I have been known to use it after dark...
I have a terrible memory..
I now have a dead battery.
Yep, everyone's done it. Left their lights on when they turn off their car or truck. Fortunately, most have an alarm that will go off to let them know what they've done. Not so much for my Ford. My F150 is less a fully formed vehicle than someone's attempt at a junkyard reconstruction. Let's just say it's a great yard truck with a bit of mystery.
The wife and I were out kayaking the other weekend. Out before dawn, it was easy to see that I had left my lights on when we were getting the kayaks unloaded. On the way home there was a bit of fog but otherwise daylight. Turned on the lights for safety. Arriving home we unloaded, cleaned up and left the lights on to fully drain the battery - just for good measure.
Sooooo, after a new battery and day of kicking my own posterior I went online to try and find a 3rd party headlight alarm. Either they aren't making them as much as they used to or my Google skills have diminished. Either way, I was not finding what I was looking for and I knew if i relied on my own memory I might as well just put aside the money for a new battery now.
I really wanted a battery alarm so I sat myself down with a pen and paper and started sketching out some ideas. How the alarm would be powered, what would control when it would and wouldn't go off, etc. Once I had a working idea I stopped by my local Hack Shack and picked up just a few items. Those, along with my standard stock of wires and do-dads, I was all set!
Step 1: A Sketchy Idea at Best
As I mentioned, I have about a thousand sketches in my office. No, seriously. I also find it helpful to sit down from time to time and go over them. It's interesting how an idea from years ago can be key to a current project.
Step 2: All You Kneed Is "stuff"
As I mentioned, I stopped by my local Hack Shack at lunch time and picked up spare odd and end. A few bits and pieces. An apple and pear - wait, wrong slang.
Here's what I picked up for under $20:
12V Mini Relay NO/NC 275-0005
3amp Fuses 275-1025
12V Buzzer 273-055
Project Box 270-1801
On the bench I had the rest of what I needed:
Copper foil wire
20awg wire of various colors
A small breadboard from another project
Couple of fuse holders
As far as tools went for this build, all pretty standard.
I used a Dremel to cut the buzzer opening in the side of the box and slice the lip of the box lid. My trusty, but in desperate need of replacement, soldering iron. Some epoxy to hold the parts (more on that later), some shrink wrap tubing and a label maker. Last but not least, my Fluke multimeter.
Step 3: Build It and It Will Buzzzzzzz...
First I Dremeled some notches into the breadboard so it would fit snugly in the project box. The inside of the box had some divider slots so I used them to keep the board from moving around. Onto the board I epoxied the relay and both fuse holders. Excellent luck, everything just fit.
On the project box I also used the Dremel wheel to open up a "buzzer" side opening on its side. I had to grind out a small lip on the box lid so that the top-flush buzzer wouldn't interfere with closing the lid. A few drops of epoxy and the buzzer is now sitting flush in its opening.
Three holes drilled in the opposite side of the box allowed me to run three separate 20awg color coded wires (Black = ground, Yellow = Accessories, Purple = Headlights). Inside the box, after leaving enough room for the connections, I tied the three wires into a knot so that pulling the wires wouldn't damage anything inside the box. A few hits with the soldering iron and everything was connected. I used a couple pieces of shrink wrap tubing to protect where the wires were soldered together.
A quick note on the relay. This relay has both OPEN and CLOSED connection points. Without coil voltage this relay defaults to the "closed" position. When voltage is applied to the coil the relay switches to the "open" contact. I used this relay because I wanted the headlight power to flow through the relay to the buzzer. However, I also wanted to the buzzer to NOT WORK when the truck was running (not sure why but it's what went through my mind). To that end, I hooked up the coil contacts to be powered when the truck powered accessories (e.g. ON and running ). So, when the truck is running the relay disconnects the buzzer power circuit and when the truck is off the relay defaults back to a completed circuit. So, the only time the buzzer could possibly work is when the truck is OFF and the headlights are ON.
On the relay picture below. The top left pin is for "normally closed" the bottom left is "normally open" , the top right pin and bottom right pins are for powering the coil (12v applied here flips the relay from closed to open). The middle right pin connects to either the closed or open pin, depending upon if voltage is applied to the coil pins.
Instead of trying to splice wires I opted for, in my opinion, a slightly better and less prone to fault option. I had some flat copper wire laying around that was a hand me down. From the box it looked like it was manufactured in the 60's. NEVER throw anything out!. Anyway, snipped off a couple of pieces, bent to shape, tinned and soldered onto the ends of my wires. Each would perfectly fit onto the foot of an automotive fuse. No splice and no worries about cutting wires. Plus, they fit perfectly into the fuse slot.
Step 4: Test, Label and Test Again.
For the first step I simply connected the ground and "headlight" wires to a 12v batter.
Yeah, it worked!
Next step, leaving the first wires connected, I then attached the "accessory" wire to the +12v terminal.
No more buzzing......
I labeled the box and I labeled each of the wires. Although I know 'now" what each wire does, there's no guarantee I'll know what which wire does tomorrow. Heck, I can't even remember to turn off my headlights, thus the box!
You cant see in this picture but I also labeled the fuse rating, "spare fuses on board" notice and some contact info.