Can I use 230V ac as 12V dc switch

...Ghost... · 18-01-2021 3:54pm #1

Is it OK to use a 100-240V AC light switch as a 12V DC switch?

I want to use a 3 Gang switch to forward, stop, or reverse a motor. I have yet to confirm the operating voltage on the relevant section of the PCB, but it is either 5V or 12V.

My intention is to connect a transformer to the 230V AC supply and connect the switch to the transformer. From there, I would connect the COM lines to the COM on the PCB. I would run lines from each of the 3 switches to the OP,CL and STP on the PCB.

I seen on a boating forum that 230V light switches can be used in a 12V circuit, but wanted to ask here. I have included a crude collage sketch to give you a better idea of my plan.

Additional: The switch will be paired with Alexa, so I will work out schedules or use IFTTT to turn off any button which has been pressed automatically, as the switch is not an auto reset one. I tested the PCB and once the COM line makes a connection with Open, close, or stop...the motor accepts the motor continues this function even when the connection is interrupted. As such, I need the switch to reset itself using smart commands....unless there is another method I don't know about.

18-01-2021 4:39pm

Strictly speaking you shoudl use a switch designed for DC use to swicth DC.
Also when selecting a swicth you also need to state what the current is.

Most light swicthes are rated for around 10A so I am sure you will be ok in this case as the current is far less.

You know that the output from the transformer is AC not DC, right?

What volatge does the Sonoff need to operate? Might be worth checking

...Ghost... · 18-01-2021 4:54pm

2011 wrote: »

Strictly speaking you shoudl use a switch designed for DC use to swicth DC.
Also when selecting a swicth you also need to state what the current is.

Most light swicthes are rated for around 10A so I am sure you will be ok in this case as the current is far less.

You know that the output from the transformer is AC not DC, right?

What volatge does the Sonoff need to operate? Might be worth checking

This is the switch I hope to use ==>https://www.aliexpress.com/item/32956966467.html?spm=a2g0s.9042311.0.0.27424c4dFUkWwr

I'm hoping to put the transformer before the switch, otherwise I would need to reduce the voltage after each switch. I will be using 2 of these switches, so that's 6 buttons.

This is the transformer I was planning to use (AC - DC) ==> https://www.amazon.co.uk/gp/product/B08BTS5FYJ

18-01-2021 8:08pm

I think you need to read my last post carefully.

For a start I can tell you that the Sonoff switch you selected will not work if you supply it at 12 volts. So straight away there is an issue. You need to read the technical specification carefully.

Padre_Pio · 18-01-2021 8:43pm

...Ghost... wrote: »

This is the switch I hope to use ==>https://www.aliexpress.com/item/32956966467.html?spm=a2g0s.9042311.0.0.27424c4dFUkWwr

As 2011 says, this won't work.

Your smart switch has a Live and Neutral input to power the switch circuitry and a Live output to whatever the load is.

It won't work with 12VDC.
You can't even power the switch from your mains and use it to separately switch your 12VDC either.

"Dumb" switches can be used for AC and DC. Typically they have different current ratings though, where max DC current is much lower than AC (this is due to arcing in the switch contacts when the load is disconnected)

4

...Ghost... · 18-01-2021 8:50pm

2011 wrote: »

I think you need to read my last post carefully.

For a start I can tell you that the Sonoff switch you selected will not work if you supply it at 12 volts. So straight away there is an issue. You need to read the technical specification carefully.

I thought as much, but hoped there would be a work around. All I need is a temporary contact to be made when the button is pressed. So, I think I will go for a 6-12V reset push button and look at installing wi-fi relays in each circuit so i can operate the buttons with alexa.

Padre_Pio · 18-01-2021 9:32pm

...Ghost... wrote: »

I thought as much, but hoped there would be a work around. All I need is a temporary contact to be made when the button is pressed. So, I think I will go for a 6-12V reset push button and look at installing wi-fi relays in each circuit so i can operate the buttons with alexa.

Maybe something like this? https://www.amazon.co.uk/eWeLink-Wireless-Automation-Modules-Compatible/dp/B07YFSX32Y

There's plenty of DC wifi switches, but a quick look hasn't turned up one that looks like a wall switch .

...Ghost... · 18-01-2021 11:27pm

Padre_Pio wrote: »

Maybe something like this? https://www.amazon.co.uk/eWeLink-Wireless-Automation-Modules-Compatible/dp/B07YFSX32Y

There's plenty of DC wifi switches, but a quick look hasn't turned up one that looks like a wall switch .

