Firecrackers Improvements

22 Dec 2015

The Firecrackers (blog here and video here) that I made for Robin Hill Country Park on the Isle of Wight were good, but after I'd tried them out in real life on site, I knew there were some improvements I could make.

These included stringing the lights in one line, rather than going over the top of the path, improving the sound and increasing the amount of smoke.

Stringing the lights in one line is simple, and one I can leave to the Robin Hill staff when they next need the firecrackers. (The displays are changed regularly at the Park).

I got an improved sound file which gave a more realistic firecrackers noise.

I also simplified the NodeRED flow by taking out most of the delays and loops.

The amount of smoke produced by the hand held 12V fog machine I had used was great for indoors ...

but outside it got blown away too quickly. My next step was to adapt one of the larger mains powered fog machines used by the Park. These have to be permanently powered and the smoke output is controlled with a switch, so I could not power them through the relays. The hand held one was almost instantaneous - power on and smoke comes out.

Another thing I noticed on site was the Raspberry Pi GPIO pin that controlled the smoke machine triggered on bootup or reset of the pi - meaning I got a wash of smoke before anything else. I had thought I had worked out which pins were high on bootup, but obviously not.

After connecting LEDs to every pin and rebooting and starting the Pi from scratch, I made the following table - both Pi B+ and Pi2 gave the same results:

Pin Number	Powerup	Reboot	NodeRED deploy
3	Hi	Hi	Hi
5	Hi	Hi	Hi
7	Hi	Hi	Lo
8	Hi	Hi	Lo
10	Hi	Hi	Lo
11	Lo	Lo	Lo
12	Lo	Lo	Lo
13	Lo	Lo	Lo
15	Lo	Lo	Lo
16	Lo	Lo	Lo
18	Lo	Lo	Lo
19	Lo	Lo	Lo
21	Lo	Lo	Lo
22	Lo	Lo	Lo
23	Lo	Lo	Lo
24	Hi	Hi	Lo
26	Hi	Hi	Lo
29	Hi	Hi	Lo
31	Hi	Hi	Lo
32	Lo	Lo	Lo
33	Lo	Lo	Lo
35	Lo	Lo	Lo
37	Lo	Lo	Lo
38	Lo	Lo	Lo
39	Lo	Lo	Lo
40	Lo	Lo	Lo