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Build your own telemetry sensors.

May 2019 article - OpenXSensor

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Chris Bott - Moderator17/04/2019 21:27:42
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Here are some close-ups of the XT60 unit. Black is the Gnd wire. Yellow is the voltage representing current and Red is the lipo voltage measurement from the potential divider that I added for that purpose.

img_20190417_211633__01.jpg

img_20190417_211643__01.jpg

img_20190417_211722__01.jpg

Peter Jenkins18/04/2019 23:37:13
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Posted by Chris Bott - Moderator on 17/04/2019 19:58:30:

Jeti owners won't feel left out as the OpenXSensors are easily configurable for Jeti, Multiplex and Graupner HOTT, as well as FrSky.

But that's an interesting link Martin. Thanks.

Edited By Chris Bott - Moderator on 17/04/2019 20:02:07

Hi Chris

Do you know if this will interface with a JR XG system? I have a brilliant little sensor pack made by SM Modelbau called UniSense E. They cost Euro 70 so I've only got one! It would be nice to build a few more but only if they work with JR radio kit.

Thanks

Peter

Chris Bott - Moderator19/04/2019 10:01:03
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Posted by Peter Jenkins on 18/04/2019 23:37:13:
Posted by Chris Bott - Moderator on 17/04/2019 1

Hi Chris

Do you know if this will interface with a JR XG system? I have a brilliant little sensor pack made by SM Modelbau called UniSense E. They cost Euro 70 so I've only got one! It would be nice to build a few more but only if they work with JR radio kit.

Thanks

Peter

I'm afraid not Peter, no. Sorry.

Alan Jarvis19/04/2019 10:39:22
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Chris

I am ordering parts prior to the boards coming. Can you give me the pin spacing for C1, C2.

Chris Bott - Moderator19/04/2019 12:01:59
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Alan they are 5mm pitch spacing.

Chris Bott - Moderator20/04/2019 11:50:45
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Just for those who haven't spotted it, I've sent out PMs to everyone who's expressed an interest in the PCBs.

If you'd like PCB(s) and don't have a PM, please shout up.

(PM = personal message. See inbox on top bar of this page)

Andy Halmshaw22/04/2019 17:52:51
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I have now put heat shrink over the unit and as advised cut the sleeving away so that the two holes are not blocked. As you can see I have added a piece of "Open Cell Foam Rubber" because on the ground it was fluctuating up and down. Did seem to help but it did still fluctuate.

Can anybody with experience say if this is normal or am I expecting too much and do you have to mount the unit horizontal or is vertical ok?

When the wind subsides and I can go flying I will see how it works in a model.

img_2129_01.jpg

Martin Harris22/04/2019 18:35:44
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One thing from my own experience to look out for with altimeters/variometers in electric powered models with lace-like firewalls is that there can be significant pressurisation of the fuselage. Looking at flights where the model had apparently descended significantly underground on the take off run - even after removing a large piece of covering toward the rear of the underside of its fuselage prompted me to make a sealed chamber plumbed to static vents for my Extreme Flight Extra.  Sensors in fuselages behind proper firewalls need no further precautions.

Is that an altimeter? I've never had problems with fluctuations on my own Arduino/BMP180 or BMP280 based sensors built from the link I provided earlier and simply ensured there was an air path to the vent hole. I followed Jeti practice and provided a small piece of U shaped card on top of the IC then covered it with heatshrink.

Edited By Martin Harris on 22/04/2019 18:37:20

Chris Bott - Moderator22/04/2019 18:39:07
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Hi Andy

I put heatshrink over the whole unit and rely on slightly open ends.

I think if the heatshrink pulled tight over the face of the pressure sensor you'd have trouble, but otherwise it works well for me.

Over on this page it mentions making sure no direct light can get to the pressure sensor. There's other tips there too.

Mine are fairly stable, unless they get caught in any propwash during testing.

The only issue I find is that they need to settle after first being powered. So I turn on a model, do all my prefilghts and faffing about, then just before takeoff I reset the telemetry. This zeros the height reading.

