texts:
I have 4 DC motors. they each require about 12V 9A DC (108W each), and have a potential draw of up to 12V 20A each (240W each) stall current.
I am using 22 AWG insulated wire. The length of the wire, per motor terminal is about 1.2 ft.
This is all on a small(ish) sized robot.
I need to know what kind of wire I need (per motor terminal) in order to prevent wire insulation melting or fires, with wattage like that in mind


texts: Current multiplier/divider for current measurement?

texts:
You can change a current mirror into a multiplier/divider by adding transistors on either side. Then the number of transistors defines the current ratio. The transistors have to be integrated on the same chip to have a good precision (good matching), and besides, nobody wants to place 100 discrete transistors on his PCB for this.

Are there ICs for this, like a \$\times\$10 or \$\times\$100 multiplier (or \$\div\$10/\$\div\$100 divider, you should be able to use them for both)?


texts: a weird phenomenon with a 12V black & decker cordless drill

texts:
The background: I have a 10 years old 12V black & decker cordless drill, the batteries died successively, and I connected a 2 pin male plug try to use a PC power supply [PCPS] to run it.
What happened when I did the test is, a 460W PCPS works good, and a 450W PCPS didn't.
The weird phenomenon is when I directly plugged the 2 pin male into the PCPS's female 2 pin connector, the drill shaking and stop. I hooked the drill through a piece of twisted pair wire which has 2 pin female in one end and test clips the other end. The drill runs well.
The attached pictures shown the detail, any one can tell some thing about?


texts: How to power a scanner light with adapter, not battery?

texts:
Sorry for the noobish question. I'm a computer scientist, so my electrical engineering knowledge is of the "don't put fingers in electrical outlet" level.

I'd like to know how to power a salvaged scanner light of the type Scanner Light Hack v2.0 from a Canon MP210 scanner/printer. It is a single RGB tube.

I've already discovered the terminals for Power and RGB. I can turn on the light with a 9V battery, no problem. But when I use a power adapter, set to 9V as well, it doesn't work. Actually, I can get the green light to work, but not the others.

I thought maybe it was noise from the adapter? So I added a capacitor, but didn't help. I also measure the voltage with a multimeter, it reads around 9.20. The adapter is a variable adapter, but set to 9V and max output 1700ma. I've tried resistors? Didn't do anything.

I'm not sure what to try next. Anyone have any ideas?


texts:
I've created a net tie in OrCAD software. Everything seems to work, but there is one thing I don't get.
There's no problem when I connect to shapes with the nettie by placing it directly on two layers

But when I place the net tie first and then connect it to the layers, I lose the connections between pads

What's more, DRC reports no error. How can I make it better and be sure that I haven't forgotten to connect all elements?


texts:
In "Right the first time" by Lee W. Ritchey, he says "The impedance will be the same whether
the frequency of the EM energy is 1 MHz or 1 GHz. This holds true so long as none of the three variables changes with
frequency."

But clearly that equation has a dependence on \$ \omega \$ ? What's going on here?


texts: Calculating the current of an AC circuit

texts:
My goal is to calculate the current i(t) up in the right corner. Using the formula $$ Z_{total} = \left( U\over I\right), I = \left( U\over Z_{total}\right) $$

Given values are

$$
R_{1} = 1k \Omega,\
R_{2} = 0.5k \Omega,\
R_{3} = 0.4k \Omega,\
C_{1} = 1 \mu  F,\\
C_{2} = 1 \mu  F,\
L_{1} = 2H,\
e(t) = 10sin(1000t),\
\omega = 1000 $$
The internal impedance of the source is $$
Z_{i} = 10e^{j\pi/4}k \Omega
$$

I start with the parallell connection between
$$ Z_{R2}//Z_{C1} =  \left( Z_{R2}*Z_{C1}\over Z_{R2}+Z_{C1}\right) = \
\left( 500*\left( 1\over 0.001j\right) \over500+\left( 1\over 0.001j\right)\right) = -400 + 200j
$$

Ztotal:
$$ Z_{total} = Z_{R1} +Z_{R2}//Z_{C1}+Z_{C2} + Z_{R3} +Z_{L1} + Z_{i} $$
Im not sure if the internal impedace of the source Z(i) is supposed to be added to the total impedance as if it is connected in series with the rest of the impedances? If it is I get the following.

$$ Z_{total} = 1000 +(-400 + 200j) -1000j + 400 + 2000j + 10\times1000(\cos(\pi/4)+j\sin(\pi/4)$$
$$= (1000+5000\sqrt2)+j(1200+5000\sqrt2) $$

Now I use the formula above, since the current goes from + to - I get a negative voltage.
$$
I = \left( -U\over Z_{total}\right) = \left( -10\over (1000+5000\sqrt2)+j(1200+5000\sqrt2)\right) $$
$$=0.000865e^{-j0.007976} $$
$$= 0.000865\sin(1000t-0.007976) $$
Does this make any sense?


texts: Help Getting Chip Part Number, Logic-Driven DIP 12V/24V Power Control

texts:
I am planning a future project, but I need the ability to have a 5V logical high enable a 12 or 24V source from an external supply, in a standard DIP package. I remember using something exactly like this YEARS ago in high school, but I cannot remember the specifics.
Pretty much, the issue is that I am clearly searching for the wrong term when trying to identify it. If I knew what this is CALLED, then I should be able to get all the google results I need.
All I know is that it was a standard DIP, and according to the datasheet, it was capable of allowing an external 24V supply to pass through with a couple amps at least, with the enable condition being a 5V logical high, acting as a sort of "switch" for the 24V. It MIGHT have had multiple in a single package, although I cannot recall.
I have heard that I should look into the TI Power IC, but there seem to be several different families within that category on their website, so I am having an issue narrowing it down further, if that even fits the bill.
Any help on finding this would be greatly appreciated! If you know some part numbers, please answer below - I can take care of the rest.
Here is a very crude diagram, showing the BEHAVIOR (there was no audible switch, I am merely showing what it DID).


texts: possible to you add an external RF PA LNA to a chip that has internal PA LNA?

texts:
I'm working with a new generation of a wireless chip that now has a built-in PA and LNA.

The trouble is that its sensitivity is -92dBm and my old version that did not have internal RF amplifier could do -104dBm when combined with external front-end components.

The PA portion is not the issue because their output is limited by FCC.  The difference in the LNA sensitivity has a big effect on the range.

Is it possible to re-gain our old link budget using a design with external PA/LNA in combination of the built-in set?


texts: Finding the right battery management system for LiPo

texts:
I am building a "smart" battery by combining a bunch of Samsung 18650 cells with a battery management board that handles charging/discharging/protection.

The enclosure I plan to use allows for 4 x 7 cells, and I need 12-14.4 V range (this will replace a lead acid battery).

The architecture I want to use is thus:  3.6V x 4S x 7P (3.6V x 4S = 14.4V).

So the question is, I found a battery management board that supports 4S (here). Can I safely charge 7 cells in parallel? and what other options do I have?

Thanks!


texts: Interface NodeMCU with RCWL-0516 Microwave Radar Sensor and power via battery

texts:
I am trying to interface NodeMCU with RCWL-0516 Microwave Radar Sensor and power it via battery. Below is the circuit diagram

Below is the Arduino Code I am using :

int Status = 12;  // Digital pin D6

int sensor = A0;  // Analog pin A0

void setup() {
  // put your setup code here, to run once:
   Serial.begin(115200);
   pinMode(sensor, INPUT);   // declare sensor as input
   pinMode(Status, OUTPUT);  // declare LED as output

}

void loop() {
  // put your main code here, to run repeat edly:
    long state = analogRead(sensor);
    Serial.println(state);
    if(state >= 200) {
      digitalWrite (Status, HIGH);
      //Serial.println(state);
      Serial.println("Motion detected!");
      delay(1000);
    }
    else {
      digitalWrite (Status, LOW);
      //Serial.println(state);
      Serial.println("Motion absent!");
      delay(1000);
      }

}

Now with this circuit I am facing following issues :

1) Radar Sensor keep getting triggered and the led keeps getting on and off
(When I replace radar sensor with PIR HC-sr501 sensor it starts working normally. I suspect there is some interference between NodeMCU wifi signal and doppler wave)

2) No matter if I use PIR Sensor or radar sensor the battery last for only few hours and after it goes below 5.5V sensors stop working.

So, how can I make radar sensor and NodeMCU work together with battery without false triggering and how can I make it work for 2-3 days without changing battery?

UPDATE

When I power NodeMCU with USB then radar sensor is working fine. (So I don't think there is interference of NodeMCU with Microwave Sensor). Below is the circuit digram with NodeMCU powered by USB. Why there is constant trigger when NodeMCU is powered by battery?

Link of data-sheet of Radar Sensor


texts:
Context:

I often open up the freezer to my roommate's old laptop power supply.

It's the only way he knows to make it work, otherwise the power supply does not power up the laptop (and the status led does not light up). According to him, putting it in the freezer for about 30 minutes makes it reliably work.

I can attest to the unreliability of the power supply, and also to its regular working status: I've seen it work just this morning. This has been going on for multiple months, and the power supply goes needs to go in the freezer a few times every week.

Questions:

Is there any way in which putting the power supply in the freezer can really help?
If so, what are the physical phenomena involved?


texts: Using an NO switch to close to ground as an interrupt

texts:
I'm designing a circuit that supplies power via USB to an Arudino.  The USB power runs through a 3v3/5v dual regulator.  I'd like to use a small tactile switch in front of the IN lead on the regulator as an interrupt/reset apparatus, but I'm finding it difficult to obtain a suitable NC switch, though I have a variety of suitable NO switches on hand.

How reasonable is it to close the switch to ground as a means of interrupting power to the rest of the circuit?  As an example:

My assumption is that the resistance of the regulator and everything past it will make the closed-to-ground path better and should interrupt the power.  But I've never used an NO switch in this fashion and wanted to make sure I wasn't missing anything.


texts: Analog sensor signal isolation for ADC/DAQ

texts:
I am looking for the simplest way of sampling an analog sensor signal in an existing system while avoiding ground loops (say 20kHz maximum frequency). The sensor is a 5V supply with 0-5V return signal. I only need to sample the signal in a DAQ, but attaching to the sensor ground is causing ground loops. I can use the 5V supply if necessary to power an amplifier, but can alternately provide power from the DAQ side.

I believe an analog isolator is what I need, and that a single package would do the full job, but searching for the right component is finding amplifiers that require symmetric voltage supplies on both sides for example. What is the simplest solution for this application that is within say USD 10.00?

I have need for a high speed digital isolation and low speed analog, but high speed analog would just be more universal if possible.

Spec:

0-20 kHz
0-5 V
0.2 % linearity

All DAQ grounds are linked.

simulate this circuit – Schematic created using CircuitLab


texts: Recommendations for microcontroller programming under Linux

texts:
Can somebody make me a recommendation of some stable development environment (platform + programmer device + sw/ide) for beginning programming microcontrollers under linux (not arduino)?

I find it difficult to pick all this components, and I'm afraid I'll have to resort to windows. Thanks!

