Low Cost Switcher Converts 5 to 24V

This is a simple circuit. which is Low cost switcher converter 5v to 24v by using OPamp.

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A very simple Inverter circuit - 12 volt DC to 120 volt AC

This is a very simple inverter circuit. This Inverter takes 12 volt d.c and steps it up to 120 volt a.c. The wattage depends on which transistors you use for Q1 and Q2, as well as the "Amp Rating" of the transformer you use for T1. This inverter can be constructed to supply anywhere from 1 to 1000 (1 KW) watts. If Q1, Q2 are 2N3055 NPN Transistors and T1 is a 15 A transformer, then the inverter will supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power.

Parts List:

C1, C2 --------------------- 68 uf, 25 V Tantalum Capacitor

R1, R2 --------------------- 10 Ohm, 5 Watt Resistor

R3, R4 --------------------- 180 Ohm, 1 Watt Resistor

D1, D2 --------------------- HEP 154 Silicon Diode

Q1, Q2 --------------------- 2N3055 NPN Transistor (see "Notes")

T1 ---------------------------- 24V, Center Tapped Transformer

Others:

Wire, Case, Receptacle (for output)

Fuses, Heatsinks, etc.



Note: Don't try to connect this inverter with loads motors .

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Mains Switch Manager

Introduction:

Very often we forget to switch of the peripherals like monitor, scan ner, and printer while switching of our PC. The problem is that there are separate power switches to turn the peripherals off. Normally, the peripherals are connected to a single of those four-way trai ing sockets that are plugged into a singl wall socket. If that socket is accessible, a the devices could be switched off from there and none of the equipment used wi require any modification.

Description:

Here is a mains manager circuit that allows you to turn all the equipment on or off by just operating the switch on any one of the devices; for example, when you switch off your PC, the monitor as well as other equipment will get powered down automatically. You may choose the main equipment to control other gadgets. The main equipment is to be directly plugged into the master socket, while all other equipment are to be connected via the slave socket. The mains supply from the wall socket is to be connected to the input of the mains manager circuit.

Operation:

The unit operates by sensing the current drawn by the control equipment/load from the master socket. On sensing that the control equipment is on, it powers up the other (slave) sockets. The load on the master socket can be anywhere between 20 VA and 500 VA, while the load on the slave sockets can be 60 VA to 1200 VA.

During the positive half cycle of the mains AC supply, diodes D4, D5, and D6 have a voltage drop of about 1.8 volts when current is drawn from the master socket. Diode D7 carries the current during negative half cycles. Capacitor C3, in series with diode D3, is connected across the diode combination of D4 through D6, in addition to diode D7 as well as resistor R10. Thus current pulses during positive half-cycles, charge up the capacitor to 1.8 volts via diode D3. This voltage is sufficient to hold transistor T2 in forward biased condition for about 200 ms even after the controlling load on the master socket is switched off.

When transistor T2 is ‘on’, transistor T1 gets forward biased and is switched on. This, in  turn, triggers Triac 1, which then powers the slave loads. Capacitor C4 and resistor R9 form a snubber network to ensure that the triac turns off cleanly with an inductive load.

LED1 indicates that the unit is operating. Capacitor C1 and zener ZD1 are effectively in series across the mains. The resulting 15V pulses across ZD1 are rectified by diode D2 and smoothened by capacitor C2 to provide the necessary DC supply for the circuit around transistors T1 and T2. Resistor R3 is used to limit the switching-on surge current, while resistor R1 serves as a bleeder for rapidly discharging capacitor C1 when the unit is unplugged. LED1 glows whenever the unit is plugged into the mains. Diode D1, in anti-parallel to LED1, carries the current during the opposite half cycles.

Don’t plug anything into the master or slave sockets without testing the unit. If possible, plug the unit into the mains via an earth leakage circuit breaker. The mains LED1 should glow and the slave LED2 should remain off. Now connect a table lamp to the master socket and switch it ‘on’. The lamp should operate as usual. The slave LED should turn ‘on’ whenever the lamp plugged into slave socket is switched on. Both lamps should be at full brightness without any flicker. If so, the unit is working correctly and can be put into use.

Note:

1) The device connected to the master socket must have its power switch on the primary side of the internal trans- former. Some electronic equipment have the power switch on the secondary side and hence these devices continue to draw a small current from the mains even when switched off. Thus such devices, if connected as the master, will not control the slave units correctly.

2)  Though this unit removes the power from the equipment being controlled, it doesn’t provide isolation from the mains.

So, before working inside any equipment connected to this unit, it must be unplugged from the socket.

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Make a Mini UPS System

This is a simple circuit that’s provides an uninterrupted power supply (UPS) to operate 12V, 9V and 5V DC-powered at up to 1A current. The backup battery takes up the load without spikes or delay when the mains power gets interrupted. It can also be used as a workbench power supply that provides 12V, 9V and 5V operating voltages. The circuit automatically disconnects the load when the battery voltage reduces to 10.5V to prevent deep discharge of the battery. LED1 indication is provided to show the full charge voltage level of the battery. Miniature white LEDs (LED2 and LED3) are used as emergency lamps during power failure at night.

step-down transformer provides 12V of AC, which is rectified by diodes D1 and D2. Capacitor C1 provides ripple-free DC to charge the battery and to the remaining circuit. When the mains power is on, diode D3 gets forward biased to charge the battery. Resistor R1 limits the charging current.  Potentiometer

VR1  (10k) with  transistor T1  acts  as the  voltage  comparator  to  indicate the voltage level. VR1  is so adjusted that LED1 is in the ‘off’ mode. When the  battery  is  fully  charged,  LED1 glows  indicating a  full voltage  level of 12V.

