Reverse polarity for power connection.

• May 15, 2012

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maniac84

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Hi guys, is there any power connector design which we can connect reverse but stil works? I mean like if I put pin 1 as Vcc n pin 2 as ground, then if I put pin 1 as ground n pin 2 as Vcc, it can work also. Is it by using two diodes?

 

• May 15, 2012

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etmabreu

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Use a full bridge rectifier.

 

• May 15, 2012

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keith1200rs

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If you use a bridge rectifier (4 diodes) it will do what you want. However, you do lose voltage (2 diode voltage drops).

Keith

 

• May 15, 2012

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Do you have the circuit for full bridge rectifier?

 

• May 15, 2012

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etmabreu

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ahgan84 said:

Do you have the circuit for full bridge rectifier?

Click to expand...

Google for it. It is straightforward. You can also buy it as a single component in one package.

 

• May 15, 2012

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I googled it already... But seems like it is use to convert ac voltage to dc voltage. Is it for dc to dc?

 

• May 15, 2012

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keith1200rs

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Effectively your DC input is considered to be AC i.e. the connections could be either way round. So, what you have found is what you need to use.

It is not often used that way. Normally people use a single diode to protect against reverse polarity but then it won't work when plugged in the wrong way (but it won't blow up).

Keith.

 

• May 15, 2012

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Can u recommend a part number for the four diode? I wan to use on 24V.

 

• May 15, 2012

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keith1200rs

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What current? For up to 1A I would just use 4 diodes - 1N4001. If you want to reduce the voltage drop you could use Schottky diodes but they are a lot more expensive.

Keith

 

• May 15, 2012

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I am not sure. But i am connecting 24v to lm317. Any recommendation?

 

• May 15, 2012

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etmabreu

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Go for something at least 2A forward current. Say, Vishay 2W005G-E4/51 or equivalent.

 

• May 15, 2012

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Can i use 1N5400? It got 3A forward current.
How do we determine the voltage rating for the diode?

 

• May 15, 2012

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etmabreu

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ahgan84 said:

Can i use 1N5400? It got 3A forward current.
How do we determine the voltage rating for the diode?

Click to expand...

Pretty enough!

Don't bother about voltage rating, any silicon rectifier diode will support (reverse) voltages of at least 50V.

With forward biasing, every silicon diode will give you something around 0.7V voltage drop.