Raspberry PI - 433 Mhz receiver

[Mike Biddell]

Just wanted to share this find with other Raspberry Pi owners wanting node-red 433 meg control OOK/ASK, as there are loads of cheap 433 meg controls. This receiver has good range http://www.ebay.co.uk/itm/280936648330. Have connected its power rails to GPIO 3.3 volts and digital RX directly to GPIO pin (no danger as max is now 3,3 V).  Using it with RFSniffer with the code modified as suggested by Dave (added stdout). It's got about 5 metre range and with a proper antenna should comfortably achieve 15 metres.

[Julian Knight]

There are indeed a great many that are suitable. And many are cheaper than that module and don't need shipping from the USA (watch out for import duty too, it can add 30%).

[Mike Biddell]

Julian

I tried the cheaper ones and got a 6 inch range.

mike

[Emil Oberg]

I've been playing around quite a bit with 433 Mhz + Node-RED + Raspberry and my money is still on the Tellstick. It's a more expensive device (80 GBP/87 EUR/96 USD/800 SEK) but it's really reliable, got a great API and the reach is far better than any small eBay/Alibaba transceivers I've tested, even with an added antenna. Haven't tested the range but It has never failed in my fairly big apartment.

[Mike Biddell]

it is very expensive........ how do you use it with node-red????

[Julian Knight]

Something wrong there then - I've used a number of cheap devices at 433MHz and 2.4GHz without issue.

At 2.4GHz, the nRF24L01 works just fine. Not tested the total distance as I only needed a few metres inside the house but I had no problems up to around 5-10m with internal walls.

At 433MHz, I've used these modules which are cheap and easily found. Again, didn't find any issues with distance in the house. Make sure you have ones with aerials attached if you want the distance.

I'm now playing with the Ciesco SRF modules which are still pretty cheap but should have a lot more range and capability. Not tested the range again beyond a few metres as yet but others seem to get on well with them.. They also have the advantage of internally supporting encrypted links which as great for IoT uses. They are also controllable just via serial commands and can go into very low power modes.

I'd like to play with Bluetooth v4 Low Energy (BTLE) modules and they are just becoming available at a reasonable cost.

I'd also play with Wi-Fi modules but they are much harder to use due to the networking overheads and require more power too. They have also be stupidly expensive for IoT use though again, the costs seem to be coming down at last.

[Julian Knight]

I use a RFXTRX433 unit from RFXCOM. It is similar to the Tellstick I think and at similar cost.

The real advantage to these modules is that they directly support the common 433MHz based home automation protocols such as X10, Home Easy, LightwaveRF and Oregon Scientific.

The rfxtrx433 has phenomenal range and has no problem listening and sending commands to LightwaveRF/Home Easy and Oregon Scientific devices right the other end of our Victorian house, easily matching the distance of my Wi-Fi router. I have it in the office in the loft. It is a USB device and works perfectly well with the Pi which is how I'm using it.

But I don't think this is the kind of device you want from how you've described things. I think you would probably be better off with one of the radio types I've mentioned assuming you are, like me, building your own wireless sensors.

[netco...@googlemail.com]

And you really can't beat a food aerial on those 433Mhz modules

eg this sort of thing

http://www.ebay.co.uk/itm/3db-Antenna-aerial-433Mhz-RP-SMA-F-with-Magnetic-base-Ham-radio-/290868517257?pt=LH_DefaultDomain_3&hash=item43b91d5989

kevin

[Mike Biddell]

Julian errrr I dont understand that. For the cheap modules, what are the details of the connections to the GPIO you have used. Have you used a potential divider? What software are you using etc. Perhaps my GPIO has a problem !!!!!

[Dave C-J]

Mike

well reminded.... I meant to dig out the one I had in my bits box and give it a whirl. Last time I tried it range was pretty good - certainly got through 2-3 walls ok. Main thing was to add a "decent" antenna.... aka straight bit of stiff wire 16.4 cm long... more accurate the length the better.

[Mike Biddell]

yes... I have sent for that exact aerial..... I have 5 metres with just a length of wire, so it shud do quite well with that antenna.

[Mike Biddell]

with the same cheap 433 receiver as you specify, I got a 6 inch range?????? Wonder what the problem is????

[Dave C-J]

I always found simple copper wire antenna direct soldered on gives better range than any coiled one or one that goes through half a meter of coax first ... 

[Mike Biddell]

dave..... it's weird.... but I'm not sure we are comparing eggs with eggs yet. I need to know how Julian is connecting his cheap receivers. There is a voltage issue if you connect to 5V, as the GPIO pins are rated for 3.3 volts. If you use 5V, how you potential divide or down convert the voltage could be an issue. Another issue might be the GPIO pull down resistors, which I believe can be software controlled. Either way, since other people are getting good ranges with the cheap receivers, either I am doing something wrong or my GPIO is below par/knackered in some way !!!!!  I have a simple straight wire antenna at the moment, but still only 6 inch range with a cheap receiver ??????

