5500W Element Control: To PID, or not to PID?

Hey guys,

It seems like I've read a copious amount on the topic of controlling an electric kettle and HLT with a PID/SSR combination, yet I still have some questions. My goal is to control the kettles in a very simple way--meaning I would prefer to not use a thermowell or RTD to control the SSR-element, and I would only be controlling one element at a time.

I've read posts that state using a PID/SSR for "manual" mode is a waste of engineering, which makes sense to me, in some ways. For my purposes, anyway, it would seem to be overkill.

Here's my goal: control one 240v element at a time so that I can manually adjust the temperature of the wort or water in the kettle. Am I locked in with the PID/SSR combo?

Thanks

If you really want temp control, then the PID is really the way to go. You could *probably* do it with a pulse width modulator, but it'll be a royal PITA.

Also, if you just want to boil, you can probably skip all control and just plug it in. I have a 5500W element in my BK and a pulse modulator to control it, but I brewed the last three batches with the PWM cranked up to 100% on the boil. I could have just plugged it in and let it roll.

If you want to control temperature (as you say), then AUTO mode (not manual mode) is what you want. Yes, you should get a PID and a temp sensor of some kind.

Use a PID with a K-type thermocouple on Auto mode for any temp control. It's easy and consistent every time once you have it dialed in.

But like Walker says - not really needed for a simple boil... Though I use a 2nd PID in manual mode in my system for the boil. I maintain a good rolling boil at 55-60% power with a 5500w element.

I would have to say the PWM is the way to go. As for ease of use there is no easier way. Just turn the dial.

Walker: What type of PWM are you using. With mine I can not put it past half way during boil or it will boil over. I am using a 5500w element. Most of the time it is set just between and 1/4 and 1/2 for maintaining a rigorous boil.

Brewmoor said:

Walker: What type of PWM are you using. With mine I can not put it past half way during boil or it will boil over. I am using a 5500w element. Most of the time it is set just between and 1/4 and 1/2 for maintaining a rigorous boil.

Click to expand...

Mine is a DIY PWM. One 555 timer IC, one potentiometer, and a couple of capacitors.

My kettle is not well insulated, so I think that's why I can run it at full blast and not boil over during the main part of the boil (a boil over is EASY at the start before the hot break).

At 100% on with the 5500W element, the boil is pretty violent..... makes the whole brew-stand wobble back and forth.

I hadn't thought of using a PWM. I guess if I was going to build one, though, I may as well build a PID/SSR controller and just drop the thermocouple over the the side of the kettle to measure temps, so I can keep it portable.

Any recommendations for a basic PID/SSR combo to control one 5500W element?

Not to hijack my own thread, but I was wondering about the virtues of putting a GFCI breaker in the control box vs at the breaker box. Anyone done this?

I used this page to build my PWM. It is a very simple circuit. It too requires an SSR. http://home.highertech.net/~cdp/boilnew/boilnew.htm

I am not sure I would attempt to build a PID. It would be better to just buy one. I have been happy with the one I got from Auber Instruments. http://www.auberins.com/index.php?main_page=index&cPath=1&zenid=9fbff14ed910c984a29f2231ebd9a7b7
Though I dont really use it as a PID. I end up just putting up to 200 and waiting for it to get to the temp I need. I have found I don't really need the "Hold" temp feature since I am mostly batch sparging.

If you can still find them. There is a GFI cord that I got on Ebay. It seemed to be the best option for me. Since I rent it was nice to buy a cheap breaker for the panel and have my GFI universal. It is built into the cord and has a standard 240v plug on the end.

Just curious, how would a temperature controller work to control the vigor of the boil. E.g., say your wort boils at 50% On in Manual, and boils vigorously at 70% On. For either percentage, the temperature is the same, only how hard it's boiling changes. How would a temperature controller help here?

RandomSF said:

Just curious, how would a temperature controller work to control the vigor of the boil. E.g., say your wort boils at 50% On in Manual, and boils vigorously at 70% On. For either percentage, the temperature is the same, only how hard it's boiling changes. How would a temperature controller help here?

