Thanks Dc, but shifting seems a better option to muxing for digital.
In my case I'm currently using only 5 pins for up to 128 ins and outs (shared clock lines).

Thanks!

Hi,

I'm trying to save as many pins as possible and will be using the shift in (cd4021) and shift out (74hc595) tutorials for buttons and leds.

I'm wondering if it's possible to save acouple more pins by sharing the clock lines between shift registers and possibly the data lines. I'm guessing this should work if IN and OUT have separate latch pins but I'm far from my arduino so can't try it out yet.

Anybody tried this?
Thanks!

Thanks for your responses Johnwasser, Grumpy_Mike!

John, I did try reading on/off but still too much interference to get a reliable reading.

Grumpy, how slow of a response are we looking at? I can settle with a delay of up 1/4 second.

Thanks
Alex

Hi,
I'm designing a multi-touch panel using  39 pairs of 3mm IR led emitters + photo-transistors arranged as per this drawing:



It works perfectly in dust/dark situations but as expected - any ambient light turns it into a random generator 

I know the obvious solution would be to replace my cheap IR photo-transistors with proper IR modules and modulate the Leds @40khz...

But with 39 sensors, it isn't going to be cheap. I'm currently taking 3 readings at once using 3 4067 multiplexers so I'm wondering if I couldn't use an IR filter/demodulator circuit and simply multiplex the leds into that. it would save a ton of cash and soldering.
I was considering taking a sharp sensor's eyes out and multiplexing my leds into it's sockets but maybe there is a more elegant way to achieve this.
Is there maybe an IC that can do this? I know most IR modules output HIGH/LOW logic but an analog reading would be heavenly for eventual threshold calibration etc...

Many thanks in advance for your advice!

Thanks RG!

I will try some averaging and see how it goes.

Congrats on the 707, fantastic work I have to say!
Cheers!

Hi,
I'm building a midi controller with a couple dozen 10k linear pots using 2 4067 multiplexers.

 I'm currently using:

Code:

map(analogRead(0),0,1023,0,127)

Although stability isn't not terrible, I'm still getting +/-1 oscillations when some of the pots are in mid travel. Unnoticeable during performance but I real pain when the knobs fight each-other when the computer is in "learn" mode.

Midi CC only requires 7BIT resolution so I'm wondering if there is a way to lower the ADC's resolution to 7BIT since I'm trashing the resolution anyway with the Map function.

Thanks in advance for any insight.

Thanks, lefty
I'll have a search

Hi,
I have two pairs of 24pin chips that manage my car's fuel system in different ways - stock and performance.

I'm wondering if their is a reliable/simple way to switch between the 2 pairs electronically so I don't have to take my car apart to change the fuel management system.

I'm picturing a little pcb with the 4 chips and 2 outputs, with a switch to toggle between both modes.

48 relays is an option be feels overkill to me. i'm wondering if their is some kind of switching IC you could recommend.

Thanks!

Alex

Hi MarkT,

Thanks for your insight! I used a 10k trimpot to find the sensitivity "g spot" which turned out to be 3.4k in my case.

I did some thinking which lead to Plan B :


What if I used a 4067 to multiplex GND to each pair, one at a time, would that work?

I only have 3 analog pins left for IR but I can always multiplex the groups with another 4067 I guess...

Cheers

Hi!
I've been using the following schematic to use an IR Led and photo-detector transistor for my touch panel (sorry about the bad drawing):


This is a cheap alternative to proximity sensors and works great for finger detection on my Plexiglas panel.

Now I have a project that requires 42 "touch" areas and I'm trying to figure out the simplest way to multiplex them.
My plan (below) is to use shift registers to turn on each IR led one at a time, and take a reading from the respective photo-detectors:



would it be safe to hook all the transistors together or should I power them one at a time also?


I'm still an electronics novice and not sure whether photo-transistors consume power at all.
I don't mind soldering an extra bunch of shift registers if I have to, but I figured the experts might have a better plan to share

Again, sorry about the foggy explanation/schemo and many thanks for any insight!

Best
Alex

They are 20k as stated in my first post

Hi

I'm planning a synthesizer project using 5 atmega168 (4 voices and controller)

I'm curious to know if all 5 could share the same Crystal

Thanks!
Alex

Right now, with a 10k linear pot, analogRead gives me a range of 12 to 238. (I don't have other pots to play with) I'll stick with the standard 3 pin wiring and stop trying to cut corners  

Cheers!

Hi Lefty,

I was under the impression that enabling the pullup on analog pins would save the need to wire the pots to +5v.
By that logic I thought that a varying resistance between the analog pin and ground would be enough to get a proper reading.

I was obviously wrong
Best
Alex