Help/Suggestions with my micro controller based project

[2bengg]

For my final year project i wish to design something that incorporates the following things.

1. 5 devices can be turned ON/OFF using the wall switch (230v AC input).
2. the same 5 devices can also be turned ON/OFF using relays interfaced to a micro controller.

The same micro controller should also be able to detect if a device has been turned ON/OFF using the wall switch. - i need help with this.

So, basically the micro controller should somehow monitor all the 5 wall switches and be able to detect the status of each of the device ie if the switch is ON or OFF.
this needs to be a continuous process.
I am pretty confident about the software part, i need help with the hardware interfacing part.

Problems,
5 switches have to be monitored at the same time.
I wish to have the status of each of the device as a signal (high or low for ON or OFF respectively) on 5 different pins of the micro controller. so that it can be fed to any of the I/O ports of the micro controller.
is this possible ?

i hope that i have been able to explain what i need to do clearly :-?

thanks in advance

 

[prmurthy]

I am putting here again as done in your previous thread.

Hi
Just to put a thought on yours. What happens if the switch is closed and the wire is snapped . Or the other way round what happens if the switch is closed the wires is NOT snapped and the SWITCH itself is NOT working !!!!! )).

Thankyou

 

[2bengg]

well im not entirely sure what you mean,
but if something like that were to happen, then i guess the device to be operated by the switch would not work, since the switch malfunctioned or the wire was disconnected.
those are extenuating circumstances and im not really to bothered about them. should i be ?

 

[prmurthy]

Hm if you are not concerned with the malfunction of switch and wire snapped or break. The here is some tips.

1. Connect the Hot or Live wire to a diode and then connect to a resistor.
2. Sense the output of the above using opto-coupler.
3. Feed the output of opto-coupler to your microcontroller.

You have to do this for each and every switch.

Hope this will help a little.

Thankyou

PS: By the way I am also doing the same but my requirements are fault tolerance. Which unfortunately I am unable to do it.

 

[2bengg]

hmm so does that mean i have to use an opto-coupler for each ?
is there some ic i can use so that it makes the circuit more compact ?

 

[seadolphine2000]

hmm so does that mean i have to use an opto-coupler for each ?
is there some ic i can use so that it makes the circuit more compact ?

Yes, it's safer for your controller.
For an Opto-Coupler IC, use this https://www.google.com/url?sa=t&source=web&cd=1&ved=0CBMQFjAA&url=http%3A%2F%2Fwww.toshiba.com%2Ftaec%2Fcomponents2%2FDatasheet_Sync%2F%2F206%2F4195.pdf&rct=j&q=tlp281-4&ei=IHhrTeG9I5Ko8APT-cy_BQ&usg=AFQjCNGFAF6wBqHFDPBCariWoW_pSVw5aw&sig2=A-toGxR_g6VesJDiGjJPsg&cad=rja

Use also Solid State Relays to switch ON/OFF your 5 devices.

 

[2bengg]

are you suggesting that i use power MOSFETs instead of the relays ?
or instead of the normal switches ?

 

[alexan_e]

A mosfet can only switch DC loads, for AC you need a relay (standard or solid state),
you can probably use a triac too to switch the load but i would prefer the relay solution.

Alex

 

[seadolphine2000]

A mosfet can only switch DC loads, for AC you need a relay (standard or solid state),
you can probably use a triac too to switch the load but i would prefer the relay solution.

Yes, you are right. I mixed it with the Solid State Relay.
Thanks for the correction.

 

[prmurthy]

Hi

I think solid-state is little more costly than opto-couplers. Here are 2 more links for 4 ch optocoupler.

I think you would not get anything in 5 ch or 7 ch you will get 4ch or 8ch. Unfortunately I didn't remember any 8 ch one but 4ch yes there are plenty.

**broken link removed**
**broken link removed**

Thankyou

---------- Post added at 15:42 ---------- Previous post was at 15:38 ----------

are you suggesting that i use power MOSFETs instead of the relays ?
or instead of the normal switches ?

It is always wise to make things easy and not complicate. If you use solid state relays or something like TRIAC you are actually trying to replace the existing ones. Think in the easiest way which require minimum efforts.

Thankyou