Published:2009/6/24 3:51:00 Author:May
The temperature sensor/controller (the TMP-01) is a monolithic device whose low power allows it to operate with a simple half-wave rectified power supply directly from the ac line. Such an ar-rangement greatly simplifies the power-supply design requirement to the point of only needing a few low-cost components to provide a single +6-Vdc supply.The TMP-01 is essentially a therrrtostat on a chip. It includes a linear temperature sensor (5 mV/K), and also has two comparators that switch at externally determined set points. These set points are established by resistively dividing the internal 2.5-V reference to set appropriate voltages on the inputs to the comparators.One comparator is used in this circuit to turn on the heating element when the temperature drops below 30℃; it corresponds to a voltage of 1.52V on the comparator's input. (View)
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Published:2009/6/24 4:07:00 Author:Jessie
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Published:2009/6/24 3:51:00 Author:May
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Published:2009/6/24 3:50:00 Author:May
This recelver covers the 118-to 136-MHz AM aviation band It has a 10 7-MHz IF amplifier. L1,L3,and L5 are 1 1/2 turns of#24wire FIL1 is a 10 7-MHz ceramic filter.IF bandwidth will be about 250 kHz. (View)
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Published:2009/6/24 4:07:00 Author:Jessie
Most car door switches are simply single-pole switches, with one side grounded. When the door is opened the switch grounds the other line thus completing the light circuit. In a car where the negative terminal of the battery is connected to the chassis, the,.g,J tive wire of the unit (emitter of Q2) is con-nected to chassis the positive wire (case of 2N3055) is connected to the wire going to the switch. 1n a car having a positive ground sys-tem this connection sequenge is reversed. When the switch closes (door open), C1 is discharged via D1 to zero volts, and when the switch opens, g| charges up via R1 and R2.Transistors Q1 and Q2 are connected as an emitter follower (Q2 just buffers Q1) therefore the voltage across Q2 increases slowly as Ci charges. Hence Q2 acts like a low resistance in parallel with the switch and keeps the lights on.The value of C1 is chosen such that a usetui light level is obtained for about four seconds; therefore the light decreases until in about 10 seconds it is out completely. With different transistor gains and with variation in current drain due to a particular type of car, the timing may vary but may be simply adjusted by selecting C1. (View)
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Published:2009/6/24 3:49:00 Author:May
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Published:2009/6/24 4:06:00 Author:Jessie
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Published:2009/6/24 3:49:00 Author:May
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Published:2009/6/24 4:05:00 Author:Jessie
Local oscillator circuits for the NE602. (View)
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Published:2009/6/24 3:49:00 Author:May
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Published:2009/6/24 4:05:00 Author:Jessie
A circuit for use with grounded thermocouples is shown. To trim, short out the LM329B and ad-just R5 so that V°= αT, where cc is the Seebeck coefficient of the thermocouple and T is the absolute temperature. Remove the short and adjust R4 so that W equals the thermocouple output voltage at ambient. A good grounding system is essential here, for any ground differential will appear in series with the thermocouple output. (View)
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Published:2009/6/24 4:04:00 Author:Jessie
IC1 is connected in the astable mode, driving RLA. C3, Dl, and D2 prevent spikes from the relay coil and the wiper motor from triggering IC1. VR2 is adjusted to give the minimum delay time required. VR1 is the main delay control and provides a range of from about 1 second to 20 seconds. SW1 is an over-ride switch to hold RLA permanently on (for normal wiper operation). The relay should have a resistance of at least 150 ohms and have heavy duty contacts. The suppression circuit may be needed for the protection of IC1. (View)
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Published:2009/6/24 4:03:00 Author:Jessie
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Published:2009/6/24 4:03:00 Author:Jessie
The actual processing circuitry of this A/D converter consists of only four parts: U2, U3, R1 and R2. Eight temperature probes are used with the circuit; however, they can be replaced with other types of sensors, as long as resistors R3 through R10 are removed.
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Published:2009/6/24 4:03:00 Author:Jessie
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Published:2009/6/24 3:55:00 Author:Jessie
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Published:2009/6/24 3:55:00 Author:Jessie
Use of two LDR devices replaces the two vide light sources for the LDR devices. (View)
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Published:2009/6/24 3:54:00 Author:Jessie
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Published:2009/6/24 3:51:00 Author:Jessie
A circuit for isolating a variable resistor is shown. An optoisolator that has an LED and a photo-conductive cell (or photoresistor) is used. The current through the LED controls its brightness, which in turn determines the resistance between terminals A and B. The LED current is set by the voltage of the dc power supply and the value of the two resistors (R1 and R2). The fixed resistor (R1) is used to limit the current to a maximum of 20 mA (when the resistance of the potentiometer, R2, is set to zero ohms), otherwise, the LED might burn out. (View)
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Published:2009/6/24 3:52:00 Author:Jessie
This circuit is a TTL-to-TTL isolator circuit. The driver circuit is an open-collector TTL inverter (U1). When the input is high, then the output of the inverter is low. Thus, when the input is high, the output of U1 grounds the cathode end of the LED and causes the LED to turn on. (View)
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