texts: What is the difference in meaning of a voltage signal and current signal?

texts:
This might sound like a crazy bad question. But I'm wondering even though current and voltage inevitability co-exist, why do we use the term for one concept(current or voltage)? If there is a signal out there somewhere, it is both current and voltage at the same time. But we name only one of its property.

Is that about knowing one of them well? I mean lets say we have an amplifier and if we only set the amplifier with a "known voltage gain" we call it voltage amplifier and if we set it with a "known current gain" we call it current amplifier? Or is that because the nature of the input signal?

Could you give an input signal example and explain why it is called a voltage or current signal?

EDIT: My confusion didn't settle. Lets say we have a single stage amplifier. And it has an input and output. So when you look at such circuit and its input and output, what makes you to conclude it is amplifying a current input signal or a voltage input signal? What is the method to name the type of the input signal? Imagine it is increasing both. I still don't understand how to distinguish.

EDIT2: imagine a typical common emitter stable biased single npn bjt transistor amplifier. such as: http://www.electronics-tutorials.ws/amplifier/amplifier9.gif?81223b . the base voltage in this case is "bias voltage + small signal voltage - emitter voltage". and the input current current is very low. now look at the output. output voltage increased. okay. but wait.. output current also increased and became "beta*Ibase". So now the input current increased and the input voltage also increased.. is this a current or voltage amplifier? and if it is X amplifier does that mean the input signal is X signal. (X is current or voltage)


texts: Where to place debouncing circuit for remote mounted buttons and rotary encoders

texts:
I have an application where a push button and mechanical grey-code rotary encoder(user inputs) need to mounted away from main pcb. 24" - 48" away. This is for space and packaging reasons.

Is it OK to have the debouncing RC circuit on the PCB and the switches/encoder remotely connected via cable, or does the debouncing circuit need to be with the switches?

Encoder circuit from datasheet:


texts: Most efficient and rigorous way to calculate input/output impedances (transistor circuits)

texts:
I've always had troubles with input and output impedances. It is not very well explained anywhere else I could look on the web so...

What is the most efficient and rigorous way to calculate input and output impedances?

A detailed step-by-step guide is what I'm looking for here, hoping the time it may take you will be beneficial to many others here. As a practical example, why not apply it to this simple common emitter circuit (AC and DC bias).

I'm assuming that would be starting from the definition of impedance $$Z_{in}=V_{in}/I_{in}$$
and vice-versa, but as soon as there are different paths for the current as seen above, I don't really know how to proceed.


texts: Why am I getting 239 VAC between GND and line when the device is turned off?

texts:
I noticed a weird thing that I don't understand.
I'm working on an electronics project which has inside of it a 230 VAC (I'm in Europe) to 12 VDC transformer.
For the convenience, the project is plugged to the Eaton ePDU G3, which is a sort of a very smart network-controlled power strip which, among others, allows to power each socket on and off. The PDU is connected in turn to the UPS, that is, a unit with a battery inside which keeps powering the appliances in a case of an outage. Finally, the UPS itself is plugged into a surge suppressor. Everything is grounded properly.
When the device is powered on, everything works as expected. When I measure the difference between the two wires, this is what I get:

GND ↔ Line: 239 V
Neutral ↔ Line: 239 V
GND ↔ Neutral: 1 V

However, when I turn the device off through the PDU, I get:

GND ↔ Line: 239 V
Neutral ↔ Line: grows from 4 V to 36 V for something like thirty seconds, then drops to zero, grows again, etc.
GND ↔ Neutral: decreases from 236 to 215 V for something like thirty seconds, then goes back to 236 V and starts decreasing again.

The measurements are taken with an inexpensive multimeter, which may explain why adding the values from the last two rows doesn't always equal 239 V. I don't have an oscillograph, so I can't see the exact pattern.
I imagined that the mechanical relay which turns the appliance on and off in the PDU is acting on the Line, breaking the connection when the socket is turned off. In practice, the relay acts on the Neutral instead. This creates an electric shock hazard: it looks like the appliance is powered down, but there is still a 239 V differential between some of the wires inside.
What could be the reason for a PDU to do it this way? Am I missing something?


texts: How to initiate a call on a GSM module from DTMF tones

texts: Can someone tell me if it is possible to make a call from a GSM module using only the DTMF tones that a keypad puts out? If not, can someone explain how I would make the call using only the keypad, and maybe another bit of equipment?


texts: Is there a practical way to provoke/create AC power line noise?

texts:
We are suspicious of AC power line noise(common mode or differential) aka dirty electricity which sometimes appear and affect some other sensitive equipment. But we are not sure if this random noise is due to conducting high freq. noise through AC power lines.

I tried to turn on and off a vacuum cleaner next to the sensitive setup but it did not provoke anything. Is it futile to try to create such noise for short period of time? Or is there a practical way worth to try?


texts: What component does this MOSFET-like symbol represent?

texts:
What does the following symbol represent?

Update 1:
For some context:


texts: Temperature coefficient MOSFET vs. temperature coefficient of BJT

texts:
If you use transistors for an amplifier scheme, you want to make sure that when you parallel devices, you don't start to conduct more current if your transistors heat up.

I know that when using MOSFETs you always have negative feedback. If one takes more current, it will heat up more, and therefore the resistance will become bigger, and you will conduct less.

When using a BJT the device that dissipates the most current, will heat up most and will start conducting even more. This is unsafe and to solve this I always place a small resistance in series with the emitter.

But what is the physical explanation that in a MOSFET you have this positive temperature coefficient and in a BJT you have this negative coefficient?


texts: How to read multiple Verilog files in Design Compiler?

texts:
I'm trying to read multiple Verilog files in Design Compiler, but I have found just one command, read_verilog. It can read only one file at a time.

If I've got 1000 Verilog files, do I have to use 1000 read_verilog commands?


texts:
I am making a small color organ just for proof of concept fun. I am using 3 passive low, band, and high pass filters with their outputs connected to an envelope detector and a BJT that drives each LED. My main question is do you think this will work or do you have other suggestions to improve this design? Please disregard all component values. They were automatically added and I haven't done any value calculations yet. Assume the signal provided is amplified already and the 1N4004 diodes off the transistor are the LEDs.
Also do you think it is better to use passive or active filters in this case? I only plan on driving one or two LEDs per filter.
Thanks for any help!


texts: Does NFC drain power if tag is attached constantly?

texts:
I am not sure if it's a matter of NFC (Near Field Communication) standard or implementation of an NFC reader, but if a passive NFC tag is left attached to a reader, does that constantly drain power from it or not?

I've noticed that when I try scanning NFC tag (NFC Forum Type 2 Tags) with a mobile phone, they scan happens just once, so some de-duplication is built in, but I am still not sure if it silently re-scans all the time or not.


texts:
In my instrumentation class we have been given the following formula to get the power in decibels:

\$10Log(Power(mW)/mW)\$

I'd like to know if taking the power in miliwatts is something widely done or has any importance?


texts: how to show the internal wire wave in verilog output?

texts:
Suppose I have a code written as

module ruff(q,qbar,cp,s,r,clear);
//port declaration from the I/O diagram
output q,qbar;
input s,r,clear,cp;
// Instantiate S_R_FF
//s_r_ff sr(q,qbar,cp,s,r,clear);
wire clkbar,sin,rin;
assign clkbar=~cp,
       sin=(s&clear&clkbar),
       rin=(r&clear&clkbar);
assign q=~(rin|qbar),
         qbar=~(sin | q);
endmodule

What is a way to show clkbar,sin,rin( wire clkbar,sin,rin;) waveform also in output window in Xillnx?


texts: How do I know which wire is positive and negative when they are both white? One is coming from inside the other wire. I have taken a picture if anyone can help would be much appreciated. I'm trying to charge my computer and I'm not much of an electrician.


texts: Using a 3.3V MCU (Arm) to control reset pin of a 5V MCU (AVR) without a level shifter

texts:
On my PCB I'm trying to avoid a level shifter chip. So is it possible to connect my ARM CPU's GPIO pin (which runs at 3.3V) to the reset pin of the AVR chip?

I was thinking of setting the ARM GPIO pin to either low (to reset) or to set it to tri-state (let it float) and let the internal pullup of the AVR take it out of reset...

Do you see any issues with this?


texts:
i use dspic micro and ir2104 to drive half bridge mosfet

i use 12 volt , 150 watt switching power supply and lm2576 3.3 for dspic.

when the mosfet load is 10 watt no problem but when the load is 50 watt ,micro Continuous

reset and power up.the mosfet is irfz44

i pullup mclr pin with 10k resistor and put 100 nf cap for each vcc gnd.

i think when the mosfet goes on the high load, generate noise and the mclr pin reset.

because i dont have Voltage drop on vcc of micro but when i see gnd line with oscop its noisy when the micro is in reset

how to solve problem?

thank you

i separate gnd and vcc of dspic with 2 ferrite bead and add 100 nf cap series with mclr pin but yet dspic Continuous in reset


texts: Troubleshooting PCB of an ATX power supply?

texts:
Im new to PCBs, know the basics of electronics and testing of individual components. I have a PCB (of an ATX supply) that is not working when I power it, so I thought of testing each components like resistors, transistors, diodes, capacitors etc.

Since all these components are in-circuit together, is it possible to test them with a multimeter without removing them from the PCB, as I am doubtful whether the other in-circuit components should affect the meter reading?

I could not find a direct answer on the net, that is why I ask here. My browsing ended up with partial answers that, first you need to desolder each component completely and test individually, or desolder all legs except one being back on board and then test them, wouldn't that a be a tedious process. I have read that the order best to be followed for PCB testing goes like visual inspection of blown or cracked components or broken PCB tracks, inspection for heated components when powered, replacing ICs and running the PCB for a check for faulty ICs.

I would like to know the correct order and how to test basic PCB components whether in-circuit or not, if in-circuit do I have to power up the PCB. Saw few costly devices are available for PCB troubleshooting on markets, can't we do this at home with our cheap multimeters?

Well while working with electronics I felt the need for a DC bench power supply, and that is when I found on the net to convert an ATX to DC power supply, so thought of repairing my old one. Therefore I to need to get the ATX power supply working first.

My real problem with the ATX supply having a 20 pin motherboard connector is that, when I connect it to the supply and jump PS_ON#(Green) and COM(Black) pins, the fan doesn`t turn nor I get a voltage reading across other pins (except a 5V reading across COM and 5VSB pins). How should I start to troubleshoot my device and make it working.


texts: LM723 based bipolar power supply solution question

texts:
Why TL081 and 2N3906 may get very hot?

The simulation of the TL081/2N3906 shows the normal working temperature, but I measure +62 ºC


texts: What are the leading bytes before the USB setup

texts:
While tracing the USB using a Beagle 12, I am sometimes finding bytes prior to the transaction start. It is not the 8/32 bit SYNC, it does not start with a PID (e.g. 0x12 is 00010010b and a PID is ABCDa̅b̅c̅d̅) I am having troubl digesting section 8 of the USB 2.0 SPEC, and section 9 does not seem to address data prior to the PID.

