By Open Green Energy
Featured Published Nov 28th, 2016
Introduction: DIY Portable Mini Refrigerator
By Open Green Energy
I always love to drink chilled Coke. But when I go for a outing, no more any chance to get the chilled Coke.So I seriously wanted to have a portable mini refrigerator, so that I can carry, wherever I go.
I have gone through few videos on YouTube and Instructables to know how to make a Refrigerator. After some research, I made one for myself.The outcome is really awesome.
In this Instructable, I will guide you, how to make a Portable Refrigerator by using the Thermoelectric Cooler Module, Acrylic sheets and Glues.
Voltage – 12V DC
Current – 6 A
Power -72 Watts
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Step 1: Parts and Tools Required
1. Thermoelectric Cooler Module ( Banggood )
2. 4 mm Acrylic Sheets ( Amazon )
3. Arduino Nano ( Amazon )
4. Relay Module ( Amazon )
5. LED ( Amazon )
6. LED Holder ( Amazon )
7. 1K Resistor ( Amazon )
8. Rocker Switch ( eBay )
9.DC Jack ( Amazon )
10. Perforated Board ( Amazon )
11.Hinges ( Amazon )
12. Door Handle
13. Rubber feet ( Amazon )
14. Foam Boards ( Amazon )
15. Super Glue ( Amazon )
16. Glue Sticks ( Amazon )
1. Jigsaw ( Amazon )
2. Dremel Workstation ( Amazon )
3. Dremel Rotary Tool ( Amazon )
4. Soldering Iron ( Amazon )
5.Glue Gun ( Amazon )Add TipAsk QuestionCommentDownload
Step 2: How It Works ?
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The heart of this Refrigerator is a Thermoelectric Cooler Module. Thermoelectric coolers operate by the Peltier effect The device has two ( Hot and Cold ) sides, and when a DC electric current flows through the module, it brings heat from one side to the other, so that one side gets cooler while the other gets hotter. The “hot” side is attached to a heat sink so that it remains at ambient temperature, while the cool side goes below room temperature.
A thermoelectric module consists of an array of p- and n-type semiconductor elements that are heavily doped with electrical carriers.The elements are arranged into array that is electrically connected in series but thermally connected in parallel. This array is then affixed to two ceramic substrates, one on each side of the elements.
To make this Refrigerator, you have two options :
1. Buying the Peltier module,Heat Sink and Fans separately
2. Buying the entire unit which have everything.
After some enquiry, I have settled down to the second option.But if you have some old SMPS fans and CPU
heat sink, then you can choose the first option.
The first and second pictures are downloaded from web for easier understanding.
Credit : http://tetech.com/ and wikipediaAdd TipAsk QuestionCommentDownload
Step 3: Cutting the Acrylic Sheets
First I took the measurement of regular Coke Can,then I finalized the Refrigerator Size.My refrigerator size is
6.5″ x 11″ x 10″ (L x W x H ).So to make a box with this measurement, we need 6 rectangular sheets of following sizes :
1. Base 11″ x 6.5 “
2. Top 11″ x 6.5 “
3. Left Side Wall 11″ x 10″
4. Right Side Wall 11″ x 10″
5. Front Door 6.5″ x 10 “
6. Back 6.5″ x 10″
Note : Actually the front and back cover size is ( 6.5″ – 2 x Acrylic thickness) x 10″
Apart from the above 6 sheets, we need few extra sheets for making different compartments.
I used my Rockwell Blade Runner ( Inverted Jigsaw ) to cut the above size 4mm thick acrylic Sheets.
Safety : Wear Safety Goggles during cutting.Add TipAsk QuestionCommentDownload
Step 4: Cutting the Slot for Peltier Module
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To fix the Thermoelectric cooler module, measure the cold side plastic radiator and mark the outlines on the acrylic sheet.
This sheet size is same as the front and back cover i.e 6.5 ” – ( 2 x thickness of acrylic ) x 10 “.
Drill a hole inside the marked area.
Insert the jigsaw blade and follow the marked lines to cut out the slot.Add TipAsk QuestionCommentDownload
Step 5: Paint the Acrylic Sheets
First, peel up the protective cover from the acrylic.I have transparent acrylic sheets in my stock, but I wanted to make it white.So I spray painted the sheets to make white except the front door and compartments.
This step is optional as the choice of the color is depends on you. If you want to make similar to mine, you can buy the white acrylic sheets.
Safety Warning :
Prefer to paint the sheets outside or in a well ventilated space.Never forget to wear the nose mask.Add TipAsk QuestionCommentDownload
Step 6: Making Holes for Air Flow
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To dissipate the heat from the hot side heat sink of the cooler unit have two 12V fans. As the entire unit will be kept inside the enclosure, we have to make provision for air flow.
Marked the fans size on the two side walls.The outline is square shape,use a drafter compass to make a inscribed circle.Then make holes at all around.
Note : First I tried to make the holes by using my drill with a 8mm bit, but its really difficult and time taking to make bigger holes in acrylic. So I used my Dremel work station to make the holes inside the circle.Add TipAsk QuestionCommentDownload
Step 7: Glue the Cooler Unit
Take the slotted sheet and glue the Cooler plastic radiator.
