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Open 7400 Competition / Modifications of write-ups after deadline
Thank you!
Nathan
Topics
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Topics - nato
Thank you!
Nathan
2
Open 7400 Competition / [Entry] Police Lights and Siren for Toy Car
Anybody know how to embed a video in a post? In the meantime, please check out the video here: http://http://www.youtube.com/watch?v=HMlVK92Vrgw
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Abstract
A Little Tikes Patrol Police Car was retrofitted with a battery-powered emergency police lights and siren system as an entry to the Dangerous Prototypes Open 7400 Logic Competition. The circuit design focuses on simplicity and efficiency of part utilization by using only two 7400 series integrated circuits. A 5-stage Johnson decade counter is used to modulate the frequency of the warbling siren and to drive two rotating beacons consisting of ten LEDs each. A hex inverter is used to rotate the beacons, drive the four strobe LEDs, and drive the siren's primary carrier tone. This report discusses the design, testing, modifications, construction, and reception of the project.
Introduction
My children have had a Little Tikes Police Car for some time now. The faux emergency light bar only has a reflective material under the red and blue lenses, but no lights. It has always seemed odd to me that a child's police car with a light bar wouldn't have lights in it. This needed to be fixed.
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Concept
I've always enjoyed tinkering with electronics, but unfortunately the tinkering is pretty low on my priority list. The Dangerous Prototypes Open 7400 Logic Competition offered an opportunity and excuse to make a project and actually complete it. Previous unfinished projects were a bit too ambitious for my schedule, so I figured a simpler circuit that focused on being minimalistic would have a better chance of being completed. The emergency police light for the Little Tikes car seemed like the right fit for this competition.
The solution first came to me over a year ago when I saw a back-and-forth Cylon/Knight Rider light that used an oscillator and a 4017 Johnson counter. The following schematic from http://http://http://www.evilmadscientist.com comes from an example circuit.
For the lights that are powered by two channels of the counter, each counter channel has a diode in series to allow independent driving of the same LED, while not over-driving the counter-channels by shorting them together. What if, instead, one were to use a single counter channel for each LED? You'd then have a string of lights. Then, arranging them into a circular pattern one could create a classical rotating police beacon lighting effect. This seemed like a good solution for the rotating police light.