ic555 timer

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PAUL60

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Can this work?
I need to make a timer circuit that would switch a relay on
for one minute then stay off for 5 minutes, then on for 1 minute and off for 5 minuites.
and contuinue like this.
i will be using this to operate a roof cooling system.
where the misters come on for one minute and off for 5
i have 2 ics one a 555cn and the other a tlc555.
hope someone can help
thanks paul
 

Use the 555 (not the TLC555). The plot X axis is minutes. Note that the first delay is longer than the subsequent ones. The 12V relay should have a coil resistance greater than 85Ω.
 

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I might also suggest using a transistor or MOSFET between the 555 and the relay... and that 1N4001 in Mike's diagram is critical to protect the solid-state stuff from the relay's back-EMF!
 
Doktor Jones said:
I might also suggest using a transistor or MOSFET between the 555 and the relay... and that 1N4001 in Mike's diagram is critical to protect the solid-state stuff from the relay's back-EMF!
Click to expand...

Mosfet not needed. The 555 can sink 200mA. The common 85 Ohm automotive relay only takes ~120mA to pull it in. You can use a more sensitive relay...
 
Timer

Hi Mike,
you said The 12V relay should have a coil resistance greater than 85Ω.
how high can i go with the coil resistance?
this is all new to me.
very little experience with electronics
thanks paul
 
555 timer

capacitor C2 i have no luck finding that size 0.1 is there another size that can work?
paul
 
Anything from 10nF(0.01uF) to 100nF(0.1uF). These are very common.
 
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