texts: VCO for synth V/Octave and battery supply?

texts:
It's been a dream of mine to build an analogue synthesizer for a few years.

In this time I've built VCOs based on the 555 timer, which I know do not generally have an accurate frequency response without a lot of additional circuitry.

555 VCO

I've also built a VCO based on the LM358 op-amp. This seems to sound better and be more stable.

358 VCO

A lot of VCO designs I've found on the internet are quite complicated to build and require the +-12v power supply. Here's an example of one designed to run on two 9v batteries inverted.

358 V/Hz VCO

What I'm looking for is a simple design, not a huge amount of components, V/Octave  frequency response and powerable by DC from a battery(or two) (with an audio frequency range somewhere between 20Hz-12.5kHz).

I'm also considering the DCO approach, the Juno method of using a programmable divider to attain a frequency from a master clock seems very attractive.


texts: What are the disadvantages of using a diode to drop Vcc by a fixed amount?

texts:
Many circuits nowadays accept only 3.3 V as input voltage, maximum 3.6 V, but they can work often down to 2.7 V.

Since Lithium batteries (LiPo and LiIon) provide 4.2-3.3 V when charged-discharged (not completely, but substantially), a diode could be used to drop the supply by a relatively constant 0.55-0.7 V (depending on current rating of the diode and current circulating) to obtain (for 0.6 V) 3.6-2.7 V.

A capacitor has to be connected after the diode to reduce noise and current peaks.

Provided that the final device accepts 3.6-2.7 V, what are the disadvantages of this solution?

The advantages are minor cost, simpler connections, no quiescent current of a (linear) regulator.

In my specific case I'm thinking about a ESP8266 powered by a 18650 Li-Ion battery: in deep sleep the quiescent current of the regulator (2-3 uA) is significant compared to the chip itself (20-30 uA). A more compact setup is also a good advantage.


texts: Advantages on using a function generator against a multi-pulse generator by using a 555

texts:
I have designed a noise and interference reduction block. When I was going to test it by mounting the system in the lab, my professor told me that I could test it by creating a source of 50Hz by using a 555 in astable mode, instead of using the function generator as I was going to attempt.

After that, I was thinking what could be the advantages or disadvantages of testing that, with the function generator and with the multi-pulse generator. It took me a good deal of time to design the source with the 555, since it was unknown to me at that point.

So, I'd like to know the advantages and disadvantages of using both methods, to understand what was the point of using the multi-pulse generator with the 555.


texts:
I have a USBee AX Pro logic analyser

with 8 digital inputs accepting 0 to 5v.

I also have a bpt perla intercom.

It's working with a 2 wires bus (only 2 wires between outdoor and indoor panels) used for power and voice/command.
So on the indoor device, only 2 connectors.

On idle there is a 18v voltage.

Now i'd like to use my logic analyser to find the 'pattern' sent when I press the unlock door button.  But in that state it is not possible because the usbee works with 5v and the intercom with 18v.

What can I do for having it working ?  A resistance, a voltage regulator, ... ?


texts: Why should the output impedance of a current source be much greater than the input impedance of the load?

texts:
For a voltage source (except RF circuits), the output impedance of the source signal being coupled must be much smaller than the input impedance of the load. This is first of all done to prevent loading. Also even better to set Zin>>Zout to prevent the voltage divider non-linearity effects.

But why is that the other way around when it comes to a current source?

Why should Zout>>Zin? What is the logic behind it?


texts:
Now that the music festivals are getting closer this summer, I thought I would build some low-power dancefloor lights for my camp. The circuit I've found is really simple, but unfortunately I am not an expert on the field.

The driver will accept 12V as the main current for the circuit, except the control input will be 5V from a microcontroller. The FET/BJT will make the circuit always run at a specific amount of current, depending on the value of R1.

Once i'm building the shown circuit on a breadboard, it seems to work pretty okay, however when I solder it to the PCB's I have strange behaviour:

At first, the FET is open for current flowing through it, even if there's 0V on the gate. How can that even be possible? Also, the current is not limited at all!

After a while (~an hour with too much current! I suspect the FET has been very hot) it starts to work as intended, and limits the current to what I calculated. However if I put the control signal to ground, it will not be able to completely shutdown the current flow, resulting in weak but clearly visible light from the LED's.

I really cannot figure this out. Temperature (afterwards) doesn't seem to affect anything. I've built 4 of these units now, since I though i had a loose connection somewhere, but I start thinking that isn't the issue anymore.

Any thoughts?

(I'm running 25mA through each chain of LED's, i.e. 100mA in total. The voltage drop across each LED is ~3.2V (green LED's). R1 is 5R6 and R2 is 10k)


texts:
I would like to confirm that I am going about this exercise the right way.

"After a long time of being open the switch closes at t=0. Find $_L(s) and i_L(t)." (See picture below)

Do I need to take any initial conditions into account? There are none given, but as stated, the circuit has been on for a long time. Can the initial current be written as simply V_s/2R?

What I did was sum the voltages together V_S(t) = i_LR + Ldi/dt, then I took the Laplace transform and got I(s) = V(s)/L*1/(s + R) and from that I got i_L(t) = V_s(t)/L*e^(-Rt)


texts: Attiny84 has a slow rising and falling edges

texts:
I'm using an Attiny84 to generate 100us pulses for a totem pole gate driver. I was expecting rise and fall times in the order of 10's of nanoseconds, what I got was rise times of 7.8us (10% to 90%) and a fall times of 230us. To rule out any parasitic capacitance or odd ground loops on my board, I stuck the uC on a breadboard with just the scope probe hooked up to the pin generating the 100us pulses with the same problem occurring. There are decoupling caps across the rails.

The scope probe attenuation is 1X, 1Mohm/20pF input load.

I'm using pin 11 for the pulse generation.

Things I already tried:

 - Tried another Attiny84 IC to rule out defective chip
 - Different loads. Placing a 100kΩ pull down decreases fall times
   somewhat, but the signal only plateus to 4V instead of 5V. Placing a 10k
   resistor makes the signal entirely disappear.
 - Tried different pins, same problem.
 - Scoped 50ns rise and fall times on a completely unrelated board to rule
   out the scope as being defective.

Source code:

int main(void)
{
    DDRA &= (1<<PA2);//set pin  as output 11

    while(1){
        PORTA |= (1<<PA2); //set pin 11 high
        _delay_us(100);
        PORTA &= ~(1<<PA2);//set pin 11 low
        _delay_ms(100);
    }

    return 0;
}

Attiny84 Datasheet: link

Am I expecting too much from the chip? The datasheet provides a minimal amount of information about the I/O pins on pg 174.

Edit:
Whoops, what an embarrassing mistake. Bruce Abbott's answer is correct. Thanks.


texts: How can I transform the code for a read-write register to a read only register in Verilog?

texts:
I have the code for read write register here

module read_write(
input             clk     ,
input             rst_n   ,
input      [31:0] data_in , //data to be written
input             rw      , //rw=1->write to data_out; otherwise, read from data_out
output reg [31:0] data_out
);

always @(posedge clk or negedge rst_n) begin
if(~rst_n)
  data_out<=0;
else begin
  if (rw)               //write to data_out
    data_out<=data_in;
end
end
endmodule

How can I read data from a register? I am a bit confused, if I don't write the data to the register, how can I read something from the register?


texts: DALI Multi-Master: How to design a multi-master system? Is it part of DALI standard?

texts:
This question is haunting me for a long time. This could be something very basic and I do not know how it works or could be some misunderstanding! I am now using STM32E407 as DALI master and am working on the implementation of DALI. I have achieved some basic results on single Master- single Slave, now I want to look at the problems involved in multi-master DALI.

My understanding/misunderstanding:

My idea is to design a light control system with at least 3 DALI buses and if possible with a (1-10v) controller!

On single MCU, if I use different timers and GPIO pins to run different DALI buses and use two non-terminating loops in while(1) loop(or main loop), it will not obviously work as parallel processing is not possible on single core MCUs!

So, my immediate idea is to go for a modular approach, where each MCU will be implemented and running with DALI stack, providing just one DALI bus and I can use several of these to implement several buses.
To do something as shown below is my idea.

This obviously makes it more expensive and also for UI, Light_Controller MCU has  to access the data from and write data to DALIx_MCUs which leaves the Light_Controller MCU extra processing overhead or unnecessary extra effort!

I have checked for WAGO Multi-master module (commercial product). It's documentation, WAGO Multi-master doc, on page number 25, it shows the clamp as below.

I am guessing the "Logic" here is a small MCU or MPU and WAGO is using modular approach that is why each clamp provides one DALI bus!

Question:

I would like to know how multiple DALI buses or Multi-master systems will be developed in general?

and is it something that is part of DALI standard??

PS:

MCU- Micro-controller Unit, MPU- Micro-processor unit, UI - User Interface
I am not sure whether "multi-master system" and "single MCU with several DALI buses"(if at all possible!!) are same or not!
1-10v Controller can be part of the Light_Controller MCU and could be irrelevant here!


texts: How does a 700W PSU deliver so much power when most wall sockets are limited to about 20 amps?

texts:
I will be using a computer power supply to power a car audio amp for a project. The amp is 500w and my PSU is 750w. I never considered it until now, but how does the PSU deliver this? P=VI so 750w=12VI(internal lines are 12V,5V,3.3V and the 12V will be used to run the amp). So I=62.5A. This obviously can't be drawn from a regular outlet.

So I'm guessing that I'm doing this calculation on the wrong side of the PSU. In this case 750=110*I so, I=6.81A. A much more reasonable draw.

Is this correct?


texts: Regulation of transformer with inductive load

texts:
The regulation of transformer and alternators is poor while supplying inductive loads like a motor as compared to resistive loads.

Why is it so?

I do understand the phasor analysis of these loads and desire to know the physical reason behind the poor regulation of lagging loads.


texts: Why does my Oscilloscope measure a different voltage when I change the vertical adjustment?

texts:
I measured a 5V DC voltage from a lab bench power supply. The probe is a 10x which I properly compensated and the scope was calibrated prior to the measurement. I just forced the trigger to get a reading, but when I had it in AUTO and with a larger timebase the AVG was the same. The ONLY difference between the two measurements is the vertical adjustment. Why would I get such a different reading? Also I double checked the voltage with a multimeter and I got 5 volts exactly. My readings were the same with a properly compensated 1x probe.
First reading:

Second reading:


texts:
I've read a couple of application notes where it is stated that measuring current to use that value in the feedback loop helps stability because sensing before the RC net takes a pole away (see http://cds.linear.com/docs/en/application-note/AN140fa.pdf page 11, figure 13). I get that. What I don't understand completely is how do you know which current value you need to have if you only know the voltage value you what to stabilize at the output but you don't know how much you are loading the SMPS.

Thanks for your answers


texts:
I have a stdcell library which has “.v” file which contains all Verilog RTL models for stdcells. This stdcell library also has a “.lib” and ".db" timing files with all the delay information for these verilog stdcells. This ".lib/.db" files have been provided to me by stdcell IP vendor.

