Transistor trouble!

rikniknoknik

Well fist off I have consulted this site many times over not to mention the "Bible", (Programming and Customizing the Basic Stamp Computer by Scott Edwards.) And for the life of me I cannot get this damned 5vdc relay to click over using an NPN transistor.· This is my current configuratation that I have.· I built this circuit. I have 12vdc and a 5vdc relay conected to it. Its not working. I have tried this for three days now. I am very proud and hate to consult help in the name of learning but I NEEEEEEED HEELLLP . Parallax Help me finish my auto car starter circuit Please. Thank you.- Andrew, Phx, Az

http://www.kpsec.freeuk.com/trancirc.htm#darlington

Beau Schwabe

What value of resistor do you have on the transistor Base?

Does the Relay "click" if you manually short the B-C transistor junction?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe

IC Layout Engineer
Parallax, Inc.

rikniknoknik

Well actually I dont have to do anything to the B junction the relay instantly clicks over as soon as I turn on the supply.

stamptrol

Circuit looks good. Here's a few things to check:

0. you say a 5v relay, I assume you really mean 12v, according to the sketch? If not, relay is probably burned open.
1. measure from 0v to the collector of the transistor with base open. Should be 12 volts. If not, relay is open.
2. double check orientation of the protection diode.
3. What is value of resistor in base circuit? Probably 2.2 k would be fine.
4. What happens when you jumper from 0v to collector of transistor? relay should operate.
5. Can the transistor handle the relay current?
6. make sure 0v of the 12v supply and the 5v supply are tied together.

Cheers

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tom Sisk

http://www.siskconsult.com
·