The downside of a voltage regulator

240

02:36:43

The downside of a voltage regulator, is if the part failed for any reason the full voltage will be applied to your device. Creating much damage or fire if the difference is more than a few volts.

I had a go with a few lm317t regulator and a large volt supply, I'm happy to say only one test light bulb was damaged on the device side but 6 out of 6 lm317t went up in flames on my prototype board. It's not too damaged just cosmetic, some plastic melted down and blacked.

I found that a lm7805 makes a more robust variable Power supply. Place a 470 ohm between the output and ground, than a 10 k pot between gnd. On regulator and ground. Very simple and effective.

published 9 years ago

tpfohl

9 years ago

Interesting. You cant go below 5...V though because VO = 5V*(1+10kOhm/470Ohm)+Id*10kOhm

thebugger

9 years ago

Things went wrong because this is not a voltage regulator. A voltage regulator requires 2 things. First a reference voltage and a negative feedback to control the output voltage no matter what. You have no negative feedback whatsoever, just incredibly high gain op amp. Furthermore in order to keep the op amp unloaded for obvious reasons, you have to put an external transistor to handle the power dissipation. I'll try to demonstrate what i mean

thebugger

9 years ago

Search for Voltage Regulator Simplified

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