DIY Wireless Charger + NFC Dock for Your Car




About: The team behind Sugru, the mouldable glue that makes fixing and making easy and fun. Do-ers of the world it's time to get excited.

It's pretty amazing how much easier it is to use our smartphones as GPS these days! But anyone who does this regularly will know it really drains your battery, so you always need to keep it on charge when you're driving.

This project will show you how to turn any in-car phone holder into a DIY wireless charger and NFC dock! It means all you need to do is clip your phone in place and you're good to go... super simple! No plugging and unplugging your charger cables each time. Plus combining using NFC tags means your phone will load up the app you want on demand — we used maps for this, but a driving playlist might come in handy :)

This idea started a couple of weeks ago when Juan and Tom on the sugru team were talking about where it would be handy to have wireless charging for their phones. They decided building it into a car would be awesome, so they challenged Jude (remember the Oyster card hack?!) to make a DIY in-car charging system.

Here's what Jude dreamt up...

Step 1: Get Your Kit Ready

For this project you'll need:

car phone holder and USB cable and power/cigarette port (or USB to USB if your car has one of those)

— an NFC tag (self adhesive)

Wireless charger loop and PCB (Combined)

— pack of sugru (black)

— your cell phone (we've used a Nexus 4)

— scalpel

— soldering iron

— coffee stirrer - *cough* liberated from a corporate coffee bar

— also you'll need some paper, a pen, some sticky tape and some tissue paper

Step 2: Modify the Wireless Charger Loop

Reason we did this is so that your phone sits flush on the induction loop.

— unsolder the connection to the PCB

— thread the wire through the hole in the centre

— and re-solder back in position


Step 3: Find the Range of Your Wireless Charger

This seemed like an easy way to find the tolerance of the wireless charger in relation to your phone.

— Tape up the now re-soldered wireless loop to a piece of paper

— Plug it in

— Slide your phone up, down, left and right over the wireless loop to find the tolerance of your phone's charging radius. (Sadly up, up down, down, left, right, left, right won't unlock a cheat here)

— Mark the edges and mark the limits

— Using your sketch to position the wireless loop onto your car phone holder

— Slide your phone in to position to ensure it charges when docked

Step 4: STOP... Sugru Time! :)

sugru's perfect for this project because it fills weird gaps, is non-conductive (that means it's insulating folks!) plus it's pH neutral so it won't eat your PCB like some silicon caulks can.

— open your sugru and roll into two thin sausages (roll it on paper to keep your desk nice and clean and stop fluff and nonsense getting rolled into it)

— apply one sausage on the backside of your wireless loop (matching the shape of your phone dock)

— apply the other sausage around the edge of your PCB

— gently, but firmly, press everything together, securing it onto your phone dock, as shown.

— let the sugru squidge out a little as you press (next step will explain why)

Step 5: Smooth the Sugru

— Here we're using a coffee stirrer we *cough* liberated from a corporate coffee bar that rhymes with megabucks ;) FYI - they make great sugru shapers

— For a smoother finish usually we'd say use a little soapy water, but in the interest of your PCB, steer clean of water here, just give the sugru a gentle rub with your finger to smooth the surface.

— Leave the sugru to cure for a full 24 hours before using.

Step 6: Position and Program NFC Tag

— Switch on your NFC reader on your phone (somewhere in 'settings' on Android)

— Wiggle around the NFC tag on the back of your phone to find it's NFC reader

— When it finds it you'll see a message saying 'empty tag found'

Program the NFC tag - We used CYNICALifornia's great 'ible here to program ours

We set our NFC to:

+ switch on wi-fi (helps with GPS positioning)
+ switch on data
+ switch on GPS
+ load google maps
+ whatever else you want... maybe a driving playlist :)

Step 7: Ta-da! Your Very Own DIY Wireless Charger and NFC Car Dock

That's it, you're ready to go! It's super satisfying to use every time you get in and out of your car.

If you have any ideas or improvements we'd love to hear from you.

Thanks for being part of our community :)

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    39 Discussions


    1 year ago

    Very nice, this is exaclty what I wanted to do. One question: is the PCB not overheating? I wanted to put it on the back of the phone older to improved the heat dissipation.


    3 years ago

    Holy cow, thank you. This is actually the first time I have ever commented on a blog/whatever you want to call it, with a positive comment. I usually comment after getting immensely annoyed by individuals wasting my time through seeking to instruct the world on things the world (even the ignorant world) already understands. I have a certain car dock for my phone - SlipGrip, that makes custom formed car docks for most flagship phones, where simply sliding the phone into place or pressing a tab to lift it out is all that is required to operate it. Once I learned that Qi charging existed, I set out to find a Qi charger that I could some how fit into an already fitted place without affecting the docks functionality, with no success. I have seen these DIY Qi charging kits on Amazon and eBay but have had no clue as to how to make them work - until this article. Thank you.


    3 years ago on Introduction

    Good guide. Question - is there any issue with reversing the polarity of the antenna coil? ie. switching the solder points around? I ask because I have a micro-USB "down angle" cable that I'd like to use but the way the micro-usb socket is on the board means it becomes an "up-angle" connector, so flipping the PCB over is the easiest fix, but it means switching the solder points for the coil around.


    8 replies

    Hi Steven, without looking in detail at the wiring diagram it's hard to say. However, the principle of wireless charging is that it's an induction loop, and that the current will have a 'direction', so changing the polarity may well change the polarity of the charge. With that said, (although we cannot be responsible for any damage) it would seem unlikely to cause much harm if you were to try switching the polarity, test it and see what happens. The alternative (and possibly best option) is to slightly unwind a little of the loop to give you enough length of to 'flip' the PCB over. Granted this will reduce your induction loops capability, but only by say 5%, if you unwind 5% of the loop, which is probably ok. Given that you are looking into this, I get the impression that you'll enjoy finding out - please post a picture if you get it to work successfully, others may well appreciate it also!


