Flypi - cheap microscope/experimental setup

Optogenetic activation of Chrimson in Adult fruit fly

Zebrafish expressing green fluorescent protein in heart tissue

Calcium imaging in the Drosophila larva

Once we figured out the problem with the Peltier element, another problem came up, this was not a very important problem, but rather an annoying one. What happened was that when the Peltier reached the desired temperature and the arduino software went into "maintain temperature" mode it would send signals to turn the relays on and off really fast, making all four of them make a lot of clicking sounds (the magnetic switches), which was, of course, unpleasant. For this reason we substituted the relay configuration for an H-Bridge one. We are now developing a solution with a L298N H-bridge. Once it is up and properly running, we will update the BOM list, custom PCB design and Arduino sketches.

After a long development break, we managed to put more time into the project and solved (or at least seems we did) the issue with the Peltier element not behaving as expected. Turns out we were too shy with our power supply and the element needed more juice to run properly.

Using a 10V 2A power supply together with a 38X38X20mm heat dissipater and a 40X40X10mm 12V fan we were able to make it maintain 15°C on the top surface for 10 minutes (and still very stable) in a room at 28°C. The same configuration allows us to heat up the same surface to 35°C. Both temperatures (15 and 35°C) are the extreme values used for the experiments we want to conduct with this device.

This project log is to state what is our "state of the art" for the Flypi:

The system is composed of different modules (below) that can be independently used/mounted depending on the user's needs.

The modules are:

Raspberry pi and arduino with the respective python code and uploaded arduino code - these are the heart of the system. The python code is a GUI that controls the pi-camera (on/off, snapshots, movie recording), sends and listens to commands from the serial port where the arduino is connected. The arduino code does the same on the serial communication side and interacts with the sensors and other electronic bits. (The python GUI still uses some global variables and is in a very scripty format. In the future we would like to turn it more pythonic)

Pi-Camera with lens - The camera allows for complete record of experiments/test runs. So far it can do time-lapse, take snap shots, digital zoom, video recording. Also has a preview mode.

Peltier element, temperature sensor and RGB LED - the peltier uses a independent power supply (we are still working on finding the optimal/cheap/reliable one) and it's circuit is composed of 4 relays, so that we can alternate the direction of current in the peltier, in order to heat or cool the top surface according to our needs. The temperature sensor is placed on top of the peltier and clamped down with a 3D printed part. The reads from the temperature sensor are sent to the python GUI which can be used to start heating up/cooling down the peltier to a desired temperature. The RGB LED is used to indicate visually when the peltier is heating (red), cooling (blue) or at the desired temperature (green)

LED ring (12 LEDS from Adafruit) - Can be used to do optogenetic stimulation, fluorescence activation and to generate light patterns (RGB colours, rotating clockwise/anti-clockwise), as a light source for microscopy mode. Has an extra power supply

LED Matrix (8X8 blue leds adafruit with backpack) - Can also be used for optogenetic stimulation and different light stimulation patterns. Has an extra power supply.

BLUE LED- can be used for optogenetic stimulation and fluorescence activation. Can be nicely fit in the extra lens adaptor for better fluorescence imaging. Also has an external power supply.

NOTE1 except the peltier, all other modules use extra power from a powered USB hub (5V 500mA per module)

Note2 The peltier module still has problems wih overheating after being used for prolonged periods on high (35°C) or low (18°C) temperatures. We are trying to come up with a good solution for it.