Constant drive on a heating element?

[maisch]

What electronics are used to constantly drive a heating element eliminating the rapid on/off switching of a PID?

I was thinking a frequency drive might do this but then how would the FD be controlled from say an Arduino?

Is this even possible without burning out the element faster?

Any electronics whizzes out there who can help?

 

[passedpawn]

You can put the PID into manual mode. Then you control on/off instead of the temperature feedback / switching mode.

Or, you can skip the PID altogether and just use a switch.

 

[maisch]

You can put the PID into manual mode. Then you control on/off instead of the temperature feedback / switching mode.

Or, you can skip the PID altogether and just use a switch.

True, but what electronics component is going to have the ability to vary the voltage on a 240V 5500W element from 0V to 240V with either an analog or digital input without the on/off cycles?

 

[schematix]

AC power is always varying based on where it’s at in the cycle. There isn’t a way to vary power that doesn’t involve some type of switching on and off.

Not really sure what you are getting at here / trying to improve.

There is a type of controller that delivers an integer number of half cycles. Those are essentially noiseless and can provide pretty fine power delivery control.

 

[maisch]

AC power is always varying based on where it’s at in the cycle. There isn’t a way to vary power that doesn’t involve some type of switching on and off.

Not really sure what you are getting at here / trying to improve.

There is a type of controller that delivers an integer number of half cycles. Those are essentially noiseless and can provide pretty fine power delivery control.

Like a 1 channel 240V dimmer switch for Arduino? Does that make sense?

Something like this:
https://www.amazon.com/dp/B01BMSRVVE/?tag=skimlinks_replacement-20

So now instead of on/off switching you're directly controlling the voltage of the heating element.

 

[maisch]

So you've got this one which is good for 500w but we'd need a heavy duty 240V, 5500w+ version.

https://www.amazon.com/dp/B06Y1DT1WP/?tag=skimlinks_replacement-20

If I were only an EE. Something like this @0V output would then have to dissipate 5500w (the power coming in) which may not be very efficient and would generate a lot of heat but might still be worth trying.

Hrmm... also found SSVR's like this which might be worth trying:

https://www.auberins.com/index.php?main_page=product_info&products_id=332

That would require some type of rheostat controlled by digital or analog pins... anyone know if those exist?

 

[schematix]

Like a 1 channel 240V dimmer switch for Arduino? Does that make sense?

Something like this:
https://www.amazon.com/dp/B01BMSRVVE/?tag=skimlinks_replacement-20

So now instead of on/off switching you're directly controlling the voltage of the heating element.

Makes sense but it doesn’t.

Light dimmers are extremely noisy due to their sudden on and off currents, and as such are not suitable for high current applications. The voltage also isn’t constant. It just turns on at a different part of the cycle.

I’m not really sure what you’re really after here.

 

[maisch]

Ok, a little more research, so in order to drive the SSVR from an Arduino a digital pot is needed in the 0 Kohm - 400 Kohm range.

Not sure that exists, ready made, but there seems to be a lot of digital IC pots.

 

[passedpawn]

True, but what electronics component is going to have the ability to vary the voltage on a 240V 5500W element from 0V to 240V with either an analog or digital input without the on/off cycles?

Variac. It's what's referred to as a auto-transformer. But for the power you probably need, cost will be prohibitive. Still, look up variac on ebay and punch in your wattage (e.g., 30A * 240V = 7200W

 

[Brumateur]

Ok, a little more research, so in order to drive the SSVR from an Arduino a digital pot is needed in the 0 Kohm - 400 Kohm range.

Not sure that exists, ready made, but there seems to be a lot of digital IC pots.

Take a look here - https://playground.arduino.cc/Main/ACPhaseControl

You can use the same schematic but need mo re powerful triac. Fro example this one - https://www.arrow.com/en/products/bta40-600b/stmicroelectronics

 

[BrunDog]

Proportional SSR

 

[Soulshine2]

What electronics are used to constantly drive a heating element eliminating the rapid on/off switching of a PID?

I was thinking a frequency drive might do this but then how would the FD be controlled from say an Arduino?

Is this even possible without burning out the element faster?

Any electronics whizzes out there who can help?

im no electronic whiz but this is why I chose to use electric stove parts to make my rig. The elements are designed to heat at varied ranges, the knob is basically a potentiometer. The red light tells me either one are on. I can go full on (boil) or turn it down to keep warm/simmer.
My suggestion - go to your local home improvement center , appliances dept and find a replacement elec stove element controller . might be able to re-do the connection to fit your application.

 

[golfindia]

Here are the electronics involved. Making one that works at 240v/30a will require "some scaling".

https://www.google.com/url?q=http:/...FjALegQIARAB&usg=AOvVaw227vWOH-HjsnQspHeTDTu_

 

[passedpawn]

Here are the electronics involved. Making one that works at 240v/30a will require "some scaling".

https://www.google.com/url?q=http:/...FjALegQIARAB&usg=AOvVaw227vWOH-HjsnQspHeTDTu_

That's almost exactly what I posted in #9 above. Variacs for the necessary power would be very expensive (and huge) - shipping would be a lot. But I've seen ones that were pretty close on ebay.

 

[passedpawn]

Making one that works at 240v/30a will require "some scaling".

Here you go:

http://rover.ebay.com/rover/1/711-5...0001&campid=5338413729&icep_item=153047287259

 

[golfindia]

Exactly. In the olden days of DIY ham radio amps they used those big ones to bring up RF tube xformer voltage slowly to burn in tubes (gettering).

 

[Bobby_M]

I think you're thinking way too hard. When you say "without switching on and off", I think you may be concerned about a non-issue. Controlling an element through a regular SSR with either a PWM circuit or a PID type controller in PWM mode doesn't look like on/off control as long as the cycle time is 2 seconds or less. I like 1 second on a 5 gallon batch.

