Welcome to AAC.
If pin #7 of the 3905 is holding up/down of the 555 pin 2 trig it will not work.
Use a connection cap 10n from pin 7 to pin 2 and a 10k pull up on 555 pin2.
Correction pin#7 of the 3905.
Thank you very much for your assistance.hi,
Look at this, I am assuming that 3905 Timer output goes low at the end of the time period, if not ,you need a transistor inverter.
The 3905 Timer was chosen for its precision which it has allegedly for up to several hours,as well as being immune to fluctuations in the power supply which will have no effect on its acuracy. It can't really operate well in astable mode though.10Meg and a 360uF electrolytic are asking rather a lot of an accurate timing circuit, because (a) the current through the resistor is likely to be of the same order as the leakage current of the capacitor and (b) circuit board contaminants will be in parallel with the resistor.
It is still not clear what you are trying to do.Sorry, the 3905 is supposed to trigger the 7555 CMOS in astable mode for a duration of one hour. The load is going to be earphones and LED lights.
The 3905 is to trigger the 7555 CMOS at 40Hz astable for 1 hour.It is still not clear what you are trying to do.
Do you want the output to last for a duration of 1-hour?
Or do you want the output to be triggered at intervals of 1-hour?
How long does the output last?
What does the output do? Flash or oscillate for how long at what frequency?
Similar, I have to look up the pin out to be sure. It was someone elses circuit which I tested with an LED to make sure it worked like it should. I drew it in the circuit I provided which I believe is accurate.
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by Steve Arar