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Updated: July 17, 2013

R/C Servo Noise Trap Filter Projects




Testing & Operation


Note: All pictures that follow are "clickable".  Clicking on them will show you an enlargement!

A lil' history ...
    This project involves the building of a simple R/C Servo "Noise Trap" device that simply suppresses and amplifies the receiver's servo signal before it is applied to the actual servo.  In the past, the use of long servo wires and/or ignition type engines made the R/C electronic systems susceptible to RF noise (i.e. Electro-Magnetic Interference or EMI).  Servo leads/wires/extensions, particularly long leads, can often act as RF antennas, allowing EMI to get propagated back into the R/C electronics, with the potential of causing havoc.

    This device, based upon a cheap 4069 Hex Inverter, includes a 8 pin DIP (or surface mount device component as shown in picture), one .01uf capacitor and one 1K ohm resistors.

Design Criteria Summary:

1) Small/Compact device
2) Self-powered (via servo leads) device
3) Minimal components (3 not counting circuit board or connectors)
4) Buffering/Amplifying capability

Parts & Tools List ...

1) 1 - Hex Inverter IC (preferably 4069.. I have not tested/designed with any other IC)
2) 1 - 1K ohm resistor
3) 1 - .01uF Capacitor (voltage rating should be at least equal if not greater than supply voltage)

A circuitboard facilitates assembly of course...

Building Instructions...

The schematic to the left tells the whole story... simple design to say the least!


... more coming soon...

Testing & Operating Instructions...

The servo signal supplied by the receiver is connected pin 1 of the 4069 IC.  This amplified servo signal is then supplied at pin 2 (inverted), and in order to recover the signal, we need to invert it once again by connecting the first buffer output (pin 2) to pin 3 (input) of the second buffer.  The output of this second buffer (pin 4) will contain the amplified and buffered servo signal.  Noise or interference picked up by long servo leads are "cleaned up" by the two inverting buffers. The filter capacitor is included to reduce EMI noise from devices such as noisy servo motors and motor speed controllers while the resistor simply limits the current supplied to the IC.


Additional Notes...

    More to come soon.....

Earthmen Productions
Earthmen Productions

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This site was last updated 03/30/12