Laser receiver detections and Arduino PWM control of solenoids

Thread Starter

deere_chaser

Joined Nov 29, 2020
4
This is the only site I have found any talk of laser receivers, I know this is a huge post but I am just trying to be as complete as I can with the info. What I plan for my project to do is read a red rotary laser (link below) to tell the Arduino/ other board that the position is "very high" "kind of high" "spot on" "kind of low" "very low". If I can get that to read, then it would come down to the logic - When the laser is striking the "very high" portion of the receiver it sends a signal to a pin and the Arduino reacts - same for the other positions. So in the "very high or very low" section the board would put out a high duty cycle PWM signal to a MOSFET or solid state relay which controls a solenoid (12VDC) that directs hydraulic flow. When the laser strikes the "kind of high or kind of low" section the logic would change to a lower duty cycle PWM signal as to be not so aggressive. When the laser finally strikes the "spot on" section it stops all output control. Obviously hysteresis would be an issue that I think either code/logic, hydraulic flow control or ground speed would help solve or limit. I will already have a laser receiver designed for a wide area reading (link below), but I am only building Automatic control. I don't want to tear apart the purchased receiver due to cost and it would make the R&D/code much more difficult - but I am buying so I have a wider range (reading range) of the receiver and not building a setup for that yet too or fly blind with only 6 ish inches to read the laser.

My idea for the receiver is as follows -

5 light/ laser detectors - Part# B01M8PFZRC from amazon - more "eyes" added to the 5 boards/sections for a wider range of strike area - may break down into more sections like 7 or 9 possibly.

[ ] Very high level - high duty cycle to get the tool to move very quickly (coarse adjustment)
[ ]
[ ]
[ ]
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[ ] Kind of high level - medium/low duty cycle to slow the movement down (fine adjustment)
[ ]
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[ ] Spot on level - Stops all output control to solenoids
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[ ]
[ ] Kind of low level - medium/low duty cycle to slow the movement down (fine adjustment)
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[ ]
[ ]
[ ]
[ ] Very low level - high duty cycle to get the tool to move very quickly (coarse adjustment)

The system, at least on paper, will insist upon itself to get to and maintain the laser strike on the "spot on" eye. The tool this will go on will be like a bulldozer or a road grader with hydraulic adjustment, where the blade will either fill in a low spot or move a high spot.

Factors/questions
Physical factors - hysteresis, reaction time, accuracy (not looking for crazy tight tolerances but don't want it super lazy). I can always slow down and I plan to have the work area halfway close to the target before starting the automatic control.
Electronics - physical capability, design of receiver, overall plan, maybe having a dial and code for aggressiveness and an input for a "stop" "run" "hold" switch to override the control or make it start working.

Lasers-

https://www.spectralasers.com/product/lr50-laser-machine-display-receiver/

https://www.toolbarn.com/dewalt-dw0...jC2sXJD5Z2STFzm4in6eTzswi2w-jwiBoCEtIQAvD_BwE

Links to the other threads -

https://forum.allaboutcircuits.com/threads/rotary-laser-level-receiver-circuit.155616/

https://forum.allaboutcircuits.com/threads/laser-receiver-detector.65663/
 

jpanhalt

Joined Jan 18, 2008
10,941
Welcome to AAC and thank you for the links.

As for your proposal, I don't see the need for separate "circuits" to handle high, medium, small, and no offsets. That's what PWM is for doing. In other words, I would design for proportional control. I would also consider that you may/will need to add dither to your valve control to get small and/or smooth corrections.
 

Thread Starter

deere_chaser

Joined Nov 29, 2020
4
Welcome to AAC and thank you for the links.

As for your proposal, I don't see the need for separate "circuits" to handle high, medium, small, and no offsets. That's what PWM is for doing. In other words, I would design for proportional control. I would also consider that you may/will need to add dither to your valve control to get small and/or smooth corrections.
Thank you! Hopefully we can get this figured out. The separate circuits in regards to the offsets are for laser signal transfer to the board only. The 2 PWM signal circuits will control raise/ low only. I had never heard of dither, I appreciate the suggestion. I think it will greatly help the functionality of the control.
 

Bernard

Joined Aug 7, 2008
5,719
Photo transistor KDT00030ATR looks interesting; peak response @ 630 nm, 50% @ 500-650 nm. Small surface mount, .8 X 1.2 mm. Newark 1- $ 0.201. 9000-$ 0.203;
Rochester 1 @ 0.1972, 25- $ 0.1932.
My want list is too short to justify an order at this time.
 

Thread Starter

deere_chaser

Joined Nov 29, 2020
4
Photo transistor KDT00030ATR looks interesting; peak response @ 630 nm, 50% @ 500-650 nm. Small surface mount, .8 X 1.2 mm. Newark 1- $ 0.201. 9000-$ 0.203;
Rochester 1 @ 0.1972, 25- $ 0.1932.
My want list is too short to justify an order at this time.
I did some digging on the specs of the laser I have VS one used for this type of work. I have a Dewalt unit now, which is a “class 3” and the one typically used is “class 2”. I am having an issue with determining the nanometer rating for a class 2 or 3 lasers, for the correct sensor, not to mention finding a sensor to read the laser and not ambient light.
 

jpanhalt

Joined Jan 18, 2008
10,941
On further thought, you can affect smoothness by adding flow constrictors to your hydraulic lines. When I added a blade for pushing snow to my skid steer, that's what I did to get smooth and easily adjusted increments. Of course with less restriction, changes are faster. Unlike a human, your automated system cannot see ahead, but it can react quickly, so adding flow restriction might alleviate "operator"-induced oscillations.
 
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