Update: Thanks for your answers! I'll give Microchip and Netbeans based MPLAB a try. Nothing against Atmel, but I think the former will be easy to setup for me;-)


texts: How do you drive a high current load from a moderate current source?

texts:
If I have a power supply that can supply 5A @ 12V and I need to be able to supply an inductive load with 20+A @ 12V, how would I go about this?

I need a burst of current for about 2-5 seconds.

Will a capacitor bank and high current relay do it?


texts:
Tenting vias is great for:

If a via is placed over some silk screen (designator, instruction, warning, etc.) and you want the text to be more readable
A compact design with high component density and potential shorts nearby
More aesthetic look (solder mask across the board, rather than gold/silver dots everywhere)
Stop solder being sucked away during reflow if placed under a component/near a pad

On the contrary, though, I can't seem to find any reason not to tent vias. Assuming you have appropriate test points and the design works 100% (i.e. no need to probe around and check things), is there any reason not to tent every via on the board? Even if you do need to probe, you can still dig through the solder mask and make a connection if worse comes to worse anyway.

Only thing I can think of is increased heat retention if it is a high-current via, but besides that I'm lost.

Any ideas?


texts: Determine the output signal given the input and inpulse response

texts:
It's been a while since I've worked these types of problems, but I've been working out the following problem for a while now and can't figure out a few details:

And here is the solution:

Most of the solution makes sense, but I just have a few things I'm not able to clarify, namely:

How were they able to determine the h(t) is a low pass filter? And which fourier coefficients will be passed through? Seems like n=2=-2 should be a valid coefficients too
How did they get h(t) into the frequency domain?

*Update:
For the aspect of getting h(t) into the frequency domain, I've attempted the following but it doesn't line up with the what's given in the solution:

Any help is appreciated


texts: Induction motor full load and no load test meaning

texts:
Why we doing the full load and no load test for induction motor

What is the purpose ? and can you provide some example?

Why we doing the full load test and find power and stuff

and also for no load test


texts: last year I bought a xbee pro s2b, the wire antenna one. After some use, the antenna started to loose, and last week it just broke. Is there a way to repair it? I soldered it again, and it holded some time, but it broke again. What should I do?


texts: Can anyone tell me the type and model of transformer (T1) in the following circuit diagram.


texts:
What is actually alternating current (AC)? And direct current (DC)? I've been reading several books about basic electric circuits analysis and they are contradictory.

Some books say that AC is the same as the sinusoidal stationary state. That is, a sine or cosine function (actually, they are the same only shifted horizontally). For instance, \$v(t) = A \sin(\omega t + \phi)\$. Acording to these books, DC is totally stationary (static), that is, the voltage and current are not time-dependant (\$v(t) = k\$, where \$k = \mathrm{const.}\$). Currents have the same form as voltages on each of these cases.
According to other books, AC is any current that is changing (that is alternating) his sign over time (\$t\$). With maths notation: \$i(t_1) < 0\$ and \$i(t_2) > 0\$ for some \$t_1\$ and \$t_2\$ where \$t_1 \neq t_2\$. It could have any shape as long as it's alternating his sign.

I'm inclined to think that in practice wins the first option but maybe it's better the etymology of the second option.

Some other cuestions have relation to this:

Is AC a voltage that is the sum of a sinusoidal stationary state and a constant voltage? For instance, \$v(t) = A \sin(\omega t + \phi) + k\$.
Is AC a shawtooth wave?


texts: current transformer and its connections to the microcntroller(8051)

texts:
i want to make an anti power theft system to a digital meter,for that purpose  i am first trying to make digital meter to  measure how much power is being used in our house.

So i want to measure current in the line being drawn when any devices are on ( i.e instantaneous current), I have planned to use current transformer but, before going to the question i would like to ask that same job of  the current transformer  can be done using a power resistor then why not to use that??

ok if that is being answered then :i am actually going to measure the voltage  across c/t or the resistor but i am stuck  at this  point  how  to  find  the  voltage??.

Actually  i  wanted  to use differential  op-amp circuit  which could measure exactly the voltage difference  across the  resistor/ c/t and could  be  fed  to  the  adc.
 But  the input  is ac if i opt for rectification &  various other  procedures then  there will be  lot  of  stuff  to  be included  and the signal  will attenuate..
so  can  any one  suggest  whether  that idea   of using differential  opamp  is right??...and how  should signal be maintained?


texts: PCB design: safe clearance between via and ground or Vcc inner plane

texts:
I'm new to PCB design and I'm trying to achieve my first four-layer PCB.

Inner layers are GND and Vcc planes filled entirely with copper.

I need to use a via to wire a USB signal (tx, rx) from the top layer to the bottom layer. My default clearance for trace/spacing is 0.1 mm/0.1 mm, and the drill size is 0.2 mm.

I wanted to know if I could lose the USB signal if I keep a 0.1 mm clearance for Vcc and GND planes copper.

Is there a safe clearance for via wiring a USB signal or any other signals?


texts: Audio amplifier alignment procedure questions

texts:
I have a couple of questions related to the alignment procedure for the amplifier of Klipsch SW-12, a powered subwoofer.

Its service manual (link below) says the following:

(page 3)

COMPRESSION

The compression circuit consists of U5, U6, and Q28 and is adjusted via R30. If adjusted correctly, this circuit will limit the amplitude of the signal so the minimum amount of distortion in the form of clipping will occur at the output of the amplifier. R34 is used to set the maximum output level for the amplifier so it doesn’t underamplify or clip.  Next, the signal goes through a buffer amplifier U2, which provides a gain of 4.  Then the signal goes on to the driver circuits.

The alignment procedure (page 5) is the following:

SW12-I AMPLIFIER ALIGNMENT PROCEDURE

Equipment required:
  A signal source capable of supplying a 30Hz sine wave at 300mVrms.
  A true RMS Voltmeter such as the Fluke 8060B.
  A 16 ohm load rated for at least 200 Watts.
  An oscilloscope (optional).

To totally align SW12 series 1 amplifiers, follow this procedure:
  1. Disconnect power from the UUT (unit under test).
  2. Connect the UUT (unit under test) to a 16 ohm load.
  3. Connect a signal generator to the RCA input of the amp.
  4. Set all controls on the UUT to their full clockwise position.
  5. Set the signal generator for 30Hz and 60mVrms output.
    (be sure and measure the output of the generator for 60mVrms.)
  6. Connect the voltmeter leads to the output of the UUT.
  7. Apply power to the UUT.
  8. Adjust R34 for 33Vrms. Range is from 32.1 Vrms to 34 Vrms.
  9. Change signal level to 1.5mVrms @ 30Hz .
  10. Measure the output voltage. Should be between .94 Vrms and 1.06Vrms.
      Adjust R30 if necessary.
  * NOTE: Some interaction between adjustments is common. Recheck steps 8 and  10 for proper voltages.
  11. Alignment of the UUT is now complete. Disconnect power and other
    connections from the UUT.

Questions:

I don't have a 16-ohm load. I want to use an 800-watt space heater that is 17.5 ohm. What should the target voltages for R34 and R30 be? Do I need to change them? Or should they remain the same?
As to adjusting R30, to make the compression lower (to make less compression), should the output voltage be raised or lowered?

=================================
The service manual for SW-12 is here:

http://www.audiolabga.com/pdf/SW12-15%20I.pdf

Update (9/28/2018)

Accepted Tony EE rocketscientist's answer and built a 186.23-ohm resistor, consisting of 4 of the 16 750-ohm power resistors I had had since I started working on the subwoofer last year. Their not being exactly 750 ohms helped.

Their values and the combined (calculated) resistance:

773.5

738.0

734.4

735.2

186.2312444271

The space heater's resistance with/without the above resistor


texts:
I am trying to design a board controlling the powering up of an Esp8266 with the following features

low consumption
power on at fixed interval (kind of a heartbeat)
power on, when an edge is detected on a specific input say IN1
monitor the state of IN1 with the ESP

The way I designed the board so far uses a TPL5110 for the low consumption side and schedule, together with an edge detecting circuit connected to the manual trigger of the TPL.

The edge detection circuit consists in two sets  of capacitors and resistors that will  charge (resp discharge) when IN1 changes state. The caps discharge to a npn transistor that will feed the manual trigger of the TPL.

This setup works rather satisfyingly... as long as the edge detection is connected to the manual trigger after being charged.
The reason for that is that at startup the TPL reads the timing configuration on the same pas the manual trigger (basically reads a resistor value by flowing g some current there). The rising edge triggers at startup and interferes with the TPL startup setting.

I was looking for a simple  a way to delay switching on the edge detecting side but I couldn't find out how.. any thoughts or suggestions would be very much appreciated.

For completeness, the project is to build a low consumption WiFi door monitor, with a magnetic switch connected to IN1.


texts:
In a noisy media, I need to receive 10bytes with DMA (about 1Mb). I have set the DMA and its interrupt as shown below:

void DMA_Configuration(void)
{
    DMA_InitTypeDef DMA_InitStructure;
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

DMA_DeInit(DMA1_Channel3);
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART3->DR;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Buffer;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = sizeof(Buffer) - 1;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode =DMA_Mode_Normal  ;//DMA_Mode_Circular
DMA_InitStructure.DMA_Priority = DMA_Priority_Low;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel3, &DMA_InitStructure);
USART_DMACmd(USART3, USART_DMAReq_Rx, ENABLE);
/* Enable DMA Stream Transfer Complete interrupt */
DMA_ITConfig(DMA1_Channel3, DMA_IT_TC, ENABLE);
DMA_Cmd(DMA1_Channel3, ENABLE);

}
void DMA1_Channel3_IRQHandler(void) // USART1_RX
    {
    if (DMA_GetITStatus(DMA1_IT_TC3))
        {
            SendTest=Buffer[2];
            DMA_ClearITPendingBit(DMA1_IT_TC3);
        }
    }

My buffer receives 10bytes. In a noisy media, some noises can deceive my receiver. I implement another pin for telling the receiver I need to send:

void EXTI15_10_IRQHandler(void){

if (EXTI_GetITStatus(EXTI_Line10) != RESET) {
            if(GPIO_ReadInputDataBit(GPIOC,GPIO_Pin_10)==0 ){DMA_Configuration();GPIO_ResetBits(GPIOA,GPIO_Pin_5);}
            else
            {       //USART_DMACmd(USART3, USART_DMAReq_Rx, ENABLE);

                    GPIO_SetBits(GPIOA,GPIO_Pin_5);
                    DMA_DeInit(DMA1_Channel3);
                    //USART_DMACmd(USART3, USART_DMAReq_Rx, DISABLE);

            }

    EXTI_ClearITPendingBit(EXTI_Line10);
}

}

But I can't Enable and Disable DMA correctly(for example by getting 1-10 bytes it stop working in receiving mode). I disabled my DMA with different ways:

Disabling:
DMA_DeInit(DMA1_Channel3);
USART_DMACmd(USART3, USART_DMAReq_Rx, DISABLE);
DMA_Cmd(DMA1_Channel3, DISABLE);

Enabling:
Calling DMA_Configuration();
USART_DMACmd(USART3, USART_DMAReq_Rx, ENABLE);
DMA_Cmd(DMA1_Channel3, ENABLE);

I will be thankful if you could help me.


texts: Arduino+2X12 LCD to emulate a defective Kenwood HF rig display unit

texts: I have an HF rig with a bad display init (LC7582A driver and custom LCD with 9 seven-segment numeric indicators and some icons making for a total of a 100 or so segments). The input pins of the LCD driver are CE CLK and DATA. I gather from the datasheet that it expects about 105 bits from the DATA stream. I have a rough idea in my head that I have to build a "receive buffer" of about a hundred bits, then figure out and sort out which bits are for the numeric indicator segments, which bits are for a 10 segment signal meter indicator and the other icons (AM, LSB, USB, TX, RX, etc.)  And once I have "decoded" the stream. pass them on to an LCD display buffer for later pushing into a generic LCD or OLED display.  I am beginning to think, I might have to tackle this project in two steps: build a system to decode and sort out the stream bits and later after  knowing the stream "protocol", build the complete system.  The reason I got this rig was to force myself to finally learn Arduino or microcontroller programming.  If anybody can point me to some references (sketches, etc.) to get me started in the right direction, or give some tips, I would really appreciate it!


texts:
What is the purpose of resistance & capacitance in parallel to Load ( refer ckt ) ?