I want to run AMS simulation in Cadence Virtuoso environment. However I can't use ".lib" file directly for timing and need to convert it to a SDF format in order to use it inside Cadence ADE.

Does anyone know how can I convert this “.lib” timing file into SDF format using Synopsys primetime or other synopsys tools? (we use synopsys flow for digital).
I'm only interested in IO path delays in SDF file and I want to generate SDF data by cellname where all instances in design will have same delay.

I took a look at primetime user guide but I couldn't find any section where this process is documented.

Thanks in advance.


texts: How to maximize microcontroller temperature?

texts:
I need to test how hot a specific microcontroller can get in different situations. The goal is to have the microcontroller heat up as much as possible just by using it.

I was thinking I'd need to

make the microcontroller calculate something very expensive, maybe the factorial of a million or something like that.
maximize load on output pins (without exceeding specifications of the controller). Maybe just simple resistors connected to ground?

Does this work? Is there anything else I need to consider in order to maximize the temperature? Thank you!


texts:
I'm trying to enter on the command mode on this board http://iteadstudio.com/store/images/produce/Platform/ArduinoCom/IteaduinoBT/iteaduinoBT_DS.pdf.

It is a bad-documented, no support Arduino BT clone. I would like to send some AT commands, but Its not working.

Just to make sure that i'm not doing something wrong, i would like to double check the jumpers configuration. As you can see in the Datasheet lnked above, we have two positions for the jumpers (in a 6 pins set, it confuses me already, because with 6 pins, we should have 3 combinations, and not 2 as described)

So from the picture attached which are the A,B and C(?!): red: A, yellow: B?

EDIT

From the data sheet:

a jumper to set the connections of HC-05. When the jumper is set in B, the HC-05 communicates to FT232R, when the jumper is set to A, the HC-05 communicates to Atmega328P(board).

I was just able to enter in the command mode, setting the SWITCH to CMD, Jumpers at A (as cited in the accepted answer) and connected via USB, 38400. It means: the data sheet is wrong, it inverted the operations between jumpers A and B, right? AFAIK the communication HC-05 - FT232R is the serial communication that I used between my computer and the HC05 via cable and not bt, right?


texts: How to charge an android device with a buck converter

texts:
I've got a male micro USB connector like this one

I'm feeding the output of a buck converter set at 5V to pin 1 positive and pin 5 negative. Remaining pins are not connected. When I plug the connector in, the screen turns black and only the back and menu (or whatever it is) buttons are still lit but do nothing. After disconnecting the cable the phone remains like this for ~15 minutes and resets to normal.
If I plug in an ordinary charger the phone charges without a problem.
I have not done anything to the phone it's a stock android device.
It probably expects something on the not connected pins? I found that some chargers may put resistance between the data pins to indicate available current rate but is not standard so it should not be mandatory..
What do I need to do so I can charge the phone with the minimum 500mA?
EDIT:
I shorted the data pins as per USB 2 standard for a dedicated charging port and the screen phenomenon now happens only every other try.
After connecting, switching the power supply on and off does not cause the freeze but when off current is drawn from the phone.
Increasing the voltage to 5.25V resulted in ~125mA flowing to the device but without any indication of charging on the screen.


texts: What do the abbreviations "SPF" and "SPH" mean with respect to fuses? (Single line drawing for 480 V system.)

texts:
There are two lines connected between the transformer low voltage side and the 480 V bus, one with a fuse labeled "SPF" that connects to a GE power quality meter, another with a fuse labeled "SPH" that connects to a single winding of a transformer.

In the context of fuses, what does SPF stand for? It looks like could potentially be single-pole fuse or single pole fixed. I have no idea what SPH stands for.

Any ideas?


texts: Why dc component I must flow entirely through the load resistance R in buck converter?

texts:
The excerpt below is from Fundamentals of Power Electronics by by Dragan Maksimović and Robert Warren Erickson.
Can anyone explain the why question in the yellow part below? Why dc component I must flow entirely through the load resistance R?


texts:
How are amplifier output power ratings measured?

Can I measure the output power with a watt-meter or oscilloscope directly?

Can I measure the output impedance and then apply a Kirchhoff law?

I have done a lot of search about this subject and I found one important guide here:

www.ti.com/lit/an/sloa068/sloa068.pdf

But I still wonder, is the use of an analyzer the only method?

I also found this:

  a 2000 watts per channel amplifier tested with a burst signal delivers a continuous power output of approximately 650 watts (1/3 load) or 250 watts (1/8 load).

https://www.bittner-audio.com/en/information/measuring-amplifier-power/

and then I found this circuit

http://www.learnabout-electronics.org/Amplifiers/amplifiers23.php

to find the output impedance. But I still need the help from an experimenter who really does it.


texts: A question about understanding a BJT differential amplifier?

texts:
I'm trying to understand how a differential amplifier rejects common mode noise and amplifies the differential/normal mode noise.

For that I use the following circuit topology and simulation:

When Vin+ and Vin- are differential Vout increases as follows:

When Vin+ and Vin- are same Vout doesn't move much as below:

In case of common mode inputs, the increase in Vout is less than the increase in Vin. So common mode voltages get attenuated or we can say the gain is negative.

In case of differential inputs however, the increase in Vout is much more than the increase in Vin. So differential mode voltages are amplified. Hence means positive gain.

I can see these as a result in simulations.

But I don't know what causes this logically. I mean current source is causing all of these but how? Why common mode inputs cause almost no difference in Vout but differential mode voltages have big gain? Is there a way to tell what is going on in this circuit in transistor level by a step by step manner to explain why are the results are like these?


texts: Does BAFO "BF-810 USB to Serial Adapter (DB9)" supports full serial port?

texts:
Does BAFO BF-810 USB to Serial Adapter (DB9) support full serial port (hardware flow control) functionality?

If not, how can I test full serial port functionality using serial port only with TX, RX?


texts: Mosfet push pull not driving inductive load as expected

texts:
I'm building a magnetic levitation analog circuit.
I realize there's a handful of ways to do this and I came up
with my own idea ( which is partly why is doesn't work ... ) and
would like to continue exploring this idea even if later it isn't
as stable as other designs.

The setup is a IR LED and photodiode ( setup reverse bias ), that goes to
an inverting amp ( IC OP07 what i had..), which then heads off to a push pull
mosfet driver ( IRF 510 and IRF 9510 ).

My electro magnet is about 50 ohms wrapped around a pipe with ferrites in it.
I added a lot of ferrite which I regret since the field doesn't change directions very fast.

I skipped the differentiator ( would like to try later ).

Power supplies are +15 and -15 VDC, with current limiting on the -15 since it's a wall wart. The positive supply, is good up to 10 A, it's a beast.

The gates are getting appropriate pos and neg voltages. And, with a pure resistive load ( 75 Ohm ) , the current drawn is what I'd expect.
However, when the coil is connected, only the P channel mosfet draws current.

I'm wondering if the inductance of the coil is in causing this ?

UPDATE:
I didn't include the IR LED in the diagram. It runs off the 15 V rail with a 1K.
I have -0.03 V on my meter, when I check the ground. I have assumed this was from the photodiode. That's why I put the small ref volt on the OP1'a pos input.

On my meter, I do see a +15 to -15 V swing on the output of OP1, as I block and unblock the photodiode.

Updated schematic fixed per gsills comments.


texts: Is it sufficient to disconnect the negative terminal of a voltage source?

texts:
I have a scenario where I would like to use N-channel MOSFETs, because they have lower on-resistance and are cheaper.

simulate this circuit – Schematic created using CircuitLab

Would there be any problems with this approach?

I've read this answer but I understand the main concern is somehow accidentally forming a closed loop. But if the MOSFET is safely at the negative terminal of each voltage source, I don't see how there would be any risk?

Am I correct that the positive terminal of either voltage source cannot conduct until the negative terminal is also connected? In effect, as if it wasn't connected at all?


texts: How to dim an LED with constant current supply?

texts:
I have a power RGB led with 350 mA max per color. If I get 3x 300-350 mA constant power supplies will I be able to dim each individual color from 0 to 100% power with Arduino (with NPN transistors)?

I am a bit confused since constant current psu's are the best way to power led's but since they provide constant current can they be dimmed with pwm as one would expect with any power supply?

I am thinking of this PSU.


texts:
I'm using the following input stage for an audio application:

The audio signal is analog and single ended. The connector side is exposed, so a person could touch it. The TVS should protect the circuit from ESD. The C10 is a DC coupling capacitor and the other components are used to filter out GSM noise. The amplifier is a 2W class D audio amplifier.

The problem is that in certain situations, when a person touches the connector, a DC voltage is induced on the connector side of the C10 capacitor, which causes a whistling sound, although the only thing I can measure on the audio line is a DC voltage (no sinus-like wave).

The blue line in the following image shows the induced voltage on the connector side of C10. The sound fades out after about 60 seconds.

My question is: is there a way to prevent this or to discharge the capacitor quickly? Alternatively, why is the whistling sound there and can I prevent it?

EDIT:
For the sake of completion: I use the following parts now and touching the connector pins doesn't generate noise anymore.


texts: Noise problem on input of an analog to digital converter

texts:
I just finished building and testing a board using an LTC2440 24Bit analog to digital converter.

It functions, but there is a noise problem that I don't understand.  The signal I am trying to digitize is very clean (for what I need.)  When I connect it to the LTC2440, however, I get a very large amount of noise.  It seems to come from the LTC2440 itself, although the noise on the input is larger than the noise on the 5V supply to the LTC2440.

What I am trying to measure is a slowly changing DC from the MAX2015.  I need the DC voltage accurate to 0.00001 or better.  The voltage represents the level of 13GHz RF received by a satellite dish LNB.  Right now, the circuit far outperforms the original solution I had that used a SatFinder to provide the level reading voltage.

I expect to have to improve the circuit and layout in order to get the performance that the LTC2440 is capable of.  This question is NOT about that, though.  Here I am only trying to find the cause of the enormous peaks that you can see below in the picture labeled "Noise on LTC2440 Input."

Information:

Schematic:

Noise on LTC2440 Input (pin 5):

Signal (Output from U5 MCP6231 pin 6, when disconnected from LTC2440 pin 5):

This picture doesn't do the real signal justice.  The camera has a problem capturing the trace.  If it is bright enough to be sharp, the camera captures the glare around it.  If the trace is dim enough that the camera doesn't capture the glare, then it also doesn't capture the trace.  In reality, the trace is a razor thin line with small, slow, excursions.  If you look closely, there is a thin, almost white line down the middle of the fuzz.  That's the signal.  The rest fuzzy from the glare.  Even so, that is a small fraction of 1mVolt as compared to the approx. 10mV peaks in the noise picture above.

The MCP6231 was added during testing because I found that the MAX2015 puts out a lot more noise than I expected.  The simple RC filter clears that up, but doesn't make the glitches go away.

