Transformerless Power Supply

Parts List-
C1 - 1 - 0.39uF 250V Capacitor
C2 - 1 - 220uF 25V Electrolytic Capacitor
D1 - 1 - 1N4741 11V Zener Diode (See Notes)
BR1 - 1 - 1 Amp 200V Bridge Rectifier
MISC - 1 - Line Cord, Board, Wire, Case

Notes-
1. The value of C1 can be increased to increase the amount of current the circuit can supply. With the values shown, the circuit can supply up to about 15mA. Remember to increase the size of C2 also.

2. <>A different value can be used for D1 to increase or decrease the voltage as needed.

3. Please note that this circuit is not isolated from 120VAC. Because of this, the circuit must be treated with caution and encosed at all times. Do not work on the circuit (or any other circuits attached to it) when it is plugged in.

4. You may want to add a resisor in series with C1 to limit current if the circuit is plugged in and the mains is at its full voltage.

5. If you are running the circuit from 220VAC, then use a capacitor rated at greater than 400V for C1.

6. If you want isolation from the AC line, you can connect up a small isolation transformer at the inputs of the circuit. Small 600ohm:600ohm audio transformers work nicely.

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Fixed Voltage Power Supply

Parts List-
C1 - 1 - 2200uF 35V Electrolytic Capacitor
C2, C4 - 2 - 0.1uF Ceramic Disc Capacitor
C3 - 1 - 10uF 35V Electrolytic Capacitor
D1, D2 - 2 - 1N4007 Silicon Diode
BR1 - 1 - 2A 30V Bridge Rectifier
U1 - 1 - Regulator (See Notes)
T1 - 1 - Transformer (See Notes)
S1 - 1 - SPST 2 Amp Switch
F1 - 1 - 2A 250V Fuse and Holder
MISC - 1 - Heatsink For U1, Line Cord, Case, Wire

Notes-
1. Since this project operates from 120 (or 220, or 240, etc.) volts AC, it MUST be built inside a case.

2. U1 will reauire a heatsink.

3. You will need to choose T1 and U1 to match the voltage you want. Use the table below as a reference.

Output Voltage

T1U1
5V 6V, 1.5A 7805
6V 6V, 1.5A 7806
9V 12V, 1.5A 7809
12V 12V, 1.5A 7812
15V 24V, 1.5A 7815
18V 24V, 1.5A 7818

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Laser Power Supply

Parts List-
R1 - 1 - 10 Ohm 10W Or Greater Resistor
R2 - 1 - Ballast Resistor, See "Notes"
D1, D2, D3 - 3 - 1N4007 Silicon Diode
C1, C2, C3 - 3 - 0.1 uF 2000V Capacitor
T1 - 1 - 9V 1A Transformer
S1 - 1 - 115V 2A SPST Switch
MISC - 1 - Case, Wire, Binding Posts (for output), Line Cord

Notes-
1. T1 is an ordinary 9V 1A transformer connected backwards for step up.

2. R1 MUST be installed on a LARGE heatsink. A good heatsink is the metal case the supply is built in.

3. R2 Protects the laser tube from excess current. It should be soldered directly to the anode terminal on the tube. To find R2, start with a 500K 10W resistor and work down until the tube lights and remains stable.

4. If you have trouble with the tube not starting easily, use a longer anode lead that is wrapped around the tube.

5. Depending on the transformer you use, the circuit may or may not work. I cannot guarantee the operation of this circuit. Build at your own risk. Some transformers contain very few secondary windings which will quickly saturate the core and basically act like a direct short. The more secondary windings (that is, primary in this circuit) the better.

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6V to 12V dc-dc boost converter by 555 timer

This 6V to 12V dc-dc boost converter can drive a load in 12V about 3A current.The 555 timer IC is operated in astable mode, generates about 29Khz frequency of about 54% duty cycle drives the input of TIP41C transistor.1000uF capacitor smoothens the output voltage of the dc-dc converter.LED and 1.5Kohm resistor serves as indicator and load for output stability when no load is connected.You can add a 12V zener diode (1N5242B)across output to ground for further output stability.

The 39ohm resistor at the base of transistor is rated 1W, the rest 1/4W or more.Inductor can be made out of #22AWG wire wound around on an old transistor radio ferrite core.Number of turns more than 30T, but not critical.Change the values and experiment more using this circuit.

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12V to 5V DC converter using 7805 regulator IC

This simple converter project uses 7805 IC to convert 12V dc from a battery to 5V DC. This converter also can be made even only one component, the 7805 regulator. Converter can produce a maximum current of 1.5A (with heatsink) at 5V from an input of 8V to 15V. The capacitors are optional and can be omitted.
This is suitable for powering devices that uses 5V DC such as chargers,USB devices and others

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Dual Polarity Power Supply Circuit

When working with electronics, you always need one basic thing; power. This power supply is great for powering all kinds of electronic projects. It produces a well filtered, variable 1.2-30 volts at 5 amps. It is easy to build and the parts are realitively easy to find.

