TENTACLE: A Transportable Temperature and Heatwave Control Device

This tech spec was submitted by Markus Hermann as part of the University Technology Exposure Program.

Problem / Solution

Climate Change poses some serious threats and risks that disturb aquatic ecosystems. The severity of the increase in temperature, intensity, and heatwave frequency causes unpredictable consequences to the environment. Anthropogenic stressors, like climate change and chemical release, cause unprecedented interaction effects on ecosystems. This complexity could cause future temperature alterations and unprecedented interaction effects on ecosystems. Hence, the need to better understand these stressors through experiments. However, constant temperature regimes are being used in temperature-chemical interaction effects and climate-chemical multiple stressor experiments. These do not correctly represent the realistic daily temperature variations of the natural environment.

TENTACLE is an Arduino-based temperature and heatwave control device that is transportable, inexpensive, multifunctional, and easily reproducible. This device can simulate different and environmentally realistic GCC-related changes in water temperature in indoor and outdoor aquatic micro- and mesocosms. It also has the capability for long-term recordings and manipulations of temperature changes. TENTACLE also offers water temperature monitoring and manipulation of up to three different climate change-related scenarios: (i) natural or ambient sinusoidal fluctuations, (ii) elevated fluctuations, and (iii) heatwaves as extreme events. With its replaceable heating elements and low-cost materials suitable for field studies, TENTACLE creates high flexibility for researchers who may conduct in- or outdoor, small- or large-scale, fresh- or salt-water experiments at different geographical locations.

Design

MECHANICAL COMPONENTS

The TENTACLE device comprises two water-resistant boxes with identical hardware called Box 1 and Box 2. The device duplication allows simultaneous control of up to 32 aquatic test systems. It is designed for outdoor use, which is why its materials and components are weather resistant. These two water-resistant boxes are IP68-rated polymer-made with a metal front and a panel with rubber rings for air sealing and resistance to dust and water. An IP44-rated CEE-contact stop with the corresponding cabling is used for a protective high voltage power supply.

The front panel is custom-made via laser cuts to connect the digital temperature sensors and heating elements. It is designed to fit 16 XLR and 16 STAS connectors. XLR connectors for the sensor cables are suitable for outdoor use, while the STAS connectors are protected against dust and water splashes. These connectors have an adequate power rating for the device's requirements. 

TENTACLE's main component is the Arduino microcontroller to switch heating elements on and off via the main configurations of the computer GUI. This is connected to a computer via a USB Type B-port to upload or edit the Arduino source code. Different electrical safety features are combined to prevent harm with accidental water spillage or water entry. The power supply will immediately be turned off when an electrical short-circuit or an overload of the device occurs.

TENTACLE has 32 sockets for digital temperature sensors and 32 sockets to connect replaceable heating elements. The temperature sensors feature adjustable data saving intervals providing information about the natural temperature dynamics, changes, and manipulation statuses while also being ideal for continuous indoor and outdoor applications. The electricity sockets feature different electrical power for temperature manipulations in aquatic test systems of various sizes.

The cables of TENTACLE are waterproof and weather resistant. These also featured a stainless steel- encapsulated temperature sensor. When fully submerged in water, these sensors measure over a wide temperature range (-20C to + 85C) with high accuracy (±0.5C) for changing temperatures (-10C to +85C). Shirk tubing serves as a protective covering for the connections between the cable and the sensors. The electricity cable can fit all conventional heating elements because it has a waterproofed Schuko-connector (PCE).

POWER

The last electricity plug of Box 10  can supply constant electricity for the computer during field experiments.

For indoor experiments, each box is directly supplied via a CEE cable with a plug. While for outdoor experiments, each box is indirectly powered via two electric extension cables, connected to a power distributor with two CEE sockets. All power current connecting parts were boxed in waterproof cases or placed indoors for additional protection. The power distributor connects to the main power supply to secure the device's full functionality.

ELECTRICAL COMPONENTS

The maximum power demand for small and large experimental designs, 3000 and 18000 W, is calculated for ideal power distribution. Hence the need to split power over four power leads with each lead connected to a separate circuit breaker. One box uses three power leads to power the heater section, with each lead connected to two times 5 and one times 6 heaters. There are fuses for every heater after every circuit breaker for the power lead in the middle of the box. Thus only one heater will switch off if one of the heaters malfunctions.

The fourth power lead supplies the Controllino Mega. This is an industrialized Arduino with enough outputs and processing power to control a Solid-State Relay (SSR). The SSR switches on the heaters. SSRs are used for TENTACLES because of less power cost, less electrical interference, less heat generation, and a longer lifespan than mechanical relays.

ARDUINO SOFTWARE & COMPUTER INTERFACE

The software works off a configuration given via the computer interface and can be opened in any C/C++ editor to make adjustments. The code will run with the same configurations because of the savings in the EEPROM after an intended reboot or when, on some occasion, the computer itself has lost power. The one-wire protocol reads over the sensors, and these sensor readings are sent to the computer via a UDP Ethernet Connection. The interface establishes easy access to all functionalities of TENTACLE. Tab groups separate all recordings from set-up options.