# Questions tagged [power-dissipation]

Anything related to power dissipation in electrical and electronic circuits and components, i.e. the process in which electrical energy is converted to heat when current flows through them.

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### How are LEDs considered efficient?

I've always found circuits containing LEDs hard to understand, please bear with me. I know most people find it easy, but I'm confused by them so some of my assumptions might not be correct, please ...
107k views

### Is it possible to calculate how much heat dissipation and temperature rise will take place in a resistor

Suppose I have a 100 mAh battery at 20V. I connect a 1000 kohm resistor across it. How much heat will be generated and how can I find the temperature rise in the resistor? As the battery operates I ...
1k views

### TO-92 not getting hot enough

I am controlling a DC fan by an AVR MCU and I am curious about the thermal characteristics of a 2N3904 NPN transistor over which the fan is connected. Reading the transistor's datasheet, I find the ...
2k views

### 125 mW resistor subjected to 600 mW dissipation in professional safety system

The schematic below is the input circuit of a signalling PCB, which we buy from one of our suppliers of fire detection systems. Said PCB has to be built into a so called geographic evacuation panel ...
1k views

### How does static dissipative foam work?

I am planning to build a grip-release sensor using the foam. I'm pretty interested in the way it works. Does the resistance in circuit increase or decrease when force is applied onto it? And this will ...
5k views

### LED strips: 46% resistive losses?

I recently bought these LED strips. They are supposed to run on 12V/72W and have 300 x the SMD 5050 LEDs on it. Schematic: simulate this circuit – Schematic created using CircuitLab The ...
4k views

### How closely should I space my thermal vias?

How closely do you pack your thermal vias? I know that more vias divides the amount of heat each via can move and that smaller vias allows more vias to be packed together. Knowing this, it seems ...
12k views

### How to choose correct resistor with proper wattage and ohms for 6 leds connected in a serial circuit?

Let's suppose I've six LED lights with each 3.2 Volt and 20mA and all six of them are connected in one serial circuit. I know there is better setup but for this I'm using this circuit setup. I'm ...
10k views

### Is there any pattern or standard to through-hole resistor sizes?

I've long been under the impression that a quarter-watt resistor has a standard package, and a half-watt resistor has a standard package, etc. But I've recently gotten through-hole resistors which are ...
4k views

### What is making my DC/DC converter's capacitor to blow up?

I'm having some capacitors blown up and I am not sure what's the cause of this. It is definitely NOT OVERVOLTAGE and NOT in WRONG POLARIZATION. Let me introduce the scenario: I have designed a double ...
3k views

### BJT power dissipation - Which value to use? (Ta vs Tc)

I'm using a TIP120 (Darlington pair BJT) brought to saturation for a project of mine. I have $V_{CE(sat)}=1V$, $I_C=2A$, $V_{BE}=2.5V$ and $I_B=0.005$A, which give me a total power dissipation ...
3k views

### PCB layout for high side switch (high current)

I'm working on a PCB layout for two high side switches. You can see below a picture of my current layout. The copper weight of the future PCB will probably be 2 oz/ft² (double sided). I use two p-...
20k views

### Wattage calculation for resistors in series

I need the formula for calculating resistor wattage when the resistors are in series. For example, say I have 3 1/4 watt 10 ohm resistors in series. What is the potential power dissipation for the ...
3k views

### Heatsink on underside of PCB

I have prototyped some DC-DC converter modules, and they work well. However due to size, I don't have a huge amount of copper pour for them to dissipate their heat. I have used 2oz copper but the ...
3k views

### LM317 - Calculate dissipation due to voltage drop

If I use a linear voltage regulator as LM317: Input voltage = 24 V Output voltage = 5 V (so a voltage drop of 19 V) Mean load = 480 mA (peak load = 700 mA) From the datasheet, I read that maximum ...
545 views

### At the microscopic level, what exactly forces us into the “dark silicon” (i.e., the mismatch between transistor scaling and voltage scaling) problem?

I've read that if you fix the TDP of a chip, you cannot use all of the transistors simultaneously any longer. This leads me to believe that each transistor requires the same power as in previous nodes ...