In case it's not hitting home, 5500 watts on a 1/2 second on and 1/2 second off cycle feels like a 2750w element on full power.

 

[maisch]

I think I've got this figured out.

Like @BrunDog said I need a proportional SSR.

So basically I need:

1.) Proportional SSR
2.) Digital Potentiometer compatible with #1 (AD5241 or AD5242)
3.) Interface board made with #2

An AD5241 gives 256 (8 bit) steps of resistance to control the Proportional SSR.

Connect the interface board #3 to an Arduino or maybe a USB control board and you're golden. Control the SSR from a PC through a USB to Serial converter (custom PID control software).

So that'll give me 256 steps from 0 - 100%, 2.56% power per step.

Maybe someone more versed in electronics could tell me if this would work?

 

[Brumateur]

This proportional SSR has a micro controller inside which implement a logic described here - https://playground.arduino.cc/Main/ACPhaseControl

Yes you can use a digital potemtiommeter connected to proportional SSR controlled by Arduino but why do you need a 2 micro controllers (one in SSR and another in Arduino) if you can get same results using an arduino only?

 

[augiedoggy]

Why exactly is this option being considered again? Is this just for tinkering sake or is there some sort of benefit being sought out?

 

[maisch]

This proportional SSR has a micro controller inside which implement a logic described here - https://playground.arduino.cc/Main/ACPhaseControl

Yes you can use a digital potemtiommeter connected to proportional SSR controlled by Arduino but why do you need a 2 micro controllers (one in SSR and another in Arduino) if you can get same results using an arduino only?

The spec sheet for the proportional SSR being considered says it takes as input 1M (1/2W) variable resistor thus you have the AD5241 board to provide said input.

If an Arduino is not available and only a USB port on a PC then I think the setup above would work just need to find a temp sensor board to go along with it.

Not being electrically inclined I don't how you would hook the proportional ssr directly to the pins on the Arduino or how the Arduino would provide 1M variable resistor input to the proportional SSR without an additional circuit? You would have to explain this to me? Or perhaps you mean the linked circuit would replace the entire proportional SSR?

 

[BrunDog]

I think I've got this figured out.

Like @BrunDog said I need a proportional SSR.

So basically I need:

1.) Proportional SSR
2.) Digital Potentiometer compatible with #1 (AD5241 or AD5242)
3.) Interface board made with #2

An AD5241 gives 256 (8 bit) steps of resistance to control the Proportional SSR.

Connect the interface board #3 to an Arduino or maybe a USB control board and you're golden. Control the SSR from a PC through a USB to Serial converter (custom PID control software).

So that'll give me 256 steps from 0 - 100%, 2.56% power per step.

Maybe someone more versed in electronics could tell me if this would work?

Need not be this complicated. You can use a proportional SSR with a 0-5VDC input (analog), then take a PWM output from the Arduino and convert it to analog output with an R-C (resistor & capacitor) aka lowpass circuit.

Now, I am a fan of proportional control like this, but you should think about what you are really looking to gain for the cost. Heating elements have enough thermal mass that turning them on and off any faster than 1 or 2 seconds like Bobby mentioned above doesn't buy you much. If you ran it with a duty cycle of 1 second, to the liquid being heated, it would see practically no heat/cool cycles. Proportional SSRs are >$100 and regular ones are about a fifth of that.

Also, your math is not correct. 256 steps of resolution gives you 0.39% per step.

 

[augiedoggy]

@BrunDog so what is the advantage to this?

 

[maisch]

Need not be this complicated. You can use a proportional SSR with a 0-5VDC input (analog), then take a PWM output from the Arduino and convert it to analog output with an R-C (resistor & capacitor) aka lowpass circuit.

Now, I am a fan of proportional control like this, but you should think about what you are really looking to gain for the cost. Heating elements have enough thermal mass that turning them on and off any faster than 1 or 2 seconds like Bobby mentioned above doesn't buy you much. If you ran it with a duty cycle of 1 second, to the liquid being heated, it would see practically no heat/cool cycles. Proportional SSRs are >$100 and regular ones are about a fifth of that.

Also, your math is not correct. 256 steps of resolution gives you 0.39% per step.

Can you point me to a 240V 40Amp proportional SSR with 0 - 5VDC input?

Nevermind, found some:

http://www.crydom.com/en/products/catalog/pcv-series-control-relays.pdf

So yea, starting to add up now.

 

[maisch]

Can a proportional SSR be connected to a PID controller? Just thinking out-loud in case anyone know for sure.

 

[BrunDog]

Analog PID, yes.

 

[brumateur1]

Or perhaps you mean the linked circuit would replace the entire proportional SSR?

Yes. Arduino + triac with adequate amps replace an proportional SSR. Just read the article.

 

[bracconiere]

https://www.amazon.com/dp/B01CCK56QS/?tag=skimlinks_replacement-20

i use a fan speed controller for my 1500 watt hot plate...works good...

don't know how you'd control it...Maybe something to rotate the knob?

feel free to ignore this,

 

[golfindia]

A 10000 watt SCR for $26 sounds a little fishy.

 

[bracconiere]

i got my 1500 watt 120v fan speed controller for like $12 or something...or$16

https://www.amazon.com/dp/B00U3LD1WA/?tag=skimlinks_replacement-20

this is what i use with my hotplate, along with a kill-a-watt meter....have my hotplate direct power, and the fan speed controller will vary the wattage from 400 to 1400. according to the kill a watt meter, without getting hot....

from what i've read, voltage regulation is a lot less expensive then resistance dimmers....and doesn't produce as much heat...Before i tried this thing, i always didn't want to spend the 150 on a expensive light dimmer...