Apply sufficient glue all around to make perfect sealing.This is really important, otherwise the hot air ingress through the side joints.Add TipAsk QuestionCommentDownload
Step 8: Mounting the Separator
Keep any of the side wall on the table as shown in the picture.
Then place the cooling unit, measure its entire length. Mark a line for separation between hot and cold side.
Apply hot glue along the line and place the separator sheet.
To hold the sheet perpendicular,take support of a solid rectangular object.I used a 12V lead acid battery.Add TipAsk QuestionCommentDownload
Step 9: Join the Two Side Walls
Now place the base sheet and glue the earlier made structure.
Then glue the another side wall to the separator plate.
For clear understanding, see the above picture.Add TipAsk QuestionCommentDownload
Step 10: Add Supports to the Cooling Module
The heatsink along with the two fans are really heavy.As the entire unit is glued to the surface, there is chance of breaking of the bonding.So we need some support structures to hold the entire unit.
Cut small size foam or thermocol sheet to make the support.
Then insert it just below the two fans.Add TipAsk QuestionCommentDownload
Step 11: Prepare the Back Panel
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In the back panel we have to install the DC input Jack, one switch and a LED for indication.
To fix the LED nicely, you can use a LED holder as I have used.
Measure the sizes of the parts and make slots for them.I used drill for making circular slot and jigsaw for rectangular slot.Insert the components and glue them with the acrylic sheet.
1. Solder two wires to the DC jack, red to the positive and black to the negative terminal.
2. Solder a 1K resistor to the long leg of the LED ( + ) then solder a red wire to the other end of the resistor.Solder a black wire to the short leg of the LED (- ). Use heat shrink tube to avoid shorting between the wires.
3. Cut two long wires (red and black ) for power supply to peltier module.
4. Then follow the picture to make the circuit.Add TipAsk QuestionCommentDownload
Step 12: Making Arrangement for Sliding Tray
My idea is to make two cold compartments in my refrigerator, one for coke cans and other for chocolates.But I make the compartment in such a way that in the top compartment, I can keep chocolates or one can in horizontal position.
The lower compartment height is slightly higher than the regular coke can height ( 5.3 “) .
To make a sliding tray arrangement as in your home refrigerator,you need some supports to hold the tray.
Follow the steps below :
1. Cut small strips of acrylic as shown in figure. I have used the excess sheet left out during the earlier steps.
2. Glue two strips to make it thicker.If you have thicker sheet, then no need to do it.
3. Then glue the strips to the side wall.
4. Leave some space ( tray thickness + some margin ) and glue similar strip to the wall.
5. Repeat the same process for another side wall.
6. Insert the tray ( 3mm sheets ). The size is depends on your compartment size.
Note : Make sure both side strips are at equal height from the base, otherwise your tray will not stay horizontal.Add TipAsk QuestionCommentDownload
Step 13: Make Compartment for Electronics Circuits
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I have divided the hot side compartment in to two parts.In the lower part, the heat sink and fans are there, and in top part electronics circuit for controlling the refrigerator temperature.
Follow the same procedure as for the cold side compartment.Add TipAsk QuestionCommentDownload
Step 14: Insulate the Interior
To improve the cooling effect, we have to insulate the cold chamber properly. I used 5mm foam board for insulation.
1. Measure the sizes of the all the wall of the cold compartment.Then cut the desired sizes foam board.
2. Use hot glue to stick to the acrylic surface.
3. Apply hot glue sufficiently at the all joints for perfect sealing.Add TipAsk QuestionCommentDownload
Step 15: Making the Front the Door
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I wanted to make the front door transparent, so that I can see the inside.But remember if you will insulate the door also, the cooling will be more effective.
Mark 1cm side border on the front door acrylic protective cover.Then peel up the protective paper.
Paint on the border area.Leave it a hour to dry it out.
Peel up the unpainted portion protective cover.
Mount the hinge and handle by using Super Glue . I have used Gorilla Super Glue.Add TipAsk QuestionCommentDownload
Step 16: Front Door Sealing
Cut few of the 1.5cm wide foam board sheets.
Glue the foam board strips to the door border area ( painted portion )
Then close the door and check for proper fitting and sealing.Add TipAsk QuestionCommentDownload
Step 17: Controlling the Temperature
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To control the temperature, I will use an Arduino to measure the temperature of the cold compartment with the help of a DS18B20 waterproof temperature sensor.If the temperature falls below 3 degC, a relay will cut out the supply to the cooler unit and when the temperature reaches 7 degC, again the cooler unit will be switched ON.This will maintain the refrigerator temperature as well as save a lot of power.Place the Arduino and other circuit on the hot side top compartment.I used a mini bread for easy connection.To connect the temperature sensor to the bread board,solder 3 male headers pin. For better understanding, refer the above picture. To insulate the joint, apply some electrical tape.
Then glue the top cover.
Arduino Code is attached below.
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Step 18: Attach the Rubber Feet
As the acrylic sheets are slippery, I attached 4 anti skid rubber feet at the base.
Now the fridge sits firmly on any surface.Add TipAsk QuestionCommentDownload
Step 19: Enjoy the Chilled Cokes
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Now it is time to powering up the refrigerator.
Connect the refrigerator to a 12V, 10A or more power supply.Then switched it ON, the LED should be lit up and you will hear the fan sound.Leave it for 10 to 15 mins.Now the cokes and chocolates are really chilled.