Radio intereference on PIC?

[zaobz]

Hi,
I posted this on the robotics forum, but seems like not so many people visits there.. sorry for posting double.

I'm building a robot that's gonna be controlled using Futaba's T6EXAP with R146iP receiver. I'm using PIC micon at the receiving end, and it seems like the radio control is messing up the system. (when I put my hand between the receiver and the PIC, everything works. Otherwise, it stops working) :confused:

What's going on exactly? and what can I do to fix this? Should I build like a faraday cage (is that what its called?) to conceal the microcontrollers?

The radio frequency is 40Mhz btw.

[Bruce Abbott]

Which PIC, what type of oscillator is it using and at what frequency?

[zaobz]

It's PIC16F88 using the internal oscillator at 8 Mhz.

[Mr DIY]

Let me understand this correctly.. are you saying that the receiver is interfering with the PIC, as opposed to the PIC interfering with the receiver? What is the Tx doing at this time? Is it on or off?

A quick test is to wrap the Rx in tinfoil. This should help reduce any emissions from the receiver … if this is the problem.

Brian

[zaobz]

Yeah, the receiver is interfering with the PIC.

I'll try that foil method once I get home. Thx.

edit - And the transmitter is on during this...

[Bruce Abbott]

It's PIC16F88 using the internal oscillatorThen I doubt it would be stopped by low-level RF interference. More likely you have a floating input pin, causing the program to malfunction when it sees a strange value.

Have you configured pin 4 as RA5, or as MCLR? If set to MCLR (the default) it must be connected to Vcc via a resistor. Leaving it floating will cause unintentional resets.

[Mr DIY]

More likely you have a floating input pin, causing the program to malfunction

If the pin is a floating input pin, then it is unlikely that the pin is being used. And if it is not used, an unconnected pin ought not be enough of an antenna to pick up and RF interference. But everything you can check is worth checking out anyway. Bruce has a good piont on the MCLR.

I asked the question of transmitter status as the transmitter is most likely culprit to couple significant RF voltage swings onto the robot wiring… if Tx close by. You could check this by turning of the Tx and leaving the Rx switch on.

Brian

[Malc C]

I had a problem when using a pic based project in a model railway layout. The RF generated by the locomotives running on the track was enough to cause all manor of problems, and it wasn't until I used 0.1uf Capacitors between all inputs and GND did the PIC functioned correctly.

[zaobz]

Weird, the circuit just seems to work correctly today. I guess I'll just wait for the day it goes crazy again, while keeping those capacitors ready :D thx for all the suggestions.