You’re late for work. As you hustle out the front door, the furthest thing from your mind is the afternoon’s dentist appointment that you’d scheduled last week. You’d have probably forgotten all about it — if you hadn’t thought ahead by programming a home-built device to give you a voice reminder as you pass it on your way out.

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Just record your reminder on the device (“Dentist at 3 o’clock,” or “Pick up the kids at baseball practice”), set the timer for when you’ll need to hear it — up to a week in advance — and from the set time forward, it will play whenever you walk near the attached motion sensor. Sure beats having to remember everything yourself.

DIY Voice Reminder


** Part Part # Source Price|**
PIR Sensor Module 276-033 $9.99
Recording Module 276-1323 $10.79
NPN transistor 276-2016 $0.79
.1 uF cap, 50 V 272-1069 $1.49
SPST pushbutton sw red 26623 $0.66
SPST pushbutton sw blk 26649 $0.7
Perforated board 276-1395 $2.79
Wire wrap socket 37411 $1.19
LM555 Integrated Cct. 27422 $0.29
1 farad capacitor 142957 $4.49
Knob 162481 $1.49
Pot 500K with switch 263848 $1.59
4 AAA battery holder 216339 $1.55
Acrylic butter dish 104461 $7.95
1 K resistor 30BJ250-1.0K $0.22
470 K resistor 30bj250-470K $0.22
4.7 M resistor 66-RCO7GF475J $0.25

1. Drill holes in your chosen enclosure, following the drilling template. Glue the speaker [A], microphone [B] and motion sensor [C] to the enclosure. Mount the buttons [D] on the outside.

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2. Build the timer circuit board, which lets you specify a time delay after which the message will be enabled. Calibrate the timer.
3. Connect the timer circuit board to the “play” wire from the record module, the “play” button, the power wires from the battery, and the sensor and record modules.
4. Move the switch on the battery holder [E] to the “on” position. Hold the red button to record a message, and press the black button to hear it. Turn the rotary dial [F] counterclockwise to the “off” position. Turn the dial clockwise to set the time delay, after which any movement in front of the sensor will trigger the message.

A schematic diagram can be downloaded here.