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Topic: FAN - Problem GND?? (Read 6339 times) previous topic - next topic

jack wp

Aug 02, 2013, 11:31 pm Last Edit: Aug 02, 2013, 11:38 pm by jackwp Reason: 1
About the thread we have been working on for a few days you say:
I find it very strange, that the transistor does not work or changed the pins of the base, the collector and emitter

Does that mean that you did not know which pins on the transistor were what?
Did you just find the transistor in a junk box, and don't know even what it is?
I think we need to solve the first problem before I go on to another. this thread subject is "FAN - Problem GND??"

The schematic showed a TIP120 (NPN) is that the one you were using?
What transistor were you using? Do you have more than one of them?


I went to a store to buy the transistor TIP120, where pin 1 - Base, pin 2 - Collector, pin 3 - Emitter.
Since they had the TIP120, gave me the BD645 transistor, in which I said it was similar to TIP120.

I consulted the datasheet:

It's the same connection TIP120.

I have one more transistor BD645.

jack wp

Ok, so you connect the resistor to the base (pin one) ?
the fan to collector (pin 2)?
and the ground to emitter (pin 3)?
You put the protection diode across the motor? Thats to protect the transistor from back EMF. Make sure the diode is put in correct polarity, or, instead of protecting the transistor, it could burn it out.

So if connecting the resistor hooked to the base, to +5 does not run the motor, may be time to try your other transistor.


Yes. i think i have to try another transistor, but i think the transistor that i use is inside already a diode.

If it has a diode, i don't need to use another rigth?

look to the datasheet of the transistor that i use, in the next image:

jack wp

Looks like you are right.


this is my circuit:

This is my relay:

Can someone tell if the conectios is alright?
I'm confused about the pin 30, 85, 86 e 87 in relay to the conectios to my circuit..


jack wp

I could not make out some of your image. I think this is the relay isn't it?

if it is, then your schematic is wrong. 85 and 86 are the pins to the coil.



Now i can turn on the Lamp with a external power suplly  :)

Now i understand this logic.


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