Now that I have the
running the steppers, I'd like to have it turn the laser on and off too. Normally, the
Egg-Bot this board
was designed for has a servo to raise and lower the pen. This is controlled with a pulse width modulation (PWM) output. But I needed
an on/off signal to feed to the laser. Looking at the documentation,
I noticed references to a solenoid output, which sounded like just what I needed.
Looking at the earlier versions, I could see the circuitry to drive the solenoid,
but that circuitry isn't present on the board I have.
Looking at the schematics, the I/O pin that drives it is now used for another purpose.
I downloaded the firmware source code and tried to dope out what the current code did,
but I wasn't able to figure it out.
So I sent a note to the designer and asked him about it.
He sent back a prompt and helpful reply, stating that the RB4 output should have the solenoid signal.
I soldered a header on the appropriate pins and hooked up an LED (and current limiting resistor). At first, I had the LED hooked from +5V to RB4,
but that voltage isn't supplied by the board when it's running from just USB, so no joy. So I hooked the
LED between RB4 and ground, and sure enough, it followed the pen up/pen down state.
( Sweet!Collapse )
Originally posted at Dreamwidth.org comments