Polarity Protection?

kelvin james

I have read various articles on this, from using reed relay/diode combos, thermistors and other circuit designs. Also, with my setup, i am using a dual power supply, 5v logic and 12v to motor. I have fried one motor control board already by accidently wiring the board wrong, and would like to make sure it doesn't happen again. So, i am really looking for a dual purpose protection, one for polarity protection of the electronics, and secondly over-voltage protection from bonehead mistakes from myself. Just wondering if anyone has an easy solution to this, even in the form of a complete component.

Thanks Kelvin

KenM

Here are a couple of different schemes to protect from reverse polarity.

The circuit that uses a relay will turn on an LED if you connect the positive and negative wires with reverse polarity.

ken

kelvin james

Thankyou Ken for the time to post the circuits. The one that lights the led is perfect, exactly what i was looking for. As far as my other problem with the dual voltage, i figure i will have to add a regulator to protect the 5v section of the board from the 12v. Kelvin

LoopyByteloose

Actually, the newer low drop out voltage regulators have polarity protection built into them.

The reason I mention this is because you need the voltage regulation and because all diodes waste 0.6 to 0.7volts.
If you use the discrete diodes for polarity protection, you have to supply a higher voltage and this power is just disapated in heat.

If you use a low drop out voltage regulator, you can consume that power in the microcontroller.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
G. Herzog in Taiwan