oXs +C custom PC board build

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RightRudder
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oXs +C custom PC board build

Post by RightRudder » Sun Nov 03, 2013 3:59 pm

Hi guys

I have done some testing using a precision current monitor IC for oXs+C and decided to go to the trouble of doing a custom board layout. I wanted something specific to discus launch gliders and the hall type current sensors are fine for electric planes and gliders but are just not suitable for precise low current monitoring such as in a pure glider. Also weight and size are critical in DLG's so soldering multiple boards together is less attractive. So by combining the MS5611 pressure sensor and a different current sensor along with an atmel MCU all on one board I have created a custom board to act as a vario/altimeter and battery monitor all in one. This I have set up to work with my shred RC single cell batteries which have a built in buck boost converter and charge circuit and it works awesome, with the telemetry on the Tx showing a fuel gauge type display indicating the remaining battery capacity in the DLG. I have set up voice alarms to warn me audibly as the capacity reaches low and critical levels. The concept works really well and consistently and I am quite pleased with it.

Edit: I included an extra input to monitor the pack voltage. This is not accessible with the shred RC packs but when running from a regular pack, the pack voltage can be monitored from this input so telemetry alarms can be configured on both pack voltage and used capacity measurements. It is safe to connect up to 3s LiPO.

Edit: I forgot to mention, I arranged for the pressure sensor to be at one end of the board and I can make a small metal shield for it so that it can be shielded from both light and RF and also with a small tube protruding from the shielded area which will allow the pressure sensor to be connected to a tube so that it will be easy to connect it to an energy compensation tube if desired. :D

I would like to get some feedback from the community to see if there is enough interest in running a small quantity of these for a group of people. It looks like for about qty 50 the cost of all the parts and PCB would be just under CDN$30. Then I would have to do the assembly myself. I haven't decided on what the final cost should be but it will have to include something for my time and for shipping, so as you can see, it is getting up there pricewise and I don't know what people might feel is reasonable or if it is worth the effort. I would be looking at investing $1350 or so to get a qty. 50 order going and obviously don't want to do that unless I have at least say 30 guaranteed to be taken right away. Since this is only something that would work for the Taranis / 9x with frsky telemetry crowd I don't know if there would be enough interest. If not I'll only build a couple for myself.

Here is a photo of the board.
DLG_oXs_C_1.JPG
Single board vario plus current sensor.
Joe
Last edited by RightRudder on Thu Nov 21, 2013 12:32 pm, edited 2 times in total.


dumbthumbs
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Re: oXs +C custom PC board build

Post by dumbthumbs » Wed Nov 20, 2013 5:36 pm

Does your board connect to an arduino, or is it completely stand alone (i.e. plugs right into a telemetry reciever)? I know you mention that it works with your shred battery, but would it work with just a single cell Lipo battery? Does the battery plug right into the board, and then you hook the reciver to the board for power. The reason I'm asking is that I usually use the 4 channel FrSky reciever, so I'd have to wire something up to power the board.

Also, the price, you mentioned it would be 30CDN for parts, so how about 40USD assembled?

Looks like a cool project.

RightRudder
Posts: 241
Joined: Tue Jan 15, 2013 9:41 pm
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Re: oXs +C custom PC board build

Post by RightRudder » Wed Nov 20, 2013 5:46 pm

My board works like this. You feed a regulated 5v in and it feeds that through a current sensor and back out to power your Rx and gear. I've arranged it so a standard servo plug brings the power to the Rx and the signal from that channel can then be used to control things in the oXs such as Kalman gain for the vario or in future I'd like to adjust the code to allow using the radio system to calibrate the current sensor etc. You can also connect a wire directly to a battery (up to 3s lipo) and monitor the pack voltage. The output from my board connects directly to the telemetry input of the Rx. I didn't include an analog output but could consider that for a future rev. on the board. I have just received the first two prototype PCB's from the fab house but haven't soldered the parts on yet as I am still getting set up for doing that.

EDIT: First prototype done, see photo of board in first post of thread above.

On my Tx the telemetry display is setup so that I can see the pack voltage (not with Shred stuff) and also a fuel gauge display showing remaining capacity in the airborne pack (based on a capacity set at compile time) The instantaneous current is also displayable. I set up alarms based on custom switches to play a voice warning when pack capacity gets low.

Joe


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