FM Transmitter 1 Watt ( 88 MHz - 108 MHz)

Below mention transmitter is very simple to assembled , which is consist of only 2 transistors  ( 2SC2407 & 2 SC3950 )  having a stable frequency & with a high power (Range) is a tough task to do , actually you can buy a high power FM transmitter , but hard to make it due to the restriction as well as parts availability in the certain areas , in my this circuit the input were taken from the Car MP3 modulator , antenna point at the PCB can be easily found , where they always printed the every point on the PCB , if not found the antenna point then you can use the field strength  meter  (FSM) , antenna will be the peak FSM reading , this signal were then given to the circuit , sometime the RF power from the MP3 found low which cannot derive the  first transistor , for this biasing required from positive supply to the transistor base to boost some hove the input signal , 30 k to 56 k resistor can be used for the biasing ,in first stage I used 2sc2407 transistor ,in the final stages 2sc3950 were used , very cheap transistors ,where all these transistor can work very nice in the FM range, RFC were used at the transistor collector which can be easily available in the market  RFC for FM rage will be 0.56 mh  or 0.68 mh (Micro henry)  you don’t have to wound the coil , 2-30 PF Variable capacitor ofr fixed 20 PF capacitor can be used, also you can use 2N2219 , 2N3866, 2N2222 instead 2sc2407 , also you can use 2sc1971 , 2n353 instead of 2sc3950.

DC TO DC UNINTERRUPTIBLE POWER SUPPLY (48 V DC )

One of my friend demanded to design such a project where there is two different DC power supply ,we need to have un interrupted output , this circuit is designed around 48 Vdc , both power supply input mentioned in the circuit are 48v-1 & 48v-3 , both voltages were then combined by the diode  D1 & D2 , it is then down  converted by the R2 (330R, 5W) to make it in the input Rang of LM317 IC 2 , with the R24 & R25 it output will be near 15 V , then after it 7805 IC were used for fixed 5V supply for the whole circuit. Initially if power applied to the circuit ,Relay K1 will energize due to opto-coupler direct connected to the incoming both power supply while triggering transistor T2, IC C & D  will be energized when relay K1 will activated , actually both gates of IC C & D are set as a timers , when power applied to the IC both timers will start , first timer ( C ) will will trigger T3 realy K2 will energized ,the contact of this relay (6 & 4 ) will be disconnected by resulting Q1 off , here Q1 kept off by the R28 ,will be on by the R30 , the Relay ( 200 Amps) which is (SV2-1)  is normally closed ( ON)  ( with no power ) if Q1 enabled it will results relay activated & the contacts will be separated power will be disconnected, on the other the relay  (SV2-3)  will be  activated by  Q2 from relay K3 driven by the T4 , & T4 will be activated by IC1 D ( other timer). if timer run T4 will activated relay K3  , contacts (8 & 4 ) will make , Q4 will be on , capacitor C3 will remain the relay k2 on till capacitor discharged. Buzzer SG1 will be on when relay K1 activated. Threshold voltage level be adjusted by R1