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From: Roger Merriman <roger@sarlet.com>
Newsgroups: rec.bicycles.tech
Subject: Re: For those who believe in electricity
Date: 11 Apr 2025 09:15:40 GMT
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Frank Krygowski <frkrygow@sbcglobal.net> wrote:
> On 4/8/2025 8:56 PM, Frank Krygowski wrote:
>> 
>> The switch is the tiny white box toward the bottom of this photo:
>> https://www.flickr.com/photos/16972296@N08/54435279894/in/dateposted- 
>> public/ just below "3R 46 16V" which is probably a capacitor. The black 
>> pushbutton sticks out downward in the photo (or backwards, in the 
>> mounted headlight) and looks odd in the photo, again because of 
>> reflections. That switch is about 4.5mm x 2.5mm x 1.8mm tall. I removed 
>> the switch from the circuit board.
>> 
>> I had assumed it was a toggle, but it seems instead to be a momentary 
>> switch. It connects to five tiny solder pads. The two big ones, at the 
>> "bottom" of the switch in the photo, are just for fastening it to the 
>> board. At the "top" face in the photo are three very tiny pads, call 
>> them A, B and C.
>> 
>> Playing with a jumper wire ending in two sharp pins, I found that 
>> momentary contact from A to C changed the state of the light, on to off 
>> to back on, etc. A to B did the same. I had to be careful to touch 
>> fairly quickly and not bounce.
>> 
>> At last check, the light is in "on" state. I think if I don't disturb 
>> things, it should stay in that state, and I can try reassembling and 
>> testing it on the bike. I've got other stuff to work on tonight, so I'll 
>> get back to it tomorrow.
> 
> More bench testing this morning. The headlamp started right up, 
> perfectly consistently when driven by the dynamo spun with my drill 
> press. Momentarily jumping A to C (or B) of those switch solder pads 
> toggled the lamp on or off while running the dynamo. Shutting down the 
> dynamo put the lamp into "standlight" mode. In that mode, with no 
> voltage input, jumping A to C turned off the standlight. Applying power 
> turned the lamp back on, no switching necessary. It seems the headlight 
> is operating as it should.
> 
> I'm convinced the problem was that faulty switch, probably with internal 
> parts rattling around enough to occasionally toggle that A to C or A to 
> B contact. I suspect it will work fine if I successfully reassemble it 
> without the switch.
> 
> It's still slightly worrisome, because a headlight really does have to 
> be reliable. Maybe I'll carry a little battery light as a spare for a 
> while. I often do that anyway when night riding with others, because of 
> so many incidents of other folks' headlights failing on rides.
> 
Who on earth to you ride with that have light failures? I’ve never had a
light fail on the ride, I’ve had in the early days ooh batteries is a bit
tired as the light dims as the battery can’t hold the voltage any more, and
had cheap lights mounts and so on start to wear.

I still have multiple lights that I’ve upgraded from which still work, but
time and technology has moved on.

Likewise I see a lot of bikes, and meet up with folks for a Wednesday night
ride, most weeks it’s not a thing that is common, it’s not impossible but
definitely rare.

Roger Merriman