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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #1  
Old 05-26-2011, 09:25 PM
jerrymyersmills jerrymyersmills is offline
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Join Date: Mar 2011
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Default 12vac to 12vdc

Dear friends
i have bought a 12VDC relay for project work.The line voltage is 220VAC so i bought a 12V transformer to convert the 22ov into 12V for smooth operation of the relay but i keep hearing this BUZZING sound anytime the relay is working.
Folks i am a bit confused.
I suspect that the transformer is supplying 12 VAC to the relay instead of 12VDC.I want to convert 12vac into 12VDC and need some assistance to be able to achieve this.
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Old 05-26-2011, 09:35 PM
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SgtWookie SgtWookie is offline
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Your DC relay may have a diode across its' coil. That would short out the transformers' output for 1/2 of the cycle.

You can get a small full-wave bridge rectifier from your local Radio Shack store for around $1.39+tax.
http://www.radioshack.com/product/in...ductId=2062581

It has four leads; two are AC (indicated by ~) and the other two leads are DC, marked + and -. You just connect it up. If the relay still buzzes, you may need to add a filter capacitor across the bridge output. This would probably do the trick:
http://www.radioshack.com/product/in...tic+capacitors
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Old 05-27-2011, 04:38 AM
madhusudan.pigeonsembs madhusudan.pigeonsembs is offline
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You can follow this attachment.......
I think you will be very much clear......
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File Type: gif full_wave_rectifier_circuit.gif (11.7 KB, 33 views)
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