Unfortunately, I did not let go of the handle bar...
You see plenty of videos of newbies on motorcycle that can't bring themselves to let go of throttle...so you're not alone.
1. What CPU do you recommend?
2. Is the supercapacitor arrangement described above logical?
3. How do you see adjusting the G force sensitivity? Programming? Using a potentiometer?
4. Recommendations for means to record/capture the G force voltage output so as to make adjustments to the settings? This is on a rototiller. It naturally vibrates and constantly moves in all three axis directions. It is the severe acceleration move events to be controlled.
Unless you really want to use this as an excuse to get into programming, I don't see a need for a CPU at all. You can do this with analog electronics easily enough.
Your issue isn't G forces - your issue is the length of time the G forces are present, and that is what you should focus on. The tiller bouncing around is going to make an accelerometer go crazy, but all forces not lasting long and the tiller not moving anywhere fast.
Then you hook onto a rock or root and you get a long hard pull that gets the tiller moving. That long hard pull is likely to be fewer Gs than the bouncing around, so I don't think looking for peak Gs will work.
Build a circuit that will ignore the bouncing around but is sensitive to the relatively long lurch. That means a low pass filter on the output of an accelerometer, connected to an amplifier that drives a relay.
Here is how I would do it
- Use a battery - at least until the rest of it is working. You can screw around with the magneto if you want later.
Use a single axis accelerometer with analog output - you only care about the forward and back motion
Feed analog signal to a buffer (amplifier) - unless the sensor has one built in
Send that signal to a active multi-pole low pass filter with a 3db cutoff around 4 hz. Use filterpro free from TI.com to design the filter. (http://www.ti.com/tool/filterpro)
Send that signal to a op-amp circuit, make the gain adjustable using variable resistor
Drive a relay with the op-amp output (buffered through a N-MOSFET).
The gain setting on the opamp will set your threshold.
If you swap in a variable resistor on filter, you can also dial in your frequency, but 4Hz sounds OK to me if it is a steep filter.
The relay will have the mother of all hysteresis's so once it shuts the motor down, it should stay down for several hundred milliseconds. This will allow you to set the threshold high enough that it isn't cutting out every two seconds.
When you're done, patent and sell this feature to the tiller makers. When you're rich, I want a few bucks in return.Last word - turning the ignition on and off will put fuel into exhaust system, and then detonate it. Wear appropriate eye and ear protection.