Intro: Secret Book Light Switch
Several years ago I installed a strip of LED lights along the top of the bookcase in our living room. My initial thought was to use a simple switch to control these lights, but then my mind settled on something much more interesting - the magical book switch. I'm sure you're familiar with this switch. It's the one that opens secret rooms in countless stories. The switch is operated by pulling forward on top edge of a specific book on the bookshelf. In my case, the book would be controlling the LED lights instead of a secret door.
As I began to explore how others have created a book-controlled light switch, I quickly realized that the standard solution was to use a pull-string switch. The string from the switch is slipped between the pages of the book and is fastened to a metal bar, which slips into the spine of the book. When the book is tipped forward, the string is pulled - turning the switch on and off.
Then I found a much more elegant solution presented here on Instructables by the user Improbable Construct. In full disclosure, Improbable Construct's solution was so perfect that I have for the most part repeated it here - with one notable modification. This project should take most makers no more than several hours to complete and total cost as presented is around $35-$40 (in 2018). Enjoy!
Step 1: What You Need
This project requires the following supplies:
[x1] 1/16 x 3/4" (1.6 x 19 mm) aluminum bar.
[x4] #6 x 1/4" (6.4 mm) self-tapping sheet metal screws.
[x1] 3/4" (19 mm) wide brass hinge.
[x1] Lutron Credenza lamp dimmer.
This is can be replaced with an extension cord, but it is the most elegant way to make this.
[x2] Some short pieces of shrink tubing.
[x1] A roll of rubber tape.
3M Temflex 2155 Rubber Splicing Tape is a good example of this tape.
[x1] You'll also need a small zip tie.
Step 2: Select a Book
The first step is to find a good hardback book that you would like to use for the switch. This book will not be modified in any way so don't worry about permanently ruining it. We need to measure the depth of the book's pages before we make the switch. The book I selected measured almost exactly 6" (152 mm) from the binding to the edge of the pages. I added 1/4" (6.4 mm) to this length to arrive at 6.25" (159 mm). This will give us the bottom length of the frame we will be making.
Step 3: Marking the Aluminum
Next the aluminum bar is marked for bending and cutting. Beginning at one end, a mark is made at 6.5" (165 mm). A second mark was made 6.25" (159 mm) from this first mark. Note that this second length will vary based on the book measurement taken in the previous step. The third mark is 1/2" (12.7 mm) beyond the second mark and the fourth mark is again 1/2" (12.7 mm) beyond the third. A final mark is made 1.5" (38.1 mm) beyond the fourth mark. The aluminum bar is cut to length along this final mark. I used a hacksaw to cut the bar and cleaned up the cut end with a file.
Step 4: Bending the Aluminum
Bending this aluminum bar is probably the trickiest part of the entire build. I began by trying to bend the aluminum using my sheet metal vise-grips, but this did not create a straight, tight bend. Next I tried bending in a vise. Once again, I was less-than-pleased with the results.
Since I had previously made a sheet metal bending brake, I decided to use that. If you're wondering why I didn't start with this, it's because of the 1/2" (12.7 mm) bends that needed to be made. With the bending face of the brake at close to 2" (50.8 mm) tall, these bends would have been impossible. However, I realized that if I cut a small slot in the face of the brake, I could easily bend these tight bends.
I began by bending along the line 1.5" (38.1 mm) from the cut end. After bending this to 90°, the bent end was placed through the slot in the face of the brake and the first of the 1/2" (12.7 mm) bends was made to 90°. Flipping the aluminum, the second 1/2" (12.7 mm) bend was made to 90°. The final bend was made along the line at 6.5" (165 mm) from the opposite end of the bar. You can see the finished, bent frame in the image above.
Step 5: Drilling Holes in Frame
There are several holes, which need to be drilled in the newly-bent frame. First is the hole, which the switch passes through. This hole is drilled through the 1/2" (12.7 mm) wide surface around the bend from the 1.5" (38.1 mm) tab at the end of the frame. I drilled a 19/64" (7.5 mm) hole through this surface at a point 3/16" (4.8 mm) from the bend. Note that this hole is a little large for the Philmore switch and I would recommend using a smaller hole size.
