I'm wishing to make a door ajar warning for the fridge door. I have a few circuits using 555 timers that say they will do that - start a timer when the door opens, then if the timer counts down it sounds a piezo buzzer, but I may have a larger problem.
I've tried a few circuits, they all result in a VERY hot 555. So, I tried hooking up just the power rails, I have pin 1 - Ground, pins 8 and 4 to Vcc (5V). Even in this case the 555 quickly becomes too hot to touch.
Is that a valid way to test a 555 for basic integrity? I'm not sure that tying the reset line high is a good idea.
The timers I have are cheap imports, 10 cents each, but I've now tried 4 of them and get the same result. I can accept a small error rate but I've found imported ICs to be just fine in general.
I am thinking that one of the circuits at http://home.cogeco.ca/~rpaisley4/LM555.html#28 (Timer Output Section) would be what I want, or the most basic circuit at http://clarkson-uk.com/555-timer/operation/frames3.html
This's turned from being what I thought would be easy to being a nuisance, and I can't just put it aside defeated.
I've tried a few circuits, they all result in a VERY hot 555. So, I tried hooking up just the power rails, I have pin 1 - Ground, pins 8 and 4 to Vcc (5V). Even in this case the 555 quickly becomes too hot to touch.
Is that a valid way to test a 555 for basic integrity? I'm not sure that tying the reset line high is a good idea.
The timers I have are cheap imports, 10 cents each, but I've now tried 4 of them and get the same result. I can accept a small error rate but I've found imported ICs to be just fine in general.
I am thinking that one of the circuits at http://home.cogeco.ca/~rpaisley4/LM555.html#28 (Timer Output Section) would be what I want, or the most basic circuit at http://clarkson-uk.com/555-timer/operation/frames3.html
This's turned from being what I thought would be easy to being a nuisance, and I can't just put it aside defeated.