Showing posts with label detector. Show all posts
Showing posts with label detector. Show all posts
Wednesday, November 12, 2014
Maximum Temperature Detector For Fan Controller
The fan controller circuit for the Titan 2000 and other AF heavy-duty power amplifiers, has an output that sets a voltage if the fan controller reaches the end of its range. Since the controller responds to temperature, this signal is seen by the amplifier protection circuitry as an over temperature indication. The disadvantage of this output is that the maximum voltage for the fans is not constant, but depends on the load (number of fans, defective fans) and the mains voltage. This variation is caused by the fact that the supply voltage for the output stage is taken directly from the filtered transformer voltage.![Maximum]()
If the fans should fail, for example, the maximum temperature limit would lie at a considerably higher level than the desired value. The accompanying circuit, which compares the magnitude of the fan voltage to a fixed reference value, has been developed to allow the maximum temperature to be reliably detected. This circuit is tailored for 12-V fans. The reference voltage is generated by the ‘micro power voltage reference’ D1 and the FET T1, which is wired as a current source. These components are powered directly from the applied fan voltage. The current source is set up to deliver approximately 50µA.
D1 can work with as little as 10µA. The supply voltage for the IC is decoupled by R10, C3 and C4, with D4 providing over voltage protection. A maximum supply voltage of 16 V is specified for the TLC271. This opamp works with a supply voltage as low as 3 V and can handle a common-mode voltage up to approximately 1.5 V less than the positive supply voltage. Accordingly, 1.2 V has been chosen for the reference voltage. The fan voltage is reduced to the level of the reference voltage by the voltage divider R2–R3–P1. The limits now lie at 11.2 V and 16.7V.
If you find these values too high, you can reduce R2 to 100 kΩ, which will shift the limits to 9.5 V and 14.2 V. The output of the voltage divider is well decoupled by C2. A relatively large time constant was selected here to prevent the circuit from reacting too quickly, and to hold the output active for a bit longer after the comparator switches states. A small amount of hysteresis (around 1 mV) is added by R4 and R5, to prevent instability when the comparator switches. D2 ensures that the magnitude of the hysteresis is independent of the supply voltage. Two outputs have been provided to make the circuit more versatile.
Output ‘R’ is intended to directly drive the LED of an optocoupler. In addition, transistor T2 is switched on by the output of the opamp via R7 and R8, so that a relay can be actuated or a protection circuit triggered using the ‘T’ output. The high-efficiency LED D3 indicates that IC1 has switched. It can be used as a new ‘maximum’ temperature’ indicator when this circuit is added to the fan controller. The circuit draws only 0.25 mA when the LED is out, and the measured no-load current consumption (with a 12.5V supply voltage) is 2.7 mA when the LED is on.Resistors:
Read More..
D1 can work with as little as 10µA. The supply voltage for the IC is decoupled by R10, C3 and C4, with D4 providing over voltage protection. A maximum supply voltage of 16 V is specified for the TLC271. This opamp works with a supply voltage as low as 3 V and can handle a common-mode voltage up to approximately 1.5 V less than the positive supply voltage. Accordingly, 1.2 V has been chosen for the reference voltage. The fan voltage is reduced to the level of the reference voltage by the voltage divider R2–R3–P1. The limits now lie at 11.2 V and 16.7V.
If you find these values too high, you can reduce R2 to 100 kΩ, which will shift the limits to 9.5 V and 14.2 V. The output of the voltage divider is well decoupled by C2. A relatively large time constant was selected here to prevent the circuit from reacting too quickly, and to hold the output active for a bit longer after the comparator switches states. A small amount of hysteresis (around 1 mV) is added by R4 and R5, to prevent instability when the comparator switches. D2 ensures that the magnitude of the hysteresis is independent of the supply voltage. Two outputs have been provided to make the circuit more versatile.
