Understanding the Stamp

Dr.No

Okay, I want to do i basic test circuit... that is use pin 0 to power a light bulb.

I'm thinking that I connect the pin 0 to the bulb and connect the bulb to the GND pin.

However, I'm confused because the GND pin is not linked to anything and there's no solder
leading anywhere (underneath).

Is this okay or do I need to connect the bulb to another GND.

Also, I just want to be sure that the + is always the OUTPUT of current and the - is the intake
or return.
I keep getting these mixed up.

Thank you all.

Mike Green

Most light bulbs draw too much current for the Stamp's I/O pin. The maximum amount of current you can use is 20-25mA on any single I/O pin. The total current on groups of 8 I/O pins is 50mA. More will damage the Stamp. If you want to switch more current, you'll have to use an external switching transistor. Parallax's Industrial Control tutorial has a discussion and examples of this around page 90. You can find this tutorial in the Stamps in Class Downloads section of Parallax's Resource tab off their main web page.

If you happen to have a bulb that draws 20mA or less, you connect one side of the bulb to ground and the other to an I/O pin. The I/O pin provides the connection to +5V when you set the I/O pin to HIGH. Do not use an LED without some kind of current limiting resistor.

Dr.No

Thanks again.