During the warm summer months, I've been amiss with keeping up with my Model Railroading hobby. But, with the beautiful weather we've had this year, I'm sure most will understand my choosing to be outside.

I have been able to dedicate the occasion hour or two towards miniaturizing Emergency Vehicle lighting systems. While I haven't quite achieved my 1:160 goal, I have accomplished 1:43. The model I chose for my O Scale endeavor was a simple $5 Ambulance toy I found at my LHS. I measured the toy and compared it to measurements I found online and, as near as I can estimate, the Ambulance is right at 1:43.

Starting with the code I used in my GT500 project, I was able to simplify and adapt it easily for use in an Ambulance model. I ordered and used 1206 and 0805 SMD LEDs. Before getting into details, here's the video:

//player.vimeo.com/video/76918961

1:43 Ambulance Model from claymore1977 on Vimeo.

Model Features

• 10 Red, 2 Amber, 1 White lights on the bar, all independently controlled.
• 2 headlamps, 2 Turn signals, independently controlled.
• 25 main bar flash patterns, 4 headlight/tailight patterns, but the chip has room for up to 180.

Original Toy. $5 from my LHS.

Disassembled Ambulance. Truly amazing how many parts are in a simple, cheap plastic toy.

Lightbar WIP build.

Final PCB. A MSP430G2553, a ULN2803 driver, LM-317 voltage regulator configured for 3.9 volts, and a pair of 2N3904 NPN transistors used as external Amps.

In lieu of paying for or creating a custom etched PCB, I used ribbon cable and prefab PCBs. Not pretty, but gets the job done.

Ambulance approximately 60% done. All electronics except the LEDs are still external at this point. That's why it looks like it's on Life Support.