As per my understanding these capacitor & resistor is for filtration purpose ( kindly clarify the same) .

Values of C1 is 2.2uF/50V/open mode
Value of C2 is 0.1uf /50V/ Open mode
Value of R19 is 10K .


texts: How does this diode compensate bias current change on a BJT due to temperature variation?

texts:
'Im working on some exercises related to BJTs and found this circuit which is said to compensate (in theory) changes caused to bias current by temperature.

          Vcc
           o
           |
           /
           \ Rc
           /
           |  |
           |  | I_C
           |  v
   I_B     |--------------------o  V_o
  --->   |/  collector
  -------|
  |      |\             I_D     |
  |        | emitter  <---     ---
  |        |-----------
  |        |          |
  |        |          |
 ---       /        -----
           \  Re     /_\ Diode
           /          |
           |          |
           |         ---
           o
           - Vee

It says that by connecting a diode between emiter and ground like on the schematic, that is theoretically "the same" as the one that exists between base and emiter, we compensate for current variations on the output due to Vbe changing aprox. -2mV/°C in a PN junction as both the diode and the pn junction in the transistor vary in the same way compensating each other.

On the schematic we assume the transistor is correctly biased.

How does this diode compensation work?

(Please excuse the lack of a better schematic but I can't link images with my reputation)


texts: Is there a way to change AC 120 V @ 60 Hz to AC 120 V @ 40 Hz?

texts: My grandfather has Alzheimer’s and I read in a science article that a sound or light “played” at 40 Hz interacts with the waves in your brain to break apart the plaque build-up and reduce memory loss.  My thought was that if I were able to change the frequency of the light sockets (a screw in an attachment that I would build, but I can figure the structure of it up, just not the electrical side of it) then there would constantly be an atmosphere of a pulsing 40 Hz, via the lights. Any help as far as the initial wiring of this device would be amazing. If I can get a start I can probably finish it.  Thanks!


texts: How is ASIC design different from FPGA HDL synthesis?

texts:
I've had some experience with FPGA/HDL tool suites such as Xilinx ISE, Lattice Diamond, etc. The general workflow is writing Verilog/VHDL, simulation, testing and then programming the FPGA.

I've heard a couple of people say ASIC design is very different. What are the toolsets used for the two major types of ASICs, Gate level ASICs and Transistor level ASICs? I've been looking into High Level Synthesis tools such as Catapult C and Cadence C to Silicon, but I've never tried any yet. Can you explain the different types of tools available in the ASIC/FPGA field that can change/speeden up the typical HDL workflow?


texts:
When soldering capacitors, is the order on which you solder them important?

I am about to solder a project but I don't know this information

For example, I can solder each pin however I like, or one pin is goes somewhere, the other elsewhere?

Noob question, but first time soldering capacitors.


texts: Single wire CAN // Saab 9-3 I-Bus // GMLAN

texts:
I'm trying to control an instrument cluster from a 2008 Saab 9-3. It has 2 pins marked for I-Bus (both wires are green, continuity test shows they are tied together as shown here:

Some sites also call this instrument bus the GMLAN.
I had no information on how does this bus works except "the data transfer rate of the I-bus is 33 kbits/s" and:

So I have disassembled the unit and looking for some IC markings, I have found a AU5790D which is a single wire CAN transciever. There is a site with various CAN IDs and messages for a 2001 Saab 9-3. (They have changed the bus, but hopefully they have kept the codes.) Reverse-Engineering the Saab 9-3 Instrumentation Bus (I-BUS)

After some research on the one wire buses, it has turned out that my Seeedstudios Can Shield is useless here. I have ordered the same chip, so I can emulate a 2 node network.
My questions are:

Is it possible to use the transciever without any specific CAN
controller? (Directly wired to an Arduino)
(If it is not) What type of
CAN controller do I have to use between the MCU and the transciever?


texts: Enabling external reference to HP/Agilent Signal Generator (8648C)

texts:
What is the proper way to use an external 10 MHz clock signal for an HP/Agilent signal generator (in my case: 8648C)?

With my Tektronix, Rohde & Schwarz devices, internal/external reference has to be selected which makes sense.

But the manual for 8648C is just totally silent: How to activate it, how to ensure that is is actually used and locked?

Is it activated automatically? On powerup? When the external clock is connected? 5s after it is connected? ... ?

According to the manual:

  10 MHz REF INPUT and OUTPUT These connectors provide the input and
  output ports for the instrument's  timebase reference. The instrument
  will lock to a 2 MHz, 5 MHz, or 10  MHz external reference source
  connected to the input that is within ±5  ppm. When the internal
  timebase is being used, the output connector  provides a 10 MHz, 1
  Vrms level signal.

But with the scope I can see the 10 MHz signal at the REF INPUT always. Sure enough, the manual also doesn't say how to deactivate the "internal timebase".

I am not sure if the device actually uses the external reference because the measurements suggest I have some frequency mismatch.


texts: What situation does it make sense to mod a toaster oven instead of just buying a reflow oven?

texts:
I have seen kits like this online

http://whizoo.com/reflowoven

to modify a toaster oven to use as a reflow oven, but they seem like a significant amount more work and lower quality than just buying a reflow oven like

https://www.joyfay.com/catalog/product/view/id/51365/

Both seem to cost ~$200, but one involves a lot more work and risk. Why do people mod their own instead of buying them, just bragging rights or is there some aspect of customization or something I am missing?


texts:
So I wish to build a variable output mains power supply as a learning exercise.

I have determined the transformer that I need and now I am looking at the rectifier bridge.

I have looked at these diodes http://uk.farnell.com/on-semiconductor/mur410rlg/diode-ultra-fast-4a-100v-axial/dp/2441588

Which should easily allow my supply to deliver 24v @ 2.5A

Am I right?

Do I need to look into protecting the rectifier from a short?

I don't see many online guides dealing with this.

Also when it comes to earthing. Should I ensure the body of the case and transformer are connected to the death pin of the 3 prong plug. Earthing 24v on the secondary coil seems overkill.


texts: 3 phase transformers and equivalent circuits

texts:
There is an exercise in my textbook that goes like this:

3 single phase transformers are connected in wye-delta configuration.
Each transformer has the following parameters : R1, X1, Rc = \$\infty\$, Xm = \$\infty\$, R2, X2. (R1, X1, R2, X2 being the copper resistance/reactance of the primary and secondary). The primary is connected with a 3-phase line with line-line voltage Vs. Secondary is connected to a balanced load composed of 3 impedances Z=R+jX connected in delta fashion.

So we're asked to draw the equivalent single phase circuit of

Which is, according to solutions, this :

So what the primary sees is this:

Now, I understand why
$$
a' = \frac{V_{AN1}}{V_{AN2}} = \frac{N_1}{N_2} \sqrt{3} = a \sqrt{3}
$$
and why how Z is divided by 3 to convert the impedance to the wye configuration.

What confuses me is: why are \$R_2\$ and \$X_2\$ divided by 3 on the secondary side? I would think those impedances are in series with the secondary voltage, thus I doubt we could apply \$Z_Y = Z_\Delta / 3\$ here.

Secondly, what would happen with \$R_2\$ and \$X_2\$ if we had this circuit made of 3 single phase transformers like this when we derive the equivalent single phase circuit:

Would \$R_2\$ and \$X_2\$ be multiplied by 3 or would it be \$R_1\$ and \$X_1\$ that would be divided by 3 in the equivalent single phase circuit?


texts:
I am trying to build myself a very simple audio mixer that can take 3 line-level inputs and create a single output for a set of powered PC speakers. I found a schematic online (here) which I have tried to copy as closely as possible. My main question is about the power supply. I am assuming I can use +-12V for the TL072 op-amps, but I wasn't sure what the best way to do it is, I found this handy page that describes a few methods and I thought I'd use the one that utilises the TLE2426 since it seems so easy. Can someone please advise if I have implemented this correctly? Hopefully the schematic below is of good enough quality. Again, I want this to be very simple in design, but obviously if I have done something wrong then I'd really appreciate the heads-up. Thanks!

EDIT - I forgot to say that one concern of mine was the low current capacity of the TLE2426 (maybe 20-40mA) so would this be a problem in this case?


texts: Execution time problem of Memset() function in C

texts:
I have a typedef struct that stores my cumulative ADC parameters. When I clear my ADC_Sum struct it takes less than 300 ns to achieve the clearing process between size 1-8. But when size is greater than 8, it takes about 320 µs!!!

I realized that for size of 16, it takes less than 300 ns again.

I am working on a STM32 embedded board. I am wondering why this happens because it affects my real-time process. You can find the timing table and my code below.

dredg

typedef struct
{
   float CH1;
   float CH2;
   float CH3;
   float CH4;
   float CH5;
   float CH6;
   float CH7;
   float CH8;
   float CH9;
   float CH10;
   float CH11;
   float CH12;
   float CH13;
   float CH14;
   float CH15;
   float CH16;
   float CH17;

} Typedef_ADC_Sum;

Typedef_ADC_Sum ADC_Sum;

void clearSumArray(void)
{
    memset(&ADC_Sum, 0, sizeof(ADC_Sum));
}


texts: Finding a current sense differential amplifier

texts:
I want to measure the voltage drop across a shunt resistor, amplify it to 50 times the original value, and feed that (0 - 5 V) to an ADC. I'd prefer to do the "high side" current sense method (rather than having the shunt between load and ground), but might have to change that to get it all to work.

This is driving me mildly insane. I've spent many hours on this by now, but I still can't find a single IC that meets all my requirements - just most of them.

