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View Poll Results: "Flying Watt Meter" - What most interests you, as electric aircraft sensing package?
Current+Voltage+Wattage pack 6 30.00%
Current+Voltage+Wattage+Temperature pack 8 40.00%
Current+Voltage+Wattage+Temperature+GPS pack 6 30.00%
None. Doesn't interest me. 0 0%
Voters: 20. You may not vote on this poll

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Sep 27, 2011, 07:21 PM
Radio? Screwdriver!
New Product

Hitec Aurora Telemetry - Open Source "Flying Watt Meter"

Hi All,

Firstly - thanks to the successes of the Aurora 9 advanced telemetry thread ( on this excellent forum, I have been designing my own electronic telemetry 'widget'. So my thanks goes out to everyone who has helped decipher the Hitec Telemetry interface.

The idea of this Sensor Station type unit is to have a one-board unit to allow both the current and voltage to reported back to the transmitter when in flight.

This project came about of two main reasons, the first is I needed (and wanted) to know what sort of current my electric setups are running in the air and secondly I've given up waiting for the Hitec Blue (Electric Version) Sensor Station to be sold! The other big problems with the Hitec solution, is its likely going to be too expensive to equip every electric aircraft with it, and also due to the fact you need multiple sensors attaching to it - large, heavy and bulky. Which isn't a problem for large expensive electric aircraft - however most of my electric aircraft are .8m to ~1.2m (~31" to ~47") and typically draw around 15-40A on a 2S/3S/4S pack - hence the need for a simple light weight solution.

So I've developed to the following specification:
  • Small and light as possible. The current design measures in at 2.5cm by 4cm (~1" by ~1-5/8") - which is small, but I want to get it smaller! It weights about 3-4g without leads attached.
  • Read up to ~50A. This should be enough for most foamies and other electric aircraft.
  • Read up to 6S packs. Again a 6S pack is large enough for most applications. Remember a 6S pack at 50A, will be drawing around 1.26kW.
  • Fairly accurate. I'd expect it to be, at the very least, within ~1-2A at the higher ends of the scale, if not more accurate.
  • Able to read at least 2 temperatures up to 125C. The magnets in brushless motors are only good up to 80C, go above that and you quickly destroy their magnetism and ruin their power output. For the speed controller, you don't really want that going over 80C either - most consumer electronics is only rated to 80C or 125C - depending on the spec of the components used.
  • GPS interface. Its essential to know how fast and high your plane is flying.
  • Open Source. So you can see exactly what's going on and your able to hack it to work with other stuff easily too.
  • Finally, but most importantly - Low cost! As a basic package (that reads just Voltage+Current+Amps - extras such as Temp+GPS can plug in separately) I'm designing this to have a price point of a decent Watt-Meter - cheap enough to be affordable to fit to every electric aircraft. As a number, its not final but I'd aiming for around 20-25 or $30 to $40 USD mark.

So far I'm currently at the stage of testing the hell out of first hand assembled, manufactured prototype units and trying my up most to break them and find bugs. Attached below is pictures of one of the prototype units so you can see what it looks like - pictures are a bit crummy as it was taken on my camera phone. Also, please excuse some of the wonky text on the board - was a small mistake when I sent the files off to be manufactured. It doesn't affect the performance and will most certainly be fixed for the final version!

I'll upload some more pics of it in action later.

Once I get a few minor bugs out of the way, I'll knock up a handful and sell them at near part cost as final Beta test units and allow others to find bugs. Hopefully there won't be after I've thoroughly tested it, but if I do release something to a mass-market, I want to make sure its fully bullet-proof! I'll also publish the full source code and schematic for others.

So what do people think? Would anyone else be interested in this?

I have no idea if this would be useful to others? Do the specs cover enough, or are there some must have features?

I would like this to become a useful product (if there is demand out there for it) - however I did this mostly as a bit of enjoyment (I design electronics + firmware for a living, but I don't get time to do fun projects for myself at work).

Let me know guys and give me feedback, good and bad!

Last edited by SimonChambers; Sep 27, 2011 at 07:33 PM. Reason: Added images
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Sep 27, 2011, 09:56 PM
Registered User
Nice work.

