<div dir="ltr">Flashing the LED quickly can make it much more visible. For a safety device (bike light) this would be desirable.</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Feb 20, 2024 at 6:23 AM René Schmitz <<a href="mailto:synth@schmitzbits.de">synth@schmitzbits.de</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">That's probably what was intended originally, the schematic symbol for <br>
schottky and zener are somewhat similar after all.<br>
<br>
Absolutely nothing hints at a switching or oscillation here at all.<br>
<br>
And again, a 60V device should not exhibit any form of negative <br>
resistance at 12V. (I also think it would not do that anywhere outside <br>
its reverse voltage range.)<br>
<br>
I wonder, however why they would not do the dead simplest, lowest parts <br>
count thing: just a resistor (per LED).<br>
<br>
<br>
Best,<br>
<br>
René<br>
<br>
<br>
<br>
Am 20.02.2024 um 13:13 schrieb <a href="mailto:rburnett@richieburnett.co.uk" target="_blank">rburnett@richieburnett.co.uk</a>:<br>
> Most likely a Zener diode to drop some of the excess voltage.<br>
><br>
> -Richie,<br>
><br>
><br>
><br>
> On 2024-02-19 22:34, Ben Bradley via Synth-diy wrote:<br>
>> From the schematic I'm pretty sure that one "diode" or whatever it is<br>
>> has to have a range of negative resistance for this thing to<br>
>> oscillate, which I'm sure is how it works. I've not heard of schottky<br>
>> diodes/rectifiers having negative resistance in their reverse<br>
>> direction, but then I don't know everything. I don't see anything on<br>
>> the SS16 datasheet that looks like a negative resistance.<br>
>><br>
>> I wonder if this could be an SCR with an internal resistor between the<br>
>> gate and anode, so that it triggers at something below 12 volts. The<br>
>> current through the LEDs would have to be below the "turnoff" current<br>
>> of the SCR, and that seems questionable.<br>
>><br>
>> Decades ago (1950s-1960s) a tunnel diode was popular as an oscillator<br>
>> in the VHF/UHF region, but apparently went obsolete when transistors<br>
>> were made to operate at those frequencies. Electrically this could be<br>
>> a tunnel diode, but looking on Digikey and Mouser shows no<br>
>> possibilities for anything called a tunnel diode.<br>
>><br>
>> As mentioned, a unijunction transistor is another possibility, but<br>
>> Mouser only shows a few, at over a dollar each in any quantity, and<br>
>> made by Central Semiconductor, which is apparently a source of<br>
>> otherwise-obsolete semiconductors much like Rochester.<br>
>><br>
>> Something like an SCR would be my best guess, but I'm not confident <br>
>> in that.<br>
>><br>
>> On Mon, 19 Feb 2024 at 11:07, Tony Mowbray <<a href="mailto:tmowbray@ihug.com.au" target="_blank">tmowbray@ihug.com.au</a>> wrote:<br>
>>><br>
>>> Actually I think it runs as an oscillator so the operation of the <br>
>>> LEDs is pulsed to allow high current for a short period of time.<br>
>>><br>
>>> But then again, I could be way off<br>
>>><br>
>>><br>
>>><br>
>>> Regards Tony,<br>
>>><br>
>>> Sent from Samsung tablet.<br>
>>><br>
>>><br>
>>> -------- Original message --------<br>
>>> From: René Schmitz <<a href="mailto:synth@schmitzbits.de" target="_blank">synth@schmitzbits.de</a>><br>
>>> Date: 19/2/24 23:41 (GMT+10:00)<br>
>>> To: <a href="mailto:synth-diy@synth-diy.org" target="_blank">synth-diy@synth-diy.org</a><br>
>>> Subject: Re: [sdiy] Vanilla electronics question<br>
>>><br>
>>><br>
>>> Only: SS16 has 60V reverse voltage capability. Probably with <br>
>>> considerable slack until it actually breaks down. I can't see how it <br>
>>> would get into a breakdown with 12V.<br>
>>><br>
>>><br>
>>><br>
>>> The reverse leakage current of this device would be in the order <br>
>>> where you can see the LED light up. (0.4mA)<br>
>>><br>
>>> IMO it's an attempt to build a current limit.<br>
>>><br>
>>><br>
>>> Best,<br>
>>><br>
>>> René<br>
>>><br>
>>><br>
>>><br>
>>> Am 18.02.2024 um 00:34 schrieb Mike Bryant:<br>
>>><br>
>>> Pure guess ... more like a breakdown current. Sort of like a Zener <br>
>>> ... but not quite.<br>
>>><br>
>>> Conversely there may be a better explanation ... just I can't think <br>
>>> of one.<br>
>>> ________________________________<br>
>>> From: Chris McDowell <<a href="mailto:declareupdate@gmail.com" target="_blank">declareupdate@gmail.com</a>><br>
>>> Sent: 17 February 2024 23:16<br>
>>> To: Mike Bryant <<a href="mailto:mbryant@futurehorizons.com" target="_blank">mbryant@futurehorizons.com</a>><br>
>>> Cc: grant <a href="http://musictechnologiesgroup.com" rel="noreferrer" target="_blank">musictechnologiesgroup.com</a> <br>
>>> <<a href="mailto:grant@musictechnologiesgroup.com" target="_blank">grant@musictechnologiesgroup.com</a>>; Rutger Vlek <br>
