John Deere remote SCV control

[m_elias]

I’ve been investigating what is required to control the electronic JD SCV (remote hydraulics) from AoG or one of the OpenGrade/X variations.

@ChrisC has shared a screenshot of the wiring schematic on his OpenGrade github page

GitHub - Chris8960/OpenGrade3D: .INO to run opengrade3D to a danfoss valve

Here’s another screenshot from Chris showing other Option lines and possible SCV 2 & 4 control inputs? My connector only has the 7 pins installed (A-D, G-J).

It shows the connections at a 9 pin Deutsch connector. I believe that’s one of the implement connectors at the hitch, which goes to a 10 pin Metripak behind the cab (underneath the back cover). The pins labels for both are the same, eg pin A is 5V source on both connectors.

You just loosen (not remove) the two bolts under the rear fender on both sides to remove the panel/cover.

I’m prepping a test board with potentiometers for both scv #1 & 3 so I’ll report back with those results but in the meantime, has anyone else done this yet?

[m_elias]

Most of the information I have comes from @ChrisC on the OpenGrade thread.

He first mentions the electronic control method here.

Grade control

I originally was going to look into can, but there is a simpler way… all deere, cnh, and cat tractors made in the last 15 years come with a scraper interface… basically you plug and play. DAC 8000 Wired - Manuals Not sure of the wiring for cnh or cat but here is the configuration of deere [IMG_20211024_123559] It is a 5v analog input that doesn’t like extremes. So 0-2.5v controls one direction and 2.5-5 controls another… CNH and JD have a dead band from ~2.25 – 2.75 volts, this varies some …

Then at post 496 there’s another bunch of details.

Grade control

It’s a deutsch type connector [IMG_20211226_163440] Yes plug it in with the tractor off, if you mess up it will throw a code that has to be deleted before it will work again. The scv acts like normal except when detented full forward. When detented it goes to automatic, everything else acts like a regular scv.

It sounds like the JD expects voltages of 0.5 - 2.25 for one direction and 2.75- 4.5 for the other direction. There’s some deadband in the middle (2.25 - 2.75). So basically, at 2.5V there’s no oil flow, and as the voltage goes further from that 2.5V (to either 0.5 or 4.5) there’s more oil flow to the remote ports.

If you’re experimenting with this, make sure to leave provision for disconnecting and restarting the tractor to clear errors. Only connect/disconnect with the tractor turned off.

[m_elias]

A description of JD’s TouchSet depth control. I believe this uses a 0.5-4.5V signal to control an absolute depth setting. I’m not sure yet what the Options pins should be set to for this to work vs the ±2.5V option.
http://salesmanual.deere.com/sales/salesmanual/en_NA/seeding/2012/feature/electrical/1830_1835/1830_touchset_depth_control.html

And a copy of the TouchSet portion of the manual.
touchset.pdf (295.6 KB)

[m_elias]

Today I tried to input an analog voltage with a potentiometer into pins C & D using the 5V ref and ground. This first picture shows the display before I detented the SCV control lever

This is what is shows after clicking the detent with the pot centered

And these last show show the indicator arrow moves up/down as I turn the pot.

If I turn the pot too high or low it goes back to displaying EC and then after clicking the detent again, it goes back to AC with the indicator arrow.

So from my limited experience/knowledge, it looks like it’s working except there is no output from the hydraulic remote port while I’m turning the pot back and forth. It does nothing when I press the retract/extend SET buttons.

[ChrisC]

If you are not getting output of the remote I would start with clearing all codes. It will still show that the valve is being controlled but nothing will happen. If you have done this make sure the tractor is moving while you are trying to control the valve. Deere has a safety built in that the remote will not output without a speed.

[m_elias]

Yes, the tractor needed to be moving, then it works!

[m_elias]

Because the Teensy (and Nano?) use 3.3v I2C lines and the voltages to control the tractor are 0.5-4.5 volts the MCP4725 DAC needs to be power with 5V which means its I2C lines also need to operate at 5V. For testing I used a bidirectional level shifter and ran on an isolated battery but I’ve ordered a few of these I2C signal isolators from DF Robot that also include a 5V to 5V isolated power supply so they should be perfect for this project.

[ChrisC]

I purposely ran a nano with 5V logic for this reason… also I can pull 5V from the machine to power the nano so when the machine fires up its not waiting on a signal from the computer which will cause errors… in the startup the nano tells the DAC to start at 2.5V or neutral.

I think I’ve updated the code to reflect this, but to be honest I’ve had my hands full with other projects.

[m_elias]

How much power can that 5v supply? Did you run just the Nano or also enc28j60 Ethernet shield?

[ChrisC]

I am unsure, but the intended use is to supply a potentiometer on the middle of a field cultivator, so I think it could at least supply enough to drive the both of them