texts: How can I test a ballast circuit without?

texts:
I have an old table lamp. I want to repair it. It has an external ballast circuit and 9 watt fluorescent lamp (PL). I don't know the circuit is working or not. Is there any way to check it without buying a new lamp  ? What inductance and what resistance values would be reasonable to expect from a good ballast?

If circuit is okay then I can go for buying a new lamp, otherwise I want to repair the circuit.

Any help would be appreciated.

Update
As per the answer and few comments, I have bought a new lamp. After fixing some soldering and wires it is working now. Thank you all.

Here is the link for the lamp I used: http://www.lighting.philips.com/main/prof/lamps/compact-fluorescent-non-integrated/pl-s/pl-s-2-pin/927901786503_EU/product


texts:
I am trying to buffer 8192 words of data from an IO Port to RAM using DMA hardware of dsPIC33EP512GM710. I have configured the interrupt source INT0 as the source for the DMA hardware. I am using MPLAB SIM to simulate. I am facing one major roadblock.
I am able to set only 10 LSB bits of the DMA start address register DMA0STAL. Even after running DMA0STAL = 0x0FFFF; , The special function register window shows that DMA0STAL is set to 0x03FF.
I have tried using the other DMA hardware - DMA 1,2 and 3 and still same thing happens with the DMAxSTAL register. I tried simulating in both MPLAB IDE and MPLAB X IDE. I also tried assigning value to DMAxSTAL in both assembly and C and still only 10 bits can be changed.
Thank you for your help.
PS:
I have not noticed this issue with any other register.
Screenshot:


texts:
I'm trying to get the hang of op-amps, and I've run into a stop. I'm trying to implement a differential op-amp, where the two inputs are from a wheatstone bridge. Please see attached diagram

The problem I'm facing, is that the inputs \$V_{left}\$ and \$V_{right}\$ change, due to the impedance seen to the op-amp. I do not want these voltages to change, since that will cause the output of the op amp to be "wrong".

The immediate solution I see is to decrease the resistance of the bridge, and increase the resistance of the op amp. This only minimizes the error, and does not remove it.
The op-amp is ment to output \$V_{o}=2.2(V_{right}-V_{left})\$. How do I deal with this? Thx in advance! :)


texts: Why am I getting different Voltage Losses?

texts:
The step-down transformer has a ratio of 10:1

$$P_{globe}=V_{globe}\cdot I_{globe}$$
$$P_{globe}=V_{globe}\cdot I_{globe}=\left( 2 \right)\cdot I_{globe}=4\ \mbox{W}$$
$$I_{globe}=2\; \mbox{A}\; ∴\; I=2\cdot \frac{1}{10}=0.2\; \mbox{A}$$
$$V_{loss}=IR=\left( 0.2 \right)\left( 2+2 \right)=0.8\; \mbox{V}$$
$$However...$$
$$V_{loss}=V_{supply}-\frac{10}{1}V_{globe}=20.8\sqrt{2}-10\left( 2 \right)≈9.4\; \mbox{V}$$

What's wrong here?


texts:
I was thinking to build some test equipment for a RS485 bus, but Would like to get some suggestions on how I can introduce bursts of spikes in a "safe" way without damaging the connected equipment. Maybe even introduce DC offsets or AC ripples.
I only need some suggestion on how to "drive" the bus to introduce this in a safe way, the actual generation of bursts, offsets or AC will be done by a microcontroller.
EDIT
On request I will elaborate a bit more.
During software stress test (loading the bus with data traffic), I would like to introduce burst of noise or in other ways "invalidate" the signal on an electrical level to simulate, for example noise introduced when a motor start, or hum from an AC line. Our customers don't always install things the proper way and we get all kind of wierd behaviour because of this. Behaviours we can't repeat in a controlled environment (in our lab).
I know RS485 is a balanced line so it should be a lot more tollerant, but still, there are issues.
The Idea is to connect this test-device on an installation and start to disturb the signal.
Things I could think of would be to hold one (or both) of the balanced lines high or low, regardless of the driver's output. I guess the drivers can handle the case if more than one driver accidently drives in the opposite direction, without breaking. I can have a microcontroller to control when and how to do this and in this way create "bursts" and inject pulses in the middle of the traffic.
This isn't to test the hardware, more to test the software and error handling.
So I would like to get some suggestions on how to hold the bus lines high or low in a "safe" way while the RS485 driver is sending.
I hope this made it more clear now.


texts: Which connector system for serial row of PCB plus cables?

texts:
i have a series of PCB modules with signal in and signal out that need to be connected via cables.
I want to find a connector system that uses male/female on both PCB as well as cables so i can make sure that the user can only hook up signal out to signal in via cables. It would look like "PCB Male" <-> "Cable Female" <-> "Cable Male" <-> "PCB Female".
The board connector needs to have a 2.54mm pitch and preferably polarised.
Any idea which system can do that? checked JST and Molex but couln't


texts: The transient instantaneous power dissipation of an impedance

texts:
Suppose we have a resistor of value R in parallel with an inductor of value L with series resistance R. The impedance of the network is $$Z= R\frac{sL+R}{sL+2R}.$$

simulate this circuit – Schematic created using CircuitLab
The
Voltage V0(t) across the impedance can be found by the inverse Laplace transform of Z(s)I0(s).
The total power going into the impedance is $$ P_{total}(t)=V_0(t)I_0(t).$$
The current through the R branch is $$I_{R}(t)=\frac{V_0(t)}{R} $$ and the RL branch current is $$ I_L(t)=I_0(t)-I_R(t). $$
From analysis of the circuit, we know that at any point in time, the instantaneous power resistive power dissipation is $$P_R(t)=I_R(t)^2R+I_L(t)^2R.$$ We also know that the instantaneous power energizing the inductor is $$P_L(t)=\frac{1}{2}L\frac{dI_L(t)^2}{dt}$$ such that $$P_{total}(t)=P_L(t)+P_R(t)$$ is always true.
We can define equivalents voltages such that $$V_{Req}(t)=\frac{P_R(t)}{I_0(t)}$$ and $$V_{Leq}(t)=\frac{P_L(t)}{I_0(t)}$$ such that $$V_0(t)=V_Leq(t)+V_Req(t).$$ These equivalent voltages can easily be calculated in the time domain using the above equations for any arbitrary I0(t).
The transfer function Z gives a relationship between I0(t) and the V0(t). The question is: is there such a closed form transfer function that directly relates VReq(t) and VLeq(t) with any I0(t)? Also, is it possible to determine the the instantaneous transient power dissipation of an arbitrary transfer function subject to an arbitrary input current without knowing what the circuit looks like?


texts: Current transformer for current sensing at Low Voltage AC

texts:
I have 230V/50HZ AC to 12V/5A step down transformer. Is it possible to measure the current at the secondary (Low Voltage AC)side of the transformer?
is it possible to use regular CT coil(which is used to measure the current @230V AC)


texts: PCB relays for switching 700-1000V analog signal

texts:
I'd like to switch the polarity of a differential high voltage line that carries up to a 750V (+/-375V per conductor) analog signal. The easiest way to do this appears to be to use a dual-pole dual-throw (DPDT) relay, with each conductor connected to opposite pins on each pole. My problem is that the parts I've found only support up to around 300V.

I think the constraints of my problem require an electromechanical relay over e.g. a solid state one:

low contact resistance
bipolar
linear

I don't care about driving current (the load is a capacitor) or switching speed. The control voltage can be anything below 20V or so.

Does anyone know of a suitable electromechanical relay that could switch this voltage, or another way to solve this problem?


texts: I connected a commercially available LED to a circuit in series  without any resistor with a telephone line in India. The voltage available from the telephone jack is 48-54V DC with Positive Grounded and the max current is limited to 40-60 mA by the controlling cards. Why am I able to use the LED without fail? My question is how did the LED withstand  60mA current?


texts: External pull-down resistors on Xilinx XC95144XL

texts:
I need your help on the input termination of the Xilinx XC9500XL series.

I have a Xilinx CPLD XC95144XL that performs as a LED matrix controller as well as a parallel-in serial-out shift register. A total of 48 signals is connected as inputs. 14 outputs are controlling a LED matrix that display these inputs. The PISO register is interfaced from a PIC microcontroller that reads the inputs and also sets the clock.

Some of the inputs are active-high, others are active low (they are actually the redundant signal components of a first-fail-safe design). Not all of the inputs are always connected, depending on the availability of connected devices that control the inputs. So I need to keep the inputs in the inactive state by pull resistors in case the inputs are not driven. My problem is that I need a pull-down on the active-high inputs and a pull-up on the active-low inputs, but the CPLD won't read the pull-down inputs as LOW.

The Xilinx Application Note XAPP784 states:

  Avoid pull-down resistors on pins.
  All Xilinx CPLDs include additional circuitry on an I/O pin beyond just the I/O buffer. This
  includes ESD as well as circuits that manage power up behavior. For example:
  a. XC9500 has High-Z during power on
  b. XC9500XL/XV has High-Z during power on, then a keeper latch
  c. XPLA3 has High-Z during power on, then a keeper “half latch”
  d. CoolRunner-II has High-Z during power on, then a keeper latch
  Pull-down resistors “fight” the internal pin electronics, which may misbehave due to the
  external pull-down. For the most predictable behavior, avoid pin pull-down resistors.

My design has a 47k pull-down (to GND) on some and a 47k pull-up (to 5V) resistor on other inputs. All inputs additionally have a 1k series resistor. In the Xilinx ISE I set the Fitter setting -terminate to "float" to disable the internal pull-up.

simulate this circuit – Schematic created using CircuitLab

So when I start up the system, all inputs that are not actively driven, are read as '1'. But as soon as I touch those input with a multimeter to measure the input voltage, the CPLD reads the inputs as they are pulled by the external resistor (visible on the LED matrix as well as on the shifted data).

Can someone point me into a direction on how to truly disable the internal pull-circuitry? It seems to me that the "float" setting is not the complete truth.

Thank you,
Ulminpoika


texts: Buffer capacitors' role in boost power supply design?

texts:
In the power supply design, there are always smaller value capacitors placed at the output.What is the main role played by these capacitors in the module? Check the screenshot attached and I am referring to C7.

simulate this circuit – Schematic created using CircuitLab


texts: Capacitor across Vlo and Vhi on DAQ, switching power supply

texts: I have a switching power supply (RC Esc).  I am measuring the input voltage from battery using a voltage divider.   The Divider is attached to a differential DAQ.  I have very large transient spikes in both the voltage and current (current shunt).  I can suppress a lot of the spike by placing a capacitor across Vlo and Vhi right before going into DAQ.  Is this common practice and what is the math involved in the spike reduction / cutoff frequency.


texts: What's the meaning of a Bode Plot when talking about nonperiodic inputs?

texts:
The bode plot itself is built based on a transfer function, regardless of the input signal that will excite the circuit. Based on what I've learned, the bode plot show us how the response amplitude and phase will react when we change the input's frequency.

However, I can only understand the meaning of the plot when the input is a sinusoidal signal. When the input is a non-periodic function, I can't see what would be the meaning of the bode plot, since I can't understand how would be possible to change the "frequency" of a non-periodic function.

