Designing your learning platform to allow seamless switching between Manual
Mode and Automated Mode is an exceptionally smart approach. It gives you
immediate "tactile" insight into how thermal inertia, lagging temperatures,
and the Peltier module's hot side respond to a direct turning dial before
turning control over to an algorithmic PID loop.
To achieve this without changing any physical wiring later, you can design the
hardware with a Mode Switch and a Rotary Encoder (Dial) or a potentiometer.
The microcontroller will read your manual inputs and send the exact
corresponding signals to the driver board.

1. Enhanced Hardware Ingredients for Manual Control

To add human-in-the-loop operation, weave these three low-cost modules into
your design:
" 1x I2C 16x2 LCD Display Screen: A simple liquid-crystal readout that
constantly displays the target temperature, the actual temperature from the
probe, and the current operation mode.
" 1x Rotary Encoder (with built-in push button): This acts as your dial.
Turning it adjusts the power manually (in Manual Mode) or sets a target
temperature target (in Auto Mode). Pressing it can switch modes.
" 1x SPDT Toggle Switch: A physical switch connected to a digital pin on the
Arduino to flip between "Manual Power Mode" and "Automatic PID Mode."

2. Upgraded Control Architecture Layout

2. Upgraded Control Architecture Layout
      SPDT TOGGLE SWITCH                         
   [Manual]     :  [Auto]                    
                  ,
                                  <
                                  <
  ROTARY    ARDUINO     IAL $ DS18B20 TEMP PROBE      :
 (Human                             (Chemical Sample)  Input)     
       ,,      
                                     
                                     
         <                                                     <
         <                                                     <
   16x2 LCD                               IBT-2 H-BRIDGE BOARD SCREEN       
 [Displays Live                              [Drives Peltier Unit] Metrics] 
                             

3. How the Twin Modes Operate in Code

By centralizing everything through the microcontroller, you eliminate the risk
of manual user error overriding electrical safety profiles. The software
interprets the position of the toggle switch to execute one of two distinct
logical frameworks:

Mode A: Pure Manual Control (The "Tactile" Sandbox)

" The Dial Action: Turning the rotary encoder dial moves a value from -100%
(Full Cooling) to +100% (Full Heating), with 0% being entirely off.
" The Controller Action: If you set the dial to -50%, the Arduino directly
commands the IBT-2 driver to run a 50% PWM duty cycle on the cooling pin.
" The Learning Visual: You can manually watch the thermometer drop, see how
long the thermal lag takes to reach the chemical sample, and physically feel
how hot the heatsink gets under sustained manual stress.

Mode B: Automated Control (The "Set-and-Forget" Lab Profile)

" The Dial Action: Turning the rotary dial now changes a target value on the
LCD display (e.g., "Set Target: 10B0C").
" The Controller Action: The Arduino takes over completely. It reads the
target, reads the live DS18B20 probe temperature, feeds both into the
mathematical PID loop, and automatically modulates the IBT-2's heating and
cooling lines to lock the system onto your target temperature.

Dual-System Hardware Additions Summary


ComponentRecommended PartPurpose / InteractionApprox Cost (USD)
Visual Output16x2 LCD with I2C BackpackDisplays Active Mode, Live Temp, and
Set/Power Target.$4 - $7
Human InterfaceKY-040 Rotary EncoderTurn left/right to adjust settings; press
down to select.$2 - $4
Mode SelectorSimple SPDT Toggle SwitchHard-switches the Arduino logic between
manual and auto.$1 - $2
Interface Cost Overhead~$7 - $13

Would you like to look at an Arduino code framework that reads the mode
switch, handles the dial inputs for manual power adjustments, and switches to
the automated temperature lock?