The first ever item that we tore down in HackSpace magazine was a dancing Christmas tree and, as we write this latest edition, our minds wander to the festive season, which is only weeks away. In recent years, homes around the world have prepared for Christmas in even more outlandish ways – and surely the most brash and unashamed manner is to project Christmas all over your home using an outdoor projector. But, how do they work, and what can we do with one? Well, there is only one way to find out: we need to take one apart!
Pull it to pieces
The projector is made of a workable plastic, and comes in a series of sections. For example, the lens section is held on with four large cross-head screws. When removing the lens section, we discovered that the lens is real glass, and that the lens is secured over the projection plate with a water-resistant cover, helping to restrict water ingress. Where the power lead comes into the projector, we see a gland that covers the hole for the wire, and protects the unit from water. There’s no rubber seal however, so be careful!
The unit is held together using a mixture of hex screws and cross-head screws. The hex screws are used to cover an access slot where we can insert ‘cartridges’ containing the images to project. Inside the projector, there are multiple cross-head screws, of different sizes. The smallest hold a blanking plate over the LED lenses, to prevent light leakage. The thickest are those that hold the motor and LED PCB to the projector chassis. Just be careful with these screws, as they are really close to the power wires for the motor!
The images projected are made possible using a selection of cartridge slides that contain four images based on seasons/events or celebrations. These cartridges measure 65 mm by 45 mm, by 3 mm thick, and are made of the same plastic as the projector. They can be carefully taken apart to find inside two small lengths of plastic film, with the images printed upon them. Why is this important? Well, using a good-quality printer and some OHP (overhead projector, remember those from school?) transparency sheets, we can print our own images! Trial and error will be required, but the cost of the sheets is negligible.
In the box we find a 12 V 300 mA mains power supply, which provides 3.6 W of power, slightly less than the rated 4 W, but enough. The power supply connects to the projector via a 4.8 metre power cable, and it uses a screw thread and polarised connector to ensure correct polarity and for a secure connection. This also provides some water resistance as it is rated IP44 (typical for bathroom electronics that might get sprayed), but do not rely on this rating for outdoor use. Ensure that the plug is connected to the mains via a fully rated and waterproof outdoor connection.
Sadly, we can’t run the projector from a USB 5 V supply, as there’s not enough power. But if we use a 5 V to 12 V step-up voltage transformer, typically USB to DC barrel jack, then we can power the unit from a USB battery for ultimate portability! The USB output will need to be over 2 A, with 2.4 A being the sweet spot. Typically, these step-up transformers can supply up to 12 V 800 mA, over double the requirements of our projector! If you ‘roll your own’ power supply, do ensure that it is safe and it exceeds the current demands of the projector.