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Topic: 64 pots controller question (Read 2 times) previous topic - next topic

alan_m

Jun 16, 2011, 01:51 pm Last Edit: Jun 16, 2011, 03:25 pm by alan_m Reason: 1
Hi, this is my first post on this forum ..
i'm designing a 64 pots controller thats made from atmega328 and four 4067 multiplexers. The design is fairly simple, atmega will be populated with arduino code and output simple cc midi data thru serial midi. I've added leds for every potentiometer to show values via brightness.

I have to add that i'm not an educated electronician :) so if you could point out some mistakes, things that could be done better .. i would appreciate it very much.
I've attached my schematics and board layout.

thanks
michael


i'm not bored, i'm self improving

Magician

First, as leds have a threshould voltage, they will light up only when pot is set more than half.
Second, they would not light up at all with pot value more than a few k Ohm.

johnwasser

I think you are going to have some problems with the LEDs.  The brightness will not vary linearly across the range of the pot.  Try it with one pot to make sure the effect you get is what you want.  The loading of the LEDs may also cause the output voltage to be non-linear.

I hope the pots have a very high resistance since you have 64 of them in parallel between power and ground they will be drawing power.  If the pots are 1k the array would draw 320 milliamps just sitting around.  They should be at least 10k ohms.

You have through-hole components that are being soldered directly to the huge ground plane.  This makes soldering difficult because the ground plane acts as a heat sink.  You should provide thermal relief.  Read this: http://themaccabee.wordpress.com/2010/11/30/pcb-thermal-relief/
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alan_m

#3
Jun 16, 2011, 04:27 pm Last Edit: Jun 16, 2011, 04:54 pm by alan_m Reason: 1
i have already ordered 10k linear pots ..
what if i put a diode and resistor to lower the potentiometer resistance and make it kind of anti-log (like here http://sound.westhost.com/pots-f9.gif)?
will this help to light to leds?

thanks .. i will make termals for all components


thanks for reply
i'm not bored, i'm self improving

alan_m

something like this maybe?


i don't have the parts to test it yet .. is there a chance that this will do the trick?
i'm not bored, i'm self improving

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