Generating an external clock signal from an LED circuit

Thread Starter

RD O'Dub

Joined Jul 14, 2013
4
I have a Boss RC-50 Looper pedal that I want to use the metronome circuit for also creating an external clock for interfacing with various synthesizer modules, as well as possibly triggering lights, etc. I haven't been able to get a schematic. I did trace the circuit enough to be able to run external LEDs in parallel with the metronome LEDs.
I've experimented with connecting a 4050 hex buffer to the driver output/ LED input. This seems to work well enough, though I wonder about the reliability. I assume there's a LSI chip of some sort that's driving the LED. Scoping the LED input shows an irregular pulse that's about 3 volts, with a good bit of noise. I'm not real big on transistor theory, but I'm wondering if I should use a JFET (common source amp?) between the the driver output/ LED input and the buffer input to give a bit of a signal boost.
Am I headed in the right direction?
 

Papabravo

Joined Feb 24, 2006
13,924
I have a Boss RC-50 Looper pedal that I want to use the metronome circuit for also creating an external clock for interfacing with various synthesizer modules, as well as possibly triggering lights, etc. I haven't been able to get a schematic. I did trace the circuit enough to be able to run external LEDs in parallel with the metronome LEDs.
I've experimented with connecting a 4050 hex buffer to the driver output/ LED input. This seems to work well enough, though I wonder about the reliability. I assume there's a LSI chip of some sort that's driving the LED. Scoping the LED input shows an irregular pulse that's about 3 volts, with a good bit of noise. I'm not real big on transistor theory, but I'm wondering if I should use a JFET (common source amp?) between the the driver output/ LED input and the buffer input to give a bit of a signal boost.
Am I headed in the right direction?
A 4050 hex buffer is a robust chip that accepts a wide range of Vcc values. Why would you question the reliability of such a chip?
Second question is what do you want to boost the signal from and to?
Not entirely sure you are headed in the right direction or not.
 

Thread Starter

RD O'Dub

Joined Jul 14, 2013
4
A 4050 hex buffer is a robust chip that accepts a wide range of Vcc values. Why would you question the reliability of such a chip?
Second question is what do you want to boost the signal from and to?
Not entirely sure you are headed in the right direction or not.
It's not so much the reliability of the 4050, but of it getting a consistently clean input, without any false triggering. The 4050 would run off the supply voltage, which is about 9v. The idea is to jack the 3v pulse up to something closer to the supply voltage for a more consistent input.
 

Thread Starter

RD O'Dub

Joined Jul 14, 2013
4
You might do better with a driver chip instead of a hex buffer.

Where the noise is coming from...well you will need to find that yourself.
I don't think it's as much "noise" (as in noise being generated from somewhere else, and showing up on that line) as it is just slop from firing the LED.
A driver chip? As in some sort of bus driver?
 

ElectricSpidey

Joined Dec 2, 2017
1,175
Yea, something like a ULN2004, or such.

Will give you more power to drive a brighter LED than a logic buffer, and can also shift voltage levels, and doesn't need a logic input, such as a logic buffer. (high/low)

When you drive a 4050/49 from that source you may need to use pull up/down resistors to make it work correctly, and avoid floating inputs.

No need for any "signal boost" those Darlingtons will give you plenty.
 
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Thread Starter

RD O'Dub

Joined Jul 14, 2013
4
Yea, something like a ULN2004, or such.

Will give you more power to drive a brighter LED than a logic buffer, and can also shift voltage levels, and doesn't need a logic input, such as a logic buffer. (high/low)

When you drive a 4050/49 from that source you may need to use pull up/down resistors to make it work correctly, and avoid floating inputs.

No need for any "signal boost" those Darlingtons will give you plenty.
I'll check out the ULN2004. I knew about the no-floating inputs, but hadn't thought about pull up/down resistors. Thanks!
 
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