Author Topic: Direct DC rather than AC adapter  (Read 927 times)

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THCrinstam

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Direct DC rather than AC adapter
« on: October 17, 2016, 03:15:27 PM »
I have a couple of led lights that came with AC/DC switching adapters (shown in the pic).



Can I simply just cut the plugs off and wire them direct to a 12v battery?



jimbo007

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Re: Direct DC rather than AC adapter
« Reply #1 on: October 17, 2016, 09:49:26 PM »
It's possible although your plugpack maybe a regulated 12 volts while a charged battery will be 13 plus a little volts .
suggest measure the current drawn at 12 volt and again on the battery. be quick as if the current is higher, you may damage the led.
calculate the power in each case, volts times amps.
if they are similar, all is good. if they are different by much, you will need to provide either a current limiting resistor or some kind of regulator.

THCrinstam

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Re: Direct DC rather than AC adapter
« Reply #2 on: October 17, 2016, 10:16:55 PM »
I'll do that and get back to you on it.

I don't know if it matters or not, but the lights are literally just 230 LEDs on a breadboard attached to the power plug for the switching adapter.  5 out of 6 of those adapters stopped working within a couple of weeks. 4 of them just make the LEDs flash and the 5th one only lights up part of the boards. The 6th one works fine on any of them, so I know its not the lights themselves.


OperaHouse

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Re: Direct DC rather than AC adapter
« Reply #3 on: October 18, 2016, 11:54:21 AM »
A couple of diodes wired in series can drop the battery voltage a little more than a volt and that would be the same if you had one string on or multiple strings.  China stuff tends to operate LED at maximum to get a more impressive spec.  Operating at lower current the LED are more efficient.  that only comes intp play if you use a buck converter like those 2696 modules.

jimbo007

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Re: Direct DC rather than AC adapter
« Reply #4 on: October 23, 2016, 12:54:39 AM »
Another option if you were so inclined, would be to open the defective power supplies And replace the mains electrolytic capacitors. Your description of the LED,s flashing would suggestion the primary filter capacitors have dried out or failed which is not suprising considering the relatively high temperature inside these supplies. This is the most common mode of failure in switching supplies. If the mains filter is ok, then check the output capacitor as this is usually providing a reference voltage to the PSU. If it has gone low in capacitance, it will also cause contant shutdown and restarts