5Volt to LTC2440:

3.3Volt to MCP6231:


texts: Controlling a circular magnetic field with microcontroller

texts:
I have this idea for a project and I'm looking for some direction.  There is a "clock" in a recent tv show that I want to recreate.   See this image , or This imageIf you're familiar with Westworld you'll know it.

I started looking at magnetic sand and then at ferrofluid.  Ferrofluid seems to give the effect that I'm looking for but I have no idea where/what to even begin looking at.

To me I see a circular electromagnet, the field could be altered to give the desired affect with the ferrofluid.

So at stasis there would be a stable field and it would look like the first image.  It could dynamically shift to look similar to the second image.

My question is where do I start here?  Googling for "control circular magnetic field with arduino" didn't net me much.  Most were create a electromagnet with a relay etc.

Would I need to control one large field, multiple smaller ones?

I don't mean for this to be vague, as I said, I'm not sure where to even start here.  Maybe this isn't possible.


texts: Help with powering LED strips from a LED TV

texts:
I have two LED stips salvaged from a LED TV.
I only have these to LED strips and the ribbon cable that was connected to them from the TVs screen and not other PCB boards or components to help power the LEDs.

I would appreciate if someone can help me figure out how to power these two LED strips. I have very little electrical experience. Most Google searches for Led strip calculation are based on the length of a strip, but these are not the normal led strips from a roll.

The LED stips have various codes printed on them, but the code CL-550-072-V1-L and Google pointed me to this page whith what is seems the exact same model:
https://eastern-star.en.made-in-china.com/product/UXyxNGmKYMYf/China-Es-Eled-063-Cl-5500-72V1-R-L-Eled-TV-Backlight-Use-for-Phi-Lips-Cl-55-Inch.html

From that page I gather:

Power:       0.5W/LED
Voltage: 3V/LED LED
Quantity:    Rigth:72 LEDs Left:72 LEDs

I could not find information if the LEDs are in series or parallel.

Here is an image of the power connector on one of the LED strips:
https://imgur.com/Jrz7pz4

Not the best picture. But each connector has only 1 row of connectors. The connector has a single connector with a pair of (+) and (-) on the strip, and an un-used connector in the center (the cable has no wire there). Additionally what looks like single (+) and (-) exposed for soldering?.

Questions:

Does that mean each LED needs 0,17 Amps (0.5 Watts / 3 Volts)?
How do I calculate the power requirements for the whole strip or both strips?
Any recommended power supply / driver that supports dimming?

Update

I borrowed a multi meter and measured the continuity of the strip. It seems that a single strip of 72 leds are wired in 4 series sets of 18 Leds each. There was continuity between diodes 01 - 19 - 55 - 72.

Could that mean that my required power supply should be the following?

Volts
18 Leds * 3 V = 54 V

Watts
72 + 72 Leds * 0.5 W = 72 W
+ 20% overhead = 90 W

Amps
90 W / 54 V = 1.66 A


texts: Why is my transistor beta lower than expected?

texts:
I bought these transistors on digikey: BC549CTA

Reading through the datasheet, (and on digikey's page), I am led to believe that the DC gain for this transistor is at minimum 420 [@ 2mA, 5V]. The actual range is actually like 420 - 800 or something.

Anyway, I was trying to build a current source for a differential pair and wanted to pump out about 2mA of current through the transistor, so I set it up like this for a quick test:

I want to put the emitter at about 1V, so at 1V / 2 mA gives 500 Ohms, I went with 470 Ohms as the closest value I have. That ought to put the emitter at 940 mV.

To bias the transistor, I multiplied the emitter resistance by beta (assumed 600) and divided by 10 as a rule of thumb. This means I'll have to aim for a base resistance of about 28k and a base voltage of about 1.5-1.6

The divider above should work out to a Thevenin Equivalent of about 28.7k, pretty dang close.

After the quick sketch, I built the thing and to my surprise my design did not work out at all. The emitter voltage worked out to be 447 mV. That's way below what I expected. I expected to be at least somewhat close to a volt, but this is less than half. The base is the same way, about 1.05 V. Needless to say, I'm definitely not getting 2mA from this source.

I've built a few more circuits with different values. I tried to reduce the total base resistance to reduce the loading effect, but that made it worse. Eventually, I tried to work out the beta value backwards, and it looks like the transistor has a real beta value of about 43-44, not even close to the claimed 420-800. So, with that, the expected resistance looking into the base is about 20k. I worked out values of 18k for R1 and 2.8k for R2 (bias resistance of about 2.42k). This time, the values agree! The emitter voltage is about 940 mV, and the base voltage is about 1.54 V.

What gives guys? I thought maybe the spec for the transistor drifts a lot when it's outside of the measured conditions (5V @ 2mA Ic), but I used a 5V supply as well and the results are the same. I'm really confused.

For those old designs, the ones I initially thought should work, I duplicated the same circuit with my old 2N3904s, and the values were right on the money. I really cannot figure out what I'm doing wrong here.


texts: Is most of non-isolated power supply "safe"?

texts:
I need a large power supply (a little over 1kW) for a consumer appliance that only has a single on/off switch and some non-conductive handles.  An off-the-shelf isolated supplies run at least $60 for a sketchy Chinese supply that only supports either US or EU mains, whereas I could probably produce something similar to the following schematic for <$20 that would support both US and EU mains:

A lot of the cost savings would just be because I can afford to run the supply "dirtier" (higher ripple current) on input bulk capacitor(s).  Even the output can be somewhat dirty, but I would plan to clean it up by using "smart" switching on the input to the buck converter.
However, safety is a concern.  While from what I could tell from regulations there is no requirement that the power be isolated for my application, I would feel pretty bad (not to mention the financial ramifications) if someone got hurt somehow using a non-isolated design (e.g. got water into it and got shocked, if that's even possible).  However, it seems like only a small portion of a non-isolated circuit is actually dangerous.  As annotated in the schematic, is it true that mains is only dangerous to the extent that high voltages are involved, and that stepped-down but non-isolated voltages later in the circuit are "safe"?
Also note: I would plan to earth ground the metal case of the device (such that a short to live, and potentially neutral, would blow a fuse).  And also, I would definitely have whatever final design I came up with reviewed by some experts; I'm just wondering if this is a plausible direction, given that using an isolated supply would probably make the product economically infeasible.

Edit: I'm going for 48V and actually closer to 1.2kW.
Sorry for not clarifying, but that ground symbol was not meant to mean that the circuit was connected to Earth (which would short the bridge), but rather just something I placed as required by the simulation software.  The output side would be disconnected from any of L/N/G prongs, which I guess could cause some common mode voltage swing.  However, the metal case would be earth grounded (and isolated from the rest of the circuit).  Then if the live or the ground reference of the output side connected to the case the fuse would blow, but I guess if the pre-bridge neutral connected to the case, that may not be detected if there isn't an RCD (or I could add a low-rated fuse on the Earth ground path).


texts:
I'm working with a system that has a pair of plugs that I'm not familiar with. They appear to be Molex Mini Fit Jr. style connectors (such as those used to provide power for PCIe devices that require extra power), but in an 18-pin and 10-pin type that I'm not familiar with.

Not that that's surprising as I'm only familiar with a handful of molex connectors, but I'm hoping someone can help me identify an exact part number so I know what I'm looking for. I've tried searching from the Molex web-site but it's not the most user-friendly and I couldn't seem to open documents for half of the possible matches.

Here's an image of the (possible) Molex plugs. Any help in identifying whether they're a standard part (and appropriate part numbers) would be greatly appreciated. Also, if they exist in black then that'd be ideal (dunno if they'd be a different part number?).


texts: Design of synchronous buck converter: What's "ripple voltage"?

texts:
I am designing a synchronous buck converter for variable input from 12 to 36 V and output fixed at 14.4 V. The power is 400 W and switching frequency is 50 kHz.

While designing I came across 2 terms. One is ripple current that I kept 35% of rated current. The second is ripple voltage and I do not know what value to select to find the capacitance.

So want to know what ripple voltage is and what value should I select to find the capacitance?


texts:
When I turn on/off buzzer via D17 using my Ardunio nano board, the two Leds RED and AMBER turn on/off too. I don't want this occur but don't know how to do this. Can anyone can help to show me what root cause make the Leds turn on?

Buzzer characters: Large Piezo Transducer

·  Rated Frequency: 3,500Hz
·  Rated Voltage: 4 - 28 Vdc (DC input)
·  Current Consumption: 6mA @ 12Vdc
·  Sound Pressure Level(30cm): 87dB @ 12Vdc
·  Flying Leads Fitted
·  Kingstate Buzzer - KPEG253
·  Dimensions: 28mm Diameter, 25.4mm High, 33.5mm between


texts: Unexpected results in voltage to current converter (simulation is Ok)

texts:
The circuit below shows a Voltage to Current converter based on a DAC, opamp, transistor and switches. The last one, allow to have a bipolar signal output.

During the experimentation, the DAC is setup to get ~330mV in the resistor (330 ohm) at the transistor source in order to get 1mA current and the LOAD.
The circuit (except the DAC) is simulate (in multisim) with success.
The switches used during experimentation are based on MAX4623.

In the real world, there is an unexpected situation when the switch turn on (please, refer to the waveform below).

The waveforms of the LOAD (2.2K ohm) are shows in the scope chart (PIN+ and PIN-). Everything is as expected, except the part marked in red color.
The expected waveforms are show below. These waveform allow to have a bipolar current (+/-) in the load.

Any suggestion in order to understand the unexpected situation is appreciated. As well as an approach to avoided.
Edit:
As suggested by Tony, the voltage in the mosfet source has been reduced to ~110mV.

The results in this experiment change a little a show the waveforms below:

Edit:
As suggested by Spehro, a switch could be added to avoid the op-amp to saturate.

Below the proposal and expected signals.

Edit:
Below a proposal using a current mirror, following Tony and Spehro suggestions.

The waveform results improved with this proposal:

However, there are some not desired situations:

The left part of the mirror is always on, increasing the power consumption. Perhaps, a new question (based on this experimentation) will be: how to implement a ultra low power voltage-current converter (0 to 10mA)?
The initial peak (when the switch turn ON) is too high for the load. Please, refer to waveform below.

Edit (explain of unexpected situation):
As suggested, the unexpected situation is explained by the setting time of the op-amp. In summary, once the transistor turn on, the op-amp need time for adjustment (with the feedback). To solve this situation, the transistor is keep ON in order to allow the op-amp not saturated. One solution is presented in the proposal (see previous edit), where an additional transistor is added (making a mirror).
Thanks


texts:
I'm trying to design double-layered PCB audio DAC. At some point, I've started with "reverse" engineering best 80-90s Sony's CD players and found interesting thing, the "higher" player in hierarchy (more expensive, heavier, slightly better supply, etc), the less ground plane on the top layer.
CDP-228ESD -> CDP-338ESD -> CDP-X7ESD

As you can see on the last picture PCB is single-layered and it was "highest" their player (almost).
Initially, I planed to left the whole top layer for the ground plane (don't split digital/analog/power ground), but now I'm not that sure. And then I come across a Rick Hartley seminar on proper grounding (https://www.youtube.com/watch?v=ySuUZEjARPY&t=4405s) that he suggest to split the ground for <20KHz.
What strategy will be the best in my case:

Cut the ground plane after the middle of the DAC IC;
Cut the ground plane after the DAC IC;
Cut the ground plane after the I/V converter opamp;
Left whole top side for the ground plane?