Next two 5/32" (4 mm) holes were drilled in the end of the 1.5" (38.1 mm) tab as shown. These holes will be used for the zip tie used to secure the top of the switch assembly.
Finally, the 3/4" (19 mm) wide hinge was placed against the frame with its hole positions being marked as shown. Note that the barrel of the hinge should be positioned toward the hole for the switch. A 3/32" (2.4 mm) bit was used to drill the hinge holes.
Step 6: The Lever
As mentioned, I modified Improbable Construct's original design for this switch. When I first made the switch, I built it according to their specifications. However, I quickly found that the weight of my book was insufficient to reliably depress the switch. To fix this, I added a short lever beneath the switch. This lever does require that there are several inches behind the book on the shelf, but I believe this is pretty standard on most bookcases.
The lever is made from a 2.25" (57 mm) long piece cut from the 1/16" x 3/4" (1.6 x 19 mm) aluminum bar. Two 3/32" (4 mm) holes are drilled in the end of this lever for fastening to the hinge. I marked the position of these holes by sliding the barrel of the hinge up against the end of the lever.
The lever does need to be bent into a slight "S" shape in order to function properly. Since these were very slight bends, I simply used the sheet metal vise-grips, which did a nice job.
Step 7: Assemble Frame and Lever
With the frame and lever complete, the four self-taping screws were used to secure each end of the hinge to both components. The screws on the frame side of the hinge were trimmed flush using a cutoff disk as the book will lie over that portion of the frame.
Step 8: The Switch
Next we move onto the electrics. The switch used is a single pole double throw (SPDT) on-on push button switch. This switch has three terminals. Each of the side terminals are switched relative to the center terminal, with the connection switching each time the switch is depressed (See image). I found it was important for the switch to be of the on-on type as it needs to be closed when depressed. A typical latching, push button switch will be off when depressed and only close the connection when released. I used a Philmore #30-003 switch.
Step 9: Attaching the Outlet to the Switch
The Lutron lamp dimmer is unique because it uses a pass-through plug/outlet combo with a switchable wire protruding from its side. This switchable wire is originally controlled by the dimmer switch, but in our case we want to control it using the push button switch. The pass-through plug/outlet is nice because it can simply be placed between any power supply and switchable device. Note that the Lutron dimmer does run around $15 and we are discarding the dimmer, which makes this a quite expensive plug. Alternatively, you could use a standard extension cord, but the wiring would be a bit messier.
The first step was to cut the wire to the dimmer and discard the dimmer. Yea, I know that hurts. After stripping back the two cut wires, shrink tubing was placed over them and they were soldered to the center and one of the side terminals of the switch. It is important that these connections be completely covered by shrink tubing as there is 110V power from the house supply running through these connections and we want to avoid a short and/or someone accidentally touching them. After shrinking the shrink tubing, I wrapped the entire switch assembly with rubber tape to further protect it.
Step 10: Secure the Switch
Finally, the switch assembly was secured into the frame through the hole prepared for it. I further secured the wire-end of the switch using the small zip tie. This prevents the wires from pulling away from the switch if they are pulled.
In the image above, you can see that I wrapped portions of the frame and lever with rubber tape to both prevent the switch from scratching the bookshelf and to provide a grip at the front of the frame. This grip prevents slipping when the book is tipped.
Step 11: Attach to Book
With the switch assembly complete, the 6.5" (165 mm) long end of the frame was slipped into the bottom of the book's spine.
Step 12: Enjoy Your Covert Switch
If you've gotten this far, we have successfully created a covert book-activated switch. Although I use this switch for lighting, it could potentially be used to control anything you want. The pass-through plug/outlet makes this really easy as virtually any low-powered device (Less than 3A at 125V) can be switched using the book.
As for me, I've been using this switch for over two years and it's always great fun to ask guests to try and find the light switch.