View Full Version : using ULN2803's to drive BS2P40 outputs

James D. Lane
06-14-2005, 03:13 AM
HI, new here and new to the basic stamp and have to produce an 8 input/ 8 ouput channel controller using the BS2P40 for a machine that we normally use a PLC to control. It was recommended that I use the ULN2803's to buffer the outputs on the 2P40 to drive some 5VDC relays that will inturn be operating some solenoid valves. What are the recommended connections between the 2P40 outputs and the ULN2803 inputs and the ULN2803 outputs and the relay coils? Any added resitors to add to the circuit? Or is it all "canned" in the ULN IC?

06-14-2005, 03:18 AM
Here is a PDF file that will help with this project (attached).


Dave Andreae

Tech Support
dandreae@parallax.com (mailto:dandreae@parallax.com)

06-14-2005, 03:50 AM

It is all canned. The series resistors to the Stamp, and the diodes to snub the spikes from the switched inductive load, are all in the package. You should still read the PDF that Dave attached, though. It gives you a nice grounding in the principles of driving heavy loads with the Stamp.


Peter C. Charles

Director, Research and Technology
CyberBiota, Incorporated
Peter.charles@cyberbiota.com (mailto:Peter.charles@cyberbiota.com)
http://www.cyberbiota.com (http://www.cyberbiota.com)