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RobotDyn AC Light Dimmer Module
Right, what I suggested above is actually building a DIY SSR, without a case.
Electrical it's the same thing, but already done by a factory, so supposedly better and safer.
A SSR is the triac, in a proper case, with terminal screws designed for the right load.
The pulses from Arduino are the same wire that goes to dimmer board.


progen wrote:


renatoa wrote:

The PCB trace aren't capable of much more than 8-10 Amps, for a reasonable temperature increase, so you should consider cleaning the varnish and thickening them with solder.
Or soldering an additional wire from the triac pads to the terminals block.
Or, the best approach, separate the circuits completely into the power side: the triac on heatsink, fitted to power terminals accurately designed for this load, and the command side, i.e. the dimmer board used for ZCD and triac control via two tiny wires.
changing completely the layout to another more optimal approach, by splitting the circuits in

I think I'll stick to my initial plan of getting the Arduino to fire off pulses to the SSR then. Sounds safer to me.

Maybe one solution that might help you:

I am using the AC Dimmer Module to dim a 1400W halogen heating lamp in an Air-Fryer (I posted the Mod here in the forum). But I am not directly dimming it: the air-fryer already contains a TRIAC with heatsink on its PCB which is also build for higher currents than the TRIAC on the Module. I found out that a small cable coming from the LCD of the machine was actually responsible for turning theTRIAC of the heating lamp on and off (so the air-fryer normally just switches between full and no power). Unfortunately, this cable was AC 220V.

So I used the AC Dimmer module to dim/PWM this low current gating line. And with this I get nice dimming of the second TRIAC and the heating lamp.

So you could use second TRIAC capable of handling high currents and gate it with a connection that you dim using the AC Dimmer Module (which already contains everything including zero cross detection). And you can use all the scripts and libraries that come with it and allow for easy implementation.

I hope that this maybe helps you.
Edited by Yoku-San on 02/01/2021 9:50 AM
Thanks but I was a sound engineer in a former life and had gotten shocked a few times plus there's something about the sound of circuit breakers tripping that just gets on my nerves. My next build will be a pretty high powered (for a home build) one at at total of over 6000 watts and the Crydom 50A SSR that I'm looking at for the heating element comes to around USD20. Not worth me risking anything when I can afford USD20 and it comes in a nice casing with four nice terminals. Grin
For your information:

RobotDyn has released a new AC Dimmer Module for use with higher loads including a bigger heatsink.

Great find !
Please notice how the great current traces were thickened with solder, to cope with the big current.

Alternative source:
... if the shipping from RobotDyn is shocking expensive, as is case for my country... $39 with DHL
Another finding on Aliexpress... while browsing to see what's new.
This seller, which is actually the RobotDyn Official Store:

... has an "embedded" version of the dimmer, is just another board layout, for those who prefer soldering heater circuits, instead screw terminal block. Is half price versus the normal version !
Also, he is selling a DIN rail adapter, for the older dimmer board, if anyone use DIN rail for his setup.
I finally got mine. Weird how I had to get it via Indonesia. Came up to around USD7 - 8 shipped.
Is that a snubber circuit I see on board?
If you mean the circled RC from attached image, yes, as value and placement, quacks like a snubber.

renatoa attached the following image:
I've just been testing out the new 16A RobotDyn dimmer. Other than the heavier pcb traces, I don't think it offers much over the original version.

The heatsink is slightly bigger, but I think it still requires a bigger heatsink or some forced airflow to keep it's triac at a reasonable temperature when switching an 1800W 240V heating element.

I also recommend replacing the sil-pad with some thermal paste.

For an inexpensive controller setup for a small AC roaster I would recommend a Rotordyn AC dimmer controlling the AC fan and also providing the zero cross signal. For the heater I'd recommend using a zero crossing SSR such as the Crydom D2425.

A separate zero cross detector and instantaneous fire SSR is still my recommended setup for larger AC fans.


greencardigan wrote:

Other than the heavier pcb traces, I don't think it offers much over the original version.

The snubber ? Bigger terminals block, better suited for increased current.


greencardigan wrote:

I also recommend replacing the sil-pad with some thermal paste.

... but first check what you have on your actual copy... mine all 3-4 units are with thermal paste from the factory, no silicone pads.

My new models are still on the way from Chine, somewhere in the Netherlands Post yesterday.

As already wrote I am using the original board for some two years on a 1300W 230V TO without issues, in open air, no forced venting. About 60C degrees at heatsink surface.
For me is no way back to the traditional SSR usage, at least for this power level.
Even for more power I don't see the point for a separate ZCD, when this board is exactly the same, at third price.
You can simply use the triac on board to drive a bigger SSR, and you are done.
I have 4 original units and one 16A unit and they all have had sil-pads.