So, my question is: Is the bode plot only meaningful when we are analysing a circuit that is excited by a periodic signal? If not, what would be the meaning of the "frequency" (x-axis) of the plot when the input is non-periodic?

I'm a bit confused because I always see bode plot examples when the instructor draw the bode plot of any transfer function, without caring if the circuit will be excited by a period function or not.

Thank you !


texts: Where can I find a transformer that will step up a 12v input to around 400v?

texts:
So i'm trying to build an ultrasonic levitator by following the build on mike's electric stuff's channel h ttps://youtu.be/qy1w6rTpC2g . I've set everything up same as he did, following the schematic.

I'm using a standard power supply rated 12V 0-6A. When I power it up and have my oscilliscope attatched to the output of the FET I get a square wave that looks like this.

It seems to look ok to me. I've gone through a load of old ATX power supplies to find transformers but no matter how I connct them to my driver circuit it has no affect on the transducer and I've tried absolutely every combination of pins and windings possible many times. Sometimes I get the same voltage at Vin and Vout, sometimes Vout is arround 40v but I've never been able to get it high enough to drive the transducer correctly. Is there any where I can buy a transformer that will suit this purpose as an individual component or what other appliances could I potentially scavenge one from ? or have I done something completely wrong? I am quite new to electronics.

Thank You in advance


texts: How to design an AND gate for 24V AC Thermostat Connection

texts:
I have a two stage furnace with a heat pump, and a thermostat that isn't capable of controlling the second stage of the furnace when in heat pump mode.
However, I can configure it in such a way that I get two 24CVAC outputs when I want it to engage the second stage of the gas furnace, and either one of them should engage the first stage. I need to design something like an AND gate and and OR for two 24VAC outputs:
Current Outputs:

Heat Stage 1 (labeled Y1): Heat Pump Only (No Gas Furnace)
Heat Stage 2 (labeled Y2): Heat Pump + Gas Furnace on Low
Heat Stage 3 / Aux Heat (labeled W1): Gas Furnace on Low

I need to keep Aux Heat to be Low, as in the coldest winter months I have to select Aux Heat only as it's too cold for the heat pump. However, when the thermostat calls for Heat Stage 2 AND Heat Stage 3 (which it never would do in Aux Heat mode), I want to provide the 24VAC signal to the Gas Furnace on High.
Desired Outputs:

Heat Pump (Y1) - No change
Gas Furnace on Low - Y2 OR W1 (24VAC)
Gas Furnace on High - Y2 AND W1 (24VAC)

Such that when Y2 & W1 are carrying 24VAC, I then have a new 24VAC output that is effectively an AND gate between them for HIGH, but either one triggers LOW.
Were this DC, I could just easily use a relay. I could probably also rectify the AC to DC, and then use an AND Gate IC or Relay. However, I'm not that familiar with working with AC like this - is there a better way to do this?
EDIT
Someone commented briefly that I could use a 24VAC relay - and this seems like it could easily work to suit my needs here. Is there a solid state / non relay way to do this with AC?
Table 1. List of inputs and outputs.
Input 1: Thermostat Stage 2 (24VAC)
Input 2: Thermostat Stage 3 / Aux Heat (24VAC)
Output 1: Input 1 AND Input 2 (24VAC for Gas Furnace HIGH)
Output 2: Input 1 OR Input 2 (24VAC for Gas Furnace LOW)

Table 2. Logic table.
Input 1 | Input 2 | Output 1 | Output 2
--------+---------+----------+----------
 Off    | Off     | Off      | Off
 Off    | On      | Off      | On
 On     | Off     | Off      | On
 On     | On      | On       | On


texts: Why does this circuit oscillate and produce sound?

texts:
I've connected an 8-ohm speaker in series with coil. When I apply 5 volts / 500 mA to the combination (coil and speaker), I heard a very high frequency sound (something like whistling).

The coil is not air-cored (I think the core is made of ferrite or iron) and it has about 50 turns.

I would like to know why this circuit oscillates or produce this sound?


texts:
I'm producing a sine signal with the help of a wien bridge circuit. The problem is that the sine wave looks like it's being clipped at the top.

I'm thinking it has something to do with biasing. But the wien bridge circuit uses two stage transisitors.

How do I bias it correctly?


texts:
I have managed to get the frequency (the beat) frequency from an FMCW.
Here is a screen shot of a wall that's detected by the Radar.
I performed an FFT of complex I,Q data.

My questions are
1. How would I convert that peak frequency into range
2. How would I get the velocity using that frequency

Thanks

Here is the code

ResultI = (ResultI/256) -1;
ResultQ = (ResultQ/256) -1;

mixed1 = complex(ResultI, ResultQ);

Win=fft(mixed1,512);

plot(abs(win);

ResultQ(numel(ResultI)) = 0;

mixed1 = complex(ResultI, ResultQ);
L = 512;
Fs = 125000;
NFFT = 2^nextpow2(L);
f = Fs/2*linspace(0,1,NFFT/2+1);
fft_sig = fft(mixed1, NFFT)/L;

shift = fftshift(fft_sig);
plot(abs(shift));

n=0:512;  %N=100
N=length(n);
Ts=0.000001; %period [s]
Fs= 12;  %frequency [Hz]
t=(0:Ts:Ts*n(end));
A=10;
w=0.267*pi*Fs; %oscilation frequency [rad/s]
p=1.2; %phase [rad]

[freq_response,freq_index] = freqz(shift,1,N,Fs);  %N is the number of samples
pM = max(abs(freq_response)); %magnitude
pF = freq_index(abs(freq_response)==pM); %frequency
plot(freq_index,10*log10(abs(freq_response)),'b',pF,10*log10(pM),'r*')
title(sprintf('Peak Frequency = %f Hz (%.1f dB)',pF,10*log10(pM)));
xlabel('Frequency [Hz]')
ylabel('Power [dB]')

f0 = 24.15e12;
lambda = physconst('LightSpeed')/f0;
radvel = dop2speed(pks,lambda)


texts:
All radio receivers seem to use the heterodyne principle. I can see that it will be easier to work with a fixed frequency than demodulating from a wide range. Questions:

what's the difference between heterodyne and superheterodyne
what does a double-superheterodyne add to that
is there a reason why everyone uses the same intermediate frequency? is there something special about 10.7 Mhz which makes it better than 10 Mhz?
is the heterodyne principle also used in modulators?


texts:
so I have to design a circuit which lights up 2 LEDs depending on the output voltage of the Non-Inverting Amplifier. I haven't connected the LEDs in the circuit below because it's not part of the problem I'm facing. The Reference voltages are 0.5Vp and 11Vp as shown in the image, I already designed them using comparator circuits with the voltage divider method.

When I first designed them I didn't use Hysteresis, instead I connected the feedback loop to VCC but that generated noise so I used Hysteresis instead. However, now I'm not sure how the output voltage of 26Vpp on the comparators is calculated. I've tried calculating but I can never get the right answer.

Can anybody help to show how the output voltage of 26Vpp is calculated?


texts: Charging a capacitor. Calculations and PSpice simulation don't match

texts:
I started using PSpice only yesterday and I have a problem with a really simple circuit.

Vs = 2 V

R1 = 1 kΩ

C1 = 50 nF

The switch closes at t = 0 (it's not really needed).

After running a Time Domain analysis and tracing the voltage across the capacitor, I saw that it takes around ~250ms to raise the Vc to Vs.

This seemed like too much time, so I decided to double check in MatLab by graphing a function of voltage across a charging capacitor:

\$\ Vc(t) = Vs \cdot (1- e^{-{{t}\over{RC}}}) \$

where

\$RC = 1kΩ \cdot 50 nF = 0.00005s \$

\$Vs = 2 V\$

I can't post the screenshot of the result, because I don't have enough reputation for another link. But it's easy to check that the Vc reaches 2 V shortly after t = 0.25ms.

Why do I get different results for the same circuit in PSpice?


texts: What is the reverse recovery time in a diode?


texts:
I´m drawing my own PCB and I´m searching for components to use for this purpose.
Since I´m not an expert in this fields, I have some unsolved questions:

(I´m using Eagle Cadsoft) I need to create a custom library for each component that I will use on my PCB? Is there any website where I can find Eagle Libraries and buy the same components?
I would like to use a Power button on the side but the board will be parallel to the button so I was searching for a Button with flat connector. Is there any specific name to call those tactile button (Similar to power button on smartphone)?
I will use some flat connector as FFC cable , how it works the comunication of between microcontroller and unit connected through ffc connector? May I define a particoular communication protocol?


texts: MicroUSB to MCU interface with logical level conversion

texts:
I'm trying to interface a micro USB port to a microcontroller but I'm not sure about something.
The micro USB port will be connected to a computer with a simple USB cable and that will give me a 5V power supply, but the microcontroller its working at 3.3V. My question is the following: Do I need to add some dividers to adjust the level from the data pins (D+ and D-) or I can connect them directly to the microcontroller? If I need the divider, can you help me with a diagram on how to connect them?
Thank you


texts: Low Current and Voltage Power Supply ORing

texts:
I have a low power IC (an RTC module) which draws about 2.5uA average draw at 2.5V.  I want to be able to power this from a coin cell (2V to 3.1V) directly, or from a larger battery pack (3.5 - 20V).
It is also possible for both batteries to be present at the same time.

Here's a way to do that:

simulate this circuit – Schematic created using CircuitLab

Problem is, the load is very low power so if we use Schottky diodes and power the device from a coin cell, leaving the battery pack disconnected then the high leakage current of the schottky diode will likely dominate the overall power draw, flowing backwards through D2, into the regulator and to ground.

If a regular diode were used instead of a Schottky diode for D2, then a larger voltage drop would be introduced.  If we were powering the devices from the Bat Pack then the 2.5V regulator will no longer work because the minimum voltage that the load will run at is 2.4V.  If a 3.3V regulator was used instead, a low-dropout regulator (< 200mV) would be required.  These are quite hard to find with quiescent currents of < 2.5uA.  If the regulator has a high quiescent current then obviously the efficiency is reduced significantly.  Not to mention the significant energy is dissipated in D2 due to the voltage drop across it.

Is there a better way to efficiently OR low current, low voltage power supplies together?


texts: Can an electrical wiring system carry enough current to create an EMP?

texts:
I'm writing a spy story of sorts and I demand realism in my writing. In one of the chapters an agent, working with remote hacking assistance, enters a datacenter to steal digital certificates. When armed police arrive to storm the place and enter the building the remote hackers hack external electrical systems supplying the datacenter with power and send a surge of electrical energy through the datacenter's electrical wiring, creating an EMP throughout the datacenter which knocks out the police's electronic equipment. I was just wondering if this is realistic.

Questions...

Could the average datacenter's electrical wiring carry enough current to create an EMP?
Would circuit breakers or fuses preclude the surge's EMP effects?
Would the electrical power surge damage the electrical wiring and electronic devices commonly found in an average datacenter?


texts: How to make SirfStar IV chip operate as I2C slave only?

texts:
I bought a GPS that has SirfStar GSD4e chipset inside.
I see with the logic analyser that when in I2C mode it is writing to the bus.
I understand by that that it is in master mode.
How can I make it an I2C slave?

