In a previous thread I asked for suggestions on a refrigerator door open alarm, and while I appreciate the advice, none was applicable. I can't detect a light because it doesnt turn on until the door is open beyond a significant point, and I don't know how I'd build something to mount a snap switch without making it look terrible.
I want to take advantage of the fact that the fridge face has almost no resistance, and use this and the absence of it to power the 555.
The schematic is attached. R4 would be the fridge door. When closed, wires would contact it and complete the circuit with a moderately high resistance. The LED is subbed for the 555 timer.
Intent is that, when the door is closed, electricity flows through the door rather than into the base of the BJT, and prevents the 555 from receiving power. When the door is opened C1 charges, Q1 conducts, and Q2 powers the 555.
Questions:
Will this work?
What resistor values should I use? I made these up on the fly.
How do I ensure that once ON, a transistor will turn off when desired. I can't seem to get that part to work on the breadboard.
I want to take advantage of the fact that the fridge face has almost no resistance, and use this and the absence of it to power the 555.
The schematic is attached. R4 would be the fridge door. When closed, wires would contact it and complete the circuit with a moderately high resistance. The LED is subbed for the 555 timer.
Intent is that, when the door is closed, electricity flows through the door rather than into the base of the BJT, and prevents the 555 from receiving power. When the door is opened C1 charges, Q1 conducts, and Q2 powers the 555.
Questions:
Will this work?
What resistor values should I use? I made these up on the fly.
How do I ensure that once ON, a transistor will turn off when desired. I can't seem to get that part to work on the breadboard.
Attachments
-
52.1 KB Views: 35