Modern gas-sensing technology embraces the principle governing “smart” devices: integration of wireless communication. TI provides a Gas Sensor Platform with Bluetooth® low energy (BLE) to serve as a reference design to aid customers in developing next-generation industrial and consumer end-products capable of detecting gases such as chlorine dioxide, hydrogen sulfide, carbon monoxide and ammonia. The combination of flexible analog front end (AFE) with a low-power wireless radio allows the design of products in a variety of applications: industrial process and controls, building technology and comfort, household CO sensing, and mining.
The key components composing the Gas Sensor Platform are the LMP91000 analog front end (AFE), the CC2541 2.4-GHz Bluetooth low energy and proprietary SoC, the LM4120 precision micropower voltage reference, and the TPS61220 boost converter. Repurposing components for different sensor applications is as easy as updating the LMP91000’s firmware and changing the sensing component; a resistor may be added if using 2 or 3-lead electrochemical sensors. LMP91000 is powered by a CR2032 coin-cell battery and interfaces with the CC2541.
Wireless connectivity
TI’s decision to include BLE into gas detection is rooted in ease of access; by seamlessly connecting to an iOS application running on iPhones and iPads, it’s possible to wirelessly verify a sensor’s operational condition at any time. Fundamentally, Bluetooth technology seeping its way into traditionally unconventional devices such as gas sensors is nothing unusual; it’s a natural part of the Internet-of-things movement, propagating integrated manufacturing worldwide. BLE improves safety, increases sustainability, and grants user mobility.
Gas signatures are transmitted wirelessly to the Smartphone using Bluetooth low energy.
LMP91000
The LMP91000 supports many different toxic gas sensors and may be configured to accommodate the critical parameters of each; it is therefore central to the entire reference platform and useful in any micropower or electrochemical-sensing application. The component's flexibility allows the support of multiple electrochemical sensors, such as three-lead toxic gas sensors and two-lead galvanic cell sensors, with one consolidated design. LMP91000 supplies a complete signal path solution between a sensor and microcontroller, generating output voltage proportional to the cell current.
LMP91000 functions between a voltage range of 2.7 and 5.25 V, enabling micropower applications to operate effectively. Although the total consumption is less than 10 μA, additional savings is possible by switching off the TIA amplifier and shorting the reference electrode to operate with an internal switch. The extremely low power guarantees extra battery life.
CC2541 2.4GHz Bluetooth low energy and Proprietary SoC
The CC2541 system-on-chip allows the creation of full-bodied network nodes using minimal bill-of-material cost. In essence, CC2541 is a system-on-chip solution power that's optimized for Bluetooth low energy and 2.4-GHz applications. The CC2541 offers short transition between multiple operating modes to yield added low-power consumption when the device is paired with systems requiring low power consumption.
Moreover, the solution merges powerful support features and peripherals through the union of a leading RF transceiver with an industry standard enhanced 8051 microcontroller, in-system programmable flash memory, 8-Kbyte RAM, and more.
TI’s commitment to providing a robust reference design is brought one step further through the inclusion of the hardware files and source code of CC2541 as open source, to encourage full application customization for each individual solution and fast market access.
LM4120
The LM4120 is a precision low-power lower-dropout bandgap voltage reference. Voltage references produce a constant voltage over time regardless of temperature, load, or power supply changes, thus rendering the LM4120 ideal for battery-powered portable devices.
The module consumes only 160 µA of supply current and operates within an input voltage ranging from as low as 2 V, to as high as 12 V. If power mode is enabled, the current will further drop to as low as 2 µA. Subsequently, LM4120 is very flexible, featuring two grades (A and Standard) and seven voltage options. The device performance is ensured over the industrial temperature range (−40° to +85°C), while certain specs are ensured over the extended temperature range (−40° to +125°C).
TPS61220
Serving as a low-input-voltage boost converter, TPS61220 is the final component in this reference design. The converter acts as a power-supply solution for all products powered by the following batteries types: single-cell, two-cell, or three-cell alkaline, NiCd or NiMH, a one-cell Li-Ion or a Li-polymer battery. Furthermore, TPS61220 protects circuits against overtemperature, overvoltage and input undervoltage lockout.
TPS61220 includes an operating input voltage ranging between 0.7 and 5.5 V, and is available in either an adjustable output voltage or a fixed output voltage version. Simultaneously, the output voltage of the adjustable variety is programmable within the range of 1.8 to 5.5 V using an external resistor divider, but is set internally in the fixed output version. Under typical operating conditions the device performs at up to 95% efficiency.
Learn more about Bluetooth low energy and Gas Sensor design at TI’s official webpage.
Orderable part numbers, in stock at Mouser:
a. CC2541
b. LM4120
c. LMP91000
d. TPS61220
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