Click to expand...

It's all about pulse width modulation.

What you are doing is telling the controller that you want the element to be on for <whatever>% of the time. The PID will turn the element on and off based on your programming.... and it does not use the input from the temp probe when doing so.

When the element is on, it is 100% on. When it is off, it is 100% off.

But, by programming it to do something like "turn on for 1 second, then turn off for a half second", you are effectively getting 66% power from your element.

A PID is kind of overkill for this because all of the smarts of the PID and the temp input are not used. You can use a simple pulse width modulator circuit to get this behavior for a fraction of the price of a PID.

BUT... If you need a PID part of the time (mash) and then a PWM the other part of the time (boil), and you don't need to do these things at the same time, a single Auber PID with "manual mode" support is perfect for the job. You just switch the mode of operation when you need the PWM behavior.

EDIT: even in manual mode, the PID needs a temp probe connected to it, but it doesn't actually USE the input from the probe. You can leave the probe dangling in the air if you want.

Right. That describes Manual mode well, and I understand that. My question is about how you would control in Automatic between just boiling and vigorous boiling, using a temperature probe. All I can picture is that this is not possible.

RandomSF said:

Right. That describes Manual mode well, and I understand that. My question is about how you would control in Automatic between just boiling and vigorous boiling, using a temperature probe. All I can picture is that this is not possible.

Click to expand...

You are correct. It is not possible to control boil strength with a temp controller. Gently simmering water is 212*F. Violently boiling-over water flying up and out of the pot is also 212*F.

You need pulse width modulation to control a boil.

Thanks. That's the only thing that made sense to me.

Brewmoor said:

I used this page to build my PWM. It is a very simple circuit. It too requires an SSR. http://home.highertech.net/~cdp/boilnew/boilnew.htm

Click to expand...

Thanks for the link. I think this meets my needs! I also batch sparge, so do not have a need for holding a continuous temp.

Brewmoor said:

If you can still find them. There is a GFI cord that I got on Ebay. It seemed to be the best option for me. Since I rent it was nice to buy a cheap breaker for the panel and have my GFI universal. It is built into the cord and has a standard 240v plug on the end.

Click to expand...

I would prefer to do this, as well, but did not see any such cable on Ebay. I'll keep looking though. I like the simplicity.

I found the link for you. Seems like they are still available. I really like this solution. The cord is super long and tough too.

http://cgi.ebay.com/30A-Ground-Fault-Interrupt-w-MPlug-GFI-Cable-FREE-SHIP-/350138274590?cmd=ViewItem&pt=BI_Electrical_Equipment_Tools&hash=item5185de131e

Thanks!

You guys wouldn't happen to have pics of your PWM set-ups, would you?

Reading CD's schematic, it looks like he is using 12vdc power through a separate 110v dc adapter plus the 240vac line.

lustrum said:

You guys wouldn't happen to have pics of your PWM set-ups, would you?

Reading CD's schematic, it looks like he is using 12vdc power through a separate 110v dc adapter plus the 240vac line.

Click to expand...

Yes... the PWM circuit runs on DC voltage, so you need a DC source for it.

I just used an old cell phone charger that I had in a box to supply the PWM circuit with DC.

I was able to take the plastic casing off the cell phone adapter and put the guts of it along with the littlw PWM circuit into a small electrical gang box from Home Depot (similar to this but MUCH cheaper) and covered it all with a plastic faceplate.

The gang box and faceplate cost about $1 total.
The adapter was free "junk" I had on hand.
The PWM parts cost about $3 from mouser.com.

I can take some pictures tonight for you. I am building three more of them for a new project I am working on. I just picked up some parts I was missing at lunch. I can also send you the PCB file too. You could just print it and put it on copper. I use ExpressPCB. It is free software http://www.expresspcb.com/

Let me know if this is the route you want to go. I will post the pics tonight.

I agree with Walker. Get a 12v wall wort and take it apart. Put the guts along with the circuit board into a project box. I isolated mine. I put all my high voltage into one sealed box and ran low voltage to my main panel. Peace of mind I guess for liquids and power.

