Detecting motion of a platform

I'm hoping for some guidance and options for a sensor that will work for my application. I'm looking for a super low power sensor that will tell me when a platform is moving. I want to enable an ultrasonic range finder, but only while the platform is in motion. I've thought of using an accelerometer, but it seems like this will only tell me when the platform starts or stops. I am looking for a sensor option that will be able to provide a "wake up" signal to an Arduino board whenever the elevated platform is moving in any direction (x,y or z axis).

Any suggestions would be greatly appreciated! I am stumped!

I have a strong feeling this is an XY problem......

No, it's an xyz problem :smiley:

Haha! Fair enough, I was a bit vague in my initial post. Here is the entirety of the problem. I have a motorized platform that can move in the x, y, and z direction. I want to tell the vehicle when it is within a given range of an object and sound an audible alarm.

I was planning to use ultrasonic sensors for the rangefinding devices (but I'm not married to this idea). However, if I run these all the time I risk running my batteries down quickly. I'd like to find a way to ONLY activate the rangefinding portion of the code when the vehicle is in motion. The vehicle is moving less than 1% of the time it is being used and by turning the sensors off I should be able to reduce battery consumption. Other alternatives for achieving my end goal are MORE than welcome!

Thanks for the quick replies, any input is much appreciated!

I want to tell the vehicle when it is within a given range of an object and sound an audible alarm.

What vehicle? What object? What range?

So what moves the platform. Monitor that?

Unfortunately I cannot modify any of the wiring currently on the platform so the sensor/alarm/power supply all has to be self contained. I'd like to provide a chirp when the platform is 3 feet away from an obstacle (likely a flat wall, human, girder, get the drift) and a sustained beep when the platform is less than 6 inches away.

well it might not be ideal to have a complete standard size arduino on the platform, so probably i would say one of those miniature ones they have had advertised with a small rechargeable battery with relay switch to a recharger for when platform isn't being used.

And you mentioned you cannot change the current circuit and it needs to be self contained, so if that's the case the micro controller you put on the platform will require a wireless shield.

If you CAN change the current circuit im pretty sure you could find a way to power a micro controller on the platform taking analog sensor readings by proper arrangement of the wiring without needing to transmit the readings wireless.