LED grow light

[darkwhamsic]

I recently got one of those LED grow lights from ebay, like >>http://www.ebay.co.uk/itm/225-LED-Hydroponic-Plant-Grow-Lighting-Panel-Board-Blue-Red-Lamp-Light-UK-240V-/251063703695?pt=UK_HomeGarden_Garden_PlantsSeedsBulbs_JN&hash=item3a7490188f

However, it seems to be being a bit a a pain and not working properly (they have refunded me for the product and i dont have to send it back, so thought i'd have a play and see if i can get it working)

I'll start from the beginning (good place i think)

when i went to turn on the lights, i though they weren't on at all so changed the fuse, however i noticed they were on, but very, very dull. so it wans t the fuse

so i took the back off to have a look inside. There are 2 boards inside, one with all the resisters etc, the other with just the LEDs on, to make sure nothing was causing a problem inside. I re-soldered the positive wire to the LED board cause it looked a little loose amd the same with the smaller board/

Still nothing

But by accident, i noticed that when i touched the back of one of the LEDs it would light up that row... hmm strange

It doesnt smell like anything has burnt inside, and i cant see any burn marks on any boards

All the LEDs are working.. in a fashion..

Just wondered if anyone has any suggestions as to waht it might be or how to get it working again

I'll try and put a pic of the curcuit if needed

[I_Daniel]

When you touch something and it works then you have a very difficult fault to trace, namely a dry joint, sometimes there is also a hairline crack which when you touch or press on a pc-board makes contact.

[darkwhamsic]

When you touch something and it works then you have a very difficult fault to trace, namely a dry joint, sometimes there is also a hairline crack which when you touch or press on a pc-board makes contact.

Thanks

Will have a look through at the solders see how they are.

Is there a 'good' way of looking for and cracks.. like giving the boards a little flex, or could that just make it worse

[I_Daniel]

Occasionally you will see a tiny oxide coloured ring around the lead. which could. but not for certain indicates a dry joint.
Two other ways to check
1st check with a volt meter from one joint to the other along a track. But bit dangerous you could cause a short if you are not very careful.
2nd way rather use a Ohm meter and check from one joint to the other across a track. The Power must be off.

[Major_Problem]

A simple way of supplying LED's is connecting a lot of them in series with one series resistor. Probably per column. If all LED´s are low in output, a power supply problem (low voltage) seems the first item to check.

I took a look at the e-bay site. It's a 240 V light panel. Does it use a straight forward adapter for power supply? What is the voltage on the output?

Every LED needs approx 1.5 to 4 Volt across, depending on LED colour. Count the number of LED's in series, add some voltage for the resistor and you know the minimum voltage of the adaper.

if you know the resistor value, use U=IxR to calculate the voltage across resistor (e.g. 0.01 Amp x 470 ohm = 4.7 Volt).

[Leroy Asad]

It is important not to connect the LEDs in parallel as it would lead to their ultimate failure. Keep the two branches of series connections and measure voltage across each LED and the voltage across resistor and post it here. I think the LEDs are dropping much more voltage than specified.








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