What are these bytes for?

12 01 00 02 00 00 00 20
E6 04 16 51 04 03 01 02
00 01

Setup transaction:

80 06 00 01 00 00 40 00

Setup packet:

2D 00 10

get device descriptor:

C3 80 06 00 01 00 00 40
00 DD 94

ACK:

D2


texts: Increase ram ic memory cell count by using many ic?

texts:
Is it possible to increase a ram ic memory cell count with two of this chip?

For instance, I have two 16x4 ram ic. To increase up to 4-bits to have 16x8, it is straightforward, I just have to connect same address pin of the two chips together.

But how can I have 255x4 with these chips (thanks to the 4 + 4 inputs)?

(Sorry if I am not very clear in my explanations)


texts:
I have to design a 1100 sequence detector using Mealy model and JK Flip-Flops. Here is the state diagram:

And based on this diagram, I obtain following input statements for flip-flop inputs (A and B flip-flops):

JA = A and X
KA = B
---------------
JB = A xor X
KB = A nand X

Finally, VHDL implementation gives these result:

But it catches "110" instead of "1100". When I implement same state diagram using case...when structure, it gives correct result but I have to use logic gates & JK flip-flops.

How should I change this design? Is there something wrong or something I missed?

EDIT: I need obtain functions JA, KA, JB, KB (which are inputs of JK flip-flops) in terms of present states A,B and input sequence X.


texts: Inverting output of gate driver for MOSFET

texts:
I am using this circuit to control the speed of a small motor (12VDC, 0.3A).
The arduino PWM output saturates a 2N2222 NPN transistor which saturates the mosfet gate.

My issue: when PWM is high (5V), the output is low at the mosfet (0V = motor stopped). So when my controller starts up, the motor is running until the code applies the max value to the PWM output to shutdown the motor.

What I want to achieve: PWM high (5V) results in output high. instead of "PWM high (5V) results in output low".

I could solve it using an opamp to invert the signal but there must be a simpler way?


texts:
I'm using the TLC5926IPWPR in a design. It uses an SPI interface. The TLC5926IPWPR chip is on a separate PCB than the MCU that is controlling it. The Clock and SDO pin must go through a cable about a 1ft long. I want to clock this as fast as possible, and I wanted to get an opinion on my clock signal. The cable is affecting it quite a bit and I wanted to make sure I meet the minimum requirements, as this design will go into large quantity production and I don't want 1 in 1000 units to loose a bit or something.

Also note that I have two of the TLC5926IPWPR cascaded.

From the datasheet:

Here is my clock without the cable from the MCU IO pin:

Here is my clock with the cable (Measured at the end of the cable):

If I measure the time between the threshold of 0.7*Vdd and 0.3*Vdd, I get about 18nS. Is this the right way to measure the clock width requirement? It's the same time if I measure from 50% of Vdd as well.

Questions:

1) If the max clock is 30MHz, why is the min clock width 20ns? Shouldn't it be (1/30MHz)/2 = 16.67ns or less?

2) My clocks rise time is well under the maximum, but what about the clock width requirement of 20ns min? Is my clock sufficient?

3) Any ideas on how to clean this up so it matches the requirements better at 30MHz?

4) Can I put a schmitt trigger or something that could clean the signal up from the MCU to meet the requirements at the end of the cable?

The chips are working great as is and I don't see any issues, but one or two units is hardly a valid test of that.


texts: How to measure the voltage over a transducer? aka how to measure ultrasound

texts:
I want to measure ultrasound.
For this task I bought a sensor, and an instrumentation amplifier.
Apparently it doesn't work the way I thought because when I test it with a sample 40 kHz wave as input it does not get amplified but only phaseshifted or distorted when I adjust Rg (R Gain).
Shematic where ie(t) is the sensor.

Should I use a specific shunt? At the moment its just a 100 ohm resistor
What is a normal value for Rg? I tried it with a 250 kohm potentiometer but no value in that range helped.
Am I using this instrumentation amplifier in a wrong way?


texts: Using PP film or PET film as active filter stage capacitors

texts:
How to compare PET and PP film capacitors for active low pass filter stages? If I implement an active filter which film capacitor is more temperature stable? I guess temperature might vary the capacitor capacitances hence the filter characteristics. So Im wondering which type is safer to use in this respect. Is there a convention to use a specific type?

More specifically here is a KEMET 47n PP type cap: https://eu.mouser.com/datasheet/2/212/F3301_R79-1103144.pdf

And here a KEMET 47n PET type:
https://content.kemet.com/datasheets/KEM_F3101_R82.pdf

Im stuck which type would be suitable for such application. From the data-sheets where should we look at?  Does anybody have experience?


texts: How to calculate ripple/smoothing cap for vintage motorcycle LED headlight conversion

texts:
New here. Very little EE background but am tinkering with a project that has so far been nicely straightforward. However I've run into a real snag.

I have a few dozen links so it's just as well that I cannot post them as a new member or it might overwhelm.

1980 vintage motorcycle.
Separate lighting and ignition coils.
Nominal 6v system generates 4vac ~ 16vac in the RPM range.
Maximum power from lighting coil is 27watts.
Ac cycles vary along with voltage @rpm. I cannot yet find a source for that ac cycle range. Headlight is presently 6v 21w incandescent; anemic orange at idle, and almost useful at full RPM.

What I'd like to do is take fullest advantage of what little is on tap here to power paralleled LEDS.  So far, all from Digikey's site I've received....

rectifier
GBU10A-BPMS-ND

regulator
NE12S0A0V06PNFA

SMD LED (pair)
XMLBWT-00-0000-000LT50E4CT-ND.

I'm now left with two calculations that are beyond my rudimentary electronic skills. How can I calculate the largest number of those LEDs, wired in parallel, before I run up against the 6A limit of that regulator?
And, apparently, the toughest of all, the calculations for an optimum ripple/smoothing cap on the rectifier are so far beyond my abilities that I'm reduced to begging for someone to help me select one from digikey.

If discovery of the the ac cycle range is needed, and cannot be determined from the owner's manual itself (I can link to it), I will find a way to determine it if it's necessary.  MY DMM doesn't do Hz, but can't it be calculated by
simply counting the number of coils in the lighting coil and multiplying them by the rpm range from lowest to highest? Maybe a little added algebra?

Thank you very much for any consideration of this.


texts: Is there a way to check if semihosting is enabled at runtime

texts:
The ARM Cortex cores has a built-in feature called semihosting which is a way to interact with the attached debugger, for example to do printf() debugging without using a peripheral unit.

However, the implementation of semihosting is to execute a BKPT instruction. If the semihosting is not enabled this will result in a  DebugMonitor exception. Is there a better way to check if semihosting is enabled other than catching the exception? The annoying thing is that executing the BKPT instruction will halt the execution when the debugger is attached and I always have to press continue after every flash and restart.


texts: I have wired up 4 Raspberry Pis in parallel, each being activated by its own SPST toggle. The circuit is being powered by a 5V 5A switching power supply. Each time I power on a pi after the initial, the previous active pis show a slight blip in the onboard power LED. I can not detect a voltage drop when I activate each additional pi and 5A is overkill on available current. I am not sure what will help this issue as I am very much a hobby level tinkerer. See attached schematic. Any ideas would be greatly appreciated.


texts: Is integrated circuit packaging copyrighted/patented?

texts: A friend of mine is interested in manufacturing ICs. He wants to know whether the different form types of packages (DIP, LGA,  BGA) have intellectual property obstacles to using them. If so, who owns them and how are royalties paid?


texts: MPU6050 with STM32 reading axes X,Y,Z values problems

texts:
I have an STM32F303 Discovery and I want to use the I2C bus to receive the x,y,z data from an accelerometer MPU6050. Does anyone have source code for this? The problem is that the address of the buffers (i2cBuff) are 0, and the Xaccel, Yaccel, Zaccel too.

Here is my code:

#include "main.h"
#include "stm32f3xx_hal.h"

/* Private variables-----*/
I2C_HandleTypeDef hi2c1;
uint8_t i;
uint8_t i2cBuff[8];
uint16_t ax,ay,az;
float Xaccel,Yaccel,Zaccel;

#define mpu6050Address 0xD0

int main(void)
{
   HAL_Init();
   /* Configure the system clock */

   /* USER CODE BEGIN 2 */
   for(uint8_t i=0 ; i <255;i++)
   {
       if(HAL_I2C_IsDeviceReady(&hi2c1,i,1 ,10) == HAL_OK )
       {
          HAL_GPIO_TogglePin(GPIOD, GPIO_PIN_12);
          break;
       }
    }

    /* USER CODE END 2 */

    /* Infinite loop */
    /* USER CODE BEGIN WHILE */
    while (1)
    {

       HAL_I2C_Mem_Read(&hi2c1, mpu6050Address, 0x3B, I2C_MEMADD_SIZE_8BIT, &i2cBuff[1], 6, 10);

       ax = -(i2cBuff[1]<<8 | i2cBuff[2]);
       ay = -(i2cBuff[3]<<8 | i2cBuff[4]);
       az = -(i2cBuff[5]<<8 | i2cBuff[6]);

       Xaccel = ax/8192.0;
       Yaccel = ay/8192.0;
       Zaccel = az/8192.0;
      /* USER CODE END WHILE */

      /* USER CODE BEGIN 3 */

      }
      /* USER CODE END 3 */

   }


texts: Why does holding my car's RF remote to my head extend its range?

texts:
I'm in my parking lot and just a little too far from my car for the remote to work...  But if I hold the remote up to my chin, and then suddenly it works.

It sounds dumb until you try it, but it definitely works, with lots of different remotes/cars.  I assume it has something to do with the capacitance of your head, but I don't understand the details.


texts: Building a UHF RFID Reader, FCC regulations?

texts:
I've been working on a project that involves tiny UHF transponders (ex. OMNI-ID Fit 220) that fit into a product with very limited space. We wanted to build our own reader (5 or 6 of them) because it's cheaper, easier to integrate into our system using a reader board and a little Arduino, and we can utilize the reader for our application better. We aren't exactly electrical engineers but more hobbyists as the place we work usually like to build everything in-house so that's why we went this route, we have access to everything possible to build one ourselves. We had very poor read results and reliability with the Sparkfun M6E Nano, so we abandoned that module. So I brought in some evaluation kits (Impinj RS1000 and STI) We were really happy with the Impinj development board but Impinj is telling us we need FCC approval and UL certifications to build our own device. Is this correct? To my knowledge I thought as long as we didn't exceed 1 Watt in TX power and move out of the UHF frequency range here in the FCC we would be fine to use our small batch of devices, we wouldn't even sell them.

The readers we have seen are around $1000+ or USB desktop readers but cheap. If we 3D print our own cases and build them ourselves our costs would be only ~$300-$400 per device.

Do the FCC regulations stop us from building our own reader device? Do we have to get approval that doesn't go over 27dBm? I can't exactly find anything saying so.

Am I missing something bigger?

