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Topic: Put some analog Meters + dimming LEDs on an Arduino Mini (Read 474 times) previous topic - next topic

optikfluffel

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 :)

MarkT

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.
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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)

majenko


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.

optikfluffel

So just something like this ?
Code: [Select]

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

MarkT

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
[ I won't respond to messages, use the forum please ]

optikfluffel

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

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