Power supply design problem. 120AC in 5Vdc out. problem is making the 5VDC variable using dimmer on AC side.? - 120vac to 5vdc
I am designing a power source using Out 120VAC to 5VDC. You need to control output (5VDC) by a regulatory body of the device. After examining the LM317 can see, but not to vary as the output voltage when the input voltage.
Sunday, January 24, 2010
120vac To 5vdc Power Supply Design Problem. 120AC In 5Vdc Out. Problem Is Making The 5VDC Variable Using Dimmer On AC Side.?
2 comments:
Forget the regulator.
Get a transformer from 120 V to 10 V or 12 in the current demand. Then, using a diode array bridge and a large cap. Fed up to 12 volts DC to a LM317 with a pot that the entrance to the court. Use it to adjust the tension.
http://home.cogeco.ca/ ~ rpaisley4/PSupply ...
For reasons of security, and I can not emphasize this enough, you need a step-down transformer and follow all safety procedures when using 120VAC.
First, use a transformer 120VAC to 12VDC wall wart - and sells them in virtually any electronics store. Make sure it's a bit expensive, heavy, processor type and not a modern light switch unit.
Then the power regulator 120VAC lamp.
Adjust to glow 5VDC unit.
How it works: A cheap transformer wall wart is not regulated and has a step-down transformer in it. Take advantage of the high AC voltage, corrects and filters DC. Since the fixing ratio: primary, secondary, say, 10:1, and 120VAC = 12VAC Out. 17VDC to 12VDC correction is close enough to 12 VDC (under load) for most devices. Now, with a controller "chops" the 120VAC reduce the average voltage of the primary wall wart times. To find 25% dimming, you in the primary 30VAC transformer in a ratio of 10:1, and if the secondary 3VAC rectified and filtered, it shoULD 5VDC approaches.
These are gross figures and a crude method, but is quick and dirty, and works with the AC input voltage to determine.
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