design relay circuit

[chasekan@gmail.com]

hi,
I have problem with designing relay circuit,
please kindly help me
I am using 8051 (p89v51rd2) micro controller, according to my program the relay must have contact with NORMAL CLOSED when the controller sends binary1(5v,1mA),where as sending binary0 the relay must have contact with NORMAL OPEN



for simple understanding need inverter circuit for handling relay

thanks in advance

 

[treez]

you don't say what current the relay must carry...or the holding current of the relay coil.
But it sounds to me like you need the micro to switch a bjt or fet, which switches current into the relay coil....and thus actuates the relay.
Look at the relay coil resistance to see what extra (if any) series resistor you have to put in series with it.

 

[chasekan@gmail.com]

sir it has 112ohm resistance

 

[treez]

that means , if you use 5v rail, that the current in the relay coil can be 4.8v/112 amps (if a bjt is used to switch it)......is this enough to actuate the relay?....look at the datasheet

 

[chasekan@gmail.com]

sir i use one transistor inverter with collector voltage 12v,nearly 11.6mA, base voltage is only 5v with 29uA from micro controller,

 

[treez]

12V/112R = 100mA

 

[chasekan@gmail.com]

sir please look at the attachment,according to that concept the relay does not work

- - - Updated - - -

sir i want to work with the second circuit, why doesn't it work relay

- - - Updated - - -

sir i want to work with the second circuit, why doesn't it work with relay

 

[treez]

I don't see the relay

 

[chasekan@gmail.com]

output mark is connected with one terminal of relay and the another terminal of relay is connected to the ground

 

[treez]

the relay is needed in the schem...where is the other part of the coilconnected to?, 12v?, 5v?, anywhere else.?

 

[BradtheRad]

The relay coil needs to get sufficient current to energize it. It needs to be in the position occupied by the final pull-up resistor in your schematics.

Example:

Your spec is for the relay to be Off when your incoming signal is high.
If your relay is SPST (N.O.) then you will need to add a second transistor as shown in your second schematic (post #7).

Or else you can use the NC contacts of a SPDT relay (shown in my simulation above).

 

[chasekan@gmail.com]

sir, before proceeding my conversation, first, herewith i would like to convey my heartfelt to both treez and bradtherad for sparing your valuable time for spending on my thread, thank you so much sir,


sir herewith i ve attached my schematic design,

the exact condition is

when controller sends binary 1 the red LED should glow
where as controller sends binary 0 green LED should glow


the strong requirement here is we should not change the red and green LEDs alternatively(to NC and NO).

- - - Updated - - -

sir, before proceeding my conversation, first, herewith i would like to convey my heartfelt to both treez and bradtherad for sparing your valuable time for spending on my thread, thank you so much sir,


sir herewith i ve attached my schematic design,

the exact condition is

when controller sends binary 1 the red LED should glow
where as controller sends binary 0 green LED should glow


the strong requirement here is we should not change the red and green LEDs alternatively(to NC and NO).

 

[chasekan@gmail.com]

hi everybody now i ve designed the above state analogue circuit,thank you so much foe your guidance thanks lot