To conveniently facilitate local convenient off-site R&D facilities for the ESP32 and Horticulture project, a small greenhouse 'lab' was constructed, based upon a 'VegTrug' Tomato greenhouse. This structure has a small footprint, alowing it to be unusually located within the cockpit of 'Lena Mary', my dry-docked Moody 40 sailing yacht stripped of its steering gear.
| The basic 'VegBot' frame. | The 'VegBot' frame in the cockpit (looking aft). |
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| Air quality control in the VegBot | |
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| Air conditions within the VegBot are regulated under the control of the ESP8266 Local Host Module. Minimum temperature is established by a heater control loop which is activated whenever the actual temperature falls below the setpoint temperature by a set margin (nominally 1 degree). Deactivation occurs whenever the actual temperature exceeds the setpoint temperature by more than the same set margin. Should the actual temperature exceed the solar gain margin (nominally 3 degrees) even when the heater is off as would be the case under summer conditions, induction and extractor fans are activated to introduce colder ambient air from and exhaust warm air to the outside space under the VegBot. Irrespective of the temperature control status, the induction and exhaust fans are activated to ensure that the air in the VegBot is completely changed at least once every 4 minutes. |
Maintaining a uniform temperature throughout the VegBot is only posible if the enclosed air is continuously recirculated. The recirculation fan at the head of the reciculation pipe lifts heated air from below the centre shelf and pushes it out into the space above the top shelf. From here it cools and by gravitation moves back down into the lower regions of the VegBot. Ventilation pipe (rear) and recirculation pipe (front). |
 Ambient air induction fan and recirculation fan atop the ventilation and recirculation pipes respectively. |
 Extractor fan in base of VegBot. |
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The heater (right) is a 500W ceramic element PTC device which is both fast heating and safe to use in an enclosed environment. The humidifier (left) is a generic 2.8l domestic device. Both are controlled via isolating relays from the Master module. |
| The VegBot Control Centre and Camera | |
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 | The Control Centre comprising (from bottom to top) with recirculating and ventilation pipes behind:
The 8-port 5V usb power supply delivers power to the Local Host Module, transducer fan, Camera Module and recirculation and ventilation fans. The ESP8266 Local Host Module is equipped with a fan which ensures that the transducers are continuously fed with ambient air, without which the control loops would suffer considerable lag and significant deviation from their setpoints. The ESP32-CAM Camera module. |