Toy car fitted with lights and sirens is a children’s delight


[Nathan], a member of the DangerousPrototypes forums, was looking for a project he could use to enter the 7400 logic competition they are holding. His kids had a small ride on police car, but the light bar on top contained no lights, and the car made no sounds when his children were in pursuit of baddies around the house. [Nathan] had all the inspiration he needed, and took to his workshop in order to fix this glaring oversight by the toys’ creators.

He designed a circuit based loosely around a Cylon-style light that he saw a while back at the Evil Mad Scientist Labs, which employed an oscillator and a 4107 decade counter to control the lights. His design uses a 74HC04 hex inverter as the oscillator, while the decade counter is used to modulate the siren’s frequency and control the rotating LED beacons.

The final result is great if you ask us. An “unnamed adult female” in the house was not nearly as impressed by the additions based upon how much time [Nathan] spent on the project, but his children were absolutely thrilled.

Continue reading to see a quick video of the revamped police car in action.


  1. That’s a slick build. Lucky kids! :)

  2. anguish says:

    That is awesome!

  3. The Timmy says:

    the 4107 is a PLL Frequency Synthesizer
    (datasheet here: )

    the 4017 is the decade counter — that’s actually the first IC I started working with, along side the 555, back in my xbox casemodding days.

    all that aside, I love this project. growing up my dad and I would always come up with ways to “improve” my toys that seemed to be lacking appropriately (and sometimes inappropriately) placed LEDs.

  4. Oliver says:

    he will soon regret this project, I guarantee it. Giving your child the ability to make more noise is not the best way to a happy family home.

  5. Paul Potter says:

    Great modification.

  6. meatman says:

    it needs to be louder, a lot louder.. and brighter. something that after 3 minutes will turn all adults into crazed people hell bent on making it stop is just right.

  7. KillerBug says:

    There are book smarts…like the kind needed to make a siren using a 7400.

    …and there are street smarts, like the kind needed to avoid giving sirens to children.

    I actually had to read the article a few times…I didn’t actually think anyone would willingly and intentionally MAKE a siren for their children. Even if this wins the 7400 competition, I still think it was a bad idea.

  8. Kendall says:

    I might do something like this when my son’s old enough for one(next summer). I would add a way to remotely disable the siren and other sfx.

  9. Hirudinea says:

    “Ma’am, do you know how fast you were going?”

    “I was just walking the hall.”

    “Please blow into this ma’am.”

    “That’s a juice box.”

    “Don’t make me taze you ma’am.”

  10. charliex says:

    Is this even street legal ?

  11. jimbob says:

    Awesome! I was thinking about adding headlights and a horn to my son’s similar, non-light bar equipped car. This gives me the motivation to get off the couch and get building.

  12. dbear says:

    As a parent this would be an appalling thing to have in your home.

    As a grandparent, aunt or uncle it is the perfect revenge tool. It does need to be solar powered though.

  13. Dan Fruzzetti says:

    To the original modder: EXCELLENT WORK! I am absolutely stunned at it. You did something really special for your child; you should celebrate. If you search ‘improving a motorized toy’ on this site you’ll find my stab at a similar job — the kids love it just the same!

    • Dan Fruzzetti says:

      PS – This excites me as my wife was really happy with how the car came out. I hope your own spouse can accept that a little modding time, especially when geeklings can watch and learn, is priceless.

      How much value will your children get out of seeing Dad working with soldering irons and electronics, modifying an existing product to do more of what he wants? It’s priceless to pass these skills on to your kids.

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