Used slow whoop alarms can be recycled into a portable version by adding a switch, a battery and a project box. This portable version is useful duringÂ emergency response training. Persons attending the training can get used to the slow whoop sound and recognizing the alarm when used in real hazard situations.
The slow whoop alarm used in this schematic needs 12V or 24V to work. A simple PP3 9V block battery also works perfect, even when the battery is nearly empty there is still some sound. This slow whoop alarm needs about 10mA of current, this means that the portable version can be used for 50 hours continuously. When using it for 30 seconds each training, this device can be used for 6000 training sessions. However, the battery will probably die from age before all the energy is used.
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