Constant drive on a heating element?

[augiedoggy]

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,

The solder trace on these board cant even reliably hold up to a 5500w load.. there are a couple threads on this from about 3-4 years ago on here somewhere where owners had to modify them to keep them working.

 

[bracconiere]

The solder trace on these board cant even reliably hold up to a 5500w load.. there are a couple threads on this from about 3-4 years ago on here somewhere where owners had to modify them to keep them working.

so with help they work?

How would you control one with a Arduino though?

(i'll have to poke around google to try and find those threads for the OP)

 

[golfindia]

And where would you attach a ground to the SCR box?

 

[augiedoggy]

I may be wrong but I thought they dont work well with 60hz power for some reason as well.. its been a long time , I'm still trying to figure out the point here? I currently use pid as well as duty cycle to control my element power efficiently and effectively with my arduino.. again whats the benefit your after?

 

[bracconiere]

I may be wrong but I thought they dont work well with 60hz power for some reason as well.. its been a long time , I'm still trying to figure out the point here? I currently use pid as well as duty cycle to control my element power efficiently and effectively with my arduino.. again whats the benefit your after?

i took the OP to mean they were after temp control, not on off cycles? like my hot plate....when i'm using my hotplate for stuff, i need constant lower temp, not an on off cycle...

 

[augiedoggy]

i took the OP to mean they were after temp control, not on off cycles? like my hot plate....when i'm using my hotplate for stuff, i need constant lower temp, not an on off cycle...

Ok lets clear this one up.
Controlled high speed on/off pulsing very effectively does control the surface heating temp of the elements.. Thats they whole point of it being used to control the intensity of a boil. when you pulse the power this way it never lets the element come up to full temp.. just like controlling motor speed or an led light circuit this way.

when I use duty cycle mode on my 3bbl system to boil at 60% strength for example, all 4 5500w elements combined show a total amp draw of 52 amps and not the 90 amps they normally draw. the boil is much less powerful and I can control it consistently and fairly linearly this way.
So again what is the advantage of all the extra hardware? Is there one?

 

[bracconiere]

Ok lets clear this one up.
Controlled high speed on/off pulsing very effectively does control the surface heating temp of the elements.. Thats they whole point of it being used to control the intensity of a boil. when you pulse the power this way it never lets the element come up to full temp.. just like controlling motor speed or an led light circuit this way.

when I use duty cycle mode on my 3bbl system to boil at 60% strength for example, all 4 5500w elements combined show a total amp draw of 52 amps and not the 90 amps they normally draw. the boil is much less powerful and I can control it consistently and fairly linearly this way.
So again what is the advantage of all the extra hardware? Is there one?

i wouldn't know, i brew on NG...but i do know when i make other alcoholic beverages. My hot plate would turn on and off like 20 seconds apart, and i had to jump it into always on, and use my fan speed controller to get a consistent low temp....i'd imagine if you can control ms on off cycles it'd work as good...

i just thought i'd try and say what works for my hotplate, thus my statement of feel free to put me to ignore.... (i've been accused of starting too many fights here)

 

[augiedoggy]

No worries, im just trying to share and understand myself.
Quickly pulsing the element times does work effectively the same way to control output and IMO is a cleaner solution with the available equipment already at hand. I'm by no means an expert on this either. but that why I keep asking what the advantage would be because obviously theres something myself or someones missing here unless this is just for the fun of making it happen.

 

[bracconiere]

No worries, im just trying to share and understand myself.
Quickly pulsing the element times does work effectively the same way to control output and IMO is a cleaner solution with the available equipment already at hand. I'm by no means an expert on this either. but that why I keep asking what the advantage would be because obviously theres something myself or someones missing here unless this is just for the fun of making it happen.

i was thinking, your right and if you can get the cycle fast enough. it'd be the same as me seeing 30fps tv as motion to the beer....it's just my hotplate was like the old dial-up streaming....

 

[brumateur1]

Quickly pulsing the element times does work effectively .

Could you define "quickly"?

When you have duty cycle 1sec or less you should start synchronizing your control pulses with mains period. Otherwise you can get a huge output error

 

[augiedoggy]

Could you define "quickly"?

When you have duty cycle 1sec or less you should start synchronizing your control pulses with mains period. Otherwise you can get a huge output error

for example on my mypin td4 pid, when in manual mode and set to 50% power.. the element is on for half a second then off for half a second ... pulsing, this never allows the element to get hotter than half power would allow.

