Using a minimum of parts, time and effort, this Instructable can be completed for as little as $13.64+tax, with no knowledge of circuits needed. While I do make use of solder in this project, it is not necessary to know how to solder, and I will present alternatives in the appropriate steps.
Ready to get building? See the next step for parts list and safety points!
Step 1: Parts List / Safety
See below for a complete parts list. As far as wire goes, I put down what I used, but this project is not picky. It is very simple and low current, so most any gauge or solid vs. stranded wire will be fine. I left the wire out of the cost estimate since you use so little and it comes 90ft to a roll.
All Model/Catalog numbers and prices come from Radio Shack's website.
1) 9-Volt Battery Holder - $1.09 (Model: 270-326; Catalog #: 270-326)
2) Heavy-Duty 9V Snap Connectors - $2.69 (Model: 270-324; Catalog #: 270-324)
3) 2.2K ohm 1/2W 5% Carbon Film Resistor - $1.19 (Model:271-1121; Catalog #: 271-1121)
4) SPDT Switch Without Roller - $3.19 (Model:275-016; Catalog #: 275-016)
5) 5mm Red LED - $1.69 (Model:276-041; Catalog #: 276-041)
6) 22-Gauge Hookup Wire, 90ft - $7.69 (Model:278-1218; Catalog #: 278-1218)
7) UltraLast® "9V" Alkaline Battery - $3.79 (Model:ULA9V; Catalog #: 55039849)
8) Unused DVD case
The standard safety precautions apply to this project.
- You will be drilling through metal, so be sure to wear gloves and safety glasses to protect against metal shavings.
- Use appropriate precautions if you use solder to connect the circuit (do not touch hot components, work in a well ventilated area to not breath in solder fumes, etc.)
- Additionally, be sure to watch out for traffic - you will be working at the side of the road on a mailbox, so it would be a good idea to have someone serve as a spotter, or even set out some orange cones.
Step 2: Prepare the Mailbox
1. Remove mailbox from wooden post
2. Using a drill, make two holes in the middle/front of the floor of the mailbox. Then use a sideways pressure while the drill is running to join the holes together and make a slot large enough for the microswitch to fit into.
3. Place the mailbox back on the post momentarily to mark on the post where the hole is.
4. Using a spade bit, make two holes in the middle/front of the wood post. Make them close enough together that they join to make a trench large enough for the microswitch to go down inside.
5. Drill a 1/4"hole in the back of the mailbox, just big enough for the LED to fit into without popping all the way through.
Step 3: Solder Components
Before you install your completed circuit in the mailbox, I would test to make sure that it works and that it is bright enough to suit you. I have a 2.2K ohm resister in there to limit the current so the battery lasts longer. If the LED is not bright enough for you, you can lower the resistor value, put two resistors in parallel (which halves the resistance), or take out the resistor altogether.
Step 4: Hot Glue Everything Down
I glued the microswitch into the hole in the bottom of the mailbox with just the lever sticking above the surface, then I took a 5"x5" square of plastic that I cut from the back of the DVD case and taped it on the front edge over the microswitch to serve as the pedal that the mail rests on to trip the switch.
Glue the LED into the hole at the back of the mailbox, glue the battery holder and any excess wire to the back, and you are finished! Enjoy effort free mail checking!