Controlling bots with bluetooth

I have wanted to switch to 2.4 ghz for a while, spektrum stuff is too expensive for me so ive been looking into bluetooth control, i want to use a 100 M bluetooth dongle with my laptop and a usb game pad or joystick or something for the controls , and a for the Rx , a serial to bluetooth adapter , an arduino and a custom made pcb to interface up to eight servos with the arduino. Bluetooth is spread-spectrum , like spektrum radio's so as far as i know there shouldn't be any problesm , but the FRA rules dont actually say that bluetooth is allowed , so does anybody in the know , know if bluetooth is ok, and if my plan is doomed to fail ?

any help would be good :)

Bluetooth is 2.4GHz and digital and therefore covered in the rules and regulations. However, you will have to demonstrate that the failsafing works and that your implementation doesn't interfere with other systems on the band (which is very unlikely).

I was going to do failsafing in the software , will that be ok do ya think? Im pretty sure the failsafes in my esc's wont work with this as i cant directly emulate an RX , just tell a servo to go to certain position

That's what spektrum does as well in their receivers (except the AR500) that is why failsafes are useless in Spektrum driven robots.

bcause the receiver has a brain im hoping that , as it wont know if its lost connection , it will just stop working , it will just give no instructions to the esc's , at which point the failsafes in the esc will kick in , im thinking of bypassing the whole analog to digital to analog again thing and just feeding the raw data straight into the esc that way there would be no need for any failsafes and it would be a lot safer

Failsafes, mean for a robot point of view that it must come to a controlled stop when loss of radio signal is detected. This also applies to any weapons in that they must not activate unintentionally. It does not matter how you implement this as long as it works and can be demonstrated during tech check. From your point of view this could be demonstrated by unpluging the bluetooth adaptor from your laptop while driving/turning at full speed. If it then stops all is well.

I would also check that Bluetooth is allowed for remote control (though I cant see why it wouldn't be). I know that 433MHz tranceivers that are very cheap (<£10) seem a good idea but regulation don't allow for control but just telemetry of data as I looked at this a while back for another project.

I would still recommend you look at a Spectrum system, they are really not that expensive (dx5), espacally if you take into account of the 2 bluetooth modules and the joystick you need, unless you have a cheaper source than me.

That's way, way more effort than just getting a Spektrum dx5e or whatever off ebay.

I agree it is a lot of hassle and I'd rather buy a DX5 as well, but the question was whether it is allowed or not. I opened up the build rules to make sure before I answered and I see nothing in those rules that would exclude Bluetooth.

I agree with Leo, there is nothing in the build rules that excludes the use of bluetooth as a control medium. However, you will be required to demonstrate it's ability to comply with section 4.2 of the build rules.....


4.2.1.
All systems that are deemed to be 'dangerous' (normally the drive and weapons)
must have a 'failsafe' device. This MUST bring the systems to a pre-set 'off' or 'zero'
position if the transmitter signal experiences interference or is lost. These devices
should also failsafe when the receiver battery is low or if power is completely lost.
4.2.2.
The failsafe(s) may take the form of plug-in commercial devices; electronic circuitry
incorporated into some receivers e.g. PCM type; or other devices e.g. electronic
speed controllers such as the Vantec. It could also consist of digital switches, which
return to preset off position on loss of power. Care should be taken in the selection of
devices to ensure they meet the requirements specified above.

Providing your bluetooth set-up can comply with the above then I see no problem with your plans.

Geoff Smith
FRA acting safety officer.

I did a bit of research into this myself a while back and came to the conclusion that it had already been done so there's not a lot of point re-inventing the wheel.

One of theguys who's done it is here and if you scroll through the thread you'll find most of the software and stuff.

http://www.rcgroups.com/forums/showthread.php?t=801036

We haven't sat down and put any of these together yet but we were thinking that the modules would replace the mosfet drivers as you can get a pwm output from them rather tan using a driver.

Would be nice to know how you get on.

Andy

Just my 2pence worth .......

While bluetooth is 2.4 ghz , there are a lot of mobile phnes at the shows and i dont know if you could be in sole control of the robot via bluetooth as i sure it would get mentioned and someone in the crowed would be sure to try and have a go with there phone ... this doesnt happen with the spectrums ...


Just a friendly comment (and something to test against )

Basicly , i like a challenge , i know i could get a spektrum system for the same price , but thats no fun.

when you pair with a bluetooth device , like wifi you have a pre shared key , and as long as no one in the audience knows this , they can t control my bot, even then they would have to guess at my control protocols, as its pear to pear so hey cant monitor it.

I ahve come across that thread before , but with that setup i cant have the degree of control i need and i am limited to 2 channels.

I would like to cut out the laptop, as its just too much to go wrong and too much to setup, so now ive established that its within the rules, does anybody know if its possible to create a wireless serial link between 2 adapters, cuz no where on the interent says that you can get 2 adapters to connect and pass serial information without a pc in there somewhere.

Sussex models is selling the Planet 5 2.4Ghz Transmitter & Receiver Set for £36 which they describe as:
Advanced 2.4GHz 5-channel professional transmitter and receiver
Includes
2.4GHz 5-channel professional transmitter
2.4GHz micro 6-channel receiver

I know nothing about this gear, just saw it on their site, but for £36 it has to be the cheapest 2.4 GHz control you are going to get.

Quote:

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Originally Posted by muchalucha

I ahve come across that thread before , but with that setup i cant have the degree of control i need and i am limited to 2 channels.

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It's sixteen pages of thread I know but it does get a bit more advanced as he gets to know the software and also gets manages to get it set up with the Wii nunchuck controller. That said sure there will be a lot of mods to any software you get but it's a good start.

Pete,

Spektrums use bluetooth technology basically there's nothing special in them. It's the same type of thing you get with either a wii controller or an xbox 360. It's just a 2.4ghz module on a circuit board, if someone wanted to they could simply take the rx apart read the software and stick it on another module. That would obviously not be particularly legal but is not really that hard.

Andy

Quote:

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Originally Posted by john_frizell

Sussex models is selling the Planet 5 2.4Ghz Transmitter & Receiver Set for £36 which they describe as:
Advanced 2.4GHz 5-channel professional transmitter and receiver
Includes
2.4GHz 5-channel professional transmitter
2.4GHz micro 6-channel receiver

I know nothing about this gear, just saw it on their site, but for £36 it has to be the cheapest 2.4 GHz control you are going to get.

---

OMG , live about a minutes walk away from smc, thanks :)

Quote:

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Originally Posted by muchalucha

Quote:

---

Originally Posted by john_frizell

Sussex models is selling the Planet 5 2.4Ghz Transmitter & Receiver Set for £36 which they describe as:
Advanced 2.4GHz 5-channel professional transmitter and receiver
Includes
2.4GHz 5-channel professional transmitter
2.4GHz micro 6-channel receiver

I know nothing about this gear, just saw it on their site, but for £36 it has to be the cheapest 2.4 GHz control you are going to get.

---

OMG , live about a minutes walk away from smc, thanks :)

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If you are going to buy one of these, ask first if you can test its failsafe capabilities. When you switch off the transmitter the robot must stop working and a lot of these transmitters the channels will just continue doing what they were doing until the signal comes back.

my escs have built in failsafes

The failsafes still won't kick in if the reciever keeps giving out the last valid signal it gets, you need the reciever to either have built in failsafes or not give out a signal when it loses contact with the Tx.

thats the plan :P