 

[augiedoggy]

I can also set the manual mode to 5% and it barely gets warm by comparison. no errors just a flicker of an led once every second.

 

[ajdelange]

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

A saturable core reactor would be ideal for this. Even smoother control than a Variac.

 

[maisch]

A saturable core reactor would be ideal for this. Even smoother control than a Variac.

Very cool. Must be a custom made component? Wasn't able to find these off the shelf. Not sure I wanna know how much one would cost.

 

[ajdelange]

I wasn't being entirely serious here. I haven't seen one of these since right around the dawn of SCRs at which time they were being phased (no pun intended) out. A quick net search, however, shows that they are still made. I wonder what for.

The mention of the Variac invoked nostalgia (there used to be a handful in every lab) and that reminded me of the reactors.

 

[maisch]

Could you define "quickly"?

When you have duty cycle 1sec or less you should start synchronizing your control pulses with mains period. Otherwise you can get a huge output error

So how does a controller w/ 12VDC turning on/off an SSR - synchronize with the AC? or is it the SSR circuit that does the syncing such that the controller doesn't care when it triggers an on/off cycle?

 

[augiedoggy]

So how does a controller w/ 12VDC turning on/off an SSR - synchronize with the AC? or is it the SSR circuit that does the syncing such that the controller doesn't care when it triggers an on/off cycle?

the ssr just pulses the power on and off at a certain fast rate determined by the cycle time setpoint of the pid.. I dont believe ac cycle time has much to do with it really its not pulsing it that fast. perhaps someone more knowledgeable will clarify. if the pid cycle setpoint is set for 2 second than in 50% manual mode the pid would power the element for 1 second then off for one second at least thats how it appeared to work on my mypin pids.

 

[ajdelange]

An SSR contains a triac (or a pair of SCR's). These do not conduct unless provided with a gate signal. The 12 V is in the gating circuit. Once the gate is applied the device will conduct, even though the gate be removed, for the remainder of the half cycle. There are lots of ways to gate these devices either synchronous to the supply or asynchronous. One way of effecting proportional control is to gate on for a certain number of half cycles and then off for another integer number of half cycles. This means the device can be switched on and off when the voltage (and current with a load like a heater) are 0 minimizing noise. Alternatively they can be switched on with a short pulse at some point in each half cycle in which case they will turn off when current drops to 0 at the end of the cycle. Or gating can be applied for some number of seconds and turned off for the rest of a cycle. This is what is done with the PID controller setups that home brewers use. The length of the cycle is usually set to something less than the thermal time constant of the load so that control of the PV is smooth. Typical values are a few seconds up to perhaps half a minute. There is really no problem with going below 1 second cycle time asynchronously. You may turn on in the middle of a line half cycle some time and at the beginning other times so you won't get precisely the same energy delivered from cycle (controller) to cycle but as there 120 half cycles (line) in a second the variability is small and the error will average out. OTOH there is no reason to go with such a short cycle time if the thermal time constant of the load is 30 seconds.

 

[brumateur1]

So how does a controller w/ 12VDC turning on/off an SSR - synchronize with the AC? or is it the SSR circuit that does the syncing such that the controller doesn't care when it triggers an on/off cycle?

Please this article - https://playground.arduino.cc/Main/ACPhaseControl

 

[maisch]

An SSR contains a triac (or a pair of SCR's). These do not conduct unless provided with a gate signal. The 12 V is in the gating circuit. Once the gate is applied the device will conduct, even though the gate be removed, for the remainder of the half cycle. There are lots of ways to gate these devices either synchronous to the supply or asynchronous. One way of effecting proportional control is to gate on for a certain number of half cycles and then off for another integer number of half cycles. This means the device can be switched on and off when the voltage (and current with a load like a heater) are 0 minimizing noise. Alternatively they can be switched on with a short pulse at some point in each half cycle in which case they will turn off when current drops to 0 at the end of the cycle. Or gating can be applied for some number of seconds and turned off for the rest of a cycle. This is what is done with the PID controller setups that home brewers use. The length of the cycle is usually set to something less than the thermal time constant of the load so that control of the PV is smooth. Typical values are a few seconds up to perhaps half a minute. There is really no problem with going below 1 second cycle time asynchronously. You may turn on in the middle of a line half cycle some time and at the beginning other times so you won't get precisely the same energy delivered from cycle (controller) to cycle but as there 120 half cycles (line) in a second the variability is small and the error will average out. OTOH there is no reason to go with such a short cycle time if the thermal time constant of the load is 30 seconds.

