haberlandt2008

The system is built to mantain the pH of the tank solution stable by droping acid or base depending on the measurements of the pHmeter. An Arduino controlled servo motor (90º rotation) is tied to a hospital valve to open and close the duct.

We’re testing the lapse between drops and the volume of each drop to see how the system responds and how we will adjust it to our needs.

Every time a drop is delivered it leaves the next one about to fall  due to the tube’s surface tension, making the system very reliable in short time releases. In my room conditions, the hanging drop starts evaporating, making the next drop to stall.

These are the results right before and after a drop release:

1h>drop falls

(pending)12h- drop falls

24h- drop doesn’t fall

48h- drop doesn’t fall

Conclusion
After a few hours without releasing a drop we are going to program it to release a double volume of liquid to push out the single drop we need.
This results could change once the tank is sealed due to increases in relative humidity inside the bioreactor.

Stirrer test1 from blablabLAB on Vimeo.

We built this using components of an old computer. One of the fans attached to the computer tower and 2 strong magnets (rear earth magnets) found inside of a hard disk drive (the older they are the bigger/stronger the magnets). All this was  glued together with the useful and reusable blu-tack. Inside there’s a pro sitrrer bar (thanks Nuria;) made of a weak magnet recovered with nylon. All controlled with a potentiometer into an Arduino board.

Problems:

Spins to fast to let the algae grow properly due to shear stress, the appropriate speed would be  around 3 cycles/second.

The speed control of the potentiometer is unstable,  speed increases and decreases quite randomly. There’s a critical point that makes the fan to stop spinning when you try to slow it down,  so we have no range in between, it’s still or to fast. Speed can make the inside bar get loose if  it’s not perfectly aligned (not easy) with the magnets below.

Potentiometer at max power, 2 different speeds.

We are rejecting this option for a more stable one. Coming soon attempt 2 with a geared dc motor.