In case it is needed the GPS is Maestro Wireless A2235-H.
But I think this implies in every Sirf based GPS module...


texts: Does the location of a program need to be specified when programming a PIC?

texts: I recently purchased a PIC programmer (cheap PIC K150) and I am attempting to program a PIC12F683. Upon reading over the datasheet it states that program memory locations are 0005h to 07ffh since other locations are used for special purposes. Do I need to specify to the programmer a kind of offset or is it done automatically? Does the chip automatically route the program into those memory locations? here is the datasheet PIC12F683


texts: I am a beginner in electronics and am trying to build a small device that vibrates every n seconds while the device is on. I have done some research and found that the materials I most likely need are: a vibration motor, a coin cell battery power source, a 555 timer or PIC, and maybe a transistor or resistor. I want the device to be small, and the only function needs to be that it vibrates every n seconds while the device is turned on. I am wondering what the best way to go about building something like this is?


texts: If the external memory (1 MB) in 8086 based system is segmented into code, data, stack and extra which are all 64 kB, what do we do with the rest of the memory? Does it go waste?


texts: AT89LP51ED2 SPI ISP -- First attempt to enter ISP mode after reset yields wrong data back, but second attempt works

texts:
I have a board using an AT89LP51ED2 from Atmel -- this is an 8051-derivative with on-board Flash program memory and a SPI ISP interface, which I am using my Bus Pirate to drive (30kHz speed, pullups ON and wired to the board Vcc, default SPI settings otherwise, the AUX pin driving /RESET).  The ISP protocol is documented by Atmel, both in the datasheet and in this Atmel app note -- overall, it is superficially similar to AVR SPI ISP except for the use of 2 prefix bytes (which makes it incompatible with avrdude).  Programming mode requires an entry command -- the two prefix bytes of 0xAA 0x55 followed by 0xAC 0x53 and a dummy 0x00, which should return 0x53 back to indicate the device is in ISP mode.

So, I have set out to implement the protocol myself, using the Bus Pirate binary SPI mode, its associated Python module, and a bit of custom Python scripting on my own end -- however, I noticed my Python script would only enter ISP mode intermittently.  I was able to reproduce the fault manually using the Bus Pirate's terminal interface, starting from a cold boot of the board:

SPI>a
AUX LOW
SPI>{ 0xaa 0x55 0xac 0x53 0x00 ]
/CS ENABLED
WRITE: 0xAA READ: 0xFF
WRITE: 0x55 READ: 0xFF
WRITE: 0xAC READ: 0xFF
WRITE: 0x53 READ: 0xFF
WRITE: 0x00 READ: 0xA7
/CS DISABLED
SPI>{ 0xaa 0x55 0xac 0x53 0x00 ]
/CS ENABLED
WRITE: 0xAA READ: 0xFF
WRITE: 0x55 READ: 0xAA
WRITE: 0xAC READ: 0x55
WRITE: 0x53 READ: 0xAC
WRITE: 0x00 READ: 0x53
/CS DISABLED
SPI>

The fault in particular is that in the first command, the ISP interface echoes back 0xA7 instead of the 0x53 it should.  Resetting the board allowed me to reproduce it again, and capture the sequence on my oscilloscope, including a glitch LOW for half a clock at the end of the last 0xFF it shifts out:

So, what am I doing wrong?  Is this a protocol issue on my end? Or should I be suspecting a faulty microcontroller, or worse yet, an erratum in the programming implementation?  Should I simply work around this in my ISP script?


texts: Pull up on output pin of Buffer SN74HCT245

texts:
I am using SN74HCT245 Buffer operating on VCC=3.3V. So, I am getting 3.3V at each output pin of buffer (B1 to B8).

But if I want to drive a load with 5V input, what options are available to me by keeping VCC=3.3V?

Is 5V pullup on output pin of buffer is valid option?

Please refer below image where I have connected pull up resistor  R1 (10K) to 5V.


texts: Understanding benefit of higher watts on power bank

texts:
I have seen multiple lithium power banks offering 5000mAh.
The Price can increase substantially for the same mAh but a higher output wattage.

My understanding of a 5000mAh battery is that this power bank can output 5000 milliampheres over 1 hour, or roughly 2500 milliampheres over 2 hours - then it will be drained of its energy

Why would I spend an additional $200 for a battery with the same capacity just a higher watt output?


texts:
For the impatient, you can skip the background.

Background

I'm programming a set of microcontrollers that communicate with SPI. There's one master and n slaves that share the bus. There's no chip select. (It's not a bad design, but n is large and there's not enough space for n extra lines).

It's therefore the responsibility of the slaves to keep their MISO in high impedance and at most one of them speak. This is done by responding only when their id is polled.

Now we'd like to have an initial discovery phase where the master discovers slaves with what ids are attached to it. To make life easier (on some aspects), we'd like to have the id unique (and therefore e.g. 32 bits). This makes it impossible for the master to simply poll ids one by one and see who responds (there are too many possibilities).

To solve this problem, I devised a variation of binary search where the slaves collectively respond and the master is able to quickly find the minimum id. The slave with that id is told to not participate anymore and the algorithm repeats. (Details unimportant).

There's one problem though. The collective response needs to be the logical OR (or logical AND) of all the responses. I've been told that the line can be configured in such a way that the MISO bus can act as a logical OR. What I've been told is:

Set MISO on master as Pull-up and
Set MISO on every slave as Open-drain.

I've tried this, but with even a single slave, this configuration doesn't work (the oscilloscope shows a constant zero on the line). If I configure MISO on the master as high-impedance input, I can see with the oscilloscope that the voltage drops to half where the bits of the outputs from two slaves differ (basically short-circuit I presume).

Note: configuring MISO on master as high-impedance and slaves each as push-pull, I can talk to each of them individually even if there are many of them on the same bus. I mean, I doubt it's a problem of the line itself.

Question

My question is, if this is at all possible, and if so, how can I configure the input and output pins of the master and the slaves so that the shared MISO line would act as logical OR (or logical AND)?

Edit

Turned out it becomes an OR with negative-true logic (basically an AND).
The problem with single slave was resolved with writing 1 to the pull-up pin on the master. Previously it had an initial state of 0.

Edit 2

Turned out the ST slave overrides my GPIO configuration of MISO as open-drain and was forcing it high when one was written. I resolved to silencing SPI and outputting MISO in this particular case manually.


texts: LTspice simulation with multiple transistor in single package

texts:
Here is the transistor using for LTspice circuit simulation.
But it comes as package with PNP and NPN.
Here is the link of the model as well.

How can I use single transistor alone for simulation


texts:
900Mhz Operation

This is a BJT mixer design I found on google

From my understanding in order to use a BJT amplifier as a mixer you have to be in the 1dB compression point.

Question: Am I wrong ?

If not...here is a BJT I found and here is a low compression point for it.

Now on to the manufactured Mixers

It looks like on mouser the mixers are design to provide best performance for a specific IF so you are limited by RF_In and FL_LO see Mouser Picture

Question: The BJT Mixer... will it mix anything ? I don't care what IF looks like I just want the product of two signals.


texts:
How to estimate current drawn by microcontroller(on the ADC port) when interfaced to a module/IC/sensor theoretically?

MCU manual: https://nxp.com/docs/en/data-sheet/LPC2131_32_34_36_38.pdf


texts: When wiring IR Phototransistor, why is a pulldown resistor needed?

texts:
My phototransistor looks like the one here, wired like this:

I don't know the exact model or anything like that. It came in an Arduino kit and was labeled "flame sensor". I used an arduino to connect mine and Serial.print values from 0-1023. It was pretty much a fire detector. Why is a 10k resistor needed to connect to ground? I understand why it is needed when reading the state of push buttons. Why is it needed in this case? If I remove it, the ir phototransistor reads 1023.


texts: What PIC processor was this HEX-file meant for?


texts: Turn a circuit on and off when a capacitor reaches a certain voltage

texts:
I have a circuit that takes an input voltage of 0.5-1.5 volts and uses it to charge a supercapacitor up to around 4 volts. However, I only need the capacitor to be charged up to 3 volts. What is the simplest way with commonly available discrete components (including resistors, capacitors, NPN and PNP transistors, power transistors/power MOSFETs, 2N6027 PUTs, and various diodes) to turn off power to the charging circuit when the capacitor's voltage goes over 3 volts and turn it on when the voltage drops below around 2.8 volts?

simulate this circuit – Schematic created using CircuitLab


texts: Addressing registers with I2C STM32F0 HAL libraries

texts:
I'm very new to using STM's CUBE and HAL_libraries. I'm using an STM32F0 microcontroller with 32 pins. The schematic for I2C is correct.
So I need a little help here.

I have a capacitive sensor (FDC1004) that uses I2C communication.  I have to write these registers to read the data.

How could I correctly send START request form master to slave (slave address is A0)?

How to set pointer to 0x0C register?

Datasheet sees (Register 0x0C:bit[7:4]) to 1.) I don't know, how to do that? And finally how to READ from the same register?
Plus I have to wait DONE_x field (Register 0x0C:bits[3:0]) before I read it?

But I don't know if I am addressing the right registers! Because I don't get any data back from the sensor!

Here is my code:

int I2Ccomm ()
{

    HAL_I2C_Master_Transmit(&hi2c1,0xA1,0x0C, 10, 100); //start bit and pointer to register
    HAL_Delay(50);
    HAL_I2C_Master_Transmit(&hi2c1,0xA1,0x054, 10, 100); // setting the register
    HAL_Delay(50);

    HAL_I2C_Master_Receive(&hi2c1, 0xA0, 0x0C, 10, 100); //read from this register
    HAL_Delay(50);
    HAL_I2C_Master_Receive(&hi2c1, 0xA0, 0x02, 10, 100); //read data from register

    return ReadREG[1];
}


texts:
We are working on a hoverboard. It has a Hall sensor with 5 wires and this weird connector. I can't find its name and the hoverboard has no documentation with its BOM.

Has anyone already seen it?


texts: Use of umbilicals with Vacuum Circuit Breakers

texts: I am a trainee systems engineer and have been tasked with drawing up symbols for mimics for a SCADA system. One of the symbols I have been asked to draw up is for a vacuum circuit breaker. When it is isolated an umbilical cable is supposed to be attached. I tried reading up on what the umbilical is supposed to do but couldn't find anything useful. Maybe I am just searching with the wrong keywords. Can anyone on here explain what umbilicals are supposed to do in this context?


texts: (Beginner) Hacking TCM-20DV sony walkman speed control

texts:
I'm hacking the speed control on the TCM-20DV sony walkman. Service manual with schematic here: http://pdfstream.manualsonline.com/d/d92cbef9-a37f-4e2b-92e5-521fab68df58.pdf

Out of the box it has a small-range speed control with two speed tiers (normal and half-speed). I'd like to replace this with a single knob to cover the entire range of speeds. I've tried a few approaches, but I'm very new to electronics and was unable to produce satisfactory results.