Anyway, my requirements are:

Less than $7 or so (I only need 2, so no "per 1k" prices!)
Able to tolerate the common-mode voltage of ~15 V (either side of the resistor with respect to ground)
Able to measure up to ~1.5 A (always less than 2) with good precision, preferably with precision at the low end as well (5 mA = 0.25 mV, 1.5 A = 75 mV, 2 A = 100 mV)
Rail-to-Rail
50 gain, or adjustable via resistors
DIP package/through-hole mounting. This one appears to remove about every single solution that otherwise works.

The requirements are absolute, perhaps except for the price... Still, I don't want to pay too much for this one part (current sensing) of the project; other ICs are involved in this as well, so the total for just the current sensing will turn out quite high.

All I can find based on this is the Maxim MAX472, which is obsolete and not available. Its replacements are surface-mount only, and I'd rather avoid making my first (after a small test) PCB double-sided, as long as routing will be theoretically possible with a single-sided board.


texts: Why the assembly code does not match the number of cycles of ARM M4？

texts:
I ran the following C program on STM32F405 (ARM Cortex-m4). I tried to comprehend its computation period instruction-by-instruction.
#include <stdint.h>

int32_t test(int32_t c, int32_t s) {
  int32_t t;
  int64_t a;

  a = (int64_t)c * s;
  t = (int32_t)a*58728449;
  t = (a - (int64_t)t*8380417) >> 32;
  return t;
}

To understand the assembly executing process. I used the following command to compile the .c code to .S assembly code.
arm-none-eabi-gcc -S test.c -mthumb -mcpu=cortex-m4

Then, I got the following assembly code.
    push    {r4, r5, r6, r7, r8, r9, fp
    add fp, sp, #24
    sub sp, sp, #28
    str r0, [fp, #-48]
    str r1, [fp, #-52]
    ldr r3, [fp, #-48]
    mov r4, r3
    asr r5, r4, #31
    ldr r3, [fp, #-52]
    mov r0, r3
    asr r1, r0, #31
    mul r2, r0, r5
    mul r3, r4, r1
    add ip, r2, r3
    umull   r2, r3, r4, r0
    add r1, ip, r3
    mov r3, r1
    str r2, [fp, #-36]
    str r3, [fp, #-32]
    str r2, [fp, #-36]
    str r3, [fp, #-32]
    ldr r2, [fp, #-36]
    mov r3, r2
    lsl r3, r3, #3
    sub r3, r3, r2
    lsl r3, r3, #10
    add r3, r3, r2
    lsl r3, r3, #13
    add r3, r3, r2
    str r3, [fp, #-40]
    ldr r3, [fp, #-40]
    mov r4, r3
    asr r5, r4, #31
    mov r2, r4
    mov r3, r5
    mov r0, #0
    mov r1, #0
    lsl r1, r5, #10
    orr r1, r1, r4, lsr #22
    lsl r0, r4, #10
    subs    r2, r2, r0
    sbc r3, r3, r1
    mov r0, #0
    mov r1, #0
    lsl r1, r3, #13
    orr r1, r1, r2, lsr #19
    lsl r0, r2, #13
    mov r2, r0
    mov r3, r1
    subs    r8, r2, r4
    sbc r9, r3, r5
    sub r3, fp, #36
    ldmia   r3, {r2-r3}
    adds    r6, r8, r2
    adc r7, r9, r3
    mov r2, #0
    mov r3, #0
    mov r2, r7
    asr r3, r7, #31
    mov r3, r2
    ldr r3, [fp, #-40]
    mov r0, r3
    sub sp, fp, #24
    @ sp needed
    pop {r4, r5, r6, r7, r8, r9, fp}
    bx  lr

I implemented test.c on STM32F405 working on 168MHz. To count the actual computing period. I used a function based on DWT to count the number of clock cycles. It shows test.c only costs about 21 clock cycles.
I also observed the period of test.c through an oscilloscope working on 1.25GHz sampling rate. I can capture about 155 points within the computation period of test.c, corresponding to about only 21 clock cycles.
How do these 60+ instructions run in 21 clock cycles? Some of these instructions even cost multi cycles. To check the assembly code, I also decompile the .o machine code and got the same assembly code. Why it doesn't execute as we expected?


texts: How many amps can I route through the automotive chassis?

texts:
I am working on an electrical installation in a truck which will operate as a mobile office.

I am wondering if it is possible to only route a 12V positive wire, and use the chassis for ground? Basically to save on cable costs.

Typically a car battery has its negative terminal connected to the chassis. Which to me suggests that the chassis has capacity for high currents. But I'm not sure if that is also valid for continuous load, e.g. at 100A, and whether this would work at longer lengths, e.g. 4-6 meters.

I'm wondering if the chassis will have too much resistance or other problems. The vehicle will be turned off, so I'm assuming noise won't be a problem.


texts: Why need the capacitors be as close as possible to the device?

texts: Just a simple question: what exactly stands behind the need for placing the capacitors as close as possible to the current consuming device's pins? Is that the inductance, resistance or maybe impedance of the PCB track or wire that affects the electric charge?


texts: small fixable position motor to drive universal stage, possible?

texts:
I'm trying to make a universal stage, inside a cooling chamber, controlled through Arduino. So what I'm after are small as possible motors (2-3 cm with shaft) to fix on the stage's arms which will allow me to rotate those arms with degree sensitivity. And just to complicate matters

the motors actually have to be able to bear the load of those arms (typically 1-3 AAA battery)
to be fixable in position (ie to resist rotating once turned to right place)
to be as cool as possible (stage is inside chiller cage, temperature control is quite crucial)

I'm not especially experienced at electronics and working my way through my first arduino learner book. But I'm having trouble working out which type of motor to fix my attention and research on. Can anyone help?

fyi - universal stage allows an object to be rotated in xyz. Think gimbal type mechanism - pic at http://www.olympusmicro.com/primer/images/stages/universal.jpg

Thank you in advance


texts:
I'm looking to create several sine waves on a single circuit. All must be under 20Khz frequency and each must be unique. Mostly it will be 5-10 frequencies needed.

As I found - almost all crystal oscillator are in Mhz frequencies and only one kind is 32Khz (which is still too high).

I should be able to get this wave on the other side using FFT.

Ideas? :)

Thanks


texts: Building a device that lights an LED once a minute

texts: I'm a complete noob in electronics. I want to build a simple battery-operated device that lights an LED for one second, once every minute. What do I need to buy to build it?


texts:
I have bought this FPGA development board, which requires this tool to flash it. I have written some verilog to blink an LED, built it, flashed it onto the board, and I am waiting for the LED to flash.

Here's the contents of blinky.v:

module top( //top module
    CLK_i,
    LED0_o,
    LED1_o
);

input CLK_i;    //input 12Mhz clock
output LED0_o;  //output signal to LEDs
output LED1_o;

reg [24:0] counter;

assign LED0_o = counter[24];
assign LED1_o = counter[3];

always @ (posedge CLK_i) begin
    counter <= counter + 1;
end

endmodule

Here's the contents of ice40hx8k.pcf:

### Clock
set_io --warn-no-port CLK_i P7

### LEDs
set_io --warn-no-port LED0_o A5 # green LED
set_io --warn-no-port LED1_o M4 # red LED

Here is my Makefile:

%.blif: %.v
    yosys -p "synth_ice40 -top top -blif $@" $< | tee logs/yosys.log

%.asc: %.blif
    arachne-pnr -d 8k -p ice40hx8k.pcf $< -o $@ | tee logs/arachne-pnr.log

%.bin: %.asc ice40hx8k.pcf
    icepack $< $@ | tee logs/icepack.log

.PHONY: build
build: blinky.bin

.PHONY: flash
flash: build
    iceFUNprog -P /dev/ttyACM0 blinky.bin

.PHONY: clean
clean:
    rm -rf blinky.asc blinky.blif blinky.bin

As you can see, you can build the binary with make and program the board with make flash.

I am certain that the correct module is "top", (I'm new to verilog but so far as I can tell, "top" is analogous to what "main" is in C). I am certain that the binary is reaching the FPGA; the iceFUNprog program writes the binary and verifies it okay. I've looked up the pins for the two LEDs and the clock input in the datasheet, and these details are in the file ice40hx8k.pcf.

I'd expect to see some pulse @ 3 MHz (that's bit 3 of the counter) and another much slower pulse, which is bit 24 from the counter. If I've calculated correctly, that's 500kHz. Since I don't see anything on the LEDs, I've gotten an oscilloscope out to try to find these pulses. I've found a 12MHz pulse on one of the pins of the microcontroller (this is presumably the same clock which is fed to the FPGA). But I don't see any other movement. The LEDs are constantly off, and the pins on the two connectors are all either constantly high or constantly low.

Is there an error in my verilog somewhere? Or what am I doing wrong?

Related meta question


texts: Thyristor voltage regulator with different fireing angle for each period with simulink

texts:
First of all I'm really low with EE so please, go easy on me. As home assigment we have to design Thyristor voltage regulator in simulink. It should run for 5 periods with different thyristor fireing angle for each period (30*, 60*, 90*, 120*, 150*). I managed to build it for single fireing angle with some matlab tutorials (first, second) and school book. The problem is I have no idea how to make it fire at different fireing angle each period (I mean, dynamically change the fiering angle for each period during single simulation, ex. 30* for first period, 60* for next etc.). Any tips how to do it?

The circuit and parameters:

Here are parameters:

AC Voltage source:

Peak amplitude (V): 230
Phase (deg): 0
Frequency (Hz): 60
Sample time: 0
Measurements: None

Pulse Generator

Pulse type: Time based
Time (t): Use simulation time
Amplitude: 1
Period (secs): 1/60
Pulse Width (% of period): 1
Phase delay (secs): (1/60) + (1/60) *1

Pulse Generator1

Pulse type: Time based
Time (t): Use simulation time
Amplitude: 1
Period (secs): 1/60
Pulse Width (% of period): 1
Phase delay (secs): (1/60)+(1/120)+(1/160) *1

Thyristor 1, Thryistor 2

Resistance Ron (Ohms): 0.001
Inductance Lon (H): 0
Forward voltage Vf (V): 0.8
Snubber resistance Rs (Ohms): 500
Snubber capacitance Cs (F): 250e-9

Series RLC Branch

Branch type: RL
Resistance (Ohms): 100
Inductance (H): 0.2

*1 According to first matlab tutorial the 1/160 should give fireing angle of 135 degrees. The (1/120) is 180 degree delay. I have no idea what 1/60 is. However that math works for my case.

@edit 21.05.2015
My teacher mentoined about vector input (tho no details). How to add vector input into thyristors (so the fireing angle is changed during simulation)?


texts: How to run a PWM controlled fan at 100% all of the time

texts:
I've salvaged a Nidec G14T12BS2AF-56J14 fan from a broken Playstation 3 which I would like to use to make a dust blower for PCs.

As a test, I've connected the fan as follows:

Brown: 12VDC
Black: ground
Grey: 12VDC

When connected like that, the fan spins at maximum speed (which is my desired result).

However, I'm not sure this is the correct way to connect this fan. First I suspected the grey wire to be a speed sensor, but the fan didn't spin when it wasn't connected. After touching the wire to 12VDC, it started to spin full throttle.
I've found out that the grey wire is a PWM wire via http://eikimartinson.com/archives/104-Driving-a-Playstation-3-Fan.html, where it states the PWM should be a 25kHz signal. But I've also read comments from people who stated using 5VDC or 3.3VDC directly connected to the grey wire.

