Beskrivelse: Stabiliseret RFI strømforsyning 12-14V/3A
 Varenr: SK1171
Byggesæt:
RS udstyr som sendere, modtager, walkie-talkies og lignende kræver speciel strømforsyning for at undgå problemer som støj, overophedning, stående bølger osv. Denne strømforsyning tillader ikke RF signaler at passere, men leverer en ren DC spænding på 12 - 14V og en strøm på op til 3A. Beskyttelseskredsløb imod termisk overlast er indbygget. Kortslutningssikker. Anbefales til Smart Kit: 96-26,000,1046, Transformer på 18V/3A er nødvendig. V 18 VAC T 18VAC/3A PCB 72x82mm.
(Transformer medfølger ikke).
How it Works
An a.c. voltage applies at points 1 and 2. The value of the voltage is 18V (AC) and is derived by the secondary of a transformer 220V / 18V / 3A. Between the point 1 and the terminal of the capacitor C1 there is a fuse of 5A for the protection of the circuit. The capacitor C1 is used to reject the interference signals, that are present in the electric network.
The a.c. voltage applies to the terminals of four rectifiers (diodes D1-D4) which form a bridge in order to achieve double rectification. These rectifiers are 1N5400 type which can tolerate a current of 3A. The capacitors C3 (4700ìF) and C2 form a smoothing filter in order to eliminate spurious signals. The dc current that is delivered at the output of the bridge is applied at the input pin (point 3) of the IC1.
The resistors R1,R2,R3 and the trimmer P1 form a small adjustable voltage divider in order to cover the range 12 - 14V (DC).
The divider can be used with devices that need 12V for their operation. Such devices are transmitters, receivers, CB, walkie-talkie, etc. The trimmer P1 is used for more detailed adjustments in the range 12 - 14V, i.e. 12.6V. The capacitors C4, C5, C6 and the coil L1 (type VK200) form a filter that is particularly useful, when the power supply is used to supply transmitters. In that case, because of the existence of static waves, the insertion of the radio frequency in the power supply is possible and can destroy the regulator. However, the electrolytic capacitors because of their technical characteristics have very bad performance in the high frequencies region. Hence,the capacitor C6 (electrolytic) is in parallel connection to the capacitors C4 (ceramic) and C5 (polyester). The last two capacitors operate much better in high frequencies. The points 6 (positive) and 7 (negative) represent the output of the circuit
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