Thank you!


texts:
I am having this MAX9278 deserializer IC.
The input to the pins +IN and -IN is a twisted pair input and therefore, it is a differential signal. I have configured the CX/TP pin to low since it is a twisted pair input to IN+ and IN-. I hope this is correct. (Referring table 10).
My question is,
I have interfaced the above deserializer with a 3.1 inch TFT which has a resolution of 800 x 480 pixels.
IN+ and IN- twisted pair input and 4 LVDS Channel output and a LVDS Clock output to the TFT.
My frames per second requirement is 60 and blanking is 20%.
In that case, according to this formula from Maxim, my PCLK,

My Calculation:

Question 1: Whether the calculation of my PCLK is correct? If it is correct, will all the LVDS Data output channels also be going to the TFT at 27.6MHz?
Question 2: From where does the 27.6MHz is generated. There is no crystal which is connected to the deserializer. However, there are 2 blocks as marked below.

So, does the blocks generate the clock or does it take the input IN+ and IN- and perform clock data recovery (there is no mention of clock data recovery in the datasheet) from the IN- and IN+ data and provide the same to the LVDS outputs? Which means that I need to send my signals IN+ and IN- at 27.6MHz? Am I correct?


texts: 433 MHz transmitter works only when I touch a specific part

texts:
As it is hard to describe, I made a small video showing my issue:
https://vimeo.com/521857517
As you will see, the RF transmitter and receiver are correctly connected as they work when I touch a specific part on the transmitter.
If anyone could help me understand what is wrong (and how to fix it), I would really appreciate it.
I also tried connecting a 100K resistor to it (with electric tape for now) and to ground and it works as well...
I’m using a 1M resitor on the encoder and a 470K on the decoder... could it be the problem?
Thanks


texts: AVR and STM32 ARM GPIOs state when IC is unpowered

texts:
I'd like to make a device combined two controllers: ATMega64 I already familiar with and ARM Cortex-M0 STM32F051 I'd like to be familiar with.

I'd like to directly connect GPIOs of two controllers. I hope that I will be able to choose which controller is now operating just providing the power to the one I need.

So the question is: if one of the controllers is unpowered will it's GPIOs interfere with GPIOs of powered one? Can I assume that all GPIOs are in Z-state while controller has no power?


texts: Altium designer: GND plane Polygone does not reach a vias array

texts:
Here is what I always get :

And here is what I want to have:

I never had such an issue with my old PC, now that I changed the PC I start having bugs like this. What can I do to solve the issue, any suggestion from you would be great.

Thank you


texts: I am trying to convert my old 9V battery operated Wah-wah pedal to a DC converted one, so I can use AC power.  I bought a DC plug for it and was told that the center pin is for ground.  However there are TWO additional pins.  I only expected one since there's just a positive and negative wire.  Which pin on the DC plug is for the positive wire?  And is it true that the center pin is for the negative wire?


texts: How is the ability of a single charger to charge a range of types of mobile phones achieved?

texts:
Chargers that are supplied with eg an Android phone can be plugged into some other non-Android type phones and charge them successfully.

How is this inter-brand and inter-system charging possible?

A typical connector used in such systems looks like this -

Note: The link to the connector image was in the original post but did not show - presumably due to the OP's rep level - RM


texts: If the switching frequency is increased for BJT what happens to the power dissipation? Will it increase, decrease, or remains the same and whats the logical reason for it?


texts:
I have a differential signal ranging from 0 to 2 MHz and need to transform it into a single-ended signal.

I found out that there are 3 methods:

Transformer
Amplifier
simply ground the negative part with a matching load

How can I decide which method to use? I mean I would just take the load-to-ground method but I guess it's not that simple to decide.

Edit: The transformer method would fall out, because DC cannot pass, although this would be no problem.


texts:
I have a device that can be configured to maintain a specific bias voltage on the output. How should I verify if it actually generates that specific voltage?

I do not think I could simply use a multimeter to measure that voltage. Instead, I thought I should use a resistor on the output of that device and then measure the voltage across it. Is that necessary?


texts: That is the value of Ri, Ro, Voltage amplification

texts:
Can someone explain what is happening in this circuit please?
I am asked to determine the amplification Au = uo/ui


texts: Why some LM25xx DC-DC adjustable step-up converters have two negative connections (IN- & OUT-) instead of only one ground?

texts:
Recently I came across several 4-pin LM25xx DC-DC adjustable power converter modules such as the ones below.

LM2577 Adjustable Step-up Converter Module from Amazon.com
DC-DC adjustable step up power converter module from HobbyKing.com

They look like this:

I'm only familiar with similar 3-pin LM25xx modules that only have one ground connection, such as these.

Murata's OKI-78sr
Murata's 78xxSR Series

They look like this:

I searched the Net trying to find a datasheet for any of the 4 pin modules, and found none. Unlike the 3-pin versions that have plenty of good quality technical information in their datasheets.

So, my questions are:

What are those IN- and OUT- pins for?
Can I just short IN- and OUT- to ground and use the 4 pin modules like the 3-pin versions?

The context for my question is this other question (which is currently on-hold) and the fact that I want to design one of such modules myself and wanted to broaden my options.

Also, I realize that the 4-pin modules are adjustable while the 3-pin modules are fixed output. But I don't understand what that has to do with the differences in the number of negative pins. From the application notes from the adjustable versions of LM25XX, such as below, I cannot imagine how IN- and OUT- pins would be wired up. To me, the only option is to provide positive input and output and a connection to ground.


texts: Complexity comparison of an adder and a multiplier

texts:
I have two algorithms with different requirements of addition and multiplication operations as follows:

Algorithm 1: 100 additions 200 multiplications, total = 300 operations.
Algorithm 2: 300 additions 50 multiplications, total = 350 operations.

Algorithm 1 requires least number of operations, but most of them are multiplications which according to my basic understanding, is more complex operation than the addition in terms of hardware implementation (FPGAs, ASICs, DSPs). Algorithm 2, however, requires 400 operations, but requires less multiplications. My questions are as follows:

Is algorithm 2 better than algorithm 1, given this information.
If algorithm 2 is better, is there a systematic way to establish this result. One method in my mind was to give weights to multiplication and addition, e.g., w_addition = 1 and w_multiplication = 2 and then calculate the total number of operations, but I am not sure if this is the regular practice in algorithm design field. If there is a systematic way of doing this, can you please give me some references to quote in a paper.


texts: What is the energy density of voltaic piles?

texts:
I heard voltaic piles have very small power but long lifetimes so I was wondering what their energy density per unit volume and energy density per unit mass is. If specifying a type of voltaic pile helps then I choose zamboni pile.

I had trouble finding numbers online. What I know is the voltage of a unit cell is ~.8, current in nanoampere range, the oxford bell has been on for more than 100 years. But I'm hesitant to use the oxford bell because it doesn't discharge a continuous current. I was able to calculate a five penny battery contains about 1 mWh but I feel like there are more efficient voltaic piles than it.


texts: Ruggedizing a component for extended temperature

texts:
I am doing a system design presently which involves an OEM optical amplifier module (Dimensions: 220 x 250 x 60mm). It has got an operating temperature range from 0 deg. to 40 deg.C. However, my system is supposed to operate all the way from 60 deg.C down to -30 deg.C. The support personnel for the component informed that it can be ruggedized to make it operate in the required temperature range. Does anyone know how the ruggedization can be done?

Update
After testing the module, we have found that it can operate till 60 deg. C without any issues. Hence cooling mechanism at high temperatures is not required. All I need is a heating mechanism which can heat up the module when it goes to negative temperatures. Which type of heater will be best suited for this application? My system has a 28V DC input and I will have to heat up a face with 220mm x 250mm area.


texts: How to make falling time shorter for mosfet switching for high voltage and high frequency ultrasonic pulser

texts:
I have a case that I need to build a pulser switching for my ultrasonic transducer which operate in 180 V and 1 MHz. I use mosfet IRF250 for the switching, and below is the circuit:

This is pretty good with response like this:

The green is input signal and the blue is output signal in the load, the problem is R1 resistor just 100 ohm, and the power needed will be 324 Watt, I want to reduce the power since the transducer only uses the voltage not the current, so I raise the resistance of R1 to 10K so the power will be 3.24 Watt, but the response is like this:

The falling time is increased drastically, what causes this ? Is it the capacitor between drain and gate inside of mosfet? How can I change the R1 to 10K but with same response as 100 ohm?


texts:
I am not normally into electrical projects or engineering so forgive my ignorance...

I am working on a project that would involve a couple dozen electrical contact switches.  I want all these contacts to be wired together in a central circuit board.  When any of the electrical switches are closed...make contact...the circuit board will detect this and send a signal via Bluetooth to my Macintosh.  The signal would differentiate which of the switches made contact.  My Mac would process this incoming data with custom software that I write (the custom software part I know how to do).

Are there any devices or components out there that will do this without a lot of work?

Thanks...MDCragg


texts: Thermopile (ZTP-135SR) Circuit Diagram Question

texts:
Is \$V_\mathrm{th}\$ being inputted into/through (as a junction/node) negative thermopile lead? (See Schematic with highlighted section)

I'm confused to why you would need to amplify \$V_\mathrm{th}\$ (Voltage of thermistor).
I understand you need to amplify for Vthermopile, since the voltage is very small.

I appreciate any help.
If you need any more information let me know.

Edit 1: The thermistor is used to measure the ambient temperature. I believe to solve for voltage out the thermopile you use
$$
V=S(T_\mathrm{tmp}^B-T_\mathrm{th}^B).
$$
The thermistor for this model is inside the thermopile. As far as I know, the thermistor and thermopile have + and - lead (Four leads total).
I believe Vth is just a reference value.
I'm not sure if that is correct to say that.

Edit 2: According to the circuit diagram on the datasheet, the thermistor voltage will be amplified. I'm not sure that's necessary for all thermopile models.

Thanks!

Data sheet for reference: https://www.mouser.com/datasheet/2/18/AAS-920-159D-ZTP-135SR-031314-web-1315865.pdf


texts:
If we have a circuit in dynamic logic:

What should the size of the charge transistors (Qe and Qp) be? I know that increasing the size improves the speed but also increases the dissipation, and that it doesn't affect the functionality.

If the highest transistor width of my pull-down-network (PDN) is \$N\cdot\lambda\$, should my size for charge transistor be something like: \$f(N)\cdot \lambda\$ ?

Thanx!

P.S. Image reference: Sedra, Smith - Microelectronic Circuits


texts: How to determine what capacitance is required for eliminating humming noise?

texts:
I've got power supply (transformer based) 9V powering modelling guitar effect processor. That noise gets amplified and it hurts.

Humming noise is 100Hz rectified mains. Processor takes 300mA 9V (500mA rated). Unfortunately I cannot tell ripple voltage (don't have an oscilloscope).

Is there any equation for calculating capacitance needed to eliminate the noise?

