Team:SDU CHINA/Hardware
We have produce four generation hardwares
| V1 | V2 | V3 | V4 | |
| safety | USB powered | It is not safe to use 220v power to connect the transforme | Arduino 5v output serves as power supply, which is relatively safe but not stable. | Using 9v student power is safe and stable. |
| wavelength of light | It can give out the lights of different colors, but their wavelength is uncontrollable, which might lead to the leakage of optogenetic switches. | It can only generate the green light and the red light. | The lights that we can get include: red light( 640-650nm)green light(530-535nm)blue light(460-465nm) | Red light(620-630nm), green light(520-525nm) and blue light(460-465nm) can all be available. |
| control | The control pattern is fixed | uncontrollable | Manual control by changing logic circuit | It can be controlled by app automatically or remotely without changing logic circuit. |
| Illumination intensity | Uncontrollable | Uncontrollable | Uncontrollable | controllable |
| Robustness | The connection between the bulb and another bulb is easy to break. | As to the 220v power, we don't take its stability into consideration | The signal line is not durable enough to be the power line, and the resistance will increase with use, thus affecting the light intensity. Therefore, it is not suitable for long-running experiment | We use the signal line in the control circuits and the electric wires in the power circuits respectively, so as to achieve the seperation of control and power. The dedicated line for each is very stable. |
In the first generation, we used normal RGB LED strip light with USB as its power supply. But the color of the light was not pure and the wavelength was uncertain, which caused the increase of leakage of the optocoupler. Besides, the voltage was not stable, which led to the failure of the experiments. To solve these problems, we decided to use monochromatic single wavelength LED as the light source after discussing with UCAS-China.
The second generation：To reduce the leakage of the optocoupler, we use the monochromatic LED with single-wavelength. As to the circuit, the 220v high-voltage AC is stepped down by the transformer and then connected to the rectifier to power a monochromatic LED up. The problem is we can't adjust the colour of the LED or control the light flexibly, and because of the 220v power supply, the hardware is a little dangerous.
The third generation: The second-generation hardware was designed to solve the above two problems. On the one hand, to adjust the colour, we used three monochromatic single-wavelength LEDs of red, green and blue for each hole. The three LEDs were used together as the light source. On the other hand, we used the Arduino Uno powered by USB to control the LEDs inserted on the breadboard and it served as the power source for the LEDs. This allowed us to control the colour of the light and we eliminated the danger of using the high-voltage power supply. However, after testing, we found that the voltage of Arduino was not stable enough to support the small bulb. As a result, the light of the bulbs became dusky after the long-running experiments. Besides, the circuit on the breadboard was astable and is prone to short circuit. We also found some problems with the designing idea. In the second generation hardware, we designed Arduino Uno and the "control circuit" of DuPont line as a "power circuit" and used signal lines as power lines. The current carrying capacity of a typical wire is about 6-10 amps per square millimetre. The larger the current, the weaker the current carrying capacity. If the high current is used to transmit the signals, the skin effect also has to be taken into consideration. The higher frequency means the skin effect will be stronger and the current-carrying capacity will be weaker. Therefore, due to the insufficient current carrying capacity of the DuPont line, the short circuit will happen after experimenting for a period.
In the improved third-generation hardware, we use a multi-level distributed control system combining RaspberryPi and Arduino. We can type in a command through the APP on the phone and send it to RaspberryPi via the LAN network. RaspberryPi continue to send it to Arduino. After decoding the command, the arduino pro mini can accordingly produce three different PMW digital signals and control the color and brightness of the bulbs via optocoupler switches. Each of the three bulbs is a group and they are connected in series circuit to 9v. Student power or spare battery, thus having the same color and brightness. It is easy to control the color of the bulbs via the mobile phone App. On the universal board, the color and brightness of adjacent light bulbs may be different. To avoid interference between them, we place a 3d printed hollow cylinder around each light bulb.
