Question about flashlight construction

I use inexpensive LED flashlights at work. They get beat up and destroyed and lost in action (read stolen). Expensive lights would be inappropriate, so i'm trying to make the cheap ones work.

The circuit board makes contact with the aluminum tube at 4 spots. These contact points occasionally corrode and become resistive. It seems that lead and aluminum naturally corrode when in contact with each other. (galvanic reaction?)




I use a wire brush on a dremel to clean them and apply no-ox to slow the oxidation rate.

My question (finally) is: How do expensive lights make trouble-free connection between the circuit board and the tube?

Thanks!

DennisMenace said:

My question (finally) is: How do expensive lights make trouble-free connection between the circuit board and the tube?

Click to expand...

The owners take good care of the light because it is a fenix

DennisMenace said:

I use a wire brush on a dremel to clean them and apply no-ox to slow the oxidation rate.

My question (finally) is: How do expensive lights make trouble-free connection between the circuit board and the tube?

Thanks!

Click to expand...

My Mini Mag Lite (heh) uses a sliding contactor of some silver metal to get the (-) connection to the flashlight body. This is probably steel or aluminum.

Other lights use brass/copper plated contacts to reduce the reactivity. Solder will not stick to Aluminum, so you are unlikely to be able to just make a solder to solder contact point. However, you COULD solder a thin ring of another metal to the contact points to improve things there.

DennisMenace said:

It seems that lead and aluminum naturally corrode when in contact with each other.

Click to expand...

Both aluminium and lead naturally corrode, period. Lead usually worse in my experience.

(galvanic reaction?)

Click to expand...

Possible - that would speed up things even more.

Google images for "flashlight driver board" and notice the gold plated ring around the outside of many boards (often both sides o/t board). Usually that's pressed in between a so called "pill" (cooling / LED holder etc), and a brass ring that screws onto that pill. With that assembly screwed into the flashlight body. So that's 'pressurized' gold <-> brass contacts in ring shape, and large brass <-> brass or brass <-> aluminium contact areas elsewhere. The battery (or top one) contacts driver board directly at the + pole.

That's just one way to do it, but a common one. Note that's not a feature unique to expensive lights! My $5 Sipik SK68 is built like that, with a spring that looks gold plated, beryllium copper (or something like that) on bottom end.

I suggest you replace your light with something better. Cheap if necessary, but better... I'd recommend Convoy lights if ~20 US$ is within your budget.

Most better built lights use brass or copper in their electrical contacts and do not rely on the solder holding things together to function as the contact. I would say that the lights you are using...if that picture is the common way they are made...are not simply inexpensive, but also poorly made lights. I think you might be better served by spending a bit more money on your lights.

I know that sometimes people are more likely to walk away with your tool if they think it is not only easily replaced, but also cheaply replaced...doesn't matter that it isn't theirs.

Many thanks for all the excellent responses!

I saw them on sale 5 for $10, so I figured "what could possibly go wrong?"oo: Anyway, they've lasted 2 years so far with only periodic maintenance. I'll spend more money on the next light once these have been used up.