When I was studying step-up/down switching regulator IC datasheets, I saw the formula: coef**current*time_on/Ripple_voltage. But is contains coefficient, which is different from datasheet to datasheet.


texts: When using emergency stop buttons and kill switches, are they designed in such a manner in which their role is more physical, such as interrupting a power supply (apparently in some of the models, like the one pictured, the button has to be turned before operation can resume), or are they just basic big red pushbuttons that are simply coded to wait until they're pressed.


texts:
This is a little bit different question than normal..

Aliexpress is ruing my life, sometimes i order things i don't even need because it seems cool. A few time ago I ordered 500x 555 chips for just a few bucks, haven't used one.

What cool project could I do with so many 555 chips? I'm open to every absurd, stupid, usefull and non-usefull or original projects.

Maybe a predator style giant clock? https://www.youtube.com/watch?v=UyBwKHCtgm0

Or maybe just a random LED blinking matrix with nothing usefull.

Open to every suggestions :)


texts: Are there disadvantages to this method of testing building wiring after a lightning strike?

texts:
A lightning strike can damage wiring in a building. Specifically it can damage the insulation on the conductors, resulting in arcing and fire, either immediately or some time after the strike.  I've seen insulation testing conducted after such a strike. This involves opening each breaker, disconnecting every load, and putting a voltage on the circuit to see if the insulation breaks down.  For a structure of any size, this can be very time-consuming.

I can imagine an alternative: simply replace all breakers in the building with arc-fault interrupt breakers.  If any arcing is happening, or starts after the fact, the breakers will trip and prevent a fire, and give a strong indicator of what circuit the damage is on. It almost certainly costs less than insulation testing every conductor, and while it's not the same kind of testing, it's a very effective test every second for the rest of the life of the structure. Plus it helps bring the building up to code, especially if you install breakers with GFCI capability as well.

Is there a reason this would be a bad idea, from a technical or safety standpoint?


texts: I want to detect light near 10 micrometer wavelength. It seems like photodiodes are mainly targeted for 1 micrometer range. Is there any detector/sensor for 10 micrometer wavelength ?


texts: How to determine Resistor values for PNP transistor

texts:
I am trying to use a PNP transistor as a high-side switch, as shown here:

How would I determine the values for R1 and R2? My circuit has a 12V battery connected as shown, and an Arduino digital pin connected to R1. my load is just a resistor and an LED to ground. The transistor I am using is this. The load needs a maximum of 140mA.

A few more questions I have regarding this circuit is:
 1) Do I need a diode between the Arduino and R1? It seems like when I hook up the pin without a diode it is constantly on no matter what, even when the Arduino pin goes HIGH.
 2) Since the 12V line for now is connected via battery, when I shut off the Arduino the load doesn't turn on but the LED I have in series with the Arduino and R1 does turn on. Why does it do this.

Many of these questions come from a misunderstanding of PNP transistors, so I am sorry for that.

Thank you in advance.


texts:
I'm in the UK and want to replace the connector on my lawn mower. I see you can buy products like this that state they can be used for garden equipment. However, the connector can be plugged in either way, so internally it could have one side with the live connected to the neutral and the other side with the neutral connected to the live?

From what I have read, this is not a problem. If it isn't a problem, then why aren't all plugs able to be plugged in either way?


texts:
In the Q/A link below, the circuit in the answer seems to be wrong to me.

Answer to "How to gradually light up an LED?"

Circuit:

simulate this circuit – Schematic created using CircuitLab

In my point of view, after you turn on the power to that circuit, transistor is immediatelly ON, what means that LED is immediatelly ON, and it will be OFF after some time elapsed when capacitor will be charged enough.

Am I wrong?


texts:
For a N-channel Mosfet does Vds = Vdb + Vbs? Is this only true for simple models or always?

Where d is drain, s is source and b is base.


texts: How to calculate, *for a square wave input*, the cut-off frequency point for a basic RC low pass filter with

texts:
I am applying low pass filter for a pcb circuit I am trying to design (picture below).
I have managed to calculate the cutoff for a sine wave input since I can insert a frequency (i.e. f_c = 720 Hz ) and get RC out of the equation:
f_c = 1/(2*\pi*RC).

My question is:

  How to do the same analysis as above (i.e. finding cutoff point) for a square input. I mean, what should I insert as f_c? doesn't square wave contain all frequencies?

I need to know how my circuit will behave with square input. What will be the time delay created by the filter under different square-wave inputs.

Thanks!


texts:
I have a Panasonic A6 servo driver paired with Velocio Ace PLC. I am trying to read servo motor status. I followed the wiring diagram from the servo manual and connected the PLC digital input to Servo's digital output. However, I am not getting any reading. Below is my wiring diagram (Please ignore the DB9 stuff) :

And here is the PLC digital input information:

Ace Digital Input

Here is the Panasonic A6 information

Panasonic A6

Basically I need to read the S-RDY, INP, and ALM output from the driver. Can somebody please point me to the right direction?

Is this the right way of wiring it? If yes, what resistor value and size should I use?


texts: What does a large capacitor do in small signal analysis?

texts:
I keep having to look this up. It seems as though I have yet to find a great way to understand this.

In small signal analysis:

What is the difference between a large and small capacitor?
What are they modeled as?
What is a good way to remember it?

Further more detailed question:
If a large capacitor was connected to both terminals of a resistor, would this essentially short circuit the resistor in small signal analysis?

Thanks, This class is difficult.


texts: Quartus II Error (18994): configuration scheme "passive serial" is not valid for the device

texts:
I'm trying to synthesize a System Verilog design into a Stratix 10 device using quartus II v.17 but keep getting the following error.

  Error (18994): configuration scheme "passive serial" is not valid for the device

All my top-level ports have been assigned VIRTUAL_PIN ON as this is just a small part of a larger design and I just want to see if it synthesizes. The error occurs for all Stratix 10 devices.

What is causing the error and how do I fix it?

Thank you.


texts: Can this WWII era rheostat be modified to dim an LED bulb?

texts:
I have a WWII era RAF chart-board lamp in perfect unused condition. I want to use an LED bulb with the original dimmer as tungsten runs so hot. I want to avoid rewiring or bypassing the dimmer as the original cabling is in such good condition.
The fitting for the bulb holder is BA15D, so I am limited in the range of 24V LED bulbs available.
The dimmer specs I can find are as follows:

Ref 5C/726 type G
Primary use: Chart-board lamp, 24 volt, 10 watts
Total resistance: 50 ohms +/- 5%
Number of turns each side: 95
Wire: 0108 in. enameled eureka

How can I choose a bulb that will work?


texts:
I have an 800 Hz square wave and would like to generate other frequency square waves from it: (100, 200, 300, 400, 500, 600, 700) Hz.

I'm aware of "divide by 2" frequency division, but how would you do something like divide by 7/8?

I plan for this project to be made from ICs (no programming). Chip suggestions are welcome :)

(Alternatively I could go from 100 Hz to the other frequencies, or go from 500 Hz, ect. I just need all of them present as outputs.)


texts: illegal reference of a signal during a static elaboration, vhdl

texts:
I have an entity inside such entity is declare a component, and of course i need to set the port map in the component.

basically i've done something like

port map (x => '0' & signal_id, ...

let's say that
x : in std_logic_vector(n - 1 downto 0)
while
signal signal_id : std_logic_vector(n - 2 downto 0)

so basically i wanted to perform a mapping of a signal sized n - 1 with a signal of size n, so i tried to perform a padding adding one zero. However when i try to run ncvhdl it says:

port map(x => '0' & signal_id,
                                |
ncvhdl_p: *E,ILSGRD (test.vhd,159|32): illegal reference of a signal (SIGNAL_ID) during static elaboration [12.3].

what's the meaning of static elaboration in this case?
i've tried to check if there was a syntax error, however from the ashenden book i've seen that expression as mapping in a port map is legal.

Can anyone explain me what's happening?


texts: One master to 32 slave pic microcontroller communication, bitbang

texts:
I'm trying to communicate with 32 microcontrollers (PIC 12f675). These are used to control 32 DC motors and 2 sensor for each PIC. So only two pins are left to communicate with master device.
I want to send signals (how much rounds to rotate and direction) to these 32 slave PICs in one master device.

PIC 12F675 hasn't I2C or SPI hardware. So I want to communicate with some bitbang technique. (PIC 12F675 running at 4 MHz internal clock)

What is the best way to do that?
(I prefer to use C language (xc8))


texts: RS232 Serial Console: Do we receive serial packets at serial pin out from CPU even we don't have the console cable connected?

texts:
What if I don't have the serial cable connected to the serial port, still I receive serial packets from CPU? (lets say console output is enabled in Software)
Will those packets got terminated (discarded) at the serial port connector end at board?


texts: Becoming crazy with EU LVD regulation in PCB and electric strength

texts:
First of all I will explain the design characteristics of my project to make clear what it is and where it enters for regulation.

It is a fixed electric/electronic installation in  offices so it can't be moved and the PCB board size has to be the smallest possible, it has plastic envelopment around all the product and earth and GND are tied (it has an isolated AC/DC power supply), and in theory the electronic's space is waterproof, and the user can't touch anything, it's all Ethernet-controlled.

So my doubts started when I had to implement the normative  EN-60335 about electrical security in home electrodomestics and the IEC 60664 for insulated systems (coated PCBs) which are the ones I assume I have to apply into the design.

The problem comes when I want to use this connector to carry  2 comms wires (serial 485), isolated logic power (+12 V, GND-Earth) and 230 V AC (line-neutral) (I know it shouldn't carry all in the same connector but it was a design requirement :palm:):

https://www.digikey.com/product-detail/en/molex-llc/1723101106/WM11592-ND/5344289

In theory the electric strength of the connector is about 1800 V but some electric test are about 5 kV peaks in the normative, so one of my doubs are about the varistor, at the AC entry, shouldn't it shortcut when the peak tries to pass it and then the connector shouldn't be affected?

In coated boards which is the minimum clearance and creepage between Line, neutral, earth and low voltage lines for this kind of product?

Can the connector and electronics be filled with some kind of plastic isolator to upgrade its isolation capabilities?

Thanks for your time.

I have already posted this in eevblog but I dont know what else to do (ok I can read the normative for four time :) ).

Also I have seen this thread but it didn't solve my questions:

Creepage distance for PCBs handling line voltage AC?


texts:
I was trying to build a circuit that if switched on would slowly (in span of of 1~5s) light up around 20 LEDs - progressively, not all at once.
To achieve that i used one capacitor to initiate the "build up" effect (and discharge when switched off) and then used NPN transistor's emitter as a base input for next transistor, as shown on diagram below.

It works but with each consecutive "part" the light is dimmer and fades out completely after 3rd LED. Which leads me to suspect that power on base of transistor is getting weaker - but it shouldn't require much to let power through.
Transistors i have used are BC337-25.
Resistors vary, i was experimenting with different ones but R1 is 1.5k Ohm, R2 is 100k Ohm, resistors between emitters and LEDs are 220 Ohm, and one between emitters and bases are 1k Ohm
As for Voltages, both inputs are currently 3.3V, but final version will be charged off one 3.9V 18650 battery.
The question is: is it possible to achieve that gradually lighting up effect (similar to "percentage charged") with this design, and if yes what is the problem with my design?
Note that while I only have some understanding of a topic I did my research around the Internet was unable to find good enough resources that I could apply to my problem.


texts: Ground versus negative terminal in a data sheet

texts:
In the following datasheet.

