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Reciever detection?

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New Member
Hey all,

I've been using Airtronics (http://www.airtronics.net) 72 Mhz receivers for my RC plane and was looking to impliment a few new features.

I'm looking to detect if the 72Mhz signal has been lost (i.e. out of range, etc). I'd like to use the fact that the signal has been lost to impliment a few saftey features (a 50 pound hunk of wood flying for miles because its out of my control can only end in distaster...so I'd like to cut the throttle on the plane so horizontal momentum is reduced)

Does anyone have any suggestions on how I could use a pretty simple circuit and modify a reciever if necissary to figure out if there is a signal being recieved or not?

Thanks in Advance!


Active Member
It's possible with AGC-level monitoring. Open the device, discover the receiver-chip and try to find a datasheet. Most of IC have a pin for field-strength meter.


Active Member
Is the transmittter "on" constantly or are there normally periods of time when nothing is being transmitted?

If it is normal for a command to be received regularly, lets say every 10 seconds or so, you could rig a simple timer to throttle back if no command is recieved in a given period of time.


New Member
Look for a failsafe schematic on the internet. They are there in abundance. I prefer the PIC based ones as they are a little more intelligent. The schematic can be placed between reciever and the servo and measures the pulse going to the servo. Pic based fail safes check if the pulse is between 1ms and 2 ms if so, they let the signal through. If not they replace it with a preprogrammed one or retain the last "good" pulse to the servo (servo hold).
Most also have a timedelay between the detection on the first false pulse and the actual fail safe function so that when the signal deteriorates the servo doesn't start jittering between the right position and the failsafe position.

PS these schematics do NOT work with PCM transmittors and recievers.

Try www.eagleairaust.com.au they have a very neat pic based fail safe complete with schematic and soruce code.

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