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How would I go about supplying the measurement circuit with multiple batteries ouputting microAmps of current

How would I go about using this same current to power the measuring circuit? Use a low side current sense resistor for the return current pathway. The problem is you need to measure both the test and ...
Voltage Spike's user avatar
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2 votes
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How to implement a blinking led circuit that is dependent on its voltage input?

The NE555 can source and sink 225mA on its output pin so you could just use Vout to drive both LEDs in anti-parallel (assuming that Vout can also source and sink the LED current, or use a voltage ...
vir's user avatar
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4 votes

Using a transistor to digitally press a button

Would this work? Maybe. Maybe not. It depends on the circuit to the switch. The sure-fire wire to do what you want is to use an opto-isolator with a BJT output because it works regardless of how the ...
Davide Andrea's user avatar
1 vote
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How does one add a volume control to this circuit?

How does one add a volume control to this circuit? A volume control is added by replacing resistor 'R4' with a 1 MΩ logarithmic potentiometer. Here's the altered schematic. Changing the ...
vu2nan's user avatar
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1 vote

How does one add a volume control to this circuit?

Replace R4 with an 'A' audio taper (log) potentiometer, such as this kind: If you use a linear ('B' taper) pot, the volume control will be too tetchy at low volume levels and too insensitive at ...
Spehro Pefhany's user avatar
1 vote

How does one add a volume control to this circuit?

LM1875 datasheet mentions this important information: If you add a pot in the feedback network to act as gain control, it will not be useful since minimum gain is 10. If it is set to a lower gain, ...
bobflux's user avatar
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0 votes

How does one add a volume control to this circuit?

Your educated guess is correct, you could replace R6 with a variable resistance (a 3-terminal pot wired as a 2-terminal resistor). But there are other, possibly better, options. Replace R6 When ...
Fabio Barone's user avatar
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3 votes

How does one add a volume control to this circuit?

My uneducated guess is to add a pot at R6. Incorrect. Adding a pot at R6 would be a gain control, not a volume control. With R6 at 0 ohms, the circuit gain would be 1, not 0. That is, there would ...
AnalogKid's user avatar
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5 votes

Transformer with same size symbol meaning

An incorrect assumption confused you. You assumed the transformer was step-up or step-down based on what it looked like to you. The answer is staring you in the face. From your two schematics, it is ...
Dereck's user avatar
  • 500
17 votes

Transformer with same size symbol meaning

I wouldn't count on the number of turns or apparent size of the windings on a schematic symbol as having any relation to the actual turns ratio of the real transformer. From the voltages shown, the ...
Peter Bennett's user avatar
7 votes

Transformer with same size symbol meaning

Many people draw the transformer step up and step down to show the relative size of the coils. The size (on the schematic) doesn't necessarily indicate step up or step down, but the coil ratio does, ...
Voltage Spike's user avatar
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3 votes
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How do I design a USB interface to program a custom microcontroller?

You are not missing anything. That MCU has a built-in USB interface. And that microcontroller already has a factory bootloader which allows to program it via USB. All you need to do is to make it boot ...
Justme's user avatar
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1 vote

Why is there a line in, line out and neutral in on a PCB, but no neutral out?

This is a common design. The neutral is there to supply power to the internal circuitry on the board and has nothing directly to do with the output. There is no need to add a neutral wire since it ...
Spehro Pefhany's user avatar
0 votes

Why is there a line in, line out and neutral in on a PCB, but no neutral out?

The point is both the lamp and PCB need both Live and Neutral for power in order to work - i.e. the lamp to light up, and the sensor board to detect movement. Compare the sensor board with a standard ...
Justme's user avatar
  • 154k
2 votes

Why is there a line in, line out and neutral in on a PCB, but no neutral out?

Neutral is common between the input and output side. In other words, there are no components that need to be in series with the neutral line between input and output. Therefore, it is more reliable to ...
Dave Tweed's user avatar
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0 votes
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Automate home blinds with motor, potentiometer and 3P switch

You would require a DPDT switch, two limit switches and two diodes to carry out the following functions: Initiate 'up' / 'down' movement Stop the motor at 'end of travel' in either direction Permit ...
vu2nan's user avatar
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0 votes

Why does power supply have a negative rail if can only output positive voltage?

As explained, the positive, negative, and Ground are electrically isolated. You can bond or reference either polarity to Ground. The ground terminal is the equipment chassis and AC Equipment ground ...
Dereck's user avatar
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1 vote

Why does power supply have a negative rail if can only output positive voltage?

