CV control of MB-808 swing

MIDIbox SEQ
1

So I’m planning to add CV control of the Swing amount on my MB-808 by simply adding a summing stage after the Swing pot. I’m wondering about how well the core will handle >+5v at the input though. Will it be ok if it gets hit with +10v or do I need to limit the output of my summing stage to 5v?

Thanks!

epk

2

ouch… 10v directly connected to pic-pins, never a good idea…should be limited in some way to avoid burning your pic…

3

I’m still pretty new to working directly with PIC’s and microcontrollers in general, so this is good info to know! Now I get to learn how to limit an opamp’s output voltage!

Thanks!

epk

4

http://www.ucapps.de…o_schematic.pdf

here in the Interface and protection unit part schematic you can see how to limit an opamp’s output voltage

5

cool schematic! although I haven’t yet been able to understand exactly how it’s accomplishing the limiting.

I ended up using two inverting opamps to do the summing, then adding a 1N4148 reverse polarity after the first opamp to limit it’s output to negative voltages, then added a 4.7v zener diode (reverse polarity) on the output of the 2nd stage to limit the range to 4.7v and this seems to be working.