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Electronics => Electronics => Topic started by: centralmax on April 16, 2012, 09:46:53 AM

Title: Axon II
Post by: centralmax on April 16, 2012, 09:46:53 AM

A newbee askes...  By using the analog I/O of the Axon II can you ude 2 push buttons 1 with a resister and 1 without on the same input to achive seperate signal?

Title: Re: Axon II
Post by: mstacho on April 16, 2012, 11:14:28 AM

3 signals, actually.  You'd want 0V to correspond to neither button being pressed, then when you push the right button, you turn the circuit on.

Otherwise yes, that should work.  A tad inefficient, though.  Why not just use 2 digitial IO pins?

MIKE

Title: Re: Axon II
Post by: centralmax on April 16, 2012, 01:31:49 PM

Thanks Mike.  My end game is to get as many inputs as possable out of the unit. I will probably need to find a way to link them so that I will get  about 100 in and 100 outputs.

Title: Re: Axon II
Post by: mstacho on April 16, 2012, 02:47:03 PM

For...what?  Haha 100in 100out is a lot...although definitely possible.  A MUCH easier solution is to just multiplex and read the inputs as fast as possible.  4051B multiplexer chips work astoundingly well and can be tied together.

MIKE

Title: Re: Axon II
Post by: Soeren on April 19, 2012, 06:10:51 PM

Hi,

Quote from: centralmax on April 16, 2012, 01:31:49 PM

My end game is to get as many inputs as possable out of the unit. I will probably need to find a way to link them so that I will get  about 100 in and 100 outputs.

A 100 inputs to a single A/D line is possible if the ambient temperature and relative humidity doesn't change by any noticeable amount and if you can keep noise completely away... IOW you'll probably have to settle for less.

The method is simple though, just make a resistive divider with one common resistor going to a stable reference voltage and let the switches connect a resistor to ground.
If you need to be be able to push more than one switch at a time, you'll need to either use "binary" values (like 1, 2, 4, 8, 16...etc) or values for an R2R ladder.
Either way, you need very precise (i.e. expensive) resistors and it will be much more expensive than just buying a microcontroller with eg. 100 pins and use that for expansion (a microcontroller is a few dollars - high precision resistors bought from a high street shop may come at a few dollars a piece).

A 100 outputs... Forget it, plain and simple.


What on earth do you need all that I/O for anyway?

Title: Re: Axon II
Post by: Admin on April 20, 2012, 02:03:18 AM

100 inputs and 100 outputs? :o

Quote

can you ude 2 push buttons 1 with a resister and 1 without on the same input to achive seperate signal?

Technically yes, but the microcontroller wouldn't know which button was being pushed . . .


You can get 100 outputs . . . you'd need to use several cross switch multiplexers in combination with the Axon.


Or . . . just use more than one Axon and have them communicate with each other using UART.