Friday, December 22, 2006


Z-axis enabled on the controller board...

I tried installing a second 754410 dual darlington chip to power the z-axis gearmotor. What a mess!

First, I installed a 754410 for the z-axis and the Mk II (circled in red) to the left of the one driving the x and y axes (circled in blue). Trying to be neat I managed to miswire the new chip to the point of creating a short within the chip.

I started to dig it out of the board (you can see the cut pins on the right side of the chip) and then realised that I had some spare space on the board. I put a third 754410 (circled in yellow) in and did a quick lashup of the wiring which is very easy to see. You can also see the two terminal connector that runs the z-axis (circled in yellow as well) That mare's nest worked first time out. There's a lesson in there somewhere, I expect.

I tested out the wiring with the {HZ+} and {CZ+} commands and it worked perfectly.

The limits detector went together fairly smoothly and the firmware for managing the x and y axes checks out for the z-axis as well. The {RZ} command now works.

Now I have to wire up another shaft encoder and the z-axis will be good to go.

I've taken to socketing all my chips... not only for reusing them when i scrap the board, but so I don't fry the chip soldering it, and so I don't ruin the board when one of the chips decides to go bad!

It adds to the cost, but with the trouble I had adding the 2nd & 3rd axis to my board, it was well worth it...
Yeah, I think you are being very wise to do that. For my own part, however, I hesitate to do it with dual darlingtons, though, because of the amount of current you wind up trying to move through a friction connection.
Some old electronics I've seen have chips on a little stamp sized piece of perfboard, it floats somewhere above/near the main board and sends short wires down to it. Looks messy, but seems to be good for troubleshooting and replacing dead chips.

I've copied that trick on my latest soldering adventure, not such a crazy idea. ;)
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