The device will use a ordinary digital alarm clock to trigger an electric motor momentarily. The average tinkerer can easily build a similar machine and I hope my Instructable guides you smoothly through the process.
Lets get to it!
Step 1: Lets Get the Parts We Need
(I have tried to include a part number to get most parts although some of these things can be found locally too)
1. A digital clock radio - the bigger and cheaper the better.
2. A car door lock actuator - (AllElectronics #DLA-1)
3. Machinists Magnetic Base - (LittleMachineShop.com #1237)
4. Prototype Circuit Board - (Digikey #V2012-ND)
5. NAND Logic Gate - (Digikey #CD40107BE)
6. MOSFET - (Digikey #IRFZ14PBF-ND)
7. Potentiometer 100k - (Digikey #490-2971-ND)
8. Capacitor 10uF - (Digikey # P5148-ND)
9. Resistor 1k (qty 2) - (Digikey #P1.00KCACT-ND)
10. Diode 1N4001 - (Digikey #1N4001FSCT-ND)
11. Battery 9v Alkaline
12. Miscellaneous - (zipties, wire, hardware, glue, elastic band, heatshrink, etc)
1. Various screwdrivers
2. Soldering Iron
4. Hand drill or drill press.
6. Hot glue gun
7.Heat gun or lighter
8. Hammer with center punch.
11. Permanent Marker
Step 2: Design the Circuitry
The solution is a simple circuit that will briefly turn out actuator on and then off, even though the input is always high.
Step 3: Test the Circuit
I always test things on a breadboard before soldering. I got mine from AllElectronics (#PB-1680) and it has been invaluable.
Apologies,I forgot to take a picture at the time but I did take a brief video of my test setup.
Step 4: Layout the Circuit on the Proto Board
Step 5: Cutting the Board Out
Be sure to clean up the edges with a file when you are finished cutting.
Step 6: Solder the Components
Place the components back into their spots and turn your soldering iron on. We're aiming for shiny solder joints that are not too blobby (although that can tricky with the pads on these proto boards)
Don't be too hasty to trim the leads, you can bend them and use them as some of your jumper wires if you want.
Use wire to complete the rest of your connections, mine is a little messy but it will get the job done.
Step 7: Disassemble the Clock Radio
Make sure you unplug the clock or remove its batteries, no need to shock yourself or accidentally short circuit it.
Remove all the screws that are keeping the clock together. I find that using one of those small magnetic trays to keep the screws from getting lost is a very good idea. If you want to buy one of these trays you can very easily make your own.
I've included an Instructable-Within-An-Instructable in this step's image notes to show you how to do it!
Step 8: Find Your Triggering Signal
For our circuit to work we need a 5v signal that will appear when the clock radio's alarm goes off. This can be tricky because (as in my case) there may be no schematic available anywhere.
First I had to find the clock's microcontroller as that would have some output lines to turn the speaker on. This was pretty easy on my clock as it only had 2 ICs. The writing on the chip was faded so I had to guess what pin to use as the trigger.
I did this by first powering up the clock with no alarm set, and then (being careful not to short out anything) use a multimeter to measure the pins of the chip. In my case there was quite a few pins that were at 0v.
Then I set the alarm to go off and remeasured each pin. Some of the pins that measured 0v previously now read 5v. Hooray!
Step 9: Add Your Trigger Wire
Now we need to run a signal wire from the pin of the microcontroller out to the circuit board we built. I soldered a length of 24ga wire directly to the pin, being careful not to create any solder bridges on the adjacent pins.
I routed the wire out the back where the clock's AC power cord exits.
Be sure to strain relief the wire so that it won't break at the solder joint if it gets tugged on. I simply hot glued it to the circuit board in the clock.
Step 10: Connect the Signal Wire to Your Circuit Board
Notice the diode that suddenly appeared on the circuit board. I completely forgot to include it in Step 4, good thing I left extra space!
Step 11: Modify the Actuator
Since the actuator will only be powered in one direction we need to make sure that it will stop pushing the button after the time cycle. We are going to do this mechanically by using a small rubber band as a bungee to pull the piston back in.
I used a hacksaw to cut a small slot in the tip of the actuator so that I could keep the rubber band in one piece.
I used a washer with screw as a flange to make sure the band doesn't slip off.
Step 12: Attaching the Actuator to the Magnet Base
To mount the actuator, I ran a long screw through the bored out mounting hole on the actuator casing. Then I tightened the knurled nut on that screw, and the thread the entire actuator assembly onto the threaded rod of the magnetic base.
Step 13: Cut the Steel Mounting Plates
I dug around my scrap bin until I found an appropriately sized strip of steel. It was not big enough to cover the magnet so I cut it into 2 strips instead.
I used a hacksaw again to cut the steel, the only difference was I used cutting fluid (Rapid-Tap) this time, it makes cutting hard materials a breeze!
Be sure to clean up the edges with a file, not only will it make the plates look better but it will protect you from nasty cuts as well.
Step 14: Drilling Holes in the Steel Plates
My plan to to mount the plates with a couple #4-40 screws with nuts so we'll need to drill some holes through the steel.
First of all I would highly recommend to anyone who likes building things to invest in a drill press. You can get a 8" bench-top drill press for $80-100 and in my opinion it will be the best money you've ever spent. (Although these days I do wish mine was a little bigger and had a wider variety of speed settings)
I follow a 4 step process when I drill holes:
1. Measure and mark the spot you want to drill.
2. Use center punch on mark.
3. Drill hole.
4. De-burr hole with a countersink.
Step 15: Drill the Holes in the Clock
The clock frame piece was too awkward to sit on my drill press table so I just used a power hand drill instead, plastic is easier to drill this way.
Always make sure you take apart the device before drilling. One of my earliest tinkering memories is destroying my toy RC monster truck by accidentally drilling holes through the frame and into its circuit board.
Once all the holes are drilled we can mount the plates with the hardware, reassemble the clock, and then stick the magnetic base on.
Step 16: Mount the Circuit Board
I decided to use some "cable tie mounts". These are just little molded pieces of plastic with sticky adhesive foam on the bottom. If you stick them to a flat clean surface they have a crazy amount of holding force.
Step 17: Wire Everything Up
I started by extending the wires on the actuator so they can reach the circuit board. I used 18ga wire for this job, making sure the wires were long enough to adjust for any position the actuator is in.
I just like using a basic lap splice instead of twisting wires together. First I make sure I've slid heat shrink tubing on before soldering. Then I strip and tin both wires that to be spliced together. Then I melt the tinned wires together, slide the heat shrink in place and cover the connections.
I used 24ga wire to run the battery connections out to the right spots on the circuit board.
I used another cable tie mount to add some strain relief to the wires, a little messy but it will do.