PCB Circuit Fabrication With the Othermill

Feb 13, 2018 20:44 · 402 words · 2 minutes read Hardware Fabrication

For this homework assignment for Homemade Hardware, we were to fabricate a PCB Board using the Othermill.

I continued with the previous design of an ATTiny85 controlling the brightness of an LED based on the reading from an HC-sr04 Ultrasonic Distance Sensor. I modified it slightly based on the instructions from class. A 1k resistor connect the reset pin of the ATTiny85 to the power, and the output LED pin would be connected via a TIP120 Transistor to the ground line of the LEDs. I also added a debugging LED.

Testing out the Circuit

First I breadboarded circuit with the modifications mentioned above:

Then I tested it out:

Designing and the Boards

Then it was time to desing the circuit in EagleCad.

The schema for the board with the sensor

For the board, I made sure that the ground pin for the sensor was on the left side; This would ensure that when the HC-SR04 was placed on the board, it would be oriented to be protuding off of the board and not overlapping it, enabling the parts below to be accessible:

The design for the board with the sensor; 4 pins were made available for the HC-SR04 ultrasonic distance sensor and oriented so that the sensor would not overlap onto the board.

We were also to create a circuit for a letter with LEDs that would have its brightness be controlled by the reading from the sensor. I was assigned the letter T.

The design for a letter T made of leds. The red route indicates where a wire would need to be attached

Fabricating the Boards

Now it was time to fabricate the circuit using the Othermill. In bantamTools, I managed to fit both boards onto the bed by rotating the T slightly.

For the bits, I set bantamTools to use 132” and 116” flat end mill bits. Then I watched in awe as the Othermill effortlessly and accurately milled the board:

Assembling the Boards

Then it was time to put the components onto the boards and solder them.

With the power connected via jumpers. The debugging light showed it was being powered correctly
Testing the output of the sensor with a basic LED light before putting together the letter T board

Assembling the letter board
The assembled boards.

And finally, testing that the sensor board can control the brightness of the leds on the letter board:

The assembled boards.