Can I connect the grey wire directly to 12VDC? Should I add a resistor (1k for example)? Should I use a voltage divider to get 5VDC or 3.3VDC? Or do I really need a PWM signal? Keep in mind that I do not want to control the fan's speed (it would be a bonus, but the fan should really be running full throttle when in use).

Thanks for the information!


texts: Drawbacks and Benefits of High Switching Frequency

texts:
I was reading about Benefits of High Switching Frequency, I found the following:

Smaller converter can be cheaper – up to a certain power output. Beyond that power level small size might be worth some added cost.
Transient response can improve with higher switching frequency.

Drawbacks of High Switching Frequency:

Efficiency is worse, Switching loss is proportional to switching frequency.
Dropout voltage (minimum VIN) is higher.

The source : http://www.onsemi.com/pub_link/Collateral/TND388-D.PDF

Can you describe to me those Benefits and Drawbacks ?

Thanks


texts:
I'm wanting to make a light box of sorts from LEDs and wanted to run it by you to confirm I have the right idea...

I have ordered 500 super bright LEDs off eBay and want to wire loads of them together. The forward voltage on the specs says 3V and my supply voltage is 12V (max 2A). I want to provide 20mA of current to the LEDs for a nice brightness.

I have calculated that if I wire 3 LEDs in series with a 150 Ohm resistor, I will get the desired 20mA of current. Is this correct?

Resistor = (12V - (3*3V)) = 3/0.02A = 150 Ohm

Now I have 3 LEDs using 20mA of current, can this be up-scaled to the full 2A power by simply duplicating the circuit as shown in the picture? So in theory I could run 300 LEDs from the power?

One last thing, If the LED's forward voltage is 3V, does that mean I can used 4 in series without a resistor with a 12V supply?

Thanks

IMAGE IS SUPPOSED TO SAY 12V NOT 5V - I've been working with Arduino for the last while


texts: Why are the capacitors necessary for a quartz crystal?

texts:
I read that it is recommended to connect 2 grounded capacitors to both ends of the quartz crystal. But that doesn't make any sense to me.
Since capacitors have no resistance, wouldn't that make it so the electricity from the MCU flows directly into ground?
And if it doesn't, what's the point anyway? They aren't connected to a signal receiver, so they can't act as decouplers to stabilize the signal anyway.
They just seem to suck away the signal.
So what's the point of them and why are there 2 of them?


texts: Help with understanding the mechanism of this parallel to serial shift register

texts:
Can the following shift register operation be explained step by step manner?:

How does the MUX function? What happens at each clock is a bit confusing for me to interpret. I tried to figure out my self but something is confusing especially with respect to MUX and Q.


texts: Which of these is the correct circuit for JK flip-flop

texts: Are both of these correct ? I am seeing both of these in different places


texts: Measuring the resistance of a real inductor?

texts:
Real inductors can be represented as perfect inductor plus a series resistance \$R_s\$.

The impedance of this component is \$Z_{L+R_s}=R_s+j \omega L\$ therefore  $$\frac{1}{Z_{L+R_s}}=\frac{1}{R_p}-\frac{j}{Z_{Lp}}$$

With \$R_p=\frac{R_s^2+(\omega L)^2}{R_s}\$ and \$Z_{L_p}=\frac{R_s^2+(\omega L)^2}{\omega L}\$

Which means that the same system can be seen as the parallel of a perfect inductor \$Z_{L_p}\$ and a resistance \$R_{p}\$.

I never tried actually, but if I use a RLC bridge or simply a ohmeter to measure the resistance of a real inductor (the same way as if it was a resistor), what do I measure? \$R_s\$ or \$R_p\$? Or I do not measure anything?

If I measure \$R_s\$ will the measurement depend on the frequency of the RLC bridge?


texts: Low Pass Filter For Square Wave Through An Optoisolator

texts:
I've got a higher voltage square wave input that I'm feeding through FOD817B Optoisolator. The square wave frequency is in the range of 30 to 300 Hz.

The Circuit is like this:

simulate this circuit – Schematic created using CircuitLab

I've tried to filter the Circuit as shown above, it works ok, but it's still quite noisy.

(Scroll Down To Bolded Area)
Here are some screenshots from the scope:

No Filter Higher Freq
[]Higher Frequency

No Filter Low Freq(noisier)
[]

With Filter(low freq.)
[]

Here is the 12v input Signal with no filtering

After realizing my scope was not properly grounded to the circuit
Here are the correct signals

On Occasion I would see the Optoisolated Signal create the similar/same sharp downward spike in the middle of the positive cycle of the square wave. Like the 12 Unfilitered Signal, but sharper.


texts: I'm hoping someone can give me some more information so that I can confidently answer this question. . . True or false: A capacitor stores energy for ½ a cycle and gives it up on the other half, the net energy is zero.


texts: In Eagle, Why via is created in the distant location

texts:
I'm using Eagle Autorouter. This works fine.

But sometimes via is created in the distant location.

Does anyone know the cause?

Image is using 10mil Grid.
Center-Top small one is the via of this case.


texts: How to check the power output of home amplifier speaker terminals?

texts:
I recently bought a Sony STR-DH800 from eBay and to cut a long story short I'm getting different volume levels using the same speakers across the various speaker terminals.

I have a multimeter and I was wondering if there is a way I can check the output from each speaker terminal so that I can do a comparisons.

The amplifier has a bi-amp feature to allow you to connect the Front A and Front B speaker terminals into a single pair of speakers. However, if you decide not to use the bi-amp you can use Front A and Front B speaker terminals independently to drive two pairs of stereo speakers. This then gives you three modes from a button on the front of the unit to change the speaker configuration:-

SP A
SP B
SP A+B

Sadly the Front A speakers terminals are extremely quiet compared to Front B. I'm not here to further diagnose why it's quiet or whether I've configured something wrong as I've already done all of that, I just need some readings so that I can prove that there is something electrically wrong the amp and try and get my money back or get it repaired.

UPDATE
I connected the two pairs of speakers to the Front B terminals and it drove all 4 speakers at full volume. From a good judgement I would say I was over 90dB. But there is something wrong here as I haven't set the Surround Back (aka Front B) terminals to bi-amp. In fact there doesn't seem to be any difference setting Front B or bi-amp.

I should note that I connected both pairs of speaker to Front A and they significantly drop in proportion to Front B. In other words both pairs of speakers connected to front A aren't the same volume but are very low compared Front B.


texts:
I'm building an EMG circuit and have chosen to use the AD8237 as my front end amplifier.
It's setup as below:

R20 is actually a digital POT so I can change the gain.  The amp is setup with a gain of ~ 80.
The following signals are hooked to the following places:

VSS - Negative terminal of (4.2V) LiPo Battery
VCC - Positive termainal of (4.2V) LiPo Battery
GND - Ground electrode (connected on bone on elbow), also see diagram below
IN+ CH1 - Positive electrode, placed on bicep muscle
IN- CH1 - Negative electrode, placed on bicep muscle about 3 cm away from the positive electrode

The GND signal is also setup as below in my circuit:

Just a simple buffered voltage divider to give a voltage half way between Vcc and Vss.  Although as a side note this is showing a 0.5V offset from what I expect.

When I have the circuit hooked up as described, with the amplifier gain set to about 80, the output signal (measured at DiffAmpOut_CH1) is a 50-100mV pk-pk signal with a 1V offset like below.

There are more amplification/filtering stages after this however I'm focusing only on this section of the circuit as they are unimportant until this first stage is working.  My problem is that I need more like a 1-2v pk-pk signal not a 50mv pk-pk signal. To achieve this I'll need to remove the DC offset.  The offset at the output is 1V with 80x gain on the amp so the offset at the input to the amplifier must be around 12.5mV. This amplifier has very good CMRR (106dB) so it seems unlikely that the issue is caused from a common offset.  It seems like one of my inputs is always 12mV higher than the other.  I'm not sure what could be causing this however.


texts: PID controller best when no model of process available?

texts:
While PID control is the best controller in an observer without a
  model of the process... (https://en.wikipedia.org/wiki/PID_controller#Limitations_of_PID_control)

What is this supposed to mean? Or more correctly, what would be a proof that PID controller indeed is the best controller when a model of process is not available?


texts: Buzzer not buzzing in proteus 7.7v - used ic555

texts:
I am trying to simulate a mosquito repellent in Proteus v7.7. It uses an NE555 in astable mode.
My problem is that I cannot hear the buzzer buzzing.
I checked my circuit and everything seems correct to me. Could you please tell me what is wrong?


texts: Why does moving this ammeter change the polarity of the applied voltage?

texts:
Note: I'm not an electrical engineer, I'm a materials engineer.  So maybe this question has an obvious answer, but I couldn't find one with a Google search.  I also have no idea if I tagged this properly, sorry!

I was reading through this open access paper on evolvable circuit components and was pretty much following it, right up until the demonstration section at the end.  In the caption to the following figure, the authors note:

  Measuring the current at the terminal where VIn1 is applied, as shown in panel c, causes the current from both inputs to have the same sign.

Why should the ammeter have that effect when it's moved from the position in a to the position in c?

(I'm also a bit confused by the final graph in b; does the negative current reading here imply that current is flowing back from ground when V2 is applied after training?)


texts: Using transistor as switch, why is load always on the collector

texts:
I find in reference circuits that when BJT is used as switch when it will be used in saturation mode, the load is always at the collector. For NPN the emitter is connected to the ground, for PNP the emitter is connected to power supply like this:

Why is the load always at the collector and not the other way around?
Since the transistor is only acting as a switch can one also use an FET instead of BJT?
if one is using BJT for multiplexing multiple 7-segment displays, the current of all the 7 segments shall pass through a transistor. So, when using discrete transistor per 7-segment unit in saturation mode, will the different current gain values of the different transistors lead to difference in brightness of the 7-segment displays?


texts:
Current leakage is apparently an issue with some aluminum Macbooks and other laptops.

https://superuser.com/questions/462244/electric-shock-mild-vibrating-sensation-on-macbook-pro-when-charging

Some of the threads related to this topic advise definitely not ignoring what seems like a minor nuisance: https://superuser.com/a/421029/108081

Putting aside the risk of the typical problem, could this be a greater danger with a voltage spike, like during a lightning storm?  Isn't there a surge protector inside the Magsafe adapter?

I've noticed the "hum" effect for a long time but only recently realized it was current leakage.  Regardless of whether or not the Magsafe's ground pin is defective, the 3-pronged cable is not being used, or the outlet isn't properly grounded, if the "hum" is still felt, doesn't this mean there is a defect inside the laptop?  If there were no defect, would proper grounding be unnecessary, as far as risk goes where the Magsafe is the current source?


texts: Difference between 1oz copper thickness and 1.5oz finished copper for PCB fabrication?

texts:
I am working on the new PCB Fab notice for the PCB board house, and try to come up with a good explanation of differences of the 2 terms below and try to determine which term I should use to avoid confusion:

1oz copper thickness
1.5 oz finished copper

Any thought or suggestion?


texts:
I am going to incorporate this 4017 in a circuit and I have downloaded its datasheet,but I can't understand some parts of it.

