Calculating resistor value for Sleep

Buddie

Hey,

Can anyone advise me on how to select the proper pull-up resistor to use for a Basic Stamp sleep command? The manual states that the outputs cycle every 2.3 seconds and to use a resistor pulled high to keep loads from cycling. I am controlling relays through transistor setups and need to know how to calculate the values for the pull-up resistors. (e.g., I have a 2N3903 connected to·2 relays in·standard setup with a 330 ohm resistor between their bases and the stamp. What pull-up value should I use?)

Any help is greatly appreciated!

Mike Green

You probably need a pull-down resistor rather than a pull-up. 10K should work (connected between the I/O pin and ground).· That will ensure that the relays are turned off.· If you want the relays to turn on and stay on during sleep, first make sure that you want that sort of behavior because the relays will turn on when you power up the Stamp and stay on until your program disables them.

You may need some kind of external flip-flop hooked up to two I/O·pins, one to set the flip-flop on and the other to set the flip-flop off.· This could be connected to come up off when the power is applied and the amount of power used would be tiny if left on all the time.


Post Edited (Mike Green) : 3/16/2009 10:57:01 PM GMT