Any Electronics Gurus Out There?

[npalen]

The picture is a closeup of one of the output LED clusters on the laser receiver shown in the thread below.

It would be interesting to automate the manual system by picking up the signals from the receiver output LED's to control a solenoid valve. The solenoid valve would basically duplicate what the operator does in operating the remote valve on the tractor while watching the receiver lights. The lights form arrows indicating whether the box blade needs to raise or lower to stay on grade.

Someone in another thread suggested using an opto-coupler to "pick up" the LED's and then amplifying to a level that would operate the coils on a solenoid valve. This would probably be less than five amps on the 12 volts.

In doing a little online reading, it also sounds like four or five photo darlington transistors strategically mounted on the receiver to sense the LED outputs might also work.

I'm wondering if a PLC (Programmable Logic Controller) might also be part of the mix in that it would facilitate experimentation to fine tune the response. Variables such as the amount of on time and delay between pulses for the
solenoids would be examples of fine tuning the system.

I realize that this system would not be as good as the automatic systems employing proportional hydraulic valves but the cost would be much lower.

Would be fun to hear thoughts from you guys and gals.


https://www.tractorbynet.com/forums/build-yourself/423542-inexpensive-laser-grading.html

 

[hiddentacocatneddih]

I work on automation for a living. Reading the LEDs would be possible but would be finicky at best for the home brew. Best bet is to find a way to wire the led outputs to digital inputs on a controller. The easiest way to use the tractor hydraulics is to find an actuator to move the control level on the tractor.

You may be able to run it off an arduino which is a $20 microcontroller.

 

[npalen]

I was wondering about the arduino boards. Are any of them capable of 3-5 amps @ 12 VDC or would an external relay be required?
Thanks for your input!

 

[hiddentacocatneddih]

No and no. 20mA max iirc. 5VDC. You would need a few devices to step up to be able to drive a relay. A 12VDC actuator may be too slow to be practical. I use one on my chicken coop and it takes ~30 seconds to cycle one way (12 inch stroke)

 

[MossRoad]

The hard part is gonna be how to make it operate smoothly and not stutter your hydraulics rapidly.

 

[npalen]

Yeah, I was wondering also about the actuator. Probably would need a response time in milliseconds in order to keep up with normal operating speed. For example, a distance of about seven feet per second is covered at just five mph. A solenoid valve would be affordable given the advantage.
I don't know if the receivers internal wiring can be accessed without damaging the case but may be possible. What would be finicky about reading the LED's--sunlight interference perhaps?

Edit: The LED output is extremely bright even in daylight.

 

[aczlan]

Personally, I would open the case and find a way to wire a pair of leads to each of the sets of LEDs.
I would find what voltage the LEDs run at, then use that to run a pair of small relays (both single pole, normally open, capable of handling 12 volts on the switch side and with the coil voltage at whatever voltage the LEDs run at), then feed a common and the up and down output from those relays to an external connector (such as a headphone jack).
Then go from the headphone jack to a heavier pair of relays that have a 12 volt coil and are heavy enough to handle whatever solenoid you are using to control the hydraulic valve.
That way, all you have to do is disconnect the headphone cable and you can use the receiver in standalone mode.

Aaron Z

 

[npalen]

The hard part is gonna be how to make it operate smoothly and not stutter your hydraulics rapidly.

Was wondering about that and whether reducing the voltage output to the solenoids would be effective or destructive. The pump output on my Kubota and probably most compact tractors is fairly low but I suppose it is somewhat relative to the valves gpm rating.

I've read that the smooth response of proportional spool valves is partially attributed, in addition to variable voltage/current, to shallow grooves cut into the spool lands to afford a gradual start of flow when shifting the spool. That makes we wonder if a conventional valve spool could be tweaked with a bit of careful mod.

 

[hiddentacocatneddih]

Rexroth prop valves come with either a amplifier card or on board electronics to drive the current curve to the coils. They can be 4-20mA or +-10vdc. I dont think you'll be able to spoof a prop valve easily. your internal plumbing with the 3 point will make it harder to tie into. Normally what we use in industry to control the characteristics of how a prop valve moves is either a PID controller, stand alone or a function in the PLC or something similar, GE for example has position controller blocks specifically. Setting up a 3rd function cylinder would be easy. I've never used a prop valve on a single acting cylinder. Iirc almost all 3 points are single acting.

If you tried to spoof a prop valve with relays on a directional valve, you will have to dampen the response to prevent chatter with the relays. Relays are boolean and typical prop valves are analog by nature.

 

[npalen]

Rexroth prop valves come with either a amplifier card or on board electronics to drive the current curve to the coils. They can be 4-20mA or +-10vdc. I dont think you'll be able to spoof a prop valve easily. your internal plumbing with the 3 point will make it harder to tie into. Normally what we use in industry to control the characteristics of how a prop valve moves is either a PID controller, stand alone or a function in the PLC or something similar, GE for example has position controller blocks specifically. Setting up a 3rd function cylinder would be easy. I've never used a prop valve on a single acting cylinder. Iirc almost all 3 points are single acting.

If you tried to spoof a prop valve with relays on a directional valve, you will have to dampen the response to prevent chatter with the relays. Relays are boolean and typical prop valves are analog by nature.

The thing that makes me think a conventional solenoid spool directional valve would work is that I can do it manually now with a manual lever operated valve. Just have to drive slow enough to watch the lights and react to stay on grade.

Planning on using a remote 3-position 4-way solenoid valve that would be powered directly off the pump or via a remote manual valve with detent. I hadn't considered using the 3PH hydraulics.
Thanks for your input!