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seperating the heating element
jedovaty
Top  #1 Print Post
Posted on 12/29/2011 1:11 PM
Hi,

I don't like how the TO turns off and on and off an on - I'd like to control the level of heat, which implies something like a variac or router speed control. Understood.

Is it any more challenging to seperate out the heating element of the TO than for a popcorn popper? I had previously done that on my "The Poppery", before I scrapped the project and found a TO for a reasonable cost locally.

Thank you,
Jano
Edited by Koffee Kosmo on 01/05/2012 4:37 PM
 
BenGeldreich
Top  #2 Print Post
Posted on 12/29/2011 2:44 PM
Jano,

I have split the heat from the fan on a Poppery 1 and two different TO models; Flavourwave and a GC. Ed B.(farmroast) has some excellent info and pictures about the GC mod on this thread.

http://www.coffee...ast/329082

Not sure if Ed did but I added a ground to my Fan wiring. I found that there was quite a bit of juice coming from the TO's metal enclosure on both models without the ground.

Ben
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
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jedovaty
Top  #3 Print Post
Posted on 12/29/2011 9:43 PM
Perfect, thank you! I need to find a variac, they are pricey new though. Where does one find rheostats?
 
Koffee Kosmo
Top  #4 Print Post
Posted on 12/29/2011 10:43 PM
Its the thermostat that switches the element on and off
One needs to disconnect it and you can do one of two things

1) Control with on and off switch manually
2) Connect to a variac for precise temp control


My preferred option is to have the thermostat disconnected by a qualified person and run the TO via a variac
Its not only very precise its also safer

KK
Edited by Koffee Kosmo on 12/30/2011 6:14 PM
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
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JackH
Top  #5 Print Post
Posted on 12/30/2011 4:03 AM

Quote

jedovaty wrote:
Perfect, thank you! I need to find a variac, they are pricey new though. Where does one find rheostats?


Try to get one of the older (USA made) types from Superior Electric, Staco or General Radio. I have heard that the newer types are made in China and have reliability issues.

None of the older units are being made anymore except for Staco and they are very expensive new. Ebay is where I got my used Superior Electric. Rugged and made to last.
Edited by JackH on 12/30/2011 3:26 PM
 
allenb
Top  #6 Print Post
Posted on 12/30/2011 7:43 PM
Another option for manual control (much more affordable than a variac) mentioned in other threads before is the so-called infinite switch used on stove top coil elements.

http://midwestapp...googlebase

It comes in 120 and 220 volt versions and can handle the current demands of a TO. The further you turn the dial the longer the on portion of the duty cycle. If you turn all the way around you hit continuous on. This would work great in a recirculating air stream as in a turbo oven which doesn't need a ultra fast on-off time base. They are also very durable and reliable.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
allenb
Top  #7 Print Post
Posted on 12/30/2011 7:54 PM
One more thing on the infinite switch. The on-off period would not resemble the long switching lag time of the stock TO thermostats. They switch according to temperature of the air surrounding the bi-metal and can remain off too long and cause large swings.

The cycling of an infinite switch is caused by the bi-metal heating up as current passes through it during normal operation and the frequency of cycling is varied by the dial exerting more or less tension on the metal.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jedovaty
Top  #8 Print Post
Posted on 01/04/2012 9:46 AM
I like the infinite switch idea, because it allows me to retain existing wiring and don't have to lug around that big variac. My TO is 110V, as are my outlets. What happens if I use a 220V infinite switch? I was able to grab one locally for very cheap, and was going to try and get all my questions answered in a proctored environment on my own, and got as far as taking it apart, but now I have second thoughts because I ran out of coffee smile It seems like it "should" work, because according to what I've read, they rely on current, not voltage.. but then, I'm a salesguy.

How much of a temp fluctuation do the infinite switches introduce? The TO switch gives me about 30F over then 30F under, I'm hoping this thing can tighten that -- if not, I'd rather just go variac route.
 
JimG
Top  #9 Print Post
Posted on 01/04/2012 11:50 AM
If you wish, you can manually control the heater using your TC4.

In addition to the TC4/Arduino, you would need a single turn 10K potentiometer and a solid state relay (standard zero cross switching model).

The aCatuai application is set up to read the position of the swipe on the pot and adjust the duty cycle on OT1 accordingly. I'm controlling the heater on my Hottop this way.