Thank you for taking the time to explain. This explains how an Arduino cycles (turns on/off) an SSR without being connected or synced to the AC and how a PID can sync itself to the AC by being powered by it. If I understand correctly.

 

[maisch]

Please this article - https://playground.arduino.cc/Main/ACPhaseControl

Yes, this is the one you referred me to earlier and demonstrates, using a custom triac circuit and an interrupt triggered at zero crossing, a synced approach using the Arduino. Again, if my understanding is correct.

So this would be slightly more efficient than just cycling an SSR on/off using an analog signal from the Arduino.

 

[BrunDog]

I’m with @augiedoggy. What’s the goal? For me, using standard SSR’s with short cycle times (~1 sec) work fine for reasonable cost and installation trouble. You can use a zero-cross SSR if you want to ensure the switch occurs at the base of the AC sine wave. Or use a proportional SSR. These are accessible, low cost, and proven reliable solutions. We are heating liquid, not modulating high speed control systems.

If defined control to the specific AC cycle is your goal, then this is really an academic exercise, upon which the above or other are possible solutions.

 

[maisch]

I’m with @augiedoggy. What’s the goal? For me, using standard SSR’s with short cycle times (~1 sec) work fine for reasonable cost and installation trouble. You can use a zero-cross SSR if you want to ensure the switch occurs at the base of the AC sine wave. Or use a proportional SSR. These are accessible, low cost, and proven reliable solutions. We are heating liquid, not modulating high speed control systems.

If defined control to the specific AC cycle is your goal, then this is really an academic exercise, upon which the above or other are possible solutions.

The goal is as the title says, "Constant drive on a heating element". That is - to drive a heating element without on/off switching.

As I've repeated many times I'm not an EE nor am I well versed in electronics so I had to pose the question and search for a solution.

"What is your goal" type questions are normally posed by more serious business type folks.

The result of asking questions is simply gaining understanding. Ancillary knowledge gained like switching mid sine wave vs. at zero crossing just adds value.

I'm considering the I2C variable pot solution just for kicks. Now wouldn't that be cool. A heating element controlled from the USB port of your PC using custom software. A software PID of sorts, controlled by mouse clicks on your screen and custom PID, Fuzzy logic, AI algorithm.

 

[augiedoggy]

The goal is as the title says, "Constant drive on a heating element". That is - to drive a heating element without on/off switching.

As I've repeated many times I'm not an EE nor am I well versed in electronics so I had to pose the question and search for a solution.

"What is your goal" type questions are normally posed by more serious business type folks.

The result of asking questions is simply gaining understanding. Ancillary knowledge gained like switching mid sine wave vs. at zero crossing just adds value.

I'm considering the I2C variable pot solution just for kicks. Now wouldn't that be cool. A heating element controlled from the USB port of your PC using custom software. A software PID of sorts, controlled by mouse clicks on your screen and custom PID, Fuzzy logic, AI algorithm.

Ok but I asked mainly to understand if you were asking and considering this venture because you didnt understand it was really unecessary and how the normal method 95% of us use already controls the heat output and that its already easily done natively with adrduinos hardware and a simple ssr. Your questions above and in the omron thread also eluded to you not understanding how the on off switching already controlled heat output in a steady linear fashion like your describing.

It would have helped if you would have just shared this info upright as it would have prevented a lot of unnecessary posts. Nothing wrong with wanting to understand something better and accomplish something in a different more complex way. I wanted to know if there was a practical reason or application where this would be a better solution in case there was something I wasnot aware of.
And I and some others just wanted to make sure you understood before you drove down this path that theres already a paved road along side it. You say you posed the question for a solution and I wanted to make sure you understood there a better method all together that we use here for home brewing applications. In other words I wanted you to know lighters exist before you came here asking how to make matches to light your propane burner is all.

Please understand that this is a homebrewing forum and most of us will assume your looking for practical information related to accomplishing electric brewing Unless otherwise pointed out by the person asking. Not just for you but for all the other homebrewers looking for knowledge who might stumble on this looking for understanding and get confused as hell by something they really dont need to worry about to control their boil inless they want to. Its helps to get it out of the way so everyones on the same page before persueing academic theories and alternatives.

Sorry if im coming off condescending it really wasnt my intent I am just trying to communicate my point of view at this point since you have made it clear you felt it was not important for us to understand the true point of all this. After all you cant say you didnt learn more about how duty cycle and pwm control works because of us questioning you motive right?

