So I have a project with an Arduino connected to control the power to a walkie talkie handheld radio at 450 MHz. basically the radio waves were inducing voltage into the power lines of the Arduino device. I moved the radio farther away from the core electronics but what I am discovering is that the power wires, serial connection, and audio wiring going from the core electronics to the walkie talkie are absorbing the radio waves. I believe that I need some type of ferrite core or shielding? any advice is greatly appreciated!
what I am discovering is that the power wires, serial connection, and audio wiring going from the core electronics to the walkie talkie are absorbing the radio waves.
Of course they are. Any conductor absorbs radio waves.
What is the problem?
It is causing glitches in the arduino, for example the arduino thinks buttons are getting pressed.
Schematic?
Picture?
It could be RF interferance - or it could be noise on the power supply - or there might be some issue with the layout that becomes visible with a picture that's making it worse.
With both a picture and a schematic, things will be more clear.
Also, are you reading the buttons right? ie, have you taken measures to ensure that when the button isn't pressed, the pin will be in a known state?
It is hard to see how 450 MHz signals could interfere with button presses on a 16 MHz machine, because the signal on the input pin is required to be stable for one machine cycle, or 1/(16 MHz). However, it is conceivable. What is your evidence that the radio is actually causing the problem?
You can always use shielded cable for the connections, and put the Arduino in a metal box, but I doubt that will be necessary.
Yes get some ferrite rings and wrap the wires round a few times, that will reduce the UHF pickup. Shielding is not likely to be much good though.
Decoupling capacitors will also help as will ferrite beads.
100pF ceramic to ground on every input can tame the differential-mode noise, ferrite toroids for
the common-mode.
Whats the power rating of the Walkie Talkie and how far away from the Arduino is the Walkie Talkies antenna?
Does the interferance still happen if you disconnect the walkie talkie from the Arduino and just hold it nearby while transmitting?
I keep explaining here about "lead dress".
All leads simply must be paired - positive and negative supply lines travelling together, connections to relays, motors, LEDs, sensors, all in pairs (or grouped together with power feed and signal to the controller).
Using "jumper wires" on modules or breadboards is not workable for complex (or any "production") assemblies or where RF is present.
jremington:
It is hard to see how 450 MHz signals could interfere with button presses on a 16 MHz machine, because the signal on the input pin is required to be stable for one machine cycle, or 1/(16 MHz). However, it is conceivable. What is your evidence that the radio is actually causing the problem?You can always use shielded cable for the connections, and put the Arduino in a metal box, but I doubt that will be necessary.
It's because of the rectification effect of the non-linear devices in the Arduino. It's a well known effect. The most popular example is how computer speakers will sometimes make a buzzing noise if you leave a GSM phone nearby. That's happening at a huge ratio of freqency, 800MHz to audio.