Output ‘R’ is intended to directly drive the LED of an optocoupler. In addition, transistor T2 is switched on by the output of the opamp via R7 and R8, so that a relay can be actuated or a protection circuit triggered using the ‘T’ output. The high-efficiency LED D3 indicates that IC1 has switched. It can be used as a new ‘maximum’ temperature’ indicator when this circuit is added to the fan controller. The circuit draws only 0.25 mA when the LED is out, and the measured no-load current consumption (with a 12.5V supply voltage) is 2.7 mA when the LED is on.Resistors:- R1 = 22kΩ
- R2 = 120kΩ
- R3 = 10kΩ
- R4,R6 = 1kΩ
- R5 = 1MΩ
- R7,R8 = 47kΩ
- R9 = 3kΩ9
- R10 = 100Ω
- P1 = 5kΩ preset
- C1,C3 = 100nF
- C2 = 100µF 25V radial
- C4 = 47µF 25V radial
- D1 = LM385-1.2
- D2 = BAT85
- D3 = high-efficiency-LED
- D4 = zener diode 16V/1W3
- T1 = BF245A
- T2 = BC547B
- IC1 = TLC271CP
- K1 = 2-way PCB terminal block, raster 5mm
- K2 = 3- way PCB terminal block, raster 5mm
Sunday, September 7, 2014
Cellular Phone calling Detector
This schema was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED.The device must be placed a few centimeters from the cellular phone, so its sensor coil L1 can detect the field emitted by the phone receiver during an incoming call.
Parts:
R1____________100K 1/4W Resistor R2______________3K9 1/4W Resistor R3______________1M 1/4W Resistor C1,C2_________100nF 63V Polyester Capacitors C3____________220µF 25V Electrolytic Capacitor D1______________LED Red 10mm. Ultra-bright (see Notes) D2___________1N5819 40V 1A Schottky-barrier Diode (see Notes) Q1____________BC547 45V 100mA NPN Transistor IC1____________7555 or TS555CN CMos Timer IC L1_____________Sensor coil (see Notes) B1_____________1.5V Battery (AA or AAA cell etc.) The signal detected by the sensor coil is amplified by transistor Q1 and drives the monostable input pin of IC1. The ICs output voltage is doubled by C2 & D2 in order to drive the high-efficiency ultra-bright LED at a suitable peak-voltage. Notes: * Stand-by current drawing is less than 200µA, therefore a power on/off switch is unnecessary. * Sensitivity of this schema depends on the sensor coil type. * L1 can be made by winding 130 to 150 turns of 0.2 mm. enameled wire on a 5 cm. diameter former (e.g. a can). Remove the coil from the former and wind it with insulating tape, thus obtaining a stand-alone coil. * A commercial 10mH miniature inductor, usually sold in the form of a tiny rectangular plastic box, can be used satisfactorily but with lower sensitivity. * IC1 must be a CMos type: only these devices can safely operate at 1.5V supply or less. * Any Schottky-barrier type diode can be used in place of the 1N5819: the BAT46 type is a very good choice.
Monday, August 25, 2014
Rain Detector Wiring diagram Schematic
This is a Rain detector alarm schema.You can keep the sensing part out of the house.If water drops fell on the sensing part the alarm will start to ring.so this is very useful schema for you.Here we have used common IC NE 555.Think and use this in different way..
Sunday, August 24, 2014
Low battery detector circuit
You feel confused to detect wether a battery is low or high, or you want to be notified if the battery and has expired , this circuit can detect if a battery has begun to decrease its strength. Circuit is based on LM4250 IC is able to detect if the battery runs out and will issue a notification signal.
Friday, August 15, 2014
Simple Cell Phone Detector Wiring diagram Schematic
This is a simple cell phone detector schema diagram, this is a pocket-size mobile transmission detector or sniffer can sense the presence of an activated mobile cellphone from a distance of one and-a-half meters. So it can be used to prevent use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for spying and unauthorized video transmission.
Simple Cell Phone Detector Circuit Diagram
Tuesday, August 12, 2014
Air flow detector circuit
If you have industry at that situation this would be so useful schema.we use this schema to knowe whether air is flowing or not.so you can use this one for your car also (recently we hope to introduce HHO technology so at that situation you can use this one to indicate the air flowing.
Subscribe to:
Posts (Atom)
