Basic Controller inquiry

[Hlias]

Hello everyone,

I want to make an array of 20x20 electrodes (a pcb with a matrix of 20x20
terminals) and I would like to be able to control each one of them
separately through a computer.

How would I do that, what type of controller should i use?

Thank you in advance.

 

[blueroomelectronics]

A microcontroller

 

[Hlias]

Thanks Bill,

Could you suggest any specific type of microcontroller?

 

[Hlias]

I would like to be able to control (ideally) independently each one of the 400 electrodes at the ends and furthermore be able to vary the voltage to each of them (meaning to be able to have more than just 2 values say 0-5V). Would I be able to do that with a microcontroller?

 

[blueroomelectronics]

A microcontroller and lots of DACs it's not going to be cheap. Also depends on how many levels you want at each pin. If you've not worked with electronics you're probably going to have to contract out such a design.

 

[Hlias]

In case I compromise with having only to states (H-L 0-5V) would I be able otherwise to control each of the 400 pins separately, only with one microcontroller?

Thank you in advance Bill.

 

[blueroomelectronics]

No single microcontroller has 400 I/O pins (I could be wrong) but you would be able to use 50 8bit latch ICs plus almost any microcontroller. What sort of current to you need at each pin?

 

[crutschow]

In case I compromise with having only to states (H-L 0-5V) would I be able otherwise to control each of the 400 pins separately, only with one microcontroller?

One way would be to have a long series of shift registers to give 400 bits with parallel ouputs, one output to each pin. The desired 400 bit pattern is then serially input into the shift register. It would require 50 bytes of information serially out from the microcontroller, which should be fairly simple to program.

 

[Hlias]

the current i will be needing for each pin will be between 10-20 mA. Not more than that.

 

[blueroomelectronics]

That's fine just check the latches datasheet for current source & sink. Many logic latches can sink far more than they can source. Still not a cheap project by any means, the PCB will be fairly large. How fast do you need to change the state of any given pin?

 

[Hlias]

To give you an idea the electrodes will be 1.5mm diameter-gold plated and I would also like to be able to control this through bluetooth. Would this be possible?

 

[blueroomelectronics]

Anything is possible, bluetooth has a serial port mode so that's ok. How fast do you need to control the pins? Are you going get a contractor to design, build and test it or do it yourself?

 

[Hlias]

The truth is that I would like to do the project myself. I know it is going to be difficult as I haven't dealed with electronics for some years now, but i think im gonna give it a shot.
Is there any particular microcontroller that you could suggest?

 

[Hlias]

I would also like to know whether it would be any more useful to use a microprocessor instead.

 

[Nigel Goodwin]

I would also like to know whether it would be any more useful to use a microprocessor instead.

I would suggest using a suitably sized PIC, as they are the most popular, and have the most support available.

No point using a microprocessor, just making it far more complicated and adding nothing.

 

[Hlias]

Thanks Nigel. Is there any particular PIC that you could suggest?

 

[Nigel Goodwin]

A lot depends what you want, 16F series are nice, but if you want to use C then go for an 18F device, as there's a free C compiler for the 18F.

You might consider Bill's Junebug programmer and project board.