The motor has red and black terminals. The red is always ~3.0 volts from the two AA batteries. The motor seems to be controlled by varying the voltage drop across the motor, using some sort of "governor" circuit in the walkman's IC. If the motor takes all 3.0 V, it goes as fast as possible. Conversely, the slowest setting is a drop of ~1.0 V. I found this out by measuring the voltage from the black terminal to ground. Ideally I could just hijack the terminals and make a circuit which lets me adjust the voltage drop across the motor.

My first idea was to use a voltage divider and a potentiometer in parallel.

Oddly when I wired this up, the whole voltage drop happened on R4 and the motor did not do anything. First question: why would the first resistor take the whole drop?

My second idea was just putting a potentiometer in series with the motor, to control the voltage drop across the motor because it seems to have some resistance itself. This sort of worked but the motor oddly wouldn't move without a nudge at higher (but still within range) resistance values. Second question: why would it need physical nudging to get started in this case?

And third question: what is the appropriate approach to this problem? I'm a bit lost, since there are many many techniques I am completely unaware of. And any reference material you think is relevant would be much appreciated!


texts: I am trying to solve this circuit.Can you please tell me if I am in the correct direction.


texts: I need to wire a sensor with analog output to an acquisition system, and the presence of a separate "shield" connection on the DAQ made me thinking: why would I use a shielded 2-wire cable versus a simple coaxial? Given that I only have to transmit an analog signal, in the low frequency range (up to few kHz) and with the highest possible SNR.


texts:
simulate this circuit – Schematic created using CircuitLab

I'm looking to find the value of \$i_1\$, \$v\$, and the total power generated/absorbed.

I started by applying KVL and KCL laws:

\$B: i_1=i_2+i_3\$

\$M_1: 1V=6i_2+5V+54k\Omega\$,

\$M_2: 8V=1.8k\Omega i_3-30i_1+6I_2\$

I tried to solve for \$i_1\$ usuing a matrix, but I didn't get anything close to right answer.

$$ \left[
\begin{array}{ccc|c}
  -30  &6  &1.8k &8 \\
 54k  &6  &0 &-4 \\
 1  &-1  &-1 &0 \\
\end{array}
\right] $$


texts: Relationship between the gate-charge graph and the Vgs waveform

texts:
Right now I'm looking at the PSMN1R1-30PL but this question can apply to any MOSFET.

Figure 15 in the datasheet depicts gate-source voltage as a function of total gate charge:

This graph looks frighteningly similar to the typical waveform of gate-source voltage vs time as a MOSFET is switched on (eg figure 13 of Power MOSFET Basics by IRF):

What is the relationship between these two graphs? Why do they look so similar? What is the meaning of the plateau at ~2.8V Vgs (in Figure 15 of the datasheet), and is it related to the Miller plateau?


texts: Will the IC mess up if the inputs that don't affect the output are disconnected?

texts:
Here's the situation. I'm trying to incorporate ANY decoder in the HC family to decode two bits. I'm also using the eagle autorouter. I decided to go with 74HC139 since its a dual decoder and the pin arrangement is convenient, BUT because I'm not using one of the decoders, I tied pins 13 through 16 to VCC to effectively disable the second decoder, but when routing on the PCB, tying adjacent pins together eliminates routing opportunities and its a major cause of my routing to not complete.

Many chips have an input that controls everything. In this case, the 74HC139 has a gate input G on pin 15 to fully control the output. If it is set to high, all output lines are high regardless of pins 13 and 14 (input bit 0 and 1). Because of this, I begin to think I can just tie pin 15 and 16 together (make G high) and then leave pin 13 and 14 open.

Is this acceptable for an HC series chip or will bad things happen (even though the output is exactly the same regardless of the level of pin 13 and 14)?


texts: iphone 6 plus - Is the resistor R0601 important?

texts:
What is the resistor R0601 important for?
Can a iphone 6 plus work without it ?
What is the meaning of the code (ZQ) in the iphone schematic?

Thanks


texts: Multi staging filters and impedance considerations

texts:
I'm trying to make a MFB Band Pass filter with 80dB attenuation and a bandwidth of around 70hz - 130hz. Each MFB has 40dB attenuation so I want to put two of them and then have two all-pass filters to correct some phase shifts around center frequency. That makes a whopping 4 stage filter. I however have difficulty understanding how I will care about impedances.

Now, I care about impedances. Chosing my bandwidth and frequencies isn't much difficult given some practical equations (selecting Q factor, selecting gain, selecting center freq, etc.). My concern however is in staging, if I put these four (2 MFBs then 2 AllPass) in series, while not using each time a follower.

1) Practically speaking, what would be the best way to make sure I end up with an overall gain of two (for example) considering input and output impedances?
Is there a way in a simulator like Altium to do it fast? Should I litterally just do it by trial error? What designers normally do.

2) And theoretically speaking, what would I do (purely mathematically speaking on paper). I had as an idea to calculate Zout of the MFB with an AC test voltage source at Vout of the MFB (other sources cancelled), and then using
\$
R_{out} = \frac{V_{out}}{I_{out}}
\$

I would then do the same for \$Z_{in}\$ and could then use \$V_{in} = \frac{Z_{in\ n}}{Z_{in\ n} + Z_{out\ n-1}}\$. Does that make sense or am I completely in the wrong?

I'm just trying to make sense of all this so I don't end up having my signal filtered but attenuated too much because of impedances.

Thanks


texts: How to lock the GPIO pin using LCKR register in stm32f10x series?

texts:
I am facing the problem of not able to lock the GPIO pins even after using the LCKK bit sequence to initiate the lock but facing some unknown issues.
My references are from HERE, page number 174
The code I'm trying here is to lock an nth pin pin of port port
void digital_lock(GPIO_TypeDef *port, int pin) {
  if ((port->LCKR & GPIO_LCKR_LCKK) == 1) { //if lock bit is set, reset it to remap the sequence
    port->LCKR |= GPIO_LCKR_LCKK;
    port->LCKR &= ~(GPIO_LCKR_LCKK);  //To modify the bit, this is the sequence
    port->LCKR |= GPIO_LCKR_LCKK;
    port->LCKR &= ~(GPIO_LCKR_LCKK);  //finally clearing the LCKK bit
  }

  port->LCKR |= (1<<pin);
  port->LCKR |= GPIO_LCKR_LCKK;
  port->LCKR &= ~(GPIO_LCKR_LCKK);  //To modify the bit, this is the sequence
  port->LCKR |= GPIO_LCKR_LCKK;
  port->LCKR |= GPIO_LCKR_LCKK; //finally locking the sequence
}

Please correct me if my understanding is wrong, Thank you!


texts: Earth leakage tripping with 3 phase motor

texts:
I'm working in elevator world, i'm now in a strange situation.

The 3 Phase synchronous motor is connected by drive then main controller and a distribution board.

The  faulty earth leakage circuit breaker keeps tripping when the motor just start to rotate.

I disconnected the UVW wires that connect the VFD to the motor, and the break was released and the earth leakage didn't trip.

The problem is that after checking the coils of the motor (UVW) by the continuity test between them and the motor chassis, there was no contact between them.

What is the possible diagnosis for this situation?


texts:
What is the maximum voltage for common music files?

When playing back on a smartphone, if the volume of the smartphone is set to maximum, how much voltage is sent to the earphones of the electric signal?

thanks so much for comment
I’m japanese.
I’m not good at English.
I use google translator.
I want to use a low frequency therapy device on my smartphone. I thought it was dangerous depending on the voltage. And I asked this question. any precautions or dangers?


texts: Easier way to implement a large look-up table in Verilog?

texts:
I am designing the FPGA-based control for a power-electronic AC/DC converter.  This converter has five output voltage levels, so it has 8 switching instances. The levels are given by h, mh, z, ml, l, for high, mid-high, zero, mid-low, and low, respectively.  I am using a time-limited counter as the theta input to reset every 0.02-s, for a 50-Hz reset (so for the 1e-8-s time-step, there are 2e6 time-steps for the 50-Hz cycle). So, these 8 switching instances are also in terms of time-steps.  Moreover, I am using 3 toggle-switch inputs to determine the AC voltage amplitude, i.e., lvl_select. Therefore, there are 2^3=8 total operating modes, each requiring the 8 switching instances. These switching angles are labelled angle1, angle2,.., angle8
Sorry for the background, as it isn't quite necessary for my question.
The way I have implemented this code (in short-hand) is:
input [31:0] theta;
input [2:0] lvl_select;
wire [31:0] angle1, angle2, ..., angle8 [0:7];
output reg h, mh, z, ml, l;
integer i;

assign angle1[0] = 95549;
assign angle2[0] = 904451;
.
.
.
assign angle8[0] = 1914451;

.
.
.

assign angle1[7] = 72345;
assign angle2[7] = 186932;
.
.
.
assign angle8[7] = 1574124;

always @ (posedge clk)
begin
    h = 0;
    mh = 0;
    z = 0;
    ml = 0;
    l = 0;
    for(i = 0; i < 8; i = i+1)
    begin
        if (i == lvl_select)
        begin
                if(theta < angle1[i])
                    z = 1;
                else if (theta < angle2[i])
                    mh = 1;
                else if (theta < angle3[i])
                    h = 1;
                else if (theta < angle4[i])
                    mh = 1;
                else if (theta < angle5[i])
                    z = 1;
                else if (theta < angle6[i])
                    ml = 1;
                else if (theta < angle7[i])
                    l = 1;
                else if (theta < angle8[i])
                    ml = 1;
                else
                    z = 1;
        end
    end
end

This is the code in a nutshell. I haven't verified that it works yet, but I think it should (unless you can see why it shouldn't?).
My question is: is there a way to add all of the 64 angle values in a smarter way?  Right now there are 64 inputs, which I may want to expand in the future.  I have the values in an excel sheet/MATLAB array right now.  Please let me know if you have dealt with similar things in the past, thanks a lot!


texts:
Im trying to do simulation of this circuit but I took this mistake.

After I clicked "Ok(TAMAM)"
then new txt opened:

  Error on line 550 : sine(0 15 1k 0 0 0)    Unable to find definition of
  model "0" Fatal Error: Vo and in are paralleled making an over-defined
  circuit matrix. You will need to correct the circuit or add some
  series resistance.


texts:
I saw this in AN-19 of linear's application notes for a boost converter. It is an error amplifier for a boost converter.

I'm not quite sure what the symbol for Q55 and Q56. My best guess is a current mirror. Am I correct?


texts: I am trying to measure the combined output voltage from this entire circuit, but I can only measure the combined current [ I(V1) ] and the voltages at each resisters. The combined output voltage should be about 0 db.


texts: MIC5216 Achieve minimum quiescent current draw

texts:
I have the MIC5216 as voltage regulator. I am regulating 2 18650 down to 5v in order to supply enough power to my circuit. I am using a 328p as MCU. The chip goes to sleep and is awoken again by an external interrupt. That way I can reduce the energy consumption down to a minimum in order for the batteries to last as long as possible. I managed to get my 328p circuit in sleep mode to 80uA whereas the MIC5216 is using 190uA in a quiet state. I know the 5216 can go as low as 8uA. In order to achieve this low state a voltage of not more than 0.16V has to be applied to the Enable pin. As mentioned, I have 8.2V applied through the 18650's and if I remove these the chip of course will fully stop working and not provide any power at all to my circuit.

