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WIGGLING 'LITE' IN GUEST MODE

CMOS 40106B Square Oscillator Power Issue
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author CMOS 40106B Square Oscillator Power Issue
Tristana
Hello all,

I'm taking my first baby steps in making my own synth circuits.

Would somebody be able to explain to me why the circuit pictured works fine when powered by a 9V battery, but causes every module in my eurorack to freak out when I attempt to power it via the PSU?



The chip in the middle is a CD40106B arranged to the following schematic with a 10µF capacitor & 1kOhm resistor:
source: https://www.electronics-tutorials.ws/waveforms/generators.html

The remaining chip is just a TL072 set to be a unity gain / output buffer.

When running power via a ribbon cable from my Eurorack PSU to the breadboard, do I need something between it and the +/- rails?
JohnLRice
I'll comment mainly because I want to learn from the answers of people who really know what they are talking about Mr. Green but I'll guess that maybe your circuit is modulating the power supply and that you might need some decoupling capacitors? hmmm..... Read this article (or ignore it if I'm wrong hihi )
https://learn.sparkfun.com/tutorials/capacitors/application-examples

Also, a more detailed description of what happens besides "causes every module in my eurorack to freak out" would be helpful. cool I'm picturing all the modules jumping out of the rack, running around and screaming "OMG OMG OMG!!!" lol
Tristana
JohnLRice wrote:
Also, a more detailed description of what happens besides "causes every module in my eurorack to freak out" would be helpful. cool I'm picturing all the modules jumping out of the rack, running around and screaming "OMG OMG OMG!!!" lol


Actually what happened!

Nah, basically things like my wogglebug or penta would have their LEDs spontaneously light, the red LEDs on the Doepfer PSU3 would flicker. Didn't leave it in too long as I probably shouldn't have been using my expensive power supply connected to expensive modules as a testbed to begin with!
Tristana
Note that when it works, I have the 9v + connected to the + rail and the 9v - to the - rail.

When I attempted it with the eurorack power, I connected +12v to the + rail and -12v to the - rail.

Am I instead supposed to connect +12v to the + rail and GND to the - rail?
Grumble
Designing electronic equippement starts with reading datasheets.
http://www.ti.com/lit/ds/symlink/cd40106b.pdf
There you will see that the absolute max. voltage for VDD is 20 volt, so connecting it between +12 volt and -12 volt (makes 24 volt) is way beond its specs and will fry your chip in several seconds.
The schematics you provide however has the 40106 connected between +9 volt and ground, which is a safe voltage to work with (also handy if you want to power from a 9v battery.
But connecting the power between +12 volt and ground is still safe.
Tristana
Grumble wrote:
Designing electronic equippement starts with reading datasheets.
http://www.ti.com/lit/ds/symlink/cd40106b.pdf
There you will see that the absolute max. voltage for VDD is 20 volt, so connecting it between +12 volt and -12 volt (makes 24 volt) is way beond its specs and will fry your chip in several seconds.
The schematics you provide however has the 40106 connected between +9 volt and ground, which is a safe voltage to work with (also handy if you want to power from a 9v battery.
But connecting the power between +12 volt and ground is still safe.


Okay, oops... that was it! The chip somehow still seems fine even after the +12v, -12v connection (I think the PSU compensated for the power draw hence all the other modules going haywire?) and works as intended connected to +12v / gnd.
Grumble
Also it is common practice to put capacitors of around 100nF between power ( both + and - )and ground as close as possible to each chip you use.
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