i have been designing a 555 circuit for yr 11 design tec and have been informed that the circuit will run for 1 hr after timing for 6. i need it to only run for a few seconds. is there any way i can do this without putting another 555 at the end?
Sorry, I'm pretty sure you would require another 555 timer. However, assuming that you are using a 'normal' delay circuit with you NE555, (using an RC time constant to set the time delay) I recommend that you try something else; the time delay becomes unpredictable / varies significantly due to component tolerances / doesn't even work at all with such extreme values as you would need for such long time delays, mainly due to capacitor leakage. I would probably use a small PIC to generate delays this long accuratley, (eg 12F675) but I'm sure there is a better way to do it... (I'd take this approach because I've got the parts handy in my workshop) Anyone got a better idea?
Welcome to the forums, simo You could get a long delay using a 14-stage frequency divider (eg cmos4060B) so the original generated frequency is divided by 16,384. 6 hours out then becomes 16,384 x 1.32 seconds or 0.76Hz into the divider. The 4060 has a built-in oscillator too. You still need another timer to turn the end thing off.
