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Build your own telemetry sensors.

May 2019 article - OpenXSensor

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Mike Blandford21/05/2019 19:56:22
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David: A bit of confusion, the A3 and A4 here are the FrSky telemetry values being sent, not the A3 and A4 analog inputs to the Arduino.

Chris has solved the problem by setting a scaling value of 0.1 in the configuration file (discussed on another forum).

Mike

Chris Bott - Moderator21/05/2019 22:18:56
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It is confusing isn't it? That's probably the hardest thing in OpenXSensor.

Once you've worked out that V1 to 6 can use any of the analog arduino pins A0 to A8, and you have to exclude the ones that are for current measuring and for SDA/SCL when using the likes of pressure sensor, GPS etc, then you start to get to grips with it.

Then FrSky label their analog voltage parameters A1 to A4, their LiPo pack volts VFAS etc. etc...

Andy Halmshaw23/05/2019 09:53:09
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Hi Mike,

Thank you for your post, entering the figure you had suggested helped but after experimenting I found that a figure of 1595 gave a more accurate reading. I used another meter in series and compared the readings and adjusted the number until I got the best match.

Andy

David Tayler26/05/2019 09:36:50
92 forum posts

Chris and Mike, Thank you for your help. Sorry to be confused by the Frsky/arduino nomenclature. I now have a module almost working for lipo voltage. I have the following display on my Taranis X9D;-

1: A2 11.1V( presumably from the receiver)

2: Cels 11.49V

3: RSSI 84dB

4: RxBT 5.0v

5:Vfas 11.50V

I only have 3S lipos and have not yet built the current sid eof the modue.The arduino pin connections are as per Chris's diagram/ PCB. VFas_SOURCE VOLT_3 to use the balance lead. Why do I not have individual cells displayed ? Also I have a series of flashing stars on the transmitter display.Why?

Thanks for the project I am gradually getting my head round it. One last question is there a cheap airspeed sensor available?

David

Paul Lewis 326/05/2019 09:57:02
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Hi,

You will only see cells in the telemetry discovery screen try searching for FLVSS individual cell voltages for information about how to display each cell or click the link below

https://openrcforums.com/forum/viewtopic.php?t=7266

The stars appear as it reads the value of each item and is normal.

P.S. if you have a Horus using OpenTX there is a nice widget you can use on the Telemetry screens called BattCheck that will display the voltage and pack % graphically.

Edited By Paul Lewis 3 on 26/05/2019 09:58:45

Edited By Paul Lewis 3 on 26/05/2019 10:07:16

Chris Bott - Moderator26/05/2019 10:10:16
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You have the Cells voltage showing the total of all cells.

To see individual ones you need to add calculated sensors.

So

Add a new sensor

Type: Calculated

Formula: Cell

 

Then chose which cell or just lowest, highest or delta.

 

Note: Cells will only show up when a battery balance connector is connected.

Edited By Chris Bott - Moderator on 26/05/2019 11:31:09

Andy Halmshaw26/05/2019 11:45:51
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I may be able to help here.

If you go to the Telemetry screen on your Taranis transmitter and copy "Cels" (in this case) three times, then edit the first line as per the second photo. Then edit the second line as per the third photo, you will have the individual cell votages, and obviously the third line the same but inserting 3 . This will work for any number of cells in a pack (only four with Chris's telemetry module), just keep copying for the number of cells line.

You next need to edit the display page on your Taranis. Then when you long press page on your Taranis transmitter you can display your telemetry data as per the fourth photo, as you can see this is an old pack where the cells are slightly out of balance even though I use a balance charge every time.

Hope this is of help.

Andy

Photo 1

img_2275_01.jpg

Photo 2

img_2273_01.jpg

Photo 3

img_2274_01.jpg

img_2279_01.jpg

Andy Halmshaw26/05/2019 11:54:17
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Hi David

I think that the flashing stars as you call them is when the telemetry data going to the Taranis changes. If the data is very stable no flash, when the value changes they flash.

Andy

Chris Bott - Moderator26/05/2019 13:33:17
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Posted by David Tayler on 26/05/2019 09:36:50:

Thanks for the project I am gradually getting my head round it. One last question is there a cheap airspeed sensor available?

David

I'm not sure about cheap but I think this is the sort of thing you're looking for.

