Coconut Flesh Grater (Portable & Speed Adjustable)

With some plywood scraps and some other additional salvaged parts, I came up with the idea to make my very own small portable tool that grates fresh coconut flesh from a de-husked, halved coconut. There are many manual graters available on amazon and other stores, but small, portable electric graters are not so common.  

Why buy from the store when you can actually make a custom one for yourself? You have the option to make them from recycled parts, adding a speed control, and safety switch, and best of all you'll see how this works together to actually make a working grater and can even be applied for a different project that involves rotating tools/equipment.

First I came up with an option to use a small DC motor which makes it easier and safer to build one, but then it comes with one problem; it is not reliable and the grater needs to be quite heavy so that it can stay and hold stable on a flat surface which a small DC motor can't. A single-phase induction motor is long-lasting, it's heavy, and suitable for this purpose.

Reducing waste is my goal, so combining recycled parts and a few other purchased, but affordable items, I made one in a small form factor that is very stable on a flat surface, easy to carry around, and comes with an adjustable speed and safety switch. 

Disclaimer:

This project involves working with live electricity and high-speed rotating parts. Never attempt to try this on your own if you are unsure and don't know what you are doing. Make sure all electrical tools and appliances that you use have safe grounding. Always take precautions and use appropriate safety gear while handling any tools, chemical powder/liquids. Learn how to use a tool, or chemical powder/liquid before using them. If there is a datasheet for certain chemicals, and you are unsure about it, read them first before handling them. Create a safe work area before you start any project.

I use scrap B-grade Plywood with 1.5cm thickness to build the casing for the coconut flesh grater and cut them into different parts as below. Supports using softwood. All dimension is in cm;

Casing:

i) Base panel - 20 X 15 X 1.8 

ii) Back cover - 20 x 17 x 1.8

**made an 0.8cm hole at the bottom corner for the power supply cable

ii) Side Cover (Right/left) - 15 x 17 x 1.8

**made a 2.5 cm hole using a hole saw for the speed controller knob and a 2.3 x 3 cm square hole for the main on/off switch. This is made on the right cover 

Softwood for the support:

i) Side Cover support (2 pieces) - 10 cm long (2.1 x 2.1 x 2.1 on all sides)

ii) Back Cover Support (2 pieces) - 5 cm long (2.1 x 2.1 x 2.1 on all sides)

iii) Centre Support for AC Induction Motor - 16 x 2.2 x 3.5

iv) Lift handle support - 23 x 2.2 x 3.5 

v) Top motor support - 9 x 4.5 x 1.2

vi) Capacitor support - 7 x 7 x 1.2

vii) Emergency Stop Switch Support - 7 x 7

Electrical/Electronic Components:

Some salvaged parts and the rest is purchased at a very affordable price from the online shop (Aliexpress). 

i) Single Phase AC Induction Motor (4-Pole, 220V 50Hz, 1380r/min) - Taken from an old washing machine

**I have got mine salvaged from an old washing machine along with a 5uF start/run capacitor with a 400VAC Rating. You can get any single-phase AC induction motor from other equipment. Some motors have rating/wiring tags attached to them. If you are able to get the motor but not the capacitor then make sure to get the right capacitor matching the motor rating. Read further.

ii) Start/Run Capacitor (5uF/450VAC) - Taken from old washing machine

** If you salvage the AC motor from an old washing machine or other single-phase AC, make sure the type of motor you are using; some motors have two capacitors - start capacitor and run capacitor and some motor use only a single capacitor which works as both start/run capacitor. Either way, you need them for the project, or else it won't start. Here's the formula to calculate before you buy one;

C = P x n x 1000 / V2 x 50

Where; 

P = Power rating of the AC Induction motor 

n = Efficiency of the motor; check the rating on the motor; if there is none you can set it as 90%

V = Supply voltage to motor (Volts); in my case, I'm using 220 V as the input voltage

C = The capacitance value that is suitable for the AC motor that you are going to use

My input voltage is 220 V so I'm using a 5uF 400VAC Rated Capacitor. You can buy one from Aliexpress.

iii) 220V/240V AC Voltage Regulator

 **This can be bought at Aliexpress they are pretty cheap and works well. With this, you can adjust the speed of the motor. 

Link: AC 220V 2000W SCR Voltage Regulator Dimming Dimmers Motor Speed Controller Thermostat Electronic Voltage Regulator Module|Motor Controller| - AliExpress

iv) Emergency Stop Switch - Optional

** This is optional, not necessary but I just put it in for testing purposes. Can be bought from Aliexpress.

Link: Red Mushroom Cap 1no 1nc Dpst Emergency Stop Push Button Switch Ac 660v 10a Switch Equipment Lift Elevator Latching Self Lock - Switches - AliExpress

v) 220/240V AC Power Plug (G-Type/UK Plug) with 0.5-1.0 meter long cable 

**Need this to juice the grater machine and make it run!

vi) KCD4 DPST Rocker Switch (16A 250VAC / 20A 125VAC)

** See if you could salvage one from other tools or equipment. Or can be bought from Aliexpress. KCD4 is a dual pole rocker switch with a built-in indicator light that I use to turn on/off the grater. 

Link: Kcd4 Rocker Switch Power Switch 2 Position/ 3 Position 6 Pins Electrical Equipment With Light Switch 16a 250vac/ 20a 125vac 1pcs - Switches - AliExpress

Grater casing & assembly:

i) Grater head + 3d printed insert

** This also can be bought from an online store, you may find alternative grater head as spare parts from other vendors selling this part separately. For my case, I had to 3d print an insert for the grater head, as the motor shaft that fits the grater head is loose when fixed.

ii) Grater casing 

** I found this small blue plastic pan that is just nice to fit with this motor. You may use others with a similar shape or custom 3d print one with a similar size.

