I like to draw, design, sketch, read in bed at night before going to sleep. With the wife sleeping beside me I decided to design a light I can use that will stand on it's own while throwing a light on my page. I love to reuse materials whenever I can - altoids tins for project boxes, components from outdated electronics, etc.
Step 1: Gather Parts
I've been thinking of making a portable bedside light for some time. For this project I want to use a 3.7v 18650 rechargeable battery salvaged from an old laptop battery pack. For a container something large enough to hold the bigger size of the 18650 battery. & I want to be able to charge the light using a solar panel.
large 200 pc tictac container - Giant Tiger
3.7v 18650 cell - from laptop battery
1w high-power cool white led
1w-3w 30degree clear optical lens
MR16 1x1w 320-350mA cc regulated
XL6009 DC-DC Adjustable Step-up boost Power Converter Module
TP4056 5V Micro USB 1A Lithium Battery Charging Board Power Charger Module
lengths of red & black 22AWG wire
As for the cost, it depends what you have laying around. Tictac container $2.49 at Giant Tiger, 3.7v battery free from outdated/broken laptop, 1w led was maybe a buck from ebay, optical lens 5 for about a dollar, mr16 maybe a dollar, xl6009 about buck & a half, TP4056 - 10 for $3.33, on/off switch & wire.
Cost under 10 bucks. More if you have to buy everything.
Step 2: Start With
For this project I wanted to get away from using a battery holder eliminating the need to take the battery out every time it needs charging. Instead I opted for a tp4056 solar charge module soldered to the circuit to allow connection to a solar panel usb, car power point usb or other 5v usb connection to charge the battery.This 18650 battery has a red & black wire soldered to the positive & negative ends of the battery, which is how I found it in the laptop battery case. Most convenient.
Overview - To power the 1w white led I used a mr16 led driver to deliver the 350mA constant current. 12v is needed to run the mr16 so I used a XL6009 3-12v in to 12-24v out boost converter to up the 3.7v of the 18650 to the 12v needed. Lastly a tp4056 module was attached directly to the battery to allow charging using a micro usb cable. I used the sketch above to work from. If you find my explanation doesn't quite do it for you maybe the sketch might be easier to understand.
Step 3: Next
After soldering a red wire to one side of the on/off switch & 2 red wires to the other I then drilled a hole in the case & pushed the switch in place. Placing the aluminum star heatsink for the led approx. where I felt it should go on the tictac box I put 2 felt pen marks on the case where the led wires go through the case. Drilled these small holes then hot glued the led aluminum star heatsink to the plastic tictac case. This will hopefully dissipate some of the heat developed by the led into the plastic case.
Turns out fastening the 1w led's star heatsink with hot glue to the case is not the way to go. Duhh! Lasted maybe ten whole minutes before the heat from the led sprung the led star from the case.
Step 4: Thermal Adhesive
I haven't worked with this particular adhesive before & I don't know if it will adhere aluminum to plastic but feel it's worth a try. It's called Arctic Alumina Thermal Adhesive & it comes in 2 syringe-like tubes that need to be mixed in equal parts before applying to the parts. Simple to use, keeping my fingers crossed.
Step 5: That's It...!??!?
With the tp4056 placed at the top so the micro usb can be accessed by opening the tic tac dispenser lid.
I imagine with a little forethought the electronics can be fit in the container in an orderly fashion. Not crammed in as mine! The optical lens is sitting a bit wonky until it's hot glued in place. I'm thinking I might change the lens for a wide angle so I haven't glued it in place.
The 1w led throws a decent light, perhaps a tad too bright for what I intend to use this light for, but I'm happy with it nonetheless. I'm quite surprised at the area it lights outdoors.
I'm not an electrician but a dreamer. I like to create things to fill a need for the sheer perverse satisfaction! This project was definitely fun to make & I like the way the components are visible through the clear plastic of the tictac box. It seems there are bugs to be worked out but that's part of the fun of it.
Any help would be appreciated!
Step 6: Back in Business!
The orange 18650 drained after the first night. I must admit I did use it a lot outside & in as I'm very impressed with the amount of light it produces. The tp4056 module only protects the battery from overcharging above 4.2 volts. It doesn't stop the battery from draining.
Found a blue 18650 with wires attached. Snipped out the orange battery & soldered in the blue. Working once again.
I really like this project & want it to succeed. Hope I'm not expecting too much out of this 18650 cell having it drive the hi power led.
Step 7: Circuit Protection
After swapping batteries I then monitored the voltage level throughout the day. Didn't lose any voltage from the 18650 all day so this evening I decided to put the light back together. But... I couldn't do it. I kept thinking about circuit protection, I have a circuit here, might as well solder it in to be safe. I taped it to the battery after soldering hoping it will hold it together when I squeeze all the components into their new home. I bought this module a year ago so I don't recall much about it. I see a similar unit at Fasttech selling for $1.20. Operating voltage 3.6 - 4.2v. Dicharge cutoff 2.4v, charge cutoff 4.25. That should save the battery from draining out.
I've ordered a charge protection module that has 4 leds that indicate the level of charge in the battery when a button is pressed.