The Crumbination Lock ™: No Toast, No Crust

Meet The The Crumbination Lock ™, the most secure kitchen appliance ever made. This toaster refuses to work unless you input the correct lock combination. Guess wrong, and your bread will be rudely ejected without even toasting. Using Arduino, sensors, and some mischievous programming, we’ve transformed an ordinary toaster into a needlessly complicated breakfast challenge. Want toast? You’ll have to crack the code first.

This Instructables guide covers how we took apart a commercial toaster, added additional components, and coded it to behave in an uncanny, mischievous manner.

Video

Function / How it works

1. Plug in the power cord to turn on the toaster
2. Put in your bread
3. Press the defrost button to get a hint for our top secret combination (3 clicks counter clockwise, 3 clicks clockwise, 5 clicks counter clockwise)
4. Rotate the dial in the order of the combination and push down the lever (The bagel LED will flash for every counter clockwise click and the cancel LED will flash for every clockwise click.)
5. Once the above conditions are met, the toaster will begin toasting like a regular toaster.

If the conditions are not met (the combination is not entered or incorrect),

1. The toast will remain in the toaster for 5 seconds before all the button LEDs light up red for 5 seconds and the toaster will eject the toast.

How This Is Achieved:

1. Plug in the toaster through AC power, and the electromagnet will turn on
2. Once lever is pushed down, electromagnet will hold lever down to push switch button allowing for heating to begin if the conditions for te rotary encoder are met
3. If rotary encoder is turned an overall of 5 counter clockwise clicks, the heating element will be turned on
4. If the above condition is not met, the heating element will not turn on
5. After 5 seconds of delay, all LEDs will flash red for 5 seconds
6. The relay to the electromagnet will open, releasing the spring causing the toast to shoot out
7. After the toast pops out, The Crumbination Lock ™ is reset to its original state

Materials:

Toaster Model: MASTER CHEF Stainless Steel Toaster with 3 Settings, 2-Slice Capacity

Dimensions: 0.48 x 10 ⅜ x 6.81 in

Wattage: 900 W

Existing Parts Inside the Toaster:

1. Nichrome wire (heating element)
2. Sliding assembly (spring mechanism & lifting lever)
3. Spring
4. Electromagnet (actuator)
5. Outer casing
6. Bread slots & guides
7. Crumb tray
8. Control PCB
9. Potentiometer
10. Buttons x3 (Bagel, defrost, and cancel)
11. LEDs

Additional Parts:

1. Rotary encoder
2. Relays x3
3. Electromagnet
4. Perf board
5. Arduino nano
6. Boost convertor (5v to 12v for electromagnet)
7. 5v power supply (120v to 5v)
8. 1k resistors x3
9. 220 ohm resistors x3
10. LED x3
11. Limit switch

Tools:

1. 3D printer
2. Gloves and safety glasses
3. Screwdriver
4. Soldering devices
5. Pliers
6. Wire cutters
7. Multimeter
8. Waterjet
9. Angle Grinder

1. A Milwaukee screwdriver was used to release the security screws and release the outer shell from the base.
2. Two clips at the bottom of the control board were released, seperating the control board from the electro magnet and relay.
3. All electronic components using side cutters, leaving in only the nichrome heating elements and their respective wires.

How the Original Toaster Functions:

1. Plugging in the toaster supplies power to the circuit.

2. Twist knob/potentiometer to set the timer for your toaster. This changes the resistance on the potentiometer to determine the rate of energy filling the capacitor.

3. Pushing the lever down closes the circuit, activating the electromagnet, nichrome wires (heating element), and the timer system.

4. Energy flows to the capacitor through the variable resistor, with its resistance determined by the potentiometer.

5. Once the capacitor is full, the microcontroller deactivates the electromagnet cutting power to the circuit and popping the toast.

Bagel button:

1. Turn on the LED next to the button.

2. Changes the state of the relay to turn off the inner nichrome wires (when pressed only the outer panels will heat up, toasting only the inside of the bagel).

Defrost button:

1. Turns on the LED next to the button.

2. Adds a set amount of time to the microcontroller, extending the heating time.

3. After the extended time is up, the capacitor timer system runs as it usually would.

Cancel button:

1. Bypasses the resistor and fills up capacitor immediately, deactivating the electromagnet.

2. The lever is released, turning the heating element off.

The circuit was built on a breadboard to allow fast prototyping throught our iteration proccess. There are three corresponding LEDs for each button input; one for bagel, one for defrost and one for cancel. While testing we used three Arduino buttons on the breadboard to mirror the toaster buttons. The buttons are pulled low and connected to the arduino pins D2, D4 and D7 with the coresponding LEDs connected to D9, D10, D11.

Two extra LEDs were added as indicators to simulate the electromagnet and heating relays on the toaster.

Wrote a code to function as intended:

The code first sets a correct combination in an array to crack open the locker toaster (3 CW, 3CCW, 5CW). Then, it sets the total of these values as the correct rotary encoder read to open the heating element (3 + (-3) + 5 = 5). The defrost button is coded as a hint button, to read the absolute values of the array and flash the bagel and cancel LEDs to hint at how many times to turn CW and CCW. A popToast function turns on all the LEDs for 5 seconds, before turning off the electromagnet and releasing the lever and mechanism, popping the toast. This function is called whenever a button other than defrost is pressed, or when the lever is pressed following an incorrect encoder dial. The cookToast function flashes the LEDs rapidly to show excitement following a correct combination, and turns on the heating element for the set cooking time (60 seconds) before popping the toast.

Tested the code on a breadboard before transferring it to the toaster.

A stronger spring and electromagnet were added to enable the toaster to launch toast into the air. The original carriage bracket was not strong enough for this change so it was replaced with a custom fabricated 2mm steel plate. The steel plate was cut using a waterjet and bent into place using a break.

The base of the toaster was designed and 3d printed in ABS to fit our electronics and provide adequate mounting points for the toaster components.

The buttons and leds were soldered onto a prototyping board which was sized to fit in the original PCBs location. The rest of the support electronics were mounted in the base of the toaster.

The Nichrome wires were toned for contenuity and resistance. Once the two loops of coils were identified they were tested, connecting 125v AC for one minute intervals while monitoring current and voltage.

After the tests were complete the wires were marked and connected to the high voltage relays.

All tests were completed in an open area with the propper PPE.

The toaster assembly was completed by attaching the 3D-printed base and outer stainless steel case to the toaster using the original security screws. With everything now assembled, the Crumbination Lock™ is ready to use. Get ready to prank everyone with flying toast!

The new spring worked seamlessly with the electromagnet, allowing the toast to pop out perfectly. However, we encountered an issue with the original stainless steel outer shell, which required us to 3D print a new handle component to pull down on the spring. This modification caused the handle to press inward and misaligned with the electromagnet. Throughout this process, we learned the inner workings of this everyday household item and explored ways to repurpose its existing elements to serve our own purpose, incorporating features such as the hint mechanism and combination lock.