View Full Version : Relay control in bs1usb

11-11-2009, 10:51 AM
Hi again guys!

Im using BS1USB in my project and i have a circuit of a relay and LED indicator. My problem is how to trigger the relay to light up the LED. I think my power supply from the BS1USB cannot trigger the relay. I try to separate the power supply of the circuit still not working.. hope you can help me.. thanks.

Mike Green
11-11-2009, 01:12 PM
Nuts and Volts Column #6 shows how to drive a relay from a Stamp I/O pin. Click on the "Resources" tab on Parallax's website and you'll see a link to the Nuts and Volts Column index.

Vdd from the USB port should be able to supply 100mA to drive a 5V relay. If you use a low current reed relay, you could probably drive that directly from a Stamp I/O pin. There are reed relays that have a 5V coil and turn on with as little as 20mA. RadioShack carries one for example.

If you have problems driving a relay and/or LED, you need to post your schematic. A brief description is not enough to get meaningful help.