40MHz to 2.4GHz conversion

[RogueTwoRobots]

Greetings all,

As we all know, from 1st January 2011 all featherweights must be run on 2.4GHz transmitters and for some of us, that means our 40MHz units becoming pretty redundant. This was something that sat a bit uneasy with me because, as I have mentioned before, I'm quite partial to my Skysport 6 transmitter that I've had since getting into robotics. I also have a good quality Field Force 6 that I was contemplating putting on eBay as it wouldn't be able to be used.

There was the argument that switching to 2.4GHz shouldn't be too much of a problem as you can pick up sets for as low as £25. Fair enough, but that gets you a simple 4-channel no frills handset. If you wanted to replace your spiffy 6 channel set with built in mixing, model memory etc you'd have to fork out significantly more.

But not anymore...

For those of you who are already aware of this, the following won't really be a surprise but I only discovered this a few days ago so I'm still quite excited about it
I'm talking about a 2.4GHz conversion kit that you can wire into your existing FM transmitter so that it operates on 2.4GHz. I was sceptical when I first read about it but having watched a few Youtube clips and read several forums it seemed relatively easy and pretty reliable; as reliable at least as the £25 budget 2.4GHz sets.

The set I'm using is a Corona 2.4GHz DIY module conversion kit from GiantCod RC: http://www.giantcod.co.uk/corona-24ghz- ... 04735.html

I've just finished converting my Field Force 6 and so far with a servo bench test, it works a treat! I was going to do a bit of a write-up but I've not taken the best pictures and I'd probably write waaay more than is needed, so here are the links to a couple of forum threads I found quite useful. They're not all about the Corona make (some mentions are made of a more expensive equivalent, Assan) but there's enough essential information contained within them all:

http://www.rcgroups.com/forums/showthread.php?t=878096
http://www.rcgroups.com/forums/showthre ... hlight=ff6
http://www.rcgroups.com/forums/showpost ... ostcount=8 (the one I've just followed)
http://www.rcmf.co.uk/4um/index.php/topic,72702.30.html

Here are the pictures from my conversion:

Contents:


Main module with bind button/LED. The three tinned wires at the top get connected to the positive, ground and PPM wires in the transmitter. The easiest point of contact to find these is the trainer board:


The three wires soldered on to the back of the trainer board. I've fitted a small switch in between the PPM line so that I can switch the unit between 2.4GHz and 40MHz (should I need it):


The co-axial cable fitted to the black stubby aerial, which has been mounted in place of the original metal telescopic aerial. The co-ax cable needs to be soldered on to the module board at two points (the inner conductive cable and the conductive cable that runs over the insulation of the inner cable. A bit confusing but it is explained more clearly in the above forum threads):


The transmitter bind button and LED mounted in place below the trainer port, along with the rather crudely hot-glue mounted switch above it:


And the completed unit:


Unbelievably easy, and you still retain all the functions of your radio as features such as mixing and dual rates are done in the transmitter before the signal is sent to the receiver.

Notes: to use on 2.4GHz, the crystals must be removed from the transmitter. The bind procedure is a bit long-winded but explained moderately clearly in the instructions. You have to press a button on both the transmitter and receiver, unlike the Radio Link units, so this may prove to be a more solid connection as a result and might not get drowned out when other 2.4GHz units are being activated (only time will tell). The receiver does have a failsafe function but some reports say that it 'forgets' the failsafe positions after it has been turned off and on again. This is something that I will need to play about with. If I don't use the failsafe feature in the receiver, I am hoping that the receiver outputs nothing on signal loss so that external failsafes can be fitted.

I'll pop up another post when I've tested that and given it a run out in a robot to test its range. Unless there are any major problems with those aspects, this could be a very cheap way to re-use radio systems that could otherwise have been getting relegated to a cupboard or eBay.

Any questions, I'll do my best to answer them based on what I know/learn.

[team_orr]

this looks very interesting jamie, i was in a bit of a fix trying to figure out what to do with my 40mhz set (which i use often in my robots) my transmitter is breathing a sigh of relief do you think it would make a differnce if there was a buddy box installed?

[gravity]

yeeeeeeeeeeeeeees !

so now I can go back to my beautiful multiplex mc2010 !!!

bye bye dx6

edit : would this perhaps work with a spectrum br6000 RX ?

