Introduction: Business Card Electronics
I am going to show you how to make some simple, solder-less inputs and an output using stuff you probably have sitting around between your workshop, the office and your car. This is a fun way to make a quick circuit when you have an idea and no real tools.
They require no soldering, and are perfect for bread-boarding.
They are easy enough to make that your favourite five year old can make them with you.
It is also an awesome way to up-cycle your useless or outdated business cards, and out geek your office mates.
I am only showing you a few simple ones to get you started, I hope you make even cooler ones on a boring lunch break.
Step 1: Gather Stuff
- a bunch of business cards (I used blank ones...that I cut myself out of cardstock)
- some foil tape. (in your garage, or car maybe, if not you can probably find some at the hardware store or maybe even the dollar store.)
- some ordinary white glue
- a pencil
To make the LED output you will also need:
- a 330 ohm resistor
- an LED
Step 2: Make a Button
I am going to show you how to make a single button, but you could easily make a multiple button input using the same techniques.
You will need four business cards for this one.
Start by folding two cards in half together and then cutting out a hole. I did a rectangle, but you do as you like.
Open them back up and put the cutout pieces to the side. The hole you just cut will be the location of your button, so use one as a template and quickly mark out the location on two sides of one of the remaining full cards, and one side of the other.
Place a strip of foil tape over the button location on each of the two full cards. Lay a prepared bit of wire (stripped at both ends) on the foil and place another piece of tape over it to hold it in place.
Glue each of the two cards with holes in them together with one of the button contacts. Sandwich them, in turn together making sure your wires are clear.
You can use one of the pieces that you cut out earlier to mark the button location (why we made the mark earlier), and write some clever text so you can remember what it is.
Step 3: Make a Touch Button
You will need two cards to make this one.
Start by cutting yourself a piece of tape roughly the same size as a card.
Draw out something similar to what I have done. The idea here is that you want to create two traces that are close enough together that a finger will bridge the distance between them when someone touches the pad. You also want the traces and connections to be away from the touch pad a little distance so they can be hidden in the final button.
Using an x-acto knife, carefully cut out the traces and apply them in as close to the same orientation as you drew them as you can manage to a blank card.
Make some connections using the tape technique, leaving your wires long enough to connect to a bread board later on.
Cut a circle in the position of the touch pad in the other card and then glue it into position on top of the first card. Write something meaningful on the card for identification and this input is ready to use.
Step 4: Make an On/Off Switch and a Pot
For the switch you will only need 3 cards.
Cut one card in half, and then in half again. Cut off a third of one of the two resulting strips.
Put some foil tape on one side of this small piece, enough to attach a wire using the same method as we used making our button.
Fold the other strip from earlier as shown in the photo and glue it on to the striker plate that we just made.
Next fold one of the remaining cards in half and make a slit-like rectangle in the center, around 1/4 of the total length (so it is about half the length when unfolded).
Unfold it and slide your switch activator up through the slit.
Put another strip of foil tape over to one side of the last card and attach another wire.
Sandwich the whole thing together with glue being careful to leave enough area for your switch to slide back and forth, and also leaving a small unglued gap so your switch wire can slide in and out a little too. Remember it is connected to the striker plate, so it slides a little.
Mark off the positions on the outside of the card.
You can use the same technique to build a potentiometer. Just scale back the size of the striker, and fill in a band with pencil scratching along the centre where the striker rides. You will want to put down the pencil before you tape to be sure that the tape has good contact. I had mediocre results with this, with a working pot in the 10 M range, it seemed jumpy. A softer pencil may have worked better.
Step 5: Make an LED Output
Using the same connecting techniques as the two business card inputs, it is easy enough to throw together small working outputs as well. As an example I made a simple LED carrier with on-board resistor.
Just poke the LED straight through one card and tape together the circuit on the back. Attach some connection wire(use different colours so you can tell positive from negative) and sandwich it to another card with some glue.
Step 6: Conclusion
That's it, now plug them into a breadboard and show the five year old who helped you make them how electricity flows through a circuit (explain what is happening when they press the button or flip the switch).
Or go out into the world and instead of doing whatever it is that you should be doing at your desk, make circuits. Just remember to bring some foil tape in your laptop bag.
Share and enjoy.
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