Using Wemo as heating boiler switch problem

[Gary Gadget]

Hi, I was thinking of using the Belkin Wemo wifi a/c switch to switch on my central heating boiler. I thought the best way would be to use it to switch a relay on the boilers dc switch circuit. However, I find the circuit has 32V and all the relays I find are rated up to on 30v dc. Essentially, I want to just close the circuit on the boiler from the Wemo or some other wifi means. Alternative suggestions welcome.
Can somoene offer me some advice please as I am a novice with these things?
Regards

 

[JonSea]

The Wemo needs to switch the DC control circuit. The Wemo can switch a relay with a line-volage coil (120v or 240v depending on where you are), and the relay contacts switch the boiler's DC circuit, possibly in place of the thermostat.

A safer way of doing this would be to have the Wemo switch a 5 volt wall-wart on and off, and use its 5v output to control a relay with a 5v coil. You can buy a 5v relay on a circuit board complete with terminal blocks on ebay cheaper than you can buy the parts so this route gives you a safe, easy to use solution at low cost.

I'll draw a sketch if you'd like.

 

[Gary Gadget]

Thats what I planned to do but the relays only rated for 30v dc. I have purchased a relay module to be triggered with 5v. So I would be very grateful for a sketch please. It sounds like I had the same idea as you but not sure of the relay rating.

 

[JonSea]

Ahhh... I thought you meant to have the relay coil in the DC wiring, not the contacts. The contacts should be fine switching the slightly higher voltage, ince the current will not be high.

The sketch shows how I might do it. Note the relay board connections may not be in the order shown.

Connect 5 volts DC to the + and common/ground terminals on the board. Also connect the input terminal to ground - most of these boards require the input to be low to switch on, but some may require the input be connected to +5 to be on.

If you want to remotely switch the boiler on, overriding the thermostat, connect the relay common terminal and the NO (normally open) terminal across the thermostat terminals. Set the thermostat temperature to the minimum temperature you want and switch the Wemo on when you want it warmer.

 

[Gary Gadget]

Thanks for your advice Jon I will try it out. Looks like I needed the reassurance to do it this way with the relay having 30vdc stamped on it! Glad you understood my plan. I may have the courage to try a method other than using Wemo after I`ve got this working!
By the way, it's just a timer, no thermostat on this system presently.
I could buy a wifi timer but it`s just the challenge to build my own kit. I want to be able to turn it on when returning to UK from holiday in the States to warm the place up after it being off for a while, or should I say, it`s the novelty of being able to.
Thanks again.

 

[JonSea]

There is an alternative that I should mention. I've been using Sonoff WiFi remote control modules from iTead. The same principle as the Wemo, at a fraction of the cost. They have been busy developing different modules, and the work great. So far, these only control a relay, so no lamp dimming, but for simple on/off control, they are awesome. They work with a cell phone app from anywhere you can access internet.

The first module they made is designed to control lamps or appliances and splices into the line cord. I've been splicing them into extension cords so I don't have damage the lamp's line cord. Less than $5 for this module!

But there's a better choice for what you're trying to do. It's called the inching/self-locking module. Translating into English, this module can either briefly close the relay when activated (think garage door controller) or operate as an off/on relay. The app shows if it's on or off. Best part is, this board controls a relay and gives you access to the terminals. Connect a 5 volt supply and you're in business. It costs $5.38 for the 5 volt version. See the webpage here.

 

[Gary Gadget]

Excellent, thanks for this. I have been looking for something like these. I will let you know how I get on. I really appreciate the help you have given.
Regards

 

[JonSea]

The Sonoffs have worked really well for me. Sometimes, they can be a little picky about initially associating (which I blame on our router) but after that they have been extremely reliable, including coming back on line after power failures.

There has been a lot of development of different modules and the app software is frequently updated. We have about a dozen in use now and couldn't be happier with the system.

 

[Gary Gadget]

Hi Jon,
I got delivery of a differen relay module (awaiting one like you suggested) but so far have not got it to work. I get power to it but it doesnt switch. It is for an Arduino but I didnt think it would matter if I gave 5v to the input too.
Need a little more time to tinker with it. I used a jumper to join both IN & COM together. Any tips?
I have this HeroNeo® New 1 Channel H/L Level Trigger Optocoupler Relay Module for Arduino 5V https://www.amazon.co.uk/dp/B00JE4R6FU/ref=cm_sw_r_cp_tai_NgOfyb17EBTAT
Gary

 

[JonSea]

Connect +5 and ground and then try IN to ground or +5 .....one of them should activate the relay.

 

[Gary Gadget]

Will do thanks

 

[Gary Gadget]

Success thanks, will keep you posted.

 

[Gary Gadget]

I got a Jog self-lock Smart WiFi Wireless Switch Relay Module DC 5V-12V by APP Control, as you recommended so just looking for a housing to stick it on the wall that is clear somI can see the LED and maybe operate the manual switch. Works well though so thanks again for your pointers. I have also now received delivery of a Sonoff switch too so having fun with these different types thanks.

 

[Gary Gadget]

I've been trialling both relay modules and the Wemo and all work great. Presently have the Wemo triggering a relay module so my wife can still override the system with the convenient on off button it has.
I am wanting to make my own faceplate to control the switch with just the iTead module but need a way to allow both wifi and manual switch operation. I dont fancy soldering across the switch but cannot think of a satisfactory way to allow two-way control with blocking the other. I looked at latched relay circuits thinking this is possible. i.e. I want one manual switch to turn on/off, without either this or the wifi switch being compromised. Will I have to us a programmable solution or can this be done with circuit design using standard components?
Essentially it will work just like the Wemo switch does.
Thanks for any help.
Gary

 

[JonSea]

The Sonoff modules (well, many of them) have a push button switch for local operation. Most of my modules are in tough-to-reach places...the manual control may or may not work for you.

One way to allow manual auto remote control would be like "3-way" light switches - I don't know if that translates outside the US....like light switches at either end of a hallway where both switches can turn the light on or off. You would need a SPDT relay and a SPDT switch to make this work. The trouble with this approach is the which way is "on" depends on the position of the other end. Sometimes, "relay on" turns on the boiler and sometimes "relay off" turns on the boiler depending on the position of the switch.

 

[Gary Gadget]

Thanks for that. Think I could end up using my Arduino, or leaving the Wemo in place. The Wemo works exactly as I want but the challenge is to reduce the cost down and have my own faceplate maybe including an LCD display.
I will have a ponder on what you suggest.

 

[Gary Gadget]

I'll use LED indicator for your suggestion possibly. Have you a rough schematic in mind?

 

[JonSea]

This is what I was thinking. If you use a SPDT (single pole, double throw) switch and a SPDT relay wired up like this, either the switch or the relay can turn the circuit on or off. If both are up or both are down, the circuit is on. If one is up and the other down, the circuit is off.

The problem with this arrangement is you must be able to see some indication if the load is on or off. The relay may be energized or de-energized to turn the circuit on, depending on the state of the state. Likewise, the switch may be up or down to turn the circuit on depending on the state of the relay.

 

[Dr_Doggy]

Hi Gary,
If you are interested in all this stuff check out smart things, there are lots of brands and manufactures out there, I have seen thermostats too! At the end of day pre-made is cheaper and usually well thought out, but not as fun & flexible as hobby builds.