Accelerometers for Positioning

Hi, You first need to find out at what level the elevator is. So, you'll need some kind'o position sensor. (ultra sound or laser) Then you can slow down the cage and use the signal from the accelerator chip to control the slowdown or braking system. Then people don't get dizzy or sick in their stomachs. Why use an old 8051, it might become obsolete before you even get your board in production. There are much better controllers available. Best regards Jens

Hi there, I've fooled around a fair amount with accelerometer/microprocessor systems and you'll find that these sensors drift. For example you'll set everything up and it'll seem like everything is great and a while later the elevator will be stopping too high or too low. Because of this drift it becomes quite hard to accurately do the integration necessary to come up with an accurate position. I'd recommend using some sort of other sensor to detect the elevator's position in the elevator shaft and then use the accelerometer in a closed loop feedback to help the elevator slow down and speed up as quickly as possible without tossing people around inside. It might also be useful to know the weight of the elevator so the system can know when it needs to start braking so the elevator can stop in time without exceeding your maximum and minimum acceleration. As another option you could use the accel' to find the position but just have a smaller sensor at each floor so the system could re-zero itself. The longer the system runs without being recalibrated, the more this drift accumulates into significant positioning errors.

Oh ya...in continuation of my last comment. I am currently working with a 3axis accelerometer that outputs a digital signal instead of analog. I realize that you only need 1 axis but it's very inexpensive (~$15), TINY, and saves you from having to fool around with op-amps, signal conditioning and A/D conversion. LIS3LV02DQ from ST Electronics You can get it at Digikey.

Why use an accelerometer? It doesn't directly measure position or speed. Elevator controllers already decelerate the car when approaching a destination by much simpler and more reliable means than a microprocessor/accelerometer combo. Are you trying to invent something? Remember "K.I.S.S."

Why "reinvent the wheel"???
You would need very accurate input and a lot of 'chain` calculation to determine cab position.
Without updates, your calculated position would soon drift so as to be unusable.
Current systems work quite well using position sensors.