David Tayler26/05/2019 17:47:24
92 forum posts

Thank you all for the help ,especially Andy in this instance. I can now see all the cells and the total. My current sensor arrived yesterday so I will add it. I think for the air speed sensor it may be as cheap to buy the Frsky modulle,even if that seems like cheating!

Chris Bott - Moderator05/06/2019 11:23:33
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Quick update. We're now up to 78 PCBs that have been requested. That number has astonished me, so many thanks for all the interest.

Hopefully the reduction in questions here means that those that have built some sensors are doing OK?

I think that demand for the boards is possibly over but a new batch has turned up today. These incorporate all the changes that have been suggested (along with a correction to the resistor numbering on the last batch - compare the pic below with the previous one - doh!)

These have come to me in 4s just to save me taping them together for postage. They snap apart easily so I can still send any required number.

I'll build one up over the next day or two just to make sure everything is OK.

Chris

img_20190605_105652.jpg

Chris Bott - Moderator06/06/2019 14:40:26
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Latest version board now built and fully tested. All good.

So boards 77&78 are in the post. All requests fulfilled.

img_20190606_103212.jpg

Kevin Fairgrieve06/06/2019 18:15:52
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I am still waiting on a few components coming from China!!

On holiday to Malta next week, if upon my return they are not here....Paypal dispute..angry

Kev

Paul Lewis 314/06/2019 09:56:10
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Here is my latest sensor with a MPXV7002 airspeed sensor using A0 and A1 with a voltage divider on the ADS1115. The ADS1115 connects to the same pins (A4, A5, VCC and GND) as the GY-63. I also have a Hobbywing RPM sensor which measures the pulses from any two of the output wires from the brushless ESC. The RPM sensor connects to PIN8 on the Arduino and takes it’s VCC and GND from the second SPORT connector. I am also using PPM via the SPORT protocol to reset the Airspeed and to change between different vertical speeds calculations using compensation from the Air Speed sensor controlled via LUA scripts.

Next I think I will try and create a 6S version with additional 100nf capacitors to ground try and stabilise the cell voltages. I will also use the ADS1115 to do the Current Sensing using an external HGLRC XT60 connector. But I need to get to grips more with Eagle PCB design software first.

Chris did you use Eagle to design your PCBs?

wp_20190614_00_32_51_pro.jpg

Chris Bott - Moderator14/06/2019 20:20:41
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Wow Paul you've really picked the ball up and run with it there.

Nice job. H

have you gone about calibrating RPM? I.e what sort of numbers have you put where? (OpenXSensor and the Tx).

How do you fancy picking up temperature sensing? That's something I'd be keen to follow.

I'll PM about PCB design as that's a whole new subject.

Cheers

Chris.

Paul Lewis 315/06/2019 00:42:11
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Hi Chris, I haven’t calibrated the RPM sensor yet I have just connected it to a test rig and checked the numbers go up and down as the motor speeds up, I will be mounting the senor to a model very soon and then using my handheld optical RPM sensor to find the correct scaling factor as it depends on the number of poles in the motor.

In the config_basic I just have “#define CALCULATE_RPM YES” As you need this for it to send the telemetry from what I understand the rest is setup by using a calculated sensor in OpenTX but I will let you know.

I thought a about temperature but it seems to only support the analogue pins on the Arduino and not on the ADS1115 so I have no pins free however I guess that if I don’t have a Baro or ADS1115 I could use pins 4 and 5 or have two oXs sensors.

Michael Hadaway08/07/2019 10:40:55
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Hello Chris.

I have been following this series with interest since the article in the magazine.

Its still a bit of a mystery to me, but I would like to purchase a few of your project boards and have a go.

I understand that you can supply them for £2 + £1 p&p and paypal is accepted.

I would wish to bye three please.

Mike Hadaway

Chris Bott - Moderator08/07/2019 16:59:42
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Hi Mike

I'm away on holiday at the moment but yes that's all correct.

If you send me a PM, I'll get back to you with PayPal details etc and you can let me have your address. No rush though, I can't do anything until the start of next week, sorry.

Chris Bott - Moderator15/07/2019 21:12:26
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If anyone is expecting a reply about purchase of PCBs could you look at your PMs please.

The last two enquiries had replies sent by me about a week ago, neither has been read yet.

Cheers

Chris

Stephen Jones15/07/2019 21:57:47
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2695 forum posts
1528 photos

Hi ,

I have a Adafruit Pro Trinket.

Is it any use for something like this.

Steve

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