Instead of the old analog circuit with 8 relays and some op amps I built a controller using an Uno compatible. After initial issues everything works fine with the exception of the 433 Mhz remote control unit that is installed in the cover of the waterproof box next to the lcd display.
It has an external antenna and had a useful range of approx. 100 meters before the conversion.
With the new setup the range is reduced to approx. 2 meters!
RFI from the Arduino board is the only thing I can think of. The remote receiver has not been modified, just two voltage dividers have been added to convert the 12V signals to 5V.
Is there a software solution to put the Atmel processor in sleep mode or any other way to reduce the clock frequency?
Question is too vague to answer.
What kind of 433 Mhz receiver is being used?
What type of transmitter is being used.
How is the receiver powered.
Its extremely unlikley the Arduino board will be creating any interferance at 433 Mhz.
Hi,
What is the application?
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
How are you powering the projects.
Did you do a mud map/circuit before you did the conversion, measuring voltages under various conditions?
Have you put bypass capacitors on power supplies and the divider for the remote Rx output.
There isn't much I can tell you about it.
The remote Rx I took from a car alarm at least 15 years ago. A 3" circular circuit board once mounted in a siren. Powered by 12V from a car battery it has two relay outputs that are toggled for approx 1/2 a second when the correct code is received from the Tx, which is a tiny black box with just one button.
The Rx has its own 7-8 V regulator, filter capacitors and even a ferrite coil.
The Rx is now mounted vertically inside a waterproof box with a 7" whip antenna connected to it, just as it has been for all these years. Power comes from a solar charged 12V battery in a compartment nearby.
The Arduino, relay boards, current sensors etc. are all mounted on a copper clad board connected to ground at a single point. The Arduino gets 12V from a large screw terminal and so do the wires to the 30 Amp relay contacts; the coils get 5V from a separate 7805 regulator.
The old circuit was completely static unless the gates were operated. The remote control range was at least 100 meters, even more in specific places.
Now the range is reduced to 2 meters; I have to get out of the car and reach over the gate otherwise the system does not respond.
Yes, absolutely. RFI from digital circuitry can interfere with the signal at the receiver. I disagree with a previous post about the Arduino not generating RFI. Perhaps with no wires attached. But as soon as you have the typical "rats nest" of wires, you have a number of antennas radiating wideband harmonics of all kinds of frequencies. In my recent experience, I've already had trouble once with a display that killed the receiver sensitivity. None of my receivers will work properly next to my PC.
The receiver is designed for the maximum practical gain. Of course it will pick up anything that arrives at the antenna. A signal doesn't have to be strong when it is in the near field of the antenna, to register.
aarg:
Yes, absolutely. RFI from digital circuitry can interfere with the signal at the receiver.
Exactly, the receiver RF stages have automatic gain control. The noise from the microprocessor deafens the receiver.
One option would be a grounded screen around the Rx, but then there still is the antenna picking up noise.
I read in the Atmel 328 datasheet the chip has a sleep mode but cannot find if/how that is implemented in the Arduino.
Hi,
What sort of box was the antenna on before you changed it?
If it was metal and now plastic, you need to have a metal area around the antenna connected to the powersupply gnd.
This acts a a ground plan to help the antenna pattern and matching.
CDK1:
Exactly, the receiver RF stages have automatic gain control. The noise from the microprocessor deafens the receiver.
That would be my guess also.
Older remotes were often am and sometimes used super regen recievers to reduce power.
They are particularly susceptible.
A filter on the receiver input may help if you can accept the loss.
I had exactly the same problem with a garage remote intermittently.
I eventually discovered that it was if rf interference from a local DAB transmitter.
TomGeorge:
Hi,
What sort of box was the antenna on before you changed it?
If it was metal and now plastic, you need to have a metal area around the antenna connected to the powersupply gnd.
This acts a a ground plan to help the antenna pattern and matching.
Tom....
Car alarms back then were large plastic pods with the board mounted in the top; the antenna was a dangling piece of wire with a red "do not cut off" label.
I could use coax and relocate the antenna or remove the complete receiver and mount it in a separate box. Both are rather difficult because of mechanical reasons.
Removed the remote RX from the housing of the Arduino, put it in a plastic jar and mounted it 2 ft. higher.
As a result the range improved 10-fold. Still not as good as it was before, but at least it is useable now.
This is proof of a strong RFI field emitted by the Arduino board and associated wire spaghetti on top of it.
Even with the processor in sleep mode there still is too much noise for a remote RX to properly function.
