S.O.S. Wristband

S.O.S. Wristband is a tool which can help the survivals trapped in the building and the rubble can be found by the rescue team fast and easily.


There are many natural catastrophes happening in the world every year, and these natural catastrophes killed thousands of people. Therefore, how to rescue survivals quickly becomes an important issue for the rescue team. When natural catastrophes happen in the city, people tend to be trapped in buildings and rubbles. The rescue team needs to find and save the survivals in the 72-hour golden window, which is considered the optimum time for rescue. Therefore, in this project, I have designed a tool that helps survivals be found faster and easier. 

When disasters happen, people can follow the emergency exit lights to escape from the room, and the emergency backpack including many tools can help people survive after they escape from the building. However, there is no tool in the backpack that can help people be found when they are trapped in the building.


I have observed that there are many emergency lights in a building. Thus, I was thinking how to design an emergency light which can help people be found when they are trapped in the building.


Ideation & Experiments

S.O.S. Wristband

When electrical power outage happens in the disaster, victims can switch on the LED for lighting and use it to find a way out. As they switch on the LED, the S.O.S. signal generator will be turned on at the same time to send S.O.S. signals.

There is a heartbeat detect circuit in the wristband, this circuit will detect victims' heartbeat. If the victim’s heartbeat stops, the S.O.S. signal generator will also stop sending S.O.S. signals. Rescue person can find the victims by using an instrument that can position the S.O.S signal.

Wristband Schematics

Here is a simple schematic for the S.O.S. wristband, this circuit is connected to a set of charged parallel super capacitors.

When the heartbeat circuit detects the heartbeat signal, this heartbeat circuit will output the signal high to FET to switch on the active RFID circuit, and then the active RFID circuit will send S.O.S. signal.


The emergency light is switched off when there is no disaster or electrical power outage.

The emergency light will be turned on when the supply mains be cut, or be turned on by building central control system when the disaster is coming. The survivals can then get the S.O.S wristband easily and quickly.

When survivals turn on the LED, the S.O.S signal generator sends the S.O.S signal continually.

The rescue person can position the S.O.S signal to find the live survivals.

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