Manual switchover

Thread Starter

ssd_9

Joined Sep 2, 2020
17
Hello all,

I am working on Iot project using ESP32 wherein I am able to control the devices like lights using one way manual switch and over Wi-Fi. My main concern is I using manual one way switch as an input to ESP32 hence I am using 5v at that point. But in case of failure of any device like ESP,TRIAC (used as switch) there is now way I can operate the device. Can you suggest me some manual switchover that can help me in this scenario?

P.S : - PFA attached dummy circuit
Mod: opened your PDF.E
AAA 1173 08.52.gif
 

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AlbertHall

Joined Jun 4, 2014
11,305
Maybe use a changeover relay instead of a triac to do the switching and the manual switch being a 2-way (called 3-way in US I think) then changing the position of either the relay or the manual switch will change the output state. You might want the micro to know whether the load is powered or not so the remote will work the right way round regardlee of the state of the manual switch.
 

Thread Starter

ssd_9

Joined Sep 2, 2020
17
Maybe use a changeover relay instead of a triac to do the switching and the manual switch being a 2-way (called 3-way in US I think) then changing the position of either the relay or the manual switch will change the output state. You might want the micro to know whether the load is powered or not so the remote will work the right way round regardlee of the state of the manual switch.
I want to avoid using change over relay also I want to implement it on one way switch as I have completed the implementation on two way switch. Anything related to the same will be helpful. Thanks
 

sghioto

Joined Dec 31, 2017
2,360
I want to implement it on one way switch as I have completed the implementation on two way switch.
What does "completed the implementation on two way switch" mean?
Seems like all you would need is a standard 3 Way wall switch.
1613080054350.png
 
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Thread Starter

ssd_9

Joined Sep 2, 2020
17
OK then add a switch in series.
View attachment 230151
Thanks for the reply. But, I will need 3 switches in this scenario one for the input, 2 three way switches for the output. So for switch board with 5 switches we will need 15 switches leading to increase in cost and also disturb the look of the house. Can anyone suggest other way around? I want to implement it in my house.
 

strantor

Joined Oct 3, 2010
5,543
If the triac fails short you couldn't turn the light off.
I realize this isn't your point; you were just clarifying TS's point, but you said it best so I'm quoting you.

Is this a reasonable design goal? A manual override? Yeah, what if the triac fails short? The light stays on. what if the triac fails open? The light stays off. Are these lights part of a life support system? Why do you need redundant backups? Do you have redundant backup light switches for your existing light switches? Why, yes, actually you do. In your breaker panel. Not sure what about this demands the extra effort.

But for the sake of argument I'll just accept that a classroom full of children will die if these lights fail to switch on/off when desired.
1. Use an overrated triac that won't fail
2. If for some reason you still don't trust one of the most common discrete components in existence, Use a 3-way switch as already suggested.
3. If that's not good enough for reasons you can't adequately explain, use a relay as already suggested.
4. If that's not good enough for reasons you simply decline to explain, use a matrix of triacs to ensure no single points of failure. With the matrix, the majority of the triacs could fail open or closed, either way, a current path would exist if you wanted it to, and not if you didn't.

Screenshot_20210212-002851_Samsung Notes.jpg
5. If that's not good enough, then nothing is.
 

Thread Starter

ssd_9

Joined Sep 2, 2020
17
I realize this isn't your point; you were just clarifying TS's point, but you said it best so I'm quoting you.

Is this a reasonable design goal? A manual override? Yeah, what if the triac fails short? The light stays on. what if the triac fails open? The light stays off. Are these lights part of a life support system? Why do you need redundant backups? Do you have redundant backup light switches for your existing light switches? Why, yes, actually you do. In your breaker panel. Not sure what about this demands the extra effort.

But for the sake of argument I'll just accept that a classroom full of children will die if these lights fail to switch on/off when desired.
1. Use an overrated triac that won't fail
2. If for some reason you still don't trust one of the most common discrete components in existence, Use a 3-way switch as already suggested.
3. If that's not good enough for reasons you can't adequately explain, use a relay as already suggested.
4. If that's not good enough for reasons you simply decline to explain, use a matrix of triacs to ensure no single points of failure. With the matrix, the majority of the triacs could fail open or closed, either way, a current path would exist if you wanted it to, and not if you didn't.

View attachment 230192
5. If that's not good enough, then nothing is.
Got your point and not arguing as well. But if someone knows or have done this somehow It will be helpful.
 

Ian0

Joined Aug 7, 2020
2,175
Preusambly, you're not using filament lamps (because they are becoming tricky to get). Triacs are very robust, they take overloads of 10 times their rated current easily. They only thing that generally kills them is a lamp filament falling across the internal lamp teminals and making a short-circuit. They never fail open-circuit. If you're using LED lamps, a short-circuit MOSFET in a LED lamp power supply might kill them, but the LED lamp will be fused in the realm of a few hundred mA. That won't bother an 8A triac, unless it's a dodgy foreign import LED lamp with no internal fuse. Anyway, if the LED lamp fails, it won't stay on!
Your circuitry might fail, and might not switch the triac on - they is probably more likely!
If you're that bothered, connect your triac with 3.5mm terminal blocks, like they did in disco light controllers (where triac failures were a common occurrence in the days of filament lamps because flashing lamps fail more often).

My suggestion - use one of those fish-key switches they use for emergency lights in parallel with the triac, so you can switch the lamp on in an emergency. If the triac fails short and the lamp stays on, remove the lamp from the socket. If it's an LED lamp it won't be too hot to touch.
https://uk.rs-online.com/web/p/key-...5Kl7yiRdZKlsbV8gyXxoCyV4QAvD_BwE&gclsrc=aw.ds
 

sghioto

Joined Dec 31, 2017
2,360
Yes I have wall switch for lights and fan but still I have to add 2 switches for each switch. That will increase the number of switches.
All your wall switches need to be SPDT or what is called a 3 way switch. If a triac should short out you could add a single SPST disconnect feeding the AC to the triacs until said triac is replaced.
1613146584396.png
 

sghioto

Joined Dec 31, 2017
2,360
Did you forget? He has already completed the implementation on two way (SPDT) switch.
Wasn't sure what he meant by 2 way switch which I asked about in post #4. In the US a SPDT wall switch is called 3 way.
OK so if all the wall switches are SPDT then what's the problem?
 

strantor

Joined Oct 3, 2010
5,543
In the US a SPDT wall switch is called 3 way.
Agreed. Not sure why all the different terminology. I think the American terminology is wrong. A 3-way would be SP3T (selector) switch.

Wasn't sure what he meant by 2 way switch which I asked about in post #4.
I'm fairly certain that nobody here is talking about SP3T switches, so the discussion hinges on SPST and SPDT. By deduction, He said he wants one-way switches (SPST - the only thing he could be talking about) not two-way (SPDT - the only thing left after eliminating SPST and SPDT).

OK so if all the wall switches are SPDT then what's the problem?
NO CLUE. No adequate explanation was given. Only "I have already completed the implementation on two way switch." Makes no sense. I think we are dealing with one of the members of this committee:
 

Thread Starter

ssd_9

Joined Sep 2, 2020
17
OK so if all the wall switches are SPDT then what's the problem?
In India most of the switches in the house are one way switch, replacing every switch with SPDT is time consuming and will increase the overall cost. for eg. Approx cost of SPDT switch is 30 each and one house has 40 SPST switch so to replace these 40 switches will cost 1200 excluding the efforts and changing the switch boards for different sizes.
 
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