Tag Archives: Thermistor

Mini-BIAB Electric Turkey Fryer Mod–Part 3

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Now that I have finished putting together the necessary circuits to read the thermistor and control the heating element, I need to provide some simple circuits for the user interface.

The Front Panel

Below is a mock up of what I want the front panel to look like:

ControlPanel

At the top right I will have a 16×2 LCD Display with a series of switches to control the heating element and set temperature for the temperature monitoring service.

  1. Heater Override – This switch will allow the user to cut off the return signal from the main circuit board back the Turkey Fryer 12V Relay to keep from accidentally dry firing the heating element.
  2. Heater Engage – This push button is used to signal the Netduino that the heater can be engaged and until pushed will not allow the Temperature Service to turn the heating element on.
  3. Heater Dis-Engage – This push button is used to signal the Netduino that the heater should be dis-engaged immediately, kind of like an all-stop button.
  4. Temp Up – This push button will raise the temperature monitoring service’s set temperature by one degree.
  5. Temp Down – This push button will lower the temperature monitoring service’s set temperature by one degree.

This is a pretty simple interface, but it provides all the basic necessities to control the Turkey Fryer during a brewing session.

The Main Board Connections

Below is the schematic for the main circuit board of the system along the right hand side you can see the various connectors that will be used to wire the switches into the Netduino:

Main_Board_Schematic

I have wired each of the push button switches using a pull-down resistor configuration, this keeps the signal to the Netduino ports low until the push buttons are pushed connecting the ports to 3.3V. The switch connections are wired into a series of header pins that will be used to connect each switch to the main board.

I have also ran Netduino Pin5 to a second screw terminal that connects to a Peizo speaker that is used to provide an audible signal when the temperature of the Fryer reaches the set temperature and again when a mash step completes. I’ll explain the code in a later post.

There is one last connector in the upper left of the schematic and this one connects the main circuit board to the LCD Display Daughter board. This connector extends the Netduino SPI ports 10, 11 and 13 to the daughter board along with 5V and Ground which are used to power the LCD Display.

In the next post I’ll cover the LCD Display Daughter Board and how you can use 3 Netduino pins to drive a 16 x 2 LCD Display.

Till next time, stay sanitized and keep an eye on those fermentation temps and I’ll catch you for a pint around the keg.

Jim Lavin – Otaku Brewer

The Search for a Counter-Top Electric Brewing System

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While I’m busy working on my full-scale all-electric brewing system, I figured it be nice to have a small counter-top electric brew system that I could use to continue brewing. I also thought it would be a good proto-type for the larger system I’m building.

While discussing the idea with a couple of folks from the North Texas Homebrewers Association, I came up with a couple of ideas:

  1. Use a couple of Electric Coffee Urns for the brewing vessels.
  2. Use an Electric Turkey Fryer for a simple Brew-in-a-Bag system.
  3. Scavenge the parts from an old commercial Coffee Maker I just have setting around.

I have a couple of goals that I want to meet:

  1. Keep the system small enough to fit on a counter top or kitchen table.
  2. Everything has to run off of a single 120 Volt AC Outlet.
  3. Has Temperature Control, so I can do step mashes.
  4. Big enough to brew at least a 2 Gallon batch at a time.
  5. Keep it as cheap as possible.

Using Electric Coffee Urns for the Brew System

To experiment with the first concept, I picked up a 40 Cup Electric Coffee Pot from my local Wal-Mart. This has just enough capacity to brew a 2 Gallon batch if I plan on making a three vessel system.

40_cup_coffee_pot

The coffee pot will hold a little over 7 quarts of water, which is just enough strike water to mash around 5 pounds of grain. However, I think this is pushing it a little, the 7 quarts of water only leaves about an inch of head space without adding the grains. So my feeling is to really do a full 2 Gallon batch a 50 Cup or larger Electric Coffee Pot is a must.

I also did a couple of tests to see how hot I could make the water and It pretty much tops out at around 175 Degrees F in a little under 30 minutes. Now this is not bad for a Hot Liquor Tank or Heated Mash Tun, but it will never be good enough for a boil kettle.  I pulled the bottom off the Coffee Pot and found what looks like a thermistor or temperature limiting resistor that cuts the power to the heating element. If I could find a way to bypass the thermistor, I’d probably be able to bring 2 Gallons of water to a boil. The 40 Cup unit has a 1000 Watt heating element, but I’ve looked at a couple of larger units that have 1500 Watt heating elements which should probably be more than enough power to bring 2 Gallons of wort of a boil.

Another issue I have with the Coffee Pot is that I still have to come up with a temperature control system that would allow me to control the temperature of all the vessels by interrupting the power to the heating element as the target temperature is reached. Now this is not a big issue, since this is one of the main components of my larger system that I want to build out and perfect before I spend a lot of money and find out that my design won’t work.

My last issue with the Coffee Pot is that I’ll need some sort of pump system or gravity feed structure to move the water from the Hot Liquor Tank to the Mash Tun to the Boil Kettle. This will add expense to the overall system which kind of goes against my last goal to keep things as cheap as possible.

The nice thing about the construction was that the spigot is attached to the pot using a metal nut around a half-inch in diameter which would make replacing the spigot with a more acceptable ball valve or bulk head fitting pretty easy.

Right now I’m estimating that the entire system will cost about $500 to build out fully with all the temperature control and miscellaneous components. So, until I’m fully convinced this is the way to go, I’m going to put the Electric Coffee Urn Brew System on hold and check out some of my other options.

Till then, keep an eye on those temps!