I built a keychain LED flashlight to practice my soldering
Someone recently asked me to replace the battery in their old iPod, and I found myself wondering what I should do with the old battery. It still works, but has less capacity than when it was new. So I looked around my workshop and found some of these surface mount LEDs and decided to test the limits of my soldering skills and make a flashlight out of them.
These LEDs are very hard to solder, since they're surface-mount and the pads are on the bottom of the LED. They were never meant to be soldered by hand, but rather placed by machine onto a specific amount of solder paste, which is then baked in a fancy oven at very specific temperatures for very specific times. To solder these by hand, you need to create a liquid puddle of solder and sorta float the LED on top, while being careful to not short the pads which are very close together as well as not overheating the LED. The temperature the plastic melts at seems to be only a few degrees higher than the solder melts at.
I wired up 5 of the LEDs in parallel, each with its own 6.8ohm resistor wired in series with the LED. This should limit the current to 150mA per LED. I hot glued this in place, as well as a lithium battery charging circuit I got off ebay for a dollar. Here's one such listing.
I slapped on a pushbutton, and Bob's your uncle! It worked first try!
Here's a blurry picture of the finished product. I'm pretty proud of how it came out, considering how tiny and fiddly the soldering was. And, I think I'll actually get some use out of it too. The battery ought to last at least an hour of runtime, and the thing is seriously bright.
Anyone here into electronics as a hobby?
Edit: Better-ish pic: https://i.imgur.com/Kxqy1jg.jpg
No potatoes were harmed in the making of this photo.
That's pretty fun. I made a "sleeper" crazy flashlight a couple years ago, though I have no photos.
I ordered an old vintage metal flashlight and replaced the guts with a LiPo battery and very bright LED. I had to use the body of the flashlight as a heatsink for the LED. It was pretty great. I would post some pics but it's in storage thousands of miles away.
One thing, just be careful with that battery! You might want to give it some protection from punctures.
Thanks, that's good advice! In the case of iPod batteries, it seems they're in a hard plastic enclosure of some sort. At the moment I'm more worried about shorting the battery leads on my keys or something. Or, damaging the LEDs or the tiny wires running to them.
I think for protection I'm just going to spray the thing down with several layers of conformal coating. That'll prevent shorts, liquid damage, and provide a bit of mechanical relief for the delicate parts.
Edit: I just realized I also have some very nice heatshrink that'd fit over the whole thing, so I think I'll do that in addition to the conformal coating. That'll protect the pushbutton and cover all the circuitry, while leaving the back open for the microUSB charging port, and the front open for the LEDs.
Oh yes, shorting can cause a really hot fire as well. Certainly don’t put that thing in your pocket with some keys until you resolve those issues.
That’s why I thought I was so clever with my vintage metal flashlight housings :) Those things were built like tanks!
If you want to play with other batteries, which have even flimsier housings btw, check out https://hobbyking.com/en_us/batteries-chargers/batteries/lipo.html?dir=asc&order=price
Thanks! I do know a bit about lithium battery safety already, though it cannot be overstated. I actually have a fairly dangerously large collection of salvaged lithium batteries. Here's just the ones on my desk. The rest mostly live in a fireproof box with their leads isolated and taped off.
I also own like a hundred pounds worth of Nissan Leaf batteries which are pretty cool. They come in modules of 4 cells, and the modules are about the size of a ream of A4 printer paper. I've got 14 such modules. LiMnO4 chemistry I think. 2S2P layout, 7.4v nominal, ~62,000mAh apiece. I use them to power an electric moped.
Sweet! Yeah, I agree that lithium battery safety cannot be overstated, that’s why I didn’t even preface my comment with any “in case you weren’t aware” clause..
Sweet! Pics?
Sure! Right now I'm actually balancing the battery, so I have the floorboards off and you get to see the guts.
https://i.imgur.com/6mXrCrv.jpg
It was originally a Motorino XPd, which is loosely based on a Honda Ruckus. I've upgraded it a fair bit since then, and I still have a lot of work to do on it. It's pretty much one of those never-ending projects tbh.
That's really awesome! You packaged it really well around the battery too, so it looks super nice. If you don't already have one, you should consider getting a cheap 3D printer and learning a bit of FreeCAD so you can make cases for your projects. So long as you're just putting rectangles together and making angles and simple curves and cutouts, the CAD work is a lot simpler than it looks.
I haven't made a project in a while but a few years back I turned a remote control car into a bot I could drive around on the cell network. It used a USB power pack like you can buy from the store to run the Raspberry Pi and servos for steering and camera turret, and then a larger laptop power pack from Amazon for the motor. The Pi connected via wifi to a mobile hotspot housed in front (super ghetto!). I'm a web developer by day, so it all ran on node.js, which I realize was a pretty odd choice, but it worked quite well. In comparison to your project though, it was much less difficult in terms of soldering skill and electronic knowledge required. You'll see how much of the project was enabled by having a crappy 3D printer around, though, which is why I recommend it.
A 3D printer is definitely on my list of important things to buy. I've never been able to justify the cost since I doubt I'll actually make any money off anything I print, or I won't be able to save the cost of the printer by printing replacement parts for things, etc. But the amount of fun I imagine I'll have with the thing, coupled with my generally terrible fabrication skills makes buying one really compelling.
Lol, when you've got a hammer... Anyway, that looks like a really awesome project and I'd love to learn more about how you pulled it off. I gather that's a camera for POV - how was the latency and framerate? Were you able to control it accurately at speed?
That's kind of where I am at the moment with 3D printers. I've had everything from a self-built RepRap Huxley to some in excess of $20k, but that was because I accidentally ended up consulting for people to repair their printers and figure out settings for non-standard materials, so I got to keep people's printers while doing that. I don't have one anymore. One of those "oh my god that's so many car payments..." situations.
Frame rate was about 10-15fps at 640x480 with not insignificant latency. I don't have data on this but if memory serves on wifi the latency was maybe in the 400-600ms range, but over cell it was more often between 1-2s in normal conditions (and you'll note the Sprint logo on there, so in a lot of places it was unusable). The controls would respond a little faster than the camera, too, so outdoors driving it was more of a turn-based strategy lol. The car would wait for an internet connection and then reach out to a server in my apartment to let it know what its current public IP was, then the browser program that controlled it would request the car's IP from that same server. From there it was WASD and arrow keys to control the car and the camera turret.
Sadly I burnt the motor out trying to go through some thick grass and replacing it just seemed like a serious pain in the ass so I moved on to other stuff.
I've been meaning to make a laser hat to deal with my receding hair line for a while now, but it has taken a back burner to countless other side projects. Even though it's not really an electronics project (more of a fabrication), my friend and I did a video about building an infinity mirror box for his computer. Apologies in advance for the total noob video mistakes. It was our first ever attempt at doing something like this.