Other parts:

• 2-core electrical cables (preferred length based on your materials)
• Terminal lug & connectors - **optional (appropriate size to connect the capacitor or switch), alternatively may solder them permanently on the terminal as you wish.
• Philips screws/JCBs (appropriate length & sizes) - to assemble the casing
• Base support - 4 pieces - **optional (can be bought from Aliexpress) - Link: 1/2/4Pcs Anti Vibration Feet Pads Rubber Legs Slipstop Silent Skid Raiser Mat Washing Machine Support Dampers Stand Furniture| | - AliExpress

Tools:

• Measuring Tape
• Square Ruler
• Digital Caliper
• Wood Clamp
• Hand Drill + Drill Bit (M6) + Hole saw Bits
• Screwdriver
• Safety Gloves/Glasses/Mask
• Wood Glue (TimberBond 756)

First, prepare all the plywood panel that has been cut in specific dimension from the supplies list. To assemble the casing, I used Timberbond 756 glue to hold each piece (side and back cover) in place.

Starting from the right panel, apply the glue on the support and attach the panel. Do the same for the back panel with the supports but leave the left cover open. Using the appropriate screw size and length screw the panel with support inside. Attach the center support for the induction motor so that it will be easier to place the induction motor later on and screw them in place.

The casing is halfway done for now but will continue after wiring and installing the electronic/electrical components inside the casing

For all the components used in this project, I have divided the wiring into different sections.

Section A : from the power source to the main switch (KCD4) & Emergency switch

Section B : wiring for the Emergency switch

Section C : wiring for AC Voltage Regulator

Section D : wiring for the Capacitor with Induction Motor

Included simple schematics for KCD4 wiring & induction motor/capacitor connection

For this section, first I connected the single-phase power supply with live (L) and the neutral wire (N) to the KCD4 switch. When connecting to the KCD4 terminal refer to the schematic. KCD4 needs to be connected to the correct terminal with the live and neutral wire so that the built-in light works when turned on. You can either use a terminal lug connector or solder them permanently on the terminal.

The output terminal from the KCD4, the L (out) connected to the emergency switch (on the normally closed terminals), and the N(out) connected to the voltage regulator.

This is for the emergency switch meant as a safety feature for the grater.

The wiring for this component is pretty straightforward, connect the L (out) from KCD4 to the terminal on the closed contact side. This switch can act both as a NO/NC switch, so I'll be wiring it on the NC side (normally closed) so that pressing the button will break the circuit at once.

Using the 220/240V AC Voltage Regulator that I bought online, I'll be able to adjust the rotating speed of the grater while it's running.

All single-phase AC induction motors have some sort of capacitor, built-in or separately connected to the motor. I took mine with a separate capacitor from the old washing machine. If you have a single-phase AC induction motor but not the capacitor, then look at the motor tag to check what rated capacitor to use. Or you can calculate using the formula; C = P x n x 1000 / V2 x 50 (see in the 'Supplies' section).

Also, check if there is a diagram of the wiring. It will be useful and easier to identify the common wire for the induction motor.

A single-phase induction motor, can't start on its own because a single-phase can't generate a rotating magnetic field for the winding on all poles. So by introducing the capacitor to the auxiliary winding at a different angle, it creates a two-phase that introduces the needed torque and magnetic field to run the motor.

In simple terms, the capacitor creates a lag or delay phase for the auxiliary winding to be energized only after the main winding is energized which provides a phased 90-degree rotating magnetic field and torque to start and continue to run.

The L (out) from the voltage regulator will be connected to one side of the capacitor terminal to either on the start or run winding. This will determine the direction of the motor rotation - clockwise / anti-clockwise.

Check the schematic on the next step for details on how this works in a single-phase induction motor.

The schematics are drawn using the free circuit simulator applet online. You can draw and simulate your own schematics for other projects. Here's the link;

https://www.falstad.com/circuit/ 

Simply changing the main supply current; the L (out) from the Voltage regulator) to the either main or auxiliary winding - purple or red wire), the single-phase induction motor can be set to rotate clockwise or anti-clockwise.

The next step is to wire/assemble this on the casing and will continue building the casing with other parts.

Placing the induction motor on the plywood base, I screw them with support attached to the back cover (16 x 2.2 x 3.5). You may use a different way to do this, but I find this is the best fit and most stable position while placing and securing the induction motor on the plywood base. You can install the left cover once you install the main switch and voltage regulator (speed controller). Note the 0.8 cm hole on the back cover for the 220/240V power supply cable.

The KCD4 switch and the voltage regulator knob slotted thru the hole made earlier on the side cover. At this point, I installed the left side cover and continue to install other components.

The support (7 x 7 x 1.2) and installing the emergency stop switch on the top right of the casing

The support (7 x 7) and the capacitor installation on the top left of the casing

Made a 3d-printed insert with a 1cm diameter in order to securely fit the motor's shaft to the grater head.

And finally, installing the front grater cover, grater head to the motor shaft, and the lifting handle support - 23 x 2.2 x 3.5 on top of the casing. For safety, earth grounding for the induction motor. Use the earth-ground wire from the power cable and terminate it at the induction motor's metal enclosure.

To test, I switched on the motor, it runs without heavy vibration and the speed controller works at various speeds. I did not install the additional base support as the entire assembly is very stable and sturdy.

That's all for a simple but powerful coconut flesh grater made out of scrap plywood, some salvaged parts, and a few cheap accessories as add-ons!