Whats your suggestion for reverse polarity protection?

* Relay that only closes when connected properly to provide power to the rest of the circuit?

* Diode across Hot & Ground threw a fuse that blows when connected in reverse?

* Zener?

Other suggestions.

 

What's the voltage of the circuit in question?

If it's 9v-18v, you could use an N-ch or P-ch power MOSFET with the source to one input, and the gate to the other input. Reverse polarity would cause the MOSFET to be turned off. Correct polarity would result in the MOSFET being ON, with a very low resistance connection.

If it's logic level voltage, you could use a logic-level N-ch MOSFET. They don't make logic level P-ch MOSFETS as far as I know.

You could use a relay, but that would mean a constant power drain via the coil.
You could use a diode, but even Shottky diodes have a voltage drop across them, therefore they dissipate power.

 

Use a polarized connector so the applied voltage can't be in the wrong polarity.

 

I'm fond of the bridge rectifier.

 

What's the voltage of the circuit in question?
....
If it's 9v-18v, you could use an N-ch or P-ch power MOSFET with the source to one input, and the gate to the other input.

The applied voltage is 12 volts amp draw will be about 1 amp, Do you have a simple diagram of the MOSFET?

In this case, a tiny draw from the relay wouldn't be an issue, but I would rather not use the relay method due to space constraints.

Use a polarized connector so the applied voltage can't be in the wrong polarity.

Ok, now how to eliminate the person making the connection from connecting the wrong wire to the right side of the polarized connector?

I'm fond of the bridge rectifier.

Thought about that, but never tried it or seen it done.

Thanks everyone for the replies.

 

You can put a PFET in the plus side and an NFET in the minus side in a criss-cross pattern.

If you are using VERY LARGE CURRENTS, then consider using a diode crowbar, putting a fuse inseries with the + connection, and putting a high current diode after the fuse with its cathode connecting to the rest of your circuit and the fuse, and the anode connected to the - connection.

I would use the diode crow bar with any lead-acid battery high powered equipment because using reverse protection MOSFET circuits or Diodes would wind up getting very hot with a 10Amp+ current draw.

0.7Vdrop * 10Amps = 7Watts for a single diode inseries with the + connection.

10Amps^2 * 0.05ohms Rdson = 5Watts for a MOSFET used in a blocking circuit.

 

Bridge Rectifier X2

as long as the volt or so difference isn't important. It's nice because no matter what way you put the battery in, it still works!