by joo, published
- Laser cutter or 3D printer
- 1 Arduino
- 3 servos
- 1 dry wipe pen
- M3 nuts, bolts, thread tap
Update to V1.01:
added calibration routine and documentation to arduino code
see the instruction tab above for building instructions
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i actually don't know the exact reason, but i think it had to do with the circles not closing because of the play in the hinges... it also could be that the functions are a bit off and faulty
Once again, thank you for the help. I did do the intial calibration and it did draw the time, however it was upside down. Will this give me the figure eight on the x-axis? Why are the start and finish points slightly different? So your going 269 degrees and finishing at -91 degrees?
number(30, 35, 8, 1);
drawTo(bx + 5 * scale, by + 10 * scale);
bogenUZS(bx * scale, by * scale, 10 * scale,4.7,-1.6, 1);
bogenGZS(bx + 20 * scale, by * scale, 10 * scale, -4.7, 2, 1);
angle is in radians, have you used the v1.01 with calibration routine? also if your servos are inverted there is a discussion down the comments about it, a quick fix seems to be the following:
writeMicroseconds(floor(((a2 + a1 - M_PI) * SERVOFAKTOR) + SERVOLEFTNULL));
writeMicroseconds(floor(((a1 - a2) * SERVOFAKTOR) + SERVORIGHTNULL));
writeMicroseconds(3000-floor(((a2 + a1 - M_PI) * SERVOFAKTOR) + SERVOLEFTNULL));
writeMicroseconds(3000-floor(((a1 - a2) * SERVOFAKTOR) + SERVORIGHTNULL));
to reverse the servos
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- Arduino uno
- Tower Pro 9g servos (those cheap ones from ebay)
- WB SL DRYWIPE MARKER, bullet tip
- A small custom servo adapter, there are shields or servo-arduinos that also can be used. You can also just use jumper wires: 5V to red servo wire, GND to brown or black servo wire and the arduino servopins connected to the yellow or orange servo wire
(for version 1.01!)
1. Lasercut plotclock_beta1.pdf from 3mm material or 3D print plotclock_SUP7.skp
- the black areas in the pdf on the servo arms should be used to engrave some material away, so the servohorns settle in
- use thingiverse.com/thing:250204 for single STL files if you 3D print the clock (Thanks corben33!)
2. 3D print swee.stl or reuse some other cylindrical part for the sweeper
3. Tap 2.5mm holes with M3 thread
4. Assemble arms with M3 screws, gently adjust the counternuts so that the joints under the screw heads just have enough play for smooth movement (see joint picture).
5. load Arduino sketch plotclock_V1, see code comments for further information
- playground.arduino.cc/Code/time library is needed
6. Add some sort of cloth with double sided tape to sweeper
7. Attach servos to digital pin 2, 3 and 4, according to arduino sketch, test them without anything attached by plugging in the arduino (the photos show it being connected to 1, 2 and 3, which isn't optimal since 1 is also the TX pin, so during arduino startup the lifting servo jumps around)
8. Put everything together
- You may have to redrill the holes that are used for securing the servos, since some servo screws are a tight fit.
Acrylic is brittle and easily breaks wen the mounting holes are to small. Only push the servo arms onto their hubs, don't secure them with screws! For initial calibration do not mount the resting clip for the wiper (danger of collision with the pen). Glue or screw the servo arms to the acrylic parts.
9. When attaching the servo arms, make sure they can turn enough to reach every point on the drawing surface by manually turning them
10. Power the arduino, it should start a calibration cycle where every second the position of both servos changes by rotating exactly 90 degrees (see last image in gallery)
11. Change the SERVOFAKTOR, SERVOLEFTNULL and SERVORIGHTNULL values until everything matches up (see code for more information)
12. Attach the pen and the sweeper holder only after testing everything else
This description is still a bit of a WIP, so comment if you have any questions!
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