RF transmission/reception

Using Arduino Project Guidance
#1

Hi all-
My goal is to transmit 4 buttons wirelessly to my arduino/head end equipment.

I have been looking at the RF Link Transmitter - 315MHz - WRL-10535 - SparkFun Electronics
and the https://www.sparkfun.com/products/10533

I want the transmission end to be very small form, I am trying to get away without using an arduino at that end, but it doesn't look like the transmitter will do it without it, being that it is essentially a wireless serial 'wire'.

any input would be helpful, this is my first foray into wireless.

(i have looked for 'wireless one arduino' on the forms and general google, but i may be searching for the wrong terms)

thanks for the help!

#2

You could use an nRF24L01+ transceiver with any Arduino clone or standalone chip that included SPI - there are some very small ones available. There's also at least one clone that has an onboard transceiver http://shop.ciseco.co.uk/rf-328-bare-arduino-atmega-328-compatible-micro-board-rfu-328/ so you can get tiny wireless-enabled Arduinos very cheaply.

#3

Those very cheap modules can be used with the VirtualWire library, http://www.airspayce.com/mikem/arduino/
The VirtualWire library is a software protocol, so you need an Arduino.
For remote temperature sensors and buttons, it will do.
You could use an standalone, Arduino - Home chip and make it Arduino compatible.

My advice is to buy a RC-Switch compatible remote switch. They cost about 2 dollars/euros on Ebay.
Capture the code with such a cheap receiver and use the RC-Switch library, GitHub - sui77/rc-switch: Arduino lib to operate 433/315Mhz devices like power outlet sockets.
Most of the very cheap remote switches are compatible.

In some countries the 433MHz is legal (Europe), and in other countries the 315MHz (US).

#4

I have been looking at the RF Link Transmitter - 315MHz - WRL-10535 - SparkFun Electronics
and the RF Link Receiver - 4800bps (315MHz) - WRL-10533 - SparkFun Electronics

Those cheap modules are pretty crappy in operation. See where sf says, “Note:
These modules are indiscriminate and will receive a fair amount of noise”. At
least they say so.

http://shop.ciseco.co.uk/rf-328-bare-arduino-atmega-328-compatible-micro-board-rfu-328/

These modules look pretty good, as they have the Arduino built in, and the RFM12B
transceivers are highly sophisticated devices, light years better than the other ones.

Also, what transmission range are you looking for? Typically, low power devices, eg
0 dbm [1 mW], are only good for up to about 10m.

#5

My advice is to buy a RC-Switch compatible remote switch. They cost about 2 dollars/euros on Ebay.
Capture the code with such a cheap receiver and use the RC-Switch library, GitHub - sui77/rc-switch: Arduino lib to operate 433/315Mhz devices like power outlet sockets.
Most of the very cheap remote switches are compatible.

I kind of like this option, but i am curios, how do the rc buttons output the unique bursts that they do, to be captured by a reciever (in our case, by the RC-Switch library)? could i create the unique output per button on my own, to then capture with an arduino running the RC switch library?

Those cheap modules are pretty crappy in operation. See where sf says, "Note:
These modules are indiscriminate and will receive a fair amount of noise". At
least they say so.

I noted that, but thought that since i am essentially just monitoring button presses, i could get away without it being too robust.

there are some very small ones available. There's also at least one clone that has an onboard transceiver http://shop.ciseco.co.uk/rf-328-bare-arduino-atmega-328-compatible-micro-board-rfu-328/ so you can get tiny wireless-enabled Arduinos very cheaply.

I think i may end up going this route. it seems very feasible. I need the transmitter end to be as small as possible (it will be going in a sweat band, to be worn while playing racquetball), but the receiver/display end will be larger. I will probably be displaying a score (count button presses) with small nixie tubes. I have a bunch sitting around, and this seems like a cool use.

Also, what transmission range are you looking for? Typically, low power devices, eg
0 dbm [1 mW], are only good for up to about 10m.

It is possible that you saw a post i made earlier, about using a theremin-type input to control a racquetball scorecard. This is for the same thing, so if someone were standing at the very front of the court, they would be about 12m away from the receiver, and only a single pane of glass between them. most likely, the transmitter will be about 6m away from the receiver when changing the score. I really liked the idea of the theremin style control, but in terms of keeping a game moving, it wasn't the best.

#6

zacnotes:
how do the rc buttons output the unique bursts that they do, to be captured by a reciever (in our case, by the RC-Switch library)? could i create the unique output per button on my own, to then capture with an arduino running the RC switch library?

They use the PT-2262 or PT-2272. You can't change the pattern, but the RC-Switch library is able to recognize it. Such a cheap remote switch could send 24-bits. It contains of a group code, followed by code for the switches.
The RC-Switch library is working good, but it is not a well written library, and there are a few other libraries for that protocol.

Part of the protocol is that the code is transmitted a few times (perhaps 10 times or more). You have to keep that in mind when receiving the code.

These modules are indiscriminate and will receive a fair amount of noise

Those modules have AGC (Automatic Gain Control), so if nothing is received, the noise is amplified until it starts receiving noise.
The VirtualWire library is able to detect a protocol from that noise, and so does the RC-Switch library.

#7

Those cheap modules are pretty crappy in operation. See where sf says, "Note:
These modules are indiscriminate and will receive a fair amount of noise". At
least they say so.

I noted that, but thought that since i am essentially just monitoring button presses, i could get away without it being too robust.

Button pushes may be the worst thing for use with noisy systems, You don't want the
whatever turning on and off randomly all the time. The more sophisticated transceivers
use packet protocols, source-destination addresses, CRC checks, and etc, so for a message
to be received properly, it has to obey fairly strict criteria, else no output reponses.

#8