The only tricky bit here is identifying the three terminals of the transistor, once you have done that, the rest is a walk over. The inductor gets connected to the emitter, and the supply wires get connected as shown. Next, take a length of stiff wire, form it into a circle about the size of the loop on the LED and solder it between the other side of the resistor-capacitor combination and the collector of the transistor.
#Xstand wireless led how to
Or you can try to identify the base by using the multimeter (if you have one, and you know how to use it). Some types of transistors have the base lead in the middle, so look up the data sheet to find out. Next, identify the base lead of the transistor and solder one end of the resistor-capacitor parallel network to it.
When both their leads have been joined together by two blobs of solder they may be handled as a unit. They may go together any way - they are not polarised, ie, have a "positive" or "negative" terminal. The transistor I mentioned in the parts list (BF494) died, and the one in the pictures is another one (one of many that I tried) that worked, that I found in my junk box.įirst, the capacitor and the resistor are soldered together in parallel. The rf induced in it is rectified by the LED and it simultaneously emits light.Ĭonstructing the oscillator circuit is very simple: All the components are just soldered together to form a self-supporting assembly. On the receiving side, the leads of the LED are bent over to form a circle. The emitter is allowed to float at rf by the inductor, while the current returns to the battery through it. The base is grounded for rf by the capacitor, while still allowing the base to get current. The resistor supplies current to the base of the transistor so that it will turn on and pass current. The one I used (found in my box of junk) had a value of 330 microhenries - marked by two orange bands and a brown band. On the emitter of the transistor is an inductor - the value of this, too, is not critical, and any value from a few tens of microhenries upwards would work. On the collector of the transistor is the induction loop - this is just a single circular loop of wire, to match the loop of wire connected to the LED. It overheated and died when I tried to increase the brightness of the LED by increasing the voltage to 12 V - so, keep your battery voltage down to 6V if using the BF494 or equivalent transistor. Then comes the transistor - I first tested the circuit using a BF494 transistor - this is a high frequency low power transistor used in the front end of medium wave radios. I used a 0.1 microfarad capacitor, although any capacitor in the range 100 picofarad and upwards will work. The 33K resistor will have three orange bands on it, and then a silver or gold band.
The voltage is not critical, and I tested it using the output from my mobile phone charger too. I used four AAA cells in a holder to test this circuit. The longer dash represents the positive tab, the "pip" if you are using AA cells. On the extreme left is the symbol for the battery. I shall explain the circuit diagram, taking each component (or its representation) from left to right. When the two loops are placed close together (but not touching) the LED lights up. The LED's leads are formed into a matching loop and soldered to form the receiving loop. The inductor is a wire formed into a circular loop. Due to feedback inside it, it oscillates, converting a portion of energy from the battery into radio frequency energy. A high frequency transistor is connected to an inductor, and biased to its active region.
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