NXT multi I/O extension

[HaWe]

hey,
I'm curious if there is anybody (best of all in Europe) who would like to produce a soldered multi I/O board in a small series consisting of
2x PCF8574 (1x8 digital in, 1x8 digital out plus transistor motor output stage)
and
2x PCF8591 (2x4 analog in)

For power supply connected to a Lego battery box (6x 1,5V) we could have 1 i2c board not bigger than 10cm x 6cm with
8x touch sensor in
8x motor on/off
8x analog in

Plugs/connectors could be, e.g., in NXT style or - very cheap - in RCX style (similar to Mindsensors Rx muxers).

the PCF8574 part may look like this (courtesy of Bernhard http://www.mindstormsforum.de/viewtopic ... =30#p61317) :


The most expensive parts would be industrial etching boards,
and the price for everything altogether including workload could be far <80 EUR for selling.

I guess there will be lots of interested people to purchase something like that.

[mightor]

I am not so sure you can fit all that on a board that small, especially without knowing anything about what kind of motors you intend to attach to it. Those big transistors are, well, big and take up a fair bit of space. The NXT connectors are not exactly very small either. A single 8 channel AD converter chip would take up a lot less space. I've used the MAX127 in the past, but they're an expensive part and you don't really need that level of precision (12 bit). A single 16 channel IO expander, such as the TCA6416A may be more suitable as well. That still leaves you with 8 motor controllers that need a home. Some can control up to 2 motors, but that's still 4 chips that need to find a spot.

Perhaps if you put components on both sides of the board, you can make it work, but that takes a fair bit of skill to make it work.

= Xander

[HaWe]

yes, you're right, the estimated size was just the board without RCX style plugs, and maybe completely double-layer SMD
perhaps this board X 4 :


you can't get a max127 cheap at the next corner (as somebody already once had written), but the PCFs instead are available cheap and anywhere.
But if anyone has got them - why not?
The same it's about the TCA6416A you mentioned.

Motors are just (e.g.) 12-20VA DC motors, maybe even switchable by relais.

But anyway, of course I'm not the one who will be the hardware designer. I just got 1 small PCF8574 board of those and it's great, and it cries out for more :)