Introduction: Tunnel Book Light With Dark Detecting Circuit and Solar-powered Battery

I wanted a light at the end of a long dark hallway in my house that would turn on by itself when it got dark, not need battery replacements, and be an interesting object to look at. I came up with a tunnel book silhouette of San Francisco with redwood trees framing the view. The idea of a tunnel book is modeled on "18th Century peep shows - images. These pre-television paper displays showed scenes, often of theater sets in one-point perspective.

There are several parts to this tunnel book light project:

1) Create the tunnel book part, mount it on a corrugated cardboard base, and insert the battery powered led lights. You can stop there, or continue on.

2) Add a dark-detecting circuit. I wanted a light that would come on by itself when it got dark, so added the dark detecting circuit.

3) Add a solar panel to recharge the battery.

Step 1: Materials and Tools

Materials and tools:

Tunnel book top:

-Card stock (I used green for the foreground, black for the middle, and yellow for the background)

-Laser cutter, or small scissors, or knife and cutting mat for cutting out artwork

-Skewer stick or bone folder to crease and help bend folds

-Glue stick

-Waste paper (about 2" x 8") and waxed paper strip for gluing


-Corrugated cardboard

-Stapler or brass fasteners

-Big scissors to cut out base

-Ruler and ball point pen to crease cardboard; use pen also to punch holes for lights in base


-A string of 5-10 led battery-powered party lights (Mine were from Dollar Tree, cost $1.00) IKEA has Sardal-12 lights

Dark Detecting circuit:

-3AA battery box

-breadboard, circuit board, wire 22 gauge, photocell, shrink tubing, 47 ohm resistor, potentiometer 10K ohm

-soldering iron if you choose

Solar Panel:

-1N914 blocking diode, shrink tubing, and solar panel

Jacks/plugs for each join in the circuit (3 sets)

I bought my supplies from my local electronics store, and online from Brown Dog Gadgets, Evil Mad Scientist,Mouser, and Digikey. The whole project cost about $20.

Step 2: Create the Tunnel Book - Print the Patterns From the Pdfs

Print the Patterns

Print the pattern pdfs and cut them out. There are two for San Francisco tunnel book which is the one shown in the Instructable. They can be printed on card stock and cut out, or printed on regular printer paper to then be used as patterns on colored heavy paper. There are also the blank patterns if you'd prefer to make your own design.

Step 3: Score and Fold the Flaps

Score and fold the flaps at the sides, roof and base flap. Score the fold lines with the ruler and skewer or bone folder, then while holding the ruler in place still, slip the tool underneath the flap and use it to help bring the flap up to crease. This makes a neat, precise fold. The side folds on the middle and front bend backward and the side folds on the back piece bend forward.

Step 4: Glue the Yellow Back to the Black Middle

Glue the yellow back to the black middle

The left side will be glued first. Position the yellow back piece on your work surface with the left side flap folded forward. Slip waste paper under this side flap, glue it, remove the waste paper and slip a strip of waxed paper under it to protect from excess glue in the wrong place. Position the middle black piece on top, aligning the bottom edge. Weight it til dry. I used the stapler for that. Turn it over and glue the other side.

Step 5: Add the Green Front

Glue the green front on

To glue the front on, start at the left again. Have the base/middle lying face down flat with the left side exposed and the right side folded underneath. Using a strip of waste paper to protect the rest, glue just the side of the middle. Put a strip of waxed paper in place, and position the front. Weight til dry. Do the right side.

At this point you have a tunnel book that you could fold flat.

Step 6: Fold in the Top Flap

Fold in the top flap. This gives the tunnel book structure.

Step 7: Make the Base

Make the base out of corrugated cardboard. The pattern is in Step 2..

Step 8: Add the Lights

Center the tunnel book on top of your platform, and lightly mark in pencil where the corners are. Also mark if there are any places in particular that you want one of the leds to go, for instance, if you have a tall item like a tree towards the center, you might like to locate one of the lights there. The lights can be at different heights, not just at the bottom. Some lights can be between the front and middle panel, and some between the middle and back. Remove the tunnel book and punch small holes for the leds with a ball point pen.

Now take your string of lights and push the leds up from inside the base. Adjust the heights. Use a bit of tape to hold them in place if you need. Tape can also keep the wires underneath tidy. I have the back lights higher. Set the tunnel book on top of the base. If all looks good, glue the front flap onto the base. Alternatively if you want to make other tops to use on this base, leave it unglued, or just lightly tape it in place. The battery pack can be placed behind the base.

Congratulations. You've completed the first part of this project. You can stop here, or continue on to add:

- a dark-detecting circuit that will make it turn on by itself

- a solar panel to keep the batteries charged

Step 9: Add the Dark Detecting Circuit

This circuit makes the lights turn on when it gets dark. This circuit uses energy, so you need to add an extra AA battery to your battery or the leds may not have the minimum voltage to light up (usually 3.2v for white leds).(You also don't want to exceed the maximum or they will burn out rapidly)

This works when made on a breadboard without soldering, but for long-term use I'd recommend soldering it on to a circuit board.


Potentiometer - a dial that lets you adjust how dark it needs to be to turn on the circuit.10K Ohm, Digikey Thumbwheel Cerm St. 3352T 103LF-nd

Resistor 47ohm

Transistor 2N 4401

Photo-cell (electronics store)

Switch so that if it's dark and you want to turn it off for the night, you can (Miniature slide switch, Philmore) electronics store

Circuit board or bread board. Mine is 1-3/4" x 1-1/2"

Wire to join it in the circuit. Mine is 22 gauge.


