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Author Topic: Telemetry  (Read 5201 times)

g6swj

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Telemetry
« on: May 24, 2016, 09:17:03 AM »

Telemetry is an automated communications process by which measurements and other data are collected at remote or inaccessible points and are subsequently transmitted to receiving equipment for monitoring

I have started this thread and will re-post here some of the recent telemetry articles so they are all in one place

Now working on telemetry link using 2 x RFM69CW 433mhz transceivers about 8 each - manufacturer quotes line of sight range >1km - we will see!


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g6swj

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Re: Telemetry
« Reply #1 on: May 24, 2016, 09:18:25 AM »

Telemetry - one step closer to autonomous navigation
At last some success. If you have ever played around with technology/programming you will completely understand the experience of hitting a brick wall that just doesn't want to budge and your project grinds to a halt. Well after several precious hours of nothing I have at last got telemetry data flowing over the airwaves (433mhz) and now appearing on a remote shore based PC screen. It's rough (very) and needs thought but the basic concept is shown below - lucky it was only days before it hit the scrap heap...
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g6swj

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Re: Telemetry
« Reply #2 on: May 24, 2016, 12:49:04 PM »

Concept for animated dials displaying data on telemetry "dashboard"

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Brian60

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Re: Telemetry
« Reply #3 on: May 24, 2016, 05:13:37 PM »

Why two sensors and two arduino's? Is it comparing one set of results against the second set?

g6swj

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Re: Telemetry
« Reply #4 on: May 24, 2016, 05:47:32 PM »

Hi Brian,

The 2 little circuit boards are radio transceivers not sensors. What you are looking at is 2 separate circuits connected together via 433mhz radio transmission.

So when all is up and running there would be a remote (on boat) transceiver connected to an Arduino which in turn is connected to IMU/GPS etc therefore facilitating transmission back to shore of telemetry data GPS, sensor, battery etc etc. On shore the radio transceiver is connected to an Arduino allowing data to be received and displayed on an LED screen/ computer etc.

Of course these are "transceivers" so you could equally broadcast a message back from shore to remote and get the Arduino to perform something, ( trigger a relay, control an ESC....)

So it could equally be the guts of a sophisticated 2 way radio control system ( 1 channel unlimited commands) - would just need to be hooked up to control surfaces/sticks/switches etc

Regards
Jonathan
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Brian60

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Re: Telemetry
« Reply #5 on: May 25, 2016, 09:27:54 AM »

Ah got it Jonathon. This is going to be one hell of a set up if/when you get the bugs ironed out of it. Look forward to reading more in coming weeks.

g6swj

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Re: Telemetry
« Reply #6 on: May 31, 2016, 08:27:37 PM »

Telemetry concept works and I now have wirelessly linked PC to remote sensor pack which would be on-board a boat capturing  GPS & 10dof IMU sensors (Gryo, Accelerometer, compass etc), battery voltage, speed, temperature, ultrasonic radar results and pretty anything else you can capture and turn into an electronic data signal that can be relayed back to shore.

Whilst the interface is still not pretty and lots of configuration/ error checking to make it more resilient are required this is the latest with animated compass and pitch and roll gauges which respond to live telemetry data.

Latency time is very low so gauges move in almost real time.

Regards
Jonathan
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Vts99

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Re: Telemetry
« Reply #7 on: June 02, 2016, 07:31:24 PM »

Never thought of even looking at anything like this as I've just returned to hobby after about 15 yrs so still struggling with the new electronic systems etc but reading this i was just wondering if it could be applied to stabilisers so that they work independently rather than manually or off the rudders so would give larger vessels a more stable presence
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g6swj

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Re: Telemetry
« Reply #8 on: June 02, 2016, 11:32:37 PM »

Hello Vts99,

I am sure there is something here to increase stability for boats that could do with it - reading a sensor and making an adjustment of some sort - I have a few candidates that could benefit from this concept -  I have modest size boat - one that is a little top heavy and each outing it has a few near misses with it wanting to become a submarine. I have considered experimenting with a movable weight to counter roll - a long length of wood pivoted at the opposite end to the weight, weight on a track that could be quickly moved to port or starboard both would allow swift dynamic adjustments of COG. Clearly if it did not adjust quickly enough it could actually make things worse. Maybe more tradition stabilisers with dynamic control would be more effective?

Several other things on my experimentation play list before I get to this one but it could be interesting.

Regards
Jonathan
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Vts99

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Re: Telemetry
« Reply #9 on: June 03, 2016, 11:26:23 AM »

I might look into this . Thinking maybe a trim on either side so if one up and one down showing a roll then stabiliser kicks in to counter the roll maybe

Graeme
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Martin [Admin]

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Re: Telemetry
« Reply #10 on: June 06, 2016, 08:42:44 PM »

Split and renamed!  :embarrassed:
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"This is my firm opinion, but what do I know?!"    -   Mayhem FaceBook Group!

g6swj

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Re: Telemetry
« Reply #11 on: June 07, 2016, 08:54:30 AM »

The project progresses slowly.

