Thursday, March 17, 2011
The CQD Experience, The Ignition Switch
This video is for "The Ignition Switch" featured in QST Aug09. This circuit provides protection against transient protection when starting your car and proves a delay off time for APRS equipment to send data before shut-down. Over all this project is about 3 out of ten for difficulty, all parts available though mouser or digikey. I'm still doing video's in a one shot deal no editing this one is a bit rough.
Some thing I have to test but haven't done yet is try the TLC551, it's another version of the 555 but even less current than the 7555. I'll keep you updated on that test.
This is from the article QST Aug09
"My goal was to come up with the smallest and least expensive circuit consisting of readily available parts. The heart of the circuit is a 12V relay rated at 25A. The circuit also consists of two 7555 IC's, CMOS version of the famous 555 timer developed in the early 1970's. Total current draw is about 100mA while on and 0mA while off. The first timer, U1 turns on by battery voltage from the vehicle ignition switch and turns on timer U2 via D2 after a 10 second delay. When U2 is turned on , it energises relay K1 via Q2. K1 keeps power on U2 until it's time cycle is completed and K1 released. Timer U2 is kept from timing and relaseingK1 by Q1 until battery voltage is removed from the vehicle ignition."