Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: Trumpkin on October 22, 2008, 08:27:27 AM
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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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Whats the application?
Whats being protected from what?
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Whats the application?
Microcontroller.
Whats being protected from what?
An Atmega32 and L293d from me sticking the battery in the wrong way.
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just use a Schottky diode
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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.
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it would also drop the voltage and dissipate that energy as heat
Schottky diodes have a low voltage drop
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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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.
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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
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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...