I need to make a coupling pole for 3-link couplings, and as any fule kno, these must be attached to a small torch so you can see what you are doing. Furkling around in the gloom trying to fish for small chain links is a whole load of no fun.
Finding a suitable torch isn't as easy as you might think, but I thought I had struck gold with a Wilko Inspection Pen Light. Metal, a nice length so you have control over the wire that will be fixed to it, and even a clip to hang it on your pocket.
Back at home, I found a snag. The thing has three settings, which are cycled through by switching it on and off using the button at one end - On, half-on and an epilepsy-inducing fast flash.
Seriously Wilko, why?
If you are inspecting something, you really don't need the flashing, nor the half-on. On and off, that will do the job.
Worse, it made the torch useless for my purposes. Full on is perfect. Half on less use, and the flashing gave me a headache.
There was only one thing to do - take it apart and rebuild it.
A quick check with the continuity tester showed that the switching was all handled at the opposite end to the light. No need to fiddle here.
At the business end, we find a circuit board. The batteries bear on the reverse of this, but between them and the LED lights are some surface mount components.
A bit of work with the soldering iron, the components were removed, and the wires disconected. Then all I had to do was poke around with the tester again to find out where the postive and negative connections were to be found. Solder the wires to these, and then reassemble it back into the light-up bit, and it worked!
3 comments:
I'm intrigued by the modifications - LEDs want to be driven by a constant current source, in crude terms this can be approximated with a resistor, but increasingly higher power torches will using a switching DC-DC convertor to control the current (easily identifiable from the inclusions of an inductor on a little PCB).
Having now removed the components that make up the constant current source (as well as providing the annoying 'modes' - which I agree are a pain), what is now limiting the current to prevent the LEDs being overloaded and thus reducing their lifespan?
With only 2AA batteries in the torch, the LEDs are being fed a nice, constant 3V so hopefully, they should last OK. We'll see!
Given that the torch is still working, perhaps the LED is one with a built-in resistor rather than a separate component, so no need to worry? Received wisdom is that too many milliAmps (even from AA batteries) will damage an LED without some form of current-limiting, but I’ve never tested it… ;-)
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