Download How to check receiver servo outputs

How to check receiver servo outputs
Ever wanted to check the servo output signal of your receivers?
Normally, this requires an (expensive) oscilloscope. But if you simply
need to know if the receiver is working, you can run a quick check on a
receiver's servo output pulse signal with an over the counter digital
multimeter.
First, you need to access the servo's black wire, and the third wire which
will be white/orange/whatever? colour. These are the two outside
connections of the servo plug. Don't be tempted to use crocodile clips
directly to the output pins of the receiver, to much of a chance you could
accidently short the black and red wires together. That will cause a short
circuit on your receiver battery which is not to be recommended!
Instead, use an old servo leadwire, which can be modified for this test.
Strip the insulation off the black and white/orange/whatever wires. Do
not strip the insulation on the red wire. (prevents accidentally shorting out
your receiver battery!)
Connect the black wire of a multimeter to the black servo wire, the red
wire of the multimeter to the white/orange/whatever signal wire. Set your
multimeter to DC volts, on its 2.00 Volt DC range. (If your multimeter is
autoranging, you must manually set it to its two volt DC range. (20 volts
will also work, but with less accuracy. Don't use the 200 millivolt range,
the receiver output will hit some 5 volts, causing the multimeter to clip
the voltage off, giving wrong readings.)
Plug in the modified servo plug into your receiver, turn on the receiver,
transmittter and multimeter. With your transmitter stick in neutral
position you will measure about 0.225 Volts DC, with a receiver battery
measuring 4.8 Volts DC. Move the transmitter stick "Full up" your meter
will change either up or down, depending on whether the servo is
reversed in the transmitter. Move the transmitter stick "Full down" and
your meter will read the other way. A higher or lower battery voltage
will likely affect this reading, depending on the receiver brand.
I've tried this with a simple digital multimeter, and measured 0.22 volts in
neutral, 0.27 volts in full up, and 0.18 volts full down. If you slowly
move the transmitter stick up and down, the multimeter voltage should
also move very smoothly, with no jerks or what ever.
Just a note, if you are using a 2.4Ghz radio, no problem. But if you are
using a 27Mhz or 40Mhz radio, keep the transmitter at least 10 feet or
more from your multimeter and receiver. The transmitter's transmitted
signal could get into your digital multimeter, and make it give weird
readings.
Different receivers might give somewhat different voltage readings. I
used a Planet 2.4Ghz receiver. But, regardless of which radio you have,
the voltage measured should vary when you move the appropriate
transmitter stick.
What are we measuring here??? The receivers servo output signal is a
pulse type signal, that outputs voltage between zero volts and battery
voltage on each pulse. That pulse ranges between 0.001 and 0.002
seconds, with 0.0015 seconds as "neutral". This pulse wave train repeats
about 50 times a second. The multimeter averages this pulse signal out,
resulting in that 0.22 volt reading.