So I'm working on a project that uses a HiLetGo L293D motorshield and I need to insert some very thin 22AWG multicore wires into the motor (M1 ~ M4) connections of the terminal blocks -- but because of the excessively strong spring loading on the 'quickfit' metal plate that grips the wire, it's a very tricky process. After I back off the locking screw, I can insert thicker, single core wires without too much trouble, but these thin wires are almost impossible. Best I could do was sort of hook them in there with a tiny screwdriver that forces the spring-loaded plate out of the way, but it's a very unsatisfactory, hit and miss process (mostly miss; they tend to crumple and just fall right out again).
Does anyone have any tips on how to do this properly?
(I've found that I can stiffen the wires some by applying solder to the ends of the wires, but it only helps a little. This video https://www.youtube.com/watch?v=2amguZlxZNc also shows some kind of stiff tip/sleeve that seems to attach to the end of the wire, and that looks like something that would solve the problem, but I don't even know what these things are called so any pointers here would also be very welcome!)
They look like regular screw terminals, yes, but they're actually screw terminals plus an internal spring-loaded plate. TBH I don't see any upside at all to this design. It's basically the worst of both worlds because even if you're using wires that are stout enough to push past the jaws of the plate, you still have to mess with the screw anyway, backing it off to release some of the tension on the plate to begin with and then tightening it up again afterwards.
Perhaps I should also add that there seems to be a limit on how far you can back off the screw. So I haven't dared try to back the screw all the way out because there's some kind of stop -- it feels like plastic, not metal -- that prevents this, and if I were to force it and actually get the screw all the way out, then I suspect this might permanently deform the plastic housing and it might not go back together again.
Your spring loaded plate actually prevents the tip of the screw from crushing and severing the wire it's clamping down on. Usually, if it's never been tightened, there's a gap between the plate and the bottom of the clamp, into which you can insert a wire, then tighten the screw. If it's been tightened without anything in the clamp, then the plate deforms to follow the shape of the bottom of the clamp, and you get the obstruction issue you're facing.
Interesting! The motorshield arrived from Amazon with all of the terminal block screws already tightened -- to quite high torque too, some of them -- so maybe that's what happened?
( A passive or lightly spring-loaded plate to prevent the screw from crushing and severing the wire is of course a good idea. But the spring-loaded obstruction and/or pressure I'm dealing with here is in a range that goes way beyond anything that might be helpful. Perhaps I've just got a board from a bad, overtightened batch?)
Perhaps. Or, just a lousy design. Followed the general way other manufacturers do it, didn't understand the underlying requirements. Who knows why China does what China does? Always a mystery.
