I have the original assembled logic board, analog, how many pots,
sliders, etc, could I attach?  I ordered one touch strip and was
thinking 2 knob pots, is this possible?


Meoff

Could I use Guitar pots?

Yo, just saw the info posted, duh!!!!

"use a low-ish resistance potentiometer, like 1k or 5k"

How about the sliders? Could I use a 10k?  I found some sweeet Alps 
sliders on ebay, but they are 10k!

10k is fine.  a pot is a pot whether it's a slider or a knob.

Is there a limit on resistance, I am new at this!? So if 10k is fine, is 
50k cool too? What are my limitations?  I found a lot of cool shit on 
ebay and would love to incorporate some added knobs, etc.

Tonedeft, thanks for your response!


Meoff

no problem, I do this stuff for a living, nice to put it to good use. ;)


checking the atmega32 spec sheet:
http://www.atmel.com/dyn/resources/prod_documents/doc2503.pdf
page 287, looks like the input leakage current is 1uA meaning that's the 
minimum amount of current the input pins need (I think, I'd have to read 
more but it sounds about right.)

so, there's ohms law (check wikipedia) it's the bread and butter of 
electronics

voltage = current * resistance

v = i*r

v=5V
i=1uA (1 microamp, .000001 amps)
r = v / i = 5 / .000001 = 5,000,000 = 5 Megaohms

you're not going to find a pot advertised for human interface in the 
mega ohm range, they'll all be 1kOhm to 100kOhm, so any pot will 
probably work.

as always, unless you're risking blowing something up, just try it out, 
that beats pencil exercises anytime.

You da man!!! Thanks for the info, I plan on teaching myself as much as 
possible, so I can trick out my house, car, studio, etc...So any good 
info would be awesome!!!

Meoff

my understanding (from the wisdom of an animatronics guy i worked for in 
LA) is that the low resistance is good for noise reduction? i forgot the 
exact rationalization.

i'd also suggest plugging it in and trying it out. nothing's going to 
explode.

low resistance means lower noise because resistors are inherently noisy, 
heat is generated when current passes through them, the heat jiggles the 
stuff inside the resistor around, the jiggling produces noise.  in 
general thermal noise is
proportional to the square root of the bandwidth (negligible in our 
case) and the square root of resistance, as well as the square root of 
temperature.

so, to reduce noise, lower the resistance, narrow the bandwidth or lower 
the temperature.

could this be why I'm getting really crappy signal off a 10k fader?

I guess I will get a lower rated pot and test that out.

nah, the magnitude of the noise would be in the microvolt range (guess). 
the noise you're seeing it much more likely due to the wires going to 
the pot picking up noise from electronics around you, like an antenna. 
putting a well grounded piece of metal around/under/near the wires going 
to the pot should help shield it.  also, shortening the wires would help 
too.

there could also be noise in the ground and 5V on the board itself.  now 
that I think about it, the button board itself is a big antenna hanging 
off the logic board.  look at your 40h, in your mind visualise the path 
the 5V and ground wires take from the USB port, to the logic board, onto 
the ribbon cables and around the button board, they travel quite a way 
as just wires in space (the PCB does little in this case than hold the 
wires in a form.)

the kit's not completely optimally designed for noise immunity, but that 
would definitely add cost and complexity to the kit beyond what's 
necessary for a working device.

encoders will be much quieter to use, and they're endless.  I'll hit you 
up tomorrow LJ.

*HI 5*

:)

hey guys! check these out!, any good? I know ALPS is good shit!

http://cgi.ebay.com/ALPS-10K-4-GANG-AUDIOPHILE-SLIDER-POTENTIOMETERS-MIXER_W0QQitemZ7606818367QQihZ017QQcategoryZ58164QQrdZ1QQssPageNameZWD1VQQcmdZViewItem#ebayphotohosting

If a pot is a pot, then could I use some spare parts from my DJ mixers? 
(Assuming that they are not in the 500k range) For example, I was 
thinking of using a line level fader. (They're Penny&Giles faders)

Meoff

yep.

i have a whole gang of alps sliders i bought at an electronics surplus 
place thats going out of business. i was hoping to use them with an 
arduino project but i think the whole 5-10K rule applies with arduino 
too and these guys are 200K kind of a bummer cause these feel really 
nice.

did you hit c&h before it died? man, i was sad when i found out, last 
time we were there in LA.

yeah its still gasping actually… barely anything left there. i may go by 
there looking for cases today. its one of those places that will be 
"going out of business" until its shelves are empty.