Maybe a square wave signal. But I think I get what you mean. If the limiter signal is high, increase power and if it's low, decrease power.I should not have used the word PWM on my circuit, as that implies something different, but I drew up that circuit before figuring out how the signal works. I should perhaps have called it Ramp Up/Ramp Down, where one state causes the inverter to ramp up its power output, and the other state ramps down. This is why you must monitor the actual power output continuously in order to determine what state to set the signal at any given moment.
Thanks for your explanation. So the two pins actually connected to the inputs of optocoupler and the "polarity" of the 2 pins inside doesn't matter? isn't that will reverse bias the led?The external limiter connections just go to an opto-coupler inside the inverter, so there is no common ground, by design. And that is a good thing since the control circuit is then totally isolated from anything inside the inverter. So your signal only needs to be capable of driving an LED (which is inside the inverters opto-coupler). The 470R resistor is just for current limiting as you would need driving any LED.
Thank you!If you use the term "aviation connector" in your search, that is the magic word that should find plenty of them.
I just println the output from circuitsetup to serial monitor. Will try the serial plotter method.Glad you got it working. Well Done!
It may be worth testing the inverter with a purely resistive load (incandescent lamps / fanless heater etc)
If you have access to an oscilloscope, you should see your GPIO pin generating a stable and mostly unchanging mark-space waveform.
Maybe send the 100ms sampled values from the circuitsetup out on the serial port and use the arduino's "Serial Plotter" view to see if they look stable.
Do you have one of those plug in energy monitor things?
similar to this:
View attachment 26158
That may help narrow down the source of your power discrepancy.
Your signal is inverted compared to mine as I am sinking the LED current through my GPIO pin whereas you are sourcing from your GPIO pin.
I was pretty pleased with the accuracy and stability of my setup. If you look at the pic in the top post, you can see the inverter, plugin monitor and my text display all agree within a couple of watts of 207W.Does your inverter has huge difference between actual and the value shown on the display? I know each unit will be different but I should be expecting similar outcomes.
May I know what does the 2ms/W means? every 2ms of "HIGH" signal will increase the inverter's output power by 1W?Example:
House pulls 200W from grid. GTIL-Power-Toggling for 200W x 2ms/W into increase direction. After that i wait for 750ms onto new values that i receive from my house measure point.
My unit (2kW) starts unstable when the setpoint is below 80W. It keeps fluctuate between 72W and 0W (as shown on the inverter display)Also, I noticed that it isn't stable when outputting 40w or less. I also checked that with the commercial external limiter unit and it is the same, so that is a limitation of the inverter itself and not the control method.
If you want to make more boards of your solution i might would buy one if possible
May I know your inverter's output power delta around the setpoint?
From your first post, you mentioned you are checking the power every ~100ms.
I don't own an external limiter so I cant verify how accurate it can be. But i think the external limiter is just using an analog comparator to generate the pulse signal. With analog, there is no "interval" so I believe it would be pretty quick.
My unit (2kW) starts unstable when the setpoint is below 80W. It keeps fluctuate between 72W and 0W (as shown on the inverter display)
Probably just difference per unit. That said. Although my device did switching OFF and 75W for set power of <75W, it is actually quite close if you average it. For example, you average the powers for one minute.It's hard to remember exactly, but mine was unstable to the point of being unusable below 40W. Above that and it stated to settle down.