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555 timeout troubles? Answered

Evening all,

 This is most likely a very basic problem but for the life of me I can't find the solution. The project: auto folding wing mirrors (see below)


The problem: for some reason my alarm logic is the opposite way round, most likely due to the removal of my motion sensor due to it tripping my alarm when locked. Now I have modified the circuit shown in the PDF to remove TR2 and R4 so the I/P to the 555 is kept high by the 12v alarm signal. I have a pot between pin 2 and ground so I can adjust the pull down point as the alarm signal only drops to 9.7V and, obviously, the 555 needs logic high or low. So, having adjusted the pull down point, I find that the 5 second timeout, which worked when I first built the circuit as per the PDF, no longer switches the O/P off. 

So so what am I doing wrong or is it just best to us a picaxe to do all of this as I code write up the code in half an hour or so.




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5 years ago

Spent some time to resolve the circuit board to a schematic.

Perhaps tomorrow I will try to understand your problem.

It would not hurt if you verified the layout matches.