sensors / keychain communication

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sensors / keychain communication

Post by bidule97 » Mon Dec 11, 2017 11:23 am


I would like to have a sensor talking to a keychain.

The sensor can have two states "on" or "off". The sensors should be on "on" state when a 2 to 20kg weight is on top of it and should be in "off" state when no weight (or under 2kg) is on top of it.

When the sensor goes "on" it sends a "in" message to the keychain every 5s
When the sensors goes "off" it sends three "out" message to the keychain one "out" message every 5s and then it stops transmitting

When the keychain receives a "in" message it turns on a green light.
When the keychain receives a "out" message it stops the green light
If the keychain does not receive a "in" message within 20s without having received a "out" message it turns on a red light and an buzzer alarm

The user can stop the alarm by pressing a button on the keychain

The distance between the sensor and the keychain should not exceed 5m.

Can anyone help me to design this circuit?


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