Schematic-

Parts List-
C1 - 1 - 14000uF or 10000uf 40 VDC Electrolytic Capacitor
C2 - 1 - 100uF 50Vdc Electrolytic Capacitor
C3 - 1 - 0.1uF Disc Capacitor
C4 - 1 - 0.01uF Disc Capacitor
R1 - 1 - 5K Pot
R2 - 1 - 240 Ohm 1/4 W Resistor(See Notes)
U1 - 1 - LM338K 1.2 to 30 Volt 5 Amp Regulator
BR1 - 1 - 10 Amp 50 PIV Bridge Rectifier
T1 - 1 - 24 V 5 Amp Transformer
S1 - 1 - SPST Toggle Switch
MISC - 1 - Wire, Line Cord, Case, Binding Posts (for output)

Notes-
1) The regulator comes in a TO-3 case and MUST be used with a LARGE heatsink. You may want to mount a small fan to blow air across the regulator (I did).

2) The filter capacitor is large. It won't fit on any board so bolt it to the case.

3) You can, of course, add a volt and amp meter.

4) Since this project operates from 120 VAC, you must include a fuse and build the project in a case.

5) R2 may need to be decreased to 120 Ohm if you experience voltage drift at light loads. 240 Ohm may not load the output appropriately on some regulators. The datasheet for the LM338K does specify 120 Ohm (I suggest you use a 1/2W unit) so you may just want to use 120 Ohm and not bother with the 240 Ohm resistor showin the parts list.

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Portable CD Player Adapter For Car Circuit

Whenever I'm in the car listening to my favourite CD, it always happens; my batteries go dead. To solve that problem, I built this extremely simple regulator circuit. It steps down the 12V from the lighter socket to 9V which is used by the CD player. Different CD players (I have a Sony Discman) may require different voltages, so just use the correct regulator. All the 78xx series regulators have the same pin out, so the circuit is universal.

Schematic-

Parts List-
C1 - 1 - 1000uF 25V Electrolytic Capacitor
C2 - 1 - 10uF 25V Electrolytic Capacitor
C3 - 1 - 1uF 15V Elextrolytic Capacitor
C4 - 1 - 0.1uF 15V Electrolytic Capacitor
U1 - 1 - 7809 Or Other Regulator (See "Notes")
MISC - 1 - Cigarette Lighter Plug, Plug For CD Player (See "Notes"), Heat Sink For U1, Wire, Case.

Notes-
1) The voltage your CD player needs will determine which regulator you use. For 9V, use the 7809. For 6V, use the 7806. For the unlikely 5V use the 7805. Remember that whatever regulator you use, you will need to heat sink it. The metal case or metal cover on the case makes a great heat sink.

2) I built the circuit in a small case with the long wire to the cigaratte lighter plug coming out one end, then another, slightly shorter wire going out the other end to the CD player.

3) Triple check your wiring. You would hate to ruin an expensive CD player because you reversed one of the connections or hooked the regulator up backwards.

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Dual Polarity Power Supply Circuit

This dual polarity power supply is easy to build, requires few parts, and is adjustable from 0-15 volts. It is great for powering op amp circuits, as well as other circuits that require a dual supply voltage.

Schematic-

Parts List-
C1, C2 - 2 - 2200uF 35V Electrolytic Capacitor
C3, C4, C5, C7 - 4 - 1uF 35V Electrolytic Capacitor
C6, C8 - 2 - 100uF 35V Electrolytic Capacitor
R1, R4 - 2 - 5K Pot
R2, R3 - 2 - 240 Ohm 1/4 W Resistor
BR1 - 1 - 2A 30V Bridge Rectifier
U1 - 1 - LM317 Adjustable Positive Regulator
U2 - 1 - LM337 Adjustable Negative Regulator
T1 - 1 - 30V Center Tapped 2 Amp Transformer
S1 - 1 - SPST 2 Amp Switch
MISC - 1 - Heatsinks For U1 And U2, Line Cord, Case, Knobs For Pots, Wire

Notes-
1) Since this project operates from 120 (or 220, or 240, etc.) volts AC, it MUST be built inside a case.

2) U1 and U2 get quite hot and will require heatsinks. A fan is usually not needed.

3) You can, of course, add a volt and amp meter.

4) U1 and U2 can only go down to a minimum of +-1.2V. If you need to go lower, you can add two 1N4003 diodes in series with the output of the regulator. The diodes drop about 0.6V each, which will allow the supply to go to 0. Note that this will also decrease your maximum output voltage by 1.2V. (Thanks to Steve Horvath for the suggestion).

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