ESP8266 doorbell integration - Page 1
Forum section: electronics / projects

author: howsad4me
author_rank: Newbie
timestamp: September 29, 2016, 06:28:29 pm
content: Hi folks!First time posting, go easy on me. I tried searching the forums, didn't find quite what I was looking for, so going for some help from the experts.My project:Create a wifi enabled doorbell sensor for existing "old school" low-voltage doorbell system. I can integrate it with my home automation. (I'm a software guy, so that part is easier for me).What I'm thinking:- esp8266 board that has a GPIO pin available.- either generate 3.3v from the low-voltage AC or use a battery- use a circuit to probably rectify the doorbell AC and drop the voltage to for an optocoupler to keep the esp8266 GPIO separate from the A/C circuit of the doorbell- I'd like the simple, reliable circuit for ringing the doorbell to primarily stay the way it is, and just "sense" the doorbell push from my esp8266 board. too often the high-tech fails. the doorbell has been working since 1958 when the house was built, just fine. No sense messing with that yet.Questions I have:1. Can I power this from the doorbell circuit itself? I haven't been able to map it out yet, I need someone to push the doorbell while I'm probing with my meter.2. Is there a preferred 3.3v regulator that I should just use? Maybe something like a LM1117 ?3. For sensing the AC to the doorbell, can I get by with a half-wave rectifier and some resistors and capacitors? does this seem like I need a full wave? Or, is there just an even easier way I should do this?Any other feedback is very much welcome. This seems like the simplest usage for the ESP8266 I can use for getting started. Except for the AC sensing part, a simple pushbutton on the GPIO would be easiest and where I'll start once my parts arrive.Thanks!- Greg

author: pelud
author_rank: Regular Contributor
timestamp: September 30, 2016, 12:02:16 am
content: I would first check to see how many wires are going into the doorbell. If there are 4 coming out of the wall, you will probably have no problem powering it, as 2 will likely be the button, and the other 2 will be the transformer. You can then put an ordinary rectifier / filter / regular on the transformer wires for power.You will probably want a switching regular of some sort, as the ESP8266 can draw a lot of current, and the unregulated voltage from the transformer will be relatively high. Perhaps take a look at some of the cheap eBay switching modules.For sensing the AC button press, I would use an ordinaryFOD814opto-coupler with a 1k/0.5W resistor to drive the LED. Then connect the phototransistor's emitter to ground and collector to one of the pins on the ESP8266 that already has (or needs) a pull-up resistor.

author: howsad4me
author_rank: Newbie
timestamp: September 30, 2016, 07:29:59 pm
content: Thanks! Time for me to go look up the datasheet for that opto-coupler. The more hints at useful parts, the more practical my electronics knowledge can get. I have bought 12v->5v dc/dc switching regulator modules before, but haven't checked out the 3.3v options yet. I'm sure they're plentiful.I'm going to get up on a chair (or ladder, I suppose), and see what's coming out of the wall, and then test with my meter and a helper to push the button.If it's only 2 wires, then I have to figure out how to power it. In that case, I'm assuming one lead is from the push button at the front door, and the other would be from the transformer, so that pushing the button completes the circuit. Just an assumption.... I'll know more soon.thanks again!

author: howsad4me
author_rank: Newbie
timestamp: October 04, 2016, 02:38:08 pm
content: Well, I have 4 wires into the doorbell. So that is good news. Now I'm gonna see if I can pick up the FOD814 opto-coupler. I just remembered that I have several little 3.3v/5v power supplies for breadboards, so I'm going to try and make it work with one of those, but probably need to build a rectifier for it out of some diodes. Or, maybe one of those little 4 pin IC rectifiers. I'm not concerned about the size of it right now, i just want to see my circuit work on the bench. I found a wall-wart in my junk bin that is 9V AC, so I'm going to start by working with that. Then I'll "graduate" to the real thing, but will have to be careful of the slightly increased voltage from the doorbell transformer.Quote from: pelud on September 30, 2016, 12:02:16 am