How to convert 24V AC to 24V DC to power Sonoff SV

ESPHome
1

I am trying to use a Sonoff SV flashed with ESPHome to control my drive gates. I am planning to locate the Sonoff SV next to my gates and power it via the accessory connector on the existing gate controller. The only problem I have is that the accessory connector outputs 24V AC whilst the Sonoff SV is powered by up to 24V DC. Can anyone advise what I might need to purchase to convert 24V AC to between 5V and 24V DC.

2

You need a bridge rectifier

3

Something like this might work, but be very careful of your grounds:

https://www.amazon.com/SMAKN®-Converter-Voltage-Supply-Waterproof/dp/B00RE6QN4U

2 Likes
4

I tried something like that but the fuse for the accessory connector kept blowing every time I connected it. I could not understand why the input did not have polarity marked.

5

As @devastator says. A bridge rectifier or four diods.
Here is how they work:

https://upload.wikimedia.org/wikipedia/commons/thumb/3/34/Diodebridge-eng.gif/250px-Diodebridge-eng.gif

6

Is a bridge rectifier something that can be purchased pre-assembled?

7

Kind off.
Its still a component.

So soldering is, well not needed but recommended.
You could use screw terminals to connect it.

8

Thanks for all the information, it was just the guidance I needed.

9

You should add a smoothing capacitor on the output also

image

2 Likes
10

If the input is AC, there is no polarity as it alternates.

11

Thanks,

Components have been ordered, just need to get my soldering iron dusted off.

12

OK, so I have had delivery of the components and built a circuit using the following bridge rectifier.

I also added a 1000uF .25V capacitor on the output as recommended. With a multimeter I have measured an input of 24VAC, however I seem to be getting around 35VDC output.

If I take out the capacitor I get 24VDC output but my Sonoff SV does not power up.

Not sure what I am doing wrong.

13

That was just an example showing the need for a smoothing capacitor and not necessarily the correct capacitor for your supply.

14

Thanks. Obviously I need to do a bit more research.

15

can be purchased pre-assembled?

A buck converter

https://www.amazon.com/Converter-2-5-35V-Regulator-Adjustable-Delinx/dp/B08B3T9DX4/ref=pd_di_sccai_1

16

Thanks, I will look into that.

17

This is expected. AC voltage is measured in RMS (root mean square). The actual peak voltages are roughly +34v and -34V. So when you rectify it you get a DC voltage of ~34v.

See also 24VAC tutorial and FAQ for irrigation, security, HVAC and control systems

18

Thanks for everyone’s help. Bought one of these and it works a treat.