CARBON MONOXIDE ALARM
Kidde KN-COB-B
Manufacturer : Kidde
Sensor: Electrochemical Sensor

Reported by Manuela Donoso and Mónica Bate, Feb 15, 2012

The Kidde 9CO5 Battery-Operated Basic Carbon Monoxide Alarm with Electrochemical Sensor. Electrochemical gas sensors are gas detectors that measure the concentration of a target gas by oxidizing or reducing the target gas at an electrode and measuring the resulting current.
Datasheet

Sensor

Carbon Monoxide Sensor or CO detector
Is a device that detects the presence of the carbon monoxide (CO) gas in order to prevent carbon monoxide poisoning. CO is a colorless and odorless compound produced by incomplete combustion. It is often referred to as the “silent killer” because it is virtually undetectable without using detection technology. Elevated levels of CO can be dangerous to humans depending on the amount present and length of exposure. Smaller concentrations can be harmful over longer periods of time while increasing concentrations require diminishing exposure times to be harmful.

Per UL 2034 requirements, the CO sensor will not alarm to levels of CO below 30 ppm and will alarm in the following time range when exposed to the corresponding levels of CO.

(Likely electrochemical. It makes a sloshing sound when I shake it. May contain sulfuric acid or something equally hazardous – so don’t puncture it).

Other Components

MCP604 Dual Operational Amplifier (op amp) Has a gain bandwidth product of 14 kHz with a low typical operating current of 600 nA and an offset voltage that is less than 3 mV. The MCP6042 uses Microchip’s advanced CMOS technology, which provides low bias current, high-speed operation, high open-loop gain and rail-to-rail output swing. The MCP6042 operates with a single supply voltage that can be as low as 1.4V, while drawing less than 1.0 of quiescent current per amplifier. The MCP6042 is available in standard 8-lead PDIP, SOIC and MSOP packages. (datasheet)

Microchip PIC 16CR54C Microcontroller for monitoring the CO sensor and driving the display. The particular chip is ROM-based, which is cheaper but not modifiable. Therefore, the program needed to be mature before mass production.

EFM-290ED Piezo High-output (90 dB minimum) piezo transducer sounder. This make the alarm sound. (datasheet)