Technical details for those technically inclined.
Total weight is 34 grams.
USB to UART Bridge Datasheet and App notes
Axon II printout (a 1:1 ratio printout of the Axon)
ATmega640 pinout quick reference
The default battery configuration requires just one battery to operate the Axon II - just like the original Axon. All Axon IIs are manufactured and shipped in this default configuration. You can also attach additional batteries in parallel on the unregulated battery bus (all batteries must be the same voltage, battery type, and charge level) as needed.
The dual battery configuration allows you to use a small stable battery for powering sensors and the ATmega640, while a much larger less stable power supply can be used for motors and/or servos. In this configuration, the battery meant to be regulated goes on the BAT header, while the other battery goes anywhere on the unregulated battery bus. To enable this configuration, flip over your Axon II and remove the small solder trace between BAT and G5. This trace acts as a high-current jumper.
For an example on how to change the battery configuration, please see this video:
Absolute minimum required voltage is 5.35V. If at any time the voltage drops below this amount, even for a milli-second, the Axon II will reset. The recommended battery voltage is 6V to 7.2V (a 6V 1000mAh+ NiMH battery works great). Maximum voltage at 16V, however most servos will have reduced lifetimes at voltages above ~6V and can quickly fail at voltages ~7.2V+.
There are three power buses. ADC pins 0 to 15 are regulated at 5V, while all other pins are directly connected to your battery. There is also two 3.3V output pins (see current tolerances).
The Axon II has polarity protection features, meaning that it is designed to protect itself if you accidentally plug your battery in reverse. However, it will NOT protect any external component(s) connected to the unregulated battery bus.
The 3.3V power bus is NOT protected against polarity or power surges, so be careful or you'll fry your USB.
This is how the pins are set up in terms of power.
Pins Voltage Bat battery (input) G5-B7 battery H7-L7 battery A0-A2 5V regulated 0-15 5V regulated 3.3V 3.3V (output) G ground - ground
The Axon II has been tested to handle at least 6A on each power bus, but can in theory safely handle up to ~13A. Placing your high current draw components near the battery can up this number. This limitation is entirely based on power bus tracing thickness, meaning that if you require higher currents you must make your own separate power bus. Using multiple batteries distributed along the power bus can reduce current across individual traces.
Individual I/O pins can supply about ~20mA power, each. Exceeding this number could damage/fry the I/O pin.
The Axon II also has a special regulated 3.3V output bus, great for components or sensors that require this low voltage. This pin cannot supply more than about 73mA, or 90mA if you aren't using USB. If you find that USB becomes unstable or fails to work when using this output, make sure you aren't overdrawing current and place a 4.7mF tantalum capacitor (polarized) between 3.3V and ground. Don't use any device with 3.3V that is likely to transmit a power surge during use.
If you exceed the specs of the 3.3V output, you can permanently damage the USB. Do not just plug anything into it without first verifying the current draw is ok and that no voltage transients will occur.
You must also keep in mind the current tolerances of the included Hitec 572125S on/off switch.
Axon II: AutoDesk Inventor CAD Files (1.7mb)
No Sketchup CAD files are currently available. Let me know if you made one!
If you'd like to create your own CAD, feel free to download the Axon II texture image.
If you have a SolidWorks design of the Axon II, let me know!
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