Relay Driver.

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achillis1
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Relay Driver.

Post by achillis1 »

Hello,
I have been unsuccesfully tried to drive a 12volt relay from 5v source and a tranzistor.
I do not know what went wrong.
I studied the circiut diagram of the relay board pdf, in order to "copy" the circuit but it seems that here I cannot find the BCW32 tranzistor!!!
Is there an "easy" compination of relay/resistor/tranzistor type/value that can work?
Also the relay must have a common GROUND with the 5v?
thank you in advance,
Regards,
Achillis.

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Benj
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Re: Relay Driver.

Post by Benj »

Hello Achillis

This is the circuit that I use to switch 12V stepper motor coils with, it should work for your application.

12V supply for relay - Collector of NPN
5V signal from uC - 1Kresistor - Base of NPN
Coil of relay - Emitter of NPN
Other End of Coil - Ground

For the NPN transistor try something like a TIP31 or TIP41 etc.

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achillis1
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Re: Relay Driver.

Post by achillis1 »

Hello Ben,
Thank you for your reply.
It seems that I have lost it during the "translation". Actually I did not quite understood the connections for the relay!
I am attaching a picture as I search on how would be the connections.
For the relay you wrote 3 connections but on the diagram it seems that on a relay are 2 connections as far as it concerns the 5/12 volt circuit.
It seems that I am lucking on circuit knowledge!!!
Thank you.
Best Regards.
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Re: Relay Driver.

Post by Benj »

Hello

Your circuit is nearly correct. But the voltage to drive the relay coil must be 12V for a 12V relay rather then 5V.

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achillis1
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Re: Relay Driver.

Post by achillis1 »

Thank you Ben,
So I shall costruct the same circuit with the only difference I supply 12volts the relay?
One last question: the relay must have the same ground referrence with the 5 volts?
Thank you.

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Re: Relay Driver.

Post by Benj »

Hello Achillis

Yes that should do it and yes you will have to common the 5V ground and the 12V ground. If you are using our EB006 or HP488 boards then you can use the +14V terminal output for the 12V output to the transistor.

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Re: Relay Driver.

Post by achillis1 »

Thank you a lot Ben,
Going to try it!
Best Regards.

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