Intro: Hot Wheels USB Rechargeable Flashlight
Make a small USB rechargeable flashlight out of a Hot Wheels sized car with LEDS and a decent amount of hot glue in tight spaces.
Over the last few years I've been working on a lamp idea involving Hot Wheels cars and LEDs where the headlights should go. I'm still tinkering on the big project but along the way I found this little side quest to be fun and inexpensive. Taking a small USB flashlight and striping it down to fit into a Hot Wheels car can be an exercise in packing stuff into tight spaces, but with the right car it can turn awesome.
The black car? That is a later attempt that I made, after I had a clue what I was doing.
That is a genuine Hot Wheels car (1999 version) of the 1938 Phantom Corsair. If you are interested I have that model available in my Etsy Store at: https://www.etsy.com/listing/108285700/hot-wheels-usb-rechargeable-flashlight
Step 1: Parts and Choosing the Right Car
Hot Wheels and similarly sized die cast vehicles are at 1/64 scale. A 3mm LED turns into a 192mm (7.6 inches) headlight. Bigger than normal but not so far off.
Choosing the right car is critical. It needs to have a enough empty space inside the vehicle. Say enough room to take $1.50 in quarters stacked up. Also pay attention to things like how the headlights are depicted on the car - are they basically flat on the front grill or more sloped? Having the front grill perpendicular to the ground makes it easier to fit them in and drill out the holes where they go. Even with a couple of these under my belt I destroyed some Mini Cooper models due to the sloped headlights.
Be aware that Hot Wheels cars generally have open windows and seats and a steering wheel inside the car. You will have to remove this added interior details to make the flashlight guts fit. I tried doing custom tinted windows in a few cars and it did not turn out well, so for now it's exposed flashlight parts if you look inside.
For a first vehicle, I'm going to recommend a brand that isn't Hot Wheels. Walmart (and other stores) carries the Adventure Wheels brand from Maisto, these cars are slightly larger (more room to play with) and have black plastic windows and no interior detailing. Sweet.
The parts List is basic:
pair of 3mm white LEDs
USB mini B female socket
a couple of 2-56, 1/8" long pan head machine screws - holds the car together when you are done.
A USB cable that can plug into a mini port - this is very common and you probably have a few laying around right now.
The car I got at the local Walmart. All the rest I got off Ebay and the local hobby store.
Try to get the brightest 3mm white LEDs you can find, mine are 20Kmcd at 20ma models, 20 degree focus. $3.5 for qty 50
USB Flashlight - it has a small pcb with surfact mount componets, a battery, a 5mm LED, a switch and a USB male socket. It generally goes for around $3 to $4 on Ebay.
Others have stuck USB flash drives out the back of a Hot Wheels car with the big USB socket sticking out. I'm trying to have it be compact so I'm replacing the USB socket with mini female version. Get one with pins sticking out, not the SMT type. Usual price is around $4 for 10 or so.
Small screws - try a local hobby store or ebay or even Amazon - small parts has a number of these.
Step 2: Hack Apart the Car
1/64 die cast cars (of which Hot Wheels is the most known brand) are held together with rivets on the bottom of the vehicle.
We drill out the rivets and you can pop the bottom part right off the chassis.
Because you might want to get back into the car after you put it all together, replace the rivets with some small screws. I'm using 2-56 machine screws, 1/8" long with a pan head.
Now to drill out the rivets - a two step process.
Drill down with a 5/64" bit, deep enough for the the 2-56 machine screw. I usually try for 3/16" deep just for clearance. With this size drill bit and in the soft die cast metal, the machine screw with cut it's own threads.
Then use a 3/16" drill to remove the head of the rivet. Don't go in too far, try and stop as soon as the head is removed.
At this point, use a small screwdriver and pop the chassis off the bottom plate.
Now you have the car in all it's parts - set the wheels aside, you won't need them till you put the car back together at the very end.
Step 3: Hack Apart the USB Flashlight
The USB Flashlight is in a plastic shell that is easily removed. Pry off the lens part with a screwdriver, then start cutting the plastic with a small pair of wire cutters or other set of pliers.
Once you get down to the pcb and battery, it's time to desolder!
