LED Juggling Knives
Introduction: LED Juggling Knives
This project was inspired by one of my friends, who is an avid juggler. He was looking for glow in the dark juggling balls and I wanted to try my hand in building it. As I worked through the design I realised that it would be much easier to build knives instead of juggling balls and I moved forward with that. With my knowledge of the 4017 IC, I decided to add a bit of flourish to the lights, which are now in the form of LEDs, and that is how I ultimately ended up with this project.
A set of juggling knives that can be also used in the dark for better visuals.
The LEDs are lit in a sequence, just like a led chaser. This is done by a 555 timer circuit in Astable mode combined with a 4017IC. The housing is relatively simple, and it was 3D printed.
This is a relatively challenging project to build with a lot of components required.
Supplies
Note: The following supply list covers the making of 3 juggling knives, as all juggling knives usually come in sets of three. If you want to build only 1, you can divide the quantity by 3.
Circuitry BOM:
1) 3 x NE555 IC + 8 pin IC holder (link)
2) 6 x IN4007 Diodes (link)
3) 3 x 4.7k Ohm resistor (link)
4) 3 x 3.3k Ohm resistor (link)
5) 3 x 4.7uF 10V electrolytic capacitor (link)
6) 3 x 40mm by 50mm Perf Board. (Any size bigger than this is fine. You can trim it down later) (link)
7) 2 x Male to Male Jumper Cable 40pcs. (link)
8) 3 x 4017 IC + 16 pin IC holder (link)
9) 3 x 10k Ohm resistor (link)
10) 25 x 5mm LEDs in Red colour (5 are extra just in case) (link)
11) 25 x 5mm LEDs in Blue colour (5 are extra just in case) (link)
12) 25 x 5mm LEDs in Yellow colour (5 are extra just in case) (link)
13) 3 x 9V Battery + connecting clips (link)
14) 12 x 3mm Dia 20mm long bolts (link)
15) 3 x 3mm Dia 6mm long bolts (link)
16) 3 x Tactile latch switch (link)
Tools and Equipment:
1) Soldering Iron + Soldering wire
2) Desoldering pump
3) Pliers
4) Wire cutters + Wire Strippers
5) 3D printer or access to a 3D printing service provider
Step 1: Understanding the Circuit (555 Timer)
There are two parts of this circuit. 555 timer and 4017 IC. I will be exploring the former in this step. You can ignore this step if you are familiar with the 555 astable circuit.
555 timer circuit
This circuit is a very common favourite of all electronics geeks. The schematic for the circuit can be seen in the first image. 982
Here is a link to the website where I got the circuit image from https://www.electronics-tutorials.ws/waveforms/555...
For this project, the circuit is wired up in an astable configuration. This means that the voltage output of the chip alternates between high and low at a constant frequency. The voltage output vs time graph of this circuit can be also seen in the image.
It is a square wave. Essentially the circuit produces pulses at a constant rate. This can be used to make an LED blink. The frequency of the pulse can be controlled used the values of the two resistors and the capacitor. These are respectively R1, R2, and C1 in the image. The equation used to calculate the frequency from these values has been given in the equation.
The final term is the duty cycle. It is the percentage of time for which the output is high. This can be also calculated with the equation in the image. Unfortunately, if the duty cycle is too high it leads to bouncing (link) or the connecting circuit can't even detect the pulse/low period.
To rectify this issue, this circuit has an additional 2 diodes compared to the conventional circuit. This is to make the duty cycle more even 50%-50% between on and off. (link)
Step 2: Understanding the Circuit (4017 IC)
The 4017 IC works with the 555 timers.
The 4017 IC has multiple output pins: pins 1-7, 9, 10, and 11. Each of these output pins is set in a sequence as shown in the image. 552