My question is: Is there a way, to reduce the power on the enable pin to 0.18V while the 328p is asleep without completely pulling that particular pin low and as soon as an interrupt is triggered to wake the whole circuit up again?

I have not worked with these kind of voltage regulators before so I appreciate any help I can get.

The datasheet for the MIC5216 is here

I am using the standard circuit shown in Figure 5 on page 11.

EDIT1
Sorry for the delay. Below a diagram of my circuit.

As you can see I added sections to the circuit in order to make the visual a little more legible. the voltage regulation part is the one that I have issues with. Even though the voltage supply is stable and provides enough current, I would like to bring it's current idle state closer to the quiescent advertised in the datasheet. My only issue is that I am not quite clear how.

The datasheet speaks about reducing the input voltage on the Enable pin (3) to 0.4V and 0.18V to achieve a quiescent state of 3 to 8μA. I cannot control the regulator with the 328p as it is going to go asleep. I was thinking about a voltage divider from the battery to the enable pin with an output of that above mentioned voltage. That could work up to the point where I want to wake the 328p up. I would now have to increase the voltage on the Enable pin of the regulator to the voltage of the battery for long enough to trigger a constant high on one pin of the MCU. With that idea though I have the problem how do I ensure to provide enough energy to the MCU in order wake it up and trigger that signal.

OK so much for my ideas. Let me know if they are totally bonkers or if there is some merit to them. Let me know if there is another way, maybe in the datasheet, that I missed.

Appreciate any feedback.

regards


texts:
simulate this circuit – Schematic created using CircuitLab

I am trying to build my own SMPS and I was intending on using a P-Channel MOSFET for high side driving the main circuit. The MOSFET in question is the IRF9540. It is rated for continuous (worst case) 18Amps but when I draw 2 amps, it stays closed forever and a component tester no longer sees it as a P-Channel MOSFET but now two resistors. I have kept the Vgs in limit a long with Vds. Is this something I am doing wrong or are my MOSFETS bad (I did buy them from AliExpress but they don't look fake.) Could a too high frequency damage it?

Within the schematic treat the op-amp as a comparator.
Also, I am aware that this hysterectic power supply is not ideal, however, I will be changing to a PWM control.

Update:

I have solved the issue. I have now changed the entire circuit to that it had an opamp controlling a PWM duty cycle fixed at 4kHz. I have achieved 5A of current draw. Thank you for your suggestions.


texts: Datasheet: What is a unit interval (UI) for a PMA?

texts:
This datasheet has a table (see Table 3-2) detailing latencies for the two parts of a 10GB Ethernet PHY, namely the PCS (Physical Coding Sublayer) and PMA (Physical Medium Attachment Sublayer).

While the latency for the PCS is unambiguously defined in clock cycles (for a clock running at 156.25 MHz), the latency for the PMA is given in "UI" (Unit Interval, I assume).

What is the UI in this context? Is it different from a clock cycle?


texts: Magnetic resistance of an electromagnet with varying cross section

texts:
I've been given the following problem:

The magnetic flux density (B) of the air space should be 0.5T. I=5A and the coil has N=200 turns. Calculate the length of the air space e.

What I've done so far:
I've calculated $$\Phi=B\cdot A=7.5\times 10^{-3}Vs$$
$$=\frac{\Theta}{R_{m,Fe}+R_{m,\delta}}=\frac{N\cdot I}{R_{m,Fe}+R_{m,\delta}}$$
$$\Rightarrow R_{m,Fe}+R_{m,\delta}=133,33\times 10^3 \frac{1}{H}$$

My plan is to calculate the magnetic resistance of the iron and use that to calculate the magnetic resistance of the air and from there the length of the air space.

My questions:
Am I going about this the right way?
Given that we have been told to calculate the length of the iron via a middle line, from where should the length of the larger section be calculated?

In other words, does the length run from the dot or the dashed line? Or put another way, is the length of the larger section \$d-e\$ or \$d-e+a\$?
So far, we have only seen magnets which are circular. Does this one need to be treated as a parallel circuit (see below), and if so are my calculations completely wrong?


texts:
So I have this 125khz RFID card and I would like to punch a hole in it so I can have a thin string go through it, making my card to be able to hang from my neck.

Though I have no experience in punching hole to any sort of card, not mentioning an RFID one.

Is it possible to punch a hole through the RFID card and still have it work properly?
How should I punch a hole through the RFID card safely, easily and using some cheap accessible tools (list of alternative ways to punch a hole into RFID card is welcomed)
In the picture below, you can see my RFID card in front of a light source, showing the antenna. On the picture, I put a green circle to the place where I need the hole to be (though I can make the hole a little bit smaller as long as a double-string can pass through). Is that a safe distance? Is the whole too big? Is there a chance that it will break the card?

Picture:

Note: please make your answers to be understandable for an average person like me (who is not deep into this field yet)

RESULT

Thanks to @Passerby for the answer. I suggest using the heated needle method if you have a needle lying around somewhere and don't have any special tools. I can confirm that it works perfectly (see image below)

Also special thanks to @DarkCygnus for his help in finding this StackExchange.


texts: Using motors with arduino without external hardware

texts: I have three small motors, and I know you should use a motor shield or driver when working with the arduino, but would it be safe to use these with the arduino by themselves without a shield? And if so, what would be the best way to work with them and control their speed?


texts: Decreasing ADC Reference vs. Amplifying signal

texts:
I have a sensor interfaced to ADC but the Range I am getting is not enough, so now there are 2 options, Gain up the signal or Reduce ADC Gain.
But as I heard it, reducing ADC gain will cause more noisy output, but then, can't I argue that applying gain to input signal will also gain up noise. are there more aspects than these which will cause noise if I reduce ADC Vref as compared to gaining up signal.


texts: Is the nRF24L01 IRQ line open-collector?

texts:
I need to know whether the nRF24L01(+) has an open-collector IRQ output, or a full push-pull driver. The datasheet doesn't mention this fact.

The reason is that I'm working on a circuit involving two peripherals (an nRF24L01 and another chip) attached to an MCU that has only a single INT pin. If both the devices have open-collector IRQ lines, I can easily just wire them all together with an overall pullup resistor, and all will work fine. If however, the nRF24L01 has a full push/pull driver on the IRQ line, then this is impossible, and instead I'll have to buffer it somehow (perhaps with a 7407 or similar). When the interrupt fires, I can query each device over SPI to enquire which device fired the interrupt.


texts: Do LED have an unproductive base power consumption like incandescent bulbs?

texts:
To generate light from an incandescent body, like a tungsten filament,
the body needs to be heated up to a temperature minimum needed to emmit light from that material.

Up to that minimum temperature, only heat is emitted. Above it, heat and light is emmitted.

What is the related behaviour of LED?

When the current increases from 0 A to the specified standard current, I assume there is some range where the LED does not emmit any light.

What happens in that range - I would guess it's not behaving just as a resistor?


texts:
This is about design of a JPEG compression/decompression scheme on an Altera FPGA. It is possible to have camera or SD card for image input and TV or SD card for image output. However, these interfaces introduce their own complexities.

To keep things simple in the early part of the project and to make it easier to thoroughly test the design, it is desired that it be possible to pass data of an image from MATLAB into the FPGA. MATLAB already has a lot of functions to manipulate data, so it is desired to send data to FPGA and read back the result after processing and compare the FPGA result with the result of identical processing done within MATLAB.

Basically data shall be read back from the FPGA from different stages of the JPEG compression and decompression processor to check how each part of the design is working.

So the question, how do I transmit data from MATLAB to the FPGA and read data back? Is there some tutorial on this somewhere?


texts: Clock domain crossing of a bus between related clocks

texts:
Imagine I want to transfer a bus from a fast clock (i.e., 100MHz) to a slower clock (50MHz). The clocks are related (come from the same MMCM, phase aligned).

The Xilinx Timing Closure User Guide indicates that the tools will take care of the inter-clock domain path requirements, so reading a single bit in the slow clock is safe. My question is: will the tools also make sure that all the bits of in the bus will be synchronised to the same slow clock edge, or is there a risk that some bits may arrive on different cycles without any further constraints?


texts: How do I create a ground on a PCB when I also need a positive and negative voltage supply for an Op Amp? What even is ground?

texts:
So I am using an OPA1612 op amp and I need positive and negative supplies for my application. I intend to use a 9 volt battery.

This is the circuit I plan to use to get a +4.5V and a -4.5V. You can see that my negative probe is connected to the node between the capacitors C3 and C4, and that the voltage at the top and bottom is 4.5 and -4.5 volts respectively. To me it seems that that middle node IS MY GROUND because it is the 0 voltage point. Evidently, the positive terminal of the battery is now at +4.5V and the negative terminal of the battery is at -4.5 volts so my battery no longer has the 0 voltage point right?

NOW HERE IS WHERE THE PROBLEM IS!!!
This is the entire circuit. As you can see I have 3 other ground connections to the 10mH inductor, the potentiometer, and the stereo jack. For the PCB design itself (which I am doing in Altium Designer if that matters), how do I create these ground connections when I am using a single battery???
When I was researching this project I found a device that is identical to what I wanted to make by someone who sells it as a product. Here is his schematic and board.
What in the heck are those H1,H2,H3, and H4 connections and why are they connected to the ground plane????
It seems to me that those H1,H2,H3, and H4 connections are the big holes with the screws in them in that second picture. So does that mean that the screws themselves are the ground???? I am just confused how this guy created a "ground" in his PCB when he split his battery to 4.5 and -4.5 volts.
EDIT:
New question:
In my PCB if I connect the midpoint of the voltage divider to the ground points (10mH inductor, the potentiometer, and the stereo jack) with traces and then connect all of those to a ground copper plane with a via, will that be my ground even if the capacitors C3/C4 and resistors R4/R5 aren't perfectly matched??


texts:
I need to measure and log power, and I want to do it mostly correctly.  I would greatly appreciate a listing of the errors I have made in my method.
I want to measure (and log) the power output of a small 3-phase generator.

Components:

200 w, 24 v, 200 rpm - 3 phase delta generator

200 w buck/boost mppt controller

-10 v to 10 v DATAQ DI-149 data logger

Three 2-ohm, 25 w. resistors

I think logging the voltage is not a problem: measure across the 75k of a 75k/91k pair.  The DI-149 can internally convert to rms and log same.

The DI-149 measures the 20 v. span in increments of 0.02 v.  My plan was to put a 2 ohm resistor between each of the 3 outputs of the generator and the inputs of the MPPT and log the rms voltage drop and convert to current.

I will multiply the rms voltage and calculated current to arrive at power (and then throw in I^2 R to account for the power lost in the resistor?)?

I would be satisfied with +/- 10% accuracy.  Is this going to get me there?


texts:
I built a circuit for ignition system using MOSFET, 555, ignition coil (specs unknown, but current rating is more than 2 A and less than 10 A), SMPS (12 V, 10 A for powering the the whole circuit.)

