Accelerometer uses? Electronics-geek stuff

[skelstar]

Im an electronics eng. and I have been having a bit of a play with an IC (chip) that has a 2 axis accelerometer built into it. What this means is that it measures the amount of acceleration/force in two seperate directions (outputs an analogue voltage).

My question is: Can anyone see a use for this on a bike...ie. on the track?

My initial idea was to use it on a bike to measure acceleration/decceleration and maybe work out cornering speeds and forces. This thing would be able to tell you how hard you are cornering. I thought it could be used to record lean angles but due to the construction of the device its effected by gravity. What I mean by that is that if you hold the device flat, then tip it over 90 degs the output voltage will change. The bike tips when it corners and therefore the devices output changes with both gravitational force and centrifugal acceleration.

So....any thoughts?

I figured with a bike that has a digital speedo/tacho you could collect some interesting data. Would be difficult to collect realtime, but maybe good for practicing on a particular track. Have the same type of unit on two different bikes and it would show what each bike is doing?

[skelstar]

Datasheet for said device is here:
http://www.ortodoxism.ro/datasheets/...L150_250_0.pdf

[Motu]

I use one for brake testing every day...I guess I could turn it backwards?

[skelstar]

You could. You could put four of them on your bike .

[bugjuice]

you could really use a 3rd sensor, to measure outer g's too. There's the forward and backward motion, tilt/lean motion, then the 3rd being the lateral forces pushing down the bike as you're cornering

[skelstar]

Well imagine the chip has two sensors that measure in the same plane as the chip. X being forward and backward, Y being side to side. The X part is easy, the chip doesnt change its' attitude' in that plane (unless monos), but the side to side stuff is harder. Unless you can stop the chip/package from tipping with bike, the Y axis is never going to be in the same plane as the lateral forces due to cornering. There will be a component of gravity too. The only way I can think of getting around this is by putting it on your helmet as you head doesnt/shouldnt really tip with the bike.

[RantyDave]

I have been having a bit of a play with an IC (chip) that has a 2 axis accelerometer built into it. [snip] I thought it could be used to record lean angles but due to the construction of the device its effected by gravity.

Ummm, skel, gravity is an acceleration. As for actual practical uses I dunno but will leave it in the back of my head and see what we come up with.

You could stick one at either end of a shock absorber and use the difference to derive some description of behaviour curve. A nice graph showing what it is that an Ohlins does that a generic doesn't? Repeatable shock settings?

Should be pretty trivial to use an accelerometer to do halfway scientific testing of brake pad material...

Any plans on what you're going to use to collect the data?

Dave

[skelstar]

Yeah, know about Grav and acc. I have it set up so that if I start the device, and tip it up 90deg it measures 5VDC, tip it back and then back another 90degs (ie 180deg in total) it reads 0VDC. Its all gravity. A guy at work is wanting to use it as a yacht heeling/lean indicator. Hence my thought about bike lean angles.

Collection via a micro. A PIC18F252 to be precise. Probably just logging the data and spitting it out via rs232 back at the pits.

Like your 'shock' suggestion though.

[Motu]

You could. You could put four of them on your bike .

My brake tester also checks for lateral forces too,it picks up brakes pulling to one side.Not really useful as it only measures max and average results.

[RantyDave]

A guy at work is wanting to use it as a yacht heeling/lean indicator. Hence my thought about bike lean angles.

Ah, right. Difference is that a heeled yacht is going in a mostly straight line whereas a bike going round a corner is experiencing centripetal acceleration. In fact if you measure the heel on a bike using an accelerometer it'll measure zero since the forces (torques) have to all equal out to prevent angular acceleration round the roll axis ... otherwise known as falling over.

You could measure tip-in accelerations though. You'd get cool numbers from high siding too.

PIC is a good choice.

Will think some more about characterising shock absorbers.

Dave

[skelstar]

The way this thing is constructed, it will measure gravity at rest. If I sit it on the desk, I can tell you which way up it is based on the voltage its spitting out. If I stick this on the deck of a yacht, it will tell you what the heeling angle is. Static. The construction inside the chip amounts to something that behaves like a strain guage (like a modern electronic scale). Does this mean I have to allow for different gravitation constants?

An idea for use of the data from riding around on a motorbike. Just demostrating the lateral forces:

[cowpoos]

if mounted on a wheel it could measure the gyroscopic forces... lmfao....lol.....bwaaaaaaahhhhhhh....he he he he.....lol

[2much]

I'm guessing these are used in G-tech meters. I've used a G-tech meter on my car a number of times, and it would work the same on a bike. It can give you 1/4 mile times, 0-100 times, cornering G's, braking G's, etc...

Here's the info on it: http://www.gtechpro.com/

[skelstar]

Oh dear, I kinda expected that poos. Do I get an assist?

[sAsLEX]

I am nearly an Engineer, and am building a Inertial Navigation system using Micro-Electromechanical Systems accelleromaters and Gyros with GPS updating using Kalman filters.

Will give pitch roll heading basically the full navigation solution, but the MEMS thingys have quite bad drift in the gyros etc which is why I am using the GPS to update its initial position estimates regulary to limit the effect of the drift.

Was going to trail it on my bike depending on how small I get it.