Neon Flasher Runs From 3V Supply

A neon indicator typically requires at least 70V to fire it and normally would not be contemplated in a battery circuit. However, this little switchmode circuit from the Linear Technology website (www.linear-tech.com) steps up the 3V battery supply to around 95V or so, to drive a neon with ease. The circuit has two parts: IC1 operating as step-up converter at around 75kHz and a diode pump, consisting of three 1N4148 diodes and associated .022µF capacitors. The 3.3MO resistor and the 0.68µF capacitor set the flashing rate to about once every two seconds. The average DC level from the diode pump is set to about 95V by the 100MO feedback resistor to pin 8. The circuit could also use an LT1111 (RS Components Cat 217-0448) which would run at about 20kHz so L1 could be reduced to 100mH and use a powdered iron toroid core from Neosid or Jaycar.

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Battery Replacement Power Supply

Your childs battery toy has failed and you have to fix it. Once you have managed to get it apart, the battery compartment is not likely to be connected to the works or the batteries might have gone flat anyway. The solution is this switchable supply which is designed to replace from one to six dry cells. It is not intended to replace the batteries on a permanent basis, as in most cases this is not practical. The heart of the supply is an LM317T adjustable 3-terminal regulator and six trimpots selected by switch S1b. The other pole of the switch, S1a, is used to select taps on the transformer secondary, to minimize power dissipation in the LM317T. The table shows the trimpot settings for the six voltage outputs. Diode D1 and the 10µF capacitor and the LED provide power indication. This has the advantage of constant brightness which would not be obtained if the LED was run from the unregulated switchable DC.

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Self switching Power Supply

This is so useful circuit for you all. because this circuit switches itself off when no load is connected across its output terminals so you can prevent from over lording and form lots of electrical problems.According to the out put of IC 7805 you can get the voltage that you want..Maximum voltage is 12v (250MA).

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Troubleshooting STR IC Regulator Power Supply

A. Unable to start.

Can be caused by:

• No start-up voltage supply Vcc or a voltage less than 16V
• Electrolityc Capacitors supply voltage Vcc filter dry.

  

2. Led indicator blinking

If the supply voltage Vcc examined rocking. This is because the regulator of life and death because OVLO work., Die-protectionist regulators and auto start life over and over. If it is turned off Electrolityc Capacitors  usually still keep the rest of the cargo.

Can be caused by:

• Electrolityc Capacitors supply voltage Vcc filter on a pin-4 dry. Replace with a value equal to or slightly larger. - triger UVLO
• input filter capacitor on pin-1 feed dry behind the declining value - triger OLP
• Rectifier diode of the switching transformer is damaged (sometimes when examined with avo-meter looks like a still good)
• cause the supply voltage Vcc drops of the switching transformer (UVLO)
• Part damage or broken lines on the feedback circuit of the voltage regulator through B to photocoupler - triger OVP
• Electrolityc Capacitors dry filter voltage B - triger OVP
• One of the output voltage of the switching transformer secondaries there is a short (over load) - triger OLP
• Soft start capacitor value decreases - triger OLP

3. Noise arising (noise)

Can be caused by:

• Transformer windings slack.
• If there are ceramic capacitors - can sometimes cause interference noise due to its characteristic piezoelectrik like crystal resonator. Replace with film capacitors.

4. When the st-by normal stress. But when the power is on the regulator directly off protectionism no voltage on the secondary this part. Electrolityc Capacitors  are still storing charge.

Can be caused by:

• Sensor OVP small value resistor on pin-2 to the ground so that the value of delayed triger to OLP or OCP.
• Regulator IC is damaged

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Note: Be careful when the regulator is not working. Because of Electrolityc Capacitors  may still have a charge when turned off.

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