One of the AC Training Lab summer students has been working to modify the Digital Pipette (video description) to address a few issues related to the electronics.
Two separate power supplies were required in the original design (6V for the linear actuator and 5V for the microcontroller). This has been modified to use a step-up voltage regulator and a shunt regulator to avoid voltage spikes from the actuator that might damage the microcontroller. This appears to be working without issue, and using a 5V 1A power supply.
Thank you for your initiative to improve the digital pipette! Here are my thoughts on your post.
In general, it is not recommended to use a step-up voltage regulator for a power supply of actuators. Actuators typically require high current, especially at the starting phase, and the regulators may be unable to provide enough current. The actuator should be directly connected to the power supply for stability. However, the actuator for the digital pipette is small, so it might not be a big problem for now.
Because of the above reason, I would generate 5V from 6V if I had to use only one power supply. Also, 6V is easy to generate using 4 batteries. When I tested last time, generating 5V from 6V provided by 4 AAA batteries using a regulator seemed to work, but I haven’t thoroughly tested the stability.
If you prefer to use 5V, the actuator should work with 5V at a slower speed. According to the FAQ (“Can I slow my actuator down?” Frequently Asked Questions | Actuonix Motion Devices), 6V is just the maximum allowed. In this case, you may need to use something to protect the controller from the noise caused by the actuator.
I previously developed a wireless version using ESP8266 Wi-Fi module (x.com) and the source code is already public (GitHub - ac-rad/digital-pipette at wireless). The summer student may be interested in this direction.
Good point about step-down vs. step-up. 6V to 5V, and the 5V to the MCU separated by the shunt regulator seem like good options.
Thanks for the link to the FAQ. This addressed some related questions from elsewhere. In particular, the L16-P with external LAC board would make it possible to carefully control the speed of the actuator and do synchronization.
A software workaround is to run a timed while loop that progressively increases the duty cycle, but this would likely be more fragile and limited than the above option.
Hello, I am the high school student currently working on this project and I wanted to provide a update to the progress of the digital pipette. I am currently still using the Step-up voltage regulator as it currently does not appear that the decrease in current has a major impact on the pipette. However, if I find that there are major issues with this method I plan to generate 5V from 6V as mentioned by Mr. Naruki. I am currently working on integrating the digital pipette with the Science Jubilee. I have made a second version of the case shown in the original post just to lower the Terminal PiCowbell ensuring it no longer sticks out. Additionally, I am designing the tool plate and tool wings for the pipette when it is attached to the Jubilee. Please let me know if you have any suggestions. Thank you for your time.
Hello, I wanted to provide an update on the progress of the digital pipette. As mentioned in the post-Dr. Baird shared, that the Jubilee adapter has been completed. In addition to this, I have been working on allowing the motors in the Digital pipette to work effectively with the motors in the Jubilee. I am doing this by synchronizing the times of the controllers of the different motors through MQTT. With this message I will attach a short video demonstrating this time synchronizing with a Servo Motor and the digital pipette. With this the digital pipette can work in sync with other devices such as the motors of a Science Jubilee.
Hello, I apologize for the delay. Here is the bill of materials for the digital pipette. As I no longer have access the pipette the measurements for the screws and bolts may be off but I have tried to ensure that they match with the measurements on my case design. I will attach a link to the document below please let me know if you have any questions or concerns.