>>> <<a href="mailto:rutgervlek@gmail.com" target="_blank">rutgervlek@gmail.com</a>>; SDIY List <<a href="mailto:synth-diy@synth-diy.org" target="_blank">synth-diy@synth-diy.org</a>><br>
>>> Subject: Re: [sdiy] Vanilla electronics question<br>
>>><br>
>>> wacky. Is it the leakage current of D1 that allows C1 to do anything <br>
>>> in the first place?<br>
>>><br>
>>> Cheers,<br>
>>> Chris<br>
>>><br>
>>> On Feb 17, 2024, at 4:59 PM, Mike Bryant <br>
>>> <<a href="mailto:mbryant@futurehorizons.com" target="_blank">mbryant@futurehorizons.com</a>> wrote:<br>
>>><br>
>>> <br>
>>> Yes fairly sure D1 is operating in some form of avalanche mode, <br>
>>> turning the LEDs on for a short while before it recovers and turns <br>
>>> them off again. Could be at 100Hz, 1Hz or even 0.1Hz though, <br>
>>> depends on C1.<br>
>>><br>
>>> As for it not working, it's possibly because D1 is borked from being <br>
>>> used like this.<br>
>>> ________________________________<br>
>>> From: Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org" target="_blank">synth-diy-bounces@synth-diy.org</a>> on behalf of <br>
>>> Rutger Vlek via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" target="_blank">synth-diy@synth-diy.org</a>><br>
>>> Sent: 17 February 2024 18:35<br>
>>> To: grant <a href="http://musictechnologiesgroup.com" rel="noreferrer" target="_blank">musictechnologiesgroup.com</a> <<a href="mailto:grant@musictechnologiesgroup.com" target="_blank">grant@musictechnologiesgroup.com</a>><br>
>>> Cc: SDIY List <<a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a>><br>
>>> Subject: Re: [sdiy] Vanilla electronics question<br>
>>><br>
>>> Here's a schematic of the circuit. These are really all the <br>
>>> components. The entire PCB is really no more than twice the size of <br>
>>> my finger tip. The capacitor value is unknown.<br>
>>><br>
>>> <image.png><br>
>>><br>
>>><br>
>>> Op za 17 feb 2024 om 18:58 schreef grant <a href="http://musictechnologiesgroup.com" rel="noreferrer" target="_blank">musictechnologiesgroup.com</a> <br>
>>> <<a href="mailto:grant@musictechnologiesgroup.com" target="_blank">grant@musictechnologiesgroup.com</a>>:<br>
>>><br>
>>> Once you all get consensus on the circuit, any chance us in the <br>
>>> peanut gallery can get some kind of schematic so we can follow <br>
>>> along? Thanks!<br>
>>><br>
>>> GB<br>
>>><br>
>>><br>
>>> ------ Original Message ------<br>
>>> From "Rutger Vlek via Synth-diy" <<a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a>><br>
>>> To "SDIY List" <<a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a>><br>
>>> Date 2/17/2024 7:48:43 AM<br>
>>> Subject [sdiy] Vanilla electronics question<br>
>>><br>
>>> Dear list,<br>
>>><br>
>>> Against my wishes, I'm working on repairing my eBike's rear light, <br>
>>> instead of building something synth related. However, I'm stumbled <br>
>>> by a seemingly simple circuit that just does not behave as I <br>
>>> expected. Of course I considered buying a new rear light, but for <br>
>>> the sake of the planet (and my own knowledge gathering), I'm trying <br>
>>> to revive the original one.<br>
>>><br>
>>> The circuit is simple, I'll try to describe it. Positive voltage <br>
>>> (appox. 12V) from the bike's battery enters two red, parallelled <br>
>>> power LEDs (in forward direction), goes through a 150 ohm resistor, <br>
>>> and then through what seems like a Schottky diode (SMD package <br>
>>> labelled SS16) in reverse (!), non-conducting direction to ground. <br>
>>> The point before the SS16 is also connected via a capacitor to the <br>
>>> positive supply.<br>
>>><br>
>>> I replaced the LEDs and they are testing fine now (didn't before). <br>
>>> From the start I assumed the SS16 (presumed Schottky diode) to be <br>
>>> there for reverse voltage protection, until today... when I looked <br>
>>> at the direction in which it's placed. Moreover, the resistance and <br>
>>> power dissipation capacity of the resistor don't seem to fit a <br>
>>> traditional LED circuit. In other words, the resistor would run the <br>
>>> LEDs very close or over their maximum current rating, and would burn <br>
>>> out due to the heat it had to dissipate while doing so.<br>
>>><br>
>>> So....can anyone tell me, what is this circuit? If I had to guess, <br>
>>> it's either:<br>
>>> (1) an attempt at a traditional LED circuit by someone who messed-up <br>
>>> badly<br>
>>> (2) some kind of switching voltage regulator (the rear light <br>
>>> indicates to be capable of handling a supply anywhere between 6V to <br>
>>> 12V). So I'm guessing it's the latter.<br>
>>><br>
>>> If moderation feels this is way off topic, I can completely <br>
>>> understand. Although I'm interested to learn about this circuit, as <br>
>>> it perhaps could find its way into synthesizers too.<br>
>>><br>
>>> Rutger<br>
>>><br>
>>><br>
>>><br>
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