#222 

Hi Ralph - I recall mentioning something like this to you previously, possibly in an email not sure. But I've just had my second YT cull after a further few years as I had subscribed to way too many channels, and once again your channel remains securely on my sub keep list. Haven't watched many of your videos over this time as I've been involved in several other things (e.g. my iOS and Android app development and releases etc) but I will scroll through and catch up. Have watched this one though, and very interesting it is too. keep well Ralph, keep the water away from those bins, and keep up the great work. John.

Welcome BACK, Mr. Bacon :)

Thank you very much for very useful topics

Also, install the relay inside your heater. That way you run low-voltage wires from your microcontroller box. Cheers!

Very informative video

cool :) waiting for the next one :)

Big Clive has done a number of videos on both capacitive and resistive power supplies. While I have no reason to think he's pulling our collective legs, thanks for producing that Microchip tech note to verify. As for driving the relay, I'd stick with a single supply. Coil source at 5v rail, drains to ground through an N-channel FET (and current-limiting resistor). Programmatic logic lines up "high/low" with "on/off", so no "active low" logic to keep straight. You mentioned it in the video, but it bears repeating: don't forget the reverse-biased snubber diode across the relay coil. 😁👍

I certainly wouldn't use any capacitive power supply on something I was likely to be plugging into my laptop! A few years back I was building a box for a friend to switch audio sources to several different speakers and soundbars and had to power the microcontroller in it, and instead I took the PCB out of a USB charger and fixed it to my board. I had several of them and one I stripped apart to check how safe they were, and they were good enough, the only reason they I didn't use them for their intended purpose was that the plastic case had a tendency to fall apart, not good in the living room! However when built into something perfectly safe, and quite a bit cheaper than the module you show. However I would advise caution with cheap chargers from eBay or Ali Express unless you are sure about the quality of the electronics - you only need to watch a few "Diode gone wild" videos to know why! But re-purposing a USB charger and building it into a project is a valid prospect if you take a little care. You can also get very small 5v and 12v switching power supply modules quite cheaply (like the one you showed I suppose!).

Use a solid state relay to control the heater.

I love the design process, my suggestion would be to make the relay replaceable, give it its own little PCB with four screw terminals and maybe add some mounting holes. Then design a little square cut out on the main PCB (it is large enough) so you can fit a spare relay (already soldered on its little PCB) in there.

Don't forget OTA code to make it easy to upgrade. Great practical project!

perfect app to replace relay with SSR. Also if you connect to bimetal switch set to high it would serve as an overheat safety.

I had used Hy-Link a lot and pretty much reliable, For the relay I would stick to 5v and add a transistor, there is 16Amp version not much larger the one you got. I played with transformerless a lot in the past, I know it is dangerous, you heard of Sonoff? They used tranformerless.

Interesting project Ralph. Maybe include a sensor to sense when you've turned off your kill-switch, or turned off the lights when leaving you workshop.

Great project Ralph, when your works shop is done how about a decent headphone amp ?....cheer.

My first thought was to add a two pole contactor to your existing kill switch. No bells but you could also control the kill switch plus contactor with this esp32 circuit. Or the one esp control both independently, and add the bells and whistles in software.

Hi Ralph, just going through some of your older videos, and I noticed on this one you showed the Home Alone project. Completely unrelated to *this* video, but I wondered how you found the PIR detector and whether it ever suffered from false triggers, which I get all the time on a project using a larger PIR. I wondered if you were using any additional circuitry rather than just reading the PIR output directly, and if so is there a video on it ? I've got some of the PIR ones you have used, and they work fine on the breadboard but don't want to start my next PCB design until I know if it's going to work in a real project. TIA

Since you mentioned your "home alone" project, with its PIR, I was wondering if it'd be worth including one -- for even more control options? Just a thought.

Any thought about solid state relays or are they not powerful enough? Cheers

Hi Ralph, If I understand your control scheme proposal (which is by no means certain), you want it to -) Turn on the power to the heater when the "power kill" switch at the door is ON (meaning you're in the shop) AND -) The temperature is less than some preset comfort level UNLESS -) you override it with the override switch OR -) it's overridden by the phone app OR -) the temperature is less than 9 degrees AND it's the middle of the night If I've got the hierarchy right there, then I think you've just traded the "I forgot to turn off the heater when I left the shop" problem for two problems: an "I forgot to turn off the override toggle switch" problem; and an "I forgot to turn off the phone app override" problem. To get around that, I'd suggest that both overrides should start a timer that allows the heater to run for a set time. Whether that's 15 minutes or 2 hours probably depends more on how long it takes to heat the shop than anything else, but you really need them to be momentary switches, and time limited. I'm not sure how that would work with your phone app? If you're writing your own, then just do it. If you're piggy-backing on an existing app's capabilities, it might be more difficult. and BTW - I understand why you're doing it your way... You've got all these wireless microcontroller hammers sitting around, and when you've got a hammer, everything looks like a nail ;) But the heartbeat doesn't need to be wireless, and doesn't need a microcontroller. There must be dozens of ways to skin that particular cat! For instance, you could use a 555 timer to generate your heartbeat pulse, which you could then use to activate one of your many spare relays to pull a line low. Or the 555 could light up an LED that you detect using a phototransistor or even an LDR. Not to mention (since others have already done so) a PIR as an occupancy sensor.

One thing that occurs to me is the potential for the override switch to scupper the project. If you turn on the heater using your phone but for some reason you don't go to the workshop, you're back where you started, wasting power/money. A possible solution is to have a time limit on the override such that it turns off again if it doesn't detect the heartbeat signal after say 30 minutes.

