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GAN142
Reduce Motor Noise
By Michael
Simpson
In the past when I built a Bot I would just slap it
together and hope for the best. However when I started to use RC
receivers to aid in the control of my bots the results left a lot to be
desired.
After some research and and experiments here is what I have
come up with.
Action 1 Motor Suppression Capacitors
This is a black art. There are as many opinions on
how to connect capacitors to motors as there are motors.
However one method seems to be the most popular. This is the 3 capacitor
method. I used this one in all my RC cars and many of the RC toys
that I have taken apart use this method.
| Step 1 You will need 6
.1uf capacitors They should be rated roughly 3 times your motor
voltage.
Kronos
Robotics sells a set of 6
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Step 2 Take 2
capacitors for each motor and twist them together as shown.
Clip Leads and solder together.
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| Step 3 Scratch a spot
on the motor between the two terminals as shown. Using
soldering iron apply some solder. Then solder the twisted end
of the two capacitors to the spot on the motor case as shown.
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Step 4 Insert the
third capacitor into the holes in the terminals as shown. At
the same time connect your motor wires. Solder in place.
If the motor leads are longer than a couple of
inches they should be twisted.
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Here is another pic of some motors with a slightly
different terminal layout.
We attach a capacitor from each terminal to the metal case
of the motor. Then we attach a third capacitor across the the
terminals.
Action 2 Twist Wires
One of the easiest and most overlooked technique that can
be done to lower motor noise is the twist your motor and motor power
wires. This in affect forces the magnetic fields to cancel each
other out.
Notice how the motor power connector here is twisted.
Took me all of 10 seconds to do this and I can tell the differences.
If the motor leads are longer than a couple of inches they should be
twisted as well.
By just using the above techniques I multiplied my RC radio
range by 4. What else can you do? Well actually there are
several.
Shielding
By placing a metal shield between your motors and radio can
do wonders. Also keep in mind that some metals shield better than
others. Carbon Steel shields several hundred times better than
aluminum. Dont use this shielding as a conductor or you may compound
the problem.
Wire Placement
Place your high current wires away from sensitive areas and
antennas. Don't run the wire parallel with wires that are used as
signaling in your micro controller. If you must its best to have
them cross at 90 degrees.
Micro Controller IO Leads
When not in use micro controller leads should be held high
or low. In most cases I have had success just setting the
unused ports as output.
RC Radio Antenna Placement
In the past I used a piece of piano wire to wrap my RC
receiver antenna around for support. This is an absolute No-No.
I now use a stiff piece of plastic about the diameter of a drinking straw.
I run the antenna up through the center.
 
Where do I get this plastic tube. I get it from my
local department store. I purchase one of those plastic kites.
They no longer use wood. Instead they use this thin plastic tubing.
I get 3, 2' tubes for about $2.
Also note how I attach small perf boards to my radio
receiver with foam tape. I use small headers to run leads to a
header so I can quickly attach my receiver to a breadboard on my bot.
Parts
list
Motor Suppression Caps
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