I have a 433.92 mhz RF receiver sensor that I use to wirelessly communicate between multiple Arduino's. I noticed that sometimes I get great range distance and other times I do not. I have been reading up about optimizing RF and I read about two things I am currently not doing:
Choke - apparently the DC line needs a choke to reduce AC interference or something like that
100nF capacitor - apparently 100nF capacitors are needed to also reduce interference
One of the things I've read which I have already changed was to hook the sensor voltage up to a external power supply, that has improved range greatly.
Does anybody have more intel about this? I have read this somewhere on another site which listed some layout practices for 433 RF. It didn't have any schematics or additional info.
Should I add these components? What is the expected benefit of it? How can I measure the results? Where in the circuit do I place these components? On the input voltage or on the data line?
If you do not have clear line-of-sight between the two devices you are at the mercy of any
conducting material (metal) and absorbing material (damp masonry, people, trees) in
between.
If you have clear line of sight you simply need to ensure both antennas are polarised the
same and pointing the right way (if directional) to get maximum signal reception. The
transmitter's antenna in particular needs to be correctly tuned to resonance to increase
radiated power, which depends on the type of antenna.
An antenna system comprises two parts, the antenna itself and the grounded structure
or cable that it emerges from - both contribute to the radiation pattern.
Thanks for your reply, very informative. I will have to play with those values. Since you didn't comment on my original question, do you think I won't need the choke and the capacitor?
Make sure that the supply voltage to the receiver is as close as possible to 5V.
The receivers will work with higher or lower voltages, but their sensitivity is degraded as
the onboard local oscillator drifts with changes in supply.
Also, if possible dont locate the receiver physically close to the Arduino, as all Microprocessors
create broadband noise.
433.92 is a shared frequency and you will often experiance interferance from other devices on the same frequency
which can create the affect of range loss.
Thanks for all the info and suggestions, I will try them out! Also thanks for sharing the 2.4Ghz transceiver modules, those are a steal. I am currently working on something that requires 433 to integrate with existing hardware.
One additional question. I have put the 0.1uF capacitor on the 5v line and the sensor has stopped working all together. I measured the 5v after te capacitor and it reads 0.2v now. I am confused. Did I use the wrong capacitor (it reads 104 on it).
Thanks a lot for your answer. I thought I was good to go today so I was really waiting for a response.
I have some more reading to do, this stuff can be pretty difficult if you come from a different world.
I have placed it in my circuit and everything still works, succes!
Since I have a 5v voltage regulator, should I put the capacitor on the 12v line or on the 5v output of the regulator?
I'm using the Arduino to drive a ledstrip, which operates at 12v. I wanted to power the Arduino with this power source as well, so I added a 5v voltage regulator. This in turn powers the Arduino and the RF sensor.
Does the voltage regulator make the capacitor unnecessary?
Should I put the capacitor between 12v and ground or 5v and ground. As stated I am powering my project with a 12v power supply and I am using a voltage regulator to get 5v into the Arduino and the RF sensor.
Should I put the capacitor between 12v and ground or 5v and ground. As stated I am powering my project with a 12v power supply and I am using a voltage regulator to get 5v into the Arduino and the RF sensor.
Does it matter at all? Why not or why so?
thanks again!
In addition to the decoupling cap right next to the devices, you should also have a cap on either side of the regulator (this is true in general of regulators - they can't provide stable output without caps) - datasheet for Fairchild's LM7805 suggests 0.33uf on input, 0.1uf on output - I usually go larger than that though, for good measure. Also, check the datasheet to make sure it doesn't specify the type of capacitor (some regulators don't like ceramic caps)
Its worth repeating - look in the datasheet. Often the manufacturer will provide a few
example circuits which can save you time and uncertainty... The more datasheets you
read the faster you can glean useful information from them, and you sometimes find
some cunning circuit tricks...