Be very careful with those Hi-link and similar down converters. Looking at the spec it does not say they are mains isolated. Would be an interesting test. I've only found one from Amazon ( EASY POWER) that actually gives an isolation figure of 1kv. They may all do the job until you plug in your, soon to be magic smoke free, USB connector. Keep em coming :)

An SSR might be more reliable than those smaller relays, but they also tend to be a bit larger and space here is a concern. But one possibility that I believe exist with both the 8266 or 32 is future integration into Home Assistant if you ever decide to centralize all of your 'smart' devices for easier control. Looking forward to seeing how this journey ends. I've been playing around with a heat controller myself, but it isn't as smart and only dealt with a 60x45x60 cm volume. Sadly, I don't think the PTC heaters I was playing with are sufficient to get the job done in a reasonable amount of time with where I wanted to mount them.

Just a thought, maybe you could use an opto coupler (triac or similar) to drive a mains relay/triac to avoid loading the CPU power supply ?

Great project! I am doing something quite similar to control the hot water pump that circulates the water around my house. I have tried using the HiLink 5V/5W power supply and found that I got brown outs on the ESP32 regularly, especially when connecting to the WiFi due to current surges from the WiFi function. I know that you are not planning to use WiFi in this project, but just a heads up that the 1A current isn't quite accurate. I have now used a 12V HiLink to power the ESP32 directly, and an LDO (Mini 360) to create a 5V power rail to power the other componets on my pcb. That seems to work a lot better and is more reliable. No more brownouts!

You can make a "Poor Man's" isolation transformer by connecting two (small) transformers "back-to-back" with their (similar) secondary windings, thus providing double isolation to the second transformer mains voltage terminals. Grounding one side of the intermediate wingings is a bullet-proof way of preventing mains voltage break-through.

Have you taken into account thermal runaway due to a faulty temp sensor that would indicate a low temp constantly ,perhaps there's an overtemp thermal breaker built into the heater already?

Friday and Bacon time :-). Annyway you should use a Solidstate relay, and control your heater using a PI controler (D not needed) using PWM (as low frequensy as you can get on the ESP is perfect). Like this you get perfect temperature control, none of this on off rubish. Within profesional building automation, this is a quite normal solution, and has been around since i started back in the early 90s. I recently buildt myself an inline electric water heater for my underfloor heating system, using a 3phase 9kw heater and two sollidstate relays, offcource with overheating thermostats, flow swithc and so on, not that you need any of this since you just use the buildt in thermostat as an overheat thermostat. Annyway it works just perfect, communicating with my Homeautomation system using MQTT, and regulates the temperature just perfect, within 0.05°K of setpoint.

Perhaps the addition of a Watchdog Timer - as per your video 194 - to avoid a processor crash leaving the heater powered ON ?

Need to program Arduino (mini) on mains potential? Please consider this isolated serial programmer on Thingiverse 4911765.

Perhaps the rule of KISS is applicable here?

Whopping big isolation transformer? :) I guess it is for arduinos. I used to do lots of power electronics stuff and I have a 3kVA with 15A variac and a secondary 400VA isolation transformer. I think you're on the track. Tiny psu modules are handy and safe. Make sure to fuse it. I would be fine with a capasitive dropper too. I tend to update software OTA and in that case you only need to program it once (when it is not connected to mains). I find it unlikely to need scoping for such a simple circuit. For something like full ESP32 current (200mA or so) capasitive droppers are not that small, probably larger than a tiny psu module.

Nice project, just as usual @ 24:30-ish you said -give some safety, and you turned all blue in the face, is that a coincidence. fear or are you just sitting on something you shouldn't? LOL you could put an opto-coupler in front of your relay or maybe replace it with an opto-triac, i think you done that before with Zero crossing detection

Did you ever consider a solid state relay?

Use relay or ssr then these ssr use to controll the magnatic swtich the magnatic switch is some high price but its good for controll the high power device u controll the swith with ssr or relay cuz its coil need 220v ...

would go for a solid state relay , low actuating current , no contact sparking

i was thinking of an esp32 washing machine solution to replace the factory circuit . i m still thinking it but i bought a new washing machine :)

Ditch the DHT series of temp sensors , they are crap - try the newer SHT30 or SHT40 units . The DS18b20 is reliable , reasonably accurate and can run on one wire .

OK so you are not planning on using the internal T-stat. If it is a low voltage T-stat inside the heater why not just replace that with a relay. Then your relay does not handle the mains heater current.

How the isolating transformer provides improved safety, always mystifies me. Its input is the same as its output, so how is 230V at the input somehow safer than the 230V on its output? Surely my body can’t tell the difference? I suspect the answer is obvious, but not to me.

A simple timer socket would work

why not ignore the heartbeat sensor, and set up times for it to work and with a humidity sensor as well and a lower temp after a certain time at night to keep a steady dry temperature, not sure I would trust a chinese relay to operate 2KW switching, maybe a contactor or solid state relay

All fancy air coller hair dryer hair straight and lot of other thing use cap droper ......

A heartbeat monitor is a smart decision. If you get murdered in your workshop, CSI won't get fooled by the temperature

Tasmota way easier

Don't really need an RTC if it's on your network. Control the detailed functionality via e.g. NodeRed, not local code and configuration. It doesn't take continuous chatter if you communicate only changes of setpoints when they occur, until they are acknowledged. Indeed there is scope for sleeping. There's no reason not to switch a 5V relay via a MOSFET. You manage your WiFi transmission so that it doesn't happen until the relay has switched the MOSFET gate to open "slowly" by placing a small capacitor on it.