fechter wrote: ↑
Jul 25, 2018 10:46 am
I tried using a rolling ball tilt switch on another project and it failed due to too much current on the contacts. Only a few mA was enough to trash it, so for sure you need a transistor to boost it. They might not work well on a bike that's going over bumpy ground. The ones I've seen for brake lights looked more like a pendulum. You might be able to use a sensitive micro switch with a weighted pendulum to activate it on deceleration.
So, I now have a pair of adafruit ball tilt switches.
The experiment, if I get time, will be to wire them in parallel.
Also to place them in a 30deg vee. Thats the shape vee, not a
netname. Vee laid almost flat and parallel with respect to the
roadway, excepting the tilts needed to detect deceleration.
Each arm also aimed slightly aside, not quite straight ahead.
I figure 2n3906 NPN might do for the switching. Pull the base
up toward 1 cell with 33K, more or less? Let either of the tilt
switches shunted across VBE turn that transistor off. Maybe
this application would prefer a slower transistor? I got some
oldschool 2n2222 in TO-18 cans. Proven useful since 1962...
This limits the mechanically switched current and voltage to
100uA and 0.7V, hopefully low enough to cause no extra wear.
Requires both dislodged from rest to turn the transistor ON.
Between the vee shape and transistor saturation, perhaps
some debounce will be achieved? That's the experimental
part, not that I'm worried the described circuit is no good.
Just don't want to make complicated where simple will do.
Underneath the seat might be a location better insulated
from vibration than the kickstand? But need a different
sort of deadman switch to insure a drainproof turn-off.
Don't know what sort of switch might be suitable...
--- edit early AM Aug 1st ---
And it works (w 2n4401), on a breadboard anyway.
Bent to about 60 degrees Vee, with a 30 deg uptilt.
Not so glitchy as I was worried, but road test might
reveal otherwise. An arm swing limited by clipleads
just can't fake.
VCEsat and 100 series ohms restrict LED to <20mA.
Voltage drop across my Red was about 1.95V...