Voltage and Current monitoring for a South Carolina Arducopter


Using EC3 connections on my quad was a good idea...except when it applied to the AttoPilot 90A sensor from SparkFun. The goal for adding this sensor to the system was to be able to remove it cleanly if needed. The sensor pcb design was changed (from earlier pics in the Wiki) to provide a clean installation of Dean's connectors. What to do? Adapt and Overcome! Behold my solution!

And from the back of the audience I hear "Yeah? So what?" Well the 'what' is the constant challenge we as hobbyists face to take parts and components from different maunfacturers and adapt them to our uses. Have you read the thread on adding this small part? To save you the trouble of looking for it, HERE. Imagine the confusion on the part of the hobbyist who asked if the sensor should be getting hot enough to melt the solder! Wow. The first task I performed after getting a successful adaptation to EC3 was checking for a direct short of the battery connection - none was found. (whew!!) The second task was to insulate the power connections to ensure a short was not added accidently while in use (or crashed).


The solution? Hot Glue! The low temp variety of hot glue guns is cheap and cheap to use. Both sides were sealed off and then tested for mechanical strength. Next was to integrate it into the quad and set it up via Mission Planner. The above linked instructions worked flawlessly to set up the sensor. There is some confusion if you should subtract the 0.3V from the actual measured output from the PDB to the APM. I subtracted it anyway - the MP prompts said I should even if it is contradicted in the Wiki instructions.

The actual function of the sensor can be seen after the APM is reset. It can also be tested with the CLI under the 'tests   -> battery ' command string. NOTE: The CLI prompts you with a "Careful" mesage. THIS MEANS THE MOTORS WILL BEGIN RUNNING! ALL THE MOTORS! I did have my propellors removed prior to making the mod but if you, dear reader, decide to add this and perform the CLI tests.. REMOVE YOUR PROPS.

What you see above is the output of the CLI while the battery test is running. Note that 'Careful' actually blends into the 'Hit Enter to exit' string. When I hit Enter, the screen stopped updating but THE MOTORS CONTINUED TO RUN! I tried various commands from 'exit' to 'Cntr-C' to 'stop battery' all to no avail. The motors stopped spinning when I clicked on the 'Flight Data' icon at the top of the screen. I suspect the command string that is sent to the APM to shift from CLI to Flight Data mode flushed the command registers of the battery test states.

The last part of this tale will be a photo of the AttoPilot sensor as installed on the quad. It is installed prior to the PDB on my system but after the arming plug harness (covered in a previous blog post HERE). Thank you for reading this far and I wish you success should you choose to add this neat device to your system.

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Comment by Carl La France on September 30, 2012 at 4:14pm

R.D. When  hot glue gets re heated it melts The guys in the wood shop  tried gluing an  electric drill back together that  had  fallen and got broken once it heated up it came apart again. They use hot glue to temporarily hold pieces together until epoxies has time to cure   maby fire retardant  silicone? I like the velcro holding the arming plug in place until it is needed Have a good day!

Comment by R. D. Starwalt on September 30, 2012 at 4:45pm

Hey there Carl! Perhaps I should clarify about the hot glue? An AttoPilot sensor does not get hot when it operates. The link above referring to melting solder was certainly due to a mistake on the part of the person asking if it should get hot. He certainly had a short on across the battery in/out on the circuit board. That is why I checked my work with a DVM to make sure I didn't build in a problem.

In my application of the hot glue, I am just trying to keep the contacts insulated/isolated from touching anything conductive. RTV would work fine as long as the curing process didn't attack the board parts and traces. Heck, Elmer's white glue would also work but it would take a long time to dry and more than one coat would be needed.

The velcro arming plug parking spot didn't occur to me until I had the extra pieces from some parts I bought at the hobby shop. They were so small I didn't have a use until the light went on. So far, so good. If for some reason I lose the arming plug, no worry, I made the harness so that I could just connect the battery like it was, only now I have the AttoPilot sensor in the circuit also.

Be good to yourself!


Comment by Alex Hills on September 30, 2012 at 5:06pm

I used EC3 connectors on mine as well.  Instead of hot glue, I just used a big piece of clear heatshrink from the store: https://store.diydrones.com/HeatShrink_tube_p/pr-0004-01.htm

Comment by R. D. Starwalt on September 30, 2012 at 5:26pm

Hello Alex. I initially attempted to have the EC3 connectors in the same plane as the pcb. This would have required longer leads from the EC3 to the pcb and would have worked well with large heatshrink tubing idea.

As with many things, there is usually more than one solution. Thank you for the comment and if you get a chance, add a picture so others could see another way to do it.


Wiki Ninja
Comment by Stephen Roach on September 30, 2012 at 5:40pm

Great write up! thanks

Comment by Dany Thivierge on September 30, 2012 at 6:47pm

BTW the motors in CLI motor test will stop when they finish their cycle (each motors will spin a bit in sequence) 

When you hit ENTER it will complete the sequence, let it finish (going back to motor 1) 

Comment by R. D. Starwalt on October 1, 2012 at 4:15am

Dany, Are you are referring to the CLI motor test --> 'setup motors'. That is a great tool for confirming motor connection/dircection.

In my case I was using 'test battery' - something I had not used before. It was a big surprise for all the motors to start up simultaneously. Some form of battery information and not motor function was expected. It makes sense to load the system and monitor/display results.


Comment by Crashpilot1000 on October 1, 2012 at 6:21am

Looks heavy

Comment by Kim Skatun on October 1, 2012 at 6:57am

Hi, I really like your red on/off switch on the right hand side of the the picture.

Can you take some more photos off it? How did u make it?


Comment by R. D. Starwalt on October 1, 2012 at 7:01am

Crash - It is heavy... duty. ;)

For the benefit of those who may be numerically obsessed.. it weighs just under 11 grams.

The quad, RTF with empty camera mount, is 3.4 lbs, 1.5 kg. Flight/hover time has been at 9 min with a 3S 3200 mAh Eflite 30C battery. See THIS post regarding flight time and modeling information.

As I have stated before, I do not complain about her weight, she does not complain about my flying. :)


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