the motor shaft will rotate as the motor input connected
to the de-energized relay would always see a positive
voltage and the other motor input would have a ground
path provided by the energized relay.
Thus, the mutual exclusive energizing of the relays
forces the relay contacts to act as a mechanical H-bridge. The direction of the motor shaft rotation is
dependent on which relay is energized.
THE COMPLETED SPACE DAY
After assembling and testing with a network of one
CAN node and the motor node, I assembled two more
CAN nodes, programmed them, and attached them to
the existing CAN network segment. I attached a Lenovo
NetBook to one of the CAN nodes and successfully
accessed the other pair of CAN node’s LED 1 and LED 2
resources. I was also able to blink LEDs on the CAN node
attached locally to the Lenovo NetBook via USB.
Controlling all of the motors on the motor node via the
network from the Lenovo NetBook was a success, as well.
With the help of some Velcro and a couple of wire
ties, I mounted the Lenovo NetBook, a USB cable, and
the CAN node on a 9” x 18” piece of 1/8 inch aluminum.
CONTACT THE AUTHOR
■ Fred Eady can be contacted via email at firstname.lastname@example.org
THE DESIGN CYCLE
■ PHOTO 3. Here’s what each student saw when they sat
down at their science stations. I had 196 touchy-feely
students pass through and use the trio of Lenovo NetBooks
for 20 minutes per session. The NetBooks toughed the
whole day out without a single malfunction or failure.
Five adhesive rubber feet on the underside of the a
luminum plate put the finishing touches on the science
station you see in Photo 3. Things are good and I’m off
Space Day was fantastic and the science station
performed beyond my expectations. Here’s more good
news. You can add Visual Basic interfacing and
MarshallSoft’s WSC4VB toolkit to your Design Cycle. NV
Order online at:
Development Tools for PIC® MCUs
microEngineering Labs, Inc.
Phone: (719) 520-5323
Fax: (719) 520-1867
Colorado Springs, CO 80960
With Accessories for $119.95:
July 2009 81