John Deere remote SCV control

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

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?

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

He first mentions the electronic control method here.

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

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.

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.

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

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.

The tractor needs to be driving/moving to activate the hyd valve

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.

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

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.

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.

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

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

Did you end up doing anything further with this @m_elias ?

Can you correct me if I’m wrong about the functionality? With the board/pot plugged in:

  • You can still manually actuate the SCV fingertip control.
  • You can still click the SCV fingertip control and use the timers and flow controls.
  • With the finger tip control in the “forward and down” position you allow remote control by the pot/board.
  • So with a board/pot plugged in; you retain all the normal functionality except for float, you lose float.

I’m thinking about making a small board to interface with the connector for hydraulic up/down control of implement.

The diagrams read “SCV 1 only” and SCV 3 only." I assume that if you connect both analog lines you can have control of both SCV 1 and SCV 3 simultaneously?

The touchset control manual seems like different functionality than the scraper control. Do you think implement with touchset control use different GHJ jumper?

The current PGNs don’t have any actuator speed information, so the flow rate would have to be hard coded or maybe adjustable with a potentiometer on the board or some buttons or something. Any input on that?

I don’t see a convenient way to switch between plugged/unplugged (other than plugging/unplugging) implemented in such a way that you won’t throw codes. Sometimes you’re going to get someone in the cab that doesn’t want to use auto function and just wants to be able to put an SCV in float. Any ideas? Do you think pins GHJ (jumper pins) could just be connected to a microcontroller? Allow the microcontroller to read a mode pin (connected to switch) upon powerup and then set pins GHJ to either FLOAT or HIGH/LOW? Think that would be fast enough to prevent the tractor from throwing a code? How do you reset the tractor once it has set a code?

I think you lose the “continuous flow”

It has been a long time since I was in a JD tractor but I think “forward and down” is the continuous function, float is one detent further.

This is correct.

It’s been a while.

I want to check our TouchSet harness eventually to see what’s different in it but there we only use one height potentiometer on a cultivator to set up & down height whereas the pictures I showed of the EC & AC on the display is in a mode for controlling flow on the remote hyd.

Thanks for the answers! Just to clarify because I’m still not confused, do you lose float or do you lose continuous flow (timer)?

It’s the down/forward continuous/timer option that you lose. I’m not sure what happens to the up/backward though. The simplest for connecting/disconnecting to to shut down the tractor but you could get fancy with a man-in-the-middle microcontroller.

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I’m just looking though my notes to familiarize myself again with the JD remote control system. Were all your questions answered?

When using the remote flow control option as the diagrams from Chris show (Auto Control mode on scv 1 & 3) you lose the ability to use the down detent (continuous or timer) but I suspect the up detent (continuous or timer) still works (imagine a scraping scenario) but you can still manually control both up and down. It’s not the float position that activates AC mode but rather the down/forward detent.

In P mode as described in the Touch Set manual section, then only scv 1 is used in an absolute height mode where the valve outputs oil to bring the analog input voltage from the remote pot to the set point (ie raise or lower cultivator)

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Thanks Matthew, all my questions were answered.

Hey im looking to put together open grade for a John Deere 8120 and the tractor has a connector inside. Is that the same one youre talking about to add the wires diectly to the scv? Or is it the one outside the tractor

On the 8x00 and 8x10 series the touch set harness is under the rear cover with the SMV sticker. I’m not sure how the 20 series is.