 # Put some analog Meters + dimming LEDs on an Arduino Mini

Hi :) I want to build a little CPU/RAM/etc. meter with 6x 1mA ammeters and want them to be lightened up with a little LED per meter that only shines a little if the meter is around 0% and then get's brighter and brighter according to the meter. Is that possible with the 6 PWM outputs from the Arduino? How do I have to solder that together?

Thank you :)

Since mechanical galvonometers (that's the precise word for the analog ammeters you mean) have a mechanical mass they automatically low-pass-filter a PWM signal nicely. You just need to limit current appropriately. For a 1mA FSD (full scale deflection) you want a total of 5k resistance from a 5V PWM signal. The meter itself will have a resistance of a few hundred ohms or so (this should be in the specs), so try a 4k7 resistor in series.

yes my meters have 410? ^^ but I don't understand/know how to hook the LEDs to that and let them dim =/ (sorry for being such a n00b xD)

optikfluffel: yes my meters have 410? ^^ but I don't understand/know how to hook the LEDs to that and let them dim =/ (sorry for being such a n00b xD)

LED+resistor in parallel with the meter+resistor.

So just something like this ?

``````               /----(Resistor)--(LED)------\
Arduino PWM --:                             :-- Ground
\----(Resistor)--(Meter)----/
``````

Yup, perfect - make sure the resistor for the LED limits the current to 10mA or less or the output voltage to the meter will droop (or use a different pin and drive the LED upto 25mA. The pin output transistors have a finite resistance around 30 to 40 ohms when running from 5V

Thank you so much :) One (hopefully last) more question: Does a 0,6W 0.1% resistor do it?