how to connect relay with MCU-89S52

[H_D_R]

irf7313 circuit

hello all,

i want to interfcae relay with MCU.
i have 12v relay which has five legs.

so i am confused how do connections in circuit.
how to give supply to relay.??
which legs will connect with MCU.??
which legs will connect to the load..??

i am attaching the photo of my relay.

thank you all in advance..!!

 

[joby16]

Hi,

Use a driver/ Transistor for driving the relay from 89S52. (Eg: ULN2803 , IRF7313 etc)
Connect the Relay coil to the output(collector/ Drain) of the driver and the 12V supply.
Also attach a Free Wheeling diode for relay protection.

Regards,
Joby

 

[H_D_R]

Hi,

Use a driver/ Transistor for driving the relay from 89S52. (Eg: ULN2803 , IRF7313 etc)
Connect the Relay coil to the output(collector/ Drain) of the driver and the 12V supply.
Also attach a Free Wheeling diode for relay protection.

Regards,
Joby

thank you for reply.

i have seen such circuit which is using ULN2803. but they are not using diode.
so will it be fair for circuit.??

can anyone send me schematic for connection @ load end side.
i am confused because it has three legs (NO, NC, and COMMON) at load side.
so which connections i have to use for load.??

 

[IanP]

Use NO and COM ..

NC is connected to COM when the relay is not energized ..

**broken link removed**

Regards,
IanP

 

[H_D_R]

thank you so much IanP.,

can any one please tell me the diference between use of Driver IC and transistor ckt for relay driver except the simple circuit..??

 

[IanP]

as far as functionality is concerned there is no difference at all ..

rgds,
ianp

 

[H_D_R]

thank you so much IanP.,

can any one please tell me the diference between use of Driver IC and transistor ckt for relay driver except the simple circuit..??

which one is preferable when muliple relays are used..??

and how to define the required current for relay.?
if i am using greater voltage relay then what will be change in circuit..??
i mean to ask how we can know we should use ULN 2803 or 2003 etc etc.
is there any calculations/formulas.??
please let me know or send me some link from where i can get this details...

thanks.

 

[IanP]

both ULNs can do the same, the ULN2003 can drive up to 6 devices, the ULN2803 can drive up to 8 dvices ..

both can drive loads of up to 500mA ..

if voltages are above 50Vdc you can't use them ..

rgds,
ianp

 

[drbizzarow]

you can use opto between transistor and controller pin for protection

 

[H_D_R]

suppose i want to use higher current relay then which ic is suitable..??

can any body please tell...???

thank you..

 

[joby16]

Hi,

It's depends on the Relay Coil Current. The below link may help you to get a basic idea.
http://www.kpsec.freeuk.com/components/relay.htm

Regards,
Joby

 

[H_D_R]

Hi,

It's depends on the Relay Coil Current. The below link may help you to get a basic idea.
http://www.kpsec.freeuk.com/components/relay.htm

Regards,
Joby

thanks joby,

but can you please tell me how to know coil resistaance as per ohm's low

Relay coil current = supply voltage /coil resistance

at least two parameter must be known..

is it necessary to put diode accross coil..??

if yes then why we are not using it when we are using an driver IC istead of transistor circuit.???

 

[joby16]

Hi,

The Relay rating (Voltage, Resistance etc) will be mentioned in the Relay itself.
If the relay driver has internal relay protection circuitry, then the external diode is not required.

Regards,
Joby

 

[H_D_R]

Hi,

The Relay rating (Voltage, Resistance etc) will be mentioned in the Relay itself.

but the relay which i have,
in that they have mentioned 7A 250V AC and 12A 120V DC.

so how to use this relay with my MCU (89S52) and via which Relay driver..???

 

[joby16]

Hi,

At least you should get the operating voltage of the relay ie, 12V DC, 24V DC etc.
Once you identified the input voltage, you can connect the relay to a DC power supply with an ammeter in series and measure the current.

Regards,
Joby

 

[H_D_R]

Hi,

At least you should get the operating voltage of the relay ie, 12V DC, 24V DC etc.
Once you identified the input voltage, you can connect the relay to a DC power supply with an ammeter in series and measure the current.

Regards,
Joby

sorry to say but i didnt understand your reply.
please read the specification carefully and then reply me again.
because i am feeling that there is somthing wrong..

thankyou..:|

 

[joby16]

Hello H_D_R,

Please let me know what kind of relay you are using. Normally the operating voltage of the relay (ie the voltage to be applied to the coil) must be mentioned in the relay itself. Please checkout anything like DC12V/ DC24V in your relay.. You can observe the voltage is written as DC 12V in the picture below

http://cnhke.manufacturer.globalsou...e/product_id-1000830763/action-GetProduct.htm
**broken link removed**

Regards,
Joby

 

[H_D_R]

see the picture added below.
i think you can see the data also.

i am just using same relay.

i am writing the data written on it's surface.

1st::
7A 250V AC
7A 120V DC
@ 50/60Hz


2nd::
10A 120V AC
10A 24V DC
here it has not mentioned any frequency.

now please tell me, which one i have to follow.

PS:: jpg file is updated.

 

[joby16]

Hi,

observe ur relay once again,PROPERLY, it is written there 12V DC...

got it, or still got problems....

 

[H_D_R]

Hi,

observe ur relay once again,PROPERLY, it is written there 12V DC...

got it, or still got problems....

sorry to say but I am not wrong.
you can see easily by zooming the jpg uploaded in my last post.

let’s say that may be printing mistake.
but my question is how to get the details of Coil-current and coil-resistance.:?: