Mr.What


About Mr.What

Electrical Engineer, working in Software Engineering for 20+ years. Wants to do more low level hardware and embedded work. Also interested in metal work.


Laser cut enclosure for RAMPS1.4 board

Here is my drawing for a box to enclose a RAMPS1.4 stepper motor control board. If you don’t have any RAMPS1.4 boards… I guess you won’t be interested. You can cut these at Quelab from 3mm acrylic. Cut one copy as is, another copy without the little access holes for the opposing plates. It is easy to delete items in LaserCut, harder to add them.

You will need to add holes for fans, ventilation and cable routing.


Delta 3d-printer calibration procedure

After making it part way through the dreaded calibration procedure for a delta 3D printer, it does not seem that bad. I tried to write a quick overview that may be helpful to some.

I am not done yet, but I am within +-1mm of flat. I hope that the autocalibration procedure will take care of the rest. I think that the residual error is from loose tolerance on my mechanical build. The solution would be to check the squareness of the frame, and re-print the diagonal bar carriages to be exactly the same. Mine were printed at different times with minor design changes, and don’t perfectly match.

Centering the extruder tip on the print bed is a matter of position of the endstop switches. This is very hard to correct with sub-mm accuracy. I may add a fine-adjustment screw to the carriages for these small adjustments.


ACE 2014

I have gotten busy, and not heard much from ACE. I don’t have tickets yet (guess I’ll get them at the door). I don’t know if I could bring the Dalek if I wanted to, without permission as an Exhibitor.

Quelab Red-Green-style Dalek confronts cut out of the Queen.

It has a blown transistor, which I have not fixed yet. I could just replace the transistor, but I’d like to try to improve the drive circuit to make this failure less likely to happen. I haven’t gotten around to it.

If anybody is interested in a last minute push for ACE, I can arrange to go over to Quelab in the evenings to try and get this done. I need to repair the drive, and perhaps work a little more on the aesthetics.

A local cosplayer is doing a push to have a lot of superheros in tutu’s. If you have or could make a tutu for the dalek, that would be awesome. A tutu might give me extra motivation to at least repair the current drive circuit.


Laser engraving wood


There are some tricky aspects to working in wood. Since it is not totally flat, cut the stock just large enough for your piece, then stabilize with magnets. It can move with the engraving motion/vibration. Masking tape would have helped with burn marks/smears, but they can be removed to the desired degree with light sanding. I wanted to leave a little bit of the burn scars, I think they look neat.


Arduino Pin-Change Interrupts for Sonar

I had a very hard time figuring out how to use Pin-Change Interrupts. I found AVR documentation hard to follow, and Arduino libraries overly complicated and obfuscating. Here is an example of how to use pin-change interrupts for Arduino (mega). It may help.

Pin-Change Interrupt forum post

Bottom line:


PCICR |= 1; // enable PCI0 pin group interrupt
PCMSK0 |= 0b1100; // enable PC interrupts on arduino pins 50,51, which are in group PCI0
...
/// Pin-Change interrupt, for group PCI0 (arduino mega pins 13..10, and 50..53)
ISR(PCINT0_vect) {
// do what you need to do when one of the pins in this group changes.
// usually... check to see which pin changed here... then do something.
}