My LED grow light stopped working! Now what?

A couple weeks ago, I noticed that the LED grow light under a couple of my plants was particularly weak.  After checking it out, I saw two of the light pucks were burnt out.  How could this be?  The lights only have a few thousand hours on them and have a design life of 25,000 hours.  Since I bought my lights second hand, I didn’t have a warranty option so I decided to open the lights up and see what I could learn.

The unit in question was a Hydrogrow 84X2 Pro, which took me removing 8 small screws to open up.  Inside there were 3 power supplies, a fan, four light pucks, and wiring.

I compiled my list of necessary tools:

  • Screwdrivers and Drill if you want to pull it apart faster
  • Jumper wires
  • Multimeter
  • A power source – I used an Arduino, but you’ll need a 5V source
  • Electric tape or soldering iron

After opening the light, I found this was the setup:

IMG_0896

You’ll notice that each set of two light pucks has it’s own 5V power supply.  The first step was figuring out if the power supply was working and the lights were dead, or if the power supply failed.  As you can see, each of the sets is wired in series, so if one fails, both lights go out.  I removed a puck (lower left in the picture) that I knew worked and changed it out with the puck in the upper left (either would do the trick).  When I clipped in the working puck and switched the light on, the broken side lit up which indicated a working power supply and the dead puck was the one I removed.  Another test would have been to plug the dead puck into the spot where I removed the working one and try that.

Once I isolated the dead puck, I decided I had two options.  First, I could buy a new puck and have it shipped from China.  This taking a long time and costing more money (21 LEDs lights @ 2 per light = $42) was not my first choice.  Second, I could find the culprit LEDs and short them.  I decided to give that a try–after all, I had nothing to lose!  The blank chip with the LEDs looks like this:

IMG_0900

I ran 5V power from my Arduino Mega to two jumper cables and tested each light at it’s base.  I made a map of what lights worked and which didn’t respond as I thought (see below):

troubleshooting LEDs

After I was done, I found that the center (green LED) was out.  I decided to attach a jumper wire to both sides of the LED, helping pass current around the broken LED and complete the series circuit.

To my surprise, it worked!  I reverse engineered the LED and screwed everything back.  Checking again, I have four working pucks again and the only downside is that one is missing the one burnt out LED–no big deal at all!

Just wanted to share my experience as I won’t be the last one with this problem.  Hope I saved you some time and money.

 

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