

ANALYZING THE DIFFERENTIAL AMPLIFIER PART

Let \$I_{C5}=\frac{I_1}{1+\frac{2}{\beta}}=I_E\$

$$v_1-v_{BE1}=v_2-v_{BE2}$$
$$v_1-v_2+v_{BE2}-v_{BE1}$$
$$v_{ID}+v_{BE2}-v_{BE1}=0$$

Now,
$$v_{BE1}=V_Tln(\frac{i_{C1}}{I_{S1}})$$
$$v_{BE2}=V_Tln(\frac{i_{C2}}{I_{S2}})$$
If \$I_{S1}=I_{S2}\$
$$\frac{i_{C1}}{i_{C2}}=e^{\frac{v_{BE1}-v_{BE2}}{V_T}}=e^{\frac{v_{ID}}{V_T}}\tag1$$

Nodal equations at the emitter:

$$I_E=i_{E1}+i_{E2}=\frac{1}{\alpha}(i_{C1}+i_{C2})\tag 2$$

Substituting eq (1) in (2) we get:

$$I_E=\frac{1}{\alpha}(e^{\frac{v_{ID}}{V_T}}i_{C2}+i_{C2})$$
$$=\frac{i_{C2}}{\alpha}(e^{\frac{v_{ID}}{V_T}}+1)$$

$$i_{C2}=\frac{\alpha I_E}{(e^{\frac{v_{ID}}{V_T}}+1)}$$

also

$$I_E=\frac{1}{\alpha}(i_{C1}+i_{C1}e^{-\frac{v_{ID}}{V_T}})$$
$$=\frac{i_{C1}}{\alpha}(e^{-\frac{v_{ID}}{V_T}}+1)$$
$$i_{C1}=\frac{\alpha I_E}{(e^{-\frac{v_{ID}}{V_T}}+1)}$$

My question is: How do I analyse \$ Q_3 \$.


texts:
I want to implement load balancing for my car charger using my own system, running on a small server in my house. The EV charger has an API to set the max loading current, and I can get the overall power usage of the house from the P1 port of my smart meter. If the load is too high (if it exeeds 25A on any of the 3 phases), I want to decrease the charging current.
Question: what is a good algorithm here? Will my circuit breakers break if the current is more than 25A even for a tiny amount of time? Should I make sure I never use more than, say, 80% of the power?


texts:
I have an application where a cycling peak load from a 40hp motor is regularly tripping a 65Kw genset. Here are the details of the configuration:

65Kw Genset powered by a natural gas engine
40hp pump jack motor is the primary load
the peak load cycles from 100% load to 0% load in 5-6 second, then back to 100%
There are a few auxiliary loads being added, such as heat tracking and lighting.
There is a VFD in line between the generator and motor.

When the load initiates it goes to 100% immediately, continues for 3-5 seconds, then dumps to 0% load ( actually due to a counterbalance system it tries to backfeed, a sink is used to prevent the backfeed to generator). This cycle has caused no problems previously at lower speeds, but at the current operating speed the cycles are too short for the engine controls to react and increase work to make up for the load changes. Slowing down the motor is not an option.

A similar situation we are/will encounter is where we have 3-5 motors under the same load circumstances running at one site, though the loads are not synced, they are all at different cycle speeds meaning eventually the peak load across all motors will sync, likely resulting in a generator trip.

To help determine solutions I'll rule out the following possibilities:

Simply increasing power supply is a tough sell, although ideal for my interests I would need to be able to prove absolutely it is the only option.
We have no control over what speeds the motors are operated at.
Our genset sizes are calculated by our customer and requested as such, they are very stubborn and confident in their calculations.

