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author is not affiliated in any waywith either company.)Controller SoftwareThe software was developedto be more flexible than justcontrolling a toaster oven, shouldyou want to apply it to otherthings. The original SparkFunsoftware — which does have manyuseful basic code examples in it —has been heavily modified andexpanded to get the resulting codedescribed here.The 4K memory limit of thePIC makes life really tough forgetting sophisticated with theprogram. Every “extra” feature orline of code was scrutinized. Heavyuse of functions (subroutines) wasrequired to eliminate redundantcode. The fact that only 200memory locations are left out of 4096 is an indicationof how tight it is. The user interface is further hinderedhaving only 2x16 characters on the display and just threecontrol buttons (there is a fourth button for reset only),however, a lot can still be done as seen in Figures 4 and 5.The top line contains the settings for the currentmode of operation and the second line shows thefunctions for the three buttons, marked “up,” “down,” and“select” on the PC board. Each button canhave two functions, depending onwhether a short push or long push(greater than two seconds) has beenmade. The slash mark “/” separatesshort/long functions.A User Manual has been preparedwhich details all the capabilities andoperating procedures. The modes aredescribed briefly as follows:1) Main Menu: This comes up first afterthe splash screen and allows the user toselect one of the five operating modes.This is the basic “home” screen andalways available when exiting one of theother modes. The only way to exit theMain Menu is to turn off the unit!2) Manual: Has a stop watch andrelay control plus displays the currenttemperature. The user can manuallystart/stop/reset the stop watch and turnthe relay on or off directly. This mode isFIGURE 5. Program Mode LCD screen.FIGURE 3. Standardreflow solder profile.“Main Menu” Screen:Current mode:MM = Main Menu“up” button function:x = none“Program” Screen:Step NumberP1 = Program1P2 = Program2“up” button function:R = run (short)S = stop (short)/R = reset timer (long)OvenFlow 1.0useful for calibrating the oven (or making toast).3) Semi-Automatic: The user can set a temperature andthe oven will track this temperature and turn the relayon and off automatically. This can be used for very longoperations, such as chemical bath (e.g., etchant)temperature control for several hours.Mode: ManualMM x x Nx/Sel“down” button function:x = noneTimer Program temperature (C or F)0 000s 000C 000CP1 R/R Jmp Ed/Ex“down” button function:Jmp = jump to next step(short or long)FIGURE 4. Main Menu LCD screen.Top line – Mode Select:ManualSemi-AutoProgram 1Program 2Setup“select” button function:Nx = next mode (short push)/Sel = select this mode(long push)Actual temperature(C or F)“select” button function:Ed = Go to edit mode (short)/Ex = exit back to MainMenu (long)June 2008 69