THE FRANKENGRIDDLE PROJECT

It started out innocently enough with a griddle & burner from a 1970's Wolf stove...

The griddle area is about 11" x 25" with a gutter and drain on one side. The slab is 3/4" thick and the griddle weighs about 48 lbs. It looks like it should be able to cook a fair bit of bacon at once.



I mounted it on top of an old stainless steel food service cart with nice heavy duty castors so it's mobile.



There's room inside for a propane bottle. The burner control knob is on the front and there's a removable drip tray on the left.



Mmmmm...  It makes breakfast!



I guess the project wouldn't have been too silly if I had just left it at that.

But wait, there's more....


I was poking around through my "junk box" and found some other stuff that looked interesting.
A type K temperature probe, a small stepper motor from an old printer, a stepper driver circuit from an old discarded project, a 16 x 2 LCD display, and a microcontroller board I designed and built for another project.
The controller board contains a 16F887 controller, a DS1302 real time clock, a 24LC128 EEPROM, 5 volt regulator, and some MOSFET output drivers.

So I stuck that pile of hardware together with a little solder, connected the stepper motor to the gas valve, hacked up a few lines of code for the processor and presto...






A temperature controlled griddle with a digital display!


The processor reads a type K temperature probe that's embedded in a hole in the side of the griddle. The stepper motor has a 6:1 gear reduction to the gas valve shaft and with the half step driver that gives a resolution of 0.15 degrees of valve rotation. The temperature is user adjustable from 275 to 450 (F) and the processor uses a PID routine that gives very good control of the temperature.





When first powered up the LCD shows a friendly greeting message and then it displays the current griddle temperature, the user adjustable setpoint, the current time, and the current gas valve position.




The menu button allows access to select auto or manual control mode, time set mode, backlight brightness, and adjustment of several variables used in the PID calculations.





It was kind of a crazy project but it works very well and it makes excellent woven bacon!





And Frankengriddle makes English Muffins too!



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Frankengriddle is still a work in progress and hardware & firmware updates are being made regularly.

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Current Frankengriddle features include:
  • Gas Griddle from a 1970's Wolf stove. Griddle is approximately 11" wide x 25" long x 3/4" thick. Weighs 48 lbs. Has a gutter and drain on one side with a removable container to catch the grease.                                                                                                                                                                                             
  • Griddle is grafted on to a stainless steel food service cart with heavy duty castors and room for a 5 gallon propane bottle inside.                                                                                                                                                                                                                                      
  • Stepper motor driven burner valve with16F887 controller gives excellent temperature stability and fast response time to sudden load changes.                                                                                                                                                                                                                    
  • Type K temperature probe embedded in griddle gives accurate temperature control.                                                                                                                       
  • Processor controlled auto-ignition system with thermocouple pilot verification.                                                                                                                                
  • LCD display shows current griddle temperature, setpoint temperature, current gas valve position, and current time.                                                                                                                                                                                                                                                           
  • Onboard real time clock with battery backup.                                                                                                                                                                        
  • Data logging capability records the griddle temperature, temperature setpoint, and valve position. User adjustable logging frequency (default = every 10 seconds). Up to 2600 data points. Data can be downloaded to a PC via RS232 and imported into spreadsheet, etc.                                                                                                                                                        
  • Easy to use menu routine allows user to set desired temperature, set current time, access "auto" or "manual" control modes, adjust LCD backlight brightness and contrast, turn data logging on & off, adjust certain PID parameters, and turn "alert" sounds on & off.                                                                                                                                                                                                                                                                
  • Makes an "alert" noise if griddle runs out of propane.                                                                                                                                                                                                
  • Plays the opening riff from "Smoke on the Water" when the griddle gets up to temperature.                                                                                                               
  • DB9 connector on front panel allows download of logged data or upload of firmware upgrades.                                                                                                                   
  • Runs on DC power source... 10.5 - 16 volts, 1 amp max. (500mA max with battery charger off)                                                                                                                
  • Onboard 12 volt 7AH battery provides over 8 hours of continuous use without external power.                                                                                                             
  • Onboard battery charger to charge internal battery. 16F684 controlled charger can provide up to 13.8 volts output with only 10.5 volts input. Gives precision control over battery charge current and terminal voltage. Plug into any 10.5 to 16 volt source capable of supplying at least 1 amp to power griddle & battery charger. (12 volt 1 amp "wall wort" is recommended from AC power source)



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Materials you will need to build this project:


One griddle and burner from an old Wolf stove. (or substitute whatever you have laying around)

One stainless steel "food service cart" on wheels. (or substitute whatever you have laying around)

One small stepper motor from an old printer. (or substitute whatever you have laying around)

L297/ L298 stepper driver chipset. (or substitute whatever you have laying around)

One 16 x 2 LCD display. (or substitute whatever you have laying around)

One home built controller board. Mine has a 16F887 processor, real time clock, and plenty of EEPROM. (substitute whatever you have laying around)

Assorted bits of angle iron, sheet metal, pipe, screws, switches, wire, solder, & heat shrink tubing. (Substitute whatever you have laying around)

Plenty of bacon for testing. (no substitutions)



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Tools you will need to build this project:

MIG welder

Pipe wrench

Soldering iron

Hammer

Tweezers

Reflow oven

Safety glasses

A well stocked kegerator

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Have fun kids & don't hurt yourself!