[sdiy] Vanilla electronics question

Mon Feb 19 13:36:05 CET 2024

Only: SS16 has 60V reverse voltage capability. Probably with 
considerable slack until it actually breaks down. I can't see how it 
would get into a breakdown with 12V.

The reverse leakage current of this device would be in the order where 
you can see the LED light up. (0.4mA)

IMO it's an attempt to build a current limit.

Best,

  René

Am 18.02.2024 um 00:34 schrieb Mike Bryant:
> Pure guess ... more like a breakdown current.  Sort of like a Zener 
> ... but not quite.
>
> Conversely there may be a better explanation ... just I can't think of 
> one.
> ------------------------------------------------------------------------
> *From:* Chris McDowell <declareupdate at gmail.com>
> *Sent:* 17 February 2024 23:16
> *To:* Mike Bryant <mbryant at futurehorizons.com>
> *Cc:* grant musictechnologiesgroup.com 
> <grant at musictechnologiesgroup.com>; Rutger Vlek 
> <rutgervlek at gmail.com>; SDIY List <synth-diy at synth-diy.org>
> *Subject:* Re: [sdiy] Vanilla electronics question
> wacky. Is it the leakage current of D1 that allows C1 to do anything 
> in the first place?
>
> Cheers,
> Chris
>
>> On Feb 17, 2024, at 4:59 PM, Mike Bryant <mbryant at futurehorizons.com> 
>> wrote:
>>
>> 
>> Yes fairly sure D1 is operating in some form of avalanche mode, 
>> turning the LEDs on for a short while before it recovers and turns 
>> them off again.  Could be at 100Hz, 1Hz or even 0.1Hz though, depends 
>> on C1.
>>
>> As for it not working, it's possibly because D1 is borked from being 
>> used like this.
>> ------------------------------------------------------------------------
>> *From:* Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of 
>> Rutger Vlek via Synth-diy <synth-diy at synth-diy.org>
>> *Sent:* 17 February 2024 18:35
>> *To:* grant musictechnologiesgroup.com <grant at musictechnologiesgroup.com>
>> *Cc:* SDIY List <Synth-diy at synth-diy.org>
>> *Subject:* Re: [sdiy] Vanilla electronics question
>> Here's a schematic of the circuit. These are really all the 
>> components. The entire PCB is really no more than twice the size of 
>> my finger tip. The capacitor value is unknown.
>>
>> <image.png>
>>
>>
>> Op za 17 feb 2024 om 18:58 schreef grant musictechnologiesgroup.com 
>> <http://musictechnologiesgroup.com> <grant at musictechnologiesgroup.com>:
>>
>>     Once you all get consensus on the circuit, any chance us in the
>>     peanut gallery can get some kind of schematic so we can follow
>>     along? Thanks!
>>
>>     GB
>>
>>
>>     ------ Original Message ------
>>     From "Rutger Vlek via Synth-diy" <Synth-diy at synth-diy.org>
>>     To "SDIY List" <Synth-diy at synth-diy.org>
>>     Date 2/17/2024 7:48:43 AM
>>     Subject [sdiy] Vanilla electronics question
>>
>>>     Dear list,
>>>
>>>     Against my wishes, I'm working on repairing my eBike's rear
>>>     light, instead of building something synth related. However, I'm
>>>     stumbled by a seemingly simple circuit that just does not behave
>>>     as I expected. Of course I considered buying a new rear light,
>>>     but for the sake of the planet (and my own knowledge gathering),
>>>     I'm trying to revive the original one.
>>>
>>>     The circuit is simple, I'll try to describe it. Positive voltage
>>>     (appox. 12V) from the bike's battery enters two red, parallelled
>>>     power LEDs (in forward direction), goes through a 150 ohm
>>>     resistor, and then through what seems like a Schottky diode (SMD
>>>     package labelled SS16) in reverse (!), non-conducting direction
>>>     to ground. The point before the SS16 is also connected via a
>>>     capacitor to the positive supply.
>>>
>>>     I replaced the LEDs and they are testing fine now (didn't
>>>     before). From the start I assumed the SS16 (presumed Schottky
>>>     diode) to be there for reverse voltage protection, until
>>>     today... when I looked at the direction in which it's placed.
>>>     Moreover, the resistance and power dissipation capacity of the
>>>     resistor don't seem to fit a traditional LED circuit. In other
>>>     words, the resistor would run the LEDs very close or over their
>>>     maximum current rating, and would burn out due to the heat it
>>>     had to dissipate while doing so.
>>>
>>>     So....can anyone tell me, what is this circuit? If I had to
>>>     guess, it's either:
>>>     (1) an attempt at a traditional LED circuit by someone who
>>>     messed-up badly
>>>     (2) some kind of switching voltage regulator (the rear light
>>>     indicates to be capable of handling a supply anywhere between 6V
>>>     to 12V). So I'm guessing it's the latter.
>>>
>>>     If moderation feels this is way off topic, I can completely
>>>     understand. Although I'm interested to learn about this circuit,
>>>     as it perhaps could find its way into synthesizers too.
>>>
>>>     Rutger
>>>
>>>
>>>
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