Jim
 
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jedovaty
Top  #10 Print Post
Posted on 01/04/2012 12:41 PM
Jim -- that's sounds really cool, but it might be a little advanced for me at this stage. Some questions on it - how much of a temp swing exists over the desired temperature? How exactly is it wired?

TC4---10k Pot---Relay---Heater

? Specs on the relay? I'm going to the electronics store today to pick up an extra female electrical input in case the infinite switch doesn't work, so I can at least hook up the horror fright router speed control until I get a variac.

Will have to see if my arduino-BT will be able to handle the aCatuai, too.. lots of work, oh, booger, why does my day job get in the way? smile
Edited by jedovaty on 01/04/2012 12:57 PM
 
JimG
Top  #11 Print Post
Posted on 01/04/2012 3:33 PM

Quote

jedovaty wrote:Some questions on it - how much of a temp swing exists over the desired temperature?

The amount of temperature swing will depend on how good you become at adjusting the power going to the heater. The setup I described, using aCatuai, effectively replaces the router speed controller. So it is still manual control.

Quote

jedovaty wrote:How exactly is it wired?

The 10K pot gets connected to the ANLG1 header on the TC4 (3 pins). The middle pin on the ANLG1 header should be connected to the "wipe" on the pot, normally labeled on the pot as "3."

The "+5V" pin on ANLG1 gets connected to pot pin 2.

The "GND" pin on ANLG1 gets connected to pot pin 1.

If the power setting goes the wrong way when you dial the pot, then swap the last two connections.

The idea is to use the pot to put a signal between 0V and 5V on the middle pin of ANLG1.

Most SSR's (see below) get connected like this:
- TC4 OT1, positive --> SSR terminal 3
- TC4 OT1, negative --> SSR terminal 4
- mains line (hot) --> SSR terminal 1
- SSR terminal 2 --> heater(+)
- mains neutral --> heater(-)

Quote

jedovaty wrote:? Specs on the relay?


The relay specs should be:
- solid state relay (SSR)
- controlled by DC voltage (typical usable range is 3V to 32V)
- "load" side of the SSR should be for AC current, and rated for at least 10A (assuming 220V mains) and 240VAC.
- it should be the type that switches the load on or off at the zero crossing point of the AC power.

Jim
 
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jedovaty
Top  #12 Print Post
Posted on 01/04/2012 5:07 PM
Jim thank you on the wiring!


Quote

JimG wrote:
The amount of temperature swing will depend on how good you become at adjusting the power going to the heater. The setup I described, using aCatuai, effectively replaces the router speed controller. So it is still manual control.


How much of a temp swing does aCatuai bring in then? On the unmodified TO, without me doing anything, the swing was 30F in both directions. When I got my hands into the mix, I could do about 15-20F over and under shoot, which would probably get better with experience (note I've only roasted about 8lbs so far).

Maybe I'm not understanding this? Please excuse my newbie questions, and I appreciate your patience with me. I'm assuming with aCatuai, I tell it to keep the temp around 450F, it will work by shutting the relay on/off through the 10K pot, based on the ET or BT probes. Do I have any say in how much it should over/undershoot the target temps?

Further addition to complications. Hopefully I have this right:
Variac and router speed control affect the voltage and/or current to the heating element, so it makes it heat hotter or less hot, therefore we can get more accurate temps with small swings in temp, whereas with the stock TO and the infinite switch, these turn the element on/off to achieve the target temps and average them out. You wrote the aCatuai replaces the router speed control, so it falls into the like-variac category? But then the relay switches on/off, perhaps the software allows it to be more accurate.. oh, I'm confused.


EDIT -- I built a sous vide machine with a PT100 probe and a PID controller. Does the aCatuai software kind of work like the PID controller?
Edited by jedovaty on 01/04/2012 5:59 PM
 
Unta
Top  #13 Print Post
Posted on 01/04/2012 6:47 PM
Lets see a sous vide machine thread..!
Sean Harrington
educate.
 
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allenb
Top  #14 Print Post
Posted on 01/04/2012 7:45 PM

Quote

jedovaty wrote:
I like the infinite switch idea, because it allows me to retain existing wiring and don't have to lug around that big variac. My TO is 110V, as are my outlets. What happens if I use a 220V infinite switch? I was able to grab one locally for very cheap, and was going to try and get all my questions answered in a proctored environment on my own, and got as far as taking it apart, but now I have second thoughts because I ran out of coffee smile It seems like it "should" work, because according to what I've read, they rely on current, not voltage.. but then, I'm a salesguy.

