9vac 1000mA -> 12vdc 500mA adapter

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9vac 1000mA -> 12vdc 500mA adapter

Postby tonymcbony » 21 Apr 2010, 11:12

Hey folks,

I'm just trying to figure out what I need and in what order to make an adapter box that takes my pedal power's 9Vac 1000mA output and converts it to 12vdc 500mA. I'm trying to power a particular delay that keeps giving me trouble.

I assume at the basic level I need a rectifier and a smoothing cap.
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Re: 9vac 1000mA -> 12vdc 500mA adapter

Postby lolbou » 21 Apr 2010, 12:49

See some explanations here...

This might get you on the way, let us know! :wink:

(moved to Stompbox Builder's FAQs & How To's)
- Are you a mod or a rocker?
- Uh, no, I'm a mocker.
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Re: 9vac 1000mA -> 12vdc 500mA adapter

Postby tonymcbony » 21 Apr 2010, 15:15

I'm also silly enough not to mention the fact that it's a pedal power/ power plant box that I want to take the 9vAC power from on part, stick it into a box that will spit out 12vDC

Thanks for that link, I'm trawling through it
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Re: 9vac 1000mA -> 12vdc 500mA adapter

Postby mictester » 22 Apr 2010, 01:19

tonymcbony wrote:Hey folks,

I'm just trying to figure out what I need and in what order to make an adapter box that takes my pedal power's 9Vac 1000mA output and converts it to 12vdc 500mA. I'm trying to power a particular delay that keeps giving me trouble.

I assume at the basic level I need a rectifier and a smoothing cap.


Basically, you're right. 9V AC rectified and smoothed will give you (roughly) 1.4 X the AC Voltage, so you'll have about 12.8 Volts DC. This will be unregulated, and you really don't have enough voltage "headroom" for a regulator. If you want to get really close to 12V, use a 1N4001 diode in series with the supply - it'll drop (roughly) 0.65V, so you'll be very close. If your 12V DC circuit only needs a supply rated at 500 mA, your 9V 1A supply will be "man enough" for the job, and you should see a reasonably reliable 12V even under load.

A good "rule of thumb" is 1000µF per Amp, so your supply should be OK with a 470µF smoothing cap. However, I'd err on the side of caution, and go for 1000µF - you're then sure that the hum you're hearing isn't coming from the supply rail!
"Why is it humming?" "Because it doesn't know the words!"
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Re: 9vac 1000mA -> 12vdc 500mA adapter

Postby tonymcbony » 22 Apr 2010, 03:15

That answer is freaking amazing.

Any suggestions on which particular diodes I should be using in the recitifer?
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Re: 9vac 1000mA -> 12vdc 500mA adapter

Postby mictester » 22 Apr 2010, 06:28

tonymcbony wrote:That answer is freaking amazing.

Any suggestions on which particular diodes I should be using in the recitifer?


You could use four 1N4001 - they're rated at 1 Amp, so will loaf along at half that. Remember too that the 1N400X series are all the same except that the last digit relates to the maximum reverse voltage - 1N4001 = 100V so there's lots of headroom! If you can't get 1N4001, use 1N4002 or 4003 or 4004... For example: I have a lot of 1N4003, so use them for almost everything!
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Re: 9vac 1000mA -> 12vdc 500mA adapter

Postby tonymcbony » 23 Apr 2010, 04:07

Sweet, all working and wonderous, thanks for the help!
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