What is the max Vdd current? And the max current & voltage of the CLOCK pin?

Here is the data sheet.


texts: Soldering question: Which Kester solder to use (Resin-Five vs. SN63) in what situation

texts:
I have been soldering electronics projects for 60+ years but have forgotten (if I ever knew) which solder to use in which application.
Besides a few short lengths of unknown origin, I have 2 large rolls of Kester solder: Kester Resin-Five 40/60 (.092 dia) and Kester Solid Wire SN63 (.050 dia). The Resin-Five solder seems to melt at a lower temperature and flow better, but the finer Solid Wire solder looks cleaner like it is more appropriate for PCB soldering of small digital components.
I also have several choices of soldering irons ranging from 20-40 watt pencils to a bigger dual-power Weller soldering gun.  I have used the smaller irons on PCB components and the larger gun for larger line voltage wiring.
Can anyone give me some guidance on which solder and gun to use in various situations?
Thanks


texts: Can I use a transistor to control my garage door?

texts: I am using an Arduino to make a keypad to open my garage door when the correct pass code is entered. I plan on using a MOSFET to connect the two wires that currently go to the push button in the garage. The label on the garage door opener says it's 30 volts going to the push button.  The MOSFET is rated at 60V 30A. Will this work, or do I need to use a relay?


texts: What type of audio output does this symbol represent?

texts: I have this picture. I want left, left ground, right and right ground output. Pin. But I can't understand it. Can somebody please help me. Thanks.


texts:
I want to ask the opposite of this question.

Here are the purpose of the bit scramblers:

Encrypt, but LFSR (and other used) bit-scramblers are breakable.
Clock recovery, but it is done by the 8b/
DC offset, but it is done by the 8b/10b.
(Are there any?)

Why do we need bit scrambling when using 8b/10b?


texts: How should I implement a USB-C Power Mux Circuit with Enable?

texts:
I'm designing a device which can be powered by DC IN or USB-C. The USB-C is a DRP, so it may be tasked either with sinking or sourcing power.
The DC IN may be between 5V and 20V, so from here I'll refer to it as the 20V rail. There's a big buck converter responsible for making a 5V rail out of whatever appears on the 20V rail.
The actual PD communication is already done, so assume my uC knows how to control these inputs, I just need to design a circuit that it can control.
There are a couple power scenarios I'd like to handle:

20V rail is not present, 5V rail is not present, 5V is present at USB C VBUS, so let the USB C VBUS onto the 5V rail

20V rail is not present, 5V rail is not present, some 9-20V is present on USB C VBUS after PD negotiation, so let the USB C VBUS onto the 20V rail

20V rail is not present, 5V rail present, PD negotiation can control between HiZ and 5V on the USB C VBUS

20V rail is present, 5V rail present, PD negotiation can control between HiZ, 5V, and 20V on the USB C VBUS

It would seem to me that the ideal chip for this would be a 22V+ tolerant 2 to 1 power multiplexer with enable and select, where enable blocks both forward and reverse current. I was not so lucky to find such a chip.
I could also use two load switches, but then accidentally having both inputs be high at the same time would cause a link between the 20V rail and the 5V rail, which would be catastrophic. Additionally, I think the handoff between the two voltages could be tricky to time. Both of these would seem to be addressed with the use of a power mux instead.
Here's a sketch of what I'm thinking for the circuit:

The questions I have are:

Is my load switch correct (and optimal) for using 3.3V to control a 5-20V high side load with current being blocked in both directions when disabled? I'm still a little shaky with MOSFET design. If I understand correctly, when I open the MOSFET closer to the power source, the other MOSFET's body diode will be used momentarily to create enough Vgs to saturate the second one as well, thus there would be no diode drop though my load switch. I'm also open to a single chip solution for this if one exists.
Would the TPS2124 be a good choice for a power mux here? I can't tell from the datasheet if Vout > Vin is allowed. I'm also open to suggestions.

Thanks in advance for all of your help


texts: Buffer SWD programming pins for 20VDC tolerance?

texts:
I have an application that I'd like to use some existing connector pins for SWD programming. All exposed pins and pads on the device must be 20VDC tolerant.
I think I could solve this with an appropriate buffer that would turn anything over 3.4V or 5.1V into a logic level safe voltage, but cause propagation delays.
Or
I think I need a clamping circuit that doesn't change the relatively weak 3.3V or 5V SWD signals enough to matter.
... Or a combination of both, clamping for incoming and buffering for outgoing?
The largest concern is board size I need to devote to this, and then that it's robust/reliable and still allows for "reasonable" programming/debugging speeds.
Any suggestions? Thanks


texts: Failed to trigger capacitive touchscreen of my iPhone XS

texts:
As you can see in the title, I am trying to trigger the capacitive touchscreen of my iPhone XS but it does not work as intended.
Here first a picture of my Arduino setup (the cardboard represent my iPhone):

Here is my code:
void setup()
 {
   pinMode(13,OUTPUT);
   digitalWrite(13,LOW);
 }

 void loop()
 {
     digitalWrite(13,LOW);
     delay(500);
     digitalWrite(13,HIGH);
     delay(500);
 }

Here is the model of relay I am using:
https://pdf1.alldatasheet.fr/datasheet-pdf/view/1132028/SONGLERELAY/SRD-05VDC-SL-C.html
I Am using Eco Fused copper foil tape.
I tried to follow this tutorial found on internet:
https://www.instructables.com/Arduino-Plays-Stick-Hero/
The fact is that If I use a coin (1 centime coin as I live in France), it work kind of from the moment it's scotched with normal scotch but is inconsistent and same if I used a piece of copper tape which have the size of the coin or more bigger one.
But I need to press a little button on an application which require to use a little piece of copper tape but from the moment the scotch seems to be more little than the coin, like for example on the picture, it does not work at all.
Is there a way to get this working on a little zone because when I try to press my phone screen with my finger by applying the less surface possible, I think way less surface than the copper tape on the picture, it work with no problem so I don't really get it.
If someone can help me to fix it, I would really appreciate, maybe I am missing an component !
Have a good day.
Thank you.


texts: What mosfet do I use in induction heater?

texts:
I have been building an induction heater based off this schematic. I have tried using irfp250m mosfets. Works like a charm. But whenever I put a too big piece of iron inside the coil, the mosfets soon self destruct. However if I place a smaller piece in the coil, it heats up orange hot. The power supply isn’t the problem here. It’s a 48v 50a telecom switching power supply. So I wanted to increase the amount or iron I can put in the coil. I went out and got me some more unique mosfets.  First one I got is a 2SK1812. Worked perfectly while idling, however self destructs when something is placed in the coil. Even the smallest piece that worked with the irfp250m.  The 2sk1812 is rated for a higher voltage and amperage, so why didn’t it work? Is it the RDS on? Does the switching speed(Trr) matter?

Ok so I was like on these won’t work so I replaced the blown 2sk’s with 2 beefy APT43M60L 600v 45A N ch mosfets. These ones worked but got hot really fast.  That is definitely the RDSon causing that. But still doesn’t work with the same chunk of iron that the irfp250m mosfets did well with. The apt43’s also self destructed.

So why did these problems happen? And what are some mosfets that could work with high power induction heater?


texts:
I am trying to double the voltage out from a 1.5V battery using an MCP618 op-amp as a learning experience prior to using the op-amp to amplify the output from a set of strain gauges set up in a Wheatstone bridge.

However, to check that I wasn't doing something totally dumb, I wanted to start from a circuit with a unity gain.  That circuit is as below.

simulate this circuit – Schematic created using CircuitLab

The voltage measured by VM1 equaled zero, which makes sense to me.  If the op-amp is trying to make the difference from V+ to V- equal, then V+ should equal the output.  Hence, I then tried to make this into a voltage doubling circuit, as shown below.

simulate this circuit

Now, when I measure from the output to the input, I would anticipate reading a doubled voltage.  Instead, I read a potential difference of ~1.5 V (i.e., the input is 1.5 V higher than the output).  By measuring from the output to the negative terminal of the battery, the output from the op amp is 23 mV from zero, relative to that negative terminal.

What am I screwing up here?

---------------------------EDIT 1/15--------------------------------

I've redone the circuit as suggested in the initial answers (or so I believe), but am still seeing the same behavior as before.  The circuit I'm now using is as follows:

simulate this circuit

In short, when I run this, I see a potential difference of 20 mV between nodes A and B on the diagram, which doesn't change when I disconnect the 1.5 V source.  Any help is appreciated.

EDIT #2 (1/15): Added the 10k from battery to non-inverting input, and checked for shorts and such.  No change in behavior, even with a new chip.  I did notice that there was a current spike (1 amp!) on chip's power supply when I turned it on after plugging the new one in (which made the chip nice and toasty), so I added a 15k resistor between the power supply and the Vss pin as well.  Upon putting a new chip in place with this 15k resistor on the Vss pin, it didn't give me a current spike, but it did give me still the same behavior as before.  Circuit now appears as follows:

simulate this circuit

ERROR FOUND (between chair and breadboard): supply voltage to op amp was connected to Vss instead of Vdd.  Circuit (less the resistor between +5V and Vdd) now exhibits the desired behavior.


texts:
simulate this circuit – Schematic created using CircuitLab

hi,

in the above circuit, why wont the motor run?
connecting the motor - to Drain of the mosfet and the motor starts spinning.
and how do you rename a "custom device" - i would like to change P1/U2.

U2 = ULN2003a

http://www.irf.com/product-info/datasheets/data/irlb8743pbf.pdf
http://www.ti.com/lit/ds/symlink/uln2003a.pdf


texts: I have an Arduino Nano and when I power it either via USB or VIN it heats up very quickly. Before it started to overheat I heard a spark but didn't see which pin sparked and I think that's the problem. During the spark I had a L293N motor drivers one IN pin was connected to the board. I tried uploading the blink sketch and disconnecting everything but still having the same problem. I can't see any visual issues on the board. How may I fix it?


texts:
I'm planning a PCB project with PCI-E connector. After looking some docs about PCI-E. I find one problem about the fanout the PCI-E gold fingers, the X16 pinout defines as below (part of whole 164 pins):

You see, the opposite side of two GND pins are one data pair. So, If I want to connect the GND pins to ground plane, I may can't avoid using blind vias. So, I wonder if blind via is necessary for such situation? Are there any routing method or suggestions to avoid using of blind vias?


texts: How to find out the voltage on Arduino ADC input?

texts:
I am a complete beginner in the field of electrical engineering. I have this temperature sensor with 2k Ohm resistance on 25°C. I have wired it parallel to a 3.6k Ohm resistor to lower the overall resistance, powered by the 5V output on my Arduino Duemilanove with ATmega168 chip. I connected this to an analog input channel.

My problem is how to translate the numbers I read from my analog input into temperature in °C.

