Combination

[Frodo Baggins]

Hello,

I am limited with 8 inputs on a speedyboard,am I able to make a combination with these inouts(inorder to be able to "increase" the "limited" amount of inputs"?[Each input takes true or false]

Thanks in advanced. 

[RTSLVU]

I am guessing your "speedyboard" in an 8bit digital I/O?

Right off the top of my head I would say you could design some external circuitry to multiplex the single port.

Now you would have to give up two data lines and use them as address lines and one as a R/W line

Then using bidirectional three state latches expand it out to 20bits of I/O.

You might want to look into Measurement Computing's USB DIO products. They have a 24bit (3x8bit) USB DIO for $99

Message Edited by RTSLVU on 12-24-2009 11:12 AM

[Frodo Baggins]

 I have speedy-33 which has 8 analog inputs(switches) and 8 analog outputs(LEDs), so what is the name of the  product we could add to increase the number of inputs and outputs.Does National Instruments have such a product?

If they don't,do you know any link that will  explain and clarify the steps that you stated ?

 Thank you very much 

[Frodo Baggins]

"Faithless is he that says farewell when the road darkens."   --  J.R.R. Tolkien

[Stefo]

Hi Frodo 😄

As mentioned by RTSLVU, it is possible to extend number of inputs to more than , if you use multiplexer (it is switch which has one input and multiple outputs). If you are looking strongly for NI MUX, you can find them under switches (NI Products & Services -> Modular Instruments -> Switches), but I'm strongly convinced that for your application this approach is like bring elephant to move a needle.

Way cheeper and more practical solution (as I believe you are student working on project) would be to use just one external chip as was mentioned before. You can just google for multiplexor and you can find many manufacturers. Example can be Analog Switches and Multiplexers from Maxim-IC.

Anyway, I don't believe this should be your, nor anyones approach. If you need to have more inputs, than rather than "creating your own circuit", you should exactly specify how many I/Os do you need, how fast schoudl they measure and what schould they measure, and then choose the right products. You will save a lot of effort and time to yourself by searching manuals and writing to the forums

When it's clear what you really need, I recomend to visit www.ni.com/dataacquisition and search the right device for you. You can find many interesting products for reasonable price.

Regards,

Stefo