Like a mystery?

I’m cannibalizing two identical bicycle LED strobe units for my MOB
pole. The circuit boards have a push button that cycles between
Flash – Steady – Off but are set up so they are ON and flashing as
soon as power is applied such as when you first put the batteries in.
I want flashing so I’m just ignoring the switch and switching the
power to the boards.

As I’m sure you know, soldering little things like this isn’t for the
faint of heart so I’m testing at each step. The first one came out
perfectly. The second won’t go on. I tried with just one battery
(running out of ideas) and it goes on! It’s flashing although at half
brightness. With one and one half volts, it works. With the proper 3
volts, nada. The first one also works with one battery at half
brightness.

What do you think gives?


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Roger Long

hi roger,

my only thought on this is that if i were doing it i'd probably use a
PIC processor instead of the little circuit board. you can get a PIC
that would do the job for under 1$us and it would be very small with
just 6 pins, 2 of which are for power and ground, so it's very small.
of course you'd have to already have the programmer and things to do
it. using a PIC and programming it you could also control the speed
that the LED blinks at and you could put in a wait at the beginning of
the code so that it'll idle until the internal clock stabalizes on
power up, etc. would still operate off of 3 volts.

as for your board's problem, i don't know. i'd try a ferrite bead near
the circuit board on the wires you inserted between the LED and the
board and see what that does, maybe those long wires are feeding
something weird into the controller chip. could test that too by
insuring that the board works the way you want it to on power-up
without the wires attached, with just the LED touching the leads. just
a thought.

Thinking back, I remember that I was interrupted by having to take kid
somewhere. When I did the second light, I just plunged into it
without putting it together and testing it first. It might well have
been defective and I could have returned it. Too late now.

I was so focused on testing at every step that I forgot to test at
step 1

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Roger Long