What is it?

The heart badge is a simple interactive badge that is shaped like a heart and lights up when you tap it or move it sharply.

This version is a kit that beginners can assemble themselves.

Why did you make it?

I wanted to make the simplest possible circuit that did something interesting and interactive. I thought for a while and came up with this.

The vibration sensing circuit reacts to you organically, lighting up when moved suddenly or when tapped. It is never fully on or off and is always waiting to react to you. It consumes virtually zero power when left alone and does not need to be turned off.

Unlike other beginner kits this one is possible to be completely understood end-to-end by a beginner while also doing something somewhat interesting. It's not based on some complicated logic or pre-programmed microcontroller that somehow does whatever it does. It uses just one capacitor, resistor, transistor and switch, one of each of all of the most basic electronic components, demonstrating how they work.

Parts included

• PCB
• smidgen of double sided tape
• pin back
• 1x 1µF capacitor
• 1x 100kΩ resistor
• 1x BJT transistor
• 1x cylindrical spring switch
• coin cell battery holder
• CR2032 coin cell battery.

Tools needed to assemble

• Soldering iron
• Flush clipper tool

Assembly instructions

Components should go on the side of the board marked by their outlines in white. Eye protection should be worn while clipping excess leads, as they will often go flying when clipped

Resistor

Bend the leads and place through the holes on the board marked by the small white rectangle. The polarity (the direction in which it is oriented) does not matter. After placing, bend the leads on the opposite side out so it stays in place when the board is flipped.

Flip the board and solder. Clip the leads with flush cutters.

Capacitor

Next, the capacitor.

The capacitor is the small black cylinder with a white stripe along one side.

The white stripe marks the negative side of the capacitor. The lead on this side is also slightly shorter.

The negative side should face towards the center of the board. It should also be marked by a small minus sign near the negative side. So, the shorter lead should face the center of the board.

Slip the leads through the board and bend them out on the other side to hold it in place when the board is flipped over.

Flip the board and solder in place. Clip the leads when finished.

Transistor

Next, the transistor. The transistor has three leads and looks like a semi-circle when viewed from above.

The transistor must be placed so that its semi-circle shape matches the white semi-circular outline on the front of the board. The flat side should face the bottom of the heart shape and the circular side should be facing up.

You will have to bend the inner of the three leads out a bit for it to fit on the board. Place the transistor's leads through the board and bend them out on the opposite side so it stays in place when flipped. Then flip the board, solder in place, and clip the leads.

LED

The LED has a slightly flattened edge on one side (this can be a bit hard to see). This must line up the white outline on the front of the board, which is also flattened on one side. This marks the negative side of the LED. The lead on the negative side should also be shorter. The negative side should be facing the left side of the board from the front.

Place the LED through the board and bend the leads out on the opposite side. Solder and clip the leads.

Switch

Next lets attach the spring switch: it's the long black cylinder. It should have one thick lead and one very thin copper lead. The holes for the leads should reflect this, one being much smaller than the other. The leads should be bent at a right angle and it is meant to be placed such that it will seat in the rectangular cutout. The polarity does not actually matter electrically but it should only physically fit one way.

Gently slip the very thin wire through its hole and then the thicker hole. You may have to hold the cylinder in place with your finger or with tape so it stays in place. Solder the leads. The very thin copper wire will be a little challenging, but be careful. Clip the leads when finished.

Battery connector

The battery connector is a circular plastic holder with metal clips/leads. It should have one side that sticks out from the circle: this is the positive side of the connector and it must face towards the bottom of the board, matching the white outline for the battery connector.

You may have to hold the battery connector in place with your finger or with a smidge of tape so it stays in place as you solder. Be careful to touch only the plastic part and not the metal parts as you solder, as the metal parts will get extremely hot as you solder!

Place the battery connector and solder. Its leads have considerably more thermal mass than the other wires and will take a little longer to heat up. You can clip its leads a little bit after soldering, but they will go flying! Do not let the clipped bits fly into your eyes. Close your eyes, wear eye protection, cover the board completely with your hand, or clip it so its facing away from you into a garbage bag.

Next, snap the battery into the holder. The positive side (marked with a "+" symbol) must be facing upwards.

Flip the board and you should find that the LED glows in reaction to movement.

Pin back

The pin back comes with die-cut double-sided foam mounting tape pre-attached. Remove the film and place on the large white rectangle that matches its size. Press firmly into place.

That's it!