My approach is the following:

1/R ＝ 1/\$R_1\$ + 1/\$R_2\$, so 1/R = 1/3600 \$\Omega\$ + 1/2000 \$\Omega\$, so R = 1286 \$\Omega\$.
R = U / I <=> R \$\times\$ I = U, hence 1286 \$\Omega\$ \$\times\$ I = U
Arduino analog input maps from 0V to 5V to 0..1023. Using this I can translate a given number into a voltage, and use the formula above (and a resistance table for that sensor) to calculate the currently measured temperature.

As you can see, I have not figured out yet what I would be in these calculations. Is my approach correct, and what is I in this context?

I would appreciate a hint in the right direction. Thanks in advance.


texts: LTspice model for LM317 and the calculators gives different output voltages for the same resistors values

texts:
I found LTspice model for LM317 in a very trustable recommended source, downloaded and simulated the following circuit:

As you see above in LTspice for R1=240 and R2=1.5k the output voltage is around 9.46V.

But online calculators calculates for the same resistors different output voltages than LTspice. Here some examples:

9.14V
9.06V
Another 9.06V

If someone encountered this or eligible to verify whether the LTspice model is correct, why is there big difference? Is this LTspice model reliable?


texts: Inline Mains Switch with microcontroller

texts:
I'm looking for some inspirations/references as to how I might go about designing a switch powered by a microcontroller, switching a mains powered device . My ultimate objective is to create a zigbee controlled switch that simply switches the mains power on and off. This device would be controlled by another microcontroller able to communicate wirelessly via zigbee. My key requirement is for the inline switch to be simple to connect, allowing the mains line to enter one side and exit the other, allowing it to be fitted in any existing scenario where a device might be powered by a traditional switch.  My questions are:

• In my design, what approach might I take to split off the the AC power and transform to DC allowing my microcontroller to operate without needing an independent low voltage DC power supply?

• How do I integrate a relay into my design to switch the mains power from the same mains source?

I appreciate there are many considerations about safe design when handling mains voltage. It strikes me there must be some very similar open source hardware designs out there that would help me learn how to best achieve this.

Grateful for any advice or references.

Many thanks,
Greg


texts: speed control of induction motor using dimmer

texts:
i want to control the speed of induction motor single phase (about 1.5 kw /  2 hp  \ 220 volt \ 50 hz and 1400rpm) using dimmer(triac) , i try this circuit
i chang the value of C1 to get best control
the circuit worked acceptably but not very well , not requested
i Noticed that the range of control the speed with variable resistance R1
is tight and when i Reduce the Speed  the motor have some noise
1-how i can solve the proplem of the thigt range of the control speed?
2-how i can solve the proplem of the noise in the motor?
3- what the Disadvantages and Damage of this kind of control on the motor?
and by this kind of control As a result i reduce the voltage so the torque will be reduce , are i am right ? so what is the benefits?
for circuit Rs= 27 Ω ,5 watt and c1 = 300nf ,400volt and the load  is the motor ant triac is bta41


texts: Are there any disadvantages in high pin count MCU?

texts: I have to choose a mcu for a project and I only need 4 I/O pins. However, microcontrollers with higher computational power usually have many pins. Are there any disadvantages using a high pin count mcu, apart from size and price?


texts: MPLAB X IDE on computer emulation / debugging how to set input values?

texts: Is there any way I could emulate input into chip using the free emulator, when debugging my code to see if it responds correctly into input?


texts: What technique is more suitable for multiple (10+) simultanious bluetooth communications? CC2564

texts:
I am developing an industrial hardware that communicates via BLE 5.0. The design is this: multiple devices: (10, 20 devices) communicates with an high bitrate (around 20 bytes every 50 ms, so around 150 3.2 kbps). Sometimes is also the central that communicates, but it is mostly peripheral vs. central.
I am developing this architecture with CC2564 trasmitters (https://www.ti.com/lit/ds/symlink/cc2564.pdf?ts=1616973324278&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FCC2564).
Now, I have the next choices:

pairing all devices, before the transmission
connect via BLE connection, without pairing, and manage data trasmission using carachteristic read or write.
not connecting devices, but transmit messages using advertisement system.

The question is: what approach would you use to avoid collapsing data, increase the range and the reliability of the trasmission, that is crucial, and avoid losing data, or, even worst, the connection?
Do you see any possible problems that I should know or intrinsic limit of bluetooth for this kind of application?
Thank you for your suggestions.


texts:
I am very inexperienced at electronics, but I have recently tried to connect a wireless chip to my microcontroller. I soldered some header pins to my board to allow me to remove the chip when needed or to change it.

Trying to test it by sending a message and printing it to a terminal on my PC.

However when I press send the chip doesn't appear to be working, but if I remove the chip and wiggle it about as I am inserting it the message sends. This indicates to me that there is a poor connection somewhere. But I have no idea how I would trace this.

Any suggestions?


texts: MSP432 Programming and boundary scan issues (4-Wire, 2-Wire and SWD)

texts:
I have reached a predicament.

I have a production board with an MSP432 that will not program. To provide some context, I am using the XDS110 that is supplied with the MSP432 launchpad and am simply running jumper wires (approx 10cm) to the target. After some basic troubleshooting, I have come to a conclusion that the MSP432 would have to be factory reset.

I have followed the factory reset procedure outlined by TI but the process fails when running the GEL file, giving me an error of:

CS_DAP_0: Trouble Writing Register DP_RESET: (Error -1170 @ 0x2) Unable to access the DAP. Reset the device, and retry the operation. If error persists, confirm configuration, power-cycle the board, and/or try more reliable JTAG settings (e.g. lower TCLK). (Emulation package 7.0.48.0)

No connection possible. This could be caused by the device having gone to low power mode and disabling JTAG PINs. You have the option to either toggle reset or try to use SWD instead.

MSP432_Factory_Reset() cannot be evaluated.
Target failed to write register DP_RESET
     at DP_RESET=1 [msp432_factory_reset.gel:44]
     at MSP432_Factory_Reset()

This test was performed with identical settings to the MSP launchpad defaults with the only exception of a lowered JTAG clock speed on 100kHz.

This leads me to my other findings when performing a boundary scan test on all different debugging modes, the only mode that fails is 2-Wire mode with an error of '-233' (0xffffff17). One would think that if the 4-Wire mode was to pass, the 2-Wire mode would pass as well.

Question: Could this be a hardware issue? Is it a case of missing pull up/down resistors? (from my understanding the MSP432 datasheet instructs only a pull down on SWO)

I have attached an image of the MSP432 and its layout, it is of note that R11 (DCOR) and L3 are not populated.

I have hit a wall in terms of debugging, and am not sure what to do next as the official TI procedure fails. Any advice would be appreciated, thank you.

UPDATE: I decided to probe around a bit more and found that Vcore is reading around 240mV, when other sources indicate that it should be ~1.2V.
I believe that a low Vcore is leading to this issue, however I do not see anything on the board that would cause it to attain such a low value. I am operating the device in LDO mode.


texts:
For an audio device (Sharp IM-DR420H MiniDisc recorder), I am looking for a solution to merge the ground signals together. The recorder uses a '1-bit digital amplifier, full-bridge output, and 4-pole earphone plug'. The type of equipment you connect to the device should have 4 poles, or by using the 4-pole to 3-pole adaptor, according to the manual.

The pinout looks like this:

So the ground signals are completely separated.

Now my question is; how can I merge these two ground signals, as I don't have any 4-pole headphones or the official adaptor. When connected directly to a 3-pole to RCA lead, it sounds ok, but there is a huge reduction in stereo separation and spaciousness.

As I don't believe the official adaptor uses something other than a couple of resistors and maybe capacitors, I thought I could easily build one myself.

Also I saw a post about merging two audio channels together;
https://electronics.stackexchange.com/a/136134/117666

Would that be the same principle for 'only' the ground signals?

The specifications of the output power;

The related schematic diagram with the audio circuitry outlined in red;


texts:
I am using a 12V to +-5V NMH1205DC converter. When I measure the output voltage without a load, it measures about +-8V. This converter will power a low current circuit that contains several OpAmps. Their maximum voltage ratings are +-5.5V. I am afraid that this overvoltage from the converter might kill the OpAmps. Is that a problem? How to fix it?

When I clamp the outputs with 1k load resistor, the voltage drops to +-5.2V. Is that an acceptable solution?

Also, page 4 suggests how to reduce output ripple. They provide a the table of suggested values for a 5mV p-p max ripple, and for my part those are 47uH and 4.7uF. If I want to reduce the ripple even further, say to 1mV p-p or 500uV p-p, which values should I use?


texts: Opamp: Compensate to achieve constant gain

texts:
I have been trying to achieve a constant gain across an LM318 opamp in a differential amplifier configuration ranging from 500Hz to about 500kHz.
The opamp has a bandwidth of 15Mhz.
Since the gain is dependent on frequency, I have not been successful.
If the input amplitude is constant 600mV peak-to-peak, I would like the output to be, for example 4V peak-to-peak at all frequencies of interest.
After some research, the only way this appears to be possible is to use another opamp in the feedback loop to increase the gain at higher frequencies (active feedback).
Is this true, or is there a better way to do this, and if so, what would it be?
I would appreciate any help on the subject.
Thank you.
Edit: Schematic of what I'm trying to achieve:


texts: Calculating resistance for driving motors off Arduino

texts:
I'm planning on driving two motors off an Arduino. Here are the two motors I'm using, requiring 3VDC and 350mA. It was recommended I use this H-Bridge to control the two of them, capable of driving 4.5V-36V at 1 amp.

Considering the power output from the H-bridge is substantially higher than required by the motors, I'm assuming I'll need some resistors in the sequence

Arduino >> H-Bridge >> Resistor >> Motor

I used Ohms's law to calculate I'll need one \$\dfrac{V}{I} = \dfrac{3 V}{0.35 mA} = 9 \Omega \$ 1 watt resistor in conjunction with the power in on each of the motors.

Is this right? I'm a software engineer so I'm not very knowledgeable in this area.


texts: Distribution of the frequency drift of oscillators

texts:
I'm investigated the effects of oscillator inaccuracy on timing related applications and I'm therefore interested in the distribution of the frequency drift for common oscillators such as LC or Crystal-based ones. Surely they are different for each oscillator and each oscillator type but I'm just interested in the rough characteristics of the distribution.

Assuming e.g. that the frequency drift can be expressed as
$$\tilde{f} = f * ( 1 + n_f )$$
where f is the nominal frequency, I'm looking for the distribution of n_f. Does it e.g. make sense to assume it to be Gaussian?

Or alternatively for the estimate t_hat of the real time t and assuming it to be given by
$$ \hat{t} = t*(1 + n_t) + d $$
where d is the clock offset, I'm looking for the characteristics of n_t.

Sketch of scenario:

I have an oscillator/clock (very small, i.e. < 1.5 mm^3, and low energy consumption) that I want to operate for, say, 48 hours.

Before operation and after operation I synchronize with an atomic clock.
I'm interested in the inaccuracy of the time measurements in the operation time if I measure time intervals, which are in order of a second, and the absolute time when I started to measure that interval.

