Relay connection with 8051 microcontroller ?

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vead

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I am trying to connect 12 v relay to 12dc motor
someone can look the connection in Image ?
I have doubt that connection may be wrong ?
 

Ground connection missing for DC Motor!!!!
 

Notice that a 8051 port pin sources only a few 10 µA, can't drive a bipolar transistor without external pull-up resistors.

I'm sure you have heard about this point before, it's been mentioned in countless 8051 Edaboard threads.
 
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I am testing manually on breadboard. the wiring connection is same as show in image. I have 5vdc and 12v dc

Now the problem is that both relay and motor are running continuously. I saw both motor and relay does not turn off when 5v dc is switch off.

that does not matter if 5v dc supply is switch ON/OFF. motor and relay are continuously running.

what may be reason? why relay does not turn on / off to motor. how to fix problem ?
 



Where you are using 5V in your circuit. Is it for your microcontroller? The relay & Motor is connected with the 12V DC. Clarify it
 

hobbyckts said:
Where you are using 5V in your circuit. Is it for your microcontroller? The relay & Motor is connected with the 12V DC. Clarify it
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no still I am not using microcontroller. I just want check manually , thats why I connected the power supply , look below image
 

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What you do connect the one end of the motor directly to the ground.

Relay Connections: Connect NO pin to +12V, NC to Ground & COMMON pin to another end of DC motor.


Now DC motor one end will be connected to ground and another end will be to common pin.


Try this.... It has to work

- - - Updated - - -

Remaining connections leave as it is.. Even the 5V power supply.. Don't alter anything else
 
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    vead

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yes that's work. but I think you did not understand what I am trying to do

port pin high means 5 v
port pin low means 0 v

I did not program MCU to run motor using relay. I want to connect 5v dc supply. so that pin may be High or low
 

How long will you continue to show the erratic motor circuit, see post #2 and #3?
 


Yes, You do the circuit without microcontroller and do the connections as per my previous post. Just connect the 5V power supply at the base of the transistor and sure it will work as per your requirement.

Note:Make sure you are shorting both the grounds. i.e. Short 5V ground and 12V ground together to complete the circuit.
 

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