When  the  mains  power  fails, diode  D3  gets  reverse  biased  and D4  gets  forward  biased  so  that  the battery  can  automatically  take  up the  load  without  any  delay. 

When the battery voltage or input voltage falls below 10.5V, a cut-off circuit is used to prevent deep discharging of the battery. Resistor R3, zener diode ZD1  (10.5V)  and  transistor  T2  form the  cut-off  circuit.  When  the  volt- age  level  is  above  10.5V,  transistor T2  conducts  and  its  base  becomes  negative (as set by R3, VR2 and ZD1).

But when the voltage reduces below 10.5V, the zener diode stops conduction and  the base voltage of  transistor T2 becomes positive. It goes  into  the  ‘cut-off’ mode  and  prevents  the  current  in  the  output  stage.  Preset VR2  (22k) adjusts  the voltage below  0.6V  to make T2 work  if  the voltage  is above 10.5V.

When  power  from  the  mains  is  available,  all  output  voltages—12V,  9V  and  5V—are  ready  to  run  the  load.  On  the  other  hand,  when  the  mains  power  is  down,  output  voltages can run the load only when the  battery is fully charged (as indicated  by LED1).For  the partially  charged  battery, only 9V and 5V are available.

Also, no output is available when the voltage goes below 10.5V.  If battery  voltage  varies  between  10.5V  and  13V,  output  at  terminal A may  also vary  between  10.5V  and  12V, when the UPS system is in battery mode.

Outputs at points B and C provide 9V and 5V, respectively, through regulator  ICs  (IC1 and  IC2), while output A  provides  12V  through  the  zener diode. The emergency  lamp uses  two ultra-bright  white  LEDs  (LED2  and LED3) with  current  limiting  resistors R5 and R6. The lamp can be manually switched ‘on’ and ‘off’ by S1.

The circuit  is assembled on a general-purpose  PCB. There  is  adequate space  between  the  components  to avoid overlapping. heat sinks for transistor T2 and  regulator  ICs (7809 and 7805) to dissipate heat are used. The  positive  and  negative  rails  should  be  strong  enough  to  handle  high  current. Before  connecting  the  circuit to the battery and transformer,  connect it to a variable power supply.  Provide  12V  DC  and  adjust  VR1  till  LED1  glows. After  setting  the  high  voltage  level,  reduce  the  voltage  to  10.5V  and  adjust  VR2  till  the  output  trips  off.  After  the  settings  are  complete, remove the variable power supply and connect a fully-charged battery  to  the  terminals and  see  that LED1  is  on. After making  all  the  adjustments  connect  the  circuit  to  the battery  and  transformer. The battery used in  the  circuit is a 12V, 4.5Ah UPS battery. 

Parts List :

Resistor :

R1= 68 ohm

R2= 1k

R3= 1k

R4=47 ohm

R5= 390 ohm

R6= 390 ohm

Variable Resistor:

VR1= 10k

VR2= 22k

Diode:

D1= 1N4007

D2=1N4007

D3=1N4007

D4= 1N4007

Zener Diode :

ZD1= 10.5V, 0.5W

ZD2= 12V, 1W

LED:

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LED1= Red light (normal)

LED2= White

LED3= White

Capacitor:

C1= 470µF ,

Transistor :

T1=BC548

T2= TIP127

IC :

IC1= 7809

IC2=7805

Transformer = 230V AC 50Hz Output 12V, 1A

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DC to DC Converter-6V to 12V Convert

This is a inverter circuit diagram. This circuit can provide up to 800mA of 12V power from a 6V supply. For example, If you could run 12V car accessories in a 6V car. The circuit is simple, about 75% efficient and quite useful. By changing just a few components, you can also modify it for different voltages.

Component : 

Part	Total Qty.	Description	Substitutions
R1, R4	2	2.2K 1/4W Resistor
R2, R3	2	4.7K 1/4W Resistor
R5	1	1K 1/4W Resistor
R6	1	1.5K 1/4W Resistor
R7	1	33K 1/4W Resistor
R8	1	10K 1/4W Resistor
C1,C2	2	0.1uF Ceramic Disc Capacitor
C3	1	470uF 25V Electrolytic Capcitor
D1	1	1N914 Diode
D2	1	1N4004 Diode
D3	1	12V 400mW Zener Diode
Q1, Q2, Q4	3	BC547 NPN Transistor
Q3	1	BD679 NPN Transistor
L1	1	See Notes
MISC	1	Heatsink For Q3, Binding Posts (For Input/Output), Wire, Board

Notes

1. L1 is a custom inductor wound with about 80 turns of 0.5mm magnet wire around a toroidal core with a 40mm outside diameter.

2. Different values of D3 can be used to get different output voltages from about 0.6V to around 30V. Note that at higher voltages the circuit might not perform as well and may not produce as much current. You may also need to use a larger C3 for higher voltages and/or higher currents.

3. You can use a larger value for C3 to provide better filtering.

4. The circuit will require about 2A from the 6V supply to provide the full 800mA at 12V. 

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