Video shows current latency which when overall programs are streamlined should be even more responsive. (sorry for poor video quality)

YouTube video https://www.youtube.com/watch?v=ZveydhZimJw

Regards
Jonathan
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Brian60

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Re: Telemetry
« Reply #12 on: June 07, 2016, 11:49:07 AM »

 :-)) :-))

One thing I have read Jonathon, is how sensitive the IMU's are to magnetic fields. In one demo I watched, just moving the unit closer to a metal table affected the heading of the magnetic compass.

Taking that into account, how are you looking at shielding it not only from anything ferrous in the ship, but from all the magnets which obviously have a much greater magnetic field, in the drive motors? In my case I will have around 14 motors in the new build of varying sizes.
 

g6swj

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Re: Telemetry
« Reply #13 on: June 07, 2016, 12:25:21 PM »

Hi Brian,

I hope that a process of calibration/offset configuration might get around this ("external forces") - very much part of the experiment - not sure right now what the issue/outcome will be - no doubt a few more grey hairs I am sure..

Regards
Jonathan
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Brian60

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Re: Telemetry
« Reply #14 on: June 07, 2016, 03:12:09 PM »

Well hopefully by the time I get to this point you will have solved it {-)

However how about this for an idea I was saving.

In shops like Halfords you can by expanded aluminium mesh - in the bodyshop section with the body filler. Make up a Faraday cage to either surround the drive motors or the electronics, or even both. Now I'm not sure if aluminium mesh would work or not, but you can get the same type of thing is steel, but I thought aluminium for lightness.

Hmm, maybe not for the electronics, a Faraday cage would block out the signals as well as stopping the ingress of unwanted magnetic pulses.

g6swj

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Re: Telemetry
« Reply #15 on: June 07, 2016, 03:22:42 PM »

Faraday Cage - Wow - that's a whole project in itself!

Interesting link ( one of thousands - I just love the access to knowledge that the internet brings - problem is you can really get into stuff that eats away at your valuable time)

https://backyardbrains.com/experiments/faraday

Now one of those moments that I open my mouth without thinking (no doubt regret this) I think Faraday cages block electromagnetic (radio/RFI etc) signals and not magnetism itself.

Answers on a post card!

Jonathan

Just googled - thought it was like this
Quote
No. The point of a Faraday cage is that it's made of a conductor, which responds to electric fields. A strong magnetostatic field is different, and will barely be affected by the Faraday cage.
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Brian60

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Re: Telemetry
« Reply #16 on: June 12, 2016, 02:38:16 PM »

Jonathon I'd like to get a second opinion here.

The 9DOF IMU board from Adafruit (the one you are using) I thought about sourcing this in the UK, however most wanted 3 times the US price and the official importer want over 50 :o So I'll be ordering direct. But I came across on one english site that it is no longer available as out of production.

Going to the Adafruit site it is still available so I reckon they are telling porkies. Now this is where I'd like advice. On the Adafruit site there is also this 9DOF IMU,....  https://www.adafruit.com/products/2472

OK its twice the price but as it says most of the math is done onboard rather than having to collect algorithms and code it. It seems a much simpler way to go if half the work is already done.

What do you think? Is it worth the extra cash or go with the original?

grendel

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Re: Telemetry
« Reply #17 on: June 12, 2016, 05:16:39 PM »

if you had an array of 3 or 5 transponders around the pond, you could probably get a position fix to cm accuracy, this would assist automated displays and the slaving of several boats to each other
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flashtwo

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Re: Telemetry
« Reply #18 on: July 01, 2016, 04:47:05 PM »

Hi,

Thinking back to the old Cathode ray oscilloscope days, I remembered that mu-metal was used to shield the 'scope from the transformer, viz:

https://en.wikipedia.org/wiki/Mu-metal

Also, as you know from other forum threads, I'm using a compass/gyroscope board as part of the Voice Controlled Edwardian Steam Launch navigation system. I've positioned the compass up in the roof of the launch, as far as I can get from the steam engine and electric motors. I've used it successfully for compass control of the rudder, though I haven't carried out any "scientific" calibration of the system.

Perhaps you could carry out a similar exercise they did in the War, when calibrating the HUF-DUF radio direction finders, and actually make a "calibration compass map" by turning the boat through 360 and prompting the computer with the exact direction and build a look-up table ;- depends if you want the ultimate accuracy.

I like your YouTube video of the system in operation, very advanced I must say. Will you be displaying data in graph (parameter v. time) form; I would find that very useful for monitoring my boiler controls, i.e. pressures and temperatures.


Ian.
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g6swj

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Re: Telemetry
« Reply #19 on: July 02, 2016, 12:04:03 PM »

Hello Ian,

Interesting points re calibration & look up table - I can't recall where but I have seen something vaguely similar in concept. Yes it would be possible to graph any of the parameters in real time, currently they (sensor data) are saved to a csv text file on the shore based computer as well as written to a micro SD card on the remote (boat) - ready to be analysed afterwards, offline should there be a need. The application in the video is written in Visual Basic using a free copy of Microsoft Visual Studio - it's a simple application with very few lines of code and is really little more than parsing lines of data and updating the screen. Childs play compared to Pic programming:)

My intention of creating my own telemetry system was simply to have a vehicle that would allow me to get a picture of what is happening with other experiments - dynamic stability, autonomous navigation etc.

At the end of the day, all a bit of fun that keeps the grey matter on it's toe's

Regards
Jonathan
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