Transceiver ?

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cooldude4u2no

New Member
Hello, im new to picaxe only been playing around with it, but have a very good knowledge with electronics. I was curious if someone could point me the right direction as to a RF transceiver that i could use with picaxe without spending a ton of money (Since this is just a hobby). I was trying to find a good way to have two or more devices to communicate back and forth to each other wireless. (Example: device one sends command to device two to activate relay, device two respnds back that relay has been turned on.) I had thought about using just a RF Transmitter and Receiver, but that is only one way communication, i would have no idea if the second device recieved the command or not. Do you believe I am heading in the right direction?

I have looked at the XBee Module, but hoping to find something a little cheaper.
 
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manuka

Senior Member
Cooldude4u2no(Phew!): Welcome-you've certainly come to the right place,since PICAXES & cheap wireless data modules are absolutely made for each other. What sort of ranges & data rates did you have in mind? As the humble PICAXE-08M even has commands to handle IR data you may even be able to use infrared for simple switching!

Simplex 433 MHz TX/RX approaches can be as low as just a few US$ each end, but smarter options using transceivers may be more like US$30 a pair. Ranges to hundreds of metres/yards are typical, but data rates may be quite low (typically 2400 bps).

This topic has arisen numerous times on the Forum ( come in Manie?) & I've also diverse wireless resources at => www.picaxe.orcon.net.nz

Stan. (New Zealand)
 
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cooldude4u2no

New Member
manuka said:
You've certainly come to the right place- PICAXES & 433 MHz wireless data modules are absolutely made for each other. What sort of ranges & data rates did you have in mind? As the humble PICAXE-08M even has commands to handle IR data you may even be able to use IR !

Simplex 433 MHz TX/RX approaches can be as low as just a few US$ each end, but smarter options using transceivers may be more like US$30 a pair. Ranges to hundreds of metres/yards are typical, but data rates may be quite low (typically 2400 bps).

This topic has arisen numerous times on the Forum ( come in Manie?) & I've also diverse wireless resources at => www.picaxe.orcon.net.nz

Stan. (New Zealand)
Click to expand...
Thanks for your reply! Yah ive searched these forums for about 5 hours now, and have read alot of interesting topics, just none that really stated what i really wanted to know.

Im not looking for something to transmit very far, but maybe something powerfull enough to transmit through a wall or two?

http://www.sparkfun.com/commerce/product_info.php?products_id=690

Would something like that work?

I have no clue about wireless communication.
 
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Dippy

Moderator
How big?
Budget?
Range required?
Smart or dumb?
Preferred frequency band (and reason for choice).

Stan and DrAc usually recommend Hope RF devices and yishi/nishi/dishi/squishi (?).. something from China. (I think they get t-shirts :) )

There is so much stuff around, so maybe give us a clue as to required specifications first.
And remember, in many cases "cheap" = "chod". Sacrificing those extra pennies can be well worth it. Speak to some of the people here who have wasted days/weeks after 'economising' with cheap crap from alternative suppliers.

People here can give excellent advice.
 
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manuka

Senior Member
Wall(s) -what sort ? IR won't penetrate solid surfaces, so rule that out. This is the sort of request background we really need for starters.

Take heart my good man Dippy- it's TGIF after all. Are you on the wrong side of morning coffee ?
 
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lbenson

lbenson

Senior Member
The Sparkfun transceiver you point to does not look breadboard-friendly or particularly picaxe-friendly.

If your communication needs are simple, you could use 315mHz or 433mHz transmitters and receivers like those shown here: http://www.sparkfun.com/commerce/advanced_search_result.php?keywords=315mhz&search_section=products

I have used these successfully, but prefer the 315mHz product because I have encountered interference in the 433mHz range. There are many examples of the use of these products on the forum. But as others have asked, what are you transmitting and under what conditions?
 
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manuka

Senior Member
marcos.placona: Ahem-the global 433 MHz ISM band is usually limited to VERY LOW POWER transmitters,with just 25 milliWatts typical. IMHO it's better to go for more sensitive receivers (at least better that -100dBm) & thereby achieve the same range, BUT with less interference to others. You'll also get better battery life.
 
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cooldude4u2no

New Member
lbenson said:
The Sparkfun transceiver you point to does not look breadboard-friendly or particularly picaxe-friendly.

If your communication needs are simple, you could use 315mHz or 433mHz transmitters and receivers like those shown here: http://www.sparkfun.com/commerce/advanced_search_result.php?keywords=315mhz&search_section=products

I have used these successfully, but prefer the 315mHz product because I have encountered interference in the 433mHz range. There are many examples of the use of these products on the forum. But as others have asked, what are you transmitting and under what conditions?
Click to expand...
The one i pointed out would of been a pain anyway. I was looking deep into HopeRF. I lost the page to the one i was looking at. I will post it as soon as i find it again.

