It is a perfect addition to any DIY laboratory power supply, battery chargers and other electronic projects where voltage and current consumption must be monitored. PIC Volt Ampere Meter was designed to measure output voltage of 0-70V or 0-500V with 100mV resolution and 0-10A or more current with 10mA resolution. Note: You can add a 3th 2N3055 and use for R9=27 Ohm, to make a 10/12 ampere power supply of the design stated above. Remember to isolate the transistors from the chassis/radiator! Use a radiator (heat sink) of appropriate size and surface area insulating and heat-conducting spacer or at least a thin mica hot adhesive and thermal paste. amp is needed, so we have some room when short-circuited) the bridge rectifier (D1.D4) only needs 4 x 1N5401 (any +/- 3 amp diodes as only halve of the max. only one 2N3055, will give you 4.5 amps. If there is insufficient load on the output, the output will rise. To do this, all quiescent operating current is returned to the output establishing a minimum load current requirement. Since the 100 uA current from the adjustment terminal represents an error term, the LM317 was designed to minimize IADJ and make it very constant with line and load changes. The reference voltage is impressed across program resistor R1 and, since the voltage is constant, a constant current I1 then flows through the output set resistor R2, giving an In operation, the LM317 develops a nominal 1.25V reference voltage, VREF, between the output and adjustment terminal. You should see equal spaced voltage marks on your home-made scale if your meter is a linear type. Make a mark on your power supply meter-scale to calibrate the meter. If you want to calibrate the scale, turn P1 to several voltages (like every volt) and confirm each time with your calibrated voltage meter. Adjust P3 till the meter needle shows maximum result (end scale) Turn P1 to maximum (maximum voltage of our power supply). Get your hands on a calibrated digital meter or a good analog meter and measure the voltage at the output of the power supply. P2 47 Ohm or 220 Ohm 1 watt * (be sure you can reach 0 ohms as any resistance limits the current) Part list for 6/8 Amp regulatable power supply (PSR28A68):Д1.D4 = four MR750 (MR7510) diodes (MR750 = 6 Ampere diode) or 2 x 4 1N5401 (1N5408) diodes. Remember to use thick wires suitable for transfering the current needed according to the power supply you tend to build. If you do not isolated the finals from the heatsink, then please make sure the heatsink does not make contact with the chassis (metal casing where you plan to build the PS into). The collectors of the finals needs to be soldered with a wire all together if the transistors even if they are isolated from the heatsink or not. When using a 100 Ohm/1watt varistat the current is limited to approx. P2 will allow you to set the limit of the maximum available amps at the output +Vcc. The LM317 maximum output voltage is 30 volts, but using the diodes D7,D8 & D9 the output voltage is approx 30v - (3x 0.6v) = 28.2volt.Д¬alibrate your build-in voltmeter using P3 and, of course, a good digital voltmeter. To have a zero voltage on the output I've put 3 diodes D7,D8 and D9 on the output of the LM317 to the base of the 2N3055 transistors. P1 allows you to 'regulate' the output voltage to anything between 0 and 28 volts. Caution: 42 volt is the voltage that could be on the output if one of the transistors should blow. So all capacitors should be rated at 50 volts. The rectified voltage of: 30 volt x SQR2 = 30 x 1.41 = 42.30 volt measured on C1. Although the LM-317 power regulator will kick in on shortcircuit, overload and thermal overheating, the fuses in the primary section of the transformer and the fuse F2 at the output will secure your power supply.

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