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HP 7540 17 inch CRT monitor Circuit Daigram

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Used ICs -  STR-G5643D – NT6865UG – STV9118 – LM1246 – LM 1248 – M1237BDKE - LM2470TA – STV9302A – 79A774-1 [LOT] – 2SC5929 [HOT Transistor] Maintain interconnecting ground lead connections between chassis and picture tube dag when operating chassis.  Certain HV failures can increase X-ray radiation. Monitor should not be operated with HV levels exceeding the specified rating for the chassis type. The maximum operating HV specified for the chassis used in this monitor is 24.8KV ± 1KV  with a line voltage of 120/240 VAC. Higher voltage may also increase possibility of failure in HV supply. It is important to maintain specified values of all components in the horizontal and high voltage circuits and anywhere else in the monitor that could cause a rise in high voltage or operating supply voltages. No changes should be made to the original design of the monitor. Components shown in the shaded areas on the schematic should be replaced with exact factory replacement parts. The ...

Simple Security Monitor

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A remote listening circuit. The area to be monitored is connected via a cable and allows remote audio listening. Simple Security Monitor Circuit Diagram: Notes: You can use this in your garden and listen for any unusual sounds, or maybe just wildlife noises. If you have a car parked in a remote location, the microphone will also pick up any sounds od activity in this area. The cable may be visible or hidden, screened cable is not necessary and you can use bellwire or speaker cable if desired. Circuit Description: Starting from the right hand side, the power supply. I have used 12V as a standard power supply voltage, or a 12V car battery may be used. The circuit is in two halves, a remote microphone preamp, and an audio amplifier based around the National Semiconductor LM386 audio amplifier. The remote preamp uses an ECM microphone to monitor sound. A direct coupled 2 stage amplifier built around Q1 and Q2 amplify the weak microphone signal. Preset resistor R2 acts as a gain control, an...

Voltage Monitor Circuit Diagram

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This is the project of Voltage Monitor Circuit Diagram. This is a very simple circuit which can be modified to the user's needs. Its operation is simple, when the input voltage is 0, the LED (LO). The LED turns off when the voltage increases to the level determined by R2. Voltage Monitor Circuit Diagram

LM3914 Based Battery Voltage Monitor

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This voltage monitor is made to display the voltage of 12v battery (for UPS) on LEDs. For this purpose LM3914 is used. The voltage range decided to display is 10v to 13.5v for 12v battery. LM3914 is display driver that can be used in dot  mode or in bar mode; dot mode , with only one led is lit at a time, and in bar mode where it lights leds progressively when the voltage increases. The circuit needs to be powered from the battery being measured and to be able to adjust the lower and upper voltages that light the first and last leds on the led bar. For the 12V battery, the first led in the bar will lit at 10V and the last one at 13.5V , giving 0.35V per led. These thresholds may be set to other values by adjusting two trimmers in the circuit. Calculation and Adjustments: Current flowing per led is controlled by R3 resistor, by applying ohm's law  Ir3 =1.25v/ 4.7kohm =266uA.  Where 1.25v is the minimum voltage required to operate the led. To be able to read the supply vo...

Wireless Baby Monitor

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Walkie-talkies (also known as handheld or PMR, Personal Mobile Radio) can be bought at low prices even from department stores, and they can be operated without a licence in many countries. Considering the low cost, such a set would be very suitable for use as a wireless baby monitor, with the addition of several external components. These are connected to the jack sockets for an external loudspeaker/microphone and an external PTT (Push-To-Talk) switch, which are often found on these devices.  Wireless Baby Monitor Project Image The walkie-talkie with the extra electronics and microphone is placed in the baby’s room. When the PTT switch on the other walkie-talkie is actuated for about a second the ‘baby’ walkie-talkie produces a series of tones, which the external electronics can detect. This then activates its own PTT switch for about 5 seconds, so it switches over to transmit. During this time the other device can hear what the external microphone picks up.  Figure 1- Wirel...

Temperature Monitor Circuit Diagram

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A simple op-amp circuit that will trigger a relay when a preset temperature is reached. Please note that there is no hysteresis in this circuit, so that if the temperature changes rapidly, then the relay may switch rapidly. Temperature Monitor Circuit Diagram Circuit Notes : This circuit uses an ordinary NTC thermistor with a resistance of 47k at room temperature. A suitable part from Maplin Electronics is FX42V. The circuit is set in balance by adjusting the the 47k potentiometer. Any change in temperature will alter the balance of the circuit, the output of the op-amp will change and energize the relay. Swapping the position of the thermistor and 47k resistor makes a cold or frost alarm. Calibration : At room temperature (25 degrees Celsius) a 47k NTC thermistor resistance is approximately 47k. The non-inverting op-amp input will then be roughly half the supply voltage, adjusting the 47k pot should allow the relay to close or remain open. To calibrate the device, the thermistor idea...

Mains Frequency Monitor Circuit Diagram

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Here is a simple frequency counter designed to monitor the 240VAC mains supply. It as a frequency range of 0-999Hz, so it could also be used with 400Hz equipment. Standard TTL/CMOS logic is employed for the counters and display drivers, while an ELM446 (IC1) generates accurate 1Hz pulses for gating. This device utilizes a 3.579545MHz crystal for its timebase, as commonly found in TV and video circuits and even on old PC motherboards. Mains Frequency Monitor  Circuit diagram: Mains Frequency Monitor Circuit Diagram Source by : Streampowers

Simple Mains Frequency Monitor Circuit Project

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Project of Mains Frequency Monitor Circuit Diagram. Here is a simple frequency counter designed to monitor the 240VAC mains supply. It as a frequency range of 0-999Hz, so it could also be used with 400Hz equipment. Standard TTL/CMOS logic is employed for the counters and display drivers, while an ELM446 (IC1) generates accurate 1Hz pulses for gating. This device utilizes a 3.579545MHz crystal for its timebase, as commonly found in TV and video circuits and even on old PC motherboards. Mains Frequency Monitor Circuit Diagram : Mains Frequency Monitor Circuit Diagram Copyright: Silicon Chip Electronics Magazine

Motorcycle Battery Monitor

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A circuit for monitoring the status of the battery and generator is undoubtedly a good idea for motorcyclists, as for other motorists. However, not every biker is willing to drill the necessary holes in the cockpit for the usual LED lamps, or to screw on an analogue accessory instrument. The circuit shown here manages to do its job with a single 5-mm LED, which can indicate a total of six different conditions of the onboard electrical system. This is done using a dual LED that can be operated in pulsed or continuous mode (even in daylight). Built on a small piece of prototyping board and fitted in a mini-enclosure, the complete circuit can be tucked inside the headlamp housing or hidden underneath the tank. The heart of the circuit is IC2, a dual comparator. The comparator circuit is built without using any feedback resistors, with the indication being stabilised by capacitors C4 and C5 instead of hysteresis. Small 10-µF tantalum capacitors work well here; 220-µF ‘standard’ electrolyti...