Friday, 7 December 2012

Remote Controlled Eight-Relay Board


- An RC Firework Firing Device

I am making a remote control (RC) device. It allows me to independently switch eight relays and control various  items. When I press buttons on a small keypad, instructions will be decoded and transmitted via a microwave RF packet transceiver (@868 MHz). At the other end (up to 100m away!)  another transceiver decodes the message and switches the relays ON or OFF. 

For my first application, I am using the main components described in Parts I to III, to construct an RC firework firing device. Here's a quick re-cap of relevant posts.

Part I - Analogue Keypad as Input device The remote control incorporates a small inexpensive analogue keypad, connected to an Arduino Uno. The Arduino handles the scanning and decoding of the keys pressed on the pad.

Part II - Using the RF12 Board by JeeLabs. I'm using a pair of RF12 modules on boards by Jeelabs, connected to Arduinos.  These enable data sharing among common network groupings. I am just using them for RC, although they are capable of much more.

Part III - Eight Relay Module.  I am using a relay module to provide power some firework igniters. It's an optically isolated 8-relay module, again controlled by an Arduino. The igniters are by Talon. See link for a demonstration of how they work.

Firing a firework.
When I press a number 1 to 7 on the keypad It should send a data-packet over RF, and trigger one of the relays (1-7). This will supply sufficient power to take the Talon igniter up to white heat and light the firework's fuse.

When setting off fireworks, safety is a major consideration, so I want to incorporate some safety features into my device. I started by thinking about a Safe Operating Procedure (SOP) which would guide the development of the physical device and the code.

 These are some ideas that came to mind:
  •  A standardised sequence of actions to wire the igniters, connect them to fireworks, power devices and arm devices.
  • Key switch
  • Missile switch cover  
  • Visible and audible power / arming indicators.
  • PIN number to protect keypad entry

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