A while back my kids got this SOS station toy, it came with a few emergency cars and the boys quite liked it. My girl friend and myself however; hated it, it had a speaker and made a high siren sound and an annoying voice would shout things like “all cars respond”. So I modified it; ripped out the speaker and mounted a few LEDs instead, so now it flashes but no sound.

Ripping out all of the original electronics
Ripping out all of the original electronics

Originally it had a blue light on the roof, a speaker and four buttons; pressing them would make a siren noise and a voice would start talking/yelling. And the blue light would blink for a few seconds. There was also a “walkie-talkie” thing connected to the speaker. Pretty annoying stuff.

Mounted new switch, and covered up the unused holes
Mounted new switch, and covered up the unused holes

I removed the electronics inside, the speaker, “walkie-talkie” and buttons, kept the blue light but replaced the light bulb with a self-flashing LED. I mounted two yellow LEDs in the roof over the “car port” area, also self-flashing. I plugged three of the four holes where the old buttons had been with rubber gaskets and mounted a toggle switch in the last one. This turns all the LEDs on and off.

Wiring up the new switch and LEDs, I'm reusing the battery holder
Wiring up the new switch and LEDs, I’m reusing the battery holder

I reused the battery holder, it fits 3 x AA batteries in series, which gives a voltage of 4.5 volts. This is a bit too much for the LEDs, so a few resistors were required. And that was pretty much it. It now flashes yellow and blue when turned on, and does not make any noise. Perfect :)

Soldering the yellow LEDs
Soldering the yellow LEDs
Blue LED, soldered and glued down
Blue LED, soldered and glued down

Here are the parts I used:

  • 1 × LED 5mm clear, flashing Blue, 3.0-3.4V, 20mA, 7000-8000mcd, 20°
  • 2 × LED 5mm clear, flashing Yellow, 1.8-2.2V, 20mA, 4000-5000mcd, 20°
  • 2 × LED holder 5mm, White plastic
  • 1 × Resistor, carbon film, 0.25W, 75 Ω, 5%
  • 2 × Resistor, carbon film, 0.25W, 150 Ω, 5%
  • 1 × Switch, toggle, 1-pole, micro, MTS-102, on-on, 6mm