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Old 07-25-2012, 04:08 PM   #31
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Running DC device off AC


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Originally Posted by bcgfdc3
jump start pack used for a car
Ah yes, but what we forget is that I'm looking for something cheap and no more than about 4 inches square.

I did pick up a 200V 10A bridge rectifier. Output voltage is 11.6V DC, however, under load it reduces to 8.3V. I don't know the amperage rating of the AC transformer but it's pretty beefy. However, I'm guessing it's not powerful enough.

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Old 07-25-2012, 04:48 PM   #32
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Running DC device off AC


You can sometimes pick up inexpensive parts at places like allelectronics and goldmine-electronics.
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Old 07-25-2012, 05:51 PM   #33
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Running DC device off AC


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Ah yes, but what we forget is that I'm looking for something cheap and no more than about 4 inches square.

I did pick up a 200V 10A bridge rectifier. Output voltage is 11.6V DC, however, under load it reduces to 8.3V. I don't know the amperage rating of the AC transformer but it's pretty beefy. However, I'm guessing it's not powerful enough.
Sounds like your tranny is not powerful enough !
go for bigger !

You will need something in the 5 to 10 amp range .

Last edited by dmxtothemax; 07-25-2012 at 05:55 PM.
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Old 07-25-2012, 06:36 PM   #34
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Running DC device off AC


OK here's a possibly dumb question....

Can two 5A 12V AC transformers be connected in parallel for 10A?

This is the type of transformer I have


I have plenty of these laying around, some 6V, some 12V, some 24V.
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Old 07-25-2012, 06:45 PM   #35
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Running DC device off AC


Some transformers can be connected in parallel by some people. You can not, however, connect anything that looks like that in parallel without very likely making smoke.
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Old 07-26-2012, 04:21 AM   #36
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Running DC device off AC


You can !
But it is not considered good practice !
You must feed them both thru a large resistor
first before you parrallel them.
Use a 10watt .22 ohm resistor for both.
Do not try to connect them together with out these resistors.
The trannys must be the same in voltage and current for it to work.
A fuse before the resistor would be wise !
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Old 07-26-2012, 07:57 AM   #37
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Running DC device off AC


Doesn't sound like that would work because these transformers vary in output voltage + or - about 1.5 volts.

I also thought about a 24V transformer using a household dimmer to dial down the input voltage until the output matches 12V, but that also sounds iffy to me.

This is more of an experiment than anything else, just to see if I can accomplish it with what I have laying around.
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Old 07-26-2012, 09:55 AM   #38
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Running DC device off AC


Keep in mind the the nominal voltage for automotive power is way above 12V.
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Old 07-26-2012, 10:02 AM   #39
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Running DC device off AC


He has been using some kind of monstrous power pack to run the light. I have to get a hold of that and see what kind of voltage it is putting out.
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Old 07-26-2012, 10:36 AM   #40
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Running DC device off AC


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He has been using some kind of monstrous power pack to run the light. I have to get a hold of that and see what kind of voltage it is putting out.
11 to 14 volts or thereabouts would do ya good.
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Old 07-26-2012, 10:31 PM   #41
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Running DC device off AC


Quote:
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He has been using some kind of monstrous power pack to run the light. I have to get a hold of that and see what kind of voltage it is putting out.
You should try using a large 10a automotive battery charger,
They are normally quite cheap !
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Old 07-26-2012, 10:38 PM   #42
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Running DC device off AC


Just get one of those landscape lighting transformers and put the bridge rectifier on its output.

We use `em all the time for DC lighting projects ...
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Old 07-26-2012, 11:19 PM   #43
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Running DC device off AC


Something like this and just pulling the guts out?

http://www.menards.com/main/outdoor/...614-c-6388.htm

We have an old battery charger somewhere in the clutter at work, I just have to find it to see what the amperage rating is on it. Looked around a little today and didn't see it but we have shelf loads of boxes
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Old 07-26-2012, 11:49 PM   #44
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Running DC device off AC


By a 12Vdc power supply.....here is one for $30

http://www.automationdirect.com/adc/...ies)/PSS24-100
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Old 07-27-2012, 07:57 AM   #45
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Running DC device off AC


That one looks to be 24V but it says "adjustable". Does that mean one set of output terminals is 12V?

Otherwise there is this

http://www.automationdirect.com/adc/...s%29/PSS12-100

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