Electronic Party Wear Pendant

I always love making wearable electronic art and in this instructable we will see how to make led pendant which discos over minimal fundamental components.

The idea is to keep it as small as possible so definitely we need to use SMD components.

Having a disco light I don’t mean a fancy RGB light but simple mono color LEDs which will blink with a fading effect.

To make the LEDs blink we need a circuit which will have the capabilities to do so, many circuits are available on internet like a astable oscillator with 555 timer IC but I preferred to go with the simplest and most fundamental oscillator using two transistors two capacitors and four resistors with other complimentary components.

To understand how the oscillator works you can check this.

The 1st schematic picture shows the oscillator but we cannot use it cause there is no way we can make a led oscillate using it, so we need some complementary components (2nd picture). If you are keen enough to test the circuit on breadboard you will notice that led blinks and if we consider its waveform it will be a square one, but we need a waveform, more of a sinusoidal form providing a fading effect this can be achieved using a capacitor (3rd picture)

To give a more techy looks the frequency of blinking should be around 1.5 Hz which is the frequency of heart beat of normal human being

I referred the same to find the values of resistors and capacitors and so you can.

Electronics components

• CR2032 button cell x 1
• Yellow SMD led 1206 package x 8
• 47uF electrolytic cap x 1
• 1K 1206 x 7
• 1M 0805 x 2
• 150ohm 1206 x 2
• Bc547 SMD package 1F x 2
• 0.47uF multi layer cap 1206 x 2

Actually we require around 3K in one section of circuit but it was not sourced locally in my area so instead I used 3 x 1K in series you can use 3.3 K instead if you get it or even do the same as I did.

Materials

• Male headers x 4
• Fancy chain to put it around your neck x 1
• SMD holder x 1
• Zero PCB / perf board x 1
• Single strand wire x 50cm
• Multi strand wire x 10 cm

Tools

• Solder iron
• Solder
• Wire stripper
• Sand paper

• First layer will be the power house.
• Cut the zero PCB into 10 x 7 holes.
• Solder SMD button cell holder in horizontal direction making sure it is at top of the PCB.
• Solder two male jumpers at bottom left corner from button cell holder.
• Strip of some insulation from multi strand wire and insert it up trough one hole of zero PCB.
• And solder other end to 2nd jumper.
• So now we have our power house PCB ready.
• You can refer the PCB diagram for soldering provided above.

• The 2nd layer will be the functional layer the one who is going to create the required waveform.
• The process is very straight forward.
• I have provided a picture of how you can solder them.
• As resistors and capacitors don’t have orientation no need to worry about it.
• Do keep in mind the polarity of electrolytic capacitor while soldering.

• Last layer will be the led layer.
• Eight LEDs will be attached in parallel.
• 1st cut out a 10 by 10 piece of zero board.
• Snip of corners of about 3 by 3.
• Sand the corners.
• PCB will have a octagonal shape.
• Solder the LEDs with proper orientation according to the picture.
• Connect all LEDs to parallel using single strand wire according to picture.
• Solder male jumpers connect +ve of LEDs to +ve of headers and –ve of LEDs to –ve of headers.
• Connect all three layers by inserting headers into respective holes and then solder them.
• Everything needed to make the LEDs blink is done if you insert the button cell in the holder it will start to blink but to complete the build we need to add a chain so that we can hock it over neck.

• There is no need that you should have the same chain as I got but make sure that it has some sort of thing so that you can hock up into a small ring.
• Remove insulation of single strand wire cut around 1 cm in length and bend it into circular form.
• Insert it into one corner hole of 2nd layer PCB and solder the joint.
• Do same for other corner which is diagonally opposite to previous one.
• Now you can attach the chain to the rings and wear it.

Insert the cell, hock up the chain around the neck and enjoy the blinking.

In version 2 I will try to accomplish using circuit sculpture.