Bewildered of Tamworth

Mike

[Dave C-J]

If it's a 5V receiver then it'll need 5V to perform.... so you can drive that from the 5V pin on the Pi... - it's the GPIO inputs you need to be careful with, so yes use a voltage divider. As long as you do that then you should be able to turn off the GPIO resistors. (If you do leave it on then leave it on on the pull down side - so that is is parallel with your own resistor making the input voltage even lower...)

[Julian Knight]

To be honest, I'm not up to much on the electronics front! But a simple voltage converter is enough, I brought a bunch from eBay.

Generally my electronics is poor enough that I prefer to avoid messing with the Pi's GPIO and simply connect up an Arduino clone instead. That's one of the reasons I'm switching to the SRF's - at least I will if I can ever get on their forum to find out which one I need for my low power Arduino clones. At the moment, I've got the Slice of Pi plugged in to the Pi and a shield plugged into my original Arduino UNO.

[Mike Biddell]

Julian, ahhhh I didn't think we were comparing eggs with eggs.... you are getting a decent range with arduino. 

A voltage converter could be the answer..... connect the receiver to 5V on the GPIO and down convert to 3.3V.

mike

[Mike Biddell]

Dave .... I get the impression that the GPIO has aggressive pull downs. I'll Google how to turn them off !!!!!! i've seen a command somewhere.

mike

[Julian Knight]

Yes, that's what I did on the Pi but to be honest, it's too much trouble!

I can build an Arduino for around £5, plus £10 or so for an SRF module. That can be run from standard batteries for months, years if you are careful and restrict the data flow.

Then just stick the slice of radio on the pi for another £10.

You can even get a micro Arduino clone from Ciesco for £14. They do suitable antenna's too if you need extra range. These are all 868MHz for the UK.rather than 434MHz.

Encrypted comms with simple serial commands for a very low price, not sure you could ask for more?! :)

[Mike Biddell]

Julian ... thanks for the info..... the slice of radio looks interesting and I haven't heard of that before.

mike

[Claudiu O]

MIke, there is no need for a voltage divided for receiver on Raspberry Pi, at least not for the modules I used; basically same cheap modules that Julian mentioned got them from ebay. In the seeedstudio wiki it says "Receiver Data Output: High - 1/2 Vcc, Low - 0.7v" and indeed in my experience the receiver doesn't put out more than 3.3 V even if powered with 5V.

You are right about the range, without antenna the range is so small I thought my modules are broken. However, after finding this instructables and adding an antenna, the range became pretty decent, about 15m, I think.

Unfortunately I couldn't figure out how to use these modules directly with node-red so instead I am reading the data using a modified version of RCSwitch for NinjaBlocks (my project in github, in case it helps). I see you mentioned Dave suggested using RFSniffer, can you please point me to the related post? Thanks!

[Mike Biddell]

Claudiu

I've never seen the spec before ..... 0.5 of VCC is great..... means 5V supply will present 2.5 V logic 1 to the GPIO pins.... so that means it wont damage the GPIO.

Dave C-J solved the problem of using these receivers with node. You simply edit RFSniffer to add stdout, and remove the "Received " from the output string, so that it just returns the numeric RF code e.g. 12345678. You can run RF sniffer from within node using "daemon" and pipe the output into "switch node" so each code then can have a specific action from the switch. It almost sounds as if I know what I'm talking about..... but it's all Dave really !!!!!! You have to use SUDO, but if you look in this forum at my previous chats to Dave, he explains how to solve the SUDO issue too !!!!!!

Mike

[Claudiu O]

Thanks a lot, Mike, for the info about RFSniffer, I will revive my old project and try to figure it out, it would be awesome if I could do the entire thing in node-red, without additional C code. Thank you!

[Mike Biddell]

Claudiu

It all works as advertised...... Only the flea powered receiver issue was holding me up. The transmitter is fine. It looks as though the receiver I quoted at the start of this thread will give a very good range...... I'm stuck doing other stuff at the moment, but will get back to this project soon. I've also been waiting for Thingbox to incorporate the latest node-red, so that I can use HTTP binary to get piccies from my IP cameras ...... I'll try that next !!!!

Mike 

[Emil Oberg]

Hi Mike, sorry for the late reply, I'm out of country working day and night...

So how do I use the Telldus with Node-RED? Well, I've written a full featured module for it: https://github.com/emiloberg/node-red-contrib-telldus

It hasn't been released to NPM yet (as I want to write some tests before it first), but it's fully functional.

Emil

[Mike Biddell]

Thank you....