In my experience the top priority telemetry item for most e-flyers is mAh consumed. Sure, voltage, current and power are interesting but used mostly for setup and tuning which can be done with a portable device you move from plane to plane. However, mAh consumed is of interest on every flight in every plane.

So if you are going to all this trouble I would strongly recommend you consider adding support for mAh measurement. Typically this is obtained by integrating the current over time.

I am not sure if there is a dedicated slot in the A9 telemetry display for mAh but you could potentially hijack the Temp3 and/or Temp4 slots as a work-around. Another option might be to have a way to program the pack capacity into the module so that you could then use the fuel guage indicator. However I think most users would really like to see the actual mAh number.
Sep 28, 2011, 03:08 AM
Registered User
Thats Great Works..... same here, hope you add a mAH measurement.....if you have extra memory, maybe you can add a Datalogger feature, just like an EagleTree Data logger.

I guess, I would never look at my Transmitter LCD display when I fly my Helicopter. I usually ask my Buddy to Read the LCD display when I fly......a Data logger will be nice if you fly alone (No need to Bother other flyer), Just make sure you also read the Throttle Stick, so that when you downloaded the data, you can read the Throttle Stick Position, Voltage, Current, mAh, Temp1..........
Last edited by lazy-b; Sep 28, 2011 at 03:15 AM.
Sep 28, 2011, 10:07 AM
Glad to see other people are using the info that came from the Aurora 9 advanced telemetry thread.

Myself I got just what I wanted, and a bit more.

I have two full Sensor stations build that have Amps, Voltage, Temp, RPM , and GPS. The smallest is 1 inch by 3 inches and is based on Arduino Mini.

I when to all this trouble for what I call a gas gauge for electric flight.

I have total amps used displayed in the rpm 2 spot on the transmitter, and also have the fuel icon starting full and dropping as my mAmps used goes up.

I also have the Bluetooth board that Swin sold.
This sends the info to my droid phone and Matts software that speaks the fields that you tell it.
I normally have Esc temp,( I live in AZ and here in the summer I need to know it's temp) and mAmp.
This gives me everything Hitec promised, but has failed to deliver to now.

The only weak part of the system, is that where I put mAmps used, RPM2 area, you must round off by ten. so 1999 on the display is 1990 or 2000
Sep 28, 2011, 12:29 PM
Registered User
Volts, Amps, mA consumed, Temp, RPM. But all of this doesn't can't be used while flying unless there are separate discernable alarms for each. It would also be very beneficial to log for review post flight since you can't watch values and fly at the same time.
Sep 28, 2011, 03:29 PM
Radio? Screwdriver!
Cheers for the feedback guys.

mAH used is something that I have considered. Like you said, it'll have to be displayed on another parameter - such as RPM. Once (or if) Hitec put a maximum RPM alarm onto the Aurora, then this could be set to the limit that you want to discharge your batteries too.

I've just finishing coding up a version with mAH used and I'll start doing some testing soon - hopefully tomorrow if the weather holds out. Unfortunately the chip I'm using simply hasn't got enough program memory space free to both mAH used and GPS functionality - so I'll have to move to a larger (and slightly more expensive) device if its to have both functionality.

I'm debating if its worth the extra product cost to have GPS functionality (with mAH used) built in, or if its something that won't be used that often.

I would like to fit it onto all my aircraft though, as in the summer our flying field has large crops that jump up and grab the model occasionally. With a GPS receiver on-board, its simply a case of walking to the co-ordinates shown on the Aurora screen and fetching the model!

The problem with an on-board data logger is that it would add weight, size, complexity and therefore cost. Also the telemetry data port on the Optima doesn't send any servo+stick positions over, so it wouldn't be possible to log that information on-board the aircraft (unless of course you read the servo position of the throttle channel).

What I think is a much better solution is to do like burtgree has got and have a device that plugs into the back of the Transmitter module on the transmitter. This could be either two things, the first is to log straight to a SD card and the second, send the data to another device over Bluetooth (such as a phone). The advantage of a phone is that is has an inbuilt SD card/large memory unit and you can do a lot more too. Such as a live Google maps/earth plot of the aircraft. Very handy if its not possible to get the aircraft back to the field!

A Bluetooth to Android interface is something that I'll be developing sometime soon and if this current project is successful, and there is interest in an interface then I may speed up the timeline that I can get around to doing this.

