Have a spare USB Flash Drive laying around? Turn them into a OTG-USB Drive so you can connect it to your smartphone or tablet without having to carry around a USB-OTG adapter. There are few products on the market designed for that, but I would like to make my own, since it is easy and I have all of the required parts.

I was cleaning my stuff and it turned out I do have a few USB-OTG adapter laying around. I bought them as a backup, and as you may know, today USB-Type C is the future. That means, I have absolutely no purpose keeping that much around. Not to mention my old USB 2.0 flash drive, which is kinda obsolete. So here it is, I'm gonna show you how you can turn your regular USB 2.0 flash drive into a USB-OTG drive for about a dollar.

Disclaimer: The risks associated with this project are damaged flash drives, smartphones and tablet. You have to exercise caution when splicing and soldering wires around, not to mention keep your $500 smartphones away for first time testing. You have been warned!

Next, these are the things you need:

- A regular USB 2.0 Flash Drive with soldered connector (FREE)

- An USB-OTG Adapter (should cost less than $1)

- Multimeter with continuity-test feature

- Soldering Iron with solder

- Basic soldering & multimeter skills

- Knife (to pry open USB Drive)

- Silicone Sealant, Sugru, hot glue or some sort of insulative adhesive

- Wire cutter or scissors

- Electric drill or dremel with 2mm bit

- (Optional) Male USB connector type-A to check for pinout

Step 1: Select Your USB Flash Drive

First thing you need to do is to select a USB Flash Drive with a soldered connector. Not all USB Drive are equal, and the only way to know it is to pry open the drive. Use a knife or screwdriver to dismantle the drive.

[Pic 2-5]

This is a China-made USB 2.0 Flash Drive with stainless case. Unfortunately this is an small ultra-thin flash drive stuffed in a plastic dummy. No USB connector is present.

[Pic 6-8]

This is another China flash drive. Except it actually has a board with a connector. I'm going to use this drive. Please note that the "messy" solder in the connector is due to the fact I have soldered this USB Drive before.

Step 2: Cut the USB-OTG Adapter

[Pic 1-2]

There are various types of USB-OTG on the market, and for this model, I can pull the plastic frame around the female USB port to show you what is actually inside.

[Pic 3-5]

Try to measure the length of the cable required for your USB drive. Do not cut the cable too near to either end, because we're going to need both. The yellow flash drive is an example of a common flash drive (Kingston)

[Pic 6-9]

Use a wire-cutter to strip each wires until all 4 colors are present. You can continue stripping the wires until each wires are free to move around inside the flash drive body. This is to make sure the wire can fit inside the flash drive when it is closed.

Step 3: Check Your OTG Pinout

Now a USB-OTG Adapter uses 4 wires. Two are for power, and two are for data. You need to make sure you do not solder the wrong wire or you can end up damaging your $500 smartphone for a $2 project.

Using a multimeter and the female USB connector you just cut, you can determine the pinout of your OTG cable. Typically the colors are: Red, White, Green, Black. But it may not always come in that order, or maybe it will have 4 different colors altogether. Please note the pinout diagram above, if you're measuring the female connector that means the order of colors are reversed!

[Pic 4-5]

I used a male USB connector to make checking easier. It should also cost less than $1 if you shop online.

[Pic 6-7]

This is what my multimeter shows when it is in the continuity-test mode. Take note of the correct orientation of the wire vs connector. Double check the order and refer to the USB pinout guide when in doubt.

Step 4: Soldering

Now it is time to solder the wire. Prepare your soldering iron and solder.

"Tin the tip" of the solder and start tinning the 4 wires.

ALWAYS DOUBLE CHECK TO ENSURE THERE ARE NO SHORT-CIRCUIT at any of wires you just soldered. Also ensure no wire is too close to each other. I cannot emphasize enough at this point, that you should have soldered the correct order of the pinout. If you feel you made a mistake, it may be wise to stop the project and discard the old flash drive rather than damage your smartphone or tablet.

Step 5: Prep the USB Flash Drive Body

[Pic 1-3]

This is an easy step. First you just have to drill the plastic body of your USB Flash Drive. This is to make sure the cable from the OTG can exit through the back of the flash drive. I used a 2mm drill bit, but I think 3mm should do a better job for my cable.

[Pic 4-6]

The next step is to make sure the flash drive does not move around. The second you pry the USB drive open there is a chance it won't be as tight the next time you put it back. So I decided to use a double-tape to keep the flash drive from wiggling. You can use blu-tack, sugru, hot glue or other stuffs.

I did put some silicone sealant to the USB connector so I don't have to worry if any of the wires move around and touching each other causing short-circuit. While this is optional, I highly recommend it. I'm not sure if Sugru and Blutack are insulative material, but when in doubt the silicon sealant and hot-glue work well.

Step 6: Here You Go!

After all those work, it's time to put your USB OTG drive into a computer. The reason I chose computer first is because most computer's motherboard have a short-circuit protection.

I tried it on my tablet first (pardon the broken screen) through both its USB and OTG port. It worked perfectly as intended, and then I proceed to try it on my smartphone (LG G4) which runs on Android. It is recognized by the File Manager. I should remind you that most Android do not support NTFS file format, so you are better off formatting your USB Drive as FAT32.

Voila! The DIY OTG-USB Drive works! Now you can have your own OTG-USB Drive without breaking the bank.

but now I must warn you that because this is a simple "parallel" wiring, YOU SHOULD NEVER ATTEMPT TO CONNECT BOTH ENDS [PIC 7]. I am not responsible for any damage you cause to your equipment if you decided to be curious.

[Pic 8-10]

Okay now that you have known how to make your own OTG-USB Drive. Here are pictures of my DIY OTG HUB. It's essentially made using the same dismantle-and-solder method. It even uses the same OTG cable from the OTG Adapter. What's best is that I have been using this hub for more than a year with no problem and no damage.

Good luck!