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 Robotics / RCX / 1440
1439  |  1441
Subject: 
RFC: Mux schematic viability
Newsgroups: 
lugnet.robotics.rcx
Date: 
Mon, 1 Oct 2001 13:57:16 GMT
Viewed: 
1742 times
  
    If anyone with electronics experience has a moment or two, I would be very
grateful if they could take a look at
http://www.starforge.demon.co.uk/images/mux.png This is a design based on the
4017/4066 multiplexer on Michael Gasperi's website except that I want to
use BAT85 diodes rather than 1N4148s and the 4017 switches three 4066s: one
like in the existing design and two to provide multiplexing for the other two
sensor lines. I've added some LEDs for diagnostics,they take power from the 9v
external supply.

Does this scheme look workable? Should I provide a bank of dip switches to
allow unused input lines to be tied to their respective gnd via a 2.2k
resistor, or can I leave them floating? (I can modify the schematic to show
what I mean if this is not clear) I think I need some 0.01uF capacitors to
decouple the 4066s but I've left them off the diagram for simplicity.

I should point out that I have modified my RCX1.5 so that it has an external 9v
power supply (I use a regulated PSU capable of supplying 9v at 1.2A) and the 9v
supply referred to on the schematic is taken from that there. I have mounted a
2x4 electric plate on the top of the RCX, connected it to the battery
connectors inside the RCX via wires threaded through the two small holes in the
top of the case at the back and the power is connected through a 9v wire cut in
half with a standard power socket at the end (I will post full pictures and
explanation to my website shortly).

My apologies if I've made any glaring errors in the circuit, I'm a programmer
by nature and trade and most of my electronics experience is digital logic gate
related stuff (processor design and the like) - this "real life" electronics is
proving a bit more of a challenge to get right! :))))



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