Ideal Halo Lite thermostat

[Jarsudsco1]

Hi, I recently bought an Ideal Halo Lite Thermostat (through Ebay, although it was sold as and looks new). I want to learn about Opentherm so I've built a "hub" based on the readily available interface circuits. The slave and master interfaces appear to talk to each other quite happily but when I connect the Halo Lite the hub reports (via an Arduino) a series of "T..." messages from the thermostat and responds with "B..." messages. So it looks like the thermostat is working to some extent but the display shows nothing at all so I have no idea what's going on.

Any suggestions would be welcome.

 

[RandomGrinch]

Hi,

Sorry, this might not be of any help, and I may be very wrong!

If I understand correctly, when you connect the Halo lite thermostat, you get absolutely no signs of life from the display?
Have you ever seen the display come to life?

I'm afraid I don't know the specifics of the Halo Lite and this is a total guess!
However, it seems to me, as if your 'hub' may not be delivering enough power through the opentherm cable, to enable the Halo to operate?
There may be sufficient power to enable the IC's to function; hence some communication, but not enough for a more power hungry display?

Keep at it though, this sounds like an interesting project

 

[Jarsudsco1]

@RandomGrinch - thanks for your reply. I had thought about the power level but I was under the impression the Opentherm physical interfaces were fairly standard and that all devices were compatible. I was wondering if anyone was aware of any incompatible devices or some that needed none standard interfaces or maybe even some specific messaging in order to start up.

Your suggestion is still a good place to start, I will try and check the various voltage and current levels today. Thanks again.

Other suggestions from anyone are also welcome.

 

[RandomGrinch]

From Opentherm wiki :

"A controller from manufacturer A can in principle be used to control a boiler from manufacturer B. However, OpenTherm controllers and boilers do not in fact always work properly together. The OpenTherm standard comprises a number of optional features and some devices may include manufacturer-specific features. The presence or absence of such features may impair compatibility with other OpenTherm devices"

 

[Jarsudsco1]

@RandomGrinch - Lol, thank you so much for that - gotta love standards, eh?

I wonder how anyone would go about checking that a particular control device - like my Halo Lite, isn't faulty, if they don't have a compatible boiler to connect it to...

 

[RandomGrinch]

Non-compliance and incompatibility with standards? ....No, not us!
We've just added 'features' and 'enhancements'!

 

[nitrochicken]

Hi Jarsudsco1

Sorry to bring up a 12 month old thread, but did you ever figure this out? I just bought the same thermostat hoping to connect it to a vokera boiler that supports opentherm but the device doesn't seem to power up?

Thanks

Dale