What are the most relevant error components that lead to the inaccuracy in the two timing measurements (the interval time and the absolute time)?


texts:
I am just getting into electronics and been reading about voltage dividers, I wanted to build one myself. I have built the below schematics on a breadboard and I am not getting the voltages I want.

below are my calculations.

R3:

bleed = (20mA + 30mA) * .1 = 5mA
R3 = 3.3/0.005 = 660Ω (really used a 680Ω)

R2:

R2 = (10 - 3.3) / 25mA = 268Ω (really used a 27Ω)

R1:

R1 = (12 - 10) / 55mA = 36Ω (really used a 33Ω)

After R1 I am getting a reading of 11.59V, and after R2 I am getting 8.26V.

I can't seem to figure out what I got wrong in my calculation.

Picture of breadboard:


texts:
I am not sure if this is right place for this question.
NFC bandwidth can go up to 50KB per second, and there are NFC business cards that have EPROM up to 8kb.
Is there possibility to put micro SD card of 1,2 or 8gb and connect it with NFC chip  to communicate with NFC reader and transfer data from that SD card? Basically like a USB stick but with NFC protocol and embedded in business card. Is this possible at all as I don't know if SD cards can work in passive mode, but if EPROM chips of 8kb can work in passive mode I am questioning if there is possibility for SD cards as well.


texts: Trying to view CM and DM components of a signal on a two channel digital scope screen

texts:
I want learn how to view the CM and DM components of a signal on a usual two channel scope. The reason for this to be able to verify whether a noise superimposed on a signal is CM orDM.

Regarding my below drawing, I thought if I can measure Va and Vb with two seperate channels I might use the MATH function to see the CM and DM components. Imagine Test Device in the figure is a power supply with its plus and negative terminals shown and you observed noise/interference at some point by a scope.

And now you want to check whether what you have seen as noise is due to CM or DM interference.

Would the following setup work:

In this case about the figure above I’m stuck at two points:

Where should be the probe ground leads be connected?

What would plot the CM and DM if MATH function is used? Would Ch1+Ch2 plot the common mode part of the signal?


texts: Different voltage sources in parallel with a diode

texts:
I have a simple problem, I got stuck with it.

simulate this circuit – Schematic created using CircuitLab

I have to plot the voltage drop on resistor R as a function of its value, the V, and r. The diode is ideal.

So I think about this system as two parallel voltage sources: one with a 2V voltage and 2r internal resistance, and another with V voltage, r internal resistance. The diode won't let current flow to the second supply, so there will be no current between them.

My idea was that the voltage of the parallel system output will be the higher supply's voltage: 2V, and it will have an internal resistance of 2r, so it will induce a current in R like 2V/(2r+R). But a simulation showed me different results (I used the http://www.falstad.com/circuit/ simulator applet.)

So, how could I mathematically combine two different voltage and internal resistance voltage supplies?


texts: Peculiar noise when observing a square wave

texts:
I'm using the following function generator: http://www.farnell.com/datasheets/499058.pdf?_ga=1.129729036.1263433037.1467971694 and a Tektronix TDS 1002B scope for some measurments.
Most of the time I use the function generator's square wave output(at %50 duty-cycle) as an input to a circuit.

The issue is that I see a lightning-like random flickering noise when I observe the rising or falling edges of the squarewave above 200Hz.
It is hard to describe what I see so I uploaded a very short record of the scope screen.
Here is how it looks like:
https://youtu.be/hOy5-SOk2mg

I would like to describe the setup briefly to elimitae some possible causes.
To observe the signal from the function generator, I first hook up the function generator's squarewave output to the scope's channel (I also use a 50ohm terminator to eliminate ringing).
Below is how the BNC is connected to 50ohm output of the function generator:

And here below is how BNC is connected to the scope channel(If I don't use 50ohm terminator I still have the noise plus ringing):

I first thought the noise could be coming from the scope itself so I hooked up the scope probe to its own builtin 1kHz output. But the edges were very clean without any weird interference.
I also tried the setup with different BNC coax cables and still having the same issue. I also don't observe this noise on the scope screen only if the function generator's output is set below 200Hz.

Do you have any idea what could be the issue here? And could it be fixed with a different setup.

Edit:

Below is a photo from the scope screen. I had to take tens of photos to catch when the noise hits. Below when the noise strikes:

As I wrote this happens randomly all of a sudden. So the noise is not continuously there that was the reason why I had uploaded a video.

Another clearer photo when the noise appears:

Edit 2:

Some new observations:

1-) I used 2-prong power plugs and the issue still existed. So it is not related to ground loops

2-) I cannot sample fast enough 10ns signals with my DAQ device

3-) If I use 20MHz bandwidth instead of 60MHz in settings the noise becomes better

4-) Noise only exists for the square wave output not for sinusidal or triangle

  And I guess the most important observation is the following:

  When I set the function generator main output's Vpp anything less than
  2V the noise disappears totally. And I hear a 'tick' sound the momemnt
  Vpp is adjusted below 2V (a tick sound similar to when you hear in CC
  limiting in a power supply). There is obviously some relation with
  function generator's pulse output amplitude but have no idea what it
  could be. But under 2Vpp if I play with duty cycle noise appears again for different duty cycles..


texts: What dictates voltage levels on a PC's serial port pins?

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I'm currently seeing an inconsistency between the serial ports of 2 PCs I'm working with, and can't seem to hone in on the cause. I'm trying to control an external scanner, which works perfectly fine on one machine, but not at all on the other.

All of the pins on both machines have the same voltage level (0V on pins 1, 2, 4, 5, 8, 9, and 5V on pin 6), except for 2 -- pins 3 and 7. On the "good" machine, pin 3 is normally at -5V, and pin 7 is normally at 5V, whereas on the "bad" machine, pin 3 is normally at around -11V, and more surprisingly, pin 7 is at around -11V too.

I've actually taken the PCI Express to RS232 card out of the "good" machine and tried it in the "bad" machine, but still no luck -- it seems as though the problem is independent of the expansion card (I've tried many).

Does anyone have any insight into what is causing the different voltage levels? I'm not as worried about the magnitude, as one PC may be offering more power in this regard, but the RTS pin has different states on both machines.


texts: DC voltmeter and full wave bridge rectifier in Proteus

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I am trying to measure the average voltage on a resistor but I see always zero like below:

I connected ground but the result was the same.
When I add a parallel capacitor in R1, there is no problem but otherwise I can't get a good reading. My friend tried this circuit on Multisim and there was no extreme situation like I have.


texts:
I'm currently building my first stepper motor driver, a bipolar stepper,
4.5-48V 1A phase current with 4.5 Ohm phase resistance. I've built the
circuit of the L6206 following the "Typical application" in the data
sheet and controlling it with an AVR ATmega.

Basically it works fine, but the current is much too high. At 12V my
2.5A power supply switches off and the L6206 gets hot very quick. At 7V
the current at stand still is more than 1.5A, running it is at 1A.

So I suppose I have to limit the current, but I am not sure how. The
datasheet mentions an integrated PWM current control but I can't find
any further information on how to use it. It explains how to the
overcurrent protection can be used to roughly regulate the load current
what I have tried, it works but the motor then runs choppy and I feel
sorry for it.

Another thing I don't understand is why the driver still works if I
remove the charge pump?


texts: How can I use 5 LEDs for additive colour mixing using the CIE 1931 Chromaticity diagram?

texts:
I am using Amber, Green, Blue, White (2500K - Colour Temperature) and White (6500K - Colour Temperature) LEDs, and altering their brightness to get to a specific colour and brightness (luminous flux) on the CIE 1931 Chromaticity diagram.
I am specifing xamber, yamber, xgreen, ygreen, xblue, yblue, xwhite2500K, ywhite2500K, xwhite6500K, ywhite6500K. These are the respective coordinates of each LED on the CIE 1931 diagram. I am also specifying xmix and ymix, which is the coordinate of the colour I want to get to, and Ymix, which is the brightness of the colour I want to get to.
The solution I want to get is the Yamber, Ygreen, Yblue, Ywhite2500K and Ywhite6500K brightness values for each LED to get to xmix, ymix and Ymix.
I can do this right now, but the problem is is that my method only gives me one possible combination of the brightnesses of the LEDs. Sometimes this combination is impossible to achieve (ie Yblue is too high - my blue LED simply can't shine as bright as the solution requires).
I was wondering if there is a way to get lots of different combinations of brightness for the 5 LEDs to get to my desired colour and brightness, so I can choose which ones are optimal and within range of possible values.
I can go into more detail if you would like, such as the formulas and method I use to get my singular solution if it helps.
This is my first question here so if there is something I have done wrong or something you could suggest that I do to make the question more answerable please let me know.
Thank you very much.
EDIT:
The calculation I have used to get a combination of Yamber, Ygreen, Yblue, Ywhite2500K and Ywhite6500K is as follows:
Firstly we set up a 3x5 matrix A:

Then we take the pseudo inverse of this matrix and call the result B.
I did this in MATLAB like so:
B = pinv(A);
Then we multiply B by another matrix, and we have our result in the form of a 5x1 Matrix:

Attaching images seemed easier because of the formatting. Hope this helps.


texts: Drop voltage from 3.3 V to 2.5 V with step-down dc-dc converter or diode

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I'm building a status display for a meeting room. The door to the meeting room gets sunlight from the side, so I will hang the lamp turned 90 degrees and the red status light will point towards the long corridor.

On Amazon it says for the DC-DC converters I looked at that you need 1.5 V difference between the input voltage (in my case < 3.3 V) and the output voltage (in my case < 2.5 V), which is not the case (0.8 V). Can someone tell me if there is such a thing and how I find it. Alternatively, I would also be grateful if someone recommends a suitable diode (I have no experience with this).

The (connection of the) solar panel is under the battery. The LEDs are conntected on the left side. They will eat a maximum of 16 mA together with the last DC-DC converter at 2.5 V. Of course at higher voltage they eat more, but that would break ma LOLIN at pin 5 (yellow cable).

I have three DC-DC converters inside (one is inside the D1 mini pro). I didn't want to connect the D1 mini pro with 3.3 V, but connected it with 5 V, so that the internal DC-DC converter doesn't have to be desoldered or reverse floated around and maybe additional modules with 5 V could be connected. In the beginning it worked, i.e. the LEDs were on. After the voltage dropped or something else happened, I now have to replace the last DC-DC converter (I need 2.5 volt but get ~ 2 volt only).


texts:
I'm working on an arduino project. The arduino have a 5V output up to 500mA and a 3.3V output up to 50mA. The problem is i have to power several circuits under 3.3V who consume between 8mA and 20mA each. 8 circuit maximum, so 160mA max. So I can use the builtin output to power two of them but will need to drop the voltage of the 5V output to 3.3V.

I've found 3 options :

Series resistors, but with 160mA I will need some 2 Watts resistor and I don't have some actually.
Diodes in series, seems ok for me, got a bunch of 1N4007 but as the load can change, the voltage drop will change too, and let's say I have only one device connected, I will have much more than the 3.3V...
Voltage regulator, but I can't find some for 5->3.3, or really expensive (around 10€, 15$)

Any ideas ?