Accelerometer ... anyone use one ???

Don 944 LA · 02-08-2005, 09:19 PM

I have read through the threads and there is allot of mention of accelerometers, but I didn't come to any where they actually followed through with them.

seems that phidjets has some, and there are some rather pricey ones out there.

I would like to implement one as a moving/stopped indicator to disable video etc .. Frodoplayer has this function included (

Frodo ) ... and it seems that the liablility if these things are ever sold and there isn't something there is huge. Plus, having one that is difficult to disable would be nice ( hard, not impossible

)

Also, seems like they all have way too much capability. They could even duplicate one of those dashtop boxes to measure horsepower etc ... with the proper software ( maybe an addon to ODBII functions )

It would be nice to find one that is simple moving / stopped ...

anyway, just rethinking this and wonder if there has been any development

Don

Chris31 · 02-08-2005, 10:07 PM

Why not just use the handbrake to disable the video?
Use the speedometer? or even use the GPS (not very reliable though)

The accelerometer is not really that reliable for measuring true acceleration of the car. Rather it measure the total acceleration felt by the sensors, thats including the gravity. Go and buy one, tilt it up and you see it register 1g. Put the car on a hill and you see it register some acceleration even though the car is parked up. A bump on the road will see a change in acceleration and I dont think theres a way to remove this easily. Hit a bump once, a small acceleration is registered and it may continue seeing the car travellling at some speed even though you have already stopped.

There is a long thread about this, dont know if you already read it.

frodobaggins · 02-09-2005, 05:25 AM

Accelerometer would suck for this.

Scouse Monkey · 02-09-2005, 05:31 AM

Quote: Originally Posted by frodobaggins

Accelerometer would suck for this.

yeah and it would mean if your car was rocking for some reason

the video would go off. Accelerometers would be useful added into your GPS system for when it loses signal.

frodobaggins · 02-09-2005, 05:35 AM

Quote: Originally Posted by Scouse Monkey

Accelerometers would be useful added into your GPS system for when it loses signal.

Not really. You really need a compass and a speed sensor.

Scouse Monkey · 02-09-2005, 05:52 AM

Quote: Originally Posted by frodobaggins

Not really. You really need a compass and a speed sensor.

you can take your last recorded speed and direction from GPS and use a couple of acclerometers to detect changes. Bit basic but might help in built up cites.

Scouse Monkey · 02-09-2005, 05:57 AM

a digtial compass would save bit of work though

Nic · 02-09-2005, 06:13 AM

Quote: Originally Posted by frodobaggins

Accelerometer would suck for this.

i agree with this, an accelerometer isnt going to tell the differance between stopped and constantly moving at a particular speed, it also has no relavence to horsepower unless you factor other things in like weight

Scouse Monkey · 02-09-2005, 06:27 AM

i suppose you could always tell the cinrcuit to assume the car is stationary when it is turned on. then it can calculate the speed easily from that. But a handbrake sensor a billion times easier.

DeltaFX · 02-09-2005, 08:24 AM

One can filter a 2D accelerometer to get rid of gravity effect. The idea is to making it move just like it was on top of a joystick pushed forward->left->back->right(am I clear ???)

1-If the system is horizontal, not moving or @ stabilized speed, then the output graph is a circle, centered on (0,0)

2-If the car is on a slope, not moving or stabilized speed, the output is still a circle, but no longer centered on (0,0)

3-If the car accelerates/decelerates/turns, the pattern is a egg-oïde, offcentered like the circle in case 2(its gives the slope) and its great axis minus the original circle radius gives the real planar accélération.

The problem is tilting the sensors.....

StationRocket · 02-09-2005, 08:52 AM

I agree that an accelerometer by itself wouldn't work well for this application and that there are going to be better/easier ways to do it. But all the concerns about tilting, rocking and gravety are pretty moot. If the program that is monitoring it's output is written with an understanding of the world arround it (aka gravity and the laws of physics) than it could easily output meaningfull data like overall speed vice oscilations about a piont (rocking). The software could work like the dead reconing software that is used in inertial navagation systems. It needs to know what the starting conditions are and then it just summs up all the inputs to keep track of what is going on.

The cool advantage of implementing one would be the ability to track the performance of your car as you make changes to it.

MatrixPC · 02-09-2005, 09:27 AM

To detect the car is moving or not, the best sensor to get the info from is speed sensor. Well most car has that right?
The 2nd is Neutral switch sensor. Most/all auto trans has that right?
The 3rd and the easiest of all is, e-brake switch. Why not use this one? You can drive the car with the e-brake engage (well you can, but not recommended

)

Chris31 · 02-09-2005, 07:28 PM

Quote: Originally Posted by Scouse Monkey

yeah and it would mean if your car was rocking for some reason

the video would go off.

You got to spank your monkey nice and slow then