heavy load on power supply and lots of bleed? (+/- 12 volt power one supply)

[loss1234]

i am working on a project. it takes up TWO THREE OR four WIDTH BREADBOARDS (the big kind) and runs on a dual 12 volt (-/+ ) supply

now a lot of it is just testing different things to see how they work together

right now on there i have

a filter
2 4046 PLL's with dividers connected
a pseudo random circuit
a vca (13700)
an A/R gen
a audio to gate circuit
a lag circuit
a few buffers
and a few amplifiers (all tl072 oe 74)
and an F TO V Chip running into a VCO
a few tiny LFOS

NOW, when i try to take a voltmeter reading of my power supply when all of this is on, (its a 12volt power one dual supply .7a psu) i get a reading of only 10-10.5 volts!!

also, i am getting LOTS of bleed problems. like if i listen to JUST the PLL output or JUST the vco output, i can STILL hear the clean guitar bleeding through the signal (like its coming through my ground return or something)

any suggestions?  i DO have 104 and 10uf caps at random places all along the boards going from + to gnd and from gnd to -v

any help appreciated

thanks

[frequencycentral]

Hey loss is that my A/R gen?

Try a 22uf (10uf should do) cap and a 0.1 uf cap across the power rails where the power enters each and every seperate circuit. That would be one of each from +ve to ground, and one of each between -ve and ground. This is called 'decoupling', 'randomly placed' isnt really good enough. Thats how it would be done on a modular synth, which is basically what you have there. That should sort the bleed.

Also, it sounds like you may need to increase the ma of your power supply. Why not do the caps thing and then see how many of the circuits you can successfully run before you run into problems?

Any unused cmos should be tied to ground. Also, if you have 555's in there you may have crowbarring of the supply going on.

It sounds fascinating by the way.

[R.G.]

Mother Nature is trying to teach you about power distribution issues in larger systems.

Breadboards are NOT good ways to hook up ground to larger (more than a handful of ICs) systems. Star grounding and star distribution might help, as might putting a 10uF/0.1uf at every IC power point. Maybe.

[loss1234]

thanks guys


I do have SOME non random decoupling but you are right, i should add it to each circuit. Now i DID have a 555 based circuit in there but i tore it out as it caused weird bleed in everything.

RG- so how are we supposed to test gigantic circuits if breadboards are a power nightmare??

one of the things that worries me about working on a big project is this.

if you have LOTS of circuits you need to test TOGETHER but they arent done enough yet to solder or pcb, but on breadboard they act all weird, then how are you ever supposed to develop things to work for PCB?

its the chicken or the egg problem. i cant get decent testing on a breadboard but i cant put things on pcb until they are well tested. ahhhh

i suppose i should try star power
maybe even try powering the cmos off of batteries for now.

i will start tying all unused cmos to gnd too. that was one i got lazy on.

also i found earlier today that when i put i reduced the gain of my input opamp (which was super super high in order to provide a square wave to the 4046) it helped with noise but hurt my tracking. so i think i need to rethink my tracking side of the circuit.


sorry, right now i am using Ian fritzs A/R, A/D gen.


thanks.. i have a lot of things to figure out.

especially if this is ever going to get put in a rackmount (which is the plan)


btw, i have many power setups for my moduar that work fine. there is a slight chance the power one supply i bought used has some loading issues which was why i was asking how much load a psu like that should be able to handle before the voltage starts dropping. it was sold as is so....

but if its natural for volts to start dropping as you start reaching the maximum amps of a psu then its probrably fine.

how can i test the amount of amps my circuit is trying to use?

thanks

[slacker]

btw, i have many power setups for my moduar that work fine. there is a slight chance the power one supply i bought used has some loading issues which was why i was asking how much load a psu like that should be able to handle before the voltage starts dropping. it was sold as is so....

I would think the power supply should be able to supply the correct voltage up to the current draw it's rated for. So yours should be able to supply 12volts at 700ma, that might be the total current it can supply though so it might be 350ma for +12 and 350ma for -12.

how can i test the amount of amps my circuit is trying to use?

The easiest way to do this is to put a 1 ohm resistor in series between the power supply and the circuit. If you then measure the voltage drop across the resistor that will give you the current draw. If you haven't got any 1 ohm resistors just use the smallest value you have and then use Ohms law to find the current draw.