Electromagnetic Sensor Circuit Using 741 IC

This is a design schematic to sensor the electromagnetic field. This circuit is based or built by 741 IC. This IC is an op-amp. The circuit can detect the field even hidden wrings. This is the figure of the schematic.


A 1mH inductor is used for sensing the electric field. The electric field will induce a small voltage in the sensor inductor and this induced voltage is amplified by the op amp. The headphone connect at the output of the op amp will give an audio indication of the electric field. For example, the electric field around a main transformer can be heard as a 50 Hz hum. The POT R4 can be used to adjust the gain of the amplifier. By keeping the sensor inductor near to a telephone line, you can even hear the telephone conversations. All electrolytic capacitors must be rated at least 15V. The switch S1 can be a slide type ON/OFF switch. The POT R4 can be used to adjust the gain. It is better to have a radial type inductor for L1.

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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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