Okay, so I used a little deception in the title to try to grab your attention. Did it work? Well, it’s more like a Perpetual Projection Clock. This is a "GREEN' project. Theoretically, you won't use up and waste batteries.
PROBLEM: So I am a LAZY OLD GEEK (LOG). I mostly sleep on my side. On one side, I have an alarm clock. But when I turn on my left side, I do have a clock (see picture) I got free from an insurance company but it isn’t viewable at night. Being Lazy and Old, it is hard to turn over to see what time it is.
Trivia: You may wonder since I’m Lazy why do I need to know what time it is? Well, we live in the high desert and I like to take my dog for hikes early before it gets too hot. But not too early.
SOLUTION1: So being a Geek, I decided to build my own custom projection clock. My original design was to take this little projection clock key chain and power it by a $2 solar light that I got on sale at Ace Hardware. But, alas, I found out the little projection clock was powered by two 1.5V button cells and all of the solar lights, I have or seen have a single 1.2V rechargeable battery in them.
SOLUTION2: Well, I happened to find some Rosewill Solar Flash Lights on sale at Newegg for something like 5 for $3. (see picture) Now I opened one up. They have a LIR2032 3.6V lithium rechargeable battery attached to the solar panel, so this should work fine for my needs.
Step 1: Parts List
1 Projection clock key chain $1.35 ebay.com
(Search ebay for projection clock)
1 Key chain solar light $1.00 on ebay.com
(Search ebay for keychain solar torch)
T Hinge, I found one in my junk pile). I don’t know how they’re measured but I think it might be a 2”.
Mini pushbutton, also from my junk pile
Scrap PCB, also from my junk pile
1 heavy duty binder clip. For my headboard, I needed one that would fit on a ½” board.
I bought my key chain solar light from Newegg on a Shell Shocker deal for less than a dollar a piece but they are also available from ebay. Now, I haven’t purchased one of these but they look almost identical with three LEDs so I am assuming they’re the same design.
NOTE: The LIR2032 rechargeable battery in the keychain solar light can also be purchased separately on ebay but the best price I found was about $2. I find it rather interesting that you can buy the keychain with LIR2032 and solar panel and 3 LEDs for less than the battery by itself. Go figure.
Step 2: Projection Clock Modification
I tested the project clock as purchased. The first thing I did was lose the instruction sheet that came with it. I remember seeing it but then it disappeared. Spooky! Anyway, I was able to set the time and date and got it to work. I even tried it early one morning. The couple of times I tried it I apparently pushed the wrong button and it got into Set mode, so I gave up and went back to sleep.
There appears to be two or three versions of these projection clock key chains. I only have one type so can only tell you how I modified mine. The basic concept is to attach wires to where the main button goes to simulate a button push.
So I took off the battery cover and found a Phillips screw. (see picture, ignore the two white wires sticking out as I forgot to take a ‘before’ picture and this is an ‘after’ picture.
The clock has a top half and a bottom half. I took a utility knife and carefully pulled the two apart. They just snap together. (see picture). Again, this is an ‘after’ picture. The red top has a couple of pieces in it, a lens and a window aperture. They may fall out but you should be able to reassemble according to the picture. I removed the key ring.
Next I removed the little PC board assembly sitting in the bottom. This took a little maneuvering and prying to get it out. (see picture)
On the bottom of the PCB, you can see the three buttons. The one to the left is the ‘Light’ button. Basically, these buttons are just metal domes. The PCB has a circle that contacts the outer rim of the button and another contact in the middle of the circle. When the button is pushed, the circle is shorted to the center. So it was fairly easy to follow the outer ring but I had trouble figuring out where the center contact went.
Having worked with these before, there’s a piece of clear tape holding the button in place. I carefully lifted the tape until the metal dome was lifted and I could see where the center contact went. Then I put the button and tape back on.
There's not much room, so I used some 30 AWG wire wrap wire. One of the contacts went to the LED, so I soldered one wire to that side of the LED.
The other contact went to a little via(contact) that passed through to the other side of the PCB. I used an Xacto knife to carefully scrap away some of the solder mask exposing more of the copper. Then I soldered the other wire there.
Step 3: Projection Clock Modification, Part2
In actuality, I originally left the batteries in for my projection time clock then later took it apart to add the solar panel. If you’re doing the whole project, now is a better time to do this. One side of the PCB has a little spring that holds the batteries in. Connect another 30 AWG wire to the solder joint for the spring. The other contact for the batteries is a metal tab. Connect another wire to this metal tab in the housing where the white wire from the PCB is attached.