We are performing full site load calcs in the coming days but this is a very time sensitive issue so I'm pulling on all my sources now, any help is greatly appreciated. There are two options I have come up with already but need further confirmation to act on either of them. They are:

Install a capacitor between the generator and VFD/Motor to act as a buffer, lowering the immediate draw on the generator as well as the immediate drop of load.
Install more or a larger genset, this requires absolute proof for the electrical engineers that they are wrong, likely more challenging then inventing my own superconductor.


texts:
I am using the NRF52832 and code it with arduino. I am reading A0 to get a signal from a sensor at 1m cable length.

simulate this circuit – Schematic created using CircuitLab

If I disconnect the sensor from the board, the analog input drop to zero. (Of course, the pull down is doing its job)

But once I connect the sensor, in the console, the analog input read 0,0,0,0,0 then 192 and come back to 0,0,0,0... (arduino analog signal goes from 0 to 1025)

What I have tried so far:

Add a 1pF capacitor in parallel of R1.. but not luck, it doesn't cancel the noise.
Change R1 value to 10kohm resistor but it appear to increase the noise
Adding a ferrite bead to the sensor cable (doesn't change anything)

I also tried this amplifier :

How can I avoid this noise ?


texts:
I am looking at this circuit which converts 5V to 13V, and am wondering how it is designed.

I have seen inductors being used in buck convertors, where a squre wave was used to convert and make it a low pass filter and allow only the DC.  But what is the inductor doing in this circuit


texts: I want to read 4 analog signals (coming from 4 pH sensor, generally said 16HZ freq.) With one buffer op-amp circuit going into a single ADC channel. Is it possible to achieve this using analog MUX ICs? Im asking because I'm not sure if the MUX will distort the analog signals. If yes, what other IC's can you recommend that is able to take 100 samples per second for each channel?


texts: SPICE circuit to find AOL and noise gain of Transimpedance amplifier

texts:
In Chapter 10 of Art Kay's book "Operational Amplifier Noise", he gives a SPICE circuit (pp.179) that can be used to generate the noise gain, AOL, and current-to-voltage gain.

Could anyone explain to me why put the source VG1 in the way shown in the picture, and why not at the non-inverting input side.

And, also, the book writes "Note that the 1-TH inductor is used to break the feedback loop from an AC perspective but allow for a DC connection. The 1-TF capacitor allows the signal source VG1 for AC coupling into the loop at extremely low frequencies." Could anyone give more details about these two lines?

I would greatly appreciate it if you kindly give me some references.

Thank you very much.


texts:
Hello all,
I have this circuit which will take an input (4x1.5AA (3.5V~6.2V)) and output a boosted voltage of 12V (120mA).
The problem I am facing is that the voltage takes about 10s. to build up from a dead start condition.During this time the battery voltage falls to about 1.8~2V and then recovers to about 0.5V less than open battery voltage,once the o/p voltage has reached 12V.After this the circuit works pretty fine.
I procured a similar circuit from here.The problem is similar with this, though less (maybe about 4 seconds,battery voltage drops to 2~2.2V).
Any suggestions on how to improve this?
TIA.


texts: How to install an embedded GPS patch antenna

texts:
How should I install an embedded GPS antenna?
Here is the antenna in question:
the antenna http://www.robotshop.com/media/catalog/product/cache/7/image/800x800/9df78eab33525d08d6e5fb8d27136e95/s/e/seeedstudio-embedded-gps-antenna-for-gps-bee.jpg
http://www.robotshop.com/ca/en/seeedstudio-embedded-gps-antenna-for-gps-bee.html
It has a 9 cm cable.
My project box (which contains a gsm shield, microcontroller, custom proto circuit board, motor h-bridge, lipo battery, and charging circuit) is an outdoor grey PVC junction box (like the kind used on hot tubs).  It is just big enough to fit all the components inside.
It looks kinda like this, but more of a cube:

(source: cesco.com)
Right now I just have the antenna loosely held in place by the mess of wires, and it is taking about 40 seconds from cold start to establish a fix, which is usually about 30-100 m off.
So, do I need to somehow mount the antenna to the wall of the project box, facing up?  If so, do I just drill out a small hole in the side of the box and epoxy the antenna to the wall such that nub on top is 'looking' through the hole?