First I built circuit-1 which has worked but only for a few seconds and temperature of the MOSFET is too high during operation.
Second circuit-2 which is better than circuit-2 but works for 1 minute And still MOSFET is heating (slowly). I built the circuit-2 with reference to (arduino controlled spark plug with ignition coil) @MatsK

My question here is:

Why it is better than the first one and how to choose the RCD components which are connected in parallel with MOSFET in circuit-2?

And I powered the circuit form 12 V, 10 A SMPS and the SMPS is struggling to provide supply and I don't know why (LED in SMPS is flickering during operation)


texts: How to find the relative bandwidth /frequency of a aperiodic signal?

texts: I have a transfer function with a fixed cut off frequency  and I wanted to apply an input proportional to time(x= cont*time), also the condition is to  have a frequency greater than the cut off frequency. Theoretically there will be infinite frequency (fourier transform is \$K/(\omega^2)\$). First of all I wanted to know if such a term called relative bandwidth/frequency is applicable in this scenario and if yes what is the idea behind it.


texts:
I am stuck on a problem with RF Module. I am trying to make an RC Car and facing a lot of problems while doing so.

I am using a 433 Mhz RF module, HT12E-D encoder decoder, L293D and 2 BO motors(DC). My circuit works fine with 100-200 RPM Motor but as soon as I use a faster motor such as a 300 RPM motor the circuit stops receiving any signal due to which the car just moves according to the last signal.

As soon as the high RPM Motor is connected following happens:

The transmission board stops working(when any other button is pressed no response is there)
The data pin LED continuously blinks
Have to stop the motor forcefully to continue transmission

The best guess would be the motor driver circuit is taking up all the current. so I tried two different power sources for the circuit I powered up the Motor Driver circuit using 7.4V li-ion Battery and the receiving part with a regular 9V battery. but still the same problem is there. I am thinking of using another Encoder decoder IC P2272 or HC148. Any suggestions? Please help


texts:
I am working on a project that uses the STM32 Cortex M3 LQFP48.
There is a pin for Anti-tamper (PC13).

I am not concerned with anti-tamper security as this is just a home project.

How can I deactivate this feature on my chip?


texts: Bi- directional level shifter 1.8 - 5V  3.3V

texts:
I have the following issue:

I2C data from various devices with VCC/IO level from 1.8V to 5V should be handled from my controller, but this just tollerates voltages up to 3.3v on IO pins. I had a look at different levelshifter ICs but all I found have the constraint that low Voltage needs to be smaller than high voltage side.

So I came up with this idea:

Is there any issue with this solution?
Does anyone know a better solution?


texts:
I am trying to observe the metastability by simulating (LTSpice) a chain of inverters and probe the signals in between.

The oscillation never happens (I put more than 5 inverters to ensure enough propagation delay.) The signal just stay at 50% of VDD.

The moment that I change another unconnected signal (to the inverter chain) the chain of invrters starts to oscillate but it never shows any metastability and it always starts from 0 then 1 then 0 and so on. I expect that the initial point sometimes starts from 0 and sometimes from 1, but I does not.

How can I simulate a circuit with real metastability in place?


texts: Amplifiy a square wave pulse to drive a 30-60V 100 Ohm PWM load

texts:
Load:

R around 100 ohm.
Operates with PWM.
Has linear average I-V response with square pulse up to 10KHz.
Absolute maximum voltage is 60V.
Absolute maximum average current is V * duty% / R < 100mA.
Absolute maximum power average 0.85W.

Operation Requirement:

Upstream voltage range: 0-60 V.(Can be provided by upstream PSU in CC/CV mode)
Frequency range: 0.5 - 4 kHz.
Duty cycle range: 0%-95%.
Can accept trigger (4 kHz).
Can divide trigger (f/2, f/4, etc.)
Adjustable trigger delay.
Clean waveform.
As small rise and fall time as possible.

I'm not aware of any equipment that fits all those requirement. Most function generators can only reach +/- 10 V. Most bench power supplies only supply DC in CV/CC mode.
Digital I/O devices (Arduino, etc.) with faster clock can achieve all those except for the voltage requirement. Perhaps there is some sort of amplifier that can bring the voltage to 60 V, but DC-DC boost modules only works with DC input/output.


texts: Alternating voltages on vintage calculator circuit board

texts:
I am an electronics novice.

I have a vintage calculator with six secondary wires coming out of its transformer and ending on the board, as shown below:

Using the AC portion of the multimeter, I measured the voltages across the board terminals marked 1 through 6, with the results as follows:

Is it normal to see AC voltages on such a board, or is this because of the age of the product (1979)?

Is the AC voltage changed to DC somewhere on the board?

Is this a "digital" calculator?  (There is an IC chip on the board.)  If so, why is there alternating current, unlike say on an Arduino?


texts: 8051 / EFM8LB1 / programming via C2 after PCON0.STOP := 1?

texts:
Yesterday I wanted to see, how much power my EFM8LB1 uses, when it has just this firmware with bootloader disabled:
.org 0
ljmp 1$
1$:
orl (REG01CN), #8
orl (PCON0), #2

Today I found, that I cannot access it via C2 anymore.
I tried keeping it in reset when powering on and then sending C2 commands... without success...
How can I fix it without dumping the MCU and soldering a new one?
How does that EFM8LB1 decide if the reset means "now we do C2" or "now you run the reset ljmp"?


texts: ATX power supply only 0.1A from 12V rail?

texts:
I have a project which requires a high current output (potentially 60A). Rather than get a lab bench supply, I got hold of a Corsair ATX AX1200i that can supply a max of 100.4A on the 12V wire.

I've followed an instructables guide on getting an ATX to run without being attached to a motherboard (soldered the green wire to a ground) and got a 12V wire from the 24 pin connector, as well as a ground wire.

However, when I connect the supply to my circuit (mainly a Peltier configuration), the peltiers barely cool. What's more is that the current seems to be throttling to 0.1A.

What am I doing wrong/ am I using the wrong connector (+12V wire on the 24pin connector as opposed to any others).


texts:
I have to design the connections between different electrical components inside a wireless equipment. The "traditional" way to connect each one with the others is the PCB, but the particular shape of the volume (imagine a cylinder with a circular section where h1 = 5mm, h2 = 9mm and R = 60mm, see fig. 1) can not contain a "straight" and rigid PCB sheet.

So, what are the best practices to connect components pins' between each other in this kind of case? I have thought of plain and simple wires but it doesn't seem very "professional" to raw solder them, and not very durable neither. The Flexible Printed Circuit Boards seem to be another alternative but how are the components placed on them?


texts: MAX232 circuit, what is the purpose of the capacitors?

texts:
Possible Duplicate:
Can I use 10\$\mu\$F caps in a MAX232?
What is a decoupling capacitor and how do I know if I need one?

Kindly refer to the following typical MAX232 circuit:

I am still not quite sure I understand capacitors correctly, and while building this circuit, I realized that I wasn't understanding what the purposes of the capacitors I was sticking onto the breadboard were. My guess is that they are all used for power conditioning, or decoupling. I am not sure how I would be able to tell which one though.
I am especially confused about the 10 uF capacitor, as it seems like it's just shorting out the GND and VCC pins from my microcontroller.


texts: MPX2200DP signal value reversed when amplified with AD620

texts:
I am trying to measure differential pressure with MPX2200DP. According to the datasheet, the signal is linear and its value ranges from 0 to 40 mV. To be able to use the sensor properly, AD620 instrumentation amplifier is used to amplify the signal to the sensor. The gain is chosen to be 100, and the reference terminal is not connected.
The measured signal show that the output voltage is reversed (i.e. Vout is 4.7 at zero pressure difference) and the it decreases with increasing pressure difference.
If the reference terminal is connected, Vout is dropped to 0.65 volts, and the value remains constant.
IS there any solution that could be applied?


texts:
i am designing a basic AES algorithm on verilog, and i need to split a 1828 bits array into 16 parts each one of 8 bits, for example (basic no 128 length  example), if i receive in my 8 to 2 splitter module 10111011 i need to generate 4 outputs 10 11 10 11

Thanks


texts:
I have a question related to the amplifier circuit given in datasheet of 2SC1946A The circuit looks like this:

I need some info on the inductors used in the circuit. Following are my questions:

What is the value of inductor L? Nothing is mentioned about L except L: Length 10mm. What does it mean?
What is 1D (if D stands for Diameter)? Is it 1 mm diameter? Is it practical to wind a coil of 1 mm diameter with 1.5mm wire?
How to wind 1/2 Turn of a coil? How should it look like?
What is pitch of a coil. Is the gap between 2 parallel lines of winding wires?
Should I change any component in this RF amplifier circuit if the input signal's frequency changes? Which Inductor and Capacitor duo forms the tank in this circuit, which is responsible for 150 MHz frequency?


texts:
I have extracted a strip of 6 LEDs from a LED strip that has these caracteristics :

LED Quantity    300leds
Input Voltage   12V
Power           72W/5M
Cuttable        Every 3LEDS
Package         5 meters/reel

I have calculated that the 300 led draws 6A (http://www.supercircuits.com/resources/tools/volts-watts-amps-converter)
So that 6 LEDs should draw 0,12A (6*6/300)

So I have deduced that powering those 6 leds with 9V, I should use a
9 = 0.12*R
R = 75 ohms

I chose to use a 68 ohms resistance, not having a 75 one.

The problem is that when I wire the circuit, I have half the luminosity using the resistance than when I don't use it. Best of all, if I use a 150 ohm resistance, it's almost the same effect.

What did I miss ?

Thank you for your help.


texts:
I am hoping someone with electrical system knowledge can help clear something up for me. I am considering purchasing an appliance the requires a 230V, 16A outlet. I asked an electrician about wiring on the same Male plug as my dryer which is 220V 30A so I could simply use the same outlet and he said I couldn't do so because I would need a specific 220V 15 amp outlet. But from looking online and reading about amps, it seems that as long as I'm not EXCEEDING the amps, then it shouldn't matter. I am wondering if using this outlet will cause any risk of fire or electrocution because the amperage is higher? Also if it could damage the appliance since it's quite expensive. Any input is really appreciated because I know nothing about this type of thing.

Thank you

EDIT: I am in Canada. The product is Speidel product#22200(pome fruit grinder). Note that in the manual it says its 50 Hz but they now have a version for North America that is 60. I couldn't upload a picture of my outlet but will try again.


texts: Using a schottky diode to improve PNP transistor turn off time

texts:
I was able to use the following schematic to improve the turn off time of a NPN transistor

Adding a schottky diode (even externally to transistor) component reduces the turn off time dramatically.

What is the equivalent circuit for a PNP transistor?


texts:
I need to make a -10 V dc power supply (I_max = 250 mA) to implement in a system where +-10 will be used for powering opamps and a push-pull.

I have a 24 V dc available as power supply.

Regarding the +10 V, I could do it with a switching regulator (buck converter).
However, I cannot find an IC that can output the -10 V without having a very high current (~500-1000 mA) through the inductor (which would probably make it explode).

