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Messages - Adam 'Weirdarms' Wiggins

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New Product Ideas / Re: Inertial Measurement Unit shield
« on: October 13, 2012, 06:00:12 PM »
Repost of what I mentioned on the 3-phase BLDC topic.

Someone suggested in the kickstarter comments for the project an all in one 9-axis chip ( which looks ideal, it seems to be about $17. A simple shield with that (maybe some other telemetry like a I2C temp chip and/or barrometer).

I had not thought about really high powered motors, that's a good point maybe looking at the modular power boards idea first is the best way to start. I'm currently looking for some good info on algorithms and general software design for 3 phase BLDC motors, so if anyone has any pointers please pipe up.

As for the IMU, someone suggested in the kickstarter comments for the project an all in one 9-axis chip ( which looks ideal, it seems to be about $17. A simple shield with that (maybe some other telemetry like a I2C temp chip and/or barrometer) and a connector for an off-shield GPS module would be ideal.

Maybe we should split the IMU into a new topic?

A varient which might cover the points both of you have raised is to have a very simple shield that then provides a connector (outside of the stacking profile) for a power module that has the MOSFETs, etc. That way you can have one shield that can you can plug different rated (10A, 30A, 100A) power modules into and down the track probably simpler AVR (or other microcontroller) boards that the power modules can plug into when you don't need the stacks. The power modules could be 'side-cars' to the shield :)

The thing I don't like about this is that the shield is very basic, I don't think it would really be much beyond a connectors/tracks and I think in most cases you are probably going to have a single ESC made out of one power module and one micro. In that case it just adds cost and probably space for little gain. For example there are not enough ADCs and timers in general to do more then one ESC per AVR.

If you look at commercial ESC they are pretty small, for example I have a 30A one with all the power fets on one side which nearly fix in the square profile of the TinyDuino and it uses 5 fets per phase rather then just two which clearly fit inside the profile. The other side has the AVR, etc.

I think we could for 10A probably do a single shield (no stacking the MOSFET packages are too high and probably need a heatsink), in the standard footprint. I might look at how feasible such a design is. I think both a straight (top of the stack) shield and power module side-car shield have their usage in different domains or stages of development at any rate.

New Product Ideas / Blushless 3 Phase DC electronic speed controller shield
« on: September 23, 2012, 12:25:57 AM »
This might be a bit of a stretch but for a while now I've been looking for an open hardware design for a 3-phase DC blushless motor electronic speed controller (ESC) for hobby engines used for multicopters. The reason is you can get these things cheap but they are the PWM servo interface style controllers (some can be hacked) with no telemetry information, and no I2C. Most of these controllers are Atmel chips and more then capable of providing speed information and in some cases power usage, all of which would be handy information to have feed back to your flight computer.

Starting with a smaller motor rating (say 10A) it should be possible to make a shield (might require a headsink or to be the top/only shield, my wish list would be:

* Battery draw current sensing.
* Temperature sensing.
* 3-phases driven by N/P mosfet pair, and voltage sensing for cross-over voltage detection, and PWM output to drive the mosfets.
* Voltage sensing of battery input.

Atmel have a lot of design notes, so it shouldn't be too hard. I'd be happy to provide some ideas regarding design and software. I think you could do a range of shields to provide kit based development for various parts of a multicopter, R/C plane, or otherwise for things like the flight computer with IMU (3-axis gyro/accel/compus), wireless communication, ESCs, etc.

Let me know if it sounds interesting or not, I have seen on kickstarter some interest in the IMU sheeld which I personally would be very keen on.

Cheers, Adam

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