ACX1_TAU_SYNC_UserManual_En
Page 36 of 37
SME S.p.A. Via della Tecnica 40 Z.I.
36071 ARZIGNANO (VI) ITALY
Phone +39 0444 470511 - Fax +39 0444 451803
sales@sme-group.com - www.sme-group.com
6.3 Immunity to EM disturbances
Immunity is generally achieved by preventing the external electromagnetic disturbance from
coupling into sensitive circuitry.
The wires connected to the controller act as antennas and the amount of RF energy coupled into
them is proportional to their length.
Controller:
• The RF voltages and currents induced in each wire are applied to the controller pin to which
the wire is connected. SME controllers include bypass capacitors on the printed circuit
board’s wires to reduce the impact of this source of noise on the internal circuitry, but in
some applications an additional filtering in the form of ferrite beads might also be required.
• Radiated paths are created when the controller circuitry is immersed in an external field.
This radiation may couple with the traces on the board and generate various kinds of
malfunctions. If radiated disturbance is an issue, a good solution is to increase the distance
between the controller and the possible sources of disturbance or to shield the controller
by placing a metal enclosure around it.
• If a shield is required, holes should be added for ventilation purposes. In this case, using
several small holes instead of few larger holes is preferable, because holes reduce the
shielding capabilities (remember that reduction in shielding is a function of the longest
linear dimension of a hole rather than the area).
Signal:
• Low current signal wires should not be run next to the motor cables. When necessary they
should cross the motor cables at a right angle to minimize noise coupling.
Serial:
• Cut the black wire just over the cable’s shield and solder it with the drain wire in both sides.
Protect the soldering with the heat-shrink insulator.
CAN Wiring:
• CAN wiring should be kept away from the high current cables and cross it at right angles
when necessary.
• It is strongly recommended to use twisted pair with shield and to connect it to ground.
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