I need a timer that will give me a 30 minute off time and a 30 secend on time + Manual trigger ON. Mathmatically I can do this with an astable 555 but I am not sure it is practical.

thoughts?

 

Unless you need precision a 555 will work just fine, but it will take two, one for each duration.

 

30 minutes is too long for a 555 because the huge timing capacitor will have a higher leakage current than the high value timing resistor's current.

Use a CD4541 timer IC that has an oscillator and an adjustable digital divider.
A CD4060 is also an oscillator and an adjustable divider.

 

Thanks for the tips, do you have any circuit examples for the CD4541?

 

Thanks for the tips, do you have any circuit examples for the CD4541?

Its datasheet does not have applications circuits.
Look at Texas Instruments datasheet for the CD4536 timer.

 

yea Adiouguru is right there is no applications circuit in the datasheet,and also CD4060 will do just fine.goto www.electronicsforu.com.