Interactive Confetti Room Project

I was recently asked to help develop the electronics for an event.  The basic idea is that people would enter a room filled with different coloured confetti and air blowers.  These air blowers would be energised for short periods of time in prescribed sequences blowing the confetti about the room in a colourful display.  Hopefully a little bit reminiscent of a final game in a classic British TV program - the Crystal Maze!  If people aren't aware of the cult classic of the crystal maze then a link is below:

https://en.wikipedia.org/wiki/The_Crystal_Maze

The part I'm referring to is this, don't watch all of it! - skip to 2:17 for the important bit:

Hopefully people reading this post will get what I mean.  Anyway...in order to create a similar effect Five air blower units will be sourced and placed inside a 15 m² room.  The fan units will be placed in the corners with one unit in the mid point in effort to ensure there is some form of uniform airflow.  The coloured confetti is placed in front of the fan units and when people enter the room and the door is closed the fans will come on in a prescribed sequence creating an atmospheric effect.  This hasn't been tried and tested yet so some development of the experience may be required...I'll probably leave that part to others as I haven't the time and to be honest I have only been asked to help develop the kit not the experience...I'll help out where I can but getting the desired effect is up to the customer...I'll provide the tools not the results...

The above diagram hopefully gets the general idea across.

The fan blower units have already been selected and are linked below:

Vacmaster Air Mover via Amazon.co.uk

Image Credit - Vacmaster, via Amazon.co.uk

The specifications given via the Amazon product page are:

• POWERFUL AIR FLOW - The 150 W motor drives 266 litres of ambient air per second for rapid drying and cooling.
• ENERGY EFFICIENT - Consumes 90% less power than a conventional 1000 W fan heater.
• 3 TILT POSITIONS - Tilts at 45 degrees, horizontally and vertically for precise, focused air flow.
• 3 POWER SETTINGS - Low, medium and high speed settings for quiet or fast drying.
• INTEGRATED EXTENSION SOCKET - For powering additional Air Movers from a single wall socket. Daisy-chain them together to cover a large area.

The vendor doesn't mention the mains supply voltage required but as this is the UK and it's being sourced via amazon UK I'm going to assume the supply is 230 Vac.  The current draw will therefore be 0.65 Amps - as Current (Amps) = Power (Watts) / Volts from Ohms Law:

150 Watts / 230 Vac = 0.6521739130434782608695652173913‬ Amps
or 0.65 Amps to two significant figures...

Lets write some requirements:

• Switch five fans on and off independently in a pre-arranged sequence
• Choose specific times of day when fans will come on and off
• Ensure fans can only actuate when the door to the room is closed.
• Ensure fans have independent overrides for safety - be able to turn fans on/off via control buttons
• The switching requirement is 230 Vac at 0.65 Amps for each fan 

There are several ways this could be achieved.  As time is of the essence...as it always seems to be, I'm going to use relays to switch the mains feed to the fans.  The relays will be controlled via a microcontroller which can be communicated with using a serial terminal or via the buttons which will be on the front panel of the control unit.  If necessary I'll add an indication LED and maybe a buzzer to show when the fans are about to begin operation...I suspect the fan noise will make that clear to all concerned though - 😃

I could design my own relay control PCB complete with drive electronics or I could make use of a pre-made module...again time and budget suggests I go with something off the shelf.  I need a five channel relay module capable of switching 230 Vac at 0.65 Amps. I found this module on Amazon.co.uk and it looks to have everything needed...that'll save some time!

Elegoo 8 Channel Relay Module - via Amazon.co.uk

Image Credit - Elegoo 8 channel Relay Module via Amazon.co.uk

There are eight relays are capable of switching 230 Vac at 10 Amps - far more than we need and they meet the switching requirements.  They can be driven from 5 Vdc which means that they can be driven from a five volt tolerant microcontroller output.  The relay drive coils are optically isolated so the microcontroller won't be affected by the relay switching.  There is an LED (light emitting diode) at each relay channel to display when the relay coil is being driven.  The cost was a very reasonable GBP £8.99 or USD $11.31 which I would struggle to compete with if I were to design my own version.

The schematic diagram for the relay module is here in case it is needed:

We will also need the following components:

An arduino uno R3 microcontroller or clone - Via Amazon.co.uk
Some Momentary Buttons  - via Amazon.co.uk
Some jumper wires - via Amazon.co.uk
Some tri-colour LEDS - via Amazon.co.uk
Some LED holders - via Amazon.co.uk
Six mains sockets and wire - via Amazon.co.uk
Some connector block - via Amazon.co.uk
A reed switch and magnet - via Amazon.co.uk
A power supply for the Arduino - via Amazon.co.uk

The current plan (always subject to change) is to connect all the above components as follows:

Please excuse the crudeness of the diagram...I didn't have time to sort everything as much as I would have liked but it gets the general idea across...I've missed off the power supply to the arduino.  It is also connected to the incoming mains and then to the dc input socket on the arduino.  Not all of the relays need to be controlled by the arduino so some of the wires can be omitted as necessary and finally the reed switch should have a 10 k resistor pulling it down to 0 Vdc as with the buttons so that it is properly detected by the microcontroller input.

That's enough for now.  The next post will be on testing and using the Elegoo 8 channel relay module.

Take care, especially with mains wiring - Langster!