Okay so i know this has already been invented, just reconstructing it as a learning experience. But i was trying to design a way to remotely control a thermostat. Build a basic thermostat using A picaxe and thermistor that controls a central heating and air unit in your home. But i want to be able to remotely monitor it and control it using PC Software (ill program that using VB.net). I figured this would require a main module physically connected to the PC that could wireless communicate with the thermostat. The aim behind this all is to be able to control a device over the internet thru a PC (Which will technically i guess be all software based)
 
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manuka

Senior Member
All do-able. HopeRF have rather been usurped by Sure offerings in fact. Accton Open Mesh WiFi units may suit as well - Andrew Hornblow has hacked into their (undocumented) serial port to good effect.
 
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manie

Senior Member
I have used transcievers from Polygon Technologies. They unfortunately do not make these anymore so I guess I'll be looking at the Nishi et al range or other, for future work. The Polygon units work well and 1km range with a "cotanga" antenna is good and reliable. The Polygon units are serving the chook-house across an electric fence at 110 metres distance at 9600 baud, works very well.
 
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Pauldesign

Senior Member
Visit www.linxtechnologies.com/Products/RF-Modules/

for a true meaning of pnp professional RF modules (no long legs).

All u need is your data, power and antenna.

Remember u'll need good pcb layout.

For more details have a look at Linx Tech applications notes they just as juicy and straight forward as picaxe notes.

Good specs and very affordable since u're residing in USA.
 
lbenson

lbenson

Senior Member
The Sparkfun 315mHz modules I pointed out should do fine with the light-duty back and forth which you have described (if they will punch through your path--if not the better receivers on the Dr_Acula site pointed to should work).

Because you don't want the furnace to turn off when you want it on, or on when you want it off, you will need to program some back and forth to make sure that messages are received. For this you will probably need more code space than and 08M or 14M have, so try a 20X2 on either end. Serial out from a PC can communicate with a picaxe with a usb serial dongle (PL2303-type works reliably for me).
 
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manuka

Senior Member
Whatever you do eventually with wireless data, IMHO the general rule is to START SIMPLY- REALLY SIMPLY! Over the years this forum has hosted numerous prolonged wireless woe sagas,many of which arise from nearby interference. Too many config. pins WILL further confuse - START SIMPLY ! Another major issue is that 2.4GHz signals do NOT have the punch thru' obstacles that 315/433 MHz will usually penetrate. This can be somewhat offset by external antenna, which at 2.4GHz can be quite compact & high gain

I'd park X-Bee at this stage- just initially get a feel for things with some dead simple 315/433 MHz simplex devices. As you'll probably need duplex eventually (if only for furnace fail safety!) perhaps later consider the likes of the US$30-40 a pair Sure/Appcon modules below. These are the present flavour of the month for more demanding wireless work, but for raw beginners I'd again suggest that cheapie simplex TX/RX modules are used. Stan.
 

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Dippy

Moderator
I'm sure if you've read the data sheet AND are happy with SMD work then you'll find them as easy to use as any dumb module. Looks non-smart simple OOK.

I've never used them and don't recall anyone here using them but the spec looks OK, but they're not much cheaper than XBee are they?

I'm not sure about size requirements but I'd have also looked at the Alpha range from Quasar. One thing about Quasar (RF Solutions) is excellent support. It's so much nicer to get information direct rather than (sometimes) Forum guesswork.

The only trouble with choosing new-to-the-Forum devices is that you'll have to hope that people are happy to spend hours helping you.
 
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manuka

Senior Member
I know of those LINX modules, & they are rumoured as OK performers, but- YET AGAIN - I stress that they are likely to be far too complicated for raw wireless beginners. HAVE YOU ACTUALLY READ WHERE WE'VE REPEATEDLY SAID THAT YOU-SHOULD-START-REALLY-SIMPLY ?

Check Sparkfun's TX & RX -well known as cheap & cheerful wireless starter modules (~US$4 each)

P.S. Start simply!
 
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moxhamj

New Member
Re manuka "All do-able. HopeRF have rather been usurped by Sure offerings in fact. Accton Open Mesh WiFi units may suit as well - Andrew Hornblow has hacked into their (undocumented) serial port to good effect."

Hmm - that is an interesting find. At $20 a node, that might be cheaper than serial modules? Ok, maybe not quite the range, but perhaps antennas can be used to effect? I was thinking about serial to ethernet devices to interface to picaxe, but you say that Andrew has hacked a serial port. Please tell us more!
 
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John West

Senior Member
The web site of Max Carter might provide you with the heart of the PC/PICAXE/temperature reading code. Take a look here:
http://maxmcarter.com/picaxe/picaxe_server.html
He's new to the PICAXE - but he's careful and thorough in his work and publishes all of the details of it.

