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reverse polarity on relay

by CCLONDON on ‎10-03-2017 04:14 AM

I live on a boat and have just installed a wemo maker relay to remotely switch on my webasto calorifier (furness) via my phone. The problem I have is that the Wemo Maker is showing "'on" when the furness is switched off and it shows "off" when the furness is on. Any ideas on how I can reverse this?

thanks

Chris

Comments
by WEMO Maker Inventor
on ‎10-03-2017 08:53 AM

Are you using the relay (switch) on the maker to control the furnace?  If it's through a secondary relay (and it probably should be) you could change the wiring to control how the wemo relay turns that remote relay on or off.  It does sound like it's wired a bit strangely already if turning the wemo relay off turns the remote relay on, you may want to revisit what you've done.  I'd need to know more about how it's wired to offer a suggestion.

 

If you mean the Maker sensor is reporting an inverted state you'd need to change that with wiring too but it's probably harder.  I don't think there's a way to change it in the app.

 

 

by CCLONDON
on ‎10-03-2017 09:11 AM
Thanks Mike. There are two cables coming from the Furness designed for a thermostat. Since I don’t have one, I’ve used these to go straight into the relay sockets on the wemo maker.
I checked the help desk and they confirmed I couldn’t change the setting in the app so I think I’ll have to add another component between the Furness and the wemo maker to inverse the +ive -ive .
It’s all working - just in reverse. At one level is just confusing but it also means I can’t really use the scheduling function which would be a real boon.
by WEMO Maker Inventor
on ‎10-03-2017 11:16 AM

So the thermostat closes the relay when it cools off, that makes sense, and it's not much power so probably safe.

 

I guess you could reverse schedule using "on" times to suppress the heater.

 

Maybe one thing to mention - if there's a power interruption the maker will come back up as "off" which means the heater would turn on and you might not know.

 

So an external relay might be a good idea just to prevent that. 5V relay boards are < $2 from ebay and work well, but you might want to pick up a cheap USB charger at the same time to power it 'cause the Maker probably can't power it through it's +5 line.  The specs claim it can supply 100ma but I've found it's more like 50-60ma.  Belkin hasn't bothered to check or update their specs, and since they don't sell it anymore probably never will.  A relay usually needs about 70-90mA to run when activated.

by CCLONDON
on ‎10-03-2017 12:52 PM
thanks Mike. Yes I’ve noticed that it defaults to on when I unplug the wemo. Thanks for the recommendation on the relay boards - I’ve had a look but just wanted to check that this overcomes the “default-on” mode but won’t reverse the signal. Is that correct?
by WEMO Maker Inventor
on ‎10-03-2017 01:47 PM

It'll reverse the signal too.  Most relays have normally open (NO) and many have a normally closed (NC) terminal (except for the maker which is the problem...).  You'll wire the thermostat wires to the NO and COM connections of the external relay so it's only connected when the maker is ON.

 

Wire +5 from the wemo to one Maker R, and from the other Maker R to the external relay IN.  The external relay will need +5/GND from somewhere (maybe the maker but maybe not) and you need to tie the Maker GND and external relay GND together.

 

Actually I said the thermostat action wrong in my earlier email - sounds like it needs to be active to turn the heater off, and so when it heats up it shorts the two lines.  Bit odd, but I guess what you do with no thermostat (or maker) is connect the two inputs together?

by CCLONDON
on ‎10-03-2017 02:52 PM
Thanks Mike - you’ve been great. Much appreciated.
Best wishes
Chris
by nuning
on ‎10-04-2017 01:25 AM
 
 
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