What DC-DC converter and configuration might I use for this purpose?


texts: How to provide an isolated ground for Arduino?

texts:
I am designing an EEG circuit at home using an Arduino. Now, the circuit calls for the use of a battery and an optocoupler-isolated ground for safety reasons. I am planning to use Fairchild Semiconductor 6N137 optoisolator to isolate the USB power from the microcontroller power.
How do I make the connections for an Arduino. Also, how to separate the Arduino ground from the USB ground.
This is the website I am referring:

  http://people.ece.cornell.edu/land/courses/ece4760/FinalProjects/s2012/cwm55/cwm55_mj294/#

Now, if you scroll down to the Microcontroller Board Design part, that's where things get confusing for me. Can anyone please suggest how to do the same procedures for an Arduino. I am quite new to this subject and I need help. I want the same isolation (even any other isolation will do as long as it works, however, i found that optop isolation is cheaper) with an Arduino.


texts: Advice for using 60 watt peltiers. Is 12V 3A enough to get the job done?

texts:
The weather right now is so bad and hot! A friend of mine runs a mobile stream and his phone refuses to charge when it is hot. His stream crashes because he can't charge his phone or it overheats. Not even shade helps!
I'm thinking about making something for him that would clip onto his phone while he is streaming. A fan might help. But I think a peltier module would work better.

This streamer has access to 12V 6A outputs from a buck boost convertor. He uses multiple 20k mah 5V ~3A battery packs during his cast that power the buck boost. I don't know much about these, so I thought I'd ask. I think a heat sink is needed. But is a fan absolutely necessary? I'm not trying to freeze the phone. Just cool a spot on the back to a reasonable operating temp. Any other information or warnings you have would be great.


texts: Unnexpected Behaviour From Software UART On ATtiny84A AVR

texts:
I am trying to implement a software UART for the ATtiny84A, as it does not come with a UART out of the box.
The following is an example of the UART TX:
DDRB  |= (1 << DDB0); // Set the pin on Port B0 to be an output for UART TX.
PORTB |= (1 << PORTB0); // Default the pin to HIGH for the idle high of the UART

void uart_tx(uint8_t *transmit_data)
{
    uint8_t string_length = strlen(transmit_data);
    for (uint_8t character = 0; character < string_length; character++) // Separate the string into characters.
    {
        PORTB &=~ (1 << PORTB0); // Send a start bit by bringing the UART TX low.
        timer_delay(); // Extra function that generates a delay to generate the appropriate baudrate.

        for (uint8_t character_bit = 0; character_bit < 8; character_bit++) // Separate the character into bits.
        {
            if ((1 << character_bit) & transmit_data[character]) //
            {
                PORTB |= (1 << PORTB0); // Transmit a logical one
                timer_delay(); // Aforementioned delay
            } else {
                PORTB &=~ (1 << PORTB0); // Transmit a logical 0
                timer_delay(); // Aforementioned delay
            }
        }
        PORTB |= (1 << PORTB0); // Transmit a stop bit by bringing UART tx High.
        timer_delay(); // Aforementioned delay
    }
}

uart_tx("ab");

What I would expect as an output is
0100001101 0010001101

however, what I am actually getting is shown in the following

which in terms of bits is
00001000011010010001101...

Taken as a whole, it has little meaning, but upon closer inspection, parts of it are correct. What is wrong about it is the 000 inserted at the beginning, so a more accurate way of looking at it is
?...000 0100001101 0010001101
    ^ start bit?

More specifically: The last two frames are accurate, but mystery data is being inserted at the beginning.
What is very strange, is that If I implement this in a regular C program, it works as I would expect:
#include <stdio.h>
#include <string.h>

void uart_tx(unsigned char *transmit_data)
{
    for (unsigned char character = 0; character < strlen(transmit_data); character++)
    {
        printf("0");
        for (unsigned char character_bit = 0; character_bit < 8; character_bit++)
        {
            if ((1 << character_bit) & transmit_data[character])
            {
                printf("1");
            } else
              {
                printf("0");
            }
        }
        printf("1");
        printf(" ");
    }
}

uart_tx("ab");

outputs
0100001101 0010001101

as expected, so I am very perplexed as to what is going on here.
EDIT: Here is the delay related code
// Initializing the timer
TCCR0A  |=  (1 << WGM01);
TIMSK0  |=  (1 << OCIE0A);
OCR0A   =   52;

