# CrowBot: An Educational Robotic System for Growing Food
## 7 Experiments and Results  
Initially, as the basis for future educational implementations, a number of fundamental experiments were performed to verify the controllability of the growth conditions in the GrowBot. Here we will look at the example of controlling the temperature. One such experiment would turn on the white light for 2 h followed by turning on white, blue, and red light for one hour. The fan and air change (1000 mL/h) would be turned ON when the temperature would exceed 35 \({}^{\circ}\)C. Figure 13 shows the result of this experiment. The initial temperature was 26.0 \({}^{\circ}\)C, and in the 2 h period of white light condition, the temperature rose and stayed at approximately 31 \({}^{\circ}\)C, ending at a maximum temperature of 31.4 \({}^{\circ}\)C. At this point, the white, blue, and red lights were all turned on, and the temperature rose to a maximum of 35.2 \({}^{\circ}\)C. The fan and air change turned on, and the temperature fell slightly to stay around 34.8 \({}^{\circ}\)C. When all lights were turned off after 1 h, the temperature again fell to the initial 26.0 \({}^{\circ}\)C over a time period of 1.5 h.  
To test the robustness of the developed GrowBots further, and to gain insight into the growth process inside the GrowBots to inform the educational material development, we performed an experiment in which we planted seeds in nine GrowBots controlled with different parameter settings (programs) for 43 days. The seeds were sown in small rockwood cubes placed in cups that were put into the holes in the water tray. Each GrowBot can contain 16 such cups. The experiment consisted of 4 rows of 4 cups with seeds for parsley, basil, red lettuce, and green lettuce. In this experiment, there was no germination prior to sowing the seeds in the cups. The experiment was performed with nine GrowBots (see Figure 14). All GrowBots had a day light cycle of 18 h of light and 6 h of no light during each 24 h period. Three GrowBots had red light (730 nm, set to 40% of max intensity) and a small component of white (full spectrum) light (set to 16% of max intensity), while the other six GrowBots had blue light (458 nm, set to 40%) and a small component of white (full spectrum) light (set to 16%). The three GrowBots with red light and three of the GrowBots with blue light had nutrient added to the water basin (10 g for 9 L water) at the beginning of the experiment, while the last three GrowBots had (i) nutrient added from the nutrient bottle at the beginning (10 g from the 200 mL bottle), (ii) nutrient added in small drops from the nutrient bottle with 10 mL/6 h (10 g in total in the 200 mL bottle), and (iii) no nutrient. In all cases, the aeration and air circulation fans were set to the same low level. Figure 13: The temperature in a Growbot experiment when white light is turned on at 15:30, white, blue, and red light turned on at 17:30, and all lights turned off at 18:30. The reason to experiment with different color in the GrowBots is that the color of light will affect the growth of the plants. Therefore, the controllability of this parameter can be used as a learning lesson for the pupils. The effect of blue light on plants is related to chlorophyll production, and blue light promotes root development and strong, stocky plant growth. Red light is responsible for making plants flower and produce fruit, and therefore works best in the flowering phase. Hence, for the initial growth of the food plants in the GrowBots, a teacher and/or pupils could possibly make the hypothesis that they would observe stronger and higher initial growth under blue light than under red light conditions. The experiment was performed over 43 days in the period 30 June 2020-12 August 2020. During this period, all the GrowBots were running automatically with the control program (program), and water was added 2-3 times to the water tray of each GrowBot to keep the water level high enough in the tray.