At some point it says : "If the option for synchronization is not used, the synchronization input has to be connected to ground (0 V) or the sensor must be operated via a V1 cordset (4-pin). The synchronization function cannot be activated during programming mode and vice versa."

Is ground (O V) same with -Ub (negative terminal of the power supply)? I'm kind of confused why they use different terminology.


texts: Can I just connect two CR2032 batteries in parallel?

texts: I'm designing a device with a small current draw that will mostly sleep in a very low power mode and I need to use button cell batteries due to a limited thickness. I would like to double time between batteries needed to be replaced by using two or more CR2032 batteries connected in parallel, can I just connect them in parallel directly or do I need additional circuitry to prevent charging or discharging one battery from others while the device is sleeping?


texts:
I'm trying to improve the range on my 433 MHz radios that are using the CC430F5137.

Based on 25.3.3 in http://www.ti.com/lit/ug/slau259e/slau259e.pdf, it seems like decreasing the RX filter BW can improve radio sensitivity. I looked over TI's DN005, DN015 but I didn't see an explanation why this was the case. Common sense tells me that if you're listening over a larger spectrum, the radio has less time to distinguish between signal and noise. But that's not a satisfactory scientific answer, is it?

Based on (3) in http://www.ti.com/lit/ug/slau259e/slau259e.pdf, decreasing the baud rate helps radio sensitivity as well. Again, this makes sense since there is more time for each 0 and 1 to transmit over the air. Is there any scientific explanation for this as well?

I guess the other question is if the baud rate is related to the RX filter BW. Or are they completely orthogonal concepts?


texts: What is a suitable temperature rise for PCB traces?

texts:
I'm designing a PCB for a 10A relay and am trying to determine what the trace width should be.

According to this trace width calculator, the biggest factors in the width are copper thickness, maximum current, and temperature rise. I would like to use 1oz for the copper thickness since that makes the PCB cheaper, so that leaves temperature rise as the most desirable variable to change.

Using the above calculator with these settings:

Current: 10 amps
Thickness: 1 oz/ft^2
Temperature Rise: 10 C
Trace Length: 1 in

The calculated trace width is 283 mils, which is too wide.

If I change the Temperature Rise to 100 C, the calculated trace width is 70 mils, which isn't bad at all. However, I don't know what kind of temperature rise is acceptable. How do I determine this?


texts:
I have a USB type A to type B cable, I took it from a printer. Now, I want to utilize this USB cable to make a 5V breadboard power supply. I will cut the cable and connect power lines to breadboard's power rails. But, I can't be sure if it is guaranteed to have cables for power transmission or not. I mean, I don't want to ruin the cable if it cannot be used to transmit power.

So, I am sure (well, almost) that there are data lines in the cable, because it was used to transfer data between computer and printer. However, printer had its own power plug. Thus, I am not sure whether this cable has a power line or just data lines.


texts:
I'm studying the inverter with active load, whose circuit is the following:

The circuit is simple: the current mirror fixes the source to gate voltage of the PMOS, thus the plot of the drain current of M2 as a function of the source to drain voltage of M2 is univocally defined.
If vin increases from 0, we will get all the possible curves of the drain current of M1 as a function of the drain to source voltage of M1, each depending on the particular value of the gate to source voltage (i.e. vin) of M1.
The intersection of the characteristic of M2 with a characteristic of M1 gives the operating point, as illustrated in the following picture:

In the previous picture, the drain current of M1 (and M2) is a function of the drain to source voltage of M1.

Question: how does the author of my book represent the PMOS characteristic (in which the current is a function of the source to drain voltage of the PMOS) in the same plot of the characteristics of the NMOS (in which the independent variable is the drain to source voltage of the NMOS)?

Thank you


texts: A mobile power source for a laptop and a projector

texts:
My friend has asked me to do some marketing for his student targeted company. The hope is to create a good animation/flash video and project this (at night) inside the student campus onto the building. I saw a decent instructable here http://www.instructables.com/id/PROJECTION-BOMBING/ but this method involves a car/car battery. We need something more mobile as we will be situated inside the campus.

Could someone please suggest what power source I could use that would allow me to plug in the laptop and projector. Also could anyone suggest a good affordable projector?

THanks in advance


texts: Why there are AC timing characteristics but not DC in I2C interfaced chip?

texts:
I'm quite newbie in electronics, and I'd like to learn why there are AC timing characteristics to this particular
EEPROM (24LC512) that I'm using but none for DC?

Does AC timing constraints apply to DC as well?

If not so, do I need to obey any timing constraints in my design if I
were to use I2C bus with DC power supply for this chip?


texts: Why is it required to use a register in the final stage output of a pipeline?

texts:
I'm following MIT 6.004x course, where in the pipeline section, it's stated that "our pipeline convention requires that every pipeline stage has a register on its output". I absolutely understand the reason to add a register in the mid-stage, but why to use it in the final output wire. I mean, can't we just pipe the output directly, what's the purpose to add a register to remember the output result?

For example, I have the following pipeline conforming to the aforementioned convention:

why can't I delete the last register and output the result directly?

Could anyone give some explanation? Thanks for any help!


texts: Thickness for polyimide stiffener in flex pcb

texts: I'm struggling to find some guidelines for the thickness to specify for a polyimide stiffener under a surface mount connector on a flex board.  I see lots of call us and we'll help you figure it out but no guidelines or explanations.  I want to use one under a small 20 pin surface mount connector both to keep things flat for assembly and to provide some relief for multiple removal/insertion cycles (100 or less).


texts: This circuit doesn't use a gate drive, so I am trying to understand how it can output 25kHz. A friend of mine told me that it does so with the use of LC resonance; the capacitor and inductor next to F1 and F2 achieve resonance as per the formula $$f = \frac{1}{2\pi \sqrt{LC}}$$ but I still have my doubts...


texts: What does the "posted" mean in posted PCIE transaction?

texts: What is the etymology of the word "posted" in "posted PCIE transaction"?  I've worked with PCIE and I understand the difference between "posted" and "non-posted" PCIE transactions, but I don't understand what the word "posted" means.  Where does "posted" come from?  What does it really mean?


texts: Convert AC to DC using Phase Shift Oscillator

texts: from what I know, we can convert DC to AC by using Phase Shift Oscillators. I'm able to pull off the manual calculations, but as for simulation on Multisim 14.2, I didn't get the desired graph(phase shifted). Maybe my understanding is wrong, so please let me know how can I make the following circuit to oscillate.


texts: Combine a low power XBee receiver with high power XBee transmitter in a model rocket

texts:
Have got some existing low power 2mW XBee series 2 with an Explorer that I've used successfully to communicate between a PC with the XBee Explorer and a remote Arduino based project.

I'd now like to create a one way link to send telemetry data from a model rocket with an Arduino based telemetry board that has a ZigBee option. I'm thinking I'd be able to get away with the existing low power XBee I have plugged into the XBee explorer as the base station to receive the data and just purchase a high power XBee with an aerial to mount inside the rocket.

Does anyone have any experience or comments about combining a low and high power XBee to create this one way link from the rocket to a base ground station?

I realise the XBee must be of the same series (1 or 2/2.5) to be able to successfully communicate.

The ones I currently have are these www.sparkfun.com/products/8691 and I'm thinking if I bought something like this http://www.littlebirdelectronics.com/products/XBee-Pro-50mW-Series-2.5-RPSMA.html# I'd be able to create a reasonably good distance link for a smallish model rocket to send it's telemetry data through.

One issue I'm seeing is that the transmitter may need to be in some sort of broadcast or no sync/acknowledge mode as the receiver would be low power and not be able to transmit data/acknowledgements back to the rocket to acknowledge data being received. It also may (given a very good flight) go out of range and so coping with nobody listening/receiving needs to be configured into the transmitter end.

Second, what aerial or version of the 50mw XBee would make sense to use in the rocket? The link to the one I've shown above requires an external RSPMA aerial to be plugged in. Assuming the combination of high to low power sending only would work, would this be the right aerial type to use being mounted internally in a rocket?

Or am I just trying to make this all to complicated and should ignore the fact that I have low power XBee modules now and buy 2 high power ones that I won't be transmitting from one with?

Thanks.


texts: How to calculate closed-loop bandwidth from open-loop parameters using feedback factor

texts:
I'm working through a past feedback analysis question for an exam and trying to calculate what the closed-loop bandwidth becomes given the open-loop gain \$|Av|=10^5\$, open-loop bandwidth \$B_{wo} = 20 \text{ Hz}\$ and a calculated feedback factor \$ \beta = 0.151515 \$. The class notes I'm given don't mention anything about how this works and neither does the textbook. From what I understand introducing negative feedback reduces the systems gain and widens its bandwidth? The answer given is that the closed-loop bandwidth becomes approximately \$303 \text{ kHz}\$. I initially thought to multiply the feedback factor with the open-loop bandwidth giving \$3.03 \text{Hz}\$, three orders of magnitude too small.

I have looked at this post  Closed loop bandwidth vs open loop bandwidth
but I would like to know specifically how to calculate the closed-loop bandwidth using this feedback fraction.


texts:
Using the GPIO on a BBB I'm attempting to detect a change in voltage coming from a DC source that drives a buzzer when the machines cycle is complete. I've located the DC connections from the machines control board to the buzzer. When testing + to ground I get 13.2V. When testing + to the buzzer I get 6v/6ma. When the buzzer activates it spikes up and down 5 times from 6v/6ma to 10v/20ma. So my question is how do I build a circuit using these two contacts that is reduced to approx 2.5v & < 5ma as to not blow out the GPIO?

I'm very new to this but based on searching the web my initial thought was a voltage divider, since it seems like a simple circuit to create that I can easily calculate the resistor sizes for......BUT I'm concerned about the spikes as the buzzer operates. In my testing of these contacts with my multimeter several times the meter indicated an overload.

I've also read about Triacs and thought that might isolate the spike but the problem is even when the machine is idle/sleeping the voltage between the + and buzzer lead is still 6v so the triac will never reset.

Thank you

Scott


texts: How can I implement a differential input for a logic analyzer probe?

texts:
I'm currently working on a project to build a portable logic analyzer. There will be 4 input channels to the design, however I was highly recommended to redesign this using a differential input to isolate noise.

So far, each input channel gets scaled for the ADC max. voltage of 3.3V and has a zener diode for current limiting.

Can anyone recommend a specific differential input IC or circuit to apply to my current schematic layout?


texts: Power transistor identification: old RCA

texts:
Looking for an alternative/substitution for an old RCA power transistor:

Google and old RCA catalogues did not provide any useful information.
Thank you in advance.


texts: Accurate methods to measure Energy in a RLC Circuit

texts:
I am looking for an accurate way to measure a RLC Oscillating Circuit's Energy.

