MadModder

Thanks, I was beginning to think I was just talking to myself again.  But since I'm the only one in the house, I guess at least I'm always talking to the smartest person in the room?

Well I'm going to rush in and tread where.... um I'm impatient.... 

Okay so the first question is, are the opto-isolators going to be overdriven by the Arduino's outputs?

Let's say the Arduino is putting out 5V -- the 817 optoisolator can handle anywhere from about 5ma to 50 ma.

So I could hook up a variable power supply to one of the step or direction pins and slowly crank up the voltage from zero and see what the current draw is as I go, not to exceed 50ma. If I reach 5v, then I should be good to go on the step and direction pins. those are inputs

The switch pins are outputs and those are TTL level. I'll have to figure that out later. Right now I just want to get the steppers moving.

Very cool, John!

A long time ago I made some electronic rudder pedals for my old computer running flight simulator. It was Just hinged plywood pedals and linked potentiometers on a wooden box base. The pedals were connected by braided line through a pulley attached to a short post in front of, and between the pedals.

It was not so different in mechanical components than the Heath Parasol replica I was building, which used aircraft cable and pulleys to the rudder. And the feel was the same.

OK, a couple of minor speed-bumps, but nothing that Ebay and a credit card can't handle.

Speed-bump #1 - Most of the drive shafts I've found have 5mm bores or 6.2mm bores. The WLToys axles have 5mm input shafts and the shafts with a 5mm bore are a better fit to the LD1201 transfer case. But the LD1201 has 4mm output shafts. No problem, I'll just cut a piece of 4x5mm tubing and glue that into one end of the drive shaft. "Cept that I ain't got no 4x5 tubing, I've got 3x4 and 3x5 - but no 4x5.

Speed-bump #2 - Drive shaft lengths. I can't really find the drive shaft lengths I need. My last revision of the 3D model for the suspension/chassis put all the axle spacing's in their correct positions for the upcoming cement mixer conversion. I also centered the gearbox so that the front and rear drive shafts can be interchangeable. This leaves me with a nominal drive shaft length of 46-ish mm. Since the transfer case output shafts are 2 different lengths, 6mm and 7mm, I'm using the 7mm length to determine the minimum and maximum drive shaft lengths. I need to collapse my 46mm nominal drive shaft about 7mm in order to be able to remove the drive shaft - without needing to remove other bits of the truck anyway. I also need to allow for suspension droop, which won't be much since this is a cement mixer - not a rock crawler. But I need to allow for some, so I'll use 7mm there too. Bottom line - I need the front and rear drive shafts to be from 39-53-ish mm in length. It can be more than 53mm, but no less. The drive shaft from the center axle to the rear axle is worse, it needs to be from 33-44mm in length. These are the drive shafts that I like the best.  https://www.ebay.com/itm/375169557748

But....The shortest length is 60-77mm, I've got 3 of them on order. On the plus side, they use an internal/external spline for the extension instead if a square drive or a pin in slot setup. The external splines are full length, they are easier to cut so that makes sense. The internal splines are not easy to do at this size. That difficulty goes up as the spline length increases, there's not that much room in the hole to begin with and the chips HAVE to go somewhere. My guess is that the splines are only a few mm in length, the rest of the hole will be counter-bored to the major diameter of the splines - if not larger. My current plan is to cut a big enough chunk out of the middle of the female half that the length of the stack-up equals my minimum drive shaft length. I've got some 3/8" OD aluminum tubing that I'll use as a reinforcing sleeve and glue the cut parts into it. Then I cut the male splines off just enough to allow the drive shaft to fully collapse. And Bob's you uncle - I hope. It worked for the axle shafts, should work here too. We'll find out. I also ordered 2 of these. https://www.ebay.com/itm/314228515981 To see if I can cut them shorter than the others for the center to rear axle shaft.

If I get REALLY lucky, and the internal splines go full depth, then all I have to do is cut things to length. (And if you believe that's gonna happen... Well, I got some bottom land in Florida I'll sell you - it's REAL close to the river.)

Don

 Are the arduios 3v  or 5v ?  Are the optoisolators compatible with the  Arduino I/O?