 

[maisch]

Ok but I asked mainly to understand if you were asking and considering this unnecessary venture because you didnt understand how the normal method 95% of us use already controls the heat output and that its already easily done natively with adrduinos hardware and a simple ssr. Your questions above and in the omron thread also eluded to you not understanding how the on off switching already controlled heat output in a linear fashion like your describing.

It would have helped if you would have just shared this info upright as it would have prevented a lot of unnecessary posts. Nothing wrong with wanting to understand something better and accomplish something in a different more complex way. I wanted to know if there was a practical reason or application where this would be a better solution in case there was something I wasnot aware of.
And I and some others just wanted to make sure you understood before you drove down this path that theres already a paved road along side it. You say you posed the question for a solution and I wanted to make sure you understood there a better method all together that we use here for home brewing applications. In other words I wanted you to know lighters exist before you came here asking how to make matches to light your propane burner is all.

Please understand that this is a homebrewing forum and most of us will assume your looking for practical information related to accomplishing electric brewing Unless otherwise pointed out by the person asking. Not just for you but for all the other homebrewers looking for knowledge who might stumble on this looking for understanding and get confused as hell by something they really dont need to worry about to control their boil. its helps to get it out of the way so everyones on the same page before persueing academic theories and alternatives.

Sorry if im coming off condescending it really wasnt my intent I am just trying to communicate my point of view at this point since you have made it clear you felt it was not important for us to understand the true point of all this.

I'm don't quite follow you but I've learned a great deal from all of the responses and apologize if I've offended you.

 

[augiedoggy]

I'm don't quite follow you but I've learned a great deal from all of the responses and apologize if I've offended you.

No you havent, sorry I'm lousy at communicating online. I just felt that you weren't understanding the importance of your intentions and how they matter and factor in to how informative and clear the thread plays out for everyone involved is all.

 

[doug293cz]

The goal is as the title says, "Constant drive on a heating element". That is - to drive a heating element without on/off switching.

...

You cannot control an AC powered heater without on/off pulsing. The AC voltage and current go to zero 120 times a second (in the USA), which means at those points the element is off. Phase angle power control, is still on/off switching, but at a cycle time of 8.33 msec. So, everything discussed so far in this thread is still on/off pulsing. The only thing changing is the cycle time, which for the options discussed varies from 8.33 msec up to 2 sec.

The only way to get zero on/off pulsing is to use a controlled output voltage DC power supply. If you want to go this way, a switching power supply is much more efficient than a linear supply (I don't even know if you can find a linear supply at ~5500W.)

Looking for a solution implies that there is a problem that needs to be solved. Many of the replies to this thread are asking what is the actual problem that needs to be solved, and noting that there is no real unsolved problem related to powering heating elements in homebrewing applications. One of the basic tenants of engineering is that if you don't understand and state the problem correctly, you are very unlikely to find a good solution.

Brew on

 

[maisch]

You cannot control an AC powered heater without on/off pulsing. The AC voltage and current go to zero 120 times a second (in the USA), which means at those points the element is off. Phase angle power control, is still on/off switching, but at a cycle time of 8.33 msec. So, everything discussed so far in this thread is still on/off pulsing. The only thing changing is the cycle time, which for the options discussed varies from 8.33 msec up to 2 sec.

The only way to get zero on/off pulsing is to use a controlled output voltage DC power supply. If you want to go this way, a switching power supply is much more efficient than a linear supply (I don't even know if you can find a linear supply at ~5500W.)

Looking for a solution implies that there is a problem that needs to be solved. Many of the replies to this thread are asking what is the actual problem that needs to be solved, and noting that there is no real unsolved problem related to powering heating elements in homebrewing applications. One of the basic tenants of engineering is that if you don't understand and state the problem correctly, you are very unlikely to find a good solution.

I think this might be getting a little out of hand. I've already stated I'm not an EE and don't understand, therefore if answers were provided that helped me understand and come to a conclusion how can that be questioned?

I think this question has been answered and don't want to get into another discussion.

 

[golfindia]

One of the basic tenants of engineering is that if you don't understand and state the problem correctly, you are very unlikely to find a good solution.

Reminds me of a Dilbert comic strip!

 

[doug293cz]

I think this might be getting a little out of hand. I've already stated I'm not an EE and don't understand, therefore if answers were provided that helped me understand and come to a conclusion how can that be questioned?

I think this question has been answered and don't want to get into another discussion.

So what is your conclusion?

Brew on