Logged in users > User Diaries
Noise on a 12V DC circuit.
tanner0441:
Hi
I found that a 12V LED strip light with touch on/off wouldn't light when I wired it over my solar controll board. Removed it took it into the house and tried it on a seperate battery, perfect on off repeatedly every time I poked the touch pad.
So armed with a portable scope i went hunting. Didn't have to look far, right at the battery terminals superimposed on the 12V the was 5V AC spikes. 5V peak to peak and ringing for 10 micro seconds. switched the panels off still there. I have two controllers a MPPT with 750 W of solar and a PWM with 60W which will eventually moved to another building.
At this point I ran out ot time so had to shelve the hunt. But I think my easiest option is to build a little 5A common mode filter I have plenty of toroids that are suitable. Just a bit annoying that three 12V batteries in parallel (with buss bars) are not low enough impedance to keep the cr#p from a charge controller out of the connected circuits. I spent a lot of my working life keeping RF and pulse signals off DC PCB tracks.
Anyone else encountered this?
Brian
joestue:
I doubt this is a common mode problem.
tanner0441:
Hi
I haven't had time to get right into it. I know what the transients look like I know the duration of them but not the frequency they occure. They are not from the MPPT controller that produces hash on the output leads around 100 khz and very low level, so I am assuming the big spikes are from the PWM controller. This is a pulse with ringing. the best way I can describe it is like the primary patern on a car ignition system when the points open.
I thought common mode filtering because it is a symetrical patern and they are easy to make and I can put one in the lead from the controller and the battery. I used to build LISN filters for cleaning mains supplies for measuring complience in RF circuits and preventing the RF getting back up the mains leads, but it is easy when you know what frequencies you are dealing with.
As a PS cordless oscilloscopes are like cordless power tools the batteries go flat right in the middle of a job.
Brian
Mary B:
A simple .01mfd ceramic disc capacitor across +- might cure the problem. And is cheap. May be a sign your charge controller has something failing...
OperaHouse:
That is why I save the inductors out of old computer power supplies, designed with a nice lossy core. I just got one of these and I love it. Less than $29 shipped with taxes and that is with the deluxe test lead package. Love I can take it anywhere.
Navigation
[0] Message Index
[#] Next page
Go to full version