### Author Topic: constant of 12 volt  (Read 1164 times)

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#### louis

• Beginner
• Posts: 3
##### constant of 12 volt
« on: January 10, 2009, 10:34:46 PM »
hello
i got  power supply (input 120v ac 60 hz 12w and output is 12v dc 500 mA)  but when i measure it with multimeter it said 17 volts. how can i reduce to constant of 12 volt?

thank you for your help

#### frodo

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##### Re: constant of 12 volt
« Reply #1 on: January 10, 2009, 11:51:19 PM »
look on websites like rapid electronics, maplins etc etc and look for a 12V voltage regulator.
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#### want2learn

• Robot Overlord
• Posts: 189
##### Re: constant of 12 volt
« Reply #2 on: January 11, 2009, 12:20:32 AM »
I take it this is a wall adapter, Their voltage tends to drop quite a bit as you load them up.

Just do as Soerren says in you other post.
How much amps or  Milliamps does your relay pull when energised???

All of the other components in your circuit will work fine from about 3.5V to 18V, it's only the relay that needs a closer tolerance on your voltage

I haven't looked at your circuit since yesterday and I got a head like a sieve but you may find that a diode or two will be enough to drop the voltage to a level your relay will be happier with. You may not need them at all.
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#### pomprocker

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##### Re: constant of 12 volt
« Reply #3 on: January 11, 2009, 01:56:41 AM »
sounds like an unregulated wall wart. what you need it a regulated wall wart.

If you want to regulate it there is a voltage regulator with a 5% accuracy.