Sizing a capacitor?

[Jamie]

serpa4 wrote:

Please, I need help. I just ran 12v straight to the fan and it ran on
high. No problems with interference. With that out of the way, I
decided to not put those magnet things on the motor wires. However, I
did put them on all the wires from the water/meth controller with no
luck. Its strange that the controller works fine when the fan is on
high and medium, but only interferes when the fan is on low.
1) Should I put capacitors on the fan motors? If so, what size, type,
etc.
2) What should I try next?
Thanks in advance for any help.

OK, I think I have it visualized as to what you're doing.

You have a PWM drive and it isn't connected directly to the
terminals of the motors ?
Assuming this is correct, in effect, you are radiating strong
EMF waves under the hood. Adjacent wiring is becoming an R.F.
receiving transformer and there for, influencing the lines of other
equipment.! Especially things that have low current sensor transmission
lines will mostly be whacked.

What you need to do is have the output of the PWM circuit pass through
an inductor circuit with a smoothing cap on the other side.

for proper size selection, knowing the carrier frequency of the
PWM circuit helps.




--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

 

[serpa4]

any improvement when run straight at 12v? whats different?

Identical.
is the fan air flow affecting anything? wire shake/air flow
elsewhere/sensors?
I've, through trouble shooting, have moved and tied down wires every
where in multiple places with no effect.
wish u were close enough, i'd come over and try to help.
Me to.
I need to see more details about how the fan speed control
mechanism is wired. Evidently it is the speed control that
is causing th noise, not the motors. The noise is probably
coming from the speed controller producing fast edged pulses
of 12 volts to the motors. The ferrite beads might work,
but they would have to be placed near the controller to
contain its noise. And it may help to put a capacitor
across the 12 volt supply lines feeding the controller, so
its pulses don't bleed back into the 12 volt distribution.
No, the beads didn't help. They are about ˝ inch or less from the
controller. I don't know how the controller works. Its in a sealed
metal box.
I still don't know what type or size capacitor to use. I'm clueless
on capacitors or what the actually even do.


OK, I think I have it visualized as to what you're doing.
You have a PWM drive and it isn't connected directly to the
terminals of the motors ?
I don't think so. There are several wires going into the controller.
Two are heavy wires (+ and -) from the battery to power the fans I'm
guessing. There is also one other +/- that I think is the PWM
contollers power source.

Assuming this is correct, in effect, you are radiating strong
EMF waves under the hood. Adjacent wiring is becoming an R.F.
receiving transformer and there for, influencing the lines of other
equipment.! Especially things that have low current sensor
transmission
lines will mostly be whacked.
I don't understand why this is only on low.
What you need to do is have the output of the PWM circuit pass
through
an inductor circuit with a smoothing cap on the other side.
I'm clueless about electronics. What you said just went way over my
head.
for proper size selection, knowing the carrier frequency of the
PWM circuit helps.
I have no Idea.
This is the manufacture:
http://www.spalusa.com/

 

[HapticZ]

i love this group, it's soo exciting!