howto operate a 12 volt dc RELAY with 89C51

[ZOBI]

i want to operate 12 volt relay with 89C51 any idea?
i wrote a program which set HIGH at pin 1.0 , although its working and giving 5 volt but does not turn on 6 volt relay
any idea what to do with this, i have also tried to connect a 2N2222 and also d313 with this pin 1.0 and take output from transistor’s emitter pin making collector common but still it dose not  work ,any additional circuitry i should made?

[manohar]

emiter o/p of the transister connect to ic ULN2003 n o/p of uln2003 connect to relay.

[Qaisar]

use any circuit from these 2

wysiwyg_imageupload:3434:

 

 

[ZOBI]

Cn i use 2n2222 instead of Bc547?

Does above CIRUIT 1 work with 2N2222?

[Dexter]

uln 2003 is the best choice

for relay driving circuit

[Mehtab Ali]

use opamp as a comparator for driving the relay

[AJISH ALFRED]

I never recommend you to use ULN2004, just to drive a single relay. It has 8 output pins and you are going to use only one. It will just increase the cost and make your circuit complex and bulky.

Try using a transistor as a switch method,

Take any general purpose NPN transistor, ground the emitter, collector to one end of relay coil, connect the other end of the relay coil to VCC. Connect the output pin of the controller to the base of the transistor via a resitor of value 10k or less.

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