Sensors

[cosmiccloth99]

I have a question regarding what sensors would be best suited to use for something I am building. I need to be able to determine the depth of an excavator bucket while digging. I have a few theories on this but I would like to get some input from community members here.

[Gallymimu]

you need to be more clear on your requirements:

depth with respect to what?  The ground? the tread? Sea level?
how fast? how often? how accurately? how far and how close?

all of these will impact recommendations:
ultrasound
angle of machine joints
camera
lidar
midget on a rope

There are a lot of options.

[LabVIEWguru]

I was going to suggest a spring-wound encoder, but I like your midget-on-a-rope a lot better.
Of course we'd have to calculate where we attach the rope to the midget in our calculations.

[cosmiccloth99]

I had really hoped someone would confirm my belief that the midget on a rope would be feasible, however, my initial plan was to use a midget in a bikini on a rope. The depth measurement would be relative to the ground. I would need accuracy to within a few inches and it would need to be real-time to prevent an operator from digging too deep or shallow.

[pickit2]

might work if the rope was calibrated.
the then you would need to keep the weight of the midget constant.

Question how do they work out how deep they are going now, as I
seen a trench dug, then a concrete delivery was made with just the right amount.

[cosmiccloth99]

Well, we have a few different methods that we employ to determine depth. If digging a trench that requires slope then we use a laser and set it to the percent of slope required. If it's going to be a constant depth trench a laser can be used or you can also just use a tape measure to determine the depth. I have considered building a receiver for the laser as is commonly done on dozers and graders but due to the many points of articulation on an excavator it would be a nightmare just figuring out where to mount it out of harm's way. They have GPS units for excavators that are insanely costly but they show you depth angle and pretty much make even the most complex tasks simple. I'm not looking to build anything that complex I would just like to figure out the best way to determine the depth below ground my bucket is.

[pickit2]

I would look at Drone GPS Tracker as a starting point.

[solutions]

On a toothed bucket, you need to define where the depth actually is...

You also have the problem of loose fill tumbling back into the hole.

The best way is encoders on the machine joints, IMO. Because of machine size, they are going to be damned expensive.

My second choice would be a slung-by-an-armpit-harness, hip-disarticulated, red-haired, female, midget...that would enable the universal shop metrology standard of getting the measurement to within one RCH.

[Gallymimu]

I'm on board with the encoders or angular sensors on each joint, they will have to be rugged, but at least you are keeping sensors out of the hole and rocks.

although if the exavator isn't level it might not work as well.  I suppose before starting you could put the bucket on the ground and zero it.

[cosmiccloth99]

Thank you all for your input, I greatly appreciate it.

[towlerg]

It's a no brainer, the midget ever time.