On Thu, 23 Apr 1998 23:40:28 -0500 Vic Richter writes: >I want to use a basic stamp 1 as a zero speed indicator. Acutally, >what >I need to >know is when a motor that turns an air lock, at about 15 rpm, stops. >I need to use a proximity switch to send pulses to the stamp. The >prox. >switch >will be connected to 12VDC. Many of these industrial switches have an "open collector" output that acts as a switch to ground. In that case, you could use a resistor to 5V to pull the output up and make a direct connection. A resistor in series to limit any fault currents into the PIC would be a good idea. If the switch outputs either 12V or 0V, connect it through a rather large (100K) resistor like the oft-discussed direct RS-232 connection. The protection diodes in the PIC will keep the voltage from rising much above Vdd. >an opto-isolator. An opto-isolator would do the job nicely. It only has much benefit if the switch's power supply is completely isolated from the PIC power supply as well. _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866]