    Reply 3 years ago

    The signal passed from one coil to the other is RF You can not transmit DC current. The Qi transmits power at 100-205 kilohertz well above AC power's 50-60 hertz, and communicates using the same coils the power is transmitted through. The Qi base and the Qi device communicates with each other by using 4 phases.

    Selection: (first phase) Qi uses to determine what if any object(s) have been placed on the charging area.

    Ping: (second phase) Qi tries to determine if the object has a power receiver.

    Indentification/Configuration: (third phase) Qi communicates information necessary to transmit power.

    Power Transfer: (fourth phase) Qi transfers power while maintaining communications. Communications between the device and the base allow the power to be regulated, or cut off based on various conditions.

    Therefore since the coils are simply wire wound in a circle (for the most part), and we are using RF frequencies, the coils don't have to be perfectly aligned, just 'sot of' aligned and can be facing each other in either direction. Lastly coils do not have polarity one end of a wire is the same as the other, both copper or some other conductor.

    Hi, yeah I figured that unwinding the loop a bit would be best, either that or I just buy a USB cable with the opposite-angle connector instead :)

    One thing that I think I will do though is paint the coil (and maybe even the PCB as well) with brush-on electrical tape. It looks pretty ugly without something covering it up

    Hi all, I've completed the hard part of making this charger. I started off with a wireless charging pad I bought off of eBay and took it out of the casing:

    The inside was essentially what the "DIY" kits have in them. I unwound some of the inner coil to allow me to flip the PCB over so the visible components were at the back (which also reversed the orientation of the micro-USB socket, which I needed to have happen anyway)

    The mount is a Brodit active mount for a Galaxy S5. I have unscrewed the micro-USB plug from the bottom (you can see where it was in picture #2) and re-purposed the plug to power the QI charger. For those that don't know, the S5 has a flap which covers the USB3 connector on the bottom of the phone, when the flap is closed properly, the phone is waterproof. You only need a micro-USB 2 plug to charge the phone, that's what the mount came with. A USB3.0 plug is only needed if you want to transfer files at USB3 speeds.

    The charging coil is attached to the mount via a weird rubber-ish sticky pad that was used in the charging pad to keep the coil in place. I wish I knew what the stuff was and where to get more of it because it is really useful. It holds the coil securely in place against the mount but can be removed by giving it a decent tug, without leaving any residue. The PCB is held in place with double-sided foam tape (the black bit on the PCB in picture #2) The whole thing is very secure once installed in-place and isn't going to move unless I want it to.

    The final part of the process will be to buy some black brush-on liquid electrical tape and paint the visible part of the PCB and the charging coil. Will post another photo once it's been painted. I will try and get a photo of the phone in the dock too if you like, but these photos were taken with the phone camera, so I will have to find another camera to use for any pics like that!


    Oh and by the way, I did NOT reverse the direction of the current through the coil. I decided that it was most likely not going to work (DC current and all that) and in any case the way I did it allowed me to flip the PCB so the components are on the back side and not visible. :)

    Here's a photo of the dock now - I have painted the coil with liquid electrical tape and had originally painted the PCB with it as well, but couldn't get a smooth finish, so I put a piece of black duct tape over it instead. The liquid tape started to cure very quickly which led to lumps forming, you can see the finish on the coil isn't great either. Fortunately the stuff just peels off without much problem. I might do something else about covering the coil, either another piece of tape, or a printed "sticker" with the QI logo on it that I have whipped up.

    20150702_135454.jpg20150702_135026.jpgQI White on Black 4.5cm x 4.5cm CIRCLE.jpg

    Here's a final image of the completed dock... QI logo printed on to gloss photo paper and stuck on top of the coil with double-sided tape.


    4 years ago on Introduction


    Really good job, well explained and detailled..

    I would like to build such a wireless charger car dock, but my Honor 6 smartphone does not have wireless received, I 'll buy one to put it in my protection. but I have my credit cards in a "sleeve" on the back of my case (image uploaded)

    could you tell me the maximum space I could have beetween the emitter and the receiver?

    Does it matter if there is plastic, wood or something else in this space instead of air?

    sorry for my english, I hope you understood what I wanna say?

    photo (2).JPG
    1 reply

    Reply 3 years ago on Introduction

    The general range for QI is about 5mm, however I don't think I would want to have credit cards or anything with a magnetic strip in between the receiver and the charging pad, I suspect it would get wiped.


    4 years ago on Introduction

    Did this in my car, but instead of having the NFC tag do all of that, I had it start one of my Tasker profiles that turns on Location, Mobile Data, and Mobile Hotspot. Then, as my car starts up, my head unit (a Kindle Fire) will look for the mobile hotspot and connect. When the Kindle connects to the Mobile Hotspot, a new task starts on the Kindle which opens Google Maps and tethergps to use my phone's GPS, since the Kindle lacks GPS.

    1 reply

    Reply 4 years ago on Step 7

    David, I searched on Google for "Wireless DIY Qi Charger PCBA Circuit Board W/Coil Charging" and found quite a few products. They are usually in the $8-$10 range.


    4 years ago

    Hey guys,
    Great instructable! I finished building the wireless charger portion yesterday and it worked great! I'm having some issues with it today, though. My phone will constantly sync and de-sync with the charger while I am driving, never actually charging. Do you guys have any suggestions? Could it be that my cigarette lighter to usb adapter isn't working properly?