[sdiy] Vanilla electronics question

Tue Feb 20 17:24:59 CET 2024

Flashing the LED quickly can make it much more visible.  For a safety
device (bike light) this would be desirable.

On Tue, Feb 20, 2024 at 6:23 AM René Schmitz <synth at schmitzbits.de> wrote:

> 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
>
> ________________________________________________________
> 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
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20240220/010c5347/attachment.htm>