Induction Hack: Add an external probe

[Weezy]

This is something I had been mulling around for a long time. It was a side project, as I have too many other big and time consuming projects to talk about...but I never liked immersion elements. More cleaning, worry of scorching, etc. Anyway, when I picked up a used Avantco IC1800, I was excited because it has temperature settings for every 10 degrees through the typical brewing range; 140, 150, 160, 170. The first thing I did was put a pot of 2 gallons of water on the thing, set it to 140F and wait. I came back in 45 minutes and it was 173F by my thermometer. Scrap that idea!

That one was a crappy, cheap, used one off Craigslist. $40. They must have used it for deep frying because it was coated with grease. It died. But that was a blessing. I tore it apart.

The blob of white stuff is thermal grease that transfers heat from the underside of the glass lid to the thermistor (not a very effective setup). The thermistorthat is nestled on the top of the black post at center:

The center part is the sensing section. It's essentially a fancy resistor that varies resistance based on its temperature. Putting a meter on this shows it at about 275K ohms at room temp.

Here's where it attaches to the board:

When I saw it was a nice simple, removal plug, the wheels started spinning. I immediately started looking for ruggedized thermistors with the approximate resistance range. I enlisted the help of a few EE friends with supplier contacts. We came up with nothing.

Then another light bulb went off. Why not just use the existing probe with added wire and a home brewed thermowell?

I ordered some nonconductive thermal grease from Omega, and a 1/2" NPT threaded thermowell from Brewhardware.

I had an unused, cheap PT1000 thermistor that I cut to use the wire. I could have easily just used hobby wire but this is a sheathed two-wire set at the appropriate gage. win-win.

Only the sensing section needs to be exposed. The surrounding, bare wire, if shorted would likely fry the board (this is why it would have been nice to find an off the shelf ruggedized thermistor replacement) So I coated the bare wire with liquid electrical tape:

I cut the probe wires closer to the board mount, being sure to leave enough wire to solder to the spliced in extra wire. For the board side, I drilled a hole through the bottom of the cooker (the IC1800 has a flat plate on the bottom that simply unscrews).

For the probe side and the installation in the thermowell, I about 1/3 filled the well with the grease, inserted the probe as far as it would go, then siliconed the outside end to fix it and waterproof it.

IT'S ALIVE!!!

FIRST TEST?

First of all, I didn't release the factory installed smoke. It ran. I put a 12 quart pot on it with 1 gallon of water. I set it 160F, mash-in temp, and let it go. I got 2F/minute and it did not get to 160F. Let me start at the end, then I'll give the details. The temperature settings on the machine do not match the actual temps that the water will be heated to. But this isn't a big issue because the temperature settings now nicely coincide with consistent water temps, thanks to immersing the probe.

setting vs. water temp
160F = 130F
170F = 140F
180F = 150F
190F = 160F
200F = 170F

Now the details. The water must be recirculated or at least quite frequently stirred. Without recirculation, the cooker will overshoot the above listed temp by 4-5 degrees, then shut off and the temp will fall back for the listed temp, before kicking back on. When I had it set at 170F, it would cycle from 144-145 to 139-140. So I started stirring and it stayed at 140-141. Although, this yoyo effect may be dampened with grain and more water (more thermal mass) and a insulation wrap.

$230 is better than $1,000 for a 2600W Dipo with a factory external probe.


I have not brewed with this yet. I need to get the probe mounted to a pot. I plan to build two of these (likely 3500 watters), and use the Brutus 20 method. Mash Tun heated to 160F for mash in, then turned down for 150F mash. Sparge Pot on the second cooker heated to 170F. After a short mash, start cross recirculation with both set to heat to 170F.

 

[cliffhanger1821]

Nice! Thanks for the write up!

 

[dyqik]

Nice

Did you measure the resistance of the temperature sensor at other temperatures? That might help you identify the part so that this modification could be done without removing the original sensor from the induction cooktop.

If you can get an R-T curve for the sensor, then it's probably possible to use a microcontroller/Arduino/whatever to fool the cooktop into reading a different temperature, so you could get continuous temperature control.

