Control output of a variable SSR

Hi All.

To control the output power of a heating element. I'm using a variable solid state relay. This SSR can be controlled with a potentiometer of 500Kohm to control the output power.

Now i want to replace the manual potentiometer with something I can program with arduino. I was thinking about a digital potentiometer (digipot). I already tried this with the AD5206 100Kohm digipot. It has 6 channels each with a resistance of 100Kohm. I tried to put 5 channels in serie. But didn't manage to get this to work.

Is this the way to go? Or are there other more simple sollutions?

Please post a link to the product page or data sheet of the SSR.

Or are there other more simple sollutions?

PWM a logic level MOSFET?

Edit: If the heater is AC, that won't work. Maybe the OP could provide more detail like is requested in the forum guidelines in the how to use this forum-please read sticky.

jremington: Please post a link to the product page or data sheet of the SSR.

I tried 2 ssr's: this one KR2025AX http://www.kyotto.com/PDF/PDF/KR2010AX.pdf

and this one SSR-25VA http://www.fotek.com.tw/pdf/2013515_90632265.PDF

groundFungus: PWM a logic level MOSFET?

Edit: If the heater is AC, that won't work. Maybe the OP could provide more detail like is requested in the forum guidelines in the how to use this forum-please read sticky.

The heater is 230vac 50hz somewhere around 3000w.

with something I can program with arduino.

I would use a different type of SSR (the more common type that is digitally switched on and off by a voltage input), and use low frequency PWM, or just on/off, to control the heater.

jremington:
I would use a different type of SSR (the more common type that is digitally switched on and off by a voltage input), and use low frequency PWM, or just on/off, to control the heater.

It is my goal to contoll the heating element with a constant output power. Im making use of a volt amper meter to determine the current ouput power. The software tries to stay as much in the range to the given setpoint by altering the digipot.

Although this was the plan. But I cant get it to work.

Any help/advise if it’s even possible the way I described would great.

It is not possible with an SSR to have a "constant output power" except for fully on. By definition, the power is switched on and off.

If the switching is done frequently, the PWM approach described in reply #4 is by far the simplest and most popular way of [u]approximating[/u] your goal.

This won't work with a digital pot, as you discovered.

I tried to put 5 channels in serie.

jremington: the PWM approach described in reply #4 is by far the simplest and most popular way of [u]approximating[/u] your goal.

This won't work with a digital pot, as you discovered.

Thank you for the reply.

Although, I think this solution doesnt fit my needs. I want to control an heating element on output power because nomather what type it is( 3000w, 4000w,7000w). I want to set an output power to given setpoint. Thats why I'm using a volt ampere meter. Determine the current power and alter if it's diffrent from the setpoint.

Any other options?

You could buy a variable voltage AC or DC supply, and set the voltage to the appropriate value.

blaat: Hi All.

To control the output power of a heating element. I'm using a variable solid state relay. This SSR can be controlled with a potentiometer of 500Kohm to control the output power.

Now i want to replace the manual potentiometer with something I can program with arduino. I was thinking about a digital potentiometer (digipot). I already tried this with the AD5206 100Kohm digipot. It has 6 channels each with a resistance of 100Kohm. I tried to put 5 channels in serie. But didn't manage to get this to work.

Is this the way to go? Or are there other more simple sollutions?

You can approximate the original series resistor by using several wire wound resistors in series with the heating element and then progressively shorting the resistors out of the circuit using individual SSR. The SSRs can be controlled by Arduino pins.

Paul

Paul_KD7HB: You can approximate the original series resistor by using several wire wound resistors in series with the heating element and then progressively shorting the resistors out of the circuit using individual SSR. The SSRs can be controlled by Arduino pins.

Paul

Hi Paul. Thx for the reply. How do you want to adjust those resistors by programming?

Put a SSR across each resistor. Turn the SSR on and off using one digital pin from your Arduino. When the pin is low, the SSR is off and the resistor is in series with the heater. When the pin is high, the SSR is on and the current to the heating element now goes directly to it.

Paul

Paul_KD7HB: Put a SSR across each resistor. Turn the SSR on and off using one digital pin from your Arduino. When the pin is low, the SSR is off and the resistor is in series with the heater. When the pin is high, the SSR is on and the current to the heating element now goes directly to it.

Paul

So if I understand correctly. If I want to control the heating element in 100 steps. 0% to 100%. I need 100 resistors and 100 ssr's?

blaat:
So if I understand correctly. If I want to control the heating element in 100 steps. 0% to 100%.
I need 100 resistors and 100 ssr’s?

Roger, roger!