How Can I make my own regulated and filtered 9VDC Power Supply?

Format _C:

Format _C:

2[H]4U
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Jun 12, 2001
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I was given a large digital LED wall clock and the place that gave it to me was getting new branded clocks with their logo. to put it short they cut off the AC adapter and lost it so I don't know the volt/Amp requirements (I think it's 9VDC at around 300-400MA) I used an adapter with a voltage selector to find this out at anything less then 9V it will not light up any more any the LEDS start to get hot. I want a filtered supply to totally isolate from the 120VAC line (If possible) because with the adapter I'm using now I get a 60HZ flicker on the clock which is annoying, Is there even a 9V positive regulator out there is is there another way?
 
Digikey has 9V positive voltage regulators, something like this: 9V regulator Feed it with a 12v wall transformer and it should work. Otherwise you can use a LM317 adjustable regulator and set it to 9V.
 
I'd go with the LM317 as well, except you'll need a DC input voltage. If you can source a crappy wallwart at 12V or so, i'd use the LM317 to regulate it down to 9V and call it a day. You can find LM317 calculators online that will tell you the resistor values to use.
 
Would a 14Volt transformer work @ 600MA? (That's all I have extra in my parts bin I have a 12V one but it's only 100MA)
 
Any cheap wallwart AC --> DC will work up to ~42 V IIRC. (It's at least 40, so no worries there)
 
Format _C: said:
I was given a large digital LED wall clock and the place that gave it to me was getting new branded clocks with their logo. to put it short they cut off the AC adapter and lost it so I don't know the volt/Amp requirements (I think it's 9VDC at around 300-400MA) I used an adapter with a voltage selector to find this out at anything less then 9V it will not light up any more any the LEDS start to get hot. I want a filtered supply to totally isolate from the 120VAC line (If possible) because with the adapter I'm using now I get a 60HZ flicker on the clock which is annoying, Is there even a 9V positive regulator out there is is there another way?
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If the LEDs get hot at 9V, and don't work at less voltage than that, then chances are the clock is designed to run off 9V.

Run it for a while at 9V and see if it still works - maybe "hot LEDs" are how the clock is designed to work. LEDs (especially in signage applications) can get hot. hell, Luxeons, used in flashlights and industrial lighting, have heatsinks!
 
Well a friend gave me an old Dell (Pentium 100MHZ) and as I was pulling out the cards I noticed the ISA (Yes I said ISA):D sound card had a L7809CV Voltage regulator. on it I looked at the datasheet and it says it can provide up to 1.5A of current with the proper heatsink and yes gee the clock runs fine on 9VDC any more and I'm afraid I will ruin the clock and I can't get any more of them The LEDS do not get hot at 9VDC but they do at 12VDC (I'm testing this using a multi voltage Wall wort it has 1.5 - 3 - 4.5 - 7.5 - 9 - 12 Volts on the selector and the clock originally had a permanently attached AC Adapter but since the place where I got it from cut it off I just soldered on DC jack so I can move it easier

here's a picture of the clock I took a couple of days ago that I forgot to post

clock.jpg
 
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