RES: [sdiy] Question about LEDs

[Luís Marka]

On a related note, I have bicolor LEDs for modules that produce both
positive and negative outputs - my LFOs, for example.
In order to activate those accordingly (RED when the output is positive,
GREEN when it goes negative), I had to use a number of components in the LED
drive circuitry. Positive is fine: resistor + NPN transistor + LED + current
limiting resistor. Now, for the negative side I had to first invert the
input via one op. amp at unitary gain, then it goes diode (so only the
negative semicicle is taken in account) + resistor + transistor + LED +
resistor. The LED is a common-cathode (3 wire) LED.

Is there a simpler way I could have done it?

Luis Marka

-----Mensagem original-----
De: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]Em nome de Oren Leavitt
Enviada em: terça-feira, 7 de abril de 2009 05:48
Para: synth-diy at dropmix.xs4all.nl
Assunto: Re: [sdiy] Question about LEDs


Each blinking LFO LED is a little mouth saying
"me!...me!...me!...me!..." when one approaches the LFO panel with a
patch cord.
- Oren - The only dumb questions are unasked ones

Magnus Danielson wrote:
> Jason Proctor skrev:
>
>>> This may seem like a dumb question, but when you have a module such as a
>>> simple LFO with a rate-indicating LED -- something like the MOTM-390,
>>> say --
>>> is the LED typically always blinking, even when nothing is plugged
>>> into the
>>> circuit, or is it typically deactivated somehow when the module is
>>> not being
>>> used?
>>
>>
>> the LFO is running regardless of whether it's plugged into anything,
>> therefore yes, the LED blinks.
>
>
> As they should.
>
>> i just unplugged my MOTM-320s from their duties, and they are blinking
>> away merrily.
>
>
> Asking their master "please don't forget me, I want to assist you in
> your creativity". :)
>
> Yes, I think they really *SHOULD* blink...
>
> Cheers,
> Magnus
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