Sensor troubles…

So as we were putting the finishing touches on what we hoped would be our last prototype before the final production version we noticed something rather serious on the InvenSense webpage. The IDG500/650 (and the ISZ-500/650) that we are using are EOL (and the LTB has passed). So this puts us in a rather tight spot where we have a couple of alternatives:

Stay with the IDG/ISZ 500/650 – We could stay with the sensors we have and try to source as many as possible but this would leave us in an awkward position if we get more demand than we can source gyros.

Analogue replacement – We could find an analogue replacement that would replace the X/Y and Z gyros we have today (that are analogue). The best candidate for this is currently the new ST gyro L3G462A but it is still under Evaluation and we don’t know if and when it will be available. It’s easy to put in our current design but we are unsure about the performance and immunity to vibrations.

Going digital – The most attractive option but the option that requires most work is switching from analogue to digital sensors. This is a step that we wanted to take eventually but taking it now delays everything but we do get a chance to get a bit more up to date by putting in a MPU-6050 and maybe a pressure sensor. But we are not sure how the sensors will respond to the vibrations and ripples on the supply voltage.

Our current plan is to drop the old analogue sensors from InvenSense and start on the digital design using the MPU-6050. We will keep the analogue ST gyro as a backup plan just in case we hit into any problems with the digital version.

Do you have any other ideas for sensors or comments about the performance of the MPU-6050 or L3G462A (if you managed to get a sample)?

10 comments on “Sensor troubles…

  • Too bad, hope it won’t be a big delay. Can’t wait to get my hands on a prototype or production version of the Bitcraze quad!

    What I still don’t understand though is how to control the unit. Do you use IR? Of is it possible to use an RF transmitter like the Spektrum DX6i and just bind and fly?

    • I just read the post about the USB dongle, but still do not understand. Would this mean that you need a computer to control the unit. Does the OS matter since you need software to use it.

      Is it possible to bind and fly the unit with an Spektrum DX6i?

      • Hmm mayby if you get a simulator cable for your DX6 and connect it to your pc (will only work if they make the software compatible so you can change the controls in any way you wany to)

        If you need a spektrum radio to test it on i have 2 or 3 and i live close to you guys. I’d be happy to help you and get a sneak peek at the quad :D

        • The possibility to configure a custom gamepad/joystick/whatever is definitely planed. So if an RC controller has a PC cable it is going to be possible to use it.

      • Currently we are using a PC and a program we wrote in Python to control the copter. Although all of us are now working on Linux, we use only multi-platform libraries which means that it’s going to work on Linux, Windows and even maybe Mac.

        For controlling from a RC remote control we are thinking about it and the radio dongle is designed to be connected to a RC radio emitter via the PPM signal. However nothing has been done yet to implements that in the dongle firmware as we are concentrating of on the copter for now.

      • Yes we are aware of the problem that some people would like to be able to fly it without the need of a computer and would rather use a normal RC transmitter. We weren’t in the RC hobby before we started this so for us it didn’t matter. Therefor we added a possibility to hack together a cable and attach the radio dongle to a RC transmitter with a RF module port or training prot. It wount pe pretty at first but maybe later we could make a nice package such as this:
        http://www.hobbyking.com/hobbyking/store/__17631__2_4Ghz_SuperMicro_Systems_Futaba_Module_.html

        None if this has yet been tested, but we are confident it will work however a bit “hack-ish” in the beginning.

  • Have you considered the Invensense ITG-3205? Apearantly that’s what Horizon/Eflite/Blade used to replace the IDG-650/ISG-650 combo in their mCP X V2 micro collective pitch heli. Haven’t checked the specs on it, but it flies pretty nice and holds the tail very well compared to their previous model so I guess it would perform quite well in a quad as well.

    • The ITG-3050 would indeed be the logic replacement for the accelerometer but as it forced us to redesign the board for digital sensors we might as well go for the MPU-6050 that includes the accelerometer and would reduces the number of component (and could make place for more sensors ;-).

  • For using an RC transmitter with the current solution I would recommend the following trainer port/PPM to USB adapter:
    http://www.autopartner.se/hitec-usb-flight-simulator-interface-p-14254.aspx?externalsearch=1

    There are other alternatives, but this one works great in Linux (and other operating systems as well) and is recognized as a USB HID Joystick with, if I don’t remember wrong, 8 axis, so it’s pretty easy to use). It is actually a repackaged Multiplex RC Joystick which costs almost twice as much.

    I’m also pretty close by and would love to see the quads in real life. ;-)

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