Distributor

Hello, I'm looking for a little help / guidance with wireless telemetry.

 

I would like to add the wireless telemetry to my APM to use with the GCS, as I live in the UK I can't use the Xbee 900's as this is the band used by the mobile telephones here. I have a 2.4 Ghz Futaba T7C so I can't use the 2.4 Ghz Xbee's either. My thoughts are to end up using a 5.8 Ghz video link 2.4 Ghz radio and I hope the 433 Mhz telemetry.

 

I have seen this post in the Arducopter section of the DIY drones site, there is talk of using a 433 Mhz link, which I understand will work using these Wireless 1 & Wireless 2 it looks like one for the connection to a PC and the other for the APM. I have also seen other posts talking about these as an option on the forum but none of the postings answer the following question / concern:

 

Reading all the posts it would appear as if it is not to complicated, however as I don't have a great deal of programming experience or a massive background in electronics would I be opening a can 'o' worms which I could not deal with by going forward with this? Could you point me towards a set of instructions to make this work? 

 

I hope someone(s) will be able to help me with this.

 

Regards

 

Martin.

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  • Distributor

    I have just spent about 1/2 an hour looking on the web to see what people are saying about the real world use / range of these units, I can not find one entry about the max range people are able to get, there is talk about the power being to much at close range, so they have had to move the units some way from the "base" unit to get them to work even at low power, approx 10 meters +. I would have expected to find a lot of “I have poor range” posts if they are no good, I did not see any of these either. Only the duty cycle popped up from time to time, but we know all about that. One other thing I saw a few times was the data rate will need to be 9600 when at long ranges, apart from those points I really can’t find any bad reports.

    My thinking is, if the data sheet states it will do 40-80 km with LOS then I would like to think it will do 10+ km without any real issues, only real way to know is to use them, plus there are no other options that even hints at these ranges. The units we started looking were 800-1200 meters max!

    For my use a few km's will be more than enough, I think for your needs out in the "bush" you will have no real issues with the range, but the only proof will be by testing in the field.

     

     

  • HI Martint, Yes the duty cycle can be got around by simply applying a low signal on the reset pin. The signal only needs to be very short and the units connect again straight away. The 10% duty cycle is fixed an cannot be changed but please bear in mind it's purely dependent on how much data your pushing through and at what rate. In my case I use 9600 bps and get around 40 mins before it needs a reset but since my lipo only gives about 30 mins max I have not even bothered putting any resetting circuit on the airframe and have flown my plane all summer on nothing but the 868. I'm also using mine for servo control from a joystick so it was critical the units didn't lock. The 6 Mins I presume is using the maximum data rate with a constant stream of data. Even this was your requirement using a simple external circuit to reset the unit every 5 mins or so would solve it. The 10% duty cycle seems like it would cripple the usefulness of such a device but to be honest I found it wasn't too bad and given that we have limited options here in the uk regarding good kit it seemed the best of a bad bunch.

    Cheers,
    James

  • I Tried the easyradio LPRS 433 modules last year and had nothing but trouble with them regardless of what baud rate I used. After having many unexplained nose dives or sudden climbs at different flying locations I decided to put the easystar back on the bench and run it for a while. When the brushless motor was running the rudder and elevator would randomly move to their full extent and stay locked for couple of seconds before returning back to where it should be. The radio and  servo controller were on a totally different Lipo and BEC to the ESC. My GCS data would also be way out from time to time. I might have just been unlucky with my modules but in the end I changed it to the Xbee868 and have never had any problems since. Duty cycle needs a slight work around but from my experience it was worth the effort for stability.

  • Hey,

    I'm located in teh Netherlands, and faced with teh same issue. I was considering to buy this kit: http://www.yerobot.com/shop/communication/apc220-radio-communicatio... (Working frequency: 431 MHz to 478 MHz)

     

    I read positive responses about these transceivers (http://diydrones.com/forum/topics/found-433-mhz?commentId=705844%3A...)

    as opposed to the xBee 868 (http://diydrones.com/forum/topics/where-to-buy-xbeepro-868?commentI...)

     

    Alternative would be xBee Pro 2,4Ghz, but like you said, that may conflict with your rx/tx and is a whole lot more expensive (around 36 pound per unit).

     

    I guess I'm just going to buy the APC220... although the shop doesn't look all that trustworthy, but it'll probably be fine =]

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