True, using these as the ZCD even when using a bigger SSR is most economical, although perhaps it is a bit more confusing for inexperienced users.
New version, with embedded 3.3 or 5V power source:
For some reason I am not able to get the TC4 to communicate properly with the robotdyn and I have a feeling it's a software issue but am not sure.

Do I need to modify the standard TC4+ code to accompany the robotdyn or should it work as is?
Please describe "communicate properly"
I can't image other issue than the PWM signal source: should be from Arduino board GPIO pin, not for TC4 OT1 output, which is for driving a SSR, using a reversed logic.
ZC signal from robotdyn board is a direct connection to Arduino interrupt pin.
Right now I'm just testing the heater side since it seems simpler (no ZC). The PWM signal is connected and should work.
When I use CONFIG_PAC3 for phase angle control on heater, and test the robotdyn (Vcc to OT1, PSM to GPIO PIN 9), there are no flashing lights and the robotdyn seems completely inactive. When I use CONFIG_PWM for PWM on heater, same connections, there are flashing lights and the robotdyn works. I'd like to use phase angel control but so far no luck.
PAC requires ZCD, that's why is not working
Without ZCD only PWM is available.
I didn't know that, problem solved ThumbsUp thanks
im using the RobotDyn module to control an 1200w AC vac motor using PAC2 mode. ive been testing with both the motor and a lamp as well. problem is that the motor or light is either OFF or at 50% and higher. below 50% it seems motor and light are bit jittery like its being pulsed on and off. any suggestions is very much appreciated!
dpecsok attached the following image:
i read in a few other posts that this is common using PAC. i there a way to control the RobotDyn using PWM mode? if so what is the proper way to wire it? sorry im a noob ha!
If motor is induction type, i.e. no brushes/sparks, then you need a special driver, called VFD, quite expensive.
PAC works for the so called "universal" motors, those that are noisy even without load, to distinguish them from induction motors, which are quiet.
Vac motors are universal type though, sounds strange what you report... connections from the diagram above are ok.

The bulb also should work ok, though... you should experience no flickering with PAC control. Please, can you post a short video clip to see the bulb behavior ?

PWM can be slow type, used to control heaters, in CONFIG_PWM mode, or fast type, output on IO3, to control DC fans or heaters using external drivers, choice depending on task.
thanks for your feedback, i will try to make a video soon..


renatoa wrote:
PWM can be slow type, used to control heaters, in CONFIG_PWM mode, or fast type, output on IO3, to control DC fans or heaters using external drivers, choice depending on task.

So in PWM mode its not possible to control an AC motor?
The answer is no, for a mains powered AC motor.
As we can read the descriptions in the user.h section listing the various configs:

//#define CONFIG_PWM // slow PWM on OT1 (heater); fast PWM output (3.922kHz) on IO3 (DC fan); ZCD not required

... PWM on IO3 means using a MOSFET driver, for a DC motor.

For your task people usually use CONFIG_PAC2:

#define CONFIG_PAC2 // phase angle control using ICC on OT1 (heater) and OT2 (fan); IO2 used to read the ZCD

Note of the above: even if not specified, ICC is used on OT1, for heater only, not on OT2, where phase angle control is used for fan.

Even the other config modes listed after PAC2 can be used, depending on motor type and available electronics to drive it.

//#define CONFIG_PAC2_IO3HTR // phase angle control on OT1 (heater) and OT2 (fan); IO2 reads the req'd ZCD; IO3 reserved for fast PWM output for heater
//#define CONFIG_PAC3 // phase angle control on OT1 (heater) and OT2 (fan); IO3 reads the req'd ZCD; IO3 not available for output
//#define CONFIG_PAC2_IO3FAN // phase angle control on OT1 (heater) and PWM control of IO3 (fan); IO2 used to read the ZCD
There is a possible reason that comes later in my mind...
A motor is an inductive load, compared to a heater, which is mainly resistive load, even if it looks as a coil Grin
A control element of an inductive load should be fitted with a RC circuit on the exit, called snubber.
The first version of this dimmer, from the very first post of this thread, lacks this circuit, being appropriate for resistive loads, or very low power motors.
There is a second version of this dimmer, signaled here first time in post #29 above, which is fitted with this snubber circuit, the components enclosed in ellipse in attached picture.
If you have the first version dimmer you have to attach these two components externally, on same output terminals as the motor, as you can see here:
The values of components, how well I am able to read on the image, seems to be 10nF/400V for capacitor, and 1kO for the resistor.
renatoa attached the following image:

Edited by renatoa on 03/14/2022 8:22 AM
renatoa thanks for your replies and input. heres a video, and you can see that there is a lot of flickering with the light and not so much dimming.
im thinking maybe the dimmer module is not working properly or im doing something wrong ha!
im looking into getting the updated version with the snubber circuits but im thinking that even without it shouldnt the light be dimming properly?

link to video:

Edited by renatoa on 03/16/2022 5:28 AM
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