Electronics – Henry York

FocusBracketer

Category: Electronics

| Year: 2023

Objectives

Automate the process of focus bracketing with a digital camera
- Focus bracketing is taking multiple photos of the same subject with different depths of focus
  - These can then be combined in software to create a single photo entirely in focus
- Some cameras have this feature built in, but mine does not
Require no permanent modifications to the camera and be easily removable

Focus Bracketing Example

Single photo; the background is out of focus

Digital combination of five photos taken with the FocusBracketer; the whole photo is in focus

Process

Designed bracket to attach servo motor to camera, and 3D printed it
Created wheel for servo to turn the camera lens
- Rubber grip is a length of audio cable glued to the wheel
Designed PCB in KiCad
- Includes OLED screen and four buttons for the user interface
- Has terminals to connect servo and camera shutter cables
- Controlled by Seeduino XIAO microcontroller, programmed with Arduino framework
  - Chose this board because it can be soldered directly to the PCB, which keeps the device low profile
  - Program allows user to set start point, end point, and number of steps
    - As start/end points are being set, the servo is jogged
Tested device by taking close-up photos of small objects

Reflection

The device generally works well
- Sometimes the servo does not travel to the right place after the endpoint is set
  - This could be because the wheel is slipping
  - Measuring the rotation of the camera lens and providing feedback to the microcontroller could fix this
- Is much more efficient than moving the lens manually, and results in more consistent images
The process was a good test of my PCB milling skills
- This was the largest PCB I had made in a while

Chain Puller

Categories: Electronics, Mechanics

| Year: 2022

Objectives

Integrate fluorescent light fixture into smart home system
Device should work consistently

Process

Tested pulling light chain with servo motor
- Added spring to give the device more pulling power
- Adjusted servo moving distance to pull the chain correctly
Modified lightbulb example from esp-homekit-sdk to control servo
- Runs on ESP-32 development board
Added light state sensor
- Compares two photoresistors to determine on/off state of fluorescent fixture
  - Two photoresistors allow the sensor to be accurate regardless of external light levels
- Interfaced sensor with esp-homekit-sdk to display state of light in smart home app

Conclusions

Successful project- is used daily
Fails to fully pull the chain occasionally
- Sensor allows this error to be noticed by the user so they can try again
- Adjusting servo travel distance may help with this issue, or using a stronger actuator
Chain gets disconnected from servo arm sometimes, but it can be reattached

One photoresistor faces the light, the other away

Bike Eye

Categories: Electronics, In Progress, Programming

| Year: 2022

Objectives

Detect cars behind cyclist and alert them audibly and visually
Provide a cheaper alternative to cycling radars like Garmin Varia™

Process

Tested an ultrasonic rangefinder, but its range was too limited
Decided to use an ESP32 camera board with a machine learning model to detect cars
- Programmed in C++ using ESP-IDF
- Code based off of TensorflowLite image classification and Espressif SD Card examples
- Initial version of firmware only collects photographs and saves to SD card
- Collected about 1100 images to train ML model
Case designed in Onshape, 3D printed in PLA
- Velcro used to attach electronics
- Powered by Li-ion battery

Future work

To complete this project, I will need to:

Add TensorflowLite model to firmware
Create alert system
- Buzzer, if loud enough, or display mounted to handlebars
Expand case
- I think a larger battery will be necessary
Road-test completed device and collect more photos for continued training

Initial ultrasonic rangefinder prototype

Internal electronics attached to case front piece

PCB Probes

Categories: Electronics, Mechanics

| Year: 2022

Objectives

Connect quickly and effectively to PCB traces
Be cheap and easy to make
Allow in-circuit reprogramming of microcontrollers

Process

Tested various designs for probes
- Decided on clothespin because it pushes down on board
Designed PCB tip in KiCad, milled on CNC machine
Designed socket to make swapping probe tips easy, and aligner to keep probe centered
- Socket and aligner 3D printed in PLA
- Socket, aligner and magnets superglued to clothespin
Clothespins magnetically attracted to base, an extra toaster tray
PCB secured to base with double-sided tape

Reflection

Probes were able to program an ATtiny chip in circuit on a PCB- it was a success
If the magnets were stronger, setup would be easier
This project was featured on hackaday.com
- https://hackaday.com/2022/02/27/need-to-probe-circuits-remember-about-clothespins/

RGB Handlebars

Categories: Electronics, Programming

| Year: 2022

Objectives

Make cyclist more visible to cars by adding lights on the sides of the bike
- Makes the shape of the bike more defined than if there were only lights on the front and back
Look cooler than a single color light
Have a long-lasting battery

Process

Initial design used an RGB pattern LED in a long tube
- Tube contains two AAA batteries to provide 3V to the LED
- LED diffuser sticks out from handlebars to be more visible
  - Latched pushbutton underneath turns the light on/off
- Electronics connected with thin magnet wire
Second design was more compact and customizable
- Includes nickel-sized PCB with light circuit
  - PCB milled at home on CNC machine
  - ATTINY 45 microcontroller runs an RGB LED
    - Microcontroller programmed in C++ without Arduino framework
    - Custom light patterns can be added
  - Pushbutton toggles light on/off and changes light pattern
- Powered by two coin cell batteries that together provide ~3V
- Case is 3D printed, with an unscrewable top for accessing the internal circuit

Reflection

The first prototype was very reliable
- Used for almost a year before the diffuser broke off
Second design was more fragile
- If bike is leaned against a wall, the pushbutton is crushed
Both designs are not bright enough to be seen during the day
- Both designs are clearly visible at night
- A higher power LED might be visible in the daytime, but would also draw more power
This project improved my skills significantly
- I got better at milling PCBs by adjusting my workflow and finding better cutting tools
- I created the Clothespin PCB Probes in order to program the PCB, and they have been useful for other projects

UV Curer

Category: Electronics

| Year: 2021

Objectives

Create a timer to control a UV light curing system for resin 3D prints

Process

Circuit designed in KiCad
- A monostable timer design based on a 555 chip
- Timer is connected to a MOSFET to control UV LED strip
Design milled into single-sided copper clad board with an engraving bit
Through-hole and surface mount components soldered
Potentiometer, power supply, and curing enclosure connected
- The potentiometer sets the relative duration of the timer, and the button is pressed to begin the cycle
- When the timer runs out, the lights shut off
- Curing enclosure is a strip of near-UV LEDs inside of a paint can

Reflection

The timer circuit is perfect for my needs – I no longer overcure resin prints
Combining the electronics into a case would make system look cleaner