Help with using CV to control pulse width

[TotemTek]

Hello, I am new here!

I've been checking out the pedals that you've all been making and I must say - beautiful ^_^

I just finished building my first effect pedal - it is a Pulse Width Modulator and it is working very nicely.

I have also built a baby 10 sequencer to sequence the pulse width of the pedal. The sequencer is working fine - LEDs are chasing and I am getting a pulse from the ground of the LEDs. The only problem I'm having is that I do not know how to connect the two!

This is the PWM pedal schematic. The 500k pot varies the pulse width - this is what i want to control with CV from the 4017:


Here is Baby 10, along with the 555 clock that is controlling it (works nicely):


Please forgive a n00b's worries, I have searched many places and found no answer, any advice in connecting the 4017 to that 500k PulseWidth pot would be massivley appreciated.
Thanks!

[slacker]

Welcome to the forum

If you use the "EZ LFO" mod from the original PWM schematic http://www.geocities.com/tpe123/folkurban/fuzz/snippets but replace the 40106 oscillator with the CV out of the Baby 10 that will control the pulse width.
The 10k pot will let you scale the voltage so it's in the correct range for the transistor. The 100uF cap will make the voltage slide from one step to the next, so if you want a more stepped response remove it, or add a switch to give both options.

Hope that helps

[TotemTek]

Yes, thank you, I will give it a jolly good go. Will get back to you.

Thanks!

[TotemTek]

ok, i recieved my parts today and i tried putting this thing together.

i built the lfo but tried to substitute the extra 40106 for the baby 10 up but i'm still having trouble. i don't fully understand how it works thus don't fully uinderstand how it should be connected. i'm guessing it's pretty straightforward but i can't figure it out. 

i've got a noise pulse everytime step one comes around but the 500k pot doesn't seem to be varying the pulse width at all.
any pointers for me? 

[Thomeeque]

This is weird, those ten diodes in parallel conecting CV out to the ground do not make any sense There should be no bullets on crossings of ground wire and all 10 anode-to-pot-center-tap wires. I'd say there's even error on original schematic, where is first diode grounded imo by mistake.

[frequencycentral]

This is weird, those ten diodes in parallel conecting CV out to the ground do not make any sense There should be no bullets on crossings of ground wire and all 10 anode-to-pot-center-tap wires. I'd say there's even error on original schematic, where is first diode grounded imo by mistake.

Well spotted, you definately right. The ten diodes are a mixer. I'ts a crude little sequencer, really there should be a unity gain buffer after each pot and then ten 100K resistors all going into one final unity gain buffer.

[TotemTek]

oh yeah! damn. that schematic is a copy i drew up aswell    i'll have to fix that. WHOOPS!!! thanks for pointing that one out.

unfortunately this isn't the cause of the problem i'm experiencing because i wasn't wiring up the diodes in this way. still slogging on trying to figure it out....

[TotemTek]

ok, say i had all the buffers for the sequencer sorted - how would i go about getting the CV out connected to the PWM pedal?

on the PWM i have the output1 (pin2) of the 40106 coming to the capacitor and then to the 500k pot back into input2 (pin 3) of the 40106.

apparently CV goes to pin 3, but how do i connect it to use the 500k pot as a variable for a single step in the sequence? - so that i can use 10 500k pots (one for each step, to control pulse width of that step).

i'm not understanding the need for the 100k potentiometers in the baby sequencer circuit so i've kinda left them out. 

[slacker]

Give me a few minutes and I'll dodge up a schematic that will work Hopefully it will be easier than explaining.

[slacker]

Here you go, hopefully it makes sense, if not I'll try and explain it. Join the 2 points marked with a red dot together. You'll probably need to play about with the 2 resistors before the transistor to get it working properly.



If you just what to sequence 10 500k pots without using the transistor you can do that but not with the parts you've got.

Can I have some sort of prize for the fastest ever pedal design 

[TotemTek]

Can I have some sort of prize for the fastest ever pedal design 

no! but you can have something out of gratitude for helping me 

that's fantastic that you drew that for me, thanks. i've had limited results with it so far, but i haven't tried different resitor values.

i've just stuck in 10k resistors which obviously are not quite right, but it has proven that i can get the circuit to work because for a little while i was having noticable pulse width changes on the first step! i'm not yet sure if the 100k pots will give me the full range of pusle width control either...

so, in it's current state it is barely stable, but tommorrow i'll have another go and see if i can nail it. if you remember any other tips you can fire my way in the meantime they are of course very welcome