UPDATE (schematic):
The pcb I want to design is a classic R-2R dac with op amp based I/V converter and third order low-pass filter with Sallen-Key topology. Basically,
WM8804 (spdif receiver) -> SM5847 (digital filter) -> PCM58 (dac) -> ad842 (I/V) -> LME49870 (LPF+buffer)


texts:
I have a lot of trouble running a prototype made up of two I2C modules, one of which is disabled at the beginning.

Here is the list of components:

Arduino Uno
LCD I2C module
Moisture sensor module (ads1115 + moisture sensor)

The moisture sensor module is swithed off by default to prevent oxydation of the sensor's electrode.

When the arduino starts, the current flowing in the SDA/SCL pins of the moisture sensor module creates a loop, and conflicts with the LCD module.

I can make it work if I remove the transistor, and connect the Vin pin of the moisture sensor directly to the arduino Vout

How can I make them work together? I guess I should use a diode somewhere, or use one or two more transistors to prevent current from entering SDDA/SCL pins...

simulate this circuit – Schematic created using CircuitLab


texts: What certification do you need to sell electronic device to US market?

texts:
Other than FCC and RoHS statement, what other certifications do you need to have in order to sell your product to US Market?

My device is a remote control using Bluetooth Module. Operate using 4 x AA battery .
The Bluetooth module is already certified with CE and FCC.

I was told I may need a Safety test. ETL if I'm not mistaken.


texts:
I have read the basics of antenna theory and lectures.
I just want some practical PCB antenna design & its calculations /design considerations so as to understand the design calculations better.
Any PCB antenna design regardless of the frequency of the operation and the size will do.
I searched a lot but unable to find one antenna design which showed me the design calculations and the steps.
Can anyone provide me a detailed example of any PCB antenna design that you have designed or any link which provides me what I am searching for?


texts: Common ground between a current source and a power supply

texts:
I want to design a simple circuitry for testing a bench top current source through a load resistor. I want to use MAX9611, and read data through I2C by a micro-controller. The rough circuit schematic I came up with is this:

As you can see, the current source comes to RS- pin and goes through r1 to the ground plane.

My problem is, the current source and the power supply for my micro controller and the current sense chip are two different units.  e.g. the VCC comes from a 9V wall adapter but the current I want to sense is through a bench top current source equipment.

I am wondering how can I have a common ground? can I just connect the two grounds together? if not, what should I do? Not to mention that I would like to have a clean ground so no noise affects the ADC inside the maxim chip.

Please let me know if I should provide more details


texts: Why is bipolar EMG better than monopolar at reducing (common mode) noises?

texts:
As defined in this post, the monopolar EMG can reduce the common mode noise by taking the difference of the two inputs, i.e. EMG_mono = k * (V1 - V2).
And, for bipolar mode,EMG_bi = k3 * [k1 * (V1 - Vref) - k2 * (V2 - Vref)].

To simplify the equations, we assume k1 = k2 = k3 = 1. Then monopolar is simplified as: EMG_mono = V1 - V2, and bipolar is simplified as EMG_bi = (V1 -Vref) - (V2 - Vref) = V1 -V2. That is to say the overall effect is the same for both monopolar and bipolar modes.

The question is:  why is bipolar better than monopolar at reducing (common mode) noises?


texts: Can you power a 3.3 led with an arduino 5v output?

texts:
I have a led that can handle 10 milliamps at 3.3v. Can I use a voltage divider and a plus resistor to power it from an arduino nano 5v digital pin?
Maybe something like this.

simulate this circuit – Schematic created using CircuitLab


texts:
I am new in the world of electronics and am having trouble understanding an example circuit found in the LM139 data sheet. I created the circuit on a breadboard and it does indeed work, but I am not understanding the current flow and WHY it works.

http://www.ti.com/lit/ds/symlink/lm2901-n.pdf
The circuit in question is figure 28(Limit comparator) on page 16 of the datasheet.

Since the output of the LM139 is an open collector, when both comparators are "HI"(the input signal is in between the non-inverting pin of comp 1 and the inverting pin of comp 2), would that not sink the current to ground by turning on the internal transistor and not allow the voltage source to activate the external transistor? Could someone walk through how this circuit behaves?

Thank you!


texts:
I've been asked to complete the following 5 bit Gray code:

I know how to generate a Gray code (create a mirror image, pad the original values with a 0 and the reflected part with a 1), but I'm not sure how to generate the Gray code when a portion of it has already been given to me. I can see that in the third row, the A column starts with a 1, so it probably reflects over the second row. Any hints on how I should approach the problem? Or am I not seeing something that I should be?


texts: Multiple statuses displayed in LEDs and piezo [sometimes]

texts:
Essentially [and this may sound a little overkill] I'd like to run current sensors from three sources to indicate whether electric or EM locks are engaged and to feed off of reed sensors to feed the status of doors being open or closed back to a small enclosure and matching an active electromagnetic lock back to the lighting of an LED marked as such and so on for each sensor or switch source.
Power would go 110v down to 12v 10amp to a screw terminal [unless that's stupid, in which case I'll do it some other way].
Could someone explain how to run the sensors/switches and LEDs without running each off a separate terminal for power and one LED per circuit? It seems like there must be an easier way to do it, but if there is I don't even know the name of it.


texts:
I am using 0402 nominally 10k\$\Omega\$ NTC thermistors that are soldered onto a flex PCB which is then adhered to the point of interest in an Alumina based thermal adhesive.

The thermistors have been working properly through temperature cycling from room temp to 85C many times over the past year. The points of interest are cooled by forced air when in use.

Suddenly, several of the thermistors have begun failing by reading a nominal resistance between 13k\$\Omega\$ and 17k\$\Omega\$ leading to obviously wrong temperature measurements across their use range. I removed the failed ones to look for visible cracking due to thermal shock, but I don't see anything.

After going through many avenues as to figure out what is causing this problem, I am still stumped.

I know all parts have a mean time before failure, but I am nowhere near that, and clearly something is expediting their failure time. There is no shock nor vibe in the system so what else causes thermistors to fail once installed and in use over time? Corrosion? Leakage paths in the thermal adhesive?


texts: What is the use of 5V pins on Raspberry Pi GPIO?

texts:
On a Raspberry Pi, GPIO pins are 3V3 tolerant. And there are two 3V3 pins that we can use to play with GPIO (driving LEDs or sensing Buttons). But what is the purpose of the two 5V pins?

edit: I am talking about the pins specified in this official webpage - https://www.raspberrypi.org/documentation/usage/gpio/


texts: Feed a "solar" charge controller from AC->DC power supply?

texts:
In considering a DIY UPS-ish system (small bank of AGM batteries and an inverter), I knew I wanted/needed a charge controller, but most I found were just intended for keeping e.g. car batteries topped off.

It has since occurred to me that "solar" charge controllers, of which small 10-30 amp versions are in abundance, run off DC input anyway.

Is there anything wrong with feeding any typical charge controller intended for solar panel input with mains power via an ordinary DC power supply like you'd find on, say, any amateur radio operator's desk? Any special considerations beyond making sure I don't feed the controller more voltage than it can handle?


texts:
I am working in a project with a fleet of several fishing boats.
I am measuring their locations with a GPS module and some other data with a set of sensors and a micro-controller. I would like to send this data in real-time over a radio frequency link to mainland.

Ships could be located far away, around 100-400km.
There is no GSM coverage.
Satellite link should not be used.

I have evaluated using Xbee modules, however they are limited to line of sight and power limitations.

I have read that working in the MF/HF band, long ranges may be reached, specially using skywave propagation, in which the wave reflects with ionosphere. However I can not find commercial OEM modules on this frequencies to integrate with a micro-controller.

Update:

Max distance for a ship from the coast is 80 nautical miles (148 km).

I was reading about sending digital data through VHF radios using APRS.
According to Wikipedia:

  Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time digital communications of information of immediate value in the local area. Data can include  GPS coordinates, weather station telemetry, text messages, announcements, queries, and other telemetry.

APRS uses 2m amateur band (142-148 MHz), which means that commercial amateur radios can be used after converting digital signals to audio tones by a Terminal Node Controller (TNC).

Do you think these distances can be achieved using APRS with handheld VHF radios?.


texts:
Could someone explain inexperienced VHDL coder what this error message trying to tell me in simple words? I found a similar question here, but here was no answer to it:

   ERROR:Place:1108 - A clock IOB / BUFGMUX clock component pair have been found
   that are not placed at an optimal clock IOB / BUFGMUX site pair. The clock
   IOB component <HREF> is placed at site <A4>. The corresponding BUFG component
   <HREF_IBUF_BUFG> is placed at site <BUFGMUX_X2Y3>. There is only a select set
   of IOBs that can use the fast path to the Clocker buffer, and they are not
   being used. You may want to analyze why this problem exists and correct it.
   If this sub optimal condition is acceptable for this design, you may use the
   CLOCK_DEDICATED_ROUTE constraint in the .ucf file to demote this message to a
   WARNING and allow your design to continue. However, the use of this override
   is highly discouraged as it may lead to very poor timing results. It is
   recommended that this error condition be corrected in the design. A list of
   all the COMP.PINs used in this clock placement rule is listed below. These
   examples can be used directly in the .ucf file to override this clock rule.
   < NET "HREF" CLOCK_DEDICATED_ROUTE = FALSE; >
   ERROR:Pack:1654 - The timing-driven placement phase encountered an error.

