7400 competition entry: CMOS car alarm

Don’t wanna lose your car? Build a CMOS 4000 series car alarm¬†and enter it in the open 7400 competition.

Built way back in the 1980s this CMOS Car Alarm provided an entry & exit alarm for my wonderful little Mini. It was built from CMOS series logic to reduce the current consumption and the circuit only drew 20mA with both LEDs lit! I particularly like the oscillator design and the fact you don’t need any current limiting on the LEDs as the CMOS logic self-limits. Enjoy!

Build something that uses or abuses a logic chip and get amazing boards, tools, and other swag. The Open 7400 Logic Competition promotes awareness of the basic building blocks of modern circuits. Devious geeks ignited the computer revolution with discrete logic computers, what can you do? Details and entry form here.

Join the Conversation

1 Comment

  1. I’m pretty sure my Dad put a perfboard circuit in the Renault 5 we had in the mid 70s that made the windscreen wipers do an intermittent wipe. I must have been a bout 5 or 6 at the time. It must have made quite an impression on me because I can still picture it in my mind 35 years later, the first circuit board that I ever saw :)

    Thanks for the post that brought back that old memory for me.

Leave a comment

Your email address will not be published. Required fields are marked *

Notify me of followup comments via e-mail. You can also subscribe without commenting.