Does anyone know any circuits for filtering out noise from your power supply lines? I'm trying to clean up the 12vdc in my robot. It is powering a PC which introduces noise on the power lines. I hooked up an Oscope and there is a specifc frequency and ripple it introduces. Knowing this, is their a circuit I can use to filter this along with some formulas for figuring out the values of the components?
Thanks!!
-C
Dirty great big capacitor. In parallel.
Hehe. What do you consider big? I've tried the biggest polorized one I had which was 330uf I beleive, but I dind't see any difference on the scope.
-C
"Tom McEwan" wrote:
As big as you can get. Try 1000uF, bigger if you can get it. Adding more than one in parallel also and they'll add together.
-Dave
Does it make a difference if the cap is a polorized one or not?
-C
"Dave" wrote:
Only if you connect it backwards, in which case it will probably explode.
The best circuit for this is probably a pi filter. What sort of noise are you trying to filter out ?
this is made with 2 capacitors and one inductor.
supply +
No, but polarized capacitors (i.e. aluminum electrolytics) usually have greater capacity for a given size (space they take up).
-Dave
[Zagan] Others have suggested large electrolytics, which is a good suggestion for removing ripple, but perhaps what you're seeing on your scope is high frequency digital noise and electrolytics don't work well at such frequencies (for filtering out noise). Try putting a small ceramic (0.1 uF or so) capacitor across the power supply output (or input, or both) and see if that helps. If you still get low frequency ripple, then use an electrolytics as well on the output. The value you need depends on current draw, but 1000 uF or so should work.
// Jim
This is excellent info, thank you very much! I think I will experiemnt with combining this and the suggestion from Zagan (thanks Zagan!). I think these together should be able to at least help clean up my power source. It hasn't really caused me much of a problem yet, but I think I'm getting some slightly erratic readings from my ADC inputs. Everything on my robot is powered off a single large 12v battery. The motors don't seem to inject any noise, its the MiniPC that does it. I can see slight changes in the noise on the Oscope when the harddrive is doing stuff.
Again, Thanks!
-C
"Steve Vorres" wrote:
microprocessor.
C -
Oh dear, did you say the hard drive?
When the drive is being accessed (and depending on the drive vendor, just plain spinning), there could be significant amounts of radiation. It couples into everything through the ether. Caps out the wazoo may not help much. Perhaps you need geometry changes or shielding.
Just a thought, Bill
Good point. The PC I'm using is built like a laptop
-C
"Bill Turnip" wrote:
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