Re: For those who believe in electricity

On 4/9/2025 7:44 AM, zen cycle wrote:

On 4/8/2025 12:33 PM, Frank Krygowski wrote:

On 4/7/2025 11:56 AM, sms wrote:

On 4/7/2025 8:16 AM, Zen Cycle wrote:

On 4/6/2025 10:22 PM, Frank Krygowski wrote:

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A battery puts out DC, it does not provide "half of a sine wave."
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An LED dynamo light would be rectifying the AC into DC, though there are ways around this if the light has multiple LEDs (two LEDs each conducting for half the cycle). If there is only a single LED it can still be powered by the AC from the dynamo but it would be wasteful as it would only be lit for half the cycle.

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First, here's what I said: "I had hoped to diagnose it using DC, figuring a 6 volt battery would essentially supply half of the sine wave so half of the input circuit. That naturally works with incandescents, and it worked with one Avenir LED dyno headlight that I repaired."
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My reference to "essentially half the sine wave" meant that electron flow from a DC battery would be in the same direction as the flow during half the sine wave, and might serve to determine what part of the circuit was open.
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And as I said, the DC source has worked with other LED dyno headlights. It works with the Avenir I own, it works with a B&M Lyt that I just tested. Both are single LED headlamps. It didn't work with the B&M Eyc I'm trying to repair. But maybe that's related to its inconsistent and intermittent fault.
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As I mentioned in discussions here years ago, one LED dyno headlight I own has a very simple circuit: IIRC just a bridge rectifier, a voltage regulator, a resistor and a capacitor feeding one LED.
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It's obvious from my photos of this B&M lamp that the electronics are much more complicated. I'm disappointed that the electronics experts here have never commented on what the likely functions of all that complexity.

 You didn't ask that question previously:
 The lamp is significantly more complex in order to control multiple LEDs with different drive levels by processing input sensor sensor data.
 According to the user manual, it has several modes of operation:
 https://www.bumm.de/files/Produkte/LUMOTEC%20Eyc_Avy_IQ-XS.PDF
 "Functionality of the sensor mode:
During daylight, the headlight operates in “day mode”.
The driving light LED in the headlight shines dimmed onto the road. The additional DRL LEDs shine with full luminance. Maximal visibility for oncoming traffic!
(Eyc T, IQXS T: The indicator LED in the rear push button shines with full intensity.)
During dusk or darkness, the headlight automatically switches to “night mode”. The driving light emits the full luminance. The daytime running LEDs stay dark (Eyc T,IQXS T) or shine with diminished luminance (Avy T). Maximum vision, additional visibility for oncoming traffic! (Eyc T, IQXS T: The indicator LED in the rear push button shines dimly.)
The light/dark sensor switches the headlamp from mode “Night” to “Day” with a predetermined delay of 8 sec. so that a temporary brightness (e.g. car headlights turned up) will not cause immediate switching."
 These different modes require processing information from the sensors to switch the drive control of the different LEDs. That 16 pin device I've been asking about is likely a micro controller with a simple program performing a Boolean function.
 This LEDs are likely being driven by a PWM circuit to control the brightness of more than one LED. The PWM circuit is being controlled by the sensor circuits.
 As noted in the manual excerpt, the lamp will autoswitch dring daylight hours to a DRL mode, and at night has a delay of 8 seconds so car headlights don't autodim the lamp (likely controlled by the uC). Then there's the 'standby mode' where the unit switches from the power supply to the storage cap while stopped. This may be a simple analog circuit but it may also be a digitally controlled switch that senses when power is being generated from the dynamo.
 So, yes, significantly more complex than a basic LED being driven from a power supply.

I suspect most of that document refers to a later model of this headlight. (Mine is ten years old.) I say that because of the remarks about multiple LEDs, etc. This one has only one LED, it has no "senso" or auto-control function. There is an ineffective yellow "indicator LED" at the switch end. It's incredibly tiny - maybe 0.1mm diameter - and so dim I didn't notice it at first.
I suppose it's possible they designed one circuit board for all existing and upcoming models of the headlight. There seem to be several unused solder pads near the one LED in this photo: https://www.flickr.com/photos/16972296@N08/54435279894/in/dateposted-public/
The LED is the bright white rounded square toward the "top" of the photo. That "top" edge faces forward in the assembled headlight.
If that's the case, then most of the circuitry might be redundant in the headlight I own.
Incidentally, Rolf mentioned getting extra power out of the dynamo. My digital meter consistently shows 4 VAC when the lamp is running off my drill press. (That's at an effective road speed of about 14 mph.) Given that bike dynamos are essentially constant current devices pumping about half an amp, it seems like it's drawing only about two Watts electrical power. Mechanical input would be more than two Watts, of course - maybe four to six Watts.
Which reminds me that in my phone call with Peter White, he says he never bothers to turn his headlamps off. Especially with a hub dyno, the power draw is negligible. This is a bottle dyno, so zero watts drawn when I swing it out of contact.
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- Frank Krygowski