Takachar CO-OP

July 2023 - August 2023

During my four month co-op term at UBC HATCH, I had the opportunity to work with Takachar for two months (the other two were spent at Verdi). At the end of growing seasons, fields are often burned to remove remaining biomass such as twigs, straw, etc. This releases greenhouse gasses and other emissions into the atmosphere. Takachar is a startup aiming to recycle biomass into biochar which then can be reused in fertilizer, charcoal filters, and other products.

At Takachar, I primarily worked on creating a backup manual fan speed controller (more information below). Other tasks involved helping with lab experiments, performing “hot tests” on the UBC reactor, and collaborating with others to design and 3D-model upgrades to Takachar’s new reactors using SolidWorks. 

Manual Fan Speed Controller

The fan controller had to provide two different 25 kHz PWM signals to independently control two sets of fan speeds. Each set has two fans, making four total fans being controlled. The RPM is to be inputted from two mechanical dials for ease of use. I began by researching and considering different options, I chose to avoid using any microcontroller for simplicity. Instead, the PWM signal is generated by a 555-timer operating in astable mode, and the frequency is controlled by selecting resistance and capacitance values. A circuit simulation was created in LTspice to select the correct resistance and capacitance values to provide a ~25 kHz PWM signal. 

Next a prototype was assembled on a breadboard and functionality was verified with the fans. An initial issue was that fans were not reaching their full RPM. A possible cause would be due to the PWM signal, so an oscilloscope was used to verify the frequency and duty cycle of the PWM signal. However, the PWM signal was operating as intended. Next, I looked through the datasheet and found that the fans should operate at full speed when no PWM signal is supplied. So, the PWM signal was removed but the full speed was still not being met. This led to the last possible cause which would be the power supply. Alligator clips were used to connect the fan to the power supply, but after removing the alligator clips and using a direct connection with wire nuts the issue was resolved. 

After determining the prototype works, a PCB was designed in Altium to create a more secure, clean, and permanent solution. An off the shelf enclosure was selected, and a CAD model was constructed in SolidWorks to verify the PCB, cable glands, switch, and potentiometers fit. After creating a bill of materials (BOM), orders were placed for all the components and cabling. I hand soldered all components on the PCB, and crimped pins for the fan connectors. Using a drill press, holes were drilled in the off the shelf enclosure to facilitate the cables glands, power switch, and potentiometers. Printed templates combined with a center punch were used to locate the hole locations. 

When the time came to finally test the final controller, the fan speed was not being controlled smoothly. The fan speed would randomly jump high or low, and performance was inconsistent. This issue had me stumped for a while because everything was working in the prototype, and while troubleshooting with a multimeter and oscilloscope, nothing seemed out of the ordinary besides the inconsistent speed control. I checked all the connections on the PCB, checked the crimped cables, tried different power supplies, and soldered a new PCB from scratch. Finally, I narrowed the issue down to the long power extension cable for my controller. The power extension cable going into the controller was about 15 ft long, and during prototyping was not used as it was not ordered yet. This long 12 AWG cable caused noise in the power input to the PCB, and led to sporadic results with the 555-timer. This issue was resolved by simply adding a bypass capacitor to the PCB’s power input.

Technical Skills Applied:

• PCB design and layout using Altium

• CAD using SolidWorks

• Troubleshooting circuit issues using multimeter and oscilloscope

• Simulating circuit using LTspice

• Generating PWM signals using 555-timer

• Soldering

• Crimping pins on cables

• Rapid prototyping

• Designing for manufacturability and useability

• High current considerations 

• Conducting lab experiments 

• Documentation

Non-Technical Skills Applied:

• Collaborating with colleagues to run experiments, troubleshoot issues, and design new upgrades in SolidWorks

• Self-regulating and time management 

• Quickly adapting to arising challenges 

• Communicating updates and progress to remote team members

• Communicating with overseas team members