sailingharry
New Member
I'm looking to make a run timer with a reset. I have a thermostatically controlled refrigerator on my boat, and I want to be able to "force" it to run for 30 minutes when I have extra power available (engine, shore power, etc). I also want to be able to cancel it. What I envision is a single push button, that when pressed engages a relay (and an indicator lamp) and starts the timer. The timer would run for 30 minutes and then shut down. I'd also want to be able to press the same button, and have it shut down.
I can find many appropriate circuits using a 555 as a timer (but I think it sounds like I can't really get 30 minutes from that...), and I can also find latching flip flops to turn a single push button switch into an on/off circuit -- but how to do both? I'm sure that there are lots of mechanical solutions, but I'd really like to make a semiconductor solution as a learning exercise.
Thanks!
Harry
I can find many appropriate circuits using a 555 as a timer (but I think it sounds like I can't really get 30 minutes from that...), and I can also find latching flip flops to turn a single push button switch into an on/off circuit -- but how to do both? I'm sure that there are lots of mechanical solutions, but I'd really like to make a semiconductor solution as a learning exercise.
Thanks!
Harry