Secret Diagram: Protector

Showing posts with label Protector. Show all posts

Tuesday, 21 March 2017

Loudspeaker Protector Monitors Current

This circuit uses a 0.1O 1W resistor connected in series with the output of a power amplifier. When the amplifier is delivering 100W into an 8O load, the resistor will be dissipating 1.25W. The resulting temperature rise is sensed by a thermistor which is thermally bonded to the resistor. The thermistor is connected in series with a resistor string which is monitored by the non-inverting (+) inputs of four comparators in an LM339 quad comparator. All of the comparator inverting inputs are connected to an adjustable threshold voltage provided by trimpot VR1. As the thermistor heats up, its resistance increases, raising the voltage along the resistor ladder.

Loudspeaker Protector Monitors Current Circuit diagram:

Loudspeaker Protector Circuit Diagram

When the voltage on the non-inverting input of each comparator exceeds the voltage at its inverting input, the output switches high and illuminates the relevant LED. NOR gate latches are connected to the outputs of the third and fourth comparators. When the third comparator switches high, the first latch is set, turning on Q1 and relay 1. This switches in an attenuation network (resistors RA & RB) to reduce the power level. However, if the power level is still excessive, comparator 4 will switch, setting its latch and turning on Q2 and relay 2.

This disconnects the loudspeaker load. The thermistor then needs to cool down before normal operation will be restored. The values of R1-R4 depend on the thermistor used. For example, if a thermistor with a resistance of 1.5kO at 25°C is used, then R1 could be around 1.5kO and R2, R3 and R4 would each be 100O (depending the temperature coefficient of the thermistor). The setup procedure involves connecting a sinewave oscillator to the input of the power amplifier and using a dummy load for the output. Set the power level desired and adjust trimpot VR1 to light LED1. Then increase the power to check that the other LEDs light at satisfactory levels.

Author: David Devers - Copyright: Silicon Chip Electronics

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Tuesday, 7 March 2017

Simple Source Voltage Protector

Protection of electronic devices with a DC voltage source of voltage source obligatory reversal, especially protection of the source voltage is reversed. The definition of "Protectors Voltage Sources" in this article are the source voltage surge protector circuit which serves to protect the device from the reversal of the voltage source to the appliance electronics.

Source voltage surge protector will expressed in this article are general, so that later in their applications to stay adjusted value of the component with the voltage source needs an electronic appliance. Let us start reviewing Protectors Voltage Source by simple and modest.

Source voltage protection with 1 diode

Diodes are used as a protector of the source voltage installation tebaliknya voltage source is installed in series with the input line voltage source electronics devices. Installation of surge protector diode as a voltage source is on the positive line voltage source input device. The function is to drain diode current (voltage source) in one direction only, so that in the event of an upside-down voltage source. then the voltage source is not in the channel (in blocks) to the device. The value of the diode is tailored to the needs of the source voltage of the device itself.

Source voltage protection with dioda bridge

Protectors voltage source with a diode bridge in principle the same as the surge protector with a voltage source diode 1 pc. The difference is the source voltage surge protector is not blocking the source voltage, but the source voltage surge protector is to reverse the flow of the source voltage of one polarity in the case of voltage source. From the picture above to explain the purpose of reversing the voltage source in question, namely when given a source voltage through a voltage surge protector is the source of positive polarity (+) will be directly in the stream leading to the positive input line of tools and the source of negative voltage (-) will be directed to the negative voltage source input line tool.

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Saturday, 14 January 2017

High temperature protector with IC 3584

IC 3584 has thermal protection or voltage automatically shutdown when the temperature at IC exceed 150 degrees or more. You can operate this circuit at the transistor or IC heatsing, if a transistor or IC had exceeded the limit of the heat circuit automatically shutdown.

How to use a thermal shutdown circuit above that is first given a circuit of voltage V+,V-,and ground , the given a voltage Vin to be created automatically shutdown if the temperature is high , and the output is inserted in the circuit of an amplifier or other. Then IC embedded in the heatsing or case, which if too hot will shutdown alone. If the circuit already decided voltage, the voltage will re-connect if the temperature returns to normal.

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Saturday, 7 January 2017

Lead Acid Battery Protector Circuit Diagram

The circuit described here can be used to ensure that a 12 V sealed lead acid (SLA) gel battery isn’t discharged too deeply. The principal part of the circuit is a bistable relay, which is driven by the output of an op amp.

The battery voltage is first reduced via D1, R1, P1 and R2, and then continuously compared with a reference voltage set up by diode D2. When the battery discharges too much and its terminal voltage drops below the level set by P1, the output of the opamp becomes High, which causes the relay to toggle. This in turn isolates the load from the battery. The battery can be reconnected via S1 once the battery has been replaced or recharged.

The relay used in the prototype is a 5 V bistable type made by Omron (G6AK-234P-ST-US 5 VDC). The two windings of the relay each have a resistance of 139 Ω (for the RAL-D 5 W-K made by Fujitsu this is 167 Ω). When the battery voltage starts to become too low and the relay is being reset the current consumption of the circuit is about 45 mA. Shortly after the load has been disconnected, when the battery voltage rises above the reference voltage again, the reset coil will no longer be powered and the current consumption drops back to about 2.5 mA.

Lead Acid Battery Protector Circuit Diagram

The range of P1 has intentionally been kept small. With a reference voltage of 5.6 V (D2) and a voltage drop of 0.64 V across D1, the circuit reacts within a voltage span of 11.5 V and 11.8 V. This range is obviously dependent on the zener diode used and the tolerance.

For a greater span you can use a larger value for P1 without any problems. With the potentiometer at its mid setting the circuit switches at about 11.6 V.

Author : Jürgen Stannieder

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Sunday, 20 November 2016

Build an AC Mains Short Circuit Protector Circuit Diagram

The simple short circuit and overload protector design presented here can be used for protecting valuable mains operated gadgets like amplifiers, TV sets, DVD players or any other similar appliance.Normally all sophisticated gadgets today incorporate an in built short circuit protector arrangement, yet still adding a more comprehensive external protection device could only benefit the connected system.

Moreover, for gadgets such as amplifiers which are home built this protection device could prove to be very effective and useful. Also for an hobbyist who prefers building electronic gadgets at home could be greatly benefited with the present idea.

The presented short circuit protector design works on a very basic principle and costs not more than a couple of dollars.

Let's learn the functioning details of the proposed circuit.

On applying power, the high current from the 220V input is dropped sufficiently by C1, rectified by D1 and filtered by C2 to feed the gate of the triac T1.

The triac conducts and switches ON the connected transformer primary thus switching ON the load which in this case is a power amplifier.

The transistor Q1 along with R1, R2 forms a current sensor stage.

R2 specifically is chosen such that it develops adequate voltage across itself at the specified dangerous high current threshold.

As usual the formula for determining R2 = 0.6/current(A)

As soon as the triggering voltage accumulates across R2, Q1 activates and sinks the gate voltage of the triac to ground making it switch off.

The regulation continues as long as the short or overload condition is not removed.

The above short circuit regulation ensures that the current level above the specified dangerous level is restricted safeguarding the precious devices associated with the connected amplifier.

If a latching feature is required for the above design, the emitter Q1 can be configured with an SCR and the SCR can be used for latching and switching off the triac.

AC Mains Short-Circuit Protector Circuit Diagram

Parts List

R1 = 100 ohms
R2 = see text
R3 = 1k
R4 = 10k
C1 = 0.33/400V
C2 = 1uf/250V
Q1 = BC547
Z1 = 12V/1 watt zener diode
T1 = BT136 or as per current rating
TR1 = As per load requirement specs.

Source By Swagatam

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