6v relay on 12v system ?

[Krishna Patil]

I'm doing this circuit. 12V relay is used here , can i use 6V relay (miniature type) to save space and mount it on PCB ? Just by adding resistors , is this possible?

I used 12v ,200 ohm mechanical relay it worked fine. Now thinking to replace 6V miniature relay.

Miniature relay specs: 7A,300AC ,6V DC coil || 10A/125VAC , 10A/28VDC

please explain these specifications. Thanks

 

[zia]

yes put resistor and zener of 5.1.

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yes put resistor and zener of 5.1.

 

[pranam77]

Saw your schematic but was too small to see the component markings. Anyways by guessing, i can sugest something. If you are using a Miniature Telecom relay, whose consumption is very less, you can add a wirewound Pot of 1K in series to the coil and set the correct value where the coil gets 6 volts, and then replace the POT with a fixed resistor of Half watt.

 

[TonyM]

Like pranam, I couldn't see the schematic properly either. But you could look at: (1) putting a 200 ohm 0.5W resistor in series with the 200 ohm coil; (2) changing your 7812 to a different regulator to run the whole circuit off 6V (none of the other components are 12V-dependant except the buzzer, can you swap that too?).

 

[alexan_e]

I wonder if it is so hard to find a 12v relay with the same size.
The majority of relays are produced in the same size with several coil ratings.

 

[cyberrat]

5.6v Zener & resistor to drop 12v to 6v.
Perhaps also add a diode under zener to make 6.2v

 

[TonyM]

I'm not quite sure why the zener is needed and not just a series resistor - maybe I'm missing something...?

This is if the circuit voltage cannot be reduced to 6V by changing the regulator, as suggested before.

 

[zia]

plz relay have coil its acts as inductor not as regulator
so for regulation u must have to add zener

 

[TonyM]

plz relay have coil its acts as inductor not as regulator
so for regulation u must have to add zener

The coil does act as an inductor. But when the relay is energised it reaches a steady state and the resistive component of its reactance is dominant. That's why the manufacturer quotes a coil resistance, not a reactance. Therefore a zener is not necessary.

You're getting mixed up about the regulator. I'm referring to the 7812. Please see my earlier post.

 

[zia]

TonyM i think u r right but have u tested it on hardware

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TonyM i think u r right but have u tested it on hardware

 

[TonyM]

Yes, I have - donkey's years ago but yes

 

[zia]

tonyM plz give me details how u calculated the 200 ohm 0.5W resistor for 200 ohm coil

 

[TonyM]

Ohm's Law. BUT...my mistake, I took Krishna Patil's 200 ohms as the coil resistance of his new 6V relay - it's actually that of his old 12V relay. If this was behind your question then I see what you mean. Either way, apologies to all...

However, the resistor should still be equal to the coil resistance of the 6V relay, since you want to drop 6V across the relay coil and 6V across the resistor with the same current flowing through both.

The resistor power is then: P = V*V/R i.e. 36/resistorOhms

 

[Krishna Patil]

sorry for small circuit. Does Miniature Relay have coil ? It doesn't show up resistance value at the energizing side.
What is my doubt is , if i use a solid state relay and it has high resistance at input. Current might exceed the limitations of 555 IC.
My intention is to make relay mountable on PCB.


Is this how you all are telling ?

As suggested i can also use a 6V adapter, with 6V relay , but will it work ?

 

[milind.a.kulkarni]

Hi Krishna....

I had seen your circuit....as you are using a resistance in series with relay for voltage drop so I don't see any problem for relay to work ....the interesting thing in your circuit is how to determine the value of series resistance now to do that you have two different consideration as you are putting ziner diode in parallel to relay ....the ziner will regulate the voltage based on the voltage rating of ziner and will able to supply current based on the wattage of ziner so....first you need to fix this value ....based on amount of current required for relay excitation ....

refer some of the ziner regulator basics-

http://www.zener-diode.co.uk/
http://www.evilmadscientist.com/2012/basics-introduction-to-zener-diodes/
http://www.electronics-tutorials.ws/diode/diode_7.html

Good Luck

 

[glenjoy]

just put a zener diode.

 

[zhengchao201105]

I think what they said is add a resistor at this side

and the resistor value is equal to the relay coil resistor
use a 6V adapter is not the best solution ,because the motor will work undervoltage if the normal voltage is 12v.
just like alexan_e said it is not difficult to find a small size 12v relay
Miniature relay specs: 6V DC coil || 10A/125VAC :it means the coil work voltage is 12v,and the relay can used for a 125v AC/10A