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### Topic: Steadying a 12V input signal (Measurements included) (Read 461 times)previous topic - next topic

#### n3v3r5um3r

#15
##### Feb 20, 2020, 03:35 pm
You should beable to get that witha 470 ohm
resistor (12V/0.020A= 600 ohms)
Ahh I see, so I also need to consider the optocoupler's limits when sizing the RC filter.  Thanks for that.

OK, so if I use a 470 ohm resistor and want to maintain the cut-off frequency of 100 Hz then I would need a 3.9 uF capacitor.  It happens I actually have a 3.3 uF electrolytic capacitor so I think that will work.

#### n3v3r5um3r

#16
##### Mar 10, 2020, 07:34 pm
You should beable to get that witha 470 ohm
resistor (12V/0.020A= 600 ohms)
Cleaning the signal up electronically could be done with an electrolytic capacitor at the 12V signal input.
To close the loop an RC filter ended up working for me.  I needed a 470 ohm resistor and a 47 uF capacitor to properly filter.  Thank you all for the assistance.

#### TomGeorge

#17
##### Mar 11, 2020, 10:51 amLast Edit: Mar 11, 2020, 10:53 am by TomGeorge
Correct, tapping off the +12V supply to the lamp.

Not much from what I understand; enough to drive an optocoupler drawing at most 20mA.
What lamp?
What is the lamps function.
What vehicle, does it have a Canbus system?

Hows about a circuit diagram of all the components between the lamp and the Arduino?
What Arduino are you using?

A 14V to 0V PWM is not on the battery voltage line, if it was everything on the vehicle would malfunction.
Where EXACTLY is the point you are getting the 12V that you are sensing  and for what reason are you sensing?

Tom...
Everything runs on smoke, let the smoke out, it stops running....

#### n3v3r5um3r

#18
##### Mar 16, 2020, 05:02 pmLast Edit: Mar 16, 2020, 05:05 pm by n3v3r5um3r Reason: Link added
What lamp?
What is the lamps function.
What vehicle, does it have a Canbus system?

Hows about a circuit diagram of all the components between the lamp and the Arduino?
What Arduino are you using?

A 14V to 0V PWM is not on the battery voltage line, if it was everything on the vehicle would malfunction.
Where EXACTLY is the point you are getting the 12V that you are sensing  and for what reason are you sensing?

Tom...
Hi Tom - Here's a video showing the completed project now that it's all working: Focus RS Arduino LED Reflector Project

I didn't want to get into too many details in this thread to prevent topic drift as the scope was simply to steady the fluctuations in the ~12V signal I was monitoring.

If others come across the a similar issue as my first post I hope they can try looking into RC filter.

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