Sauna Heater Control. Help Needed.

https://www.element14.com/community/servlet/JiveServlet/download/232713-252340/Sauna.png

Here is how everything is wired including 5v power module specs.

System works without issues switching relay only without activating contactor.

https://www.element14.com/community/servlet/JiveServlet/download/232713-252340/Sauna.png

Here is how everything is wired including 5v power module specs.

System works without issues switching relay only without activating contactor.

System works without issues switching relay only without activating contactor.

In that case I suspect that the issue is caused by the mains voltage dropping enough to upset the power supply, and therfore glitching your Yun.

The simpliest thing to try is adding a large capacitor across the 5v.

You'll need a 10,000 uF or more and it can be made from several capacitors.

This acts as a reserviour to hold the 5v up while the supply drops when the mains drop

The second option is to try another power supply, but of a different type (ie not the same type).

Your design is physically limiting your options, and you don't want to comprimise the safety aspects of this build.

A 2 Amp supply would seem to be adequate, but many struggle to provide the full voltage at higher load currents.

With the YUN, relay, and the display, the drop in the 24ov supply is probably enough to cause a reset, of either the Yun or the LCD as you are observing.

You might be able to save a bit by pulling the backlight jumper off temporarily.

It seems that the hardware design of the Yun makes them more susceptible to power than other boards.

https://playground.arduino.cc/Hardware/Yun

You can measure the mains voltage when the 9Kw heater is on.

You may be shocked to see how much it drops to.

Here in NZ the maximum load on a sinlge phase is less ... 32A which equates to 7.6Kw.

Most Spas (similar sized heaters) used dual heaters on seperate phases.

Mark

Hi Mark,

I checked out the Arduino site and they mentioned some of the same issues that Eugene is experiencing. Unlike many of the other Arduino boards the Yun doesn't seem to have its own regulator.

John

Thank you for pointing me to the Yun specs, it seems this board is quite different from another Arduinos.

 

The Yún board does NOT come with a built-in power regulator (as does the Yún Shield). If you are experiencing instability on the WiFi chip, blue LED going off, strange or sudden resets, etc., adding a good regulator will likely solve these issues. The Atheros chip (the WiFipart) seems especially sensitive to transient spikes, ripples, lead inductance and the like when powered from the vIn pin. For example, if you power high current devices (e.g. a high torque servo) on the same power supply as the Yún (obviously not from the board, but on the same input power line) the inductance pulse, spikes or ripples will likely reset the Atheros chip much like pressing the Yún reset button. Placing a small up/down, adjustable dc-dc regulator such as the Pololu S7V8A accompanied by a 33-100uF Electrolytic Cap just before the regulator will most probably solve most of these instability issues. Pololu has a good article on Understanding Destructive LC Voltage Spikes If you are driving high power stuff, feed them before the regulator, always with common ground, of course.

I can order this regulator and try to add it, but I still don't understand why reset doesn't happen when the heater is actually being turned on. I only observed the issue when the board sends a signal to relay to turn off the heater after it's been working for a while. I'm wondering can it be a voltage spike or EMI occurs when contactor disengage contacts that are under high AC load?

It's easier for me to rewire the relay board and use an external phone charger. Please let me know if it would make sense to do it this way?

I still don't understand why reset doesn't happen when the heater is actually being turned on

but I noticed that almost all the time Arduino crashes right after contactor turns off the heater. I haven't seen any issues when contactor turns on the heater.

I hadn't seen these responses when I answered you earlier (cant explain why they didn't show)

This suggests that either the coil of the contactor is causing an issue with a component on the YUN (earlier Pi3 had issues with flash from cameras), or the rise in 240v mains is making the power supply think it's too high and shutting down enough to cause the YUN to glitch.

The capacitor is probably the quicker and easier method (if you have one).

Adding a phone charger will require tying the negative of both sources together, but you could try powering the YUN temporarily with it.

Glitches in power supplies will not show on a meter. You really need an Oscilloscope to see it.

You might be able to test this by manually switching the contactor ON and OFF using a switch.

This would allow more cycling to see if you can eliminate it.

I was a bit surprised by the YUN board power arrangements. It seems a little crude given that these aren't particularily cheep and have a lot going on.

Cheers

Mark

Hi Eugene,

Spikes are not as likely to be generated by a relay or contactor coil when they are being energized as when the power is cut. This is not as serious if the switch is a manual one compared to a solid state switch like a transistor or gate. A lot of situations may be contributing to make your problem. The fact that you have no trouble when the main heater isn't in the circuit suggests that it is a factor. If there are more than one variables in this equation it might be difficult to pin down one cause. If you add a regulator like a 7805 you will have to supply it with at least 8 volts so that it has enough voltage to do its job. The fact that others have had similar issues to yours and the use of a regulator solved the problems is a good indication. Here is a recommended wiring of the LM7805 regulator.

Click on the schematic to enlarge it.

Here is the data sheet for the LM78XX series of regulators:

http://www.farnell.com/datasheets/2298694.pdf?_ga=2.245920388.1679369121.1514241859-118307707.1475274175

John

studioab

I just had another thought to assist in isolating the cause.

If you are able to disconnect the Heater but leave the contactor switching, it will help identify if the contactor col or the load on the mains voltage is causing the issue.

In theory this is simply a matter of disconnecting the load side, and operating the contactor.

Mark

This is what I'm going to try tonight. I'll disconnected heater wires and run the test that turns on and off the contactor every 15 minutes.

Will post results tomorrow.

Thanks.

Results came really fast

I disconnected heater wires from the terminals, and tried to turn on and off contactor without the load. LCD is still glitching but arduino seems to be working fine, because knob is still controlling the relay.

here is the video if you want to see it.

https://photos.app.goo.gl/flRyRDLa82xNVoar1

My understanding is that:

#1 - LCD is glitching because high voltage wires that go to relay are too close to LCD data wires

#2 - I wasn't able to reproduce issue when Arduino crashes or freezes, which I believe is another issue caused by voltage drop or something else, I need to eliminate issue #1 first

My next step is:

- Shorten LCD wires and shield them from AC wires

Please let me know what you think.

Thank you.

LCD is glitching because high voltage wires that go to relay are too close to LCD data wires

I don't think that is the cause.

I still think you have an issue with the supply.

Yes the LCD is glitching, but in theory the YUN should also be locking up.

Is there a way to run the controller off another supply temporarily (and carefully)

Also you haven't answered if you have a large capacitor (it can be higher than 5v) to hang across the 5v supply.

These LCD's have no brownout protection at all, and are susceptible to power.

Mark

So I ended up:

- adding between Vin and gnd 1000 mf / 24v cap (didn't find anything better)

- replacing existing power module with external Nokia 5V 3A phone charger

- removing all AC high voltage wires and relay module from the box

Quick testing shows that LCD is not glitching anymore when quickly turning on and off. I tried it with and without heater connected to contactor.

At this point I will continue using it for a few days to see if the system is working without issues.