You may not want to tie your negative terminal to chassis ground when there is the possibility of picking up white noise off that ground. Floating the circuit and tying it to a different ground is ...
Fred Sopron's user avatar
0 votes

Automate home blinds with motor, potentiometer and 3P switch

The circuit would not work as drawn. The 3p switch (you actually need a DPDT switch) must be connected across both ends of the motor to control direction. The potentiometer speed control is extremely ...
vir's user avatar
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1 vote
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Zero-Current-Switching Circuits

This isn't really a well-formed question, but I think answering with the background information will address it well regardless. For EMI, the rate of change matters. So, switch turn-on and -off are ...
Tim Williams's user avatar
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3 votes

Will this short circuit to turn off an LED drain the battery?

You don't need a microswitch or any other additional devices. Just a bit of metal. Just have a bit of metal on the lid, a bit of leaf-springy-material on the base, and a little bit of paper separating ...
Steve's user avatar
  • 249
0 votes

DPDT Switch Microcontroller

For currents and voltages at microcontroller scales (5V, 10mA), something like the 74HC4052 could be wired up as a DPDT switch. It has two identical circuits (double pole) that have a common and each ...
user85471's user avatar
  • 316
7 votes

Why does power supply have a negative rail if can only output positive voltage?

If the output can't be negative,... Whether a voltage is positive or negative depends on how it is measured. The negative (black) terminal is the reference against which the positive (red) terminal ...
RussellH's user avatar
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2 votes
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Is it possible to use a 2 flip-flop synchronizer for reset?

The purpose of this structure unlike a simple 2FF synchroniser is that you get true asynchronous assert whilst maintaining the metastability protection on deassert. There will be a non-deterministic ...
Tom Carpenter's user avatar
22 votes

Will this short circuit to turn off an LED drain the battery?

Figure 1. Image source: RS Reed switches guide. A reed switch is the most compact non-electronic solution to your design problem. They are available in NO (normally open) and NC (normally closed) ...
Transistor's user avatar
  • 177k
4 votes

Will this short circuit to turn off an LED drain the battery?

Short circuiting a battery to use it as a switch is a bad idea. 1, the battery will get drained almost instantly, so unless you want to buy millions of batteries, you shouldn't do that. 2, it will ...
Andy K's user avatar
  • 337
0 votes

Is it possible to use a 2 flip-flop synchronizer for reset?

It will be delayed for at least one clock cycle, because you don't know the relationship between the rising (deactivating) edge of the reset and the rising edge of the clock -- worst case the reset is ...
Simon Richter's user avatar
2 votes

Why does power supply have a negative rail if can only output positive voltage?

The green socket is in fact chassis earth and connects to the protective earth (PE) that comes into the power supply from the wall socket. That green socket is usually galvanically isolated from the ...
Andy aka's user avatar
  • 462k
13 votes

Why does power supply have a negative rail if can only output positive voltage?

The power supply itself has two output terminals, labelled \$\boldsymbol{+}\$ and \$\boldsymbol{-}\$, and produces up to 60 V between them. Remember that voltage is defined only as a difference ...
Hearth's user avatar
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21 votes
Accepted

Will this short circuit to turn off an LED drain the battery?

With the lid closed, the battery will be dead within minutes. Consider using a microswitch such as this one, found on ebay Position the lever to be depressed when the lid is closed. When the lid ...
Simon Fitch's user avatar
  • 37.6k
13 votes

Will this short circuit to turn off an LED drain the battery?

Yes, the circuit you've shown will pretty much immediately drain the battery; some batteries have enough energy in them they'll get very hot or worse when you short them out. I can see you'll need to ...
jonathanjo's user avatar
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3 votes
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Feedback and Gand-Bandwidth Question

I notice that with a larger feedback factor, the unity-gain frequency tends to be lower and to not follow the original open-loop unity-gain frequency. This can be seen from the green curve. I'm ...
Andy aka's user avatar
  • 462k
2 votes

Pulse generation from a constant current source

The circuit below is worth exploring. R1 is the load. V3 is the signal generator of the current waveform you want. Scale of current per volt of input is set by R2, in this case 1V == 0.1Amps. ...
Fabio Barone's user avatar
  • 4,759
2 votes
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Impedance of a passive RC

The input impedance is \$\sqrt{R^2 + X_C^2}\$ and not \$R+X_C\$. Pythagoras is king when it comes to adding resistive and reactive impedances. The correct formula gives you the right answer of 306....
Andy aka's user avatar
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0 votes

