SparkFun Forums

[vinodquilon]

Find the attachment (http://www.scribd.com/doc/27157788) . The purpose of the circuit is to turn on reed relay for 60sec, when
first ring_signal occurs. For that I have to use C= 100 uF & R= 560 K. But somewhere I have
read, in the design of 555 mono take R= 10 K to limit current through the internal transistor
to 1 mA.
Is it correct ? Can I use 560 K ?

It is my first time experience with Eagle to draw schematic. If someone notice any drawing faults
in my schematic, pls inform me to improve my drawing skill with Eagle.....

[riden]

Yes, a 560k resistor will work just fine. You should see about a 61 second delay, depending upon the leakage of the capacitor.

Because of the long delay time, I usually combine a fixed value resistor along with a variable resistor in series. For example, in your case, maybe a 390k fixed and a 250k pot. You then can precisely set the delay time.

[vinodquilon]

Simple PICAXE-08 program to create accurate 60 sec output time delay when first ring trigger occurs.

start:
if pin3=1 then holdoff
goto start

holdoff:
high 2
wait 60
low 2
goto start


See the attachment (http://www.scribd.com/doc/27222082) . Opto-couplers' output goes to IP 3 (pin no.4) of PICAXE-08.
I will connect IP/OP 2 (pin no.5) of PICAXE-08 to base of relay driving transistor BC547.
Thus I can accurately turn on relay for 60 sec when first ring signal comes.

I am newbie in the field of PIC microcontroller. Thanks for all help by IanP of edaboard.

I couldn't find any eagle libraries for PICAXE-08 on cadsoft. Does anyone have ?

[riden]

Okay, so it out with the 555 and in with the PICAXE. Regarding Eagle libraries, have you checked the Revolution (creators of the PICAXE) site? A Google of Eagle PICAXE libraries will get you here:

http://www.rev-ed.co.uk/PICAXE/pcb.htm