REVIVING AN ANDROBOT BOB: Part 2
or any circuits taking power from the
Handy Board itself. Power for the Handy
Board, expansion board, Sonar Multiplex
board, and encoders all come from a
commercial DC/DC converter module in
a nice compact DIP- 24 pin format. These
are available from several manufacturers
(CINCON, AZTEC, etc.) with a variety of
options for input and output voltage. The
advantage of using a module like this is
that they are usually very efficient (80%-
90% range), have built-in short circuit
protection, and have good regulation.
The one used for this robot
accepts 18V-36V in and puts out a
steady 5V. It made more sense to go
this route instead of spending a lot
of time designing an entire power
supply. This DC/DC converter gets
power as soon as the main 24V from
the batteries are switched on.
The custom power supply module
takes both 12V and 24V into the board.
The 12V runs through four 1N5401
diodes in series to provide approximately 9V out for the audio amp and SX48
co-processor board. It also feeds a 6V
Labels for power board.
voltage regulator for a dedicated 6V out
used specifically for the Polaroid sonar
ranger. The 24V power in will be available to check the overall system voltage
and is used to power a relay that the
Handy Board can control to switch on
and off a 12V supply to power some
device (like a vacuum) later on.
The voltages that are available
when the robot is switched on (12V, 9V,
6V, etc.) are each brought out to a barrier strip. This helps keep the wiring neat
and allows for easy changes later on.
Running all those sonar
Instead of installing a Polaroid sonar
ranging board for each sonar transducer
(five boards), it made more sense to just
use a single board and then add some
additional circuitry to allow it to
drive each one of the five transducers.
A proven way to do this is to use
small relays to switch the appropriate
transducer in circuit. It is important that
there is always one transducer selected
Schematic of custom
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