// timer function
void timer_delay(void)
{
    TCNT0   =   0;  // Reset the time
    TCCR0B  |=  (1 << CS01); // start the timer with /8 prescaler.
    while (!(TIFR0 & (1 << OCF0A)));    // Wait until the compare interrupt flag is set
    TIFR0   &=~ (1 << OCF0A);   // Reset the Compare flag
    TCCR0B  &=~ (1 << CS01);    // Stop the timer.
}
```


texts: "High Voltage" Logic levels why they are rare

texts:
I'm continuing to dissect and learn from this old (1974) calculator. One thing that surprised my was that the pins of the main IC have both negative and positive voltages 0 to ±28V. Having worked mainly with ICs like the ATMEGA line, PIC controllers and other popular chips, the voltage surprised me.

Am I correct in thinking that modern IC operate at lower voltages so they can pack in more transistors without over heating?

  Inside view of circuit board of Sharp ELSI 8002 Calculator.
  The mystery IC: HD3623 has no online data sheet that I could find, but MK14 at eevblog pointed me to this data sheet showing how a similar calculator works.

When I once destroyed an ATMEGA128 with 12V, was the nature of the destruction heat that melted or burned the traces in the IC making it inoperable? But this old more robust IC must have thicker, more conductive traces.
Is that why it is so big despite doing comparatively less than smaller modern ICs?

There is one advantage to this beefy old IC: It can drive the VFD, which seems to have a -28V grid, directly. Maybe, I should look for a programmable IC that runs at higher voltages? Or would that be frustrating?

Are there IC that meet this description that can be programmed by a novice?

Maybe I should use a logic level converter of some kind instead? I want to be able to repurpose the buttons and the display within the existing case. I like the form factor and quality of the calculator, I want to make it work with a modern micro controller.

  Sharp ELSI 8002 calculator.
  I'm fairly certain that the VFD is the Futaba 9CT06, it's not super well documented, but I can make it do what I want using bench power, so having identified the pins I just need some kind of PWM... I think.

Maybe I should table this project until I've studied more! I've found some people with similar projects, but none with the same VFD.

I've put notes by my main questions for clarity.


texts: Microcontroller and Inductor part placement on PCB

texts: I am laying out a very tight design (space wise) on a PCB. Due to space restrictions, I was forced to placed a microchip microcontroller on the bottom side of a PCB with an inductor on the top side (directly above the microcontroller). It is a 6-layer board, with the stack-up being the following: signal,gnd, signal, signal, power plane, signal. Will this be a problem for the microcontroller? The inductor is 33uH (PN:SRP1265A-330M)


texts:
I have adapted my RF73/RFM73 library for the NRF24L01. These chips are almost identical, except that the RFM73 has a second bank of registers that must be initialized with some magical values. The RFM73 has a special command to switch between the banks, and a bit in the status register that indicates the current bank. This provides a good mechanism to test for the presence of the chip (switch the the other bank and check that the bit in the status register toggles), without disturbing any settings or transmitting anything.

Has anyone found a feature of the NRF24L01 that can be used in a similar way to test for the presence of this chip?


texts: Using DC generator as power source and switch in multi

texts:
I have the following:

DC Generator
5V regulator
lipo charger (5v input),
3.3v regulator,
lipo battery
device requiring 3.3v power

I only want the battery to be connected to the 3.3 regulator (and thus powering the thing) when there is a voltage from the generator. So the generator is effectively a switch and power source for the battery charger.

I have considered using relays and n type mosfets but don't understand enough to know which one to choose and how to wire it up.

Any advice much appreciated (I am new to this).

Cheers,

James.

simulate this circuit – Schematic created using CircuitLab


texts: Is this a MOSFET and if so which legs are which?

texts:
I have this TO-220 package transistor from the (inline) regulator of an electrical hotplate.

The markings on it appear to be

G21
6
9146

and the logo at the start of the last line would suggest that it is a Motorola device - but that is not visible in the photo.

After some simple checks with a DMM, the resistance between pin 1 and 3 (and vice versa) is 56 Ω. Between pins 2 and 3, the resistance is 3.5-4 MΩ and in the same magnitude between pin 3 and 2.

I can't find the datasheet when googling Motorola/MOSFET/9146/Transistor and combinations thereof.

I would like to know whether this is actually a MOSFET and if so, which pin is which? Is it the usual GDS, or something else? A link to a datasheet would be most appreciated.


texts: What is the difference between high precision resistors and current sense resistors

texts:
Actually, I am trying to build a current monitor for a wireless sensor network. I am going to use a current sense resistor as the current will pass through the resistor. By measuring the value of the voltage, the current value can be calculated.

My application is very sensitive as the current that will be measured is in the range of mA, 30 mA maximum.

When it came to buying the resistors I got confused. I found a type of resistor called "precision resistor" that has a very small error, and another one called "current sense resistor".

Here is a picture of a current sense resistor:

So my questions are:

What is the difference between these two types current sense and precision resistors?
How does this current sense resistor differ from the ones we normally use, such as as these 5.6k Ohm, 5% resistors?


texts: Should there really be 1 MΩ resistance between an anti-static wrist strap and a pc?

texts:
My previous question: what exactly is grounded through motherboard standoffs?

The answers suggest that a PC case is grounded in 2 ways:

To the ground plane of the motherboard, through the brass standoffs.

The ground plane is grounded to the PSU, through the ground wires from the 24-pin power connector.

To the PSU case, through screws. (Or surface-to-surface if PC case and PSU case are both unpainted.)

The PSU case and internals are grounded to the earth prong.

  Q1: Is this correct so far?

OEMs like DELL advise to "touch an unpainted metal surface." Thus, when you touch the case, you are directly bonding with:

case
standoffs
ground plane of the motherboard

But when you attach your anti-static wrist strap to the case, there is a 1MΩ resistance between you and the case, because of the 1MΩ resistor in practically every coil cord that comes with a wrist strap.

So, apparently, touching the case, without a resistor, is fine. But a wrist strap should be bonded through a resistor. That's contradictory.

  Q2: Can bonding to the case, through a coil cord without a resistor, do any harm to hardware components?


texts:
I wonder about the "quality difference" between using an secondary side reference + optocoupler to provide voltage feedback in an isolated flyback design and using the third winding of the transformer.

As far es I understand things, "better" regulation is possible with first variant because the tolerances of voltage reference and optocoupler can be much tighter than the tolerance of the transformer winding ratio from secondary side to the third winding.

Now assume that i am happy with an output voltage regulation of +/- 10% , are there other benefits than better output voltage regulation when using the optocoupler variant? I heard that load regulation should be better but don't know why this should be the case.

I also saw that in the variant with third winding, the voltage is more or less (rectification) fed back to the controller FB pin whereas with optocoupler feedback you can directly "bypass the controller's error amplifier" because the optocoupler's feedback is a current signal that can be fed into the output of the controller's error amplifier(i.e. the compensation network). I don' t know if this is somehow a  benefit.

NOTE: All the text abobe assumes an isolated flyback design with current mode regulation and a constant frequency controller. Also, I assume to only have one output, so please no explanations concerning cross regulation topics.


texts: Shortcircuit protection using transistors

texts:
I'm designing a short-circuit protection circuit for x2 AA battery (3V) and I'd like some tips from the community on how can I make it a low power mode circuit.
When V_out is short cirtcuited, the buzzer is activated. The problem is that the power consumption, when there's no load, is located at the 10k resistor. I'd like some tips on how can I make it a better designed circuit.


texts: Should I use Mathematica to understand circuit behavior?

texts:
I've just started learning about circuits from the "Foundations of Analog and Digital Electronic Circuits" book. KCL, KVL, element laws and linear circuits were easy to grasp but then I got the half-wave rectifier.

The solution of this circuit is:
$$i_D = -\frac{v_D-E}{R}$$
$$i_D = I_s(e^\frac{v_D}{v_{TH}} -1 )$$
$$ V_O = V_I - V_D $$

I understand how the equations are derived but not the behavior of the output. The description of the solution is very wordy in the book. As someone who prefers a thorough understanding of how things work and with a solid math background, do you it is useful to invest in learning about Mathematica and plotting circuit equations by myself? What is your preferred way of understanding circuit behavior?


texts: Current taken from USB by STM32F3 Discovery board?

texts: I am trying to find out what the board draws from the USB supply at max MHz. I really don't want to cut cables if this info is available somewhere already


texts: LM393 comparator misbehaving and causing issues

texts:
I've been stuck on (what seems to be) a very unusual issue with a little audio circuit I’m designing. I wonder if anyone here can quickly highlight the flaws of my design and/or offer an insight into what’s going on.
So, the issue is as follows. The circuit pictured below is a simple pair of comparators (LM393) indicating a 'healthy' signal level going into the two respective stereo inputs of an audio mixer. The LEDs illuminate and indicate signal as expected. The issue arises with the second channel, using comparator U5.2. When there is a strong enough signal to illuminate the LED it couples what I would call a 'breakthrough' noise onto my mix bus, which is very unpleasant at high gain levels (the noise is post-channel fader so cannot be faded out). For example, if the music had a strong drum beat each transient would couple a pop/click onto the mix bus.
I cannot work out why this is happening. In an attempt to fault find I wired the IC to swap the two comparators inside the package across the two channels and the fault moves (keeping all external components the same per channel), i.e. the top channel bleeds through distortion and the bottom channel is now clean. This left me very confused as it almost seems like any intrinsic flaws in the circuit are only bad enough to cause the second half of the comparator to misbehave. I also swapped in different manufacturers ICs and this made no difference.
I have not been able to fully understand the mechanism that couples these breakthroughs to the mix bus with my simple test equipment, so I am asking here in a hope that someone more intelligent than I can help.
Many thanks.

EDIT: I'm adding my PCB layouts below. In both cases the side of the comparator which has the longest trace to the LEDs current limiting resistor is the one at fault (R42, R57 / R15, R21). I will try to reduce the trace length and see if that makes a difference.


texts:
I'm designing a schematic and board in Eagle 9.4.0. I have couple different power nets: signal 5V, power 5V (for servos) and power 8V (from battery). I'd like the power nets to be wider than others, so I designed specific net class for them. Matching GND nets will also be wider than others.

The problem is that I want all GNDs to connect at some point. However, when I connect nets (for instance, using a net junction), Eagle asks me, whether I want to merge nets and this is not what I want to do, since I'll have to choose one of two net classes for merged net.

How can I merge two nets in Eagle?


texts: I was wondering about the 'buffer' i/o option for entities in the VHDL language. I have found that my code is much cleaner if I use the 'buffer' option instead of 'out' in any circumstance where I want to act on the outgoing signal somewhere within the entity. I find that I can think of very few reasons to use 'out' ever and I'm tempted to just always use 'buffer' in every case. So, my question is, under what circumstances should I set my outputs as 'out' (even when that means I have to add an extra signal declaration and assignment) and when is it ok to use 'buffer'?


texts: Two MP1584 voltage converters in parallel

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I have a circuit that will need to power different loads at different voltage levels (because they are LEDs of different colors). Can I use several cheap MP1584 modules in parallel (as in: same input, different outputs), or will this have adverse effects (e.g. because they are not synchronized, they all draw current at the same time)? in this case, will a series inductor (on the input) be any help in smoothing the current draw?
The input source will be a supercapacitor (or maybe a small lithium battery), itself powered by a bike dynamo. In particular the input voltage will be low (maximum 6V).


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I'm trying to plot the response of a series RLC circuit to a step function using Matlab.

I've read a bit around it, but I can't get it to work.  Help would be much appreciated.

Here is my Matlab code:

solution = dsolve('square(5, 50) / ((47*10^(-3) * 1*10^(-6))) = D2y + 220/(47*10^(-3)) * Dy + 1/(47*10^(-3) * 1*10^(-6)) * y', 'y(0) = 0', 'Dy(0) = 0', 'x');
ezplot('solution');

The values of the RLC circuit are:
\$R = 220\Omega\$, \$L = 47\$mH and \$C = 1\mu\$F.
The equation for the capacitor voltage (which is what I'm tring to plot) is:
$$v''(t) + \frac{R}{L}v'(t) + \frac{1}{LC}v(t) = \frac{v_s}{LC}$$

\$v(t)\$ is the capacitor voltage and \$v_s\$ is the source voltage (which is a \$5\$Vpp square wave).


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I've just moved to a student accommodation,and they are using sensors to keep the lights in the room on(I'm almost sure that they are PIR). The problem is that they turn off way too quickly and it's really annoying to move around just to keep the lights on.

Can I use IR LEDs and send a pulse every couple of minutes to trigger the sensor? If the answer is yes,should I use a 555 timer in astable mode to pulse an array of LEDs or is there a simpler way of doing this?
(I also don't know how many IR LEDs should be used or what area they should cover to trigger the sensor if this method works)


texts: RFID on humans, is RFID the right method?

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Me and my friends have thought of a few RFID solutions. One of them involve creating RFID tracking system to detect sailors out in the sea within 5km via a tablet or pc. Can this be done?
Reason because sailors dont wear lifejackets. Which we are thinking of creating wristbands. However we do not know if this is the right way to do it because of its range and radiation.
Setting up a reader on a buoy could be done.


texts: Clamp the output of constant current source and capacitor to particular voltage

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How do I need to saturate the output to 891mV?
The current source is 1uA and the capacitor value is 3.76n
I need the output to ramp up till 3.35ms then saturate to 0.891V


texts: Which side of this board is the capacitor polarity indicating?

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In this capacitor slot, which side is the negative and which is the positive? I've never seen this symbol before. I'm assuming the bottom is positive but want to make sure.

Thanks!


texts: How to count the number of the generated PWM pulse on stm32?

texts: I have a stepper motor on TIM2 CH1. When a button is pressed the motor runs. How to count the steps(pulse) the PWM generated while the button was pressed?


texts: Help me Help Students! (Solar Powered, Switched, Red and Green Light Device)

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Good Afternoon,

Excuse my ignorance as I'm not an electrical engineer, I'm just trying to build a device to help grade school students.  In the simplest form, I'm trying to setup a solar powered LED light box.  In searching, I realize that basic topic has been covered many times.  However I couldn't find a schematic that would cover these specifics.

In a relatively small clear acrylic box (say 2" x 4"), I would like to mount a solar panel that would power a single red or green "Super Bright" LED bulb.  It would be switchable as only the red or green LED needs to be illuminated at a time, not both at the same time.

Some of the challenges I foresee are as follows:

The LED must be able to stay illuminated all school day, every day.
As I'm sure you remember, often times the only light in the school
room comes from the overhead florescent tubes.
In order for these to see sustained use, I greatly prefer not to involve batteries as I'm trying to keep build costs down and make sure they are useful long term and not shelved when the batteries die.

Excuse the crude design, but this is what I'm envisioning:

To start playing with, I have already ordered the following:

Single Pole Double Throw, 3-Pin Terminals, On/Off/On Three Position Switch

LED Bulbs

Super Bright LED - Red 10mm COM-08862

625-630nm Red
2.1-2.3VDC Forward Voltage
80mA Forward Current
30 degree viewing angle
10,000-12,000 MCD output

Super Bright LED - Green 10mm COM-08861

515-520nm Green
3.0-3.4VDC Forward Voltage
80mA Forward Current
30 degree viewing angle
16,000-22,000 MCD output

With regards to the housing/box, I'm thinking of using something similar to this:

Can you help point me in the right direction with ideas for the components and/or a schematic to make this work?

update:
Unfortunately they can't be plugged in.  They will need to sit on individual student desks (w/o power) and can't have electrical cords running all around the class (tripping hazard).


texts:
I have designed a SEPIC and Buck converter using the TI power designer tool, which I have individually tested, and proved to be working correctly. They are both of the non-isolated type, but when I use them after one another on the same ground the voltage drops fast very low to around 1V and steadily decrements to around 0.5V.
The specs are:
SEPIC: 12-22v IN, 13.8V OUT, 2A, 400kHz based on LM3488 (which I found is 14.5V OUT in reality so I have used a LM7812CV to drop the voltage)
Buck: 12V-14.5V IN, 5V Out, 2A, 698kHz based on a TPS563231DRLR
I have used my multi-meter to test the output, I have used a small LED as a starting point for my load.
From my basic understanding there should not be a problem using a SEPIC and Buck this way, when using the correct filtering for the high frequency switching noise coming out of the first. Which I have created using a Ferrite Bead. What could be the problem for the invalid voltage output? Perhaps I am missing something elementary as I am not lectured in EE.


texts: Multi Channel Voltage Buffer for BMS Testing

texts:
Question

I have a BMS slave with the LTC6811 battery monitoring IC on the bench.

Since I'm not that eager to test it with the battery stack immediately, I want to build a test jig and I need your help to figure out how to do that because I don't have the slightest idea besides a dozen independent / isolated voltage sources.

The circuitry should be able to be supplied by a single bench power supply with a maximum of 60 V (12 cells with 4.25 V max -> 51 V). It shall provide 12 voltage outputs where the voltage between the outputs should be adjustable via a potentiometer. Meaning pot 1 adjusts the voltage between out 1 and GND; pot 2 adjusts the voltage between out 2 and out 1 and so on. The following sketch illustrates this.

The outputs should have fairly low output impedance. The jig will be used to test voltage monitoring and balancing with currents up to 300 mA which means that the outputs must be capable of sourcing and sinking current.

I'm looking for a schematic snippet that I can arrange twelve times to implement the required function in the best case but I'm also open for partial solutions.

Have a good one
Simon

Solution attempt with parallel topology

I came up with a solution where I put multiple OPA controlled power stages in parallel. The schematic below shows such a building block.

The power stages are supplied with 60 V and controlled by an OPA with level shifted output. The output voltage can be fed back with a voltage divider and I have an idea for reference voltage generation but I haven't worked it out yet.

The problem with this topology is that the output transistors burn a lot of power. This could certainly be tackled if I put the power stages in series - supply-wise - but I don't know how to supply the OPAs in this case.

I'm open for suggestions.