His existing unit operates on two D-type batteries which need to be replaced once they are depleted. [Vadim] wanted to implement a reversible method since he lives in a rented place. He replaced the original cells with battery adaptors and brought out the connections using two wires. He then proceeded to add two cellphone batteries with a TPS54233 regulator so as to supply the desired voltage to the gas heater. This is interesting since the module used is an official Texas Instruments EVM instead of the traditional eBay purchase.
The batteries in question are charged using modules based on the TP4056 which in turn are fed 5V from power supply modules. The DC voltage is coupled with a LM1117 to provide power to the heater from the mains and the switch over is accomplished using an SPDT relay. The enclosure is a humble box which resembles a plastic food container and is fitted with PG9 cable glands along with a fuse holder to boot. Take a look at the original post for a plethora of images and details of construction.
This an excellent example of a project that came together using available parts to solve a problem without the frills. The DIY fish feeder is another example of a project with functional design and is a great example of DIY.
Filed under: home hacks