Best way for Relay in domestic applications

[vasudevan.palani]

*,

I am planning to do home automation using microcontrollers.

The application has to be power efficient, Normally a +5 is required all times to make the relay close the circuit.

Latching relay seems to be a good option, however, have couple of concerns though

1. I think, it can be only switched on ( just like traic ), cannot be switched off ( isnt that so ?)
2. I dont get latching relays in my place.

Requirement, i should be able close a AC circuit ( 230V, 4A, 50Hz ) from a Microcontroller I/O pin. I should also be able to open the AC circuit as well.

IGBT seems to be a good, however, its very costly.

Is there any other cheap and energy efficient solution?

Thanks

-Vasu

 

[D.A.(Tony)Stewart]

You can use 12V or 5V SPST relays which come in signal contact type <2A and power contact >2A type.

12V coils use less current but same power.

Check site for old answers

 

[vasudevan.palani]

For SPST relays, i might have to keep the pin at +Vcc all time.

I guess atleast 100 - 200 mA is required for a simple SPST relay to get activated.

If I have to use SPST, 150mA * 12 hours is no less.

Am looking at something which can be turned on with a current/voltage pulse as well turned off with a pulse.

Thanks

 

[D.A.(Tony)Stewart]

I am not sure of all other unstated requirements.

Load? EMI? Battery operation? Memory in case of power fail? Number of MCU ports required?

They make many types of high quality efficient relays that consume 0.1% of load as well as more expensive latching relays with either bipolar voltage or dual coils . Omron make the best relays and have the best documentation. More...

DigiKey has the best selection

impulse drive latching relays require much higher current and 4x cost typ.

 

[ard]

The X10 appliance modules use what you describe; its a relay with a cam driven contacts. Each pulse turns the cam by 90 degrees (I think), and there is no need to keep it powered to maintain that state. Unfortunately, I dont have the part number.

And it works on 120 volts.

 

[chuckey]

"The application has to be power efficient" unless you are switching really small AC devices it will be with relays, a relay with a 2W coil can switch 2KW of AC , so it would waste .1% of the power. With really small relays, a coil wattage of .2W should be able to switch 20 W of AC, i..e. it wastes 1%.
Frank