[sdiy] Vanilla electronics question

Tue Feb 20 14:22:37 CET 2024

That's probably what was intended originally, the schematic symbol for 
schottky and zener are somewhat similar after all.

Absolutely nothing hints at a switching or oscillation here at all.

And again, a 60V device should not exhibit any form of negative 
resistance at 12V. (I also think it would not do that anywhere outside 
its reverse voltage range.)

I wonder, however why they would not do the dead simplest, lowest parts 
count thing: just a resistor (per LED).

Best,

  René

Am 20.02.2024 um 13:13 schrieb rburnett at richieburnett.co.uk:
> Most likely a Zener diode to drop some of the excess voltage.
>
> -Richie,
>
>
>
> On 2024-02-19 22:34, Ben Bradley via Synth-diy wrote:
>> From the schematic I'm pretty sure that one "diode" or whatever it is
>> has to have a range of negative resistance for this thing to
>> oscillate, which I'm sure is how it works. I've not heard of schottky
>> diodes/rectifiers having negative resistance in their reverse
>> direction,  but then I don't know everything. I don't see anything on
>> the SS16 datasheet that looks like a negative resistance.
>>
>> I wonder if this could be an SCR with an internal resistor between the
>> gate and anode, so that it triggers at something below 12 volts. The
>> current through the LEDs would have to be below the "turnoff" current
>> of the SCR, and that seems questionable.
>>
>> Decades ago (1950s-1960s)  a tunnel diode was popular as an oscillator
>> in the VHF/UHF region, but apparently went obsolete when transistors
>> were made to operate at those frequencies. Electrically this could be
>> a tunnel diode, but looking on Digikey and Mouser shows no
>> possibilities for anything called a tunnel diode.
>>
>> As mentioned, a unijunction transistor is another possibility, but
>> Mouser only shows a few, at over a dollar each in any quantity, and
>> made by Central Semiconductor, which is apparently a source of
>> otherwise-obsolete semiconductors much like Rochester.
>>
>> Something like an SCR would be my best guess, but I'm not confident 
>> in that.
>>
>> On Mon, 19 Feb 2024 at 11:07, Tony Mowbray <tmowbray at ihug.com.au> wrote:
>>>
>>> Actually I think it runs as an oscillator so the operation of the 
>>> LEDs is pulsed to allow high current for a short period of time.
>>>
>>> But then again, I could be way off
>>>
>>>
>>>
>>> Regards Tony,
>>>
>>> Sent from Samsung tablet.
>>>
>>>
>>> -------- Original message --------
>>> From: René Schmitz <synth at schmitzbits.de>
>>> Date: 19/2/24 23:41 (GMT+10:00)
>>> To: synth-diy at synth-diy.org
>>> Subject: Re: [sdiy] Vanilla electronics question
>>>
>>>
>>> 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 
>>> <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
>>>
>>>
>>>
>>> ________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy at synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: 
>>> https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace at synth-diy.org
>>>
>>>
>>> ________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy at synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: 
>>> https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace at synth-diy.org
>>>
>>> -- 
>>> -- 
>>> synth at schmitzbits.de
>>> http://schmitzbits.de
>>>
>>> ________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy at synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: 
>>> https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace at synth-diy.org
>>
>> ________________________________________________________
>> This is the Synth-diy mailing list
>> Submit email to: Synth-diy at synth-diy.org
>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
>> Selling or trading? Use marketplace at synth-diy.org
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy at synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org

-- 
--
synth at schmitzbits.de
http://schmitzbits.de