Archive for February 20th, 2013

Anonymous Breakout With HB-415 Stepper Driver: Mismatch

Turns out that the anonymous parallel port breakout board isn’t compatible with an optoisolated stepper driver: each output has a 1 kΩ series resistor that limits the current well below the driver optocoupler’s expectations. The driver has an internal 300 Ω resistor on each input, too, which doesn’t help in this situation.

A detailed look at the resistors lined up in front of the connectors:

Anonymous parallel breakout board - series resistors

Anonymous parallel breakout board – series resistors

The breakout board would work fine with non-isolated drivers, like the Pololu breakout boards, so it’s not really at fault. The fact that there’s no doc anywhere to be found means you (well, I) couldn’t discover this without buying it first, but … I suppose it’ll come in handy for something.

One could short across the resistors, but I intended to use this board for the initial bringup and all that soldering defeats the purpose.