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The open source phone by Dooba, called "Trill" is awesome. Open source PCB with a 3D printed enclosure. Beautiful little OLED display. Making a cellphone has been my objective for about a year - I even have most of the parts already. Sadly I haven't had the time to sit down and really work on it. But my cellphone is on it's last leg (And I've had it since 2012 - so it can be considered archaic at this point). I really don't want to buy another phone - so Trill is on my wishlist.

A look at the spindle slipping due to low contact friction with the holder, Z axis probing to prevent warpage, and counterweight springs to give a favorable failure mode for the spindle.

Z axis springs used to cancel the force of the spindle's weight
Z axis springs used to cancel the force of the spindle's weight

The demands of graduate school were taking their toll last month and I wasn't able to give OCI the love it deserves. But I'm back to work now! The Z axis was not getting enough current from the stepper driver on the ramps board. This is because the entire spindle assembly weighs 1kg - and is straining out the stepper motors. When moving in small increments, the motors will skip steps and move inconsistently (see data from Circuit Mill Development Log: Z Slip). Often times the spindle would slip downward while cutting, causing some catastrophic results.

Test geometric patterns and test designs milled with reasonable success

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A simple circuit board that fits in a RAMPS motor driver slot. It breaks out the Step, Direction, !Enable, and ground pins. These signals can now be used with larger high current stepper drivers.

Average: 5 (1 vote)

A +-5V power supply. The input is 12V (as a minimum, it can go up to 48V). Made to be used with this 12V power supply. The max current is 1A per supply. This supply works perfectly for amplifier circuits that deal with AC signals.

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A simple Radio Frequency Transmitter. The circuit includes a DC rejection capacitor, input low pas filter, and a resonant circuit for AM modulation. A tunable capacitor is used in order to generate a resonating carrier.
This design is made with reference to a design in Practical Electronics for Inventors, Third Edition

Average: 2 (1 vote)

This AC dimmer circuit utilizes a zero crossing detector and Triac. The output power can be controlled by adjusting a potentiometer value. The max current allowed is 10A (limited by the Triac).

This device can control the power delivered to any type of AC device, not just lamps. It can work on AC motors, heaters, power supplies,etc.

I've noticed that the circuit mill in development is having issues with small adjustments (0.3 mm). During small movements, the axis will do one of two things - it will either not move at all, or it will move too far. For example in the picture below, the left pattern was done keeping the Z axis at a steady height. The right pattern was done with the Z axis adjusting to keep the cut level. As you can see, the mill appears to be "slipping" over time, and the bit cuts further and further into the board.

No Z movement (left) vs Level compensation (right)

Here's a fun video showing all of the work that went in to prototyping, testing, and manufacturing television sets in the 1950's.

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This circuit is capable of generating a constant 13V from an input from a solar panel of 5V-17V (or more). There is also an extra 5V output for logic circuits (IE some sort of embedded control system). Design components and parameters were found using the Boost Converter - Component Calculator.


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