I see for an Oscillator it is common, and some results produce a Parabola or close to it. See: http://www.physics.brocku.ca/PPLATO/h-flap/phys5_2.html

Can I do this with an RLC Circuit and an Oscilloscope? If so how is it done accurately?


texts: IC legs (VCCIO1) Broken Accidentlly of Xilinx XC2c128 CPLD is it working?

texts: This is the image of  My Xilinx Ic that leg name VCCIO1 that broken yesterday ......but I found in its datasheet that their is a same pin named VCCIO1  are present at that time I was happy but when I try to check Continuity test on it using Multimeter,then Multimeter not show any Beep when I try to connect both 73 No VCCIO1 to 55 no VCCIO1 PIN ......I suggest both are same but multimeter not is it true ? ........please help Friends....


texts: 5v relay module not working with dc adapter

texts:
I have a setup with a relay that disconnects mains voltage for a project.the problem i have is that the relay works fine when i connect it to the arduino and  power it from a laptop but i changed the source to a mobile charger with sufficient current rating it just keep turning on and off .i think that after turning on it keeps shorting as the arduino resets too i have also tried it directly by removing arduino and just powering it through the charger same thing happens. i have changed the charger once too . one thing to be noted is that i  tried another cell phone charger with output:5v and current :1A it worked with it .

(x)

** EDIT:** turns out it was my own mistake ,the input wiring for powering the charger were mixed with the relay . fixed now thank you all for the help !


texts: Is a 'timeout' of 0.2 ms for UART communication realistic?

texts:
In most examples (from Arduino/STM32/whatever) I see timeouts of 10 to 100 ms for different kind of communication.

However, I am wondering how much 'overhead' there is. Assuming I want to send 8 bytes (including stop bits + overhead, via RS485, 2.5 mbps), and getting a response back (let's say also 8 bytes). This would take: 64 bits / 2500000 bits/s = 32 us.

Now there needs to be some processing (interrupt handling) from both sides (sending + receiving). I'm using HAL which has some more overhead maybe, so let's take a huge 10,000 instructions. On a 72 MHz CPU this would take 10,000/72,000,000 = 138 us.

This totals less than 200 us together...
Do I miss something?

(note that I intend to use interrupts, and probably later DMA since it will even have less overhead high likely).

EDIT

Communication from an STM32F103C8T6 to another STM32F103C8T6
Both running at 72 MHz
RS-485 via UART, 2.5 mbps
There are no other higher priority interrupts (that can block UART)
Requirement: not hard, but preferably multiple messages within 1 ms.


texts:
Last week I asked this question attempting to find a solution to efficiently converting higher voltage to lower voltage.
From the answers, I arrived at TI Power Designer and I ended up with this schematic.

This is all well and saved me from a lot of trouble. However, some users suggested that the layout is a lot more important than the schematic, in creating a powerful (get it?) design.
Therefore, I looked at the datasheet of the IC and I started reading.
There was an example layout and some layout guidelines which I followed carefully. This resulted in adding two more bypass capacitors to the original schematic and a new schematic resulted:

After this, I started the layout for the schematic and I ended here:

This is fantastic and small, which was desired. However, I don't have a lot of experience with designing this kind of circuit so I am looking for feedback.
UPDATE:

Moved Rpg resistor lower as indicated by user1850479 in order to tighten the loop formed by the switch, inductor, capacitor. Really useful comment. This also makes the two components more  visible (Cvcc and Rpg suggested as a DRC error by the same user)
As suggested by Stiddily I tightened the feedback loop by shortening the connection from 5V to the resistor and I also highlighted the path so it's more visible. Note that this is on the bottom layer.
Removed the adjacent nets as it seems to have confused some users. Also tried to tag the components better in the layout (picture 3) so inferring from the initial schematic (picture 1) would be easier.

Are there any other improvements I could make to this? Is there anything I could do to make the explanation of this better?


texts:
Below is my circuit diagram. I want to on and off my two motors inside. However, I want to make circuit better and replace two Diode between TIP120 and Digital output. I want to change the relay to more common type as well. My motors are needed to switch on for around 2 hours.
What others thing should I change? Could you help me?

Thank you.

I updated my circuit diagram. Could you all take a look? Thank you.


texts: Deriving the zeros of this video amplifier circuit

texts:
This is problem 6.3 from Vorpérian's Fast Analytical Techniques book. I'm having trouble proving his answer for the numerator of this video amplifier circuit's voltage gain function. The general form of the voltage gain is given by
\begin{align}
A(s) = A_m \frac{N(s)}{D_L(s) D_H(s)},
\end{align}
where \$ D_L(s) \$ and \$ D_H(s) \$ denote the poles for the low and high frequency response, respectively, and \$ N(s) \$ denotes the zeros.
Here's what the circuit looks like simulated in Qucs-S. I generated it from this simulation file. (To open this in Qucs-S, copy all the text in it and save it as a *.sch file. Then open it using Qucs-S.) I realize the simulation is at a ridiculous frequency (up to 100 THz; we should be using transmission line theory at that point), but I wanted to make sure I was able to see all the high frequency poles and zeros.

In the book, the numerator is given by
\begin{align}
N(s) = \left( 1 + \frac{ s }{ \omega_{oz} Q_{oz} } + \frac{ s^2 }{ \omega_{oz}^2} \right) \left( 1 - s \frac{ C_{bc2} }{ g_{m2} } \right),
\end{align}
where
\begin{align}
\omega_{oz} &= \frac{ 1 }{ \sqrt{ C_{bc1} C_{be1} r_{o1} r_{\pi 1} \parallel \frac{ r_{x1} }{ 1 + g_{m1} r_{o1} } } } \\
           &\approx \frac{ 1 }{ \sqrt{ C_{bc1} C_{be1} \frac{ r_{x1} }{ g_{m1} } } }
\end{align}
and
\begin{align}
Q_{oz} &= \frac{ \sqrt{ C_{bc1} C_{be1} \frac{ r_{o1} }{ r_{\pi 1} \parallel \frac{ r_{x1} }{ 1 + g_{m1} r_{o1} } } } }{ C_{be1} + C_{bc1} \left[ \frac{ r_{o1} }{ r_{\pi 1} } \left( 1 + \beta_1 \right) \right]]  } \\
       &\approx \frac{ \sqrt{ C_{bc1} C_{be1} \frac{ g_{m1} }{ r_{x1} } } }{ C_{be1} + C_{bc1} g_{m1} r_{o1} }.
\end{align}
Now, I managed to figure out where the factor of \$\left( 1 - s \frac{ C_{bc2} }{ g_{m2} } \right)\$ comes from. When the output voltage \$V_o\$ is zero, all of the current from the dependent current source \$g_{m2} v_{\pi 2}\$ has to flow through the two capacitors with which it forms a loop. This allows us to formulate that loop's KVL equation as
\begin{align}
v_{\pi 2} \left( s C_{bc2} - g_{m2} \right) = 0.
\end{align}
After two algebra steps, we find the zero at \$\left( 1 - s \frac{ C_{bc2} }{ g_{m2} } \right)\$.
I have been working on deriving \$\omega_{oz}\$ for just over six months' worth of weekends. It's definitely gotten to the point where I can't do this myself.
I figured that since
\begin{align}
\omega_{oz} &= \frac{ 1 }{ \sqrt{ C_{bc1} C_{be1} \mathcal{R}^{(1)} \mathcal{R}_{(1)}^{(2)}} } \\
           &= \frac{ 1 }{ \sqrt{ C_{bc1} C_{be1} \mathcal{R}^{(2)} \mathcal{R}_{(2)}^{(1)}} },
\end{align}
where \$\mathcal{R}_{(j)}^{(i)}\$ denotes a null resistance, I could simply assume that \$\mathcal{R}^{(2)} = r_{o1}\$ and \$\mathcal{R}_{(1)}^{(2)} = r_{\pi 1} \parallel \frac{r_{x1}}{1 + g_{m1} r_{o1}}\$, and try to reproduce the result that way. However, in the process of attempting to derive \$\mathcal{R}^{(2)}\$ and \$\mathcal{R}_{(1)}^{(2)}\$, I found that
\begin{align}
\mathcal{R}^{(2)} = r_{x1} \parallel r_{\pi 1} \left( 1 + g_{m1} r_{o1} \right)
\end{align}
and
\begin{align}
\mathcal{R}_{(2)}^{(1)} = r_{\pi 1} \parallel \frac{ 1 }{ g_{m1} } \parallel r_{o1}.
\end{align}
I got these results by assuming that \$R_1\$, \$R_{e 1}\$, and the rest of the circuit to the right of \$r_{o1}\$ all do not contribute to the calculations of these null resistances.
The value of \$\omega_{oz}\$ from my results (which is \$ \frac{1}{2 \pi} (31.618 \times 10^9 ~\text{rad/s})\$) and the one from the book's results (which is \$\frac{1}{2 \pi} (31.403 \times 10^9 ~\text{rad/s})\$) agree numerically within an error of about 0.6%. However, I don't think my derivation and the book's derivation agree for all component values.
So here's my question: how would I go about deriving the coefficients \$\frac{ 1 }{\omega_{oz} Q_{oz} }\$ and \$\frac{ 1 }{ \omega_{oz}^2 }\$ from
\begin{align}
\left( 1 + \frac{ s }{ \omega_{oz} Q_{oz} } + \frac{ s^2 }{ \omega_{oz}^2} \right)?
\end{align}


texts: How to communicate faster than the system clock

texts:
I was reading about the new (ish) Thunderbolt 3 today, and was very impressed by the specced speed of 40Gbps. Then I looked at Intel's latest i9 processor speed... about 4.2GHz max. How can a system communicate almost 10 times faster than the clock driving it? Even parallel communication would still need 10 channels to get 40Gbps, and from what I can tell USB-C only has 4 or so.

Having read the responses, it seems like there are two parts to this: how the CPU/system communicates at such high speed, and how that high data rate (which it seems is accomplished using many parallel lines) gets through the bottleneck of the thunderbolt cable itself, which only has a small number of parallel channels.


texts:
One of my customers brought in several old EPROMs that he wishes to be re-programmed with the current firmware their system is using.
My usual way of dealing with this is to place the EPROMs in the eraser - this has a 10-minute timer.  When the first time cycle has elapsed, blank-check the chips.
If they test blank after one 10- minute erase cycle, put them back in the eraser for another 10 minutes.
If it takes more than one erase-cycle for them to become blank, count the number of 10-minute cycles for them to become blank, then double that erase time.
These 5 chips came up as blank after only one 10-minute erase cycle, so they all got an additional 10 minutes of erasing.
I'd like comments on the above.  This has worked well for me in the past but I'd like the guidance of  people smarter than myself.
My real question is in regards to the actual chip programming.  I'm worried that the chips may not hold their data as well as new chips.
What I'm thinking of doing is double-programming them.  Program each chip as normal and ensure they verify okay.  Wait a day, then verify again.  If they verify properly, then program them again (and verify).
These EPROMs are NOT in mission-critical equipment.  And although I used to regularly do this for customers oh, so many years ago, I want to give the customer the best chance these chips will work correctly for the indefinite future.
Yes: the obvious answer is to purchase brand-new chips.  Problem is these are mostly obsolete and what I'm finding is New Old Stock.  That doesn't make the new chips much better than what the customer brought me to use.
Programmer is a Xeltek 560U and the chips are 27C020 and M27C2001 (256k x8).
Again: guidance very much appreciated.
[Edit]
I did peruse the archives and found Older Tread about multiple programming cycles


texts:
I am driving an air core motor using PWM control from a microprocessor.  The position of the air core is dictated by the combined magnetic field created by applying 2 currents to 2 coils (sine coil and cosine coil):

tan theta = Isin / Icos

simulate this circuit – Schematic created using CircuitLab

The current in each coil is being created by PWM - the maximum PWM duty cycle is 75% and the minimum is 0%.