All the comm gear I've played with is of the 25W-200W variety so I'm not much help with the small data modules - but some of these other forum fellas are real experts with them. Their advice is well heeded.
 
lbenson

lbenson

Senior Member
XBee and other smart modules would be better than dumb Rx and Tx at assuring that what is transmitted from A is received at B, but the picaxe code is just about as complex in either case, and has to do with what happens when A transmits and B doesn't receive.

So the protocol is something like, A sends to B, B replies, "you asked me to do this". If A doesn't get that response back, or the response is wrong, it transmits again until it gets the proper response, or times out and sends you a message saying that something is wrong. A single character, or two, would suffice for what you have said you need. When you get the gear, there are additional useful transmission techniques with which we can help you

No point other than educational, I would say, in using anything other than the dumb Sparkfun 315mHz or 433mHz RX & TX modules, or similar.
 
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manuka

Senior Member
Henchman: Glad things worked well,but is that $5 a typo? They're normally more like US$30 a pair!
 
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Grogster

Senior Member
I'm a big fan of the Sunray RF modules at the moment:
http://www.sunrayrf.com/product_SHOW.asp?product_id=44

These things are competitively priced(US$23 each), although a LITTLE more expensive then the HopeRF units, they are 10mW output, can work from 1200-19200 baud(you specify during your order), have selectable channels, HAVE TWO COM PORTS(A TTL port and an RS232/485 port) - A big bonus that many modules do NOT have. They also have healthy ~118dB receiver sensitivity, which will help you get quite a long way over more powerful units with less sensitivity.

With a pair of these, setup one end using the TTL port, and the other using the RS232 port - no additional external level correctors needed, you can pump the data stream directly into the computer COM port. :)

With a high-gain external aerial up high on each end of these things, I have been able to get upwards of 2kM from them, or about 300-600 meters using smaller indoor whips "Through walls".

Their customer support is some of the best I have ever seen anywhere, even to the point of e-mailing ME to ask how I was getting on with them - fantastic.
 
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Grogster

Senior Member
No so far as I know, but they do have a sleep function. Much like the Xbee, you have to know when you want to put it to sleep, and when you want to wake it up again - the data stream won't do that for you, as I understand.

That's normally not a major problem though, as if you are wanting to suck(receive) data, then you know you want to, so can wake the module first. Likewise with pumping(transmitting) it out. Forgive my colloquialisms...
 
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Dippy

Moderator
Yup, looks good enough to flatten Freeview in UK.
In fact I think that would be illegal in UK.(Max 10mW @ <10% duty is that right?)
If my neighbour buys and uses one of those I will burn his house down if he transmits during the repeats of Monk ;)
 
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Zizka

New Member
Dare I suggest a professional module ? TDL2A by Radiometrix ltd (UK based, but distributors world wide). A 433MHz band radio modem with 9600 baud serial port interface. Very, very easy to use: just squirt data at it from the UART. http://www.radiometrix.com/content/tdl2a

(but I'm biased: it's my design)
 
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moxhamj

New Member
Nice design. I spent a little time browsing the rest of the site. Some interesting modules, including this one http://www.radiometrix.com/content/tdi2-1 which has a standard D9 connector.

I've been deep inside code for a long time now, but I did have an 'ah ha' moment yesterday when I used a 9600 baud radio modem to open a text editor on a board in another room and edit a tiny text file. Data transfer is via packets but this is transparent to the user.

For that sort of thing you need 100% reliable links, and I think this is where more expensive modules are worth the extra money.
 
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alistairsam

Senior Member
Hi,

I'm trying to build a simple remote controller for two stepper motors using wireless and have ordered the following transmitter and receiver from sparkfun. datasheets at the bottom of the pages.

http://www.sparkfun.com/commerce/product_info.php?products_id=8950
http://www.sparkfun.com/commerce/product_info.php?products_id=8946

I have found a lot of info on wireless in this forum, but just wanted to know the correct approach to my application.

the remote will have 6 momentary buttons and one toggle switch. I need to raise one of 5 pins on a 28X2 picaxe high at the receiver end depending on which buttons are depressed or turned on and set that pin low if the button is restored.

I also wanted to know if I can use one transmitter and two receivers where the second receiver / picaxe responds if one of two seperate buttons on the remote are depressed. this in turns controls another stepper.

so to indicate that a button is depressed, at the transmitter/picaxe, do I just monitor its input pins in a loop, and if high, send a serout number and if low, send another number? and then based on the number received at the receiver end, raise or lower the appropriate pins?

what would be the correct approach for these switches and would I need CRC check or manchester encoding for data integrity? I can then attempt to write the code.

the range is very small, around 10ft at the most. its for a telescope.
 
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