Detect if an LED is lit ?Is there a small battery-powered light sensor, sensitive enough to pick up an LED? (UK)

Here is my scenario… I have a boiler that is not ‘smart’/connected and is driving hydronic UFH. In the en suite is a dual energy towel rail. You must be careful not to have the electric element on if the central heating is on. Each room has it’s own thermostat - so the heating may/may not be on. The boiler has an LED that is lit if the central heating is on. If I could detect the LED, then I could have ST control a relay that could turn on the electric element if the heating was off.

Is anybody aware of a small light sensor out there (battery powered) that would do the job?

Many are using this device on washers and dryers to know they have completed cycle. Might work for you. Website also has a cheaper “open box” one too

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thank you for the tip… though apparently not available in the UK for some reason (not even Amazon…)

This comment would scare the hell out of me. I would never trust Smartthings in this circumstance. It’s just not reliable enough.


is that a comment on home automation in general? Or Smartthings specifically?

Smartthings specifically


Though apparently not available in the UK for some reason

Z wave is on different frequencies in different regions, in order to keep from interfering with local first responder communication networks. Similar to how mobile phones are different in different regions.

The Z wave frequency cannot be changed after the device is manufactured, and it is up to each company which regions they choose to manufacture models for. Homeseer only makes devices on the US frequency. Some companies only make devices on the UK frequency. Some companies, like Aeotec, make different models for the different regions.

So the reason you cannot find that particular device for import into the UK is that it is not made on the UK frequency (and would not work with a smartthings UK model hub).

To be honest, a heating system is a really expensive and dangerous equipment to skrew it up.

If you overheat the system, it can explode. If you do not turn it on when the temperature drops below 0 Celsius, then you can burst the pipes.

Generally SmartThings as a cloud based system, it is not reliable enough to handle this kind of scenarios. (Just look at the status page how many outages has happened during the past few months.) You rely on SmartThings cloud solution at the first level, then you rely on your network equipment, and then your internet provider, and last but not least on your electricity provider as well (just think of short power outages). It is definitely not reliable enough to control a heating system, which requires a failsafe.

I know it is the most expensive solution, but it is indeed to have the right controller connected to your boiler. One which can handle your central heating boiler and your electric towel rail at the same time. I just guess, but when you built/bought your house and the electric towel rail was fitted, the idea was to get the towel dry during spring and autumn, when you do not use the central heating. So, you physically switch / plug it to be on or off. It wasn’t really designed for mixed mode I guess. If it was, then you should have a wire running from the towel rail’s electric heater to your boiler or to your central heating controller thermostat. Because that’s where the control should be centralized.

I have a heating system, which consist a gas boiler, a circuit of radiators, a circuit of underfloor heating, a circuit of domestic hot water, and another heat source, a fireplace with a built in water tank.
The gas boiler is controlled by Viesmann controller, I cannot remember which model, and the fire place has a temperature sensor in the chimey/or on the water tank, I am not sure, which reads the temperature. The temperature sensor is connected to a controller, which turns some pumps on the selected circuits and forces the boiler to shut off when the fireplace is on. All wired from the fireplace to the cellar, where the boiler and pumps are. That has a few level of failsafes, but I can still overheat the water in the circuit, if I put too much wood on the fireplace. And to be honest, I would never think to put it on any automation system, which depends on the internet or any overcomplicated solution.

Just my 2 cents…

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As others have said, the smartthings platform is simply not fit to purpose for this kind of safety issue. It might randomly turn on, turn off, or fail to give you information. I personally don’t connect anything to smartthings that isn’t safe running for 24 hours unattended. Or being off for that long.

That’s not just community opinion: the company says so themselves in their product usage guidelines:

Data accuracy and consistency from SmartThings sensors, including those provided by SmartThings directly, resold by SmartThings, or supported by SmartThings, is not guaranteed. Therefore, you should not rely on that data for any use that impacts health, safety, security, property or financial interests.

So again as others have said it’s best to look for a different solution for this use case.

You’ll note that the American device which was suggested is primarily used for washers and dryers where there’s no safety issue if the notification fails, it’s just a convenience use case.

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Ok - advice noted. Would the same apply to Nest? Or is that a general rule for home automation currently? I am just starting on the home automation journey - so I am platform agnostic. ST appeals because it is protocol agnostic - but if that comes at the cost of reliability, then I would go to an alternative platform.

Smartthings has multiple specific reliability issues. For one thing, you can neither defer nor deny updates, which historically have happened at least once a month and then will take your hub off-line. Maybe it’s only for a minute or so, but it’s often longer, and of course if there’s a problem it can be much worse than that. The problems don’t happen to everybody every time, but they do happen to some people. :disappointed_relieved:

Smartthings is also primarily a cloud-based system, which adds additional points of vulnerability.

And historically smartthings has from time to time made backend changes without documenting or announcing them which then caused some loss of functionality for some or even all customers. :scream:

So advanced users choose the smartthings platform for its versatility, not its reliability.

There are definitely alternative platforms which are much more reliable, but they may have less versatility and support less rules complexity. So it just comes down to your own needs and preferences.

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