Project Proposal – Peltier Table

Description
In the morning, hot coffee or tea can grow cold as you watch the morning news. At a bar, your beer can get warm while you are busy talking to friends. The root of this problem is that drinks are heated or chilled once, and then served to the customer – the drink is at its best as it is served, and reaches room temperature as time goes on. A localized heating and cooling source can be used to solve this problem.

Peltier units are electronic devices which use a substrate to quickly transfer heat from one side of the device to the other. The result is that when a voltage is applied, one side gets very hoot and the other side gets very cold. Flipping the voltage causes the opposite effect (the hot side gets cold, and the cold side gets hot).

By embedding these Peltier units into countertop surfaces such as a coffee table or a bar, this solves the problem by creating a localized heating or cooling source. Adding a pressure switch and a temperature sensor ensures safety and autonomy. If the heating/cooling element can detect when something is on top of it, and also the temperature of that object, it protects the user from false positives and wasting energy.

Physical Device Sketch

Project

Full Assembly


Assembly

Component Assembly

Sensors
K type Thermocouple
One for each assembly. This will be attached to the top of the assembly to determine if the drink placed on it is a hot or cold drink. This way, the controllers knows to either keep the drink hot or keep it cool.

Pressure Switch
A sliding joint with a limit switch and a spring. As weight is applied to the top of the assembly, the spring deflects, causing the plate to slide down. As it does, it trips the limit switch, informing the controller that an object is on the assembly.

Switch
Manual override. Sometimes the user may not want to turn on the effectors, or may want a cold drink to become hot or a hot drink to become cold. This switch will allow for more user control over the effectors.

Effectors
Peltier Units
50x50x4 (mm) max 24V approximately 80 Watt device; currently looking for a model within the $20 price range. There are many different manufactures each with different specifications. More research is necessary to determine future temperature control techniques for specific units. If temperature control is not possible (device is binary – on or off) can PWM work, or are they manufactured for specific set temperatures?

LEDs
Blue and red LEDs indicate when the heat or cold is on in order to inform the user.

Logic

Is Pressure Sensor on?
—->Yes –> Check thermocouple. Hot or cold?
———->Cold –> Make cold, BlueLED on
———->Inconclusive –> Do nothing
———->Hot –> Make hot, RedLED on
—->No –> Do nothing
Is Switch on?
—->Yes –> Check setting
———->Cold –> Make cold, turn BlueLED on
———->Hot –> Make hot, turn RedLED on
—->No –> Do nothing

BOM
• Table: bar or coffee table top, preferably frosted glass or acrylic
• 2 K type thermocouples
• 4 limit switches
• 8 springs
• 8 brackets
• 8 screws
• Wiring, high voltage
• Plug
• 2 External power control circuit
• 2 H-bridge
• Controller
• 2 Red LEDs, 2 Blue LEDs
• 2 – 3 setting switches

Plan
1. Week of the 9th
Create CAD model of full assembly
b. Research Peltier control – determine if units can be temperature controlled or if should buy for spec temps
c. Order all components in assembly
2. Week of the 16th
a. Create initial model – should have temperature control from adruino using external power and H-bridge (produces hot and cold)
3. Week of the 23rd
a. Thanksgiving week – eat turkey
4. Week of the 30th
a. Integrate model into table assembly
b. Limit switches and LEDs embedded onto assembly
c. Full wiring diagram
5. Week of the 7th
a. Fine tune controls issues and interaction
b. User testing
c. Finishing atheistic touches

Assignment 10 results
I ordered 2 Peltier units online. 3 days after ordering, the company called me and told me that they could not complete my order because it was an international shipment. I learned to order early. Will now begin making CAD model to ensure I am buying right components in the right sizes.

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