Project overview
Hello, I need the assistance of an electronic engineer to improve a small circuit, I'll try to describe my project as best as possible. The numbers of the GPIOs below are the actual ones I'm using: -- THE CIRCUIT I HAVE: I have a simple small circuit that connects to a RPI. The circuit is made up of a CMOS555 timer that receives a pulse signal from GPIO-17 to keep the timer from reaching the end of the duty-cycle. If the GPIO-17 pulse signal vanishes, the pulses will not arrive to the timer and the duty-cycle will eventually (5 minutes after) reach the end. At the end of the duty-cycle, the CMOS555 timer will power off a mosfet, and within 3 or 4 seconds after, power back on. The duty-cycle will loop, unless the pulse signal becomes present again. The RPI power is connected to that mosfet, so this means that when the duty-cycle reaches the end, the RPI will power off for a few seconds, and then power back on. -- THE IMPROVEMENT I NEED: I need to know when the CMOS555 timer has reached the end of the duty-cycle. In other words, I need to know when the timer turned the power off and then back on for the RPI. My initial idea was to use another 555 timer that would trigger when the CMOS555 duty-cycle would reach the end. I would like to use GPIO-3 as an input to identify the state change of the 555 timer trigger/latch, and GPIO-22 as an output to reset the 555 timer. That's my idea, however I'm not even sure if my approach is the most appropriate for this design. Therefore I would like an electronic engineer to select the correct components and schematic design. Whatever the solution, I just don't want any PIC solutions where I have to do programming to any chips. I'm simply looking for a hardware solution that is reliable and won't falsely trigger. For this project I will only need the schematic (just an image is fine) and a parts list. I know how to create the PCB from there, and assemble it. This project is really small stuff, and shouldn't take a professional too long. I'm posting the schematic for your review of the current circuit. Please let me know if it interests you. Thanks in advance.