Carefully reinstall the PCB into the bottom case. There is a white wire going from the PCB to the case for one of the battery contacts. Mine broke off so I had to resolder it to the metal curved plate.
I took my Xacto to notch a V on both sides of the bottom so the wires can come out without getting smashed. You will have four wires coming out of case. (see picture) Try to keep track of the two wires that go to the battery terminals.
Now the top can be put back on. It might be easier to lay the top upside down and put the bottom piece on. There is a little projection screen on the PCB that has to go into a slot on the top. Get everything aligned and snap it together.
Now is a good time to test it. Put the batteries back in and push the 'Light' button. It should still project the time. If it looks fuzzy, the lens maybe backwards, If the time is cutoff, the little window aperture is probably upside down.
Step 4: Pushbutton Assembly
So I had a piece of a PCB with a pushbutton on it. You could also use some vector board or breadboard PCB. Locate the hinge so that the button will be pushed when the hinge is pushed. I drilled a couple of holes to mount the hinge. (see picture)
I also stuck the hinge in a vise and bent it so that the hinge would lie more parallel to the PCB. You don't have to do this, if pushing the hinge down will activate the pushbutton.
Next I attached the hinge to the PCB and also attached the binder clip as shown in the pictures. My camera shot looks a little distorted. The PCB is pretty much parallel to the binder clip. Make sure then metal of the clip doesn’t touch any of the circuits going to the push button. The same goes for the bolts. If a problem, you can cut the traces or insulate the metal parts.
On the other end of the binder clip, I took some 14 Awg house wiring and wrapped it around so that it was sticking up. The other end I bent it around the projection clock to hold it in place. The way I did it was to figure out where I wanted the bends, then held the wire with some needle nose pliers to make the bend.(see pictures). I also rotated the projection clock so that the time would be aligned with my reclining eyes. Since my head would be on the pillow, I oriented the clock so that it was vertical so it was easier to read. Try to keep the wire away from the buttons on the clock.(see picture)
Solder the two (push button) wires from the clock to the pushbutton. Test it by closing the hinge on the pushbutton. The time should be projected. Clip the clip to whatever is handy. I used my headboard bookcase. Adjust the copper support to display the time where you want it. I also put some electrical tape around hinge to keep it in place.
CAUTION: On these four pin pushbuttons, there is two of the pins on each side are connected together. So don't solder the wires to two pins that are already connected internally.
Step 5: Make It Perpetual
Well, I’m stretching a bit when I say perpetual. My solar panel receives power from room light so it’s not quite perpetual. If you stuck the solar panel in a window, then it would be closer to perpetual.
Open up one of the keychain solar lights. I used an Xacto knife and wedged it into the seam.
Solder two wires to the PCB where the battery is attached (see picture). I used a piece of two wire phone cable. This was a poor choice as the wire is very stiff and very hard to strip off the insulation. The wires broke off and I had to reattach and hot glued the wires to the PCB. But the cable was about 10 feet long.
The cover of the keychain solar light has a square plastic insert for the button. I took this out and ran the wires through the hole. I also removed the key chain and tie wrapped the wires to the tab for strain relief. (see picture)
By the way, the LEDs should still work by pushing the button.
Now you have two wires from the projection clock and two from the solar panel.
Strip a little insulation away from all four. Be careful that the wires don’t touch.
Using a DMM measure voltage across the two wires from the solar panel. It should read about 3 Volts. If it reads -3 V then switch the leads. Make note that the wire attached to the black lead is negative and the the red is positive.
If you still have the batteries in the projection clock then do the same procedure for the projection clock..
Remove the batteries from the projection clock.
Solder the negative wires together and insulate.
Solder the positive wires together and insulate.
Now, if you push the hinge button, it should project the clock powered from the solar panel battery.
Step 6: Conclusions
Now place the solar panel where it will get a lot of light during the day. Since my bedroom/work room is fairly dark, i have my bed lamp on most of the day so I put the solar panel under it.
I measured the current for the projection clock. It was about 90mA. The clock also requires a little bit of power to keep the correct time. The LIR2032 battery is rated at 35mAH. That would mean if the battery was fully charged, the projected time would last about 20 minutes. However, the way I use this at night, it’s only on about 2 seconds at a time.
So, theoretically, the battery should be kept charged enough to last in perpetuity, a perpetual time machine for less than $3.
Technobabble: Yes the solar panel is rated at 3.6V and the two batteries in the projection clock are 1.5V each. So I am theoretically applying 3.6V instead of the 3 volts needed. I am assuming there is enough tolerance to handle the higher voltage. So far it has worked fine.