Here are some picks from my rig. Very simple circuit. I will take better pics tonight.

Thanks for the info. I'd like to see the pics for sure. This is definitely going to meet my needs and seems like the most economical solution out there (aside from just unplugging the element!).

I also like the idea of breaking out the 110 vs 240 components. Did you use two boxes and gang them together? I'm trying to picture how it looks

As for a 555 timer, do you think this would work? It's a 12vdc CMOS timer. (click image)


I do was not able to find an "LM555" timer as CD suggests on his website.

You can find a lm555 chip at radio shack. It is a very common chip. It may have different markings but you want a 555 chip. Here is a model number that will work. It is the same chip Radio Shack sells for over $1. I would buy a few. They are a handy chip. http://www.mouser.com/ProductDetail/Texas-Instruments/NE555P/?qs=sGAEpiMZZMsFq5dYAzx%252bAIavvo06qkU3AL3wpiATMNo%3d

Here are two pics I took of one of the boards I made today. You can see it is a very easy circuit. PM me if you want a copy of the PCB file I made.

The first pic is the board and the template I printed from ExpressPCB. The second pic is a close up of the board.

I'm trying to build a controller for electric brewing Walker can you list the parts and part numbers and where you bought it so we can build a simple controller!
Thanks

ErinWhite said:

I'm trying to build a controller for electric brewing Walker can you list the parts and part numbers and where you bought it so we can build a simple controller!
Thanks

Click to expand...

See if this link works for you. I created a "shared" project on mouser with all of the parts that I ordered.
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=42dabdadd1

My little schematic:



Note: I couldn't find a little board to solder it to on mouser.com, so I actually went with an item from Radio Shack for that. It was a tiny circuit board meant to take an 8-pin DIP chip (the 555 timer in this case) with holes to insert and solder the other items in. The little board was about $1, but I can't find it on Radio Shack's website anymore.

edit: this is similar to what I bought from Radio Shack to solder it all to:
http://www.mcmelectronics.com/product/21-4610&CAWELAID=220241336

I love the GFCI cord, I have one too and it is very tough.

For my setup I just use one PID and one SSR, I don't have the power to run both 5500 watt elements at the same time anyway so I switch which one is plugged in to the controller depending on if I'm heating water in the HLT or boiling in my BK... also allows me to boil in the HLT if I wanted to. I can do electric but didn't want to get in to soldering circuit boards.

New setup will be a one vessel brew. Using BIAB along with electric. Not sure yet if I'll add a pump or not.

Thanks Walker

don't know why I couldn't find it yesterday, but here is the circuit board from RadioShack
http://www.radioshack.com/product/index.jsp?productId=2103799

Great Thanks!! I just ordered parts off of mouser.com and radioshack!!
Could you PM me some photos of your setup to help with the assembly? If you don't mind that would be most appreciated! Or email me located in my sig below!

ErinWhite said:

Great Thanks!! I just ordered parts off of mouser.com and radioshack!!
Could you PM me some photos of your setup to help with the assembly? If you don't mind that would be most appreciated! Or email me located in my sig below!

Click to expand...

Photos is something I can't really do. Mine is enclosed in a plastic gang box from HomeDepot and screwed to the back of the control panel door. It's all inside that gray box on the left in this picture.



I would have to disassemble things to get to the little circuit board and take pics. I'm not really motivated to take this apart.

I am planning to build another one of these, so I could take pics of that one as I do it, but I don't know when that will happen.

Walker said:

Photos is something I can't really do. Mine is enclosed in a plastic gang box from HomeDepot and screwed to the back of the control panel door. It's all inside that gray box on the left in this picture.



I would have to disassemble things to get to the little circuit board and take pics. I'm not really motivated to take this apart.

I am planning to build another one of these, so I could take pics of that one as I do it, but I don't know when that will happen.

Click to expand...

No Worries Thanks

Finally got around to building the PWM according to Walker's diagram. Got it all soldered together, hooked up the power, and NOTHING!

I checked and rechecked my wiring, all the things that were connected were supposed to be connected, but still nothing. I thought about it all day at work.

