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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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 =]

Hi Johann,

 

I hope you are enjoying your stay in the not so warm northern hemisphere :)  What part of SA are you from?

 

The short answer is yes to the 433, they seem to have a good range from what I have been reading. I also have seen this post that looks like it may offer even more that the links I posted at the top of this page. I had a look for the parts as listed but could not find them, part number may have changed on the HAC :(

 

I know I could go back to the older FM Tx, but I went for the Futaba 2.4 Ghz on the grounds that I have lost planes due to other people turning on their Tx with the same channel I was already flying on & had many glitches which made your heart stop every time you lost control if only for a second or so. 

 

I have seen the LRS on here as well, the other one I looked at here is a lot of money and seems more FPV than UAV.

 

I do hope a few others pitch in with some thoughts on this, as I'm sure we are not alone!

 

Regards

 

Martin.

Hi Serge,

 

They look different to the ones I linked to at the top of the page, these look like the ones you linked to here, there is also a data sheet for them that I found here, I would check that they are the same ones Johann & I were talking about above.

 

Regards

 

Martin.

The modules mentioned above are quite low data rates - 9600. I've used the Easy Radio series of modules up to 19200, they are easy to use, operate over 3.3v to 5v and give reasonable range in the 433 band.

 

Peter

@Martin,

thanks for the note. I checked a bit, and think they are similar, although I'm not completely sure, but they are both APC220 and look identical. The ones I previously linked to are indeed different.

 

@Peter,

I read in the manual that the baud rate goes up to 19200 ( http://www.yerobot.com/products/manual/APC220%20Mannual.pdf )

Although, it also states: "Transmit distance up to 1000m (line of sight) @9600 bps". So that would mean that teh range drops as bps increases? Can anyone explain me what the relation between range and baud rate is?

And what are the drawbacks of having just 9600 bps for telemetry?

 

thanks for all the info, and sorry about teh noobish questions.

Serge

 

Johann I have also seen these, I was put off a little by some information I saw a while back, which I now can't find, there was a feeling that the 1.2 Ghz was going to cause an issue with the 2.4 Ghz as it was a harmonic frequency.

I did find this page, the first video on the page uses 1.2 video with 2.4 radio and looks good even though I have no idea what camera or Tx/Rx was used for the video. I think it might be worth looking into this combo' some more.

I have a good friend who I try to visit as often as possible in SA he is about 15 min's from the Kyalami circuit, I always have to stop by Monte Casino for one of the Meat Company's fine steaks! Oh and I might visit a table or two while there to win the steak money back......

 

Regards

 

Martin

Hi Peter,

 

Thank you for the information on the "Easy Radio", I had not given a great deal of thought to the data rates offered. Do you have a link to your set up we could take a look at? And do you know what a minimum rate should be for a good telemetry link?

 

Regards

 

Martin 

I think that it looks like a great unit, small and it seems to have the range to cover all out comes!

I believe the questions that we need to answer / have answered now:

  • Will it work with the APM & Oilpan?
  • I see in the Spec Sheet there is a note about running a program to allow the use of the TX/RX options on the board (I guess only needed if looking to upload way points while in flight)
  • There is no built in protocol for error checking is this needed? If the Oilpan streams the info there is no need to know the last was correct as there will be another update along very quickly.

Do you think this unit could just be powered and then have the Oilpan put all the information down the TX line?

This is where I run out of knowledge with these things.......

Just finished a few things I had to get done tonight before the snow puts in an appearance here at home, it then came to me that 2500 feet range on the unit we have just been looking at sounded great but that is only 700 odd meters which is less range than the boards I started talking about at the top of this topic, I think it might be that the first option is the better option, they say about 800-1200 meters which is more range (about 2/3 to 3/4 of a mile) your thoughts?

Plus these maybe "easier" to work with ?

 

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.

I don't think for one moment that it would be legal to use the 900 band, and I have a feeling that in most regions around the world where they use the 900 band for mobile phones they will have a much higher powered TX / RX than any xbee we could use on the 90 band, it all comes back down to trust in the equipment you use, I could not trust it, just because it works ok in x location will not mean it will be ok in another.

I think that James may have just given us the info we were looking for, I will look into this in the morning when I have a little more time free, fingers crossed it’s not a restricted band in the UK or SA :)

Hi James,

 

Thank you for joining in on the chat about telemetry and the main options we have been looking at. You have said that the Duty cycle needed a slight work around, is this an easy process for someone who is not the most tech savvy ?

 

Regards

 

Martin.

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