Solutions to Potential Problems with your Alien Eye

The low cost 5.5x2.1 mm DC barrel connector and hollow plug can be sometimes be sensitive to position and cause intermittent connections.  This results in your light flickering or even going out while riding.   Since the hollow plug must have a clearance fit to the DC barrel connector for easy removal, the hollow plug must be biased to one side so that the outside diameter makes contact and the inside diameter makes contact on the other side.    To create this bias, there is a small wire spring in most DC barrel connectors.  

With a pin or some pointed object rotate the position of the spring clockwise until you get a reliable connection.   Do not bend the wire to try to increase the tension.   Any subsequent bending will probably break the spring wire, or weaken it and then it could break when you need your lamp the most.   I have replaced a broken spring in a lamp.   It was not easy to fish the remaining piece of the old spring out of the groove.

Short Circuit Problems

It took me a while to find this problem and solve it but it all makes sense now.  If you find your battery holder is melted in a few places then you know there is a short circuit some where in your system.   The short circuit can occur between the DC barrel connector and the hollow plug when they are plugged together.   If the inside metal contact (+ terminal) of the hollow plug extends beyond the insulating plastic layer, then the exposed + terminal can cause a short circuit on the inside of the barrel connector (- terminal) if the hollow plug is longer than the DC barrel connector is deep.  I made a rubber insulating shim by using bicycle inner tube material and a revolver hole punch.    I found a few hollow connectors with this problem on cables that came with Li Ion Batteries from Hong Kong.  If your hollow connector is short and does not bottom out in the DC barrel connector you should not have a problem.  I add the rubber washer as a default option on all the lamps I build.

Punch out a 4.5 - 5 mm circular piece of rubber from an old inner tube.   Punch a 2 mm center hole.

Place the insulating shim on the hollow connector.   Insert the rubber insulating shim in the DC barrel connector.