Edited By Chris Bott - Moderator on 22/04/2019 18:40:04

Kevin Fairgrieve22/04/2019 19:09:26
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All Arduino boards are not the same!!!!!

I bought a few a little while back and made the servo tester. Good results works well.

Today I spent a good 20 minutes trying to upload openXsensor to a board.

Yep you guessed it. The second set of boards I got were 328P and not 168`s, both were 3.3v though.

Now I have a couple of MPU-6050 3 axis gyro with accelerometer sensor`s which I got in for this project.

Would they wire up in a similar fashion to the pressure sensor?

Told you I was a follower...

Chris Bott - Moderator22/04/2019 19:36:13
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Also beware, there are a couple of slightly different board layouts of the Arduino pro mini. One will fit the sensor PCB and the other doesn't.

The difference is best spotted at the row of holes at the end opposite to the programming end. On one type the row of holes is centred, on the other they are offset to one side. We need the latter.

Chris Bott - Moderator22/04/2019 19:53:38
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Kevin I've not dabbled with GPS but the connections are not like the pressure sensor no.

Have a good read of section 9 of config.description.h there are a few caveats about having to be careful about what voltages are connected to GPS modules.

Kevin Fairgrieve22/04/2019 20:21:27
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Thanks Chris I now have the correct board and will take a look at the sensor I have.

It is a 3 axis Gyro and not a GPS.

Kev

Kevin Fairgrieve22/04/2019 20:31:02
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The board at the top is the one I used for the Servo Tester.

Below are the 3 axis gyro and the board required for the sensor`s.

img_20190422_202244.jpg

Kev

Chris Bott - Moderator23/04/2019 09:51:35
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Hi Kevin sorry that will teach me to read posts properly.

I'm sure you've already found section 10 of the config description file. It describes how to connect and also has a calibration procedure.

You'll see that the accelerometer has to work in conjunction with a pressure sensor.

Chris Bott - Moderator23/04/2019 13:57:32
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I just thought I should expand on the warning about there being different layouts of Arduino Pro Mini boards.

It has come to light that there are a number of layouts.

If you wish to use one of the project PCBs then you'll have to use the right one. So here's a couple of photos of common ones.

This is the version that fit's onto the PCBs. These appear to be distinctive by the rectangular reset button.
The important thing though is that GND, A6 and A7 are along one end. We use A6 for overall LiPo volts and A7 for one of the cells measurements.

arduinodoesfit.jpg

The next one is a board that works electrically but has no connections across one end. So obviously these cannot be linked directly down to the PCB. I guess that flying leads could be used if the other holes all align properly?

arduinonofit.jpg

Edit - I just noticed also, that the programming points appear to be in the opposite order.

Edited By Chris Bott - Moderator on 23/04/2019 13:59:03

Mike Blandford23/04/2019 15:58:55
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Just for information, the lower of those two boards matches the "official" Arduino Pro Mini, as seen on the Arduino site. I also note on the rduino site it indicates the Pro Mini has been "Retired"!

Mike

Chris Bott - Moderator23/04/2019 16:06:48
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Thanks Mike. Useful info, as always.

Chris Bott - Moderator23/04/2019 17:21:39
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It looks like I can modify the PCB design to accommodate both layouts. I've done a quick redesign but have to go and give blood soon. I think I'll have a check of the design later and order a sample of 10.

I'll still send out the original design as soon as they turn up. If anyone has a particular objection, let me know. But the later version is untested and will be another 2 or so weeks once I do order them.

Chris Bott - Moderator24/04/2019 21:39:28
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Boards update.

I ordered 50. I had 3 of my previous order still in stock.

53 have now been asked for. I have addresses for all but one person and all but three have already paid. So many thanks for that, I feel bad that I don't have the goods yet. Any day now, hopefully.

I'll send them all out the day they turn up. I have the packaging and have address labels all printed ready.

Also, I've now tweaked the design to accommodate both versions of Arduino that we've spotted, and I've ordered 10 of those (and a couple of arduinos) so I can test one. There's nothing wrong with the original design, but if anyone would prefer to wait for the later board, please let me know. Those will be another 2 weeks, though.

Chris.

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