3 buttons and 3 LEDs circuit with mutual exclusion

As above, this is called a "game show" or "College Bowl" circuit. If you search for 'game show circuit' or game show circuit schematic', you will get many examples of how to do ...
AnalogKid's user avatar
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1 vote

3 buttons and 3 LEDs circuit with mutual exclusion

Here's one of many ways. It's modular, so you add as many students as needed. Personally, I would probably do this with a microcontroller dev board or Arduino. But here's a hardware only version if ...
MOSFET's user avatar
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0 votes

3 buttons and 3 LEDs circuit with mutual exclusion

This is the classic "game show" or "Jeopardy" circuit. The first button pressed is registered and locks out any subsequent presses of all other buttons, until a master reset ...
Fabio Barone's user avatar
  • 4,759
1 vote

How to apply a thermistor to my LED driver (TLC59116 PW package)

Assuming you wish to augment the internal overtemperature protection in U18, and since you are using an I2C peripheral, it would perhaps be more expedient to employ an I2C digital output temperature ...
Spehro Pefhany's user avatar
0 votes

Building a DIY BGA Rework Machine

Schematic is a mess since hot seems to be connected to neutral. That aside: If you want to use less power you should use heaters that use less power, or use less heaters. Do you really need 20 amps of ...
Quitting Due To Antisemitism's user avatar
1 vote
Accepted

TLP292 Schematic Review

No, your circuit is not fine. The TLP292 has a current transfer ratio of 50 % at 0.5 mA LED current, meaning that it will not be saturated and you can only expect 0.5((5-1.4)/10k)=0.18 mA on the ...
winny's user avatar
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2 votes
Accepted

Understanding the behavior of an emitter follower power supply

Almost no current (why?!) The voltmeter acts like a high valued resistor. You should place the voltmeter in parallel with the load, not in series with it. The same advice applies to the voltmeter you ...
Math Keeps Me Busy's user avatar
0 votes

Irregular behaviour of this RC circuit

The problem has been solved . The reason behind of it was because of pcb's itself. I dont know why this happened but when i resoldered this circuit to cheap self holed pcb with bunch of wires, now it ...
qwertyqwq's user avatar
0 votes

Why is there back current from DRV8833 when using PWM in slow decay (braking)?

If you are using the motor in bidirectional mode, then there are two decay modes. From the datasheet: As you can see in the diagram, if you turn all the switches off, it goes into fast decay mode. In ...
Saadat's user avatar
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2 votes

Irregular behaviour of this RC circuit

R3 and the LED may provide an excessive load to the IC. It's rated for 4mA @ a 3V Vcc. An overload can cause the output voltage to go below the minimum needed for a logic-high at the input. If that's ...
Carl Rutschow's user avatar
1 vote

How can we set the exact current through feedback resistor Rf1 to achieve 0V output at DC?

Your simulation has incorrect power applied: the diff pair inputs are referenced to GND, but your V- connection is also GND. The amplifier simply cannot operate ...
Tim Williams's user avatar
  • 37.4k
1 vote

How can we set the exact current through feedback resistor Rf1 to achieve 0V output at DC?

Ideally (infinite gain), the current of Rf1 should be equal to the base current of the input TR2 transistor. It follows that if we want 0 V at the output, then with the same input transistors, the ...
csabahu's user avatar
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0 votes

How can we set the exact current through feedback resistor Rf1 to achieve 0V output at DC?

$$\color{red}{\boxed{\text{Answer given before OP changed question with a faulty circuit}}}$$ how can we set the exact current flowing through the feedback resistor Rf1 to set the output at 0V at DC? ...
Andy aka's user avatar
  • 462k
1 vote

Output voltage didn't change after adding capacitors and resistors

The (rather elderly) LD1117 is designed to work with an electrolytic 10uF (tantalum or aluminum type) capacitor on the output. It requires that part in order to be stable (in this context, that means ...
Spehro Pefhany's user avatar
1 vote
Accepted

Output voltage didn't change after adding capacitors and resistors

Not a big change, I think. Is this expected? Yes, that is expected. Until a load is connected, your voltmeter will not show much difference between the two circuits. The difference will be in the ...
Fabio Barone's user avatar
  • 4,759
6 votes
Accepted

THD of two passive circuits

Unless you used a special nonlinear model, simulated resistors and caps are perfectly linear and introduce zero distortion. There is no noise either, unless you enable it. Thus the THD measurement on ...
bobflux's user avatar
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