I just want to use external HREF signal as the trigger to count lines and for some other things. Is there a better way to configure logic? Here's what I have:

ENTITY mainModule IS
PORT(
    CLK160  :   IN  STD_LOGIC;
    BUFOUT  :   OUT STD_LOGIC_VECTOR (11 DOWNTO 0)  := (OTHERS => '0');
    RESET_B :   OUT STD_LOGIC                       := '1';
    HREF    :   IN  STD_LOGIC;
    DATA_IM :   IN  STD_LOGIC_VECTOR (9 DOWNTO 0);
    PCLK    :   IN  STD_LOGIC;
    XVCLK   :   OUT STD_LOGIC                       := '0');

END mainModule;

ARCHITECTURE BEHAVIORAL OF mainModule IS
    SIGNAL      CLK10       : STD_LOGIC     := '0';
    SIGNAL      SKIP        : STD_LOGIC     := '0';
    SIGNAL      LineCounter : UNSIGNED(9 DOWNTO 0)  := (OTHERS => '0');

    component CLK_DIV16 is  port (CLKIN : in STD_LOGIC; CLKDV : out STD_LOGIC );end component;

BEGIN
U1: CLK_DIV16 port map(CLKIN => CLK160,CLKDV => CLK10);

OUT_TEST: PROCESS(PCLK)
    BEGIN
        IF RISING_EDGE(PCLK) THEN
            BUFOUT(9 DOWNTO 0) <= DATA_IM(9 DOWNTO 0);
        ELSE NULL;
        END IF;
    END PROCESS OUT_TEST;

LINECOUNT: PROCESS (HREF)
    BEGIN
        IF RISING_EDGE(HREF) THEN
            IF  LineCounter > 488 THEN
                LineCounter <= (OTHERS => '0');
                SKIP <= NOT SKIP;
            ELSE    LineCounter <= LineCounter + 1;
            END IF;
        ELSE NULL;
        END IF;
    END PROCESS LINECOUNT;

BUFOUT(11)  <= PCLK AND HREF AND SKIP;
XVCLK           <= CLK10;

END Behavioral;


texts: What are some practical examples of a constant current source?

texts:
Please don't state the obvious that nothing is a perfect constant current source.  And please do not give examples of how to create them from components.

I looked at this SE Q/A which stated the obvious - that you can not have a perfect current source.

So when I say constant current source, I am not referring to the mathematical concept used in circuits, but "natural" components that provide a close approximation to this. Key word is approximation.

A bit of research pulled up one interesting example which was a solar cell.  Is this a valid example?

A google search pulls up a similar Quora question here. Which gave the example of a solar cell.

This is a more technical site and I was looking for a more engineering answer not a mathematical or laymen's answer.

Thanks.


texts: minimalist serial port addon to a basic 8052

texts:
Currently I have two microcontrollers connected to each other so that I have two serial ports. One to the PC and one to a wireless radio module.

Now I'm considering replacing one microcontroller with a hardware UART so that I can exchange parallel data to the PC. I'm avoiding parallel port because fewer PC's come with parallel ports.

I have a few questions:

Can I achieve 56kbps if I place this UART in synchronous mode?

Can I send a byte of data to the uart by applying data to the P1 line and pulsing WR low when a signal on the UART is in a ready state?

Can I receive a byte in a similar way (where I pulse RD low instead and receive contents on P1)?

Will I always need to receive and process data within a certain time limit especially if the PC decides to ignore any flow control in use by the UART?


texts: RS (NOR) flip flop stuck at undefined [Fixed]

texts:
I'm trying to make an asynchronic automata which outputs every other impulse (any amount of 1's) from input ( 0 in any other state).Heres states table:

Q1Q2\X  0   1   Y
00      00  01  0
01      11  01  0
11      11  10  0
10      00  10  1

My functions are:

R1=Q2'X'
S1=Q2X'
R2=Q1X
S2=XQ1'

Desiered output:

My output:

My scheme:

I've also tried usig NAND based RS and using only Q1Q2 functions. Both had same result as above.

Fixed

I need to force it into one of defined states (00) by adding additional inputs (a1..4). After that i set those inputs to vaules which won't interfere and it worked exactly as desinged. Hope that helps if anyone else has that problem.

Output:

Scheme:


texts: AM and FM reception with the same antenna

texts:
I'm designing a radio with the Si4735 chip to use in a car, and I want to use the existing FM antenna for both FM and AM reception. I'm not sure how to go about this, exactly.

How would I go about achieving this? The chip's reference schematic is as follows:

I assume I need to somehow match the impedance of the FM antenna to that what the chip expects from an AM antenna.

Any help in this is appreciated.


texts: sharing ground for serial connection Across raspberry Pi and Arduino both with different power supply

texts:
I do power the Raspberry via a 5V USB charger. The Arduino is soldered into a different circuit and is powered from a 24 V circuit via a 5V charge regulator. Both will be connected to the same 230 V power circuit. Is it safe to connect both serial grounds together ? Or is it possible to create a ground loop ? As far as I understood, both devices have to share common ground if serial connection should work (without optical isolation) ?

This is the circuit with the Arduino. The pins on the upper left are the output of the relais. The 6 head pin is made for the control over the relais card. It is essentially a controler for a  8 port valve (IMV-8, Pharmacia)


texts: How can I lower the chance of burning out capacitors?

texts:
I have an AC/DC power supply circuit fitted to many machines, which are all running well within the rated power capability of the supplies.
However these keep failing, every one burning out a (large) electrolytic capacitor (after say 1 years' service). Oddly these boards vary slightly, some have one cap, some 2, but invariably this is the part(s) that fails.

The boards with 1 cap are rated at 22µF 450v, and with 2 rated at 47µF 450v.

So, what can i do to take the stress off this component? run several in parallel?

UPDATE:
Having had a good look over the PSU's they are indeed weird! the motors in the machines (which are cardboard shredders) are rated at 220v DC! so the main "chunky" part of the PSU board is just a rectifier/filter cap (which is the bit burning out) with no transformer, and the rest is a smaller, separate step-down DC supply for things like lights, switching, protection etc.


texts:
casual beginner electronics hobbyist here.

I read an article online describing how to impedance match a resistive source impedance of 75 ohms to a resistive load impedance of 1k ohms. In order to accomplish this, the author of the article inserts what he calls an L-Network consisting of an inductor and a capacitor between the resistors as show below in “Image A”. He then goes on to explain how the circuit can be analyzed by taking the load resistor and capacitors and combining them into one as shown in “Image B”. The result of this combination can be seen in “Image C”.

The question is: Are both circuits (Image A and Image B) really the same in the real world? Would both circuits really provide the exact same output, performance etc?

Thanks.


texts: Any tips on using the Invensense ITG-3200 gyro?

texts:
I'm developing a gyro+accelerometer data logging device using the Invensense ITG3200 gyro device and I'm having a real struggle getting it to talk to me. I have tried 5 of them and none of them are responding to I2C commands. Has anyone had experience using these and had to overcome hurdles to make them work?

I have two other sensors on the same I2C bus and they are behaving as expected, so my I2C comms is working fine. The sole bus master is a PIC microcontroller. I have wired the chip up exactly as shown in the specs, and use a common 3.3V supply for Vdd and Vlogic. Pullup resistors are 4k7, but have tried reducing them to 1k5 with no effect.

The gyro chip is a bit odd electrically too - it is behaving as if it has a pullup on the SDA line to a voltage at 2/3 the supply voltage, but that ceases to supply current when the SDA voltage drops below about 0.6V. That behaviour kind of makes sense but is not documented in the spec sheet.

I am wondering if I have managed to damage all 5 chips in exactly the same way, but that seems unlikely. One of them I purchased on a breakout board and it behaves exactly the same as the others: 2 of those are reflow soldered onto a PCB, the other 2 I glued upside down and hand soldered fine wires to the pads (getting desperate there!).

It would be good to hear from anyone who has used this chip successfully - seems like a great device but I am getting a tad frustrated ;)

I did send a query to Invensense but haven't heard anything back from them.

Thanks for any clues.


texts: Microphone sensor for picking up voice from across the room

texts:
I'd like to create kind of a DIY Google Home using a Raspberry Pi and voice recognition software.

I'm looking for a microphone sensor that will pick up my voice from across the room, but nearly all of the microphones I've seen look something like this:

and are clearly designed to be close to someone's mouth/the sound source.
(Please correct me if I'm wrong.)

I've found a cheap condenser microphone that looks like this:

and would it work? Or am I looking at the wrong thing entirely?


texts: I would like an honest opinion about the PCB circuit I have designed

texts:
I made my own version of the VESC controller from the open source schematics. I'm a rookie at the rules for circuit traces but have read most of what is covered.

I do not know if I should make the inner copper layer of the same layer linked together because the MOSFETs will be fed 50V constant while the DRV8301 and MCU are fed their own voltage supply utilizing the buck converter on the DRV8301.

PCB is 4 layers.

Red is top copper layer supplying 50V,
yellow is inner copper layer 1,
purple is inner copper layer 2,
and green is the ground layer

Edit:
The VESC is made by Benjamin Vedder. His github. https://github.com/vedderb
THe speed controller was design to drive BLDC motors. Paragraph 2 was whether it is okay to have separate sections for different voltages if all lead to ground. I can do 2 layers, but 4 layers allow the speed controller to be as small as possible for an electric skateboard.

Direct link to my Github page holding the files for examination. I used Kicad.

VESC 6.0 Schematic by Benjamin Vedder


texts: Should I use an isolated DC-DC converter?

texts:
I am designing a controller pcb for a wall climbing robot, which uses a ~150W suction brushless motor to stick to the walls and two smaller ~30W brushless motors to move around. The system consists of a high level Intel NUC (12V ~50W) and a low level ARM-M4 (3.3V). Everything is powered by a 6 cell 250 W*h drone lipo.
Would you insist on using an isolated DC-DC to power the digital logic? The non-isolated supply can save some money and space.
Some precautious that I took to save the precious digital logic:

The Suction motor driver (electronic speed controller) is connected through a TPS1HA01 power switch with over-voltage over-current protection (what if the beast stalls at 150W).
Each motor driver is connected through their own LC filter and a TVS diode.

After reading a similar post I am inclined toward the isolated choice. What do you think?
Thanks!


texts:
I am trying to simulate boost converter using voltage-mode controller as the schematic below. However, the circuit doesn't work as expected. Output voltage is supposed to be equal to reference voltage which is 8V but in this case it is only 3V.
Also the output of comparator is always 0 which means the switch is permanent OFF.
I tried to tune PI controller parameters but it doesn't help much.  Is there a systematic method to design this without having to tune a lot?

Schematic:

Output voltage and inductor current waveforms:

Vsaw, VPI3, Vsw signals:

VPI1, VPI2:


texts: USB powered device with multiple Decoupling Capacitors

texts:
I have a USB powered device with multiple IC's. From what I've read it's standard practice to use a combination of multiple range capacitors for decoupling each individual IC, with the smallest being as close as possible and larger capacitors not too far away.

However, I'm running into a dilemma:

According to this source, the maximum allowed decoupling capacitance for a USB device is 10uF. With several IC's all having a combination of 0.1uF and 2.2uF/4.7uF decoupling capacitors, I'm easily exceeding this limit because they're all in parallel.

The only solution I can think of is to reduce/eliminate the larger decoupling capacitor and/or try to clump a few IC's larger decoupling capacitors together while keeping the smaller decoupling capacitors close to each IC.

In my mind neither of these solutions seem ideal. What is the recommended decoupling layout for multiple IC's on a USB powered device?