 

[Weezy]

Yes, you could most likely be able to fudge resistances to the PCB. All you'd need to do is mimic a low and a high value to serve as on/off. Say, room temp and boiling. Although I have no idea what hardware and software youd need to tackle this. Thats beyond my knowledge. I did not test any other resistances. Interesting idea.

 

[AnOldUR]

Found my way here from your post in the Induction Mashing thread.

I've recently been playing with induction mashing with my IC3500 and found the temperature setting to not be of much value. With my last mash, I had better luck ramping and holding temperature by manually adjusting the wattage, but I like the idea of hacking the probe. Since it's BIAB, I'm thinking that something that can be dropped over the side of the kettle, directly in the mash, might work better than a probe that would rest outside of the bag.

Have you had any luck finding a sensor to use in place of the factory one? I don't know anything about how they work, but would any probe with the same resistance work?

My only concern is that this sensor is also used to shut down the unit if there is an overheating condition in order to prevent damage.

 

[Weezy]

You could probably rig something up in a long ss tube for a drop in sensor. It's just preference. Measuring through the side is just as accurate. Remember, you need to actively stir if not continuously recirculate to avoid hot & cold spots on any system with active, sensor-driven heating. So exact probe location isn't especially critical.

No I couldn't locate a replacement probe. I even contacted Avantco and they passed on some questions to their manufacturer, but never heard back.

 

[rudylyon57]

Very interesting work. Thanks for sharing. Just a thought...I suspect the poor calibration of the unit could be tweaked by altering the RTD resistance with a fixed resistor (in parallel with RTD to reduce total RTD resistance) since there is a fairly consistent 30F offset in the mash-temp range. Better yet, it would be cool to get further into the controls so a PID could be employed for control?

 

[Weezy]

I doubt a PID alone wouldn't work. We'd need to evaluate what voltage and resistances are sent through this thermistor at different temps, and find someway to mimic those signals via variable resistance controller or something else beyond my experience.

 

[rudylyon57]

What I was implying was not using the PID to mimic the RTD, but drilling deeper into the controls to the level where the induction circuit is turned on or off...that's where the PID and perhaps an SSR might do the trick. Just throwing something at the wall though.

 

[Weezy]

Yeah, I know exactly what you meant, I just wasn't explaining it well...cuz I'm a layman too. The power output to the coils, in my ignorant terms is, is in some sort of wave form generated by circuitry on the board. Basically, you have power coming into the board -->magic happens in the pcb--->special power comes out of board to the coils. I don't see how we easily splice into that scenario.

I do have a dead one, I could really tear it down and investigate further and post pics.

 

[cheesecake]

Any updates on this?

 

[Weezy]

Just cross linking to my follow-up of this project:

https://www.homebrewtalk.com/showthread.php?t=598424

 

[Weezy]

Well, I can't edit the OP anymore but something came up in another thread that is game changing on this subject. Apparently, this Adcraft induction cooker has true manual control.

http://admiralcraft.com/product/ind-c120v-induction-cooker/

Meaning, it can be controlled by an external temperature controller that will control this thing via it's power plug.

There's also a 3000W version, which would necessitate a panel with a relay for the higher voltage.

The point is... DON'T BOTHER HACKING AN AVANTCO (unless you already have one)!

 

[bisforbrew]

The plug connector is a NEMA Plug
5-20P. Do they make ink birds that can handle that? also can a regular outlet handle 20 amps?

 

[Weezy]

As far as 20 amps, sure. My brewery is set-up with 12 gauge wire and 20 amp GFI outlets:

the sideways plug is the 20 amp tip off. elctronic equipment that requires 20 amps will come with that one prong sideways. This cooker is 1800W, which is 15 amps. So it should just be the standard plug shape, which still falls under the 5-20 umbrella, i believe. But you do want to run it on a 20A circuit, for safety. You never want to run a circuit with continuous load at its max rating.

The inkbird I was thinking about is only 1500w, so scratch that unless you want to never run the cooker above 1500 W. Just look for 15 amp, 1800 W temerature controller solutions that suit your preference. Ranco is 15A is think. They're out there. Assuming you want a simple solution like those plug-and-play controllers. There's nothing wrong with full PID or BCS control. If you're doing 5+ gallon batches, you're going to want the bigger 3000W model with a purpose built controller that can handle the high voltage and wattage.

