ESP8266 + Relay from 14V AC

Hello together, this is my first post i hope i dont do something wrong :slight_smile:

Warning, Noob question ahead!

I'm planning to control my front door with an ESP8266. To do this I want to switch the door buzzer from my intercom (HT611-01) via a relay.

The ESP and relay should be powered directly from the intercom (to avoid a battery, external power source). The problem is, the intercom only offers 14V AC.

Is it possible to power the ESP + Relay with a full bridge rectifier and an adjustable DC/DC converter? Do I need a smoothing cap? If so, how big should it be?

Will I face problems powering the relay or running my circuit in parallel? (too high current, voltage dips, etc...)
Is there an easier solution?

so the source is 14vac, but how manny amps can it supply?

another consideration is how much power the arduino and components draw. you can look at their respective datashets to figure that out.

as to the problem of converting the 14vac to 5vdc you can probably use a module like this (not this one):

they typically cost 6-10$ and are easyer than trying to create your own solution. just look around for the correct type you need.

hope this helps!

Yea, you could use this one though.

Thanks for the answers. The module looks good!

I couldnt find any information about the amperage on the datasheet of the intercom. But i guess it should bei enough?

The ESP with WiFi on consumes 67mA (435mA Spikes). The relay shouldnt draw that much either?

What are the risks? Killing the transformer? Is it more likely to break instantly or over time?

a typical relay when triggered might draw at most 150mA, so with your other device only drawing 435mA peak, your entire circuit at peak might draw less than an amp, so you probably would be fine.

could you take a picture of the 14vac transformer? based on the size we can guess on how many amps it can supply.

the risks depend on how the transformer system is set up. it might (Almost definitely wont) fry the transformer, but it probably would blow a fuse or break over time. but as previously mentioned, you would probably be fine as the transformer is probably big enough, and your system has 'PEAKS" of current draw, not "CONSTANT" current draw.

hope this helps

Next concern might be with the “door buzzer” aka unshieled electromagnet “confusing” your esp8286 when activated.