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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Digital Pot triangle wave generator
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mike page



Joined: Sep 26, 2016
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Location: norwich, uk

PostPosted: Sat Nov 24, 2018 10:53 am    Post subject: Digital Pot triangle wave generator Reply with quote  Mark this post and the followings unread

maybe one of these: https://www.analog.com/media/en/technical-documentation/data-sheets/AD5220.pdf

driven by a 4060 with the /by 256 toggling the up/down

then just use it as a voltage divider.

not sure if they can go fast enough for audio rate though...
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Grumble



Joined: Nov 23, 2015
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PostPosted: Sat Nov 24, 2018 1:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Fastest clock frequency is 20MHz, so it will take about 13usec to go from 0 to 256 that is about 77kHz.
So clocking is no problem, if the wiper will follow with this clockspeed depends (also) on the resistance of the digital pot, where lower values are the fastest.
I guess you have to try.
By feeding the A input with a buffered AD or ADSR signal, you don’t need a VCA, although I suspect bleeding of the clock signal when the ADSR is at 0 volt.

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mike page



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Location: norwich, uk

PostPosted: Sat Nov 24, 2018 1:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Grumble wrote:

By feeding the A input with a buffered AD or ADSR signal, you don’t need a VCA, although I suspect bleeding of the clock signal when the ADSR is at 0 volt.


Good point!

would be interested to chuck some other junk at the up/down pin to get different waveshapes
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Grumble



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PostPosted: Sat Nov 24, 2018 2:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Set the up/down input to up and keep counting, you get a saw shape, set it to down and you have a backwards saw.
Ow, just noticed 128 steps Rolling Eyes

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piedwagtail



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PostPosted: Mon Nov 26, 2018 3:07 am    Post subject: Reply with quote  Mark this post and the followings unread

off the top of my head(as usual)

This looks like part of an interesting pitch quantizer with a paralleled gating system to cut out increments.

R
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Grumble



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PostPosted: Mon Nov 26, 2018 3:28 am    Post subject: Reply with quote  Mark this post and the followings unread

This one only counts up or down, not good for quantising
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piedwagtail



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PostPosted: Mon Nov 26, 2018 5:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, stick various pulses into clk and direction, in any relationship. Then use another pulse to sample and hold the output of W. Use A and B to figure range. Lunetta to pitch CV.

I'm pointing to a composition device using pulses rather than your or the OPs conception of using it directly as a wave provider.

Farnell seem to have the best prices, especially for SOICs.
For Moonbase, there's the AD5222.

R
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PHOBoS



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PostPosted: Mon Nov 26, 2018 10:19 am    Post subject: Reply with quote  Mark this post and the followings unread

oh interesting, I didn't realize it has the counter built in untill I checked the datasheet.

piedwagtail wrote:
For Moonbase, there's the AD5222.

hmm, NANDulators connected to the inputs, 'pots' connected to a NANDulator ? Twisted Evil

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piedwagtail



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PostPosted: Mon Nov 26, 2018 11:15 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
oh interesting, I didn't realize it has the counter built in until I checked the datasheet

Yes, Mike seems to have brought to our attention to a very interesting device.
I look forward to seeing where both the waveshaping and compositional routes can take us.

R
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Grumble



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PostPosted: Mon Nov 26, 2018 12:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Carefull with lunetta or nandulator, since the absolute max voltage for this device is 7 volts.
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