Last year a good client of ours acquired a "slightly modified" Terex 5022 telescopic handler, in which the original Danfoss electronic control unit was replaced with an ingenious system of cables and makeshift levers that were connected directly to a 5 section PGV32 directional valve.
There were three levers to your right, two to you left - rugged looking, but almost impossible to work with - and when the new owner tipped the handler over when he accidentally activated turret rotation with his elbow while loading a large and heavy container, he decided to invest in a "proper" joystick control and asked for our help, at which point yours truly came into the picture with an "economic" quote and promises that "our custom built system is the best handler controlling system in the world!"
The build itself, especially the control board, was a lot of fun, and I will definitely give it a detailed description in a future post, but today I want to expose, or better - begin exposing - a very peculiar, in my opinion, problem, which I wasn't expecting to run into.
Connecting a PVG32 valve to a joystick or a rheostat control is something I had done many times before, and I thought that my experience would be more than enough to take on a project like this.
For this particular build I ordered a Danfoss JS1-H heavy duty joystick with a PR2 grip version. Just like the original system, it had three proportional controls (the two axis plus the thumb roller) and three buttons to control additional functions. Nothing fancy or over-complicated.
The control board contained a combination of a toggle circuit, a binary logic IC and several solid state relays to direct signals and power - once again, a simple, albeit rather "custom" solution.
Before installing the system on the Terex, I, naturally, tested everything in the shop, and everything worked absolutely fine.
Pretty content with myself I began the installation. I ripped out the cables and levers (with certain amount of satisfaction), replaced the original wiring, slapped the new control board behind the operator's seat, hooked up the 25 pin SUB-D connector to the joystick and ran the system with the joystick sitting in my lap...
As expected, the system worked flawlessly "at the first push of a button"!
Pleased with the way my custom solution behaved - I turned to the "polishing stage", during which you normally take care of stuff like cable management, zip tie trimming, mechanical supports, reinstalling lids and covers and what not.
With the owner's blessing I used one of the "old" lever supports to secure the joystick - I cut out the mounting holes in a 3 mm steel sheet, welded it to the top of the support frame, ground the sharp corners, and painted it over with a black spray. An hour of work and such a beauty to behold!
Now picture the following - the cables are tight and tidy, the joystick's in its due place and boy does it look good, the so very professionally looking control box is fixed and closed, even the cabin floor has been cleaned. "Pretty as a picture", as Groundskeeper Willie would say! I start the engine, move the joystick and - nothing works! Zilch, nada, not even a single on/off button. Do you know the cartoon failure sound, the tuba one? That's the sound that played in my mind at that moment.
Saying that I was devastated would be an understatement. Did I connect something wrong? Have I made a mistake designing the PCB? Did I just burn a brand new one thousand euro joystick with my contraption? These and a thousand more thoughts rushed through my head at that moment. I am so-o-o screwed right now!!!
Well - what do you do in a situation like this? - You don't panic, you verify everything . Which I did. To no avail. Half an hour later the only thing that I had connected was the god damned joystick's power and ground connections - and the stupid thing still wouldn't work! For as much as I didn't want to believe it, it appeared that the brand new Danfoss joystick had just died on me, and the worst part of it was the fact that I wasn't sure if it simply died or if it was my "invention" that killed it.
You know what happened next? - I found and solved the problem. Quickly and painlessly. And, knowing what I know know, I would be able to tell you what the problem is just by looking at the pictures or reading this post.
I contacted Danfoss and described what I found, but, unfortunately, so far I haven't received an answer from them. I'll keep waiting...
I am expecting to get another JS1-H joystick soon, and I will run some tests on it to see if it behaves the same way as this one.
And for now - I will keep the "suspense" till the next weekend, when I will tell you what exactly what it was that I discovered and how I solved the problem.
In any case - if any of you recognize or have thoughts about the problem with this installation - please, send me an email - because right now I am trying to define if the "thing" that I found is "normal" for these joysticks or if I simply got a "lemon" from Danfoss.