[rallikas]

edit : would this perhaps work with a spectrum br6000 RX ?

99% NOT, using other manufacturer systems together is quite discussed topic, but it dont work out.

[rallikas]

Actually this kit is originally sold by hobbycity! http://hobbycity.com/hobbyking/store/uh ... 28DSSS%29_

I have been using my diy kit in hitec optic 6 SPORT for a while now, and it works well!! I have tested it on planes, cars, boats and robots, works well on all models. Havent had a single glitch so far!
I completely removed the internal 35mhz module from the transmitter and replaced with the 2.4 one.
You cant go wrong for the money!

[terry]

ive been reading some feedback from users who have used this kit and am a bit concerned about this-

Once the TX and RX have been turned off it can take a couple of minutes to rebind. Turn the RX on first and then the TX on after 10 seconds if they do not bind within a minute or so turn the transmitter off and then back on again, if this fails turn both TX & RX off and start again.

isnt this a bit of a pain when arming up ?

[rallikas]

I turn on the TX before and it binds with 2-4 seconds. I dont get why people have so much trouble with the binding, mine works perfect!

[RogueTwoRobots]

Jack: I can't say for sure if having a buddy box installed would make a difference. Does yours plug into the trainer port? I have a buddy box for my Skysport 6 (up next for conversion) but mine doesn't plug into the trainer port so will probably be unaffected.
Effectively you're just making a second connection to the trainer ports and then switching between the frequencies (if you install a switch) so I would imagine the buddy box would function as normal, but I don't know what the wiring and connections are for a buddy box connected through the trainer socket so don't take my word for it.

WJ: As Mart mentioned, most probably not. People have tried it but with very little success. 2.4GHz definitely doesn't seem as component compatible as FM was with regard to using different brand receivers etc. If it's any help though, the kit does come with an 8-channel receiver included, with 6- and 4-channel rxs available for roughly £10.

Terry: I had a similar scenario when mucking about with mine last night but I was still getting used to it at that point. When it did bind, it did so very quickly (in about the same amount of time as it takes a Spektrum to connect) in the same way as Mart's; I'm going to fiddle about and work out what combination of turning on/off the transmitter/receiver it seems to like the best, but it seems that the standard operation (tx on, rx on) works well enough.

Will have a play around with it more and post any findings.

[typhoon_driver]

I'm watching with a lot of interest!

[RogueTwoRobots]

Well gave it a bit of a test today in a robot. I couldn't get a good long-range test, but of the distance I did get there were no problems. Controlling your robot when it's at the far side of the arena shouldn't be a problem.

Failsafes: you can set failsafe positions in the reciever when you power up in a certain way. I haven't done this since getting the kit but I ran through a typical failsafe check (fwd-off, back-off, left-off, right-off, weapon-off) and it performed flawlessly. I expected that on the drive as it was two Electronize 30A controllers that have built-in failsafes. But the weapon was on a 15A Electronize, not the good 15A ones, but one of the cheaper 15A ones that has a lower quality of control. This definitely doesn't have a failsafe built in but the weapon came to a stop every time. It takes around two seconds after turning the transmitter back on before the receiver reconnects (much like you get on a DX6, from what I've seen).

Now this is the issue that could sway you if you're deciding whether to purchase the kit or not. I was using a separate receiver battery, so the arming up procedure was tx on, rx on, link in. But when I did this first time, the tx/rx didn't connect. I turned the rx supply off and on again and this time it worked. No problems after that; I turned the tx off numerous times during failsafing and it always reconnected. But if you're using a BEC, the rx off-on is replaced by taking the link out and putting it back in. It's your choice to decide if that's a niggle you could put up with.
Some people say you need to power up the rx first, before the transmitter. Again, if you're using a BEC, this means putting the link in before turning on your tx. I don't know if anyone already arms up like that, but I'm not sure what an EO's take on that is. Should be safe since the robot should failsafe but sometimes when powering up the drive motors can spin briefly or something else can turn on for a second, so maybe best to check with the organiser.

I'll be running this setup in Drumroll 2 at the champs and will have a separate rx battery so that I can get the radio system sorted and settled before powering up the robot. While the test today has been useful, I'll learn a lot more once it's been through a weekend of combat.