Yeah, I actually have one of those for testing. I don't mind if the end result does not look like a light switch. As long as it is a physical button and I can splice a wifi control module into each function. I had hoped something like the sonoff switch would work, but I knew there would be problems.

I'm thinking something like this for buttons https://www.amazon.co.uk/Self-locking-Latching-Button-Waterproof-Stainless/dp/B07G1591Z6/ref=asc_df_B07G1591Z6/?tag=googshopuk-21&linkCode=df0&hvadid=310746095651&hvpos=&hvnetw=g&hvrand=13047927584391704713&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1007850&hvtargid=pla-594028038213&psc=1

51SYcC4qjnL._AC_SL1001_.jpg

Padre_Pio · 18-01-2021 11:53pm

How about this?
Not so neat, but 4 channels, can connect whatever you want, power off mains or 5-24V, has button for each channel.

http://ewelink.coolkit.cc/?p=458

...Ghost... · 19-01-2021 2:10am

Padre_Pio wrote: »

How about this?
Not so neat, but 4 channels, can connect whatever you want, power off mains or 5-24V, has button for each channel.

http://ewelink.coolkit.cc/?p=458

Cheers for that. Although more expensive (I need 6 buttons, so 2 devices), I think I could work with that.

Padre_Pio · 19-01-2021 2:54am

...Ghost... wrote: »

Cheers for that. Although more expensive (I need 6 buttons, so 2 devices), I think I could work with that.

Remember the relays are double throw, so you have 8 potential outputs. Don't know if that's useful.

...Ghost... · 19-01-2021 3:33pm

Padre_Pio wrote: »

Remember the relays are double throw, so you have 8 potential outputs. Don't know if that's useful.

Unfortunately not. Each relay will only be suitable for one action and will act as a push button to start the process. I have a swing gate motor and a slide gate motor, each with it's own PCB. Each PCB will have Open, Stop and Close functions. Now, I could consider doubling up the relay circuits to open both, stop both and close both, but will have to consider any potential issues in doing that.

As an aside. You reckon the kits on Amazon are just Alibaba stuff? I'm not keen on paying twice the price on Amazon if I don't have to.

Padre_Pio · 19-01-2021 4:34pm

Probably the same stuff. Amazon is just quicker than Ali, and tax is included if you happen to get stung.

Here's a cheaper one from UK.
https://banggood.app.link/42O5hSP1adb

...Ghost... · 19-01-2021 8:13pm

Padre_Pio wrote: »

Probably the same stuff. Amazon is just quicker than Ali, and tax is included if you happen to get stung.

Here's a cheaper one from UK.
https://banggood.app.link/42O5hSP1adb

Ordered. :cool:

Padre_Pio · 19-01-2021 11:50pm

...Ghost... wrote: »

Ordered. :cool:

Let us know how it goes. I'm half thinking of doing something similar

liveandnetural · 20-01-2021 12:03am

to answer the original question. Yes but the must be derated a quick rule of thumb is derate by two thirds so a 10amp ac would drop to 3dc this is as a guide. More in the article below
https://www.nkkswitches.com/pdf/electricalratings.pdf

...Ghost... · 20-01-2021 2:31pm

Padre_Pio wrote: »

Let us know how it goes. I'm half thinking of doing something similar

I'll post back here once I have tested the setup. I'll be powering from the mains and will test 3 relays.

liveandnetural wrote: »

to answer the original question. Yes but the must be derated a quick rule of thumb is derate by two thirds so a 10amp ac would drop to 3dc this is as a guide. More in the article below
https://www.nkkswitches.com/pdf/electricalratings.pdf

Interesting, thanks. Could be useful for future project.

...Ghost... · 29-01-2021 8:04pm

Padre_Pio wrote: »

Let us know how it goes. I'm half thinking of doing something similar

Well, the bad news is that it arrived today and I have been unable to pair this device. As recently as last week I paired a Wi-Fi relay module and got it to do what I wanted. I cannot understand why this product will not pair. I have set each relay into pairing mode (3 fast blinks repeating) and have tried to connect with the following Apps: Ewelink TuyaSmart AmazonAlexa SmartThings I also tried to connect using Amazon Alexa discovery mode and I tried to connect directly to the device with its own Wi-Fi. However, it was not showing a Wi-Fi signal and could not be found.

I've thrown in the towel on this device and will opt for separate Wi-Fi relays.

...Ghost... · 31-01-2021 6:16pm

Tried again today. Did the very same thing. And it worked. Good stuff.

Can I use 230V ac as 12V dc switch

Comments