Remote delayed 12 channel switch

[artyvesna]

Hi.
Given:
- a control box containing:
--- an Arduino based controller with N-Mosfet switch
--- a "switching" PSU 3amp/3.0V regulated
- 1.5 meter 2x 22AWG wire unshielded
- process chamber containing a fixture/jig with 12 nests equiped with spring loaded contacts for power supply aka. ICT fixture
- 12 items:
--- normally powered by 2x 1.5V batteries (equipped with electronic "pump")
--- max current draw of each is ~250 mA in short (ms) spikes, constant mean is around 70 mA

Problem description:
  Operator loads products in their nests on the fixture and into the process chamber, presses a start button.
MCU then starts a sequence and at some point activates a MOSFET(irlz44n) which commutes ground to 1.5 meter wire,
which in turn is connected to the fixture where at the moment all the nests are connected in parallel.
As you can probably see, all units get powered simultaneously and that is a problem.
Beside of voltage drop at ~2V on the common wire, these items initiate a radio comm -
simultaneously, on the same channel. This is undesirable.
  Now, while i admit that the whole design is quite amateur, but this is another discussion.

Possible solution:
  Implement some very compact simple control unit(?) in tandem with some transistor array (like TC7320FG-G M931), to realise
sequential/delayed power switching to each of the nests. The whole assembly must fit into a tiny (~ 30 x 50...70 x 10 mm)
confined space, meaning almost no heat dissipation.

I would appreciate your suggestions.

[SL4P]

First suggestion, maybe to pitch this in the Arduino forum.
http://forum.arduino.cc/
They are more targeted at programming solutions for Arduino.

Second suggestion would be to express the problem in technical English, rather than nests, pumps and ...
if you can have a clearly awn black dagram to communicate your ideas - a wiring/circuit schematic can come later.

Define the problem first, before you start throwing specific parts at it.
What you have may be suitable, but find the goal fi st, before visiting Radio Shack.

(I’ll be over at arduino.cc to help when you get there.)