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Author Topic: Best Wireless R/C techniques/solutions ??  (Read 1628 times)
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Poperinge, Belgium
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Hi All,

My son and I finally decided to design and build our own FlyBot.
Currently we are shaping the specs and solutions we are going to use
keeping an eye on the cost :-) (For kids the sky is the limit ... but for
my bank account.).

That said. we are tempted to also build our own R/C based of the Arduino.
As I am and IT professional I'm tempted to use WiFi for the wireless communication.
However I know there are other Wireless R/C technologies out there and
perhaps those are better suited for R/C (Like RF22).

Any suggestions...

Kind regards,

Peter

-------------------------------------------
So many ideas, so little time.
Why buy if you can build it.

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Seattle, WA USA
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Quote
Why buy if you can build it.
Because you get what you pay for. Some things are worth paying an expert to do.

Quote
That said. we are tempted to also build our own R/C based of the Arduino.
As I am and IT professional I'm tempted to use WiFi for the wireless communication.
However I know there are other Wireless R/C technologies out there and
perhaps those are better suited for R/C (Like RF22).
The best technology depends on the data that you want to send. Let's see. Hmmm. No, no requirements or specifications defined anywhere.

I thought you said you were an IT professional...
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What sort of range are you looking for?

What sort of data are you planning to send, and in which direction?

Whereabouts will your bot operate - indoors, outdoors?

If you only plan to use an ordinary RC handset and control the 'bot manually, I've have thought that an off-the-shelf RC system was a no brainer. But if you plan to connect your bot to a PC, bluetooth or WiFi may make more sense. But you'd need to provide a lot more information about what you want from the link, to make a sensible decision.
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Poperinge, Belgium
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Hi PeterH,

Thanks for the rely. I hope I can clarify my first post for you, so here goes.

The 'spirit' of my post was to gather information on technologies related to short-range (<2km)
wireless communication. Wifi being one example, and RF22 being another.
I was not requesting for a ready to use solution, all I wanted where suggestions ....
I deliberately left out any specifics as they tend to cloud the answers. If I suggest details
chances are the the feedback would be biased, related to the my suggestions, making my request
null and void ... sadly that point got lost in translation.

The plan is to also build a remote control handset, based of the Arduino. The prime reason
being for the fun and experience, but also as I feel it will allow greater flexibility. If we buy
an Off-The-Shelf remote controller it will limit the possibilities for hacking and modding it
with new features we come up with, hence another reason the make the controller as well.
But this brings the technology for wireless communication into the foreground.

I just wanted to find out it if there are 'other' alternatives to Wifi for sending and receiving
control and/or telemetric data between the controller and the Bot and vise versa. I was just looking
for directions or pointers to other Off-The-Shelf technologies. Based on the gathered information I was
planning on compiling this data into at document describing the various pros and cons and their
suitability for indoors/outdoors amongst others.

For instance WiFi has a 'suitable' range and latencies in an ad-hoc WiFi Network. It is easily
available as modules for the Adruino. But it uses the overly crowed 2.4GHz range, which could
make it subject to unwanted interference.

Bluetooth, is also usable but has a very close range.

RF22 looks currently to most promising. It uses other frequencies from the 433/868/915MHZ bands
and is available in a high-power modules of 500mW output power and reaching ranges of up to 2km (1.5Mi).
I'm currently looking at the Hope RF RFM12BP module.

On a side note:
Sadly even here there are some people that can not read and/or deduce information that is not explicitly
mentioned and have an unstoppable urge to make themselves noticed by blatantly belittling people.

Kind regards,

Peter
« Last Edit: January 18, 2012, 03:51:32 am by pdepuydt » Logged

Seattle, WA USA
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If I suggest details chances are the the feedback would be biased, related to the my suggestions, making my request null and void ... sadly that point got lost in translation.
I'm not sure how specifying the range, that would eliminate recommending something that does not meet the range requirement, nullifies any recommendation that does.

I'm not sure how specifying the amount of data, that would eliminate recommending something that does not meet the volume requirement, nullifies any recommendation that does.

I'm not sure how specifying the type of data, that would eliminate recommending something that does not meet the type requirement, nullifies any recommendation that does.

There is a big difference in radios that can transmit 20 bytes a minute over a distance of 30 feet and ones that can transmit 2M of voice quality data 2000 miles.

Something got lost in the translation...
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Poperinge, Belgium
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Hi Paul,

First, to bad we seem to have started off on the wrong foot.
Forgotten and forgiven.

Allow to clarify my objective.

Objective :
The design and construction of a remote control device based upon Arduino with the explicit aim to use
it to remotely control ROV's (air/land/water based). The ability to send commands to the ROV for steering
and de/activations of functions. Have the ability to receive telemetry from the ROV and display them on a
screen on the remote control( such as sensor readouts, battery status, etc).

The only weak spot I have is the selection of a suitable RF data transmission technology. One could indeed
use Wifi, but it has probably a to a limited range and might not meet the latency accuracy needed ?
 
Specs:
Range : <1000m outdoor
Latency: <2ms
Bandwidth: >= 2Kbps
Direction: bi-directional, preferred for telemetry feedback.
Freq.: Preferably not 2.4GHz ... (potentially subject to interference ?)

Currently I'm looking a transceivers from Hope RF, namely the RFM12 series http://www.hoperf.com/rf_fsk/cob/RFM12.htm
and it is supported by Arduino http://www.open.com.au/mikem/arduino/RF22/

I know there are still other considerations that need to be cleared, such as which Arduino to use.
Chances are the UNO could lack some processing power to control the transceivers.

