4017 sequencer led help?

[daverdave]

Hey all, I just wondered if anyone could give me a clue as to how to wire the leds in a simple 4017 based sequencer like the vanishing point so that they stay at the same brightness, without being affected by the pots?

[oskar]

If they are to indicate what step in the sequence you are on you can tie them to the same resistor going to ground.

[frequencycentral]

http://www.cgs.synth.net/modules/gate_sequencer2.html

[kvb]

you will have to add some extra logic to separate what is going through the pots from what is going through the LEDs.

you could also just run a parallel 4017 to your LEDs
the switches that control stages would need to be dual

[daverdave]

If they are to indicate what step in the sequence you are on you can tie them to the same resistor going to ground.

I'm not sure what you mean, there's no resistors on the vanishing point near the pots, do you mean tie one before the pot to ground or after, I'd have thought that they would still change brightness with the pots setting.

[slacker]

Instead of connecting the LEDs between the outputs and the pots connect the pots straight to the outputs of the 4017. Then connect the anodes of the LEDs to the outputs of the 4017 as well and connect the cathodes to ground through a suitably sized resistor. If all your LEDs are the same you can just tie all the cathodes together and use one resistor to ground.

Another way to do it would be to keep the LEDs where they are on the vanishing point but wire the pots as voltage dividers instead of how they are now. Basically wire them like you would a volume pot with one outer lug going to ground, that way the LED has the same resistance to ground no matter where the pot is set. That would probably require reworking some of the other circuitry in the vanishing point though.

[frequencycentral]

http://www.midiwall.com/gear/babyseq/

[daverdave]

Great, thanks for the replies. I'll have a play around and see what works best.

[The Tone God]

Its going to comedown to how much current you indicator and opto LEDs are going to need. Connecting a set of LEDs right off the outputs before the pots will work but you will tap come of the current needed for the optocoupler LED so as you change the pots settings you can cause changes in the brightness of the indicator LED which kind of defeats the purpose of all this work.

The "safer" option is to use a driver off the line like with a gate or a transistor. I did that in VP v1.0. I choose not to do it as people were already overwhelmed by the circuit and they always had the option to add it if they liked without scaring off the newbies.

Andrew

[daverdave]

Cheers, I'll have a look at different ways to do it.