When Wrong battery leads are connected

[Ajay0707]

Hi Gurus,

I am sorry I am asking too many questions.... may be because I just began electronics..

When I connect the wrong battery leads to Gary's detector unit it burns the C1 and IC's 7660 and 1117a. I just was wondering if we could build a circuit which will disconnect the power supply if wrong battery leads are connected to the circuit board.

Sorry I dont know much of the terminology as I am a beginner.

Please help me with the Schematic and PCB if its possible. Your kind help is greatly appreciated.

Thank You
Ajay

[homefire]

All you have to do is place a Diode on one of the leads to protect the circuit.

[Ajay0707]

Hi Homefire,

Thank you for the quick reply. Could you please suggest a suitable diode for this application.

Thanks In Advance
Ajay

[homefire]

Just about any Rectifier diode of suitable voltage and current would work.

6A, 50V Rectifier should be more then enough.

[Ajay0707]

Hi Homefire

Hi Homefire,

Thank you for the suggestion. I will find a diode with the same values that you have suggested.

-Ajay

[M.T]

Hi Homefire,

Thank you for the suggestion. I will find a diode with the same values that you have suggested.

-Ajay

HI

Ajay0707 CAN U GIVE THE NAME of diode

are u make any changes in ur pi

regards

[Ajay0707]

Hi MT,

I have used 1N4007 which was a readily available rectifier diode with me. It solved the purpose.

-Ajay

[oldfox]

Wrong battery polarity connect

Hi folks.
The CURE to connecting a battery backwards is a bridge rectifier. (4 pin device or 4 diodes)
Connect the battery to the AC inputs, disregarding polarity. The + and - outputs go to the original battery inputs.

If you doubt this, draw it out and try both directions of the battery. If connected properly in the circuit, + out will be + voltage. It's all black magic.

Sorry about this post being so late buy I just saw it.

Good luck,
Old Fox

[satdaveuk]

Hi MT,

I have used 1N4007 which was a readily available rectifier diode with me. It solved the purpose.

-Ajay

Hi Ajay
That diode isnt beefy enough its only rated at about 500ma so very liable to go short circuit and you wouldnt know until its use is needed.
Also putting that one in series your loosing about a volt, so instead of 12v your running on 11v Your better off with a shoskey diode IN5817 20V/5A there cheap as chips and more than enough for what you want and less volts drop.
Another way we used to do it with taxi radios where they were taken them in and out of diffirent cabs was to put a shoskey diode across the +/- supply and if reverse polarity happened current flows through the diode and would just blow the fuse.
The best way is using a relay and a few components, which draws no current when polarity is connected correctly .
The draw back with using four diodes is your wasting at least twice as much power as the single diode method hence why its rare to be ever used when using batterys, but can be very useful when building projects using a bench power supply.

Regards
Dave

[satdaveuk]

here you go, if connected wrong polarity the LED light up, note there using to shoskey diodes, there fast acting.
When you applie correct polarity D1 becomes reverse biased and the relay stays off, when incorrectly connected D1 becomes forward biased and activates.
Very simple and effective.
The relay for the TGSL etc can be really small but oviously sizes will vary depending on power rateing of project.

Regards

[satdaveuk]

These are other options sugested which are simple but have there downfalls.
I often use the bridge when working off my bench supplys, a blessing when getting tired and open to mistakes

Regards

[satdaveuk]

This circuit uses a p channel mosfet, ive not tryed this one yet but looks dandy, hopefully we get some feedback from others on this one.

Regards