Heat shrink tubing

Solder tool and solder

Wood and screws to mount it if you like

I made this circuit on a white" breadboard" first which has connectors on the back so you don't need to solder things. It's great for trying out circuits that you're constructing. You can stay with that, or make a permanent version soldered on a brown circuit board. The Instructables electronics class explains how to use them.

To put it together I laid out my components and the diagram and start placing the components. I used a multimeter to measure ohms to be sure parts are joined the right way. I started at the positive battery terminal and proceeded from there. For each component, I clarified in my mind what each end was attached to, then placed it in position.

1) On the breadboard, I started with the red positive wire that comes from the battery box, then added the switch, using an end and middle prong.

2) After the switch came the potentiometer. Again, i used an end and a middle prong. I soldered wires to them to make them easier to use on the breadboard. One prong goes in the same row as the last component, the other moves on to a new row.

3) After the pot came the transistor, paying attention to B-C-E labels.

4) One end of the resistor goes into the same row as the pot and switch, and the other end goes in the same row as the C of the transistor.

5) The E of the transistor is attached to the positive that goes to the leds in the diagram, so that's the row I put the red positive wire for the leds.

6) The photocell goes between the base/pot row and a new row.

7) I'll also put the negative wire from the leds in that same row.

8) In the same row, add the black negative wire that goes to the battery box.

9) Connect the battery and leds, turn the battery on and the switch on, and adjust the potentiometer so the circuit turns on at the level of darkness you like. Observe what happens if you put your thumb on the photo cell. Try aiming the photocell in different directions - that affects the light exposure.

Step 10: Other Versions of the Same Dark Detecting Circuit

Once I got the basic circuit working, I had fun making other versions. You can put all the components neatly on the circuit board close to the surface - or play with it. On these versions, I extended the wires, and or divided the resistor into two resistors purely for artistic reasons. It's still a totally functional circuit. To make it clear how everything was connected on the circuit board, I used white wires on the bottom and marked them with colored markers to correspond to similar markings on my circuit diagram.

Step 11: Adding Plugs to the Battery Box

You could just wire the whole circuit together, but I find it useful to be able to disconnect parts easily.

Why I change the battery box:

-There's a voltage drop across the dark detecting circuit of about .7v.

-The white leds need 3.2v to light up, 3.2+.7 =3.9v.

-AAs are 1.5v, so 3AA = 3 x 1.5v=4.5v. Rechargeable batteries are slightly less. (4AA are 1.5v x 4 = 6v which is too high for the leds.)

-The lights I got came with a 2 AA battery box which provides 2 x 1.5v. = 3.0v, not enough, so I'm replacing it with a 3AA battery box.


-Wire - red and black makes it easy to keep track of + and -. you can use red and black wire, or use white wire and mark one with red marker to help you keep track.

-Plugs (Both our sets of wires will end in plugs)

-Soldering iron and solder

1) In the 3AA battery box, locate + and - terminals. Follow the wire from the spring-like negative end of battery holder to the small circuit board. That's the negative terminal. The positive terminal is the other terminal. There is the set of wires currently coming out of the box from the printed circuit. If yours are long enough, you can just add the plug. Mine aren't, so I'll remove them and add new wires that I've already attached a plug to.(Your circuit board may not look exactly like this one, which includes an ability to flash. You may not have a circuit in your battery box at all.)

2) Unsolder the wires by holding the tip of the hot soldering iron on the blob of solder that attaches the wire. It will soften and melt, at which point you can lift off the wire and pull it out of the battery box. In the photo, the upper of the two blobs is the negative one. You can tell this because it is on the same lighter green part of the printed circuit as the wire that snakes around the side of the box to the negative end of the batteries. I've already attached the plug to these wires, and covered the joins with heat shrink tubing. I'm keeping track of positive and negative. I've fed the ends through the hole in the battery box and used a piece of masking tape as a clamp to hold the end of the wire in place while I solder it. I've labelled this set of wires "To Light".

3) I'll add another set of wires which will go to the solar panel. They'll attach directly to the battery terminals, skipping the rest of the circuit. I don't want to remove any more of the wires already there. I've put red marker on the positive wire, and fed it through to the positive end of the batteries. The negative wire will be soldered on on top of the pre-existing wire that goes to the negative end of the batteries. I've labelled this set of wires "To Solar Panels."

Step 12: Add Solar Panel

I added a solar panel to charge the batteries.

I learned that in the Instructable "$4 Solar Battery Charger" by Brown Dog Gadgets.

There's a great class on how to solder as part of the Instructables Electronics class. If you don't know how already, it's worth learning. It's easy, the supplies don't cost much, and it opens new doors as to what you can build.

My solar panel is 4.5v, 1W, 220mA. I've soldered a 1N914 blocking diode to the wire coming from the positive terminal. The black end of the diode is away from the panel, towards the battery. It's covered with heat shrink tubing. It keeps power in the battery from flowing back into the solar panel at night.

I attached a jack to the wires so I can disconnect it easily if I want.

Step 13: Adding Jacks/Plugs

I connect my parts with jacks/plugs so that I can take them apart if I want. I can unplug the batteries of something that's not near a solar panel and charge it up in the sun without having to take the whole structure with me.

The jack I use is DC Coaxial Jack by Philmore, 2.5mm pin x 5.5 mm ID (No. 258). Solder the center pin to the red positive wire, and the outer edge to the black wire.

The plug attaches to the battery.(DC Coaxial Plug 2.5mm x 5.5mm No. 250). Here I've used the same color wire for + and - but I've been careful keep track of which one is which.

Step 14: The Whole Set Up

Thank you for reading this Instructable. I hope you'll enjoy making it and send a picture of what you do. I'll do my best to answer any questions.

Step 15: This Is Another One I Made.

Lights Contest 2017

Participated in the
Lights Contest 2017