BOW TIE PCB BADGE

Bow tie PCB Badge

The date of that big party is coming closer,and it is time to find the perfect accessories .Have you not found the right catchy bow tie ? here it is .A “BOW TIE PCB BADGE“.

PCB-Printed Circuit Board

wait …wait ….

I know Bow Tie ,But what is this Bow Tie PCB Badge?

As name suggests it is a PCB that can be used as a Bow Tie.A 3V CR2032 battery Powers this PCB Badge.

From where did you get this funny idea ………..

Printed circuit boards(PCBs)are literally all around us,nearly every consumer electronics goods contains a PCB.When I started Working on “LED MATRIX BADGE” I realized that you could make them “art” too ! This led to designing a wearable Bow tie PCB Badge.

This little tutorial will go through how I made this Bow Tie PCB badge that will make you to stand out in any crowd.

Lets get started…..

A Few Project Goals:

Implement the Circuit myself.
Design a PCB.

Prototype!

Using a cardboard sheet I made a prototype to decide the dimensions for the PCB.And I wanted the PCB design to be simple .So I connected 12 LED s in parallel to light up the badge through a slide switch.

Things used in this project:

Coin Cell Battery CR2032
CR2032 Battery Holder BS-7
Slide Switch – 11.6×4 mm
LED,1206 SMD Package -12
Brooch Base Holder Pins – This allows you to keep your badge on the Cloth.
Custom PCB : I designed a custom PCB for this project and got it manufactured by one of the leading PCB manufacturer called ALLPCB.com.
Tools : Tweezers , Soldering iron , Solder Wire , Wire Stripper and a multi meter for checking .

Schematics:

Note: Right click on image and ‘ open image in new tab ‘ for High Resolution Images.

When working with LEDs ,you’ll use parallel circuits very often .In addition to being able to turn on more components with less voltages.They are more durable.

In a series circuit ,if one LED gets damaged ,all of the LEDs will stop working.In a parallel circuit ,one broken LED won’t stop the others from lighting up !

CALCULATING CURRENT LIMITING RESISTOR VALUES FOR LED CIRCUITS:

SINGLE LEDS: When computing the value of a current limiting resistor for a single LED, the basic form of Ohm’s Law

V = IR , becomes:

where:

V_batt is the voltage across the resistor and the LED.
V_led is the forward voltage of the LED.
I_led is the forward current of the LED.

V_batt – V_led is the voltage drop across the resistor, and (I_led)²R is the power dissipated by the resistor.

LEDS IN SERIES:

When you connect multiple LEDs in series. The voltage drop across the LEDs increases, reducing the voltage drop across the resistor. The current through the resistor (and the LEDs) remains the same:

where n is the number of LEDs in series.

LEDS IN PARALLEL:

If you connect multiple LEDs in parallel, the current through the resistor increases (though the current through each LED remains the same). The voltage drop across the LEDs is unaffected, as is the voltage drop across the resistor:

where m is the number of LEDs in parallel.

You might be wondering why there is no current limiting resistor .Won’t the LED burn? my design uses an internal resistance of battery .the battery itself wont allow such higher current to burn the LEDs, Nasty trick 🙂

Actually In the schematics you will not find a current limiting resistor,But there is one – the battery ‘s internal resistance .There is a series resistor ,we just can’t see it !All cells and batteries have some internal resistance.We usually model batteries as an ideal,constant voltage source with a series resistance.

The board outline were made using Autodesk Fusion 360.

With the working prototype ,It’s time to put the schematics and PCB design into KiCAD and get an actual printed circuit board made .KiCAD has a neat feature that lets you preview your PCB in 3D. There are lots of great tutorials on how to use KiCAD.I started with shawn hymel’s excellent ” An introduction to KiCad ” you tube series,where he takes you through building an LED blinker PCB circuit in KiCAD from start to finish.

Once I was reasonably satisfied with the schematic and PCB design,I started placing a bunch of orders.

There are lot of really great manufacturing services out there. I’ve had great experience with ALLPCB .

Note:

On the PCB I have represented anode of led with a small white dotted silkscreen.