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Arduino thrust meter setup

#1
Hi all

The here are some brief details as it is at the moment as i am making it up as i go along. and will post more details as I get it closer to being finished.
The software is written at the moment to do some preliminary testing.
This is something i am currently working on to help me sort out my motor collection and help understand a bit about motors.
The frame is made from laser cut 3mm perspex glued together.
It slides on 6mm linear bearings.
the load cell is something i got from Ebay that uses the HX711.
At the moment it has an external watt meter conected to it but will be self contained.
The motor will be controlled via the Arduino using an appropriate external ESC and run of a Lipo battery of the correct size for the tests.
So stay tuned for it's progress and will post some videos of the device in action

P9150033.JPG P9150034.JPG P9150035.JPG P9150036.JPG
 

DamoRC

Elite member
Mentor
#2
Cool - looking forward to seeing it in action. Will you be using a shunt or hall effect for current measurement?

EDIT - And RPM sensing?

DamoRC
 
#3
I have put a crappy video up on YouTube, videos are not my thing but will give you an idea of what I am doing
Cool - looking forward to seeing it in action. Will you be using a shunt or hall effect for current measurement?

EDIT - And RPM sensing?

DamoRC
For current sensing will probably use a hall effect type sensor or some other non-obtrusive method, and yes will have RPM sensing as well.
here is a few adapter plates I have done, each one has a front plate that bolts to the motor then a back plate that spaces out over the heads of the bolts. All of the motors mount so the centre of the motor or thrust line is on the centre line of the load cell.
P9150004.JPG
At the moment trying to work out what connectors for batteries and ESC's to use. As at the moment I have JST and Deans but will convert everything to Deans as I never have enough adapters to go around. May use Banana plugs as that is what most balance chargers have so most people will have that for there batteries.

The files will be made available for everyone to make there own, including the information on the electronics
 

DamoRC

Elite member
Mentor
#4
I have put a crappy video up on YouTube, videos are not my thing but will give you an idea of what I am doing


For current sensing will probably use a hall effect type sensor or some other non-obtrusive method, and yes will have RPM sensing as well.
here is a few adapter plates I have done, each one has a front plate that bolts to the motor then a back plate that spaces out over the heads of the bolts. All of the motors mount so the centre of the motor or thrust line is on the centre line of the load cell.
View attachment 114850
At the moment trying to work out what connectors for batteries and ESC's to use. As at the moment I have JST and Deans but will convert everything to Deans as I never have enough adapters to go around. May use Banana plugs as that is what most balance chargers have so most people will have that for there batteries.

The files will be made available for everyone to make there own, including the information on the electronics
Cool!

Inspired by your build, I have dragged out the bits and pieces that I had put together previously for such a test stand. I had forgotten how satisfying it is to tinker with this stuff (although I should note that since I have started tinkering, I have stopped designing and building planes!).

DamoRC
 

ElectriSean

Eternal Student
Mentor
#5
Cool!

Inspired by your build, I have dragged out the bits and pieces that I had put together previously for such a test stand. I had forgotten how satisfying it is to tinker with this stuff (although I should note that since I have started tinkering, I have stopped designing and building planes!).

DamoRC
I am so bad for that... Obsession has it's plus's and minuses ;)
 
#6
Cool!

Inspired by your build, I have dragged out the bits and pieces that I had put together previously for such a test stand. I had forgotten how satisfying it is to tinker with this stuff (although I should note that since I have started tinkering, I have stopped designing and building planes!).

DamoRC
It is a problem that, at the moment I am the other way trying to build something I can actually fly. So have not been playing with the thrust meter. 2B or not 2B that is the question.
 
#7
Finally got to do a bit more on the thrust meter. Got a strange problem with the Arduino Uno when I connect the the Analog input up to the battery or even ground it locks the Arduino up, Something to do with the load sensor I think as without that and just doing analog reads works fine:unsure:. So just changed over to A Mega 2650 and no problems at all. As can be seen by the photo added the second screen for the voltage and watts display, may add the number of cells to the display, max 6s 25.2volts?. May compact it down latter but for now easy to see what is going on. but also will need to put the RPM display somewhere. Just need to find the current sensor now.
 

Attachments

rockyboy

Skill Collector
Mentor
#8
Love this project! :D

Really looking forward to following your footsteps on this over the winter. I've been "thrust stand curious" for a while, but haven't relished the idea of tackling the software (just not a hobby I get exited about these days).
 

DamoRC

Elite member
Mentor
#9
Finally got to do a bit more on the thrust meter. Got a strange problem with the Arduino Uno when I connect the the Analog input up to the battery or even ground it locks the Arduino up, Something to do with the load sensor I think as without that and just doing analog reads works fine:unsure:. So just changed over to A Mega 2650 and no problems at all. As can be seen by the photo added the second screen for the voltage and watts display, may add the number of cells to the display, max 6s 25.2volts?. May compact it down latter but for now easy to see what is going on. but also will need to put the RPM display somewhere. Just need to find the current sensor now.
Given what you've achieved thus far you are clearly experienced with the hardware and this might be a dumb question, but you are aware that you can't connect more than 5V to any of the input pins?

I'm using the Mega 2650 for mine also although I will probably confirm that it also works on the Uno. Instead of building an LCD display, I just have it rigged to a laptop and use old software I wrote for a different but similar application to visualize the data.
So far I have the cells voltage done (each cell independently measured, up to 4S) and the RPM from the ESC wire. This was a real pain. I have a couple of optical sensors I built to track the RPM based on the prop blade passing and these work fine, but I really wanted to try to figure out how to get RPM from the ESC directly because at some point the whole shebang could be tidied up and actually mounted in a plane like a DIY data logger.
Next up is the current meter. I have tried a DIY approach to this before using a Hall Sensor embedded in an RF choke that was clamped to the battery wire. It worked but the signal amplification piece was always dodgy and its hard to calibrate something scratch built to 100 Amps. So I sprung for one of these hall sensor based units from DigiKey.
Also picked up a load cell and a HX711, but being the masochist that I am, I think I am going to play with making my own amplifier for the load cell, just for fun.

The software interface to the laptop only requires a few lines of code to the Sketch, so if you are interested, I'll happily share if you want to try it out. Its not quite ready yet as I transition it from the old functionality to something usable for this application.

Not a single plane built or repaired in the last two weeks since I started this, but its fun!

DamoRC
 
#10
Given what you've achieved thus far you are clearly experienced with the hardware and this might be a dumb question, but you are aware that you can't connect more than 5V to any of the input pins?
DamoRC
It is a valid question when you know nothing about the person, used a voltage divider with a pot in 1 leg. But to set your mind at rest I Have a Certificate of Technology Microprocessor Design and an Associate Diploma in Electronics plus many other things I won't go into here as for the speed the problem is with using the ESC if you are checking a Brushed Motor the output would not be valid. I try use bits of the shelf now days as it cuts into the play time to much doing things from scratch. But saying that I have a n OO train set that that is controlled by 5 Arduinio's hooked up on a Can-Bus, and built all the throttles and track sensors from scratch. Can't play trains at the moment as there are planes all over the layout.:). and the planes seem to take up a lot of room as they are sooo big.
 
#12
But one thing you have to remember some people are theoretically perfect but practically useless;).
The only reason I got those pieces of paper was that my hobbies were electronics and building computers so thought it might be a good idea to actually understand what I was doing " didn't help I still have no idea what I am doing sometimes.:confused: