Over voltage protection.

Hi all
I have built myself a voltage regulator that I can adjust to the desired output voltage from any input voltage from 8-32v DC. I was thinking of using my 18v drill lithium batteries which are 5.0ahr for the supply voltage but my only concern is that if the voltage regulator pooped itself could it supply the full 18v supply voltage and cooked my detector. If so is there any electronic components I can add to the regulator that would prevent this excessive voltage being accidently supplied to the detector. Hope someone can help.
Thanks in advance
Firey10_0

Electronics goes over my head, but a quick search and the appears to be plenty of info, here is a start. http://www.learningaboutelectronics.com/Articles/Overvoltage-protection-circuit.php

Firey10_0 said:

Hi all
I have built myself a voltage regulator that I can adjust to the desired output voltage from any input voltage from 8-32v DC. I was thinking of using my 18v drill lithium batteries which are 5.0ahr for the supply voltage but my only concern is that if the voltage regulator pooped itself could it supply the full 18v supply voltage and cooked my detector. If so is there any electronic components I can add to the regulator that would prevent this excessive voltage being accidently supplied to the detector. Hope someone can help.
Thanks in advance
Firey10_0

Click to expand...

I'd expect, but cant be certain, that Minelab would have a overvoltage protection cct on the P/S I/P line. Perhaps AuMan (Mick) will pop in and provide the answer.
If there is no protection, then a crowbar circuit should provide sufficient and fast protection.
A fair description of the design and operation is provided here https://circuitdigest.com/electronic-circuits/crowbar-circuit-diagram

What he said...

" If there is no protection, then a crowbar circuit should provide sufficient and fast protection.
A fair description of the design and operation is provided here https://circuitdigest.com/electronic-ci it-diagram "

Great, thanks for the info guys. I might double check with Auman and see what he thinks also.
Thanks again

How many volts exactly are you chasing?

I am currently regulating about 11v down to 8v but I want to use a different battery which is 18v. That was my concern only if the regulator failed and allowed the full 18v through to the detector.

I may be in over my head here. but couldnt you just use a voltage sensitive relay? Im not sure if they are made in a way to fail open if an over-voltage is detected But I know they make them work the opposite way?

VSR is a bit chunky to be adding to the battery, plus they are designed to switch off when the voltage drops.
Would be easy to get someone to add an 8.2 or 9.1V Zener Diode protection circuit on the output.

+1 Dead driver
You want a zener diode over voltage protection, is the way to go and its very simple.
You can also add over voltage protection by
I would place a 9.1V zener diode parallel with a fuse on your power input, when the voltage hits 9.1v the diode will conduct shorting out the circuit and blowing your fuse.
I would suggest this 9.1V 5W zener diode from Element 14 for sub $1, you can also try RS components, WES or Jaycar etc..
element14.com/on-semiconductor/1n5346brlg/zener-diode-9-1v-5w-axial-leaded/dp/2844766?st=zener%20diode%209.1v
you can also add a reversed normal power diode rated for 2-5 amps incase you reverse the polarity.

here is site with about and how to.
learningaboutelectronics.com/Articles/Overvoltage-protection-circuit.php