The theoretical power consumption of all the IC's under use is still below the limit that can be supplied via USB 2.0.


texts: Project Help For 12 volts output Buck Converter

texts:
So we are building a 12 volts output buck converter with 17 volts input for our project.
And i was wondering if using LM317 as regulators and NE 555 for the PWM generator a good idea.thanks.


texts: Best mixer for quadrature FM demodulator

texts:
I need to demodulate an FM signal and I want to use a quadrature demodulator for this. The signal is 16±0.15 MHz, 3.3V output from CMOS oscillator. I know that Gilbert cell mixers are most commonly used for this but I don't have any of them around yet I have some other mixers and parts that can be used as ones:

ADE-1, diode ring mixer
SN74LVC1G3157, SPDT analog switch
BF1105 and BF998 dual-gate MOSFETs
SN74AHC1G86, XOR gate with Schmitt trigger inputs

Which one of those methods can achieve highest SNR and lowest distortion (<3% is okay)? How good is the performance compared to Gilbert cell mixer? What are the main requirements for choosing a mixer for quadrature demodulation?


texts: AMS1117 short circuit protection not working

texts:
I recently shorted out my AMS1117 5V, turns out now the output is directly connected to input. That is, now I get direct 12V supply onboard. I wanted to know if it is specific to a brand or the if the built in short circuit protection doesn't work for anyone.
edit:
I short circuited my output of AMS1117 to ground . The short circuit protection did not work.
Instead now the input and output of the regulator are internally connected .. this is very dangerous for my onboard components
AMS1117 datasheet here


texts: Quick question about phase displacement in AC circuits

texts: Z1, Z2(impedance) and the effective value of I2 is given. My question is whether I can assume phase displacement of the current I, let's say 0º. I can finish the analysis of the circuit easily this way. Can I assume this?


texts: How is translation granule set in ARMv8-A processors?

texts: ARMv8-A supports three different translation granules, viz. 4K, 16K, 64K. However the programmer's guide doesn't speak how this is set. What field of which register controls the granule setting? Can anyone point me to the relevant part of the documentation?


texts: Designing an Ethernet / RJ 45 disconnector

texts:
I am currently in need of a device that is plugged in between a host and a client to cut the connection regularly on a hardware level.
This should simulate unplugging the Ethernet cable and plugging it back in.
I found something in the right direction as seen here:

However, I don't want the switch to be toggled manually but rather by an external source such as an Raspberry Pi GPIO.

As I'm not a professional electronical engineer my questions are as follows:

What kind of component do I need? Are there relays that can handle this? If there are, what relays should I look for?

Maybe there are dedicated ICs for this kind of job? Where do I search for them and how?

Thanks in advance!


texts:
I would like to use a 12V relay in my LTspice circuit, however there is no relay in the component list.

How can I do?

Relay model: SRD-12VDC-SL-C


texts: ATtiny85 pulses its pins at about 10Hz after some kind of programming/wiring messup

texts:
I have an ATtiny85 which had a simple program PWMing its output pins to pulse some LEDs.

While messing round trying to wire up Raspberry Pi SPI to program it with avrdude, it's gone into a state where when powered up it pulses PB0,PB1,PB2,PB3,PB4 at maybe 5 Hz (guessing by eye), even if I hold reset to ground (which I would expect to make it an SPI slave). I never got as far as actually feeding in any program code - just using avrdude to check that it can see the ATtiny85, which it could till this happened.

Is this broken or is it some state I can fix?


texts: LED for High frequency/blinking application

texts:
Which parameter in the datasheet of the LED defines the turn on time and turn off time?
What kind of LEDs are used for high speed switching applications?
Thank you


texts: Pull-up or pull-down at the optocoupler output

texts:
For a normal optocoupler with a LED and a phototransistor, we can put the load resistor (RL) at the emitter or the collector of the phototransistor, just like this

But for a high-speed optocoupler with some other digital logic inside, like HCPL-060L, it seems the pull-down version should not work, right?


texts:
I'm designing a motherboard with Tiger Lake UP3 CPU, and I want to use Intel I225 Ethernet controller for the LAN ports.
I225 reference design includes an SPI flash. I couldn't find what is the purpose of this SPI flash or if we can give up on it.
Note: in the SPI flash design notes, it's written that a 16Mb SPI Flash is required for supporting Option-ROM (PXE code), and 8Mb SPI Flash can be used when Option-Rom is not needed.
I can understand for example in the 16MB case why the SPI is useful. but I still don't know why it's useful in the 8mb case.


texts:
Are there any relays that essentially have the same logic as an SR Latch? Specifically I need one that will latch when power is lost to the coil and then require a separate signal to reset or "unlatch" the signal. I have found many normally closed latching relays but those would not work for this situation because when power is lost to the entire circuit the relay unlatches.
Thanks


texts:
I've started working with the AT86RF233 a few weeks ago and found the Ranging Toolbox (RTB) package quite impressive. It's the first time I'm using wireless modules, so I wanted to see if I could use the Phase Difference Measurement Unit (PMU) for another usage than ranging.

My problem is that I can't get the PMU value. Even trying just to print the value during a ranging of the original RTB firmware doesn't work. I noticed I had to set the pmu_en flag, but this didn't change much. I just get values between 0 and 20 instead of the expected 0 to 255. When pmu_if_inverse enabled I just get 0.

Has anyone experienced the same problem? Or is there some working code using the PMU I could read?


texts: Problem with my 8-to-3 line priority encoder using verilog gate level description

texts:
I am attempting to build a working 8-to-3 line encoder using gate level description in verilog. Although, I have working models, in terms of successful compilation and simulation, the recurring issue seems to be that my circuits just do not seem to implement the encoding and thus the priority as they should do.

For instance, when D2 should be encoded as, 100, 101, 110 and 111, it is only being encoded as 100 and 101 and instead D3 is commencing its encoding at 110 and 111, instead of 1000. Please see waveform below:

This is starting to be a pain in the backside, because regardless of which implementation I use, the results are always the same.

Please also see an example of one such description below:

module prior_otb_enco(Y, D, V);
  output   [2:0] Y;
  input    [7:0] D;
  input    V;

  wire    D7_not, D6_not, D5_not, D4_not, D2_not;
  wire    wa0, wa1, wa2, wa3, wa4;;

  //instanitate gates
  not    g0 (D7_not, D[7]),
         g1 (D6_not, D[6]),
         g2 (D5_not, D[5]),
         g3 (D4_not, D[4]),
         g4 (D2_not, D[2]);
  and    g5 (wa0, D6_not, D4_not, D[3]),
         g6 (wa1, D5_not, D4_not, D[3]),
         g7 (wa2, D5_not, D4_not, D[2]),
         g8 (wa3, D6_not, D[5]),
         g9 (wa4, D6_not, D4_not, D2_not, D[1]);
  or     g11(Y[2], D[7], D[6], D[5], D[4]),
         g12(Y[1], D[7], D[6], wa1, wa2),
         g13(Y[0], D[7], wa0, wa3, wa4),
         g14(V, D[0], D[1], D[2], D[3], D[4], D[5], D[6], D[7]);
endmodule

Therefore, any insights that anyone can provide will be very much appreciated.


texts: Why do VR motors like sinusoidal current?

texts: I have a question regarding powering electrical motors, variable reluctance motors to be more precise (ie. Stepper motors). This kind of motor, in a perfect situation would like to be powered with current thats shape is a sin wave and a cosine wave (for stepper). Even when doing microstepping, one should try to follow the shape of sin and cos to have the smoothest rotor rotation. Also if VRM was used as generator, it would  generate sinusoidal current. This all seems logical, looking at the circle construction of the machine. I believe if one was to unroll the vr motor and make it drive in a plane motion way, it wouldnt have to be powered with sin/cos and also wouldnt generate current in that shape. My question is- would someone please explain me in a more "fact and proof" way why does the current shape has to be sinusoidal for a vr motor? Also, please correct me if anything i wrote was not true. I would apreciate all help!


texts: Determine Transfer Function from Step Response with Non-Zero Initial Condition

texts:
I saw in this forum a way to determine a transfer function from a step graph. I wanted to know how it is done when the initial condition is non-zero, like the following step response below.

How can I estimate the transfer function of the system from this data?


texts: In VHDL what is a data operator type "variable" when it is translated to circuit?

texts: VHDL code is finally converted into hardware equivalent when it is synthesized. What happens to data operator type "variable" when it is synthesized?


texts: BJT Differential Amplifier Common Mode & Differential Mode Gain

texts:
I have a few questions about how to derive the differential gain and common mode gains:

simulate this circuit – Schematic created using CircuitLab

Differential Gain:

Taken from Art of Electronics - "Imagine a symmetrical input signal wiggle in which input 1 rises by v_in (a small signal variation) and input 2 drops by the same amount As long as both transistors stay in the active region, point A remains fixed."

I don't follow how A would be fixed?

However taking it to be true (no current through R3) I get the voltage gain as follows

(V_in1 - 0.6)-(V_in2-0.6) / 2*(R_E+r_e) = 0-V_OUT / R_C

V_OUT / Vdiff = -R_C/(2*R_E+r_e)

but in the AoE they have G_dff = R_C / 2*(R_E+r_e) what happened to the (-) sign?

Common Mode Gain:

Common Mode signal = (V_in1 + V_in2)/2 = V_in2

Following the suggestion to split the pair into 2 sections (I'm looking at section on the right)

(V_IN2 - 0.6)/ (R_E + r_e + 2*R3) = 0-V_OUT / R_C

This is as far as I get - I don't see how I can get rid of the 0.6V to get the right answer of -R_C/(2*R3+R_E).

Thanks in advance !


texts: Am I understanding I_dss of this P-channel MOSFET correctly?

texts:
I have a device that operates with a 3V lithium cell, but can optionally accept a secondary power input which disconnects the battery. This schematic shows my implementation of this function:

simulate this circuit – Schematic created using CircuitLab
(Circuit Lab does not appear to have a Schottky diode symbol.)
When 3V is applied to the DC 3V In node, the P-channel MOSFET Q1 (DMG2301LK) "opens" and the battery should effectively be disconnected.
The device draws approximately 10 µA in standby mode on battery. With secondary power, it is expected to draw an additional 64 µA due to the bias resistor R_bias. The resistor is meant to ensure that the MOSFET is in conduction when no secondary DC input is present.
Measuring current, there is ~3 µA being drawn from the cell. I was expecting < 1 µA. Reading up on the MOSFET, I am thinking this may be due to \$I_{DSS}\$ (zero gate voltage drain current). The datasheet shows that this can be -10 µA when \$V_{GS}\$ is 0V and \$V_{DS}\$ is -16V. I measured \$V_{GS}\$ to be 132 mV which coincides with the expected \$V_F\$ of the Schottky diode (VSKY05201006) at that current.

Is it likely that current drawn from the cell through the MOSFET is due to \$I_{DSS}\$? (There is a 47 µF ceramic capacitor before the transistor, not shown in the schematic, but I would not expect much leakage through it.)
If so, would it be correct to assume this current is due to the slightly lower voltage (at the source) of the alternate DC input because of the voltage drop introduced by the diode?
Suggestions to making this more effective at disconnecting the battery when secondary DC is applied?

