Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Power Supply Output Crosstalk?

Status
Not open for further replies.

Ventura

Member
I’ve just assembled a 30-watt, 12VDC-output power supply to power a few home security cameras (two with IR emitters) and a small microphone pre-amp, but I haven’t installed it yet. The heart of the unit is a “Power-One” BLP30 switching p/s with the output wired to a nearby “distribution block”…a small enclosure box with six DC coaxial plug connectors on top, wired in parallel. I mounted a small, low-power “Silenx” cooling fan just above the switcher, powered by the power supply’s own output. As this puts the fan in parallel with the cameras and pre-amp, I’m wondering if the fan’s motor might introduce noise into the system’s output, and especially what effect that might have on the sensitive audio pre-amp. In fact I wonder about the cumulative effect of all of the devices being wired to the same 12-volt source.
Might something along the lines of putting a small ceramic disc capacitor across the terminals of each of the six output connectors help filter at least some noise in the system, should there be any? And, if this is the way to go, I don’t know what capacitance would be appropriate.
Any thoughts?

Thanks
 
Yes other things connected to the power supply can interfere and induce noise.

I would imagine your microphone already has noise suppression in the pre amp circuit but it certainly wouldn't hurt to place a small value ceramic capacitor (0.01 - 0.1 uF) across each output from your distribution block to prevent high-frequency noise from your fan.

Actually the capacitor would be better off placed as close to preamp as possible.
 
Any device placed more than a short distance from a switch mode DC power supply is going to require filter caps to avoid noise, just about every piece of PC hardware has filter caps on the device itself and those leads are only 10-18 inches long.
 
Last edited:
Thanks, guys, for confirming my suspicion. This is my first venture into working with a switching power supply, and then powering several devices from that single source. I'm alright when building things from schematics, but my electronics engineering skills are limited.
Is it correct to say that the choice of value for this sort of filter capacitor depends on the frequency and amplitude of the noise in the circuit?...and that there could only be an "optimum" value if the noise was known to be fixed at a particular frequency and amplitude?
I really should try to find an article on this; I know it's pretty basic stuff, and useful to know.

Thanks again.
 
I wouldn't over think filter caps too much, you could optimally calculate a value, but it doesn't need to be that complicated.. A single low ESR electrolytic would probably work quiet well 1-10u, maybe a second with better higher frequency response, often the quick slam on a low ESR electrolytic will solve any possible problems, depends on how low noise you need to go.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top