As I slowly change the values of the sine and cosine currents through 360 degrees, the magnet follows the desired position very nicely.  However, around the 0, 90, 180 and 270 degree positions, the needle slows down as it passes through the quadrantal position then speeds back up to the normal rate of change in position (even though I am changing the desired position at a constant rate [0.1 degrees change per step]).

My question is, can you think of a reason why this is the case?

EDIT: Having inspected the air core, the magnet is surrounded by both coils, as shown.

simulate this circuit

The physical arrangement is shown here:

The patent here (PWM driver patent) describes an issue that appears similar, however, it is caused by a microprocessor being unable to accurately generate a PWM waveform when close to 0% and 100% duty cycles (back in 1991).  We have a hardware PWM module, so there is no issue with this.

What is the force on the needle? Is it constant throughout 360 degrees rotation, or does it vary according to its angular position?

We are attempting to change the desired position (combined magnetic field of the coils) at a constant rate.  It looks almost as though the force on the needle is less when it is nearly aligned with one of the coils and when the desired position is not close to being aligned with one of the coils that the force is greater.


texts:
Recently I powered on an electrical device that was (unbeknownst to me) quite defective.  It tripped the circuit breaker almost immediately (after shooting off some sparks).  There was a small (600W) transformer between the mains supply and defective device, which has its own internal fuse to guard against overcurrent events.

What struck me as odd was that the fuse was fine, despite there having been enough current drawn to trip the main breaker.

In essence, I've got things rated like:

Main Breaker - 30A @ 240V
Transformer Fuse - 10A @ 120V

Which seems to say that the fuse should always blow before the breaker trips, as it takes significantly less current to blow the fuse.

How is it that the breaker can be tripped while the fuse remains intact?


texts: How do I calculate the voltage drop over a diode OR gate?

texts: I am not an electronics professional, and know little about circuitry other than Ohm's law and the difference between series and parallel circuits. I want to build a two-way telegraph for my first project, consisting of two keys made up of an LED and a push button switch, and a center consisting of an OR gate and a power source. My problem is not in designing the circuit, it's finding out what value to make the resistors/power source. My LEDs will have a voltage drop of 2.2 and my regular diodes 1.1. I cannot seem to wrap my head around the concept of voltage drop when multiple components are involved. I know that the voltage goes down by 1.1 when current passes through a diode, but what happens when a circuit branches into two diodes that then recombines?


texts: Stepper motor going one step forward and one backward

texts:
I have DRV8825 driver wired like that:

And I'm sending high and low signal in loop. Each 2 high signals motor moves one step. And it moves forward then next step backward. Yes, I've tried to switch wires - with surprising effect: motor still does the same


texts: Power rail decoupling caps for analog circuitry

texts:
First off, the terminology I'm using could be complete rubbish - I'm still learning

I have a mixed signal board for measuring bio-signals. The 4 layer board will have a split ground plane, analog ground and main ground (for a microcontroller, SD card, extra sensors, etc), star connected at the power pins through a ferrite bead. Previous versions (which I did not design) have had significant problems with noise.

Should the analog circuitry (mostly op-amps, etc.) have additional decoupling capacitors near the physical chips, in addition to the caps at the outputs of the DC/DC and charge pump that are powering them? similar to the picture below.

Assuming that it should have the decoupling caps, what size and why?
The DC-DC and charge pump are in the range of 100s of KHz to a few MHz, while the analog signals we are interested in are less than 100Hz, centred around 10Hz

Finally, all componants are Imperial 0805 packages (for convenience, still prototyping). The op-amps are 0PA2277 (additional question: is it better to use OPA4277, with 4 op-amps per package instead of 2, in terms of noise performance?).


texts: Would leakage through a JFET create thermal noise

texts:
The impedance through the gate of a JFET is very high and leakage current very small.  Would this impedance act like a large resistor creating thermal noise?

Would this be a low noise way of implementing a large impedance?


texts: How to find Thevenin voltage of two-port network from admittance matrix

texts:
The two-port network is powered by 10 mV voltage source and has admittance matrix:
\$ Y =
\left|
\begin{matrix}
y_{11} &  y_{12} \\
y_{21} &  y_{22}
\end{matrix} \right|
=
\left|
\begin{matrix}
2 \cdot 10^{-3} &  -3 \cdot 10^{-5} \\
0.5 &  2 \cdot 10^{-4}
\end{matrix} \right|
\$

From admittance matrix I know, that

\$ \left[
\begin{matrix}
i_1 \\
i_2
\end{matrix} \right]
=
\left[
\begin{matrix}
2 \cdot 10^{-3} &  -3 \cdot 10^{-5} \\
0.5 &  2 \cdot 10^{-4}
\end{matrix} \right]
\times
\left[
\begin{matrix}
u_1 \\
u_2
\end{matrix} \right]
\$

\$ i_1 = 2 \cdot 10^{-3} \cdot u_1 - 3\cdot 10^{-5}\cdot u_2 \\
 i_2 = 0.5 \cdot u_1 + 2\cdot 10^{-4}\cdot u_2\$

The task is to draw Thevenin's circuit for this and to compute its parameters. All I can imagine when I hear "Thevenin" is circuit like this:

I suppose, the parameters are \$U\$ and \$R_i\$. I would compute \$ R_i \$ as \$ \frac{1}{y_{11}} = \frac{10^3}{2} = 500 \space \Omega\$. Is that right? If not, how to compute that?

And I have no idea how to compute \$U\$. I know it is equal to voltage between \$2\$ and \$2'\$ nodes in this picture:

Any hint or explanation?


texts: Why would I need a relay between a DC motor and my Arduino?

texts:
I was told that I should put a relay between my 5V motor and my Arduino. I asked why, but they didn’t know.

Why do I need to separate them with a relay? The motor requires 5V and the Arduino provides 5V.

Also, do I need to separate all components from the motor with a relay or could I, for example, put them in the order:

Arduino -> Relay -> Demultiplexer -> Motors?


texts: How to implement a MIMO model with state space block in sumulink?

texts: I want to implement an state space model with 4 inputs and 4 outputs at simulink. But the state space block has only one input and only one output. So what can I do here?


texts:
I'm porting a circuit from DE0-Nano to DE5-Net.
I'm currently implementing a simple test circuit for the DE5-Net. So far I can program the user LEDs and the two Hex Displays.
However, I don't seem to be capable of doing any serial IO. My VHDL is generated, so I'll try to explain what I'm doing.
I am using an FTDI USB-RS422-WE-1800-BT cable, the FPGA connector of which I had to crimp myself. I may have made a mistake with the crimping. I don't have the tools at the moment (holidays & working from home) to test this.
The cable I mentioned before does appear to be working in the sense that it's correctly connected to /dev/ttyUSB0. For example:

lsusb shows the cable when it's plugged in;
echo Hello world > /dev/ttyUSB0 returns a zero exit status and the cable's PC end connector emits light;
od --read-bytes=1 < /dev/ttyUSB0 doesn't throw an error but it doesn't output and it blocks.

I'm using Quartus and Ubuntu. The following provides some more detail. Some of these commands aren't needed but none of them result in an explicit error.

I run stty -F /dev/ttyUSB0 sane;
I run stty -F /dev/ttyUSB0 raw;
I execute 'quartus_pgm -l', which detects the FPGA;
I run jtagconfig, which also detects the FPGA;
I upload the netlist to the FPGA;
I execute the FPGA and this results in the correct signals for the LEDs and the hex displays on the FPGA at 50MHz/9600 Baud.

My test environment simulates a continuous sequence of (10 bit data frames: one low start bit; 8 data bits; one high stop bit). Each bit signal is maintained for \$d=5*10^7/9600\$ clock cycles:
\$d\$ times 0 (start bit); \$8d\$ times 1 (constant data bits); \$d\$ times 1 (stop bit).
Im sending the start/data/stop bits to Pin AE17, while maintaining a low signal on Pins AF17 and AF16, and maintaining a high signal on Pin AG14.
If someone sees an obvious mistake or has a suggestion for a diagnostic test, please let me know.


texts:
I'm experimenting with a small servo motor with the raspberry pi using PWM (pulse-width modulation). My understanding is that the servo should respond to different length of pulse. I should be seeing some motion if I output a constant square wave, right?

And if I output a constant HIGH signal the servo shouldn't do anything.

Is there a way to test for sure that the servo is working properly? I don't have an oscilloscope so I can't really confirm that my code is outputting the way it should - thinking about putting an LED and I should see a blinking light.


texts: Does a power amplifier output constant current or constant voltage?

texts:
I am having a confusion with the following a 16W high power amplifier for an RF circuit.

Specifically I wonder, does it give me a constant current or a constant voltage as output?

and if it does neither, what does it do then?


texts:
So I have a transformer that is like 230 || 30 V.
One thing I don't get that on primary side it has the following leads:
0 --- 230V --- 240V

When it can be useful? I mean I can't think of situation when somebody would say "We should wire it to 240V, 230V will be a bad choice".
Isn't it hard to know what exact value particular wall outlet will be outputing? I always though that in one house it can be 230, then you go to the different city and it's 240, not to mention it is never precise, so you can get like 235.  Moreover regular customer doesn't know what he has in the outlet.
What is the reason that manufacturer decided to have two options?
I've never seen a 230/240 switch on any device either. And bonus question - if you already decided to make such a primary side - why not make 220V also?

I tried google this and all the answers were like "there is no difference, don't bother", but I suppose manufacturer would not make it such a way if it wouldn't have an application.


texts: Minimising interferences caused by switching low current

texts: For 2.4ghz radio devices, what are some good practices for minimising interferences caused by the boost converter on board? Suppose the input voltage is around 3V and output 5V <300mA. Even though the switching frequency is probably less than 600kHz, I wonder if the harmonics or other elements can cause substantial interferences that affect transmission (short/inefficient antenna).


texts: Does the 433 MHz transmitter/receiver, transmit the voltage?

texts:
The title, says it all...

I would like to know if the 433 MHz transmitter/receiver (couldn't find a datasheet, here is all I found on it) transmits the voltage, or if it just a logic output of '1' or '0'?

