Ricoh Launches Environmental Sensor Board for Development of IoT Devices

Ricoh Electronic Devices Co., Ltd. in Japan launched a special circuit board for electronics engineers developing new IoT devices.

The RIOT-001 is an environmental sensor board that measures the ambient temperature, humidity, air-pressure and illuminance.

The data is collected by an MCU and sent by Bluetooth (BLE) to smartphones or tablets with a dedicated application program.

Ricoh developed this special circuit board because of the huge interest from the market for our recently launched power management ICs intended for IoT applications.

The RIOT-001 contains various power management ICs with an ultra-low supply current and low output noise level. IoT devices require specific functions such as maintenance-free operation from an independent power supply, low energy consumption (extending the battery life), high accuracy sensors, wireless communication, small components, etc. This new sensor board makes it easier for designers to develop new IoT devices and contributes to shortening the time-to-market.

The sensor board is powered by a photovoltaic cell (not included), the electric energy is collected by the R1800 Buck DC/DC Converter for energy harvesting.

The converter has an internal maximum power voltage setting to define a voltage level at which the photovoltaic cell produces its maximum power and therefore optimizes the amount of generated power. The R1800 stores the collected energy in a unique Small Lithium-Ion Secondary Battery (SLB) with a capacity of 0.35 mAh, manufactured by Nichicon Corporation.

Also, the IC has reverse current protection preventing charging loss. Theoretically, when fully charged, the SLB battery can provide power to the IoT board for approximately 20 hours. By using a photovoltaic cell according to the specifications of the RIOT-001 board makes battery-free operation possible, saving maintenance costs for replacing the batteries regularly.

Another Buck-Boost DC/DC converter RP604 is present on the circuit board, with its wide operating voltage from 1.8 V to 5.5 V, it regulates the fluctuating SLB battery voltage as it is charging and discharging during operation. The DC/DC Converter achieves a high-efficiency operation in both standby and active modes. The purpose is to provide stable power to an onboard MCU, Bluetooth (BLE) transmitter and the four sensors.

The SLB battery voltage is measured by an advanced battery monitor embedded in an RP124 LDO. A conventional way to measure the remaining battery charge is using an external resistor divider + MOSFET connected to an A/D Converter. However, such circuit has a considerable high current flow to ground, draining the battery and limiting the lifetime of the application. The RP124 provides a simple solution with a built-in resistor divider and voltage follower as a buffer. As an advantage, this circuit has a much lower current flow to ground and the output is compatible with the input impedance of the A/D converter.

There is an alternative power source available if one prefers not to use a photovoltaic cell to supply power the RIOT-001 board. The RIOT-C01 (sold separately) is an add-on board with a CR2032 coin battery and can be attached to the mainboard, a pair of connectors to connect the boards is already present for your convenience. Theoretically, this board can keep the RIOT-001 board operating for 1.5 years, depending on the sample rate of the measurements. Another second purpose for using the RIOT-C01 is to shorten the initial charging time of the SLB battery since it takes a while for a photovoltaic cell to charge this battery. In this way, the RIOT-001 board is instantly ready for use when powered up.

The measurements of the RIOT-001 are sent by Bluetooth to an Android tablet or smartphone device, Ricoh provides the APK file for installing the application to observe the data from temperature, humidity, air pressure, illuminance and SLB battery voltage sensors. The circuit boards can be purchased from authorized online or local distributors.