Need to control Main AC 240V oven from Arduino

Hello
I need a Triac like device/board to drive a mains 240V oven upto 10A (resistive load).
I have found a few devices/boards that are for light dimming at 2A but I need to control more current. Doesn't matter if device/board is voltage controlled or PWM, i can code arduino to drive either. Anyone know of a high current device/board please let me know.
Many thanks imk

Search for SSD, Solid State Relays. They use an inbuilt triac as well as an Arduino compatible trigger input.
If You buy them from China look for 25 Amp versions. One China Amp is often less then one Imperial Amp, or Metrical...

1 Like

What about a Solid State Relay?

I thought solid state relay were on/off binary devices, i need variable control of the oven power.

PWM is on/off control.

They are, but unlike a mechanical relay, you can use PWM with the solid state relay.

PWM is on/off true.
But it implies the mark/space ratio is the amount of oven power/motor speed/Illumination etc.

Turning a 10 amp load on/off a 980hz is not recommended.

True but i would have to synchronize the PWM frequency to the mains, else it could turn on at the beginning of the mains Sine Wave or at the top of the Sine Wave and result in very poorly regulated power. Which is likely to cause current spikes and noise on the mains. Point of using Triac is they regularly turn on at point in the Sine Wave you want to give you the same amount of power on each cycle.

Think i have found a solution
https://robotdyn.com/catalog/ac-dimmers.html

https://robotdyn.com/ac-dimmer-module-8a-with-ac-dc-power-supply-1-channel-3-3v-5v-logic-ac-110-240v-8a.html

Thanks for the help

Most AC solid state relays use TRIACS which DO NOT WORK with PWM. A TRIAC latches-on until current falls to zero (i.e. at the next AC zero crossing).

If it's not a zero-crossing SSR (which turns-on and off at the zero-crossing) it can be phase-controlled like a light dimmer.

But PWM or "dimming" in not normally used for heating-control. Since you can't heat or cool in a fraction of a second, heating (and cooling) normally switches on & off to maintain temperature. That's how your oven's regular temperature control works, it's how your furnace and air conditioning works, and how your refrigerator works, etc. Often there is some hysteresis so it doesn't switch too quickly or so a regular relay doesn't "chatter".

LarryD

15m

Turning a 10 amp load on/off a 980hz is not recommended.

WHY? Happening on countless motors all over the planet at this very second.
From ebike's to diesel electric trains etc and beyond.
I run the motors in my robots at 12v 1A at 1khz PWM and they work perfectly.
10amps is just bigger motor, I ran 100A PWM motors years ago controlling machine in steel mills in Birmingham.

TRY It, get an incandescent bulb and run it from PWM get warm and is dim red, hotter get orange and full power glows white. That is what PWM is for.

True triac turn off when current goes to zero.
So integrate the PWW to some voltage that turns triac on at same phase angle on each cycle and you have nice smooth power control.

From my experience of Solid State Relays you use them like mechanical relays to just turn on and off.

But dimmers that use triacs integrate the PWM into a voltage that triggers the triac at same part of phase angle on each cycle of the mains hence you get nice smooth power control

How many degrees temperature can your oven change in one millisecond?

PWM would work fine with the solid state relays, but your PWM cycle should probably be at least a 20 second cycle, not in the Hz range. The PWM frequency depends on how close you want to hold the temperature, the oven inertia, and a few other things you need to consider. Using the SSR with zero cross you do not have to worry about phase angle etc when it is on or off for several seconds or more. This also eliminates EMI/RFI noise. Since you are using upto 10A give yourself some cushion and use a 25 or lager SS relay they do not cost that much more.

Perhaps it is easier to provide an example of using a standard SSR to control the temperature.

What has to be done is the on / off time must be multiples or 60Hz or 50Hz in some countries. I'll assume 50 Hz for this suggestion.

define ticks as 1/50 (aka 20 ms)
Your control must be in multiple of "ticks"

i.e.

1 ticks on then 1 ticks off (50% power)
2 ticks on then 1 tick off (2/3 power)
3 ticks on then 2 ticks off ( 3/5 power)
etc

To reduce noise you must monitor the mains for ZC. The ZC switching SSR will do that for you.

Once you have a method of switching the power to the oven, either by chopping up the AC power cycle or by on/off bursts of multiple cycles, how are you actually going to control the temperature ?
Are you going to have some sort of thermostat which simply controls the on/off bursts or are you going to measure the instantaneous temperature and regulate the power delivery accordingly using some sort of PID (proportional integral derivative) controller or similar algorithm?

The point is turning mains 10A on and off at 980Hz is not recommended, generates lots of EMI which will be bad news for everyone in the building as its likely to break-through on every audio device that's mains powered and on AM radios for 100's of metres all around. You'd need to have some good snubbing circuitry to make it tolerable

TRIAC dimmers and motor controllers at 100 or 120Hz are already bad news for EMI, but people are much more tolerant of mains hum/buzz than a 1kHz signal.

For heating you generally use slow PWM (0.1Hz or lower). Preferrably zero-crossing synchronized (some SSRs support this). Thermal timescales are measured more in minutes than milliseconds. For instance standard thermocouple bang-bang control of heaters is effectively slow PWM.

What about all the switch mode power supplies in radios, PC, TV, phone charges, monitor, electric drills, my CNC milling machine, my 3D printer etc etc blah etc. and just about everything we have electrical, they all run at high Hz.

Oh and bytheway this is gadget I am working is NOT about controlling temperature!