Edit:
I experimentally verified that increasing the secondary DC input voltage to 3.13V reduces current drawn from the cell to < 1 µA. So I think I've answered the question somewhat, but any additional insight regarding \$I_{DSS}\$ would still be helpful.


texts: What software use to hack wireless protocol ( logic analyze ) USBee

texts:
Q: What software do you use for logic analyze?

Why: I try to hack(reverse engineering) my home wireless heating system control to make my own central control unit.

Wireless: My heating system uses the CC1101 chip to communication between wireless thermostat and floor heating control unit.

Capture: I use Usbee and Sigrok Pulseview to capture logic communication between MCU and CC1101. But pulseview is really "stupid" it can't print captured data even or export it to excel or export is as image.

How I do it: Manual read data from pulseview -> write it to excel -> and manually analyze communication in excel.

What I need: For example put data horizontal side by side to compare the difference in communication on different commands?

Example analyze: link


texts: Where to buy the inductors for LC filter in low voltage high power converter designs?

texts:
I am doing some reasearch work on converter topologies and the filter requirements in each topology. The filter I am using is LC type and the inductance I have are 188,150,75 uH.
Maximum ratings are :

Ipeak = 300A
Vmax = 300V
Fundamental Freq = 50Hz
Switching Freq = 7200Hz
Ripple Ipeak-peak = 10A

Now I am looking for the cost and size of the inducator for these specifications. Only I find is low rated current inductors on Mouser and DigiKey. So if any can provide me a the cost of the inducators or a lead how to find them, would be highly appreciated.


texts: Read a 6DOF IMU (Gyro + Accelerometer) using PRU - Beaglebone black

texts:
I plan to use an I2C interface in order to read the IMU (SparkFun 6 Degrees of Freedom IMU Digital Combo Board - ITG3200/ADXL345). Since the communication rate using I2C is 400kHz, I thought I should use the PRU in order to read the sensor as fast as possible, as it is 40 times faster in reading GPIOs compared to the Linux host kernel.

Now my question is how do I use I2C to read the sensor using PRU?
If I2C implementation in PRU is complicated , then what are my other options?

Thanks


texts: *how* are things triggered on clock rise, fall, high or low,

texts: I know the purpose and function of triggering logic , such as a d flip flop, on certain clock conditions. However, what I have not been able to understand is actually how these "triggers" work. i was thinking maybe to do this you just AND the input with the clock, but I don't feel like this is the right way.


texts: IR to audio converter (frequency and level)?

texts: What kind of IR detector and converter circuit could be used to down-convert an IR remote signal (in the neighborhood of 35 to 45 kHz) into audio frequency signals (0.1-20 kHz) of the appropriate level and drive to feed the mic input on a mobile phone TRRS headset jack for further analysis and decoding?  Would something simply involving a divide-by-4 cascade of two D flops work?  Or would decoder/(re)encoder chips or a microcontroller chip be necessary?


texts:
I have this amplifier as part of a larger system. To my understanding this circuit will always have a negative gain Vout/Vin, since we have ground on the non-inverting input and a non-zero signal on the inverting input. Is this correct? If so, would it become a non-inverting op-amp if the non-inverting input was Vin while the Vin from my original circuit is set to ground?

I tried finding the gain in the laplace domain like this:

Defining a node V1 and then using KCL I get the two expressions
$$
\frac{V_{in}-V_1}{sL_1} = sC_1V_1+\frac{V_1}{R_1}
$$
and
$$
\frac{V_1}{R_1} = \frac{0-V_{out}}{R_2+sL_2}
$$

Combining these two gives

$$
\frac{V_{in}}{sL_1}+\frac{V_{out}+R_1}{R_2+sL_2}=-\frac{sC_1R_1V{out}}{R_2+sL_2}-\frac{V_{out}}{R_2+sL_2}
$$

Rearranging for the gain

$$
\frac{V_{out}}{V_{in}}=-\frac{R_2+sL_2}{R_1C_1L_1s^2+L_1(R_1+1)s}
$$

I can't see where I might have gone wrong in the calculation of gain, but at the same time it doesn't really make sense to have a negative gain at this part of my system.


texts:
When lightning strikes or the earth wire (from the wall outlet) suddenly gets charged negatively for whatever reason, then, in theory, can it cause ESD-damage to a PC?

Because the grounding wire (inside the ATX power cable) connects earth directly
to the motherboard's ground-plane.

If earth is more negative, the ground-plane accepts electrons from earth.
Can this charge move too fast (if the potenial is large enough) and cause ESD-damage?


texts: Taking input from a generic usb gamepad in controllers (preferably like MSP430g2231)

texts: I was just wondering how can I take input from this cheap but awesome HID compliant generic computer gamepad into the launchpad. I know the launchpad could work at good speed so what it would take to take the input? The info doesn't really have to be about only launchpad just give me generic info, I can build off that.


texts: Adding dependant sources in LtSpice (CDCS)

texts:
I have the following schematic of the circuit, I wanted to added I2 as a Current Dependant Current Source depending on current on in V1 as three times the value, or, I(I2) = 3I(V1)

I have tried various tutorials, and used circuit element F and current both, its not working with any. There is always an error in circuit element I2
What can be done to achieve this result. Thanks a lot!


texts: PIC32MX350F256 Errata , IO open Drain Issue

texts:
In one of our Product we used Microchip micro controller “ PIC32MX350F256L”. Attached image is small part of circuit showing uC interfacing with a SPI device. We are using bit banging communication programming for SPI. We also used MOSI,SCLK,CS,MISO and one INT line is as open drain config in uC.

"every line has separate 5.6K pull up resistor"

Slave device generate the Interrupt when its slave data is ready to read,
During testing we found that micro controller not able to detect if any level change on this INT pin.we tried to check with Scope as soon as we touch the probe on INT line , that time only uC detect the INT. ( So on INT IO we change it from open drain to internal pull up enable, so we have both internal and external pull on line, this time everything is fine)

We also refer the micro controller errata sheet states that “The Open Drain selection (ODCx) on I/O port pins is not available when the pin is configured for anything other than a standard port output.  In addition, the Open Drain feature is not available for dedicated or remapable Peripheral Pin Select (PPS) output features”

Now Hardware is already design, and we prefer to keep external pull always on line. also we prefer bit banging programming. Now Current revision also have the same Errata. how can we Workaround this issue.

Should we change all Input pin (open Drain) to Internal pull up enable.(with External pull also there)
Should we change all Output pin (open Drain) to Internal pull up enable.(with External pull also there)
Both 1 and 2.
What happen in I2C bit bang programming, since I2C need internal open drain.


texts: Electronically switched decade resistance box design

texts:
I'd like to design a decade resistance box that uses a microcontroller to control the resistance.

Would it be possible to switch between different valued resistors using transistors? (or another component?)


texts: Hacking an RC car controller to implement a joystick (PWM)

texts:
My RC car controller (transmitter) has only 4 buttons (left wheel forward /backward, same for right)

I want to implement a joystick using Arduino.

The Arduino will use PWM on the transmitter circuit, and will use four transistors as emulated button. (When I activate the transistor, the transmitter will think the button is activated.)

Do you think it's possible?
Do you think it is safe for the transmitter ?
Is arduino pwm to fast for the transmitter? do I have to make my own slower version of PWM?

Here are some photo of the transmitter:


texts: Where does an IN5408 diode go in a hobby motor, on/off switch and AA battery holder setup?

texts:
I was told I need to add an IN5408 diode in the following setup but I am unsure where it goes.

2xAA battery pack
Positive to On/Off Switch (simple open close circuit switch)
To small hobby motor

Negative from hobby motor to battery pack

I am not sure if I need to protect the switch, the battery pack or the motor from feedback. I do know which direction the diode allows flow. I just don’t know where to put it in this circuit.

Thanks for any help in advance. Sorry it’s such a simple question but google returns everything way more complex than what I am doing and it confuses me.


texts: Wien bridge oscillator amplitude stability methods

texts:
I have read things about tungsten bulbs and its thermally controlled resistance. But what can I use for an electronics project will be builded on a breadboard. I searched for tungsten bulbs and all they were looking like regular size 100+ V lamps.

So what is the alternative in electronics level for amplitude stability of wien bridge oscillator?

p.s : don't know relevant or not but, the oscillator will be used in an auido project.


texts: Computing Voltage Drops in an AC Circuit

texts:
Compute for the theoretical voltages across the resistor and inductor for 10 kHz in polar form. (1.23 kΩ, 5 V RMS, 3.3 mH.)
I don't know where did I go wrong, my answer is very far from the data that was collected from the experiment. All voltage are in RMS.
Data:
VR = 3.22 V.
VL = 1.46 V.
Own Computation:

simulate this circuit – Schematic created using CircuitLab


texts: Parallel resistor not affecting rest of the circuit

texts:
I have been asked the following question:

  The resistance, r, is not known in fig(1a), why does its value not affect potential at b?

By Thévenin's theorem, any arbitrary voltage source can be replaced by ideal voltage source with a resistor in series (without affecting the rest of the circuit - rendering those two equivalent). However, I don't think that this is the answer they are looking for, neither I can think of any other way to explain why this resistor does not affect value of \$V_b\$. I have tried to do mesh-analysis, but that failed miserably.

Any other ways?


texts: I can't get a meaningful output from a circuit in Thomas & Moorby's exercise 2.7

texts:
I'm working out the exercises in "The Verilog Hardware Description Language" to learn Verilog. I'm currently stuck in exercise 2.7, and since I couldn't find anything on the web about it I thought I'd rather ask here.

I'm implementing this in Vivado and trying to simulate it, but I think the output is always zero. The exercise asks for a description using different techniques of the FSM represented by this circuit:

This is my current code for the circuit, which I'm testing with a test bench that correctly simulates a clock with a period of 20 time units.

timescale 1ns / 1ps

module reference(
input Ain,
input Bin,
input Cin,
input rst,
input clk,
output reg Y
);

reg Q0, Q1;
wire theORW, AandW, BandW;

or #1
    theORG (theORW, AandW, BandW);

and #1
    AandG (AandW, Ain, Q1),
    BandG (BandW, Bin, Q0),
    YandG (YandW, Cin, theORW);

always @(posedge clk, negedge rst)
begin
    if(~rst)
    begin
        Q0 <= 0;
        Q1 <= 0;
        Y <= 0;
    end
    else begin
        Q0 <= AandW;
        Q1 <= theORW;
        Y <= YandW;
    end
end

endmodule

When I simulate the code Y is always 0, no matter what combination of inputs I try and keep high during many clocks. I'm issuing a reset first. Vivado currently builds this RTL representation that looks just like the diagram in the book:

Am I misunderstanding something? Is this the correct behavior of the circuit?

