48 V DC to 5 V DC Converter circuit

  High voltage DC conversion to a low level is tough task , but it is not that difficult task so  this circuit is consist of Transistor based DC voltage  down converter circuit , here a power full transistor TIP35C were used , a smal network of resistor 4.7k , 100R 5W , Zener diode 12V, capacitor 220uf were used , Zener Diode first limited the voltages up to 12 from the input with help of TIP35C , a diode IN4001 used for protection to the circuit, this 12V were then applied to any other regulator IC like 7805 or 7809. any other other powerfull transistor be used like 2SC5200.

                                     

DELAY OFF TIMER ( 3vdc to 5vdc )

Some time timer circuits  required for some sort of delay while designing a project  but on a low  voltages we have to design such a special circuits which can even work by taking power from even mobile battery ,the IC 4001 is the best choice for it , even up to 4 timer can be made from one IC package  ( 4 Gates), a very stable & reliable time circuit , using of different values of Capacitor & resistor a different timer  interval can be possible to be made ,  this timer which can work on low voltages like 3vdc to 5 vdc ,this circuit can be used from 12 to 3V dc.

Sound activated switch circuit ON/OFF

Here is a simple sound activated circuit assemble this circuit the transistor is directly driven from the speaker output , a capacitor connected with a relay in parallel to avoid some small gape ( intervals)  connect it with your mobile phone ring output ,save a continuous tone (beep) in your mobile , set this tone for specific contacts (family members)now assemble it with your house main gate lock ,keep your mobile in silence profile just set continuous beep for specific family members by calling the mobile output will be appear from mobile ring output it will trigger the relay this relay will drive another relay it will  trigger the lock on, Only known contacts will access the main gate other unknown will not be entertained where there will be no output if unknown will call.lock will be remain open while ringing continues.

homemade pcb making

For any electronic circuit assembling it required a PCB board ,it may be bread board, dotted board or special PCB board which you have to design and then printed
You need to have a laser printer with a maximum DPI ,for clear print , for paper search for shiny surface like used in monthly magazine would be a great choice, cloth iron used for 3 to 5 minutes after printing 2 basic etching procedures are followed ,for one a ferric chloride is used , the other is a solution of HCL + hydrogen peroxide ( HCl + H2O2),
You must learn any PCB design software like Cad Soft , where you express you idea better .

Motor Control Circuit

A very Classical motor driver circuit found in many appliances, this circuit is made around two 5 pin relays, here DC power to the motor in either direction will be possible by the both relays by pressing the buttons, if button S2 pressed –Ve current will flow through relay K2 coil , to the +Ve terminal.by activating the relay K2 , the relay (C) point will be connected to the ( NO) , +Ve  will be flow towards (motor SV1-2) , the –Ve for this motor SV1-1 will be routed through K1 ( C & NC ), it will rotate in one direction , if button S1 pressed –Ve will flow through S1 ( 1 & 2) will energized relay K1 , -Ve will flow through K2 ( C & NC ) & +Ve will flow through K1 ( C & NO ) pins 

ON/OFF Switch GSM based (DTMF)

Below is a simple on/off switch using GSM mobile network .It will work on miss call option , for which you don't have to pay , one miss call for ON and other for OFF .due to the latching output from the decoder 8870 & 4028 IC , it is recommended to record two DTMF tone in mobile & set it as a ring tone for a specific user ,It means that if we call the said mobile , lets i have set 2 DTMF tone 9 & 6 , output from IC 4028 pin # 5 which having # 9 DTMF tone is connected to opto-coupler PC817 then it is connected to IC 4013 ON/OFF switch ,Once you call the mobile it will once activate (on) the pin # 9 while DTMF tone # 9 was set first , than after it tone # 6 will be observed at 8870 , so it will activate # 6 , pin # will be off ,again by calling the  the mobile circuit will be ready for the next action either off or on.For confirmation a simple switch will be added to make call busy or continuous ringing which will confirm that the desire action ON or OFF successfully done.