Wireless Mailbox Notifier

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WIRELESS MAILBOX NOTIFIER This electronic mailbox notifier sends messages wirelessly over short distances using a transceiver. When the lid of the mailbox opens, it activates a transmitter that sends a signal to a receiver in the house for half a second. The receiver produces an intermittent signal until reset. Building this electronic mailbox notifier requires some knowledge of electronics. In our case, we need to send the signal over 150 meters through the forest. Switch in Mailbox The switch consists of a reed contact that is activated by a magnet when the lid or door opens. A reed contact is weather-resistant and has a long lifespan. It operates reliably with a magnet. The construction of the reed switch is shown in the attached drawings. Dipolantenna (Self-Made) Materials: * 36cm electric tube, 5/8" * 2 x insulated copper electric wires, 2.5mm2, each 17.3cm The dipolantenna can be easily made from two insulated electric wires, each 17.5 cm long. To prevent oxidation, it's recommended to keep the insulation on the wire. The wavelength (lambda) in meters can be calculated by dividing 300 by the used frequency in MHz. In this case, the frequency is 433 MHz, so the wavelength is 300:433=0.69m. A dipol antenna usually consists of 1/4 lambda, so each dipol part should have a length of 0.69:4=0.173 (17.3 cm). By placing the wires into a standard 5/8" electric tube, a solid unit will be obtained. Remark: The distance between the antenna and mailbox must be at least 8.5cm.