How much of a temp fluctuation do the infinite switches introduce? The TO switch gives me about 30F over then 30F under, I'm hoping this thing can tighten that -- if not, I'd rather just go variac route.


Not sure if a 220V infinite switch will work with 110 or not. I'm sure it will function but not sure how the duty cycle timing will be affected.

How much temp fluctuation? Remember that an infinite switch is nothing more than a cycling device that varies the amount of time the element is on. Lets say you've got the dial turned up to half way and the element is on for 5 seconds and off for 5 seconds. If you're roaster doesn't lose gobs of heat through it's lid and pot then you won't see much swing in your ET. Definitely not 30 degrees. As you turn the switch further up there will be less off time and more on time with even less potential for temp swing.

The thing to remember is the control that comes in the TO is a bimetal stat that is trying to maintain a setpoint by heating up to a temperature then allowing it to fall so many degrees over and over while at that setpoint. All you can do is vary the temperature at which it cycles around.

With a variac, infinite switch or TC-4 set up for manual control all you are doing is manually controlling how much power the element is allowed to deliver to the air. It's up to you to keep moving the dial on these setups to keep the ET where it will maintain the desired bean rate of rise.

I think some of the confusion arises from hearing about two different types of heat management. One is manually, incrementally increasing ET by small tweaks upward to maintain rate of rise (RoR) of the coffee throughout the roast. The other method is pre-selecting ET plateaus to accomplish the same thing as with the Gene Cafe. With this method one might bring ET to 350 for 3 minutes then raise it to 400 for x minutes, 450 for x minutes until the roast is finished. This is also what has to occur when using a TO with a bimetal stat.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
jedovaty
Top  #15 Print Post
Posted on 01/05/2012 1:59 AM
Thanks Allen. The 220V infinite switch did not work in my setup with the 110V lines - didn't turn anything on, oh, well. I managed to rewire my TO: removed the timer, and put the fan and heating element on their own toggle switches, and added a second power plug so I can use either the router speed control or a variac. It was a pain putting it all back together, ended up with an extra screw, and I got the two lights mixed up -- so the switches light up the opposite light, ooops! The heating element appears to be affected by the router control, so I'm pleased this worked out smile

I think my confusion above really lies in how aCatuai works. Reading Jim's post more carefully, it seems the user still manually and physically changes the temp by adjusting the 10k pot, and the software simply logs what's been done? I was thinking it behaved more like a pid controller in that you tell the software, "get to and maintain X temp" and it does the rest by reading either the BT or ET.
Edited by jedovaty on 01/05/2012 2:00 AM
 
jedovaty
Top  #16 Print Post
Posted on 01/05/2012 2:11 AM
Sean, nothing interesting on the sous vide, I followed internet directions, but used a water heater element instead that was protected by a large commercial whisk jb welded around it. We've enjoyed some amazing steaks from the local butcher, and had fun experimenting with other foods.
 
JimG
Top  #17 Print Post
Posted on 01/05/2012 8:53 AM

Quote

jedovaty wrote:I think my confusion above really lies in how aCatuai works. Reading Jim's post more carefully, it seems the user still manually and physically changes the temp by adjusting the 10k pot, and the software simply logs what's been done? I was thinking it behaved more like a pid controller in that you tell the software, "get to and maintain X temp" and it does the rest by reading either the BT or ET.

aCataui does not have any PID control capability. It wouldn't be too hard for someone to add basic PID to aCatuai, but manual control suits my roasting needs better.

Jim
 
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miamichillin99
Top  #18 Print Post
Posted on 05/16/2012 6:56 PM

Quote

BenGeldreich wrote:

Jano,

I have split the heat from the fan on a Poppery 1 and two different TO models; Flavourwave and a GC. Ed B.(farmroast) has some excellent info and pictures about the GC mod on this thread.

http://www.coffee...ast/329082

Not sure if Ed did but I added a ground to my Fan wiring. I found that there was quite a bit of juice coming from the TO's metal enclosure on both models without the ground.

Ben


That link no longer has the instructions. Can someone provide some schematics please.
 
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