[SOLVED] relay using back-emf

[josh1245]

hello..

I am using a relay which works with 230 v AC supply (its a 230V solenoid).. so with back-emf, what more can i add in order to protect the circuit??
please help me. Its urgent. :idea:

 

[cameo_2007]

Can you please make the second part of your question a bit more clearer?

 

[josh1245]

Im sorry about it. But the problem is that, i am using a PIC16F877A micro-controller, so when i need, I would use a relay to switch to a circuit containing a 230V solenoid, so beause of this, i think a huge back emf will be generated , therefore i would like to know a solution to this..

 

[Tahmid]

Add an antiparallel diode across the relay coil.

Relay driving basics: www.jaycar.com.au/images_uploaded/relaydrv.pdf

 

[internetuser2k12]

Use a diode as mentioned by Tahmid.

A snubber is also a good idea.

 

[ALERTLINKS]

A snubber circuit, resistor capacitor, in series connected in parallel to relay coil terminals.

 

[tpetar]

Switch relay at zero-crossing point. That will reduce EMI-noise, and lifetime of relay coil will increase.

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hello..

I am using a relay which works with 230 v AC supply (its a 230V solenoid).. so with back-emf, what more can i add in order to protect the circuit??
please help me. Its urgent. :idea:

I reading previous posts, I think people forgot this relay have working coil on 220V AC.

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That HV relay should be switched with smaller relay which is connected to uC pin over transistor, and also have flyback diode over coil. I want to say you need some kind of isolation. Also check SCR zero cross detection switching,...

 

[Tahmid]

If the relay coil is driven from 230VAC, you can't use a single anti-parallel diode. That is only for DC. For AC, you need to use an RC snubber. You can also use back-to-back transils/transzorbs/transient suppressors. There are quite a few transzorbs that have two back to back built inside. You may take a look at the P6KE and the P15KE series.

 

[josh1245]

hey everyone! thanks verryyy much... your ideas really gave me some help.. um working on it now...

 

[tpetar]

We hope you'll share your ideas with us. :smile: