Sunday, 9 December 2012

Remote Controlled Eight-Relay Board


- An RC Firework Firing Device

Relay-Side Transceiver

Outside view

Opened up and expanded

The Relay-Side: Making the Connections and Code 

 Wiring the Relays and Igniters

I wired the relay module according to the diagram above. Relays 1 - 7 are wired identically, whereas relay 8 is wired to provide 12v power to the igniters, when activated, and is switched to the igniters by relays 1 - 7. A white 12v LED strip is connected accross the 12v battery to show the battery is connected and provide some safety lighting. Ribbon cables and barrier terminals were convenient for this purpose.

I'm using a 12v lead-acid battery (12Ah, peak max current 75A) to supply power to the igniters. Each igniter draws 0.5A momentarily, so there's plenty to spare.

NB although relays 1-7 can be triggered, no power is provided to the igniters unless relay 8 is active and is connecting the 12v supply.

Connecting Relay Module pins to Arduino

The Arduino and relay modules are connected according to the above diagram (see code also).

Safety Features

Safety Features on the Relay Side 
I wanted these safety features
  1. Safety / Task lighting
  2. Key Switch
  3. Audible alarm
  4. Relays Ready LED
  • Safety / Task lighting => a white 12v LED strip that comes on when the 12v battery for the igniters is connected. Shows / warns igniter power is live and provides task light.
  • Buzzer => sounds when arduino power is connected [arduino PIN15]. Buzzer can also be sounded as a "fire in the hole" warning by pressing character '*' on the control-side keypad.
  • Key Switch => when the key is turned clockwise, the circuit is completed for the relay-trigger grounds and a red LED shows this [arduino PIN16]
NB The relay-side is ready to fire the talon igniters when the white led strip is on, and a red LED is showing on the relay-side box. It is now sending a "relays-ready" signal over RF and just waiting for commands from the control-side via the keypad on the hand-held device.

 Here is the relay-side Arduino code: Relay-side.

 Useful peer comments on Hackaday


  1. This site is great and the info you have provided is awesome. I'm building a fireworks controller for the 4th. The link for the relay-side and the link for the hand-held go to the same code download. Is this correct?

  2. This comment has been removed by the author.

  3. Hi techpopulace. Thanks for the +ve feedback. It's so useful when people like yourself read the blog in detail. That link should be fixed now. Good luck with the 4th July fireworks. Let me know if you have any more probs and I'll help if I can. Useful peer comments here also: