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Author Topic: Reverse battery protection  (Read 3697 times)

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Offline TrumpkinTopic starter

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Reverse battery protection
« on: October 22, 2008, 08:27:27 AM »
I would like to use a mosfet on my next project for reverse voltage protection. What mosfet would be the best?
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Offline Admin

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Re: Reverse battery protection
« Reply #1 on: October 23, 2008, 10:54:37 PM »
Whats the application?

Whats being protected from what?

Offline TrumpkinTopic starter

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Re: Reverse battery protection
« Reply #2 on: October 24, 2008, 07:08:09 AM »
Quote
Whats the application?
Microcontroller.
Quote
Whats being protected from what?
An Atmega32 and L293d from me sticking the battery in the wrong way.
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Offline airman00

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Re: Reverse battery protection
« Reply #3 on: October 24, 2008, 07:17:38 AM »
just use a Schottky diode
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Offline ArcMan

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Re: Reverse battery protection
« Reply #4 on: October 24, 2008, 09:00:39 AM »
Although a diode would certainly do the job, it would also drop the voltage and dissipate that energy as heat - undesirable for a motor circuit.

Offline airman00

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Re: Reverse battery protection
« Reply #5 on: October 24, 2008, 09:49:59 AM »
it would also drop the voltage and dissipate that energy as heat

Schottky diodes have a low voltage drop
Quote from: Wikipedia
The Schottky diode (named after German physicist Walter H. Schottky; also known as hot carrier diode) is a semiconductor diode with a low forward voltage drop and a very fast switching action.
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Offline ArcMan

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Re: Reverse battery protection
« Reply #6 on: October 24, 2008, 10:26:27 AM »
Low is relative.  A typical Schottky diode has a 0.3V drop.  My point was that that 0.3V drop does occur and it wastes energy.  This energy waste is probably no big deal for an electronics feed or a small servo, but it can add up for a motor circuit feed.  A MOSFET has a much lower voltage drop than a diode.


Offline Admin

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Re: Reverse battery protection
« Reply #7 on: October 24, 2008, 10:02:49 PM »
Electrical protection: use a voltage regulator with polarity protection

Mechanical protection: set the pins up so that if the bat is plugged in backwards, nothing will happen

Labeling: mark clearly what wire goes where, use colored wiring too

Offline gamefreak

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Re: Reverse battery protection
« Reply #8 on: October 25, 2008, 05:53:40 PM »
Labels only help when applied correctly, my team labels things backwards all the time and I seem to recall an arm project of Admins that did the same...
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