This project was a result of necessity. Lately there are routinely power cuts in Bangalore. I don't have a inverter in the house and wanted an quick and cost effective solution. I already had the working rechargeable battery pack and charger from my Recycling laptop battery project so I quickly designed an emergency light model in the SketchUp.
Design
I have uploaded the SketchUp plans for this project to DOWNLOAD. The body of the emergency light is made from finger joint rubber wood board.
I had a scrap piece of rubber wood board left from the TV Unit project. This board was 18mm thick which was a bit too thick for this project so i had to resaw this piece first with my homemade table saw. This was the first time i have used the table saw to resaw such a wide piece, This piece is about 9cm wide which is too wide for my table saw to cut. I started ripping this piece from both sides by slowly increasing the blade height on each pass. In the end i had to use a hand saw to cut through the small channel about 2cm wide which was left in the centre of the piece. After this i had used a block plane and palm sander to remove all the saw marks and make the surface smooth. After resawing i was left with a 2 planks of 6mm thickness.
Building the emergency light case was very easy i just followed my SketchUp plans. All the pieces were cut on table saw with a mitre sledge. I have used Fevicol MR (white glue) and Feviquick ( CA Glue) to join all the pieces together. I apply the Fevicol on the joints first and clamp all the pieces together making sure that the joints are square, after this I dab CA glue on the joints from inside. With this technique i dont have to wait for the white glue to dry completely and can move to the next step by removing all the clamps and start sanding the surface the CA glue holds everything together.
Front piece of the emergency light has holes for the LED light. For this i have used 20mm and 25mm forstner bits. The wider 25mm forstner bit is used to make a lip for the LED diffuser to attach.
I have used a matt plastic sheet to make the LED diffuser. There are also 2 x 5mm holes on the front panel to attach the charge status indicator LED's. On the back piece i have drilled a hole for the toggle switch. Also have used Dremel to make slot to insert the charging circuit pcb into the back piece so that the micro USB connector on the charging circuit can come out of the back plate.
After making the body i have used Dremel VestsTip with the hot knife attachment to burn the wood surface and carve out the "Tree of life" images on the side of the emergency lights. You can also use a high temperature soldering iron to get similar results. For finishing the surface i have used water based polyurethane polish.
Circuit
For this circuit i have used 3 x 1W LED lights with star heatsink attached and connected in parallel to each other. The 1W LED's that i am using have a peak voltage rating of 3.8V. The charging circuit charges the 18650 battery to 4.2V so the LED's cannot be directly connected to the battery for this reason I am using a step-down DC-DC buck converter and limiting the output voltage to 3.8V. This Emergency Light has a automatic switch on function and will switch on when main power fails. To support this automatic feature i have used a 5V relay which connects the battery to the circuit on power failure. The circuit for the emergency light is pretty simple, I have created the circuit diagram to help anyone understand and design their own emergency light.
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| Automatic emergency light circuit diagram |
The TP4065+DW01 charging circuit that i have used for this project has battery over discharge protection and will disconnect the battery from the circuit when the battery voltage falls to around 2.5V. I have used 3x18650 cells connected in parallel to power the emergency light. These cells have been salvaged from old laptop battery's, you can read more detail on this in my Recycling laptop battery post. These cells that I have used have a capacity of 2400mAh so for 3 cells connected in parallel I should theoretically get 7200mAh of capacity. The 1 W LED's that I have used have a current draw of 3 x 200mA = 600mA so this battery should run the LED's for 7200/600 = 12hrs. This 12 hour runtime is just a theoretical figure as I don't know the real capacity of these old battery's, for my use 2 hour battery is more than enough. I have also successfully tested these battery for 2 hours and the voltage drop was minimal.
I have created a simple dock so the emergency light can be charged and removed from dock easily. I have connected 2 metal contact points on the back of the emergency light which connect to the input of the TP4065+DW01 charger. I avoid using the mini USB port on the emergency light for charging as connecting the USB cable and disconnecting it is inconvenience in my opinion.
Very useful project apoorv. Like the tree of life. I also have versa tip but it doesnt work properly on hardwood.
ReplyDeleteHai Kishore, Thank you...!
ReplyDeleteI have not tried my versa tip on dense wood yet,will try it some time and give you a feedback.
I like this article. I was searching Emergency Light Fittings over search engines and found your blog and it really helps thank you very much.
ReplyDelete