Rick's b.log - entry 2025/02/02

Heater modification

On Saturday morning, I put my hand on the radiator and discovered it was warm. It had been on all night.

Not a big deal, as it was on low heat so I maybe only lost a euro or two lightly heating a room I'm not in... but still...

This happened, and not the first time, due to the construction of the heater. It's an inexpensive Lidl radiator, and as you can see from this photo, the orange neon is lit when the heater is off.

Yup, we have a situation where glowy-light means...nothing much.

In order to understand why this has happened, and why the neon is not an indicator of whether or not the heater is actually on, let's void the guarantee and take a look inside.

There's a pleasing amount of attention to safety here.

Here's a badly drawn schematic.

I've left out the Earth as it isn't relevant to what I'm doing here.

So, the power comes in. The Live goes up to a safety cutout mounted to the radiator to prevent it getting too hot. From there it goes to a tilt switch, so the radiator will turn itself off if it gets knocked over. It's a weighted ball on a stick that presses a microswitch.
From there, Live passes to the thermostat to control whether or not a suitable temperature has been reached.
It then passes to the level selector switch. As this is the last point in which there is a unique Live, the indiator neon taps off here (the other side of the neon being connected to Neutral).
The level selector allows one to choose between Off, Low, Medium, or High.
For Low the Live goes to heater 1, which if I recall is about 600W.
For Medium the Live goes to heater 2, which if I recall is about 900W.
For High the Live goes to both heaters, which will be 1500W.

The problem here is, thus, that the neon actually says whether or not the heater would work (not overheated, not tilted, thermostat reading low) and not whether or not any heater actually is working.

The solution to this is to absolutely void the warranty by making a modification to show if/what heaters are active. This is dead simple, simply pop an indicator in between the Live going to each element and Neutral.

This took about ten minutes and cost a couple of euros in parts.

Here that is in schematic form.

A simple modification, really.

Here's a photo of the radiator on medium heat, so only the lower indicator is illuminated.

That's better. ☺

You'll have noticed that the indicators are really bright, so no excuse for leaving the thing on any more.

Almost cosy

Here is the latest code revision being tested.

This is all being done under Android.

So rather than just turning an LED on and off to show the state of the "open" switch, this version will connect to my AP (and handle reconnection if the signal drops out), get the current time, set up a webserver (and handle it), and continually check the state of the switch.

When asked, it'll throw back a very simple page like:

Very basic at the mo'.

I have included the basics for SPFFS, so the next time I work on it, it should be able to maintain a rotating list of the last n open/close actions, stored on the internal flash. Once that has been done, and the web server able to report them on request, that'll be the code pretty much done.

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Rob, 2nd February 2025, 20:53

But.. If the room is warm enough at the point you glance at the heater, all the lights will be off, even if it's switched on. Maybe you could wire the thermostat on the far side of the heaters, and the common of the new indicators beyond it. That way the indicators should be always on when heat is selected.

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