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Homemade On board telemetry System

Discussion about Tx, Rx, Servo's, Batteries, Chargers, and all the other things we like to talk about..
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jimbo
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Location: Cornwall

Homemade On board telemetry System

Post by jimbo »

As a futaba user, 8FG, i have no telemetry!
So rather than spend a bunch on a new transmitter, i thought i would try and build by own system.
So i used a couple of arduinos, one on board and one on the ground.
These are available cheaply on ebay from china for a couple of quid.
I then sourced a couple of 433Mhz transmitters and receivers and a display.
I created a simple voltage divider to ensure that the onboard ADC, of 5V can input a range of 0-20V to measure my battery system. The divider is a 300k and 1M resistor giving a scaling factor of 4.38, so i can read up to about 21.9V without damaging the on board ADC.
Both receiver and transmitter will run on a 3s Lipo.
A little bit of programming using the adruino programmer on the PC and i have a transmitter and a working receiver !
I have tested the range on the ground and i works to well up the street to about 20m plus, so i am hopeful that i can receive some useful telemetry information from on board the model. I also hope that i can add other useful stuff like later GPS, speed, height etc once i have proved the range is acceptable when flying.
I also hope that the 433Mhz transmitter does not interfere with my 2.4Ghz control. I may have to do some extensive range testing on the ground before i risk it in my test model of choice, my swift S1, then my 4.2M asw20.
Last edited by jimbo on 22 Nov 2016, 15:42, edited 1 time in total.
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jimbo
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Re: Homemade On board telemetry System

Post by jimbo »

Arduino transmitter.
The LIPO is power for the transmitter. The Transmitter is bottom right on pic. Eneloop is simulating the receiver battery, in the model i simply plug the plug into a spare port on the reciever. Im using a large arduino (mega) at the moment, i will use a nano ardiuno which is a fraction of the size and weight.
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ard1.jpg
Last edited by jimbo on 22 Nov 2016, 15:40, edited 2 times in total.
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jimbo
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Re: Homemade On board telemetry System

Post by jimbo »

Base station.
I can tell if the link is active with the dot on the right.
It disappears after 1s if there is not a valid voltage received.
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ard3.jpg
ard2.jpg
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jimbo
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Re: Homemade On board telemetry System

Post by jimbo »

Cost so far is about 3 quid for each ardunio 1 quid for the transmitter and 1.62 quid for the display, a few bits of cables and leads.

Sorry links not working, grr
FrankS
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Re: Homemade On board telemetry System

Post by FrankS »

Jimbo, I used the Wireless Co-pilot 433 mhz Vario and Current sensor with both Spektrum and Multiplex 2.4 systems and there was no interference with the 2.4 systems, so i don't think you'll have any issues in that respect.

The WCP current sensor worked well in the models I used it in, the vario was a bit more hit and miss in a glider as the range was much less than the Multiplex M Link telemetry systems.

BTW have you seen the Opensensor forum, I've built their Vario (bariometric sensor and ardunio) to go with my M Link stuff, but for somebody clever than me it could be adapted to work with a 433 mhz transmitter i'm sure.
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jimbo
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Re: Homemade On board telemetry System

Post by jimbo »

Franks, good to hear no interference. Im abit worried about the range as the transmitters according to the internet are a bit limited to a few hundred metres. Im not sure how good it will be if at all. If it runs out of range at 20ft, there are more expensive transmitters available.
No ive not looked at anything online, just googled for a few bit on the arduino so far.
Im sure if i can prove the concept, there is a bucket load i can do once i get a gps on board, this looks pretty straightforward too. I have a ram card to which it can write the gps co ordinates rather than transmit and analyse later to google maps if i desire.
Next task will be to read the speed and height somewhere, perhaps from the gps or some air sensor of some sort, more research required.
Once i start transmitting more data, i will need to write some sort of protocol (yawn), i can put the code up so far if anyone is interested (its arduino C).
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Jimbo,
I looks as if most of the low end 433MHz links are intended for very short range remote switching (e.g. Garage doors etc.) but you can get modules that will work up to 300m or above if you look around.
Robotshop.com have a 2km link pair, but these appear to be very low data rate types (again primarily intendedy for simple on/off control).
However, Futurelec.com market a range of Tx/Rx modules, although with very little documentation to explain how to use them!
It appears that you are likely to need a link budget of approximately 120dB to achieve a 2km link range (antenna dependent) at 433MHz.
Good luck.
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Jimbo,
It looks as if rfsolutions.co.uk have 433MHz transceivers which should be capable of 1-2km.
Their site also has good documentation which can be downloaded, together with example projects, albeit with Microchip devices, but they will give a starter for 10.
Their transceivers are also rather cheaper at just under £5 each.
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Jimbo,
Just looked further at the rfsolutions.co.uk website and there is a download available for the Zeta transceivers which gives you an Arduino library for the Zeta units plus sample Tx & Rx end sketches.
Thus I think I may well try a couple of the Zeta modules for general RF link experimentation as their range & data rates make them useful for a number of purposes.
Their "Small Outline" package size of 16x16mm with thro' hole connection pads is also handy.
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Having now looked at the ZETA units in more detail, I wouldn't advise going for these as they really also need a separate Codec chip to be able to control them from an Arduino type platform.
However, I am now looking at the RFM69CW units available from Hobbytronic which have similar RF characteristics and can be controlled directly from an Arduino.
A much more compact implementation though, is the tiny Moteino devices from LowPowerLab as these provides both the same RFM69 transceiver chip and an atMega328 (as in Arduino Uno) in a single tiny package about the same size as an Arduino Nano. (They are effectively another Arduino clone, using the Arduino IDE and libraries). There is also a RFM69 library and lots of home automation/networking sketch examples available for these units.

By the way, the U.K. Radio regulations allow the use of 433/434MHz for airborne model telemetry up to power levels of 10mW (+10dBm) but check the latest Regs. for detailed restrictions.
Note that a 1/4 wave aerial length for 433MHz is 173mm, so this needs to be kept straight in the fuselage.
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