Led's on sequencer not sequencing

[acidblue]

I made this sequencer from sea-moss and replaced the 22k resistors with pots and got it working fine--yippie!
http://milkcrate.com.au/_other/sea-moss/04_seq.gif

But now I want to add led's to flash in sequence.
But it dosen't work when I add a led and it's resistor to the corresponding pins on the 4051 IC in parallel, (pins 13,14,15,12 etc.).

In fact the whole sequencer stops sequencing.
Some of the led's are fully lit and some just barely.
I have the led and resistor connected in parallel from the pin to ground.
Like you would do on a 'Baby Ten' sequencer.

What am I doing wrong?

[rich decibels]

The 4051 is a multiplexer - it works like an 8-way switch. It takes whatever is on X and connects it to one of the pins X0-X7, depending on the state of the control inputs A, B, and C. In this case the 4040 is used to cycle through every combination of A, B, and C, so X gets connected to X0, X1, X2... in sequence.

Connecting LEDs to the output pins X0-X7 unfortunately won't do what you want it to do. If you redraw the schematic with the 4051 replaced with an 8-way switch, you'll see why: switching from one output to the next doesn't actually take any of the LEDs out of the circuit.

As far as I know, the only way to get indicators on a sequencer of this type is to use another 4051 whose A, B, and C, inputs are connected to the original 4040. Connect the X input to V+ via a limiting resistor (100-3k, depending on your LED), then connect each of the X0-X7 outputs to your 8 LEDs, which are then wired to ground.

There are probably more efficient ways of doing this. For instance, there are other kinds of multiplexers that have additional channels, so you could have the oscillator on one channel and the indicators on another. I've not done it myself though, so I can't tell you exactly where to look.

Good luck!

[acidblue]

[rich decibels]

Yeah it sounds as if it's wired up wrong. Rip everything out and start again! With multiplexers I always start with LEDs to indicate that everything is working before I move on to audio signals, which can be trickier to debug.

[acidblue]

Funny thing is the audio part works fine.
It sequences like it should, just the led's just don't sequence.

[rich decibels]

you can verify your wiring by connecting A, B, and C to ground. only one LED should be lit. Now connect just A to V+, a different LED should light. and so on, one LED should light for each combination of GND and V+ on A, B, and C

[acidblue]

[rich decibels]

On the second. The one with the LEDs...

[stolenfat]

this is what i had to do for my 4051 wacky sequencer...

pin->resister->led->output

just put the led in series. See if it that helps.

[Scott Stites]

This will work. R is the current limiting resistor for the LED (whatever value you are using). You only need one resistor. Make sure all the ground connections are made on the CD4051 (6, 7 and 8 ) - you don't want any input to float on CMOS. Ever.

Cheerios,
Scott

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[rich decibels]

Good idea stolenfat - I assume that would mess with the sound somewhat? In a good way, obviously...

[acidblue]

AHA! That works.
Thanks guy's.

[stolenfat]