With summers coming on its peak and increasing temperatures I am thinking about ideas to blow up all the heat away.....
So, In this instructable I am going to built a Cordless Table Fan to cool things up. To make this project productive, approachable and the final product as reliable as possible I have decided to built this Table Fan, a useful summer gadget by using commonly available materials.
The task here is to built a cost effective and reliable table fan that offers cordless operation and is rechargeable so that we can use it over and over again without any worries about handling the power cord or putting in new batteries each time.
With these initiatives in mind, its time to get our hands on the tools and required stuff for this project.
Lets get building....
Step 1: Tools and Materials
The tools that you are going to require for this project are:
- Hand saw
- Hand drill
- Drill bits
- Super glue
- Screw driver
- Soldering iron and wire
Its not necessary to have all the tools mentioned above, the task in any DIY project is to get the job done and not to own particular tools and thats where your creativity and style rolls in....
As far as the material is concerned the list follows:
- 12v 7watts Computer cooling fans (Preferably four identical units) "Can be easily found from computer scrap"
- Old laptop batteries
- 3mm thick MDF sheet (approx 2 square feet)
- 2 inch long nut bolts
- On/off switch
- 5mm charging jack
- Printed circuit board for PWM controller
- Electronics components (Detailed list in the PWM Speed control step)
- Rubber O-rings
- wooden screws
Step 2: Making the Base
To start with I have made the base of the fan using 3 mm thick MDF sheet. To make the fan stable I have to keep the centre of gravity as lower as possible. So I am going to enclose the battery pack inside the base to make the design as stable as possible and prevents it from flipping over while the fans are running at maximum speed.
All the body parts are made out of 3mm MDF sheet using a table saw as shown in the pictures above. The dimension and the number of pieces are as follows:
- 50mm*280mm Base plates (2 Pcs)
- 15mm*280mm Side plates (2 Pcs)
- 15mm*44mm Side plates (2 Pcs)
- 38mm*240mm. Side Plates (2 Pcs)
- 38mm*60mm Top plates (2 Pcs)
- 60mm*240mm Front/Rear Plates (2 Pcs)
Later I have started gluing all the pieces for the base using super glue. Since MDF sheet seems to absorbs a lot so using super glue to make joints between MDF sheets can produce some outstanding joints. I have also added small MDF blocks to each corner of the base enclosure which will later help me screw the bottom plate.
Step 3: Battery Pack
To power this Table fan I have used lithium polymer/ion cells that I have reclaimed from a couple of old laptop batteries. Usually old laptop batteries contain multiple lithium polymer cells and when a battery goes bad , usually its because of one or two cells dying causing unbalanced voltages amount the whole battery pack and thus discarded.
Hopefully I have disassembled a couple of laptop batteries that I have got from an old computer scrap dealer in my area. Those batteries costs me almost free and all I have to do is to look for the cells inside the battery that are standing above 3v. Usually the cells that have a voltage of above 3v or higher seems to hold a good capacity.
Once I have got those cells, I assured their capacity using a lithium polymer balance charger, charging each cell individually.
Later I have made two 12v battery packs by soldering three cells in series for each pack. Thus each pack have a capacity of 2200 mAh at 12v. Later I have connected both battery packs in parallel to double up the capacity which in turns increases the run time as well. Both the battery packs seems to fit perfectly inside the base enclosure. To prevent the battery pack fro moving here and there I have glued them using hot glue.
Step 4: Switch and Charging Jack
To operate the fans I have added a simple switch in series with the battery packs. Connecting the positive terminals of the battery packs to one end of the switch while the other end goes to the PWM speed controller. I have made a hatch by drilling a couple of holes and then making it up to the size of the switch using a file.
To recharge the battery packs, a 5mm charging jack is connected in parallel to both the battery packs. Latter I have drilled a 13mm hole in the base opposite to the switch so that the charging jack push fits inside the base.
The output wire then goes through a hole in the middle of the upper plate to the speed controller unit.
Step 5: Base Plate
The base plate is mounted in place using four wooden screws at each corner. Then I have glued rubber O-Rings around each screw using super glue. These O rings helps the base to resist skidding here and there while the fans are running.
Step 6: Making the Top Compartment
To make the upper compartment I have cut down the front and rear plates sections that are getting in front of the fans using a jig saw. This allows a smooth airflow and also give the whole structure an elegant look.
All the pieces are then glued using super glue and then the upper compartment is glued to the top of the Base, exactly in the middle os the base.
This compartment will serve as the space for mounting the Pulse width modulation speed controller in order to control the speed of fans.
Step 7: Mounting the Fans
The fans are placed on to the base with all the wires going inside the middle compartment. Make sure all the fans are facing in the right direction. I have also glued some wooden blocks at both corners on the base which will provide an additional support for mounting the fans.
After placing all the fans in their respective places I have connected all of them in parallel. This allows me to control all the fans using only one input and thus operating them at 12v.
Step 8: PWM Speed Controller
In order to control the speed of fans I have made a Pulse width modulation speed controller. As the name say, the amount of electrical energy that is being delivered to the fans is controlled by frequently switching the output current through a MOSFET. To achieve variable speed the width of the output pulse can be changed using a 555 timer IC producing the variation in the width of output pulse according to a 100k potentiometer.
Instead of implementing the circuit on a perfboard I have designed a schematic and then converted it to the PCB.
Later I have ordered my PCBs from JLCPCB. For the first order we can get as low as 2$ for 10 PCBs and that includes the shipment cost right at my door step.
Using PCBs for the speed controller gives that thing a neat look and also a flawless performance as the quality of the PCBs is just outstanding.
The list of components is:
- NE555 timer IC
- 100K Potentiometer
- Potentiometer knob
- IRFZ44 MOSFET
- Aluminium heat sink
- PCB connectors
- 1k resistors
- 1n4007 diodes
The schematic and the Gerber files for the PWM Speed controller are attached in this step.
Step 9: Connecting the Speed Controller
The fans are connected to the PWM speed controller at the output port and the battery wires coming from the base are connected to the input of the speed controller.
To mount the speed controller unit I have drilled a hole across the top compartment such that the potentiometer shaft goes through the front plate. The knob is mounted on to the potentiometer shaft, allowing us to control the speed of fans easily.
Step 10: Mounting the Fans
All the fans are mounted using 2 inch long nuts bolts which seems to fit perfectly. I have also made coupling for the corners of the fans at the outer side which seems to provide good strength to the whole structure.
With that being done the fan is ready to propel some cool breezes across the room.
Step 11: Final Results
As I finished this project, It was worth having a cool breeze in front of this sleek Cordless Table Fan thats built completely out of scrap. On a full charge, the fan seems to provide a run time of 2 to 3 hours depending upon the speed of the fan.
The authentic contrast of MDF sheet along with matt black PC fans gives the whole thing an elegant look. The overall unit feels solid built and I hope it will last longer.
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