Need help with simple transistor switch

[zanor]

simple transistor switch

Hi!

I'm trying to controll the remote wire of my car amplifier with a PIC (part of a power controller for my carputer ). But I can't get it to work.

Please help me

 

[lladnar23]

transistor switch

The problem is that the emitter of your NPN must be a diode drop lower than the base. For your PIC I/O pin, it probably swings approximately 0 to 5V, so when the I/O is high (5V), your load won't see a voltage any higher than ~ 5V - 0.7V = 4.3V. Obviously, you want to power the load with 12V, not 4.3V!

Now, if you were to use a 2N3906 (PNP) transistor, you would have a different problem: if your base is at 5V when the I/O is high, your transistor is ON all of the time, and there is no way to turn the load off.

If your PIC has open-drain outputs, then you are in business: just use a PNP transistor and attach the base to the open-drain I/O pin through a base resistor.
Otherwise, you might need to use 2 transistors or a relay, etc.... to do the switching. (You could use an NPN to pull the base of a PNP low, turning on the switch.)

Hope this helps!

 

[zanor]

transistor as a switch

Thanks for your reply!

If your PIC has open-drain outputs, then you are in business: just use a PNP transistor and attach the base to the open-drain I/O pin through a base resistor.

Could you please explain this part for me? Because my PIC (16F648A) does have one open drain port.
What is a open drain port? What does it do diffrent?

 

[IanP]

12v transistor switch

Take a look at the pictures below ..
They show how to connect 12V loads to 0-5V control pins ..
These circuts can be used with any general purpose I/O pin of a microcontroller, or if microcontroller has OD (open drain) output, it can be connected instead of the 2N3904 transistor (collector) ..

Regards,
IanP

 

[saeed_pk]

simple transistor switch circuit

You can switch a SPDT Relay with a transistor and then you can control what ever you want but remember when u place the Relay then becarefull about flachback Current in case of Inductor Deenergizing then you should Provide a Path for Relay inductor to discharge without harming the rest of the circuit with the use of a DIODE

 

[yogi]

pnp transistor switch

see the switching circuit from the book
my experience in autonomous robotics
get from yahoo group-booksbybibin

 

[manu]

transistor 12v switch

Pic haven't open drain I/Os but push-pull I/Os, that's totally différent !

Have a glance here :
**broken link removed**

...and try the attached schematic :wink:

What's your load ?!

 

[Ave_Rapina]

pnp transistor open drain

Hi!

I'm trying to controll the remote wire of my car amplifier with a PIC (part of a power controller for my carputer ). But I can't get it to work.

Please help me

You cant pull out with your inicial configuration no more than 4.3 V

To activate an 12V charge you need another transistor configuration

R3 act as load

 

[vgg]

pnp transistor as a switch

Hi!

I'm trying to controll the remote wire of my car amplifier with a PIC (part of a power controller for my carputer ). But I can't get it to work.

Please help me

You cant pull out with your inicial configuration more than 4.3 V

To activate an 12V charge you need another transistor configuration

R3 act as load

That schematic is not good. It is absolutely necessary to have one more resistor in collector of Q1. If Q1 is open, it's collector current will have no limitation (and base current of Q2, too!)

 

[Ave_Rapina]

+pic +pnp +switch

Q2 is an Pnp Transitor....

Just conduct when the q1 colector is lower than 12-0.7v

When Q1 is shut down there is no corrent the the potencial in colector is 12V then Q2 also shut down

I think You may not have see the PNP transistor
100Ω is the charge to supplie
I edit the repplie of the circuit
Regards

 

[yogi]

transistor switch 2n3906 schematic

read this
**broken link removed**

Bibin John
www.bibinjohn.tk