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Strobe Doorbell

July 5th, 2019

Ideal for the deaf or hard-of-hearing, the strobe doorbell uses a modified strobe light to indicate someone is at the door.

Step 1: Materials + Tools





Step 2: Program the Trinket

Upload the linked program to the Trinket. Reference adafruit's guide when uploading to the Trinket.

Step 3: Prep Strobe Light

WARNING: Risk of electric shock. Strobe light runs on 120VAC. Do not operate with strobe light enslosure open. Even with power source disconnected, be wary of capacitors retaining a charge

Remove any power source. Use the #1 screwdriver to open the enclosure. Identify the 5V power supply. My strobe light was missing the 5V connector, so I soldered directly to the strobe light PCB. Identify the LED common wire. Look for the (-) symbol on the white connector. Cut the LED common wire in half.

5V power supply

LED common wire

Step 4: Solder the Receiver PCB

Use the below picture for reference when arranging the parts on the PCB. Solder the parts to the PCB according the below schematic. The transistor's pinout can be identified via its datasheet. Do not wire the 5V or the LED common wire from the strobe light yet



Step 5: Integrate the Receiver

Protect the Receiver PCB from shorting insiding the enclosure. Hot glue the LED exposed contacts.

Prep the micro-B USB cable by removing the USB A end and identifying the 5V wire and common wire. Connect these respectively to 5V and common of the strobe light. Connect the micro-B end to the microcontroller. Next, wire the LED common (split in half) to the transistor. The side from the LED goes to the collector of the transistor. The side from the strobe light goes to the emitter of the transistor. Return the strobe light enclosure.

When the RF Remote Control button is depressed a 315MHz signal is sent to the receiver. Pin D2 of the receiver is momentarily set HIGH. This momentary HIGH is read by pin D0 of the microcontroller, which sets its pin D4 HIGH for 10 sec. Pin D4 closes the collector and emitter of the transistor, completing the path of the LED.

Hot Glue

USB cable prep

PCB Placement

Step 6: Enjoy

Mount the RF remote control at the door. Place the strobe light somewhere within range of the RF remote control and in an area with high traffic, such as a living room. Plug the strobe light in, close the blinds, turn off the lights, sit in the middle of your living room and wait patiently for a friend to come over and ring your new doorbell!

Next Step

A single RF remote control can be used to control multiple receivers, one for each room.