Even though it very annoying that its not possible, currently, to tell the difference between the alarms, the alarms are not completely useless. I use the alarms as an alert that something is wrong and needs action. If the battery is flat (warning set by voltage), if I throttle back the alarm will stop (due to the voltage drop on the pack at high current levels) - so I know that I need to land asap. Also, contrary to popular belief, it is possible to read the current telemetry data while flying. Using the EzView screens (navigated to before the flight), I can hold the transmitter up in the air to my eye-line and quite easily read the screens when doing a straight circuit across the patch. Also the Aurora remembers maximum values for most of the parameters too (such as current, voltage, speed, altitude, etc) for quick post flight checks.


This telemetry stuff is something you don't realise how useful it is until you start using it! Even the basic battery voltage monitor has already saved a couple of my airframes from landing in the rough from exhausted packs. Like how 2.4GHz is everywhere now, I believe in 2/3 years time telemetry is going to become the expected norm on all aircraft. The only problem is, with the link security of 2.4GHz and the alert warnings from the telemetry data, it gives me less excuses for when I do crash!


Sep 28, 2011, 03:35 PM
Radio? Screwdriver!
Here's a shot of the Aurora screen showing an old 3S pack under load. Its been an unusually bright and warm day today, hence it was hard to get a good shot of the screen without getting light reflections.
Oct 07, 2011, 06:41 PM
Radio? Screwdriver!
Just a quick update. Did some high-current testing (16.8v @ 42A) and GPS telemetry tests on one of my electric aircraft in my fleet I upgraded. It worked very well.

Too well infact! Thanks to telemetry I can tell you that my Wot-4 Foam-e got to 50mph before flutter destroyed the rear tailplanes, causing them to part company and impact the ground at a top speed of 60mph! Ooops...

Due to recent work commitments (darn project deadlines), I've not had a chance to test out the mAH used feature. Hopefully soon this should ease up and I can continue developing. Once I have tested the mAH used function, its nearly ready to go!

If it checks out all ok, I intend to put 10 or so units, as beta units, on eBay at a near part-cost price, to allow others to play and test them out to see what they think (as well as publishing the source code+schematic for others to play and duplicate if they wish). Being a beta unit, I won't be able to offer any guarantees on them - however obviously I don't expect them to have problems and I wouldn't be expecting them to fail. The reason to release them is that I want others to play with them to see what they think and anything they would like different. Also I want to gauge the market place and see if there is a need/want for them - and if so continue developing.

Would be looking at around 20 (~$32 USD) plus shipping (for worldwide, would be around 5 - $7.78 for signed delivery, or ~3 - $4.67 for regular packet). That would include a unit to measure voltage (up to 20v), current (up to 50a), wattage and two temperature sensors (each up to 125C). Unfortunately no GPS at that price, as GPS modules are pricey - however there would be a GPS interface plug if you wanted to attach your own unit to it. After this revision, the specs will increase (upto ~30v and ~50-60A) and I also want to integrate RPM measurement from the speed controller. However I first want to gauge interest from these units to see if its worth while carrying on.

Would anyone on here be interested? Or is this a dead project with no real interest?


Oct 07, 2011, 11:25 PM
Registered User
Simon if the main interest in GPS is for finding a lost model, many people have discovered that simply using the Rx RSSI achieves that goal very well. The RSSI works as a directional indicator so long as you realise that the you have to walk at right-angles to where the Tx antenna tip is pointing. By using your hand/body as a shield you can determine which side to move towards.

IMO GPS is a vastly more niche interest than mAh so if you have to give up on or the other, I would think GPS is the one to go.
Oct 08, 2011, 02:10 AM
How many planes is too many?
groovejet's Avatar
Hi Si,

Looks great. Personally I'd like to see it work up to 70A or more since I have a lot of high power 3S planes that draw 60A-70A.
Mar 25, 2013, 04:27 PM
Registered User
richardglissan's Avatar
simon perhaps you could tell me if the hitec system is compatible with the frsky sensor hub and sensors?
all the best
Aug 24, 2015, 08:44 AM

hi, any uodating?

Hello, IS there any updating , or SCH?
Mar 12, 2016, 01:04 AM
Registered User
Guys, I like to build this watthourmeter......hope you can post the diagram and the source code.......I have some arduino mini laying around.

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