Step 4: Desolder Parts Off the PCB, Run Extension Wires
There are four external parts connected to the PCB:
1) The Battery
2) USB Port to supply charging power
4) 3 position switch
We are desoldering off the PCB everything but the battery - just leave that in place and don't mess with it.
Confession time: I suck at desoldering. It always takes me longer than it should and I burn everything, including my fingers
The good news, even a hack job like I normally do did not kill the surface mount parts on the PCB. So take your time and take off the components. Mark on the board the plus/ground connection for the LED and USB port, I usually put a red sharpie dot next to the correct connection.
On the USB socket, there are four soldered connections. The two outside ones are the power connections, with the positive one being the one next to the red wire for the battery.
Once everything is removed, you need to solder in a jumper for the switch casing connections. The switch case is used as a ground connection, it is soldered in on both sides of the board and once desoldered you need to run a jumper from one to the other - see the final picture in this step. Took me awhile to figure that one out.
While the soldering iron is still hot, solder in the extension wires for the three components you took off. You only need a few inched for each, and thin (26 to 30awg) is good.
A red and black for the LED
A red and black for the USB socket
Three wires for the switch. - the middle and two outside pins are the ones that matter.
Step 5: Drill Holes in the Chassis for the LEDs
Because each chassis and location of the headlights is different you will need to check out where they can fit each time.
Using a 3mm (or 1/8") drill bit, see where they can go. Is there clearance on the side? Is it going to hit the center post?
It's not so much where they should go to be accurate for the model, it's more where will they fit? Don't worry if it's not perfectly aligned to where the headlights are on the model - heck, the model lights might be rectangles.
To make sure I get good placement, I take an awl and make a dent where I want the hole to go. then I scale up the drilling.
Using a hand pin vise, I drill a small 1mm or so starting bit. This gives the followup bits someplace to dig in and not wander.
Then with the cordless drill I drill it out with a 3/32" all the way in.
Finally finish up with a 3mm (or 1/8") drill bit.
You should have a couple of holes ready for some LEDs at this point
Step 6: Glue in the Window and Add LEDs to the Chassis
Because the window part is under where the the LED leads will be going, you need to put that back in the chassis.
A small dap of hot glue and pressing down firmly will handle the job well.
Now add the LEDS. They are wired in parallel, so keep track of which connection is positive and which is ground.
Every chassis is different, but often involves bending the leads around the rivet post and other parts inside the chassis.
I put heat shrink on the wires before I put them in the chassis to prevent short circuits.
Once you have the LEDs in the chassis, use a dab of hot glue to keep them in place.
Step 7: Cut Holes in the Bottom Plate for the Switch and the USB Socket.
One of the nice things with the modern, cheaper cars is that they don't use die cast bottom plates, it's all plastic. That is much easier to deal with.
Drill some holes together to get started for the USB socket. Then take a utility knife and cut around the holes until you have a socket shaped hole. You might need to shave the sides a bit but a fresh blade in a utility knife will make short work of it.
Figure out where you want the switch as well and do the same for it. You don't want to drill out for the entire size of the switch, just enough for the part that moves to go back and forth.
Step 8: Solder the Parts Together
Solder the USB socket and 3 position switch to the extension wires you put on there. I recommend you test fit and check wire length before hand, but just a few inches should be fine as well.
On the USB socket, looking at it from the rear, the positive connection is the one of the far right, and the ground is on the far left. The three connections in the middle are data/spare and can get trimmed.
Wrap the PCB and battery together in a bit of electrical tape to protect it from shorting.
Finally, solder the extension wires for the LEDs. Make sure you are not shorting them out and even a dap of hot glue is not out of place. Now that it's all wired up correctly for the first time, try the switch to see if it works.
Step 9: Glue Parts Into the Bottom Plate and Final Assembly
Now carefully put your USB socket and 3 position switch in place and hot glue them down. They should be sticking out far enough of the bottom that you can use them, but not far enough to interfere with the wheels. On most cars the standard height of the switch works perfectly.
Put the wheels back in their place and pop the bottom plate back in position. Screw in the 2-56 screws into the rivet posts to hold it.
You are done!
Congrats! Enjoy and amaze your friends with your new Hot Wheels Flashlight.