For effective drying of shoes, a constant influx of warmer, and therefore less humid air than the surrounding air is necessary. According to this principle, the proposed dryer works, the scheme of which is shown in Fig. 1. Resistors R1 – R12 are used as heating elements. A fan blows them, and heated air enters the shoes through the air ducts.
The supply voltage to the DC motor M1 of the fan is supplied through a rectifier bridge VD1-VD4, so that the device can be powered from a source of both direct and alternating current (in the latter case, capacitor C1 smoothes the ripple of the rectified voltage).
Structurally, the dryer consists of a heating chamber and two air pipes inserted into the shoes. The heating chamber is made of a plastic junction box measuring 100x100x35 mm, designed for electrical wiring. A hole with a diameter of 70 mm is cut out in its cover and a fan is fixed from the outside from the power supply unit of a personal computer (Fig. 2) and a two-pin instrument plug for connecting a power source. The fan is installed so that it pumps air into the box. The other elements are mounted on the back side of the cover (Fig. 3): resistors R1 — R12 — above the fan hole (to blow air), and diodes VD1 — VD4, capacitor C1, and resistor R13 — next to the cover wall (after checking the device for their performance should preferably be fixed with hot-melt adhesive).
Openings for air ducts are cut in the side wall of the housing. It is convenient to use plastic (unreinforced) water pipes with an internal diameter of 3/4 inch (19 mm). They can be easily processed with simple tools, and when heated, they can be deformed (bent). Cutting off two blanks of the desired length. at one end of each of them with a sharp knife, a cut is made up to about half the diameter, and at a distance of about 60 mm from one another, two holes are drilled for fixing screws.
Then, having drilled the same holes in the bottom of the box, the air ducts are fastened to it with screws and nuts МЗ (Fig. 4). Their opposite ends after heating over a gas (or electric) stove can be bent at the desired angle. For a better and more uniform air outlet, it is advisable to drill several holes with a diameter of 4 ... 5 mm in the pipe walls. The appearance of the dryer in the working position is shown in Fig. 5.
In the dryer, you can use resistors C2-23, MLT with a dissipated power of 2 W and an oxide capacitor K50-35 or a similar imported one; diodes - any small-sized rectifier with a direct current of at least 200 mA and a reverse voltage of at least 50 V (it is possible to use a ready-made rectifier block, for example KTs407A). A power source, as mentioned, of direct or alternating current with an output voltage of 12 ... 14 V at a load current of at least 3.5 A. Suitable, for example, a power supply from a personal computer or a step-down (220/12 V) transformer for halogen lamps . The fan speed is regulated by the selection of resistor R13 (it should not be set j as high as possible, as this will lead to a decrease in the temperature of the supplied air).
A further development of the device may be the automation of the drying process, for example, the introduction of a temperature control system or a timer that turns off the dryer after a specified time.
Source: Radio 9`2008