This is a small project that simply puts a small LiPo battery charger module in a case. The charger is used to recharge LiPo batteries recovered from discarded equipment which are used for powering USB audio receivers connected to powered speakers at various locations. However, it involves a mounting method that is suitable for similar modules that use PC boards that do not provide suitable mounting points, but which require a secure mounting because they support a USB connector, which may require some force for insertion and removal of the USB connector.
The charger module consists of the USB connector and the components mounted on a 26mm x 17mm PCB. The input, output and battery charge connections are at plated-through holes at either end. There are no mounting holes.
In addition to the lack of mounting holes there is the problem that the IN+/IN- and OUT+/OUT- pairs are spaced at 14mm, which is not a standard hole spacing for protoboard. The B+/B- pair is spaced at 8mm, which is close to, but not quite, 3x0.1" holes. The lengthwise hole spacing is 23mm, which is almost exactly 9x0.1" holes. So the module would fit the protoboard holes on the long dimension, but not on the short dimension.
The solution was to:
The stakes are tinned copy wire recovered from a power supply transformer with the varnish scraped away. The ground track on the copper side of the protoboard runs midway along the gap between the sets of horizontal tracks, which works out to exactly match the width of the holes in the module. The IN- and OUT- are connected on the module, so the connection through the ground track is just an extra precaution. This example is intended for stand-alone charging only, so OUT+ and OUT- are not brought out to any external connector.
B+ and B- are connected by hookup wire brought in through holes from the underside of the header pins. This is easier than trying to stake them (considering that they don't line up precisely with any holes) and then running a connection on the underside.
Holes for the mounting screws in the unused vertical rows are drilled out to a slightly larger size. The case is a simple rectangle to match the protoboard, with two rails run along the base at the sides for screws. The case is so small that it was printed with 100% infill and the screw holes drilled after the board is pressed into the case. The image shows an additional pair of screws added adjacent to the end of the USB connector, to ensure a solid mounting at that end.
The lid is a simple cap with a cutout to allow access to the header pins. Note that the cutout for the USB connector seems to suit most micro cables because they have the housing set back from the insert by the case wall width of 2mm. This places the cable housing flush with the end of the case.
The arrangement for using the module for charging a small 1000mAh LiPo battery.
The completed unit with adhesive label. A short section of
transparent plastic rod (a left over sprue from a model kit) is placed
over the two LEDS and protrudes through a hole in the cap so the light is
visible. The space allowed either side of the header strip is there
because some of the connectors are 3 pins wide (for consistency with
multi-cell batteries that have a balance wire) even though only two are