My two twin boys are pretty into Fireman Sam these days, so the red walking car they got when they were babies got an upgrade. Four blue self-flashing LEDs, a toggle switch and a 2xAA battery holder; everything bought cheap on eBay. And voila! A fire truck with blue emergency lights.
Initially I wasn’t sure that it would last long, they they might try to pull on the cables or that the battery holder under the seat would break. They do stuff all kinds of things in that storage compartment under the seat. But no problems, they seem to be fairy careful with it.
The AA batteries are 1.5 volts, and with two of them in serial; that makes 3 volts. Which is what the blue flashing LEDs uses, so no resistors required.
They provide the siren sound themselves, yelling wi-wu-wi-wu while racing from fire to fire. It was a very inexpensive, quick and easy build, and has given the boys much joy :)
These are the parts I used:
- 1 ea × Battery holder, 2xAA, with wire
- 4 ea × LED 5mm clear, flashing Blue, 3.0-3.4V, 20mA, 7000-8000mcd, 20°
- 4 ea × LED holder 5mm, Chromed metal
- 1 ea × Switch, toggle, 1-pole, micro, MTS-102, on-on, 6mm
- 1.8 m × Wire, stranded, 2-cores, 0.13mm2 (26 AWG), Red/Black