Luckily, I had another 555 laying in my box of stuff from a previous project. I swapped out the 555 Mouser sent with the one I already had. I now have a happy little test LED flashing at me.

The 555 Mouser sent was kaput.

Those little ICs can get zapped with static electricity or anything, really. I think it was Walker who said he uses a DIP socket to plug the chip into. I do the same thing, because it prevents over-heating the chip when soldering.

Anyway, kudos on the PWM and good luck putting it to use!

Walker said:

See if this link works for you. I created a "shared" project on mouser with all of the parts that I ordered.
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=42dabdadd1

My little schematic:

Note: I couldn't find a little board to solder it to on mouser.com, so I actually went with an item from Radio Shack for that. It was a tiny circuit board meant to take an 8-pin DIP chip (the 555 timer in this case) with holes to insert and solder the other items in. The little board was about $1, but I can't find it on Radio Shack's website anymore.

edit: this is similar to what I bought from Radio Shack to solder it all to:
http://www.mcmelectronics.com/product/21-4610&CAWELAID=220241336

Click to expand...

Walker, should the LED on the SSR turn on and off with the setting of the Potentiometer? I finally built one and the SSR led is on continuously and doesn't turn on and off!

ErinWhite said:

Walker, should the LED on the SSR turn on and off with the setting of the Potentiometer? I finally built one and the SSR led is on continuously and doesn't turn on and off!

Click to expand...

Yes. The LED built into the SSR is an indicator of when the SSR is "on". It should be turning on and off based on the setting of the potentiometer. If your LED is constantly on, then something is wrong with the circuit.

Walker said:

Yes. The LED built into the SSR is an indicator of when the SSR is "on". It should be turning on and off based on the setting of the potentiometer. If your LED is constantly on, then something is wrong with the circuit.

Click to expand...

Damn I will have to double check the schematic again Any ideas on what might be wrong?

ErinWhite said:

Damn I will have to double check the schematic again Any ideas on what might be wrong?

Click to expand...

Off the top of my head... Possibly a mis-wired potentiometer.

An "ALWAYS ON" LED means that the 555 timer is ALWAYS trying to drain the green capacitor but is failing to do so, or the capacitor is instantly re-charging after being drained (similar to the "100%" setting when it's working properly).

If you bought the same part from Mouser.com that I did, it had a total of 5 terminals on it. Two terminals form an ON/OFF switch that you could use for power into the device if you want. The other three terminals form the three tap points of the poteniometer.

There are a couple of ways that you could mis-wire the potentiometer such that it could result in an always on SSR LED.

Walker said:

Off the top of my head... Possibly a mis-wired potentiometer.

An "ALWAYS ON" LED means that the 555 timer is ALWAYS trying to drain the green capacitor but is failing to do so, or the capacitor is instantly re-charging after being drained (similar to the "100%" setting when it's working properly).

If you bought the same part from Mouser.com that I did, it had a total of 5 terminals on it. Two terminals form an ON/OFF switch that you could use for power into the device if you want. The other three terminals form the three tap points of the poteniometer.

There are a couple of ways that you could mis-wire the potentiometer such that it could result in an always on SSR LED.

Click to expand...

I did buy the same potentiometer from mouser.com. it has a prong on each side and 3 prongs together out of the center. Which prongs should be used?
Thanks I really appreciate the help:rockin:

the three that are grouped together.

Walker said:

the three that are grouped together.

Click to expand...

Thanks Walker!! That has to be whats screwed up then. I was using the two outside ones not the 3 grouped together. I'll switch that over tonight to see if something else isn't screwie.
Thanks for the quick response to my ameture questions:rockin:

ErinWhite said:

Thanks Walker!! That has to be whats screwed up then. I was using the two outside ones not the 3 grouped together. I'll switch that over tonight to see if something else isn't screwie.
Thanks for the quick response to my ameture questions:rockin:

Click to expand...

Ok... but... the circuit requires three connections to the potentiomenter. Were you using the two outside ones and then one of the center three, or do you only have it connected at two places?