For example, if I send through the data pin on the transmitter a current of let's say 2.5V, does the receiver connected to a circuit of 5V, output 5V or 2.5V through the data pin?

I think it would logically output 5V but I am not sure...

Thanks in advance :)

Disclaimer: I have no components, I just bought some basic components and an Arduino kit on Amazon. But I am so impatient and excited to get the parts that I already started drawing up some circuits. So beware, a lot I am saying may be wrong...


texts: Why does my PWM amplitude vary with duty cycle?

texts:
I'm controlling a 4-pin PWM fan from a 5V PIC and before going too far I'll say that everything is working fine but I'm just not understanding what I'm seeing on my scope.

The fan has a 12V supply and an internal pull-up on its PWM control line, so I'm driving it from the PIC's PWM output via a 2N7000 MOSFET. This is the schematic:

During testing, I hooked up my scope with one probe on the fan's PWM line (i.e. the drain of Q1) and another probe on the output from the PIC (i.e. pin RC5 or the gate of Q1).

So with a 25KHz PWM with 90% duty cycle (active low from the PIC because it's inverted by Q1), I get the following, which looks ok (the top yellow trace is the fan's PWM and the bottom blue trace is the PIC's PWM):

However, as I reduce the duty cycle, for example to 30%, the amplitude of the fan's PWM drops:

And at 15% duty cycle:

Like I said, it's all working ok, I just can't understand where this drop is coming from. I took a few measurements and plotted in Excel, which looks like this, with duty cycle on the x axis and the voltage across the drain and source of Q1 on the y axis:

I don't think it's a measurement artifact of the scope because the PIC's PWM shows a solid 5V at every duty cycle, but I don't see why the behaviour of Q1 should change just because of a different duty cycle. So is this something unknown that's happening inside the fan's circuitry or have I misunderstood something?

The technical data for the fan shows a performance curve like so, which is of a similar nature to my Excel chart:

If anyone can help me to understand what's going on I'd be very grateful. Even if just to say that it's something unknowable inside the fan, at least I'd know that I've not done anything wrong.

UPDATE

Ok, just to round this off, I removed the fan and added a 100K pull-up to +12V instead and indeed I do now see the full 12V at every duty cycle. For example, compare this with the previous 30% trace:

So it seems that the fan itself is doing something to alter the pulled-up voltage depending on the duty cycle on the PWM control input. I'm happy with that but if anyone has any insights into what the fan maybe doing and why, it may be useful information for future reference. FWIW I can't find anything on the manufacturer's web site that gives this sort of detail.


texts: Differential CVD waveform in PIC18F45K50

texts:
I am using PIC18f45K50 for capacitive touch button using a differential CVD.
My capacitive button works. However I am not able to get the standard differential CVD waveform suggested by Microchip.
Has someone worked on differential CVD and could guide me or point me in the correct direction?
Currently this is how my waveform looks in a scope which is way different then the standard waveform suggested by Microchip:
Standard waveform

Edit2: New waveform and the code for ADC channel

And here is the code
unsigned long int result;
ADCON0bits.CHS = 14;// Set channel to the previous sensor
CVD_CHARGE_TRIS=0; Nop();CVD_CHARGE_LAT=1;
channel1=0;trischannel1=0;
// Start Pre-charge
Nop();Nop();Nop();Nop();Nop();Nop();Nop();Nop();
Nop();Nop();Nop();Nop();Nop();Nop();Nop();
trischannel1=1;//Disconnect current sensor from GND (HI-Z)
GUARD_LAT=1;
//Acquisition
ADCON0bits.CHS=adcchanselect[0];
Nop();Nop();
ADCON0bits.GO_NOT_DONE = 1; // Start conversion
Nop();Nop();Nop();Nop();Nop();Nop();Nop();Nop();
Nop();Nop();Nop();Nop();Nop();Nop();Nop();
while (ADCON0bits.GO_NOT_DONE){}
Nop();Nop();Nop();Nop();Nop();Nop();Nop();Nop();
Nop();Nop();Nop();Nop();Nop();Nop();Nop();
//trischannel1=0;//Ground sensors
//CVD_CHARGE_LAT=0;
result=ADC_GetConversionResult();
//Scan B
ADCON0bits.CHS = 14;// Set channel to the previous sensor
CVD_CHARGE_TRIS = 0;Nop();CVD_CHARGE_LAT = 0;//Set previous sensor to Gnd (discharge internal)
channel1=1;trischannel1=0;//Set current sensor to GND (charge external)
// Start Pre-charge
Nop();Nop();Nop();Nop();Nop();Nop();Nop();Nop();
Nop();Nop();Nop();Nop();Nop();Nop();Nop();Nop();
Nop();Nop();Nop();Nop();Nop();Nop();Nop();Nop();
Nop();Nop();Nop();Nop();Nop();Nop();Nop();Nop();
trischannel1=1;//Disconnect current sensor from GND (HI-Z)
GUARD_LAT=0;
//Acquisition
ADCON0bits.CHS=adcchanselect[0];
Nop();Nop();
ADCON0bits.GO_NOT_DONE = 1; // Start conversion
Nop();Nop();Nop();Nop();Nop();Nop();Nop();Nop();
Nop();Nop();Nop();Nop();Nop();Nop();Nop();
while (ADCON0bits.GO_NOT_DONE){}
channel1=0;    // Ground sensors
trischannel1=0;
result+=(1024-ADC_GetConversionResult());
return result;


texts: How to properly use a shut pin in audio connector to prevent floating pins when disconnected

texts:
I'd like to use this RCA jack in a project that detects roughly the volume level on an RCA audio source. The circuit filters out the DC line voltage, amplifies it with a PNP transistor and then shifts the AC audio signal ~+2.5V so an Arduino can read it.

In my circuit I'm measuring the signal on the tip and just pulling the sleeve to ground.

I've read this great post over at CUI and understand that the shunt (pin 3) acts like a normally closed switch between the sleeve and the shunt.

What's the appropriate way to prevent the this from floating and picking up noise when there's no source plugged in? I gather that it's normal to either put a pull-up or pull-down resistor on this type of shunt. I'm just not sure what would be correct here.

For reference, I'm using this circuit as an amplifier with a voltage divider and .1pF cap to between the amplifier circuit and the arduino.


texts:
I am now trying to fix a camera control wheel, like the one in the top right corner of this camera (not the one which I am fixing):

This is a cheap part but I cannot find a replacement for my camera model (yes, I have searched thoroughly) and I cannot bet on that whatever else I find will fit in. I have took it apart and I am totally confused.

What I see here is 12 clicks per full rotation wheel (I see the clicking circle grill) with plastic parts. A small PCB has three outputs (three stripes on the bottom) and two grounds (two pins on the sides), the brush set only touches the PCB and nothing else. The brush does not move closer or further from PCB, it is fixed at some distance.

Now, THIS is expected to be able to deduce a click from every 30 degree position change:

http://imgur.com/a/upkUW - contact plate, brushes and 120 degree rotation simulation with correct starting position.

http://imgur.com/a/Y0z2D - PCB with oil and friction marks outlined

Even more: the contact plates (bright places of PCB) seem to be not conductive at all - measured resistance between two points of same plate is >2MOhm.

How is it expected to work at all given that no details are missing? Is it more than a contact shortening device?


texts: What is the function of the dippers in a slip ring liquid starter?

texts:
The liquid starter is one that uses a washing soda solution and water in a tank. From what I've read, the dippers are attached to a shaft controlled by a small motor to lower the dippers into the solution and thus vary the resistance.
I'd like to know what these dippers do and how they affect the change in resistance of the rotor circuit.
Also, where in the system are the electrodes and what role do they play?


texts:
To further my understanding of what happens when 2 circuits have a common ground could someone please explain what happens when the following 2 circuits (charged capacitor, high resistance load) :

share a common ground

What happens to the 2 voltages and capacitor plate potentials ?


texts: what size of copper wire can act as a 150A fuse?

texts:
If I would like to use a piece of copper wire as a 150A fuse, what size of wire should I use?

It doesn't have to be 150A very accurately, the parameters I need the wire to meet are:

it needs to conduct continuously 70A 10V-30V DC without getting red or overheating
it needs to conduct 120A sometimes for 15 seconds without melting
it needs to surely be melted before the current reaches 200A

Easily available wires over here are: 0.5 mm^2, 0.75 mm^2, 1.0 mm^2, 1.5 mm^2, 2.5 mm^2, 4 mm^2, 6 mm^2, 10 mm^2. Will any of these do the job? I can combine a few if the required value is not in the above series.

Edit: now I read more into the specifications of the device, and it is in fact rated to be fine with 600A for 5 seconds. Besides that I will be only ever using it continuously with 50A. Is that gap (50A - 600A) large enough to make a fuse out of copper?

This table of AWG wire sizes suggests that a 2.5mm^2 copper wire will melt with about 750A in 1s, and with a little under 200A in 10s, so it looks like it will melt in time for the device not to be damaged. The device itself is wired with 10mm^2 insulated wire, and I mostly worry about that wire not to be damaged.

Now I only need to find out to what temperature will a short piece of uninsulated 2.5mm^2 copper wire heat-up with 50A continuous current flow, and will it not melt the thing it is secured in at that temperature.

By "continuous" use I mean max 1 hour at a time, with full attendance of me, so it will not run unattended like this.

More info: The machine came originally with two 50A fuses wired in parallel. In fact I want to use a wire, because the fuses blow so often it starts to get expensive, on average I need 1 fuse per 1 hour of charging, so the fuses cost more then the electricity to power this. I don't know why they blow, because I have an ammeter wired in series with the fuse, and I never seen anything over 60A on the ammeter! The fuses don't blow randomly, I just can see the fuse slowly get red, it stays red for some time, and at one point it just melts. I've been watching this process and I didn't see over 60A while the fuse was melting, I was watching the ammeter all the time in the slow process of the fuse being melted. So if I need 1 fuse per hour, so be it, but I need some cheaper option then 50 cents a fuse if I am to use them at that rate.


texts:
Hopefully easy question for those of you into electronics, but as software person bit out of my depth.

What power supply should I be getting for the following LED strip for nice even light single color strip with dimmer attached? (that's not going to blow up/burn out)

Length: 10 meter (2 joined 5 meter strips)

Color: Red

Led per meter: 60

Wattage: 14.4 per meter

Voltage: 12v

Dimmer: LED dimmer mini RF 12-24V 12A

Been checking and calculating (12v /5A? ) but so confused by watts  volts, amps starting to doubt every answer I come up with


texts: Common drain stage/Source follower circuit analysis

texts:
I have been recently working on different type of MOS amplifiers and the following are my main doubts,

1) When we have a high gain stage such as the common source stage we use the output of this stage as an input to a common drain stage. What makes the common drain stage so special ? I know that they charge capacitors in a much quicker rate (Slew rate) compared to the common source stage but is there an intutive way to understand what makes the common drain stage good in this ?

2) In terms of slew rate is the push pull stage ( With the distortion effect corrected ) a better option compared to the common drain stage as the final output stage ?

Common drain stage     <---------->               Push-Pull stage