If you have any experience that could help me avoid common pitfalls I am very much interested and it will be very
much appreciated.

As I have stated before, I do not yet have a detailed end-result in mind. I have an idea and am trying to figure out
what the feasibility boundaries are. Data transmission is just one of them. This is a true father/son project, and in
case you have kids you'll understand what I mean Father build, son creates the feature requests and plays :-D

Hope this clears the air,

Kind regards,
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Seattle, WA USA
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I don't see anything in your requirements that couldn't be satisfied by a standard RC transmitter and receiver - at least the high end ones.

You don't describe what is being controlled by the receiver, but if that includes any servos, something needs to keep refreshing the servo signal. That could be an Arduino on the receiving end or it could be the RC transmitter/receiver.

http://www.futaba-rc.com/systems/18mz.html is an example. It allows you to add additional bi-directional data transmission for additional sensor feedback.
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Poperinge, Belgium
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Hi Paul,

Basically I would like to have 2 (or more) Adruino's to talk to each other via an RF link.
The receiving Arduino would the execute the command specified.
These could be servo's, motors, lights, pumps, sensors, basically anything.

Granted wifi is by far the easiest and most convenient way to do this. My concern here
was whether is would be suitable for time-sensitive remote communication. Kinda like
the jitter problem with voice comm.

However if people have good experiences with wifi I good with that too.

As I understand it there are standard RC transceivers modules on the market, there have to be
since a lot of people use such a high RC to control the remotely operated arduino's that way.
Since I do not own such a remote controller, I thought I'd build one, I would just need a second
transceiver, arduino and create some code (simplified description) ...
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@pdepuydt
I've used the RF22 and that lib. It's a good transceiver and a great lib.
However with a breakout board it becomes a little more expensive.

You also might consider the nRF24L01 2.4 GHz transceiver and the RF24 lib.
They are cheaper, more mountable, and you have options on range vs. cost. The higher freq may have advantages too.
You can get a good intro on them here. There is also a thread here.
 
(FWIW I think most people understand your strategy about starting with a general question.)
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Range I see as the biggest issue. If you're aiming for up to 1000m range that is way outside what I'd consider easily achievable with bluetooth, WiFi or nRF24L01. I don't know what the range of a modern 2.4GHz RC system is, but back when I played with the old fashioned 27/35 MHz systems they claimed 800 m range in ideal conditions but I don't think I ever got anywhere near that in practice.

In general you can increase radio range considerably by using a high gain antenna and/or power amplifier, but non-directional antennas tend not to be high gain and I can't see directional antennas being feasible in this scenario.

So I suggest trying to pin down your range requirements more exactly, in particular to what extent you're willing to compromise the range requirements in order to get an easier solution.
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Poperinge, Belgium
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@Hogan,
What are your experiences with the RF22 ? Looks like the RFM12B module is cheaper than the the RF24.
There is high-power version as well 500mW RFM12BP and according to EU regulations I could find, it is
allowed @ at 500mW between 869,400 and 869,650MHz. Not sure though is the 250KHz bandwidth is enough.

Thanks for the info links.

@PeterH
I feel the wifi range would be to short. Most wifi's claim 300m ... but at that distance there are a lot
of lost packets. If I could get a decent reliable signal up to 500m I'd be very happy. Hence the <1000m on paper :-)
We all know everything looks good on paper ...
 
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I like xbee because it's well supported and very easy to work with. Not dirt cheap and i don't think 1000 ft is realistic.
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Denver
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pdepuydt
The project I made using the RF22 is here. You'll see it's quite different from yours. I had good comm (RSSI ~100) from my backyard to the far corner of my basement. Even so, there are occasional "no ack received" errors. Not critical for me, but you should plan for that type of problem no matter what transceiver you end up with.

This weekend I will re-do the project with this nRF24L01, so I'll be able to compare. I popped for the best version because antennas are a black art to me and I wanted the amps. The one review on that page claims 100M.

I suspect that 2.4GHz may excel over 433MHz for line of sight, and with many channels to choose from, and carrier detection, interference can be avoided. I'll know more in a few days and will update that project page.
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@Hogan,
What are your experiences with the RF22 ? Looks like the RFM12B module is cheaper than the the RF24.
There is high-power version as well 500mW RFM12BP and according to EU regulations I could find, it is
allowed @ at 500mW between 869,400 and 869,650MHz. Not sure though is the 250KHz bandwidth is enough.

Thanks for the info links.

@PeterH
I feel the wifi range would be to short. Most wifi's claim 300m ... but at that distance there are a lot
of lost packets. If I could get a decent reliable signal up to 500m I'd be very happy. Hence the <1000m on paper :-)
We all know everything looks good on paper ...
 

For good, but still cheap, long range wifi, try Ubiquiti (www.ubnt.com) Their omnidirectional PicoStations are small, and the spec sheet says 500m range outside (clear Line Of Sight). If the pico doesn't cut it, you can try a nano, or rocket with an omnidirectional antenna on it. If you can deal with a directional antenna, they have some radios that have been used in 50 mile point to point setups (mounted really high up to clear the fresnel zone, and with 100% LOS obviously)

They also offer most of their radios in both 2.4GHz, and 5ghz, with some others at 900MHz.
« Last Edit: January 19, 2012, 10:58:49 am by wizdum » Logged

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