On Sun, 7 Oct 2018 17:27:35 -0400, Frank Krygowski
wrote:
On 10/6/2018 3:44 PM, Jeff Liebermann wrote:
I like to photograph what I tear apart and reverse engineer. For
example, in the bicycle section:
Cygolite Streak 280 headlight:
http://www.learnbydestroying.com/jeffl/pics/bicycles/Cygolite%20Streak%20280/index.html
K1009 headlight:
http://www.learnbydestroying.com/jeffl/pics/bicycles/K1009%20light/index.html
Since I'm a mechanical guy, not an electronics guy: Both of those seem
to show far more electronics bits than I'd have thought necessary. Any
chance of getting you to explain what they do?
Sure, but I'll need to trace out the schematic in order to give a sane
explanation. That will take about an hour to do (including drawing a
readable schematic and maybe some oscilloscope waveforms). Some of
the chips are not labeled, but I have a good idea what they might be.
I'll do it if you really want it done, but it will need to wait a week
or two when I hopefully will have the time.
I had an off-brand LED dynamo light fail on me. The LED fried itself.
Not exactly. It probably overheated because the thermal connection
between the back of the LED and the COB (chip on board) aluminum heat
sink was probable poorly connected. I've had it happen to me. I
tried to glue another tiny LED to the COB, but it didn't last. So, I
bought a replacement COB, filed few extra notches to make it fit, and
it's working today.
In
the course of replacing it (which was difficult because of the lack of
wowrking space) I was able to take some guesses at the function of the
circuitry components - rectifying, regulating, etc. But there were only
about six or eight electronic devices in there. I'm surprised a DC
battery lamp needs much at all.
Well, the basics electronic components a
1. One or more LED's on a COB or "star" heat sink.
2. A constant current driver IC that delivers about 350ma to each
LED. This is typically an AMC7135 chip and easily recognized because
of its SOT-89 package:
https://www.google.com/search?q=7135+LED+driver&tbm=isch
https://www.electroschematics.com/wp-content/uploads/2016/04/acm7135-datasheet.pdf
If you need more than 350ma, just add more 7135 chips in parallel such
as this abomination with 4 chips:
http://lygte-info.dk/pic/DriverTest/IO/Qlite%20Rev.A%207135x8%20Multiple%20Modes/DSC_3691a.jpg
3. A PWM (pulse width modulation) light dimmer and controller. That's
the 8 pin chip in the above JPG. If you want half the average light
output, just modulate the DC power to the LED with a 50% duty cycle.
0% is power off. 100% is maximum output. Some have an automatic
power off timer. The chips is a low end Arduino MPU.
That's the basics. Some optional extras a
1. Battery charging circuitry.
2. BMS (battery management system) to prevent running the batter down
to below about 2.7VDC, which tends to kill the battery, above 4.2VDC,
which tends to kill the battery, charging at too much current, which
tends to kill the battery, or inserting the battery backwards, which
tends to kill everything.
3. Stand light circuit. Basically a super capacitor and a switching
transitor or MOSFET. When the dynamo isn't producing power, the super
capacitor takes over.
4. Battery charge indicator.
5. Warranty timer that blow up something just after the warranty
expires.
Questions?
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558