The range of application of photocells is extremely wide. They are necessary in signaling systems, where they are used in a photo relay, triggered by an interruption of the light flux. Without them, it is impossible to make some communication systems, for example, light telephones, including laser ones. Photocells are widely used in various measuring devices. However, they are not always on sale. But the photocell can be made by yourself.
It is necessary
- -old photoexposure meter;
- -semiconductor diodes;
- - out of order microcalculator;
- -spring contacts;
- -transistors;
- -soldering iron;
- -multimeter or avometer;
- -file.
Instructions
Step 1
For the manufacture of a modern device, you can use: a ready-made photocell from an old photoexposure meter or a semiconductor diode in a glass case. Clean the light-shielding paint from the diode, if any. Almost all LEDs can function as photocells.
Step 2
Make a photocell from a solar cell from a microcalculator. Keep in mind that you cannot solder the reins directly to the photocell. Heating it will almost certainly ruin it. Therefore, if the battery has taps that are not suitable for soldering, it is best to secure its plate with spring contacts. They can be taken from failed electromagnetic relays. Secure the spring contacts at one end in the board by soldering the wire taps to them. The other ends should be positioned so as to press against the desired conductive sections of the solar panel. The same applies to selenium or silicon plates from photoexposure meters.
Step 3
Photocells made from solar cells of microcalculators and photographic exposure meter plates are very inert. Therefore, they are only suitable for teleautomatic devices. To receive a modulated light signal (for example, a light telephone), higher frequency elements can be made. They can be made from old germanium or silicon Soviet transistors of the P or MP series. They are found in broken receivers or tape recorders. They are often sold on radio markets.
Step 4
The body of such a transistor looks like a specific "hat", in the lower part of which there are electrodes, and the upper part covers the semiconductor crystal. You can do this. Use a file to cut the uppermost part of the body. Remove it carefully. Blow off sawdust with a blowing vacuum cleaner
Step 5
Using any measuring device (tester, multimeter) measure the photocurrent between pairs of electrodes. There are three such electrodes: emitter, collector and base. Typically, the highest current occurs at n-p junctions emitter-base or collector-base. Choose the pair with the highest photocurrent. Naturally, the higher-frequency transistor you use, the higher-frequency the photocell will turn out to be. Accordingly, more powerful transistors will give a greater photocurrent. Measurements should be made by illuminating the photocell with a reference light source (for example, a table lamp from a constant distance.
