Dear hams. Now there are a lot of radioelements, including imports, to design and simulate your own designs. In Amateur literature, the Internet, you can find a lot of interesting Amateur radio circuitry and components. Every ham knows, as necessary in a home laboratory stable power source. There was a lot of small radioelements and design, began to adopt the compact, freeing the the space on the desktop. A lot of Amateur radio circuits food can be found on chips KREN, CREA, KREN etc But the problem is that the lower limit of adjustment of these chips is 1.2-1.3 volts.
The radio Amateurs have to sometimes use voltage 0,5...1 V. In this spread, the diagram of the power supply (Fig. 1) the proposed solution, where the lower limit is 0 V.
The voltage at the anode of the Zener diode VD3 CSA must be exactly (-1,3). Need to adjust the resistor R8 and to achieve the lower limit of 0.00 V. The resistor on the supply voltage R3, can be calculated by the formula R(Def)=0,7/I(Def). I(Def) - maximum current at which to trigger the protection. Because of the nominal value of 210 Ohms no, the resistor is made up of several. The capacitor C2 can be varied from 10 to 50 UF. Capacitor C3 can be applied at 200 UF, but tantalum. The resistor R5 can apply from 10 to 36 Ohms.
Fig. 1. Schematic diagram of power supply
The price of the LM317 chip and KREN small. This scheme subject to any ham and has a current protection and short circuit protection.The characteristics of this variant
Output voltage is adjustable in the range 0...30,5 V.
Maximum load current of 5 A.
The LM317 chip, without any modifications, is replaced by domestic KREN. The protection system is taken from Radio magazine. The resistor R3 can be calculated on any current protection. Above 5A current lift is not recommended, though you can. The lower limit of the adjustment voltage is set by resistor R8. This resistor should be reusable, type SP5. The upper limit is chosen resistor R7. Positive 5V bus. can to nourish the numeric scale of the power supply.
The printed circuit Board has not been developed, applied point wiring. When using chips CREA transistor VT2 may not apply. Good luck to YOU in the field of Amateur radio.
Author: Anatoly Nikolaevich Patrin, G. Kirsanov, Tambov region, This email address is being protected from spambots. You must have JavaScript enabled to view it. ; Publication: www.evm.wallst.ru, www.cxem.net