Hi folks, I'm new here and I need some help. I am stumped on a project. I am trying to build a 5 second timer that is turned on by a voltage change from 12 VDC to 13.8 VDC. When the voltage change is sensed by the voltage comparator, two things happen a buzzer and a timer will turn on. After the 5 second delay, the buzzer must turn off. I have tried to build this circuit in MultiSim and am successfull creating each portion individually. However, when I try and put them all together it doesn't work. I really could use some help here. I am using a voltage divider to run the comparator and a LM555 timer to run the 5 second timer. I am also using a low voltage buzzer (I think it is 5 VDC) in the circuit and a low voltage relay (3VDC). Any help from one of you genius' would be greatly appreciated!!! Thanks, Rivy1992
Show us what the individual circuits look like, and how you stuck them together. Probably just a small thing you need to change to get it all working. You're in logs not modding btw, a mod will probably move it there when they notice it.
Thanks, sorry for the screw up. I forgot my flashdrive ast home and I am at work. I wrote my partner an email to sentd me the schematics in a word document so that I can post them here. She should send then to me within the next 15 minutes and I'll post them right away. Briefly, what I am trying to do is when a car starts, the voltage change in the output of the battery increases frrom 12 to 13.8 VDC. I want to use that change to drive a buzzer that will stay on for only 5 seconds and then turn off. Once the car is turned off, I want the circuit to re-set so that every time the car is turned on, the voltage increase can be detected and sound the buzzer.