 

[bisforbrew]

Yeah I don't plan of doing bigger batches any time soon. 2.5 gallons would be the biggest. I was hoping to find a solution I can just plug in a regular outlet. Ideally a manual induction burner that runs on a 15 amp circuit with a pump that can do the same for recirculating the mash.

 

[Weezy]

Yeah I don't plan of doing bigger batches any time soon. 2.5 gallons would be the biggest. I was hoping to find a solution I can just plug in a regular outlet. Ideally a manual induction burner that runs on a 15 amp circuit with a pump that can do the same for recirculating the mash.

This is the only truly manual control induction I've heard of. You could keep it set at 1500w or so and use inkbird on a 15 amp circuit. Just never use more than that. 1500 will boil your batch size just fine. GFI outlet is smart too.

 

[bisforbrew]

I guess my real issue is, I live in a rented condo and I can't really change any of the circuits in the condo. So standard everything. I do however have a standard NEMA 5-15 GFI outlet in the kitchen I can use

 

[dyqik]

If the kitchen was wired recently, that outlet will be on a 20A circuit and breaker. That's been a code requirement for a while.

 

[bisforbrew]

If the kitchen was wired recently, that outlet will be on a 20A circuit and breaker. That's been a code requirement for a while.

hmm, these apartments were probably built in the late 80's is my guess. I guess i can take a look at my breaker. If its on a 20 amp circuit then, my hope is that the wire used is a thick enough gauge to handle the 20 amps. Wouldn't want to cause a fire or anything.

I guess if everything is good an adapter to an ink bird running under 1500 watts should be safe enough right?

 

[dyqik]

If it passed any kind of inspection, the wiring on a 20A breaker will be 20A capable. That's the point of the code change (to allow two 1100W countertop appliances to run on a single kitchen circuit without overloading the wiring or flipping the breaker, which often leads to people doing stupid things to prevent nusiance trips). The only remaining piece that is a potential risk is the outlet itself. I'm personally OK with running a 15A outlet with good wire connections (i.e. after I've inspected them) at a bit above 15A for half an hour or so, but that's an entirely personal decision. I also assume that the code change that allowed 20A breakers to feed 15A pattern outlets took that risks of an overcurrent on an individual outlet into account (you could easily plug two 1100W appliances into a double outlet, for example, without tripping the breaker).

By the way, the induction plate's power draw will be rated at 120V, which means it draws 15A at 120V to give 1800W power. I'm not sure if these plates are a purely resistive load like a heating element, in which case the draw will never be more than 15A, or if they draw more current at lower voltages to give constant power output as the wall voltage changes.

When you are controlling the temperature, you should probably turn the induction plate down to low power output anyway, to prevent overshoot and save relay cycles on the Inkbird controller. In any case, I can't see you running the plate at full power for 3 hours solid, so I don't see the 80% of circuit capacity rule being relevant. You should be sure that nothing else is on the circuit though while you are using it.

 

[Paul vL]

Great Idea,
I have a regular kitchen 4 zone induction plate from Bosch that I use for my Brews and Cider.
But I'ld like to control the temperature, preferably with various heating programs/schedules.
So I took your great idea, but instead of removing the thermistor (11.8kOhn) itself, I leave it in to protect the plate against overheating.

But in series I plan to put in (for 1 or 2 zones) a mini earphone socket (that shorts when the plug is out)
When the plug is in I can then via a temp controller or Arduino and a external temperature probe trigger a relay on/off.
I tested when the thermistor is disconnected, my plate doesn't shut off for approximately a minute, but starts blinking.
so if I have a 1-2 sec interval, I can reduce the power to ~1/60-1/30 (~2%-3% of the max power).
This should do the trick, while the safety stays in place.
I don't know if this works for the other kitchen plates to.
to be continued.
I might try to hack the control board, but that my be a little out of my league. I know the chips in there so I'll do some research.
Stay safe
Paul

 

[markgm]

My guess is the thermistor in the IC3500 is a 100k Ohm NTC (resistance goes down as the temperature increases) glass encapsulated thermistor, something like this: https://www.digikey.com/product-detail/en/us-sensor-littelfuse-inc/104JG1F/615-1028-ND/1014556. The thermistor in my IC3500 reads around 100k Ohms at 77 degrees, and 135 at 63.5 degrees.