Exercise text:

  2.7 Write a description for the FSM shown in Figure 2.7 with inputs Ain, Bin, Cin, clock, and reset, and output Y.

  A. A single always block

  B. Two always blocks; one for the combinational logic and the other
  for the sequential.

  C. Oops, this circuit is too slow. We can’t have three gate delays
  between the flip flop outputs and inputs; rather only two. Change part
  B so that Y is a combinational output, i.e. Move the gate generating
  d2 to the other side of the flip flops.

  D. Simulate all of the above to show that they are all functionally
  equivalent.


texts: Digital Logic : Design a Calculator (or something similar to it)

texts:
So here's the story, We have been asked to design a Circuit (2 inputs each input has 2 bits)
functions : add - sub- multiply - Exclusive OR
and 2 select lines (we will use 2 IC'S of 4x1 Multiplexer)

and then our prof. said our report should be computerized ( Truth Table, K-maps, Equations, and Pin Assignment)

I've finished all of them except Pin assignment... I don't even know what Pin Assignment mean.

Can someone explain?


texts: Change AC signal frequency without changing the voltage

texts:
I have a non constant -/+1 Volts to -/+7 Volts AC audio signal. I want to design a device that takes this input signal, doubles the frequency, without changing the voltage.

So, the output voltage is the same as the input voltage, but suppose the input signal's frequency is 82.4 Hz. The output should be 164.8 Hz. I want this device to work with other frequencies.

In other words, it shifts the pitch of the audio by one octave.

Any leads?

Thanks in advance.


texts: electronic devices impedance and drawing current

texts:
I have a questions that kind of bugging me for a while. So in electronic devices, it has capacitors, inductors, resistors, transistors and etc. All of these together is the load of the device, which is impedance.

From what I understand the impedance lower when the device needs more current, but how does the impedance lower exactly? Isn't when a device, for example, uses more transistors meaning it has more load, therefore, higher impedance?

Thank you

PS. I am a computer engineering student. So please don't be too harsh on me. And If you want to explain in technical terms, I think I can understand it.


texts:
So while walking around school today I found a neat little piece of hardware thrown in the trash. After a quick overlook, I noticed that the display was one of those 32 segment kinds (like a speak and spell). So I took it apart and starting running some basic test and looking up things on Google. Unfortunately I am stuck now and am not sure how to continue.

The IC that controls the display has 40-pins and it too old to get hits on Google. To interface with the display, there are 8 pins. Two are for Voltage, and two run to Ground. Using an oscilloscope, I found square waves on two other pins as well. Don't really know what the last 2 pins do. Using a simple circuit for adjustable voltage on my Arduino, I was able to get the display to light up, but that is it.

So my question is, How can I get this display to play nice with my Arduino?. Do I need some other diagnostic tool? Or is it near impossible to do?


texts: Fourier transform does not produce the correct result

texts:
I am trying to calculate the absolute value of a certain sinusoid to see how MATLAB calculates the Fourier Transform by using the freqz() command. Here is my Matlab code

    Np=20;
    n=0:1:Np-1;
    s1=[sin(2*pi/Np*n)];
    h1=freqz(s1);
    figure(1);
    plot(abs(h1));

And the plotted result is:

My question is:
My theoretical plot should only show one "bar". Why doesn't it do that? Is my code wrong?


texts: What happened to the reflected wave back to source?

texts:
The setup is as followed

Signal generator (50 Ohm) -> coax cable (50 Ohm) half wave length-> short circuit

Of course I didn't do this because I thought this might blow up something, it's just a thought experiment.

So would the reflected wave being completely absorbed by the internal resistance?


texts:
I made a circuit but I am not sure it is going to work. The circuit is supposed to drive a 36 V 28.5 A motor. I am having trouble finding out if applying 5V to IRLZ44PBF would open it fully and allow 36V across the motor terminals.

And if you find any flaws please let me know. The buttons are actually outputs from an Arduino.


texts:
I recently bought a PowerTac E9R-G4 flashlight that uses 18650 batteries. Replacements can be bought on amazon.com fairly cheaply.
The box the flashlight comes in and the manual, however, both say "ONLY USE PowerTac 18650-3200mAh High Drain batteries".
The battery that the flashlight came with says "11A max continuous discharge - 15A max pulse discharge". Maybe regular 18650 batteries don't support pulse discharges at that amperage? Altho then again idk why pulse discharge would matter unless I was using the strobe mode that the flashlight has?
What would / could happen if I used other 18650 batteries? More generally, are all 18650 batteries interchangeable with one another?


texts:
I've been reading about the great War of Currents and I've been trying to find out how DC power was generated in great volumes. I can't imagine it was with dozens of chemical cells, but I can't find information on it.

A secondary question is about how Edison planned to generate DC from Niagra falls -- I can't see how to generate anything but AC from that.


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I tried to make 2 buttons that can fill a shift register with bits.
I work it out in Proteus before soldering.
Description:

one can press one of two buttons.
pressing the left button shifts in LOW (D) (red LED lights up).
the right button shifts in HIGH (D) (green LED lights up).
both buttons set CLK to HIGH (CLK) (blue LED lights up).

VCC is 5V
switch circuit:

shift-register:

Datasheet SN74LS595
The buttons seem to work, however, (in Proteus)
when pressed HIGH at start the first bit is always missing in the shift register (it doesn't go to HIGH) the second bit shifted in (HIGH or LOW) appears .
when pressed LOW at start, or a sequention of lows, do not appear.
It only deliver expected results when I start with a HIGH.
Is there a way to solve this, has it something to do with the latching?


texts: Turn off power strip when another circuit is turned off

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I have a switch in my wall which turns a outlet on and off, however I'm nearing maximum capacity on that circuit. I want to be able to plug more stuff into it so that I can turn it off with this same swich.

My idea is to somehow build a little box which plugs into 2 separate circuits, the one controlled by the switch, and another circuit which is on all the time. The box would also have a plug that I could plug a power strip into.

When the power to the circuit controlled by the switch is turned on, the box activates a relay which turns power on to the output which goes to the power strip, coming from that secondary circuit.

(Oops, spelled circuit incorrectly)

Does this make sense? In this way I can control more devices with my switch.

How could I build this? I know it'd use a relay, but what else?
Safety concerns?


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I've modeled the above circuit, but the breadboard version does not work.
(There are no unexpected oscillations - I'm just looking at DC levels.)

I'm trying to shift a 0.4V - 2.0V DC signal to 0V - 10V DC signal.

There is ref. 0.4V at pin 5 (+) of U6, the voltage follower, and 0.4V as you would expect on 6 (-) and 7 (output).

If I breadboard this circuit, U6 output (pin 7) does not give the expected voltage; it's about 0.6V, so the output on pin 1 is not 10V as expected. If the main input on R1 is 1V instead of 2V, the circuit works as expected. Can anyone offer an explanation?

Before you ask - I've breadboarded it twice!
I always thought that a voltage follower was simple!!
Current taken by circuit is >1mA.
Thanks.


texts: Questions about a relay controlled AC fan setup

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I need to switch an AC fan by a DAQ board's analog output.

Here is the setup in my mind for the moment:

The DAC of the data-acquisiton board can output 0 to 10V DC and can deliver max 5mA current. When the relay is ON the mains will power an AC fan. Here is the fan: http://uk.rs-online.com/web/p/axial-fans/2781543/ According to the data sheet I assume the fan will drive less than 1A. So I'm planning to use the following solid state relay: http://uk.rs-online.com/web/p/solid-state-relays/0346895/ since the data-sheet says it can handle upto 10A.

I have couple of questions here:

1-)  In the relay's data-sheet, there is a section on the input current range which is not fixed. So I want to be sure if DAC can supply enough current for this relay. Do I need a voltage follower between the DAC and the DC input of the relay?

2-) If I can manage to turn on and off the relay, would the switching action cause a sudden peak current and damage the fan motor? Is there a difference between turning on the power of the fan via the relay and via a manual switch? I think motor works quite ok with the manual switch. I'm just wondering if the relay's switching action might cause some harmful inrush currents for this fan motor.

3-) If I can achieve to turn on and off the AC fan succesfully by using the relay and DAC, is there a possibilty to sudden stop this motor as well? I mean I have seen a VFD AC motor speed controller which is controlling a 3-phase AC motor. There is a switch which powers on of and breaks that motor. This manual switch when switched for the "break" function motor very quickly stops rotating. Maybe it is the function of the VFD controller or the 3-phase AC motor itself and may not be applicable in my case. The reason I'm asking about this, when the fan is powered off it keeps rotating for long time until it stops.


texts: Where Does VDD+0.3V Input Limit Come From on IC chips?

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There are a variety of integrated circuits that specify that their input voltage can span a fairly wide (absolute maximum) range, e.g. -0.3V to 6.0V (ref, pdf page 4), and then have a "Input Voltage at any pin" constrain that depends on the input voltage, e.g. -0.3V to VDD + 0.3V.

That, in effect, makes the chip not be I/O tolerant to voltages that exceed the input voltage by more than 0.3V but are within the absolute maximum specs of what the input voltage allow, and forces me to apply some kind of external level shifting circuit to those inputs.

So what is the practical reason for this kind of limitation in the specifications for integrated circuit I/O pins?


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I would like to know what would happen if a capacitive load is connected to the secondary of a transformer.
I simulated the circuit on Proteus. The inductance of the secondary coil was 0.1 H
and the frequency of the supply is 50 Hz. The secondary coil produces 15V peak to peak.

I connected a capacitor across the terminals of the secondary coil.

When the capacitive reactance of the load is equal to the inductive reactance of the secondary coil (Resonance at 50 Hz), I found that the voltage is increased to about 50 V peak to peak!! (The value of the capacitor was 100uF or 101uF).

First, I thought that the mistake was in the simulator so I connected a small resistance in series with the capacitor. I tried from 1 ohm to 50 ohm. The voltage was dropped but it was sill higher than 15V peak to peak.

Why resonance increases the voltage?
If I need to increase the voltage, Why should the resonance be at 50 Hz which is the frequency of the supply? Why the voltage does not increase at a frequency of say 2 KHz?
If I made this experiment practically, Will the transformer wear out?

Thank you very much,

simulate this circuit – Schematic created using CircuitLab


texts: Impedance mismatch in LISN for EMI/EMC test

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I am currently designing LISN for CE-102 test.The schematic of the circuit is provided below.

When I connect the circuit to the network analyzer the impedance is coming as shown below

expected graph is shown below.

I'm unable to understand where is the flaw.
After 1 MHz, the impedance should go constant but my circuit it is increasing linearly.
Please guide me to stabilize impedance in my circuit
After all, LISN is all about providing stabilized impedance for mains network.


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the input voltage is from mp3 player.

Now, why is that when the input voltage is around 5 mv pk, there are no clipping issues but if we change the input voltage to around 400 mv pk(which is common in every mp3 player including mobile phones), there is severe clipping as described below in the picture.

here, we can see there are no clipping issues

but here, we start to inject the mp3 player as the voltage input (400mV)