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thepaddiscuile
Joined: Jul 11, 2007 Posts: 28 Location: ireland
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thepaddiscuile
Joined: Jul 11, 2007 Posts: 28 Location: ireland
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Posted: Thu Aug 22, 2019 7:04 am Post subject:
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Sorry I should mention that the chip used is a TL072 !!
I'm also using this.. |
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wackelpeter
Joined: May 05, 2013 Posts: 461 Location: germany
Audio files: 10
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Posted: Thu Aug 22, 2019 10:39 pm Post subject:
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Not having checked your schematic at all but a TL072 is naturally suitable for dual supplies. If you want to build an comparator on a single supply use an LM358 instead. Otherwise the TLC07X series are OPamps designed for single supply operation.
https://www.ti.com/lit/ds/symlink/tlc072-q1.pdf
As it seems you would want something like the CGS gate to trigger converter, then you should look up for the CGS24 schematics. _________________ https://soundcloud.com/bastian-j |
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ixtern
Joined: Jun 25, 2018 Posts: 145 Location: Poland
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thepaddiscuile
Joined: Jul 11, 2007 Posts: 28 Location: ireland
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Posted: Fri Aug 23, 2019 4:16 am Post subject:
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Thanks for the replies.. Yes I realize I can do it with a single supply chip but !!
To be honest I just didn't want to go down the road of buying more chips for a simple circuit.. I have 1 unused op-amp on a tl072 that I'm using for a drum circuit..
But If it can't be done then it can't be done !! |
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thepaddiscuile
Joined: Jul 11, 2007 Posts: 28 Location: ireland
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Posted: Fri Aug 23, 2019 4:21 am Post subject:
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ixtern wrote: |
Notice that on your circuit input there is a differentiating RC resulting in converting rectangle like positive pulses into positive and negative saw-like spikes. You may need to play with R and C input values to get proper output pulse |
Yes this doesn't matter too much, as I'm really just after a clean pulse in the 1-6ms range, this is then going to a pulse shaper circuit that lets me stretch or shorten the pulse to my tastes.. |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Fri Aug 23, 2019 4:53 am Post subject:
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although it might not be ideal a TL072 should work on a single supply. So I wonder, what is your input signal, does it go high AND low ?
otherwise you'd need a resistor to GND on the input (before the capacitor). Similarly are you checking the signal before or after the diode ?
If after you might again need to add a resistor to GND. Also what happens if you wire a potentiometer between +12V and GND and connect
that directly to pin 3 of the opamp, does it trigger the comparator when you turn the pot ? _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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thepaddiscuile
Joined: Jul 11, 2007 Posts: 28 Location: ireland
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Posted: Fri Aug 23, 2019 5:12 am Post subject:
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These are things I haven't tested... I haven't tried adding resistors to ground, Wonder what values they would need to be ?
And your right.. Im feeding it with a saw tooth from a dixie II modular oscillator which now that I think of it, would have half its cycle in the negative voltage range..The pwm from the dixie isn't short enough to give a pulse to use, its more of a narrow square.. As far as my ears tell, the saw gives a nice pulsey whack when the cycle starts.
How would one arrange a diode on the input to remove the negative swings ? |
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blue hell
Site Admin
Joined: Apr 03, 2004 Posts: 24079 Location: The Netherlands, Enschede
Audio files: 278
G2 patch files: 320
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Posted: Fri Aug 23, 2019 6:59 am Post subject:
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Triggering with a saw .. you mght have to change it from an upgoing saw to a downgoing one .. your circuit as is will will trigger on positive signals .. so the "fast bit" of the saw needs be upgoing.
The other thing is .. with a downgoing edge on the input you'll get a negative going spike on the input of the opamp which is outside its supply voltage range .. which may lock it up .. this can be solved with a diode fron the + input to ground to short out the negative pulses (its "arrow" pointing towards the input). _________________ Jan
also .. could someone please turn down the thermostat a bit.
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