A circuit for monitoring supply voltages of ±5 V and ±12 V is readily constructed as shown in the diagram. It is appreciably simpler than the usual monitors that use comparators, and AND gates. The circuit is not intended to indicate the level of the inputs. In normal operation, transistors T1 and T3 must be seen as current sources. The drop across resistors R1 and R2 is 6.3 V (12 –5 –0.7). This means that the current is 6.3mA and this flows through diode D1 when all four voltages are present. However, if for instance, the –5 V line fails, transistor T3 remains on but the base-emitter junction of T2 is no longer biased, so that this transistor is cut off. When this happens, there is no current through D which then goes out.
Showing posts with label monitor. Show all posts
Showing posts with label monitor. Show all posts
Thursday, November 6, 2014
Saturday, October 4, 2014
Telephone line monitor Circuit Diagram
This chic little circuit lets you almanac your buzz conversations automatically. The accessory connects to the buzz line, your band recorders microphone input, and the recorders alien ascendancy jack. It senses the voltage in the buzz band and begins recording back the band drops to 5 volts or less.
Parts
R1 270K 1/4 W Resistor
R2 1.5K 1/4 W Resistor
R3 68K 1/4 W Resistor
R4 33K 1/4 W Resistor
C1 0.22uF 150 Volt Capacitor
Q1, Q2 2N4954 NPN Transistor
D1 1N645 Diode
MISC Wire, Plugs To Match Jacks On Recorder, Board, Phone Plug
Parts
R1 270K 1/4 W Resistor
R2 1.5K 1/4 W Resistor
R3 68K 1/4 W Resistor
R4 33K 1/4 W Resistor
C1 0.22uF 150 Volt Capacitor
Q1, Q2 2N4954 NPN Transistor
D1 1N645 Diode
MISC Wire, Plugs To Match Jacks On Recorder, Board, Phone Plug
Notes
1. The circuit can be placed anywhere on the phone line, even inside a phone.
2. Some countries or states require you to notify anyone you are talking to that the conversation is being recorded. Most recoders do this with a beep-beep. Also, you may have to get permission from the phone company before you connect anything to their lines.
Thursday, October 2, 2014
Low Battery Monitor Circuit Using SCR
The prototype of this device will be used in a hospital operating theatre in unijnction with battery operated medical equipment (powered by four pen-light cells).
A moving coil voltmeter was not appropriate as, in the designers’ experience, medical staff have difficulty in interpreting a voltmeter and sometimes find themselves half way through an` operation with exhausted batteries. Therefore, the requirements for the indicator were that: 1) the display be eye catching, easily understandable and provide a sense of urgency as · the battery approaches exhaustion; 2) provide adequate warning of battery failure (at least ‘l hour); 3) current consumption of the indicator be low in. relation to the main equipment; 4) preferably, be more rugged and cheaper than a moving coil meter. The design was based on a programmable unijunction transistor (PUT), because its threshold characteristics can be well defined, arranged to flash a light emitting diode (L.E.D.) indicator.
The circuit is shown in the figure. The PUT (Q1) is used in a relaxation oscillator circuit. As the voltage being monitored (Vm,,,,) falls, the voltage on the gate (Vg) falls whilst the anode voltage (V,) remains essentially constant. Oscillation commences when V, falls below V, by 0.6 volts. As Vm, falls further, Vg falls and the PUT triggers at lower values of Va. Thus the cycle time shortens and the frequency of flashing increases giving a sense of urgency as the battery approached exhaustion. Transistor O2 and C2 act as a pulse stretcher and amplifier to drive the L.E.D. display. In the prototype the trigger point can be adjusted from 4.5-5.5 volts and the current drain when V,,,,,,, is 6 volts is 1 mA (controlled primarily by R1). This is considered acceptable as the device being monitored draws 17 mA. All the requirements have been met. The components of this low battery monitor circuit are mounted on the printed circuit board of the main device.
A moving coil voltmeter was not appropriate as, in the designers’ experience, medical staff have difficulty in interpreting a voltmeter and sometimes find themselves half way through an` operation with exhausted batteries. Therefore, the requirements for the indicator were that: 1) the display be eye catching, easily understandable and provide a sense of urgency as · the battery approaches exhaustion; 2) provide adequate warning of battery failure (at least ‘l hour); 3) current consumption of the indicator be low in. relation to the main equipment; 4) preferably, be more rugged and cheaper than a moving coil meter. The design was based on a programmable unijunction transistor (PUT), because its threshold characteristics can be well defined, arranged to flash a light emitting diode (L.E.D.) indicator.
Tuesday, September 9, 2014
Simple Car Battery Voltage Monitor Circuit
A dual op amp is used as a comparator. The green LED on the board, until the voltage exceeds 11.5 volts. The red LED illuminates when the voltage falls below 11.9 volts to the schema. Therefore, in the 11.9 to 11.5 volts, both LEDs are on, producing a slightly yellow color. When the voltage falls below 11.5 V, the green LED, and now only the red LED flashes to indicate low voltage.
Parts List
R1=1K2R2-3-4=680R
R5=15K
R6=10K
R7-8-9-10=1K
IC1=LM324
D1=5V6 /0.5W Zener
D2-3-4-5=LED
RV1=10K trimmer
Is recommended that multi-shaper for V1 and V2. Muti-trimmer makes it much easier to trigger points to make as a less expensive single-turn trimmer. The trimmer can be completely eliminated if you have access to a range of 1% resistors and has had calculated carefully. You would also want to provide more accurate reference voltage as the common 78L05 regulator.
Saturday, September 6, 2014
Monitor voltage and 5VDC and 12VDC Wiring diagram Schematic
This schema is a voltage monitor which operates on fixed testes ± 5 VDC and ± 12 VDC, and is easily constructed as shown in Fig. It is considerably simpler than the normal display using comparators and AND gates. The schema is not intended to indicate the level of entries. If one of the testes fail, for example, -5 V line fails, the transistor Q3 remains on but the base-emitter junction of T2 is not, so that this transistor is cut off. When this happens, there is no current through D, which then turns off.
Monitor voltage + and - 5VDC + and - 12VDC Circuit Diagram
Saturday, August 16, 2014
A Car Battery Monitor
A close call on the road can really focus your mind on the importance of having a battery monitor in a car. I had been enjoying a pleasant week of travelling around the countryside at a leisurely pace and taking in the beautiful scenery each day. It wasnt until the final day, with the big rush to return home, that I had to drive at night.My home is deep in the country and on the road I was travelling the closest petrol station may be 80km away. I was travelling through an area that is full of open-cut coal mines and large heavily loaded semi-trailers constantly pound the roads, travelling at quite high speeds. It was around 8pm at night and everything was very dark no street lights or house lights anywhere.
Just as I was going up a hill, the lights began to dim and the engine coughed. A large semi-trailer loomed in the rear-vision mirror as I pushed the clutch in and tried to restart. My speed was falling rapidly and my lights were blacked out - I was like a sitting duck in the middle of the road, as the semi-trailer came rapidly bearing down on me. I just managed to pull the car off the road, as the semi-trailer came screaming past, missing me by inches! After calling for assistance from the NRMA, the problem was found to be a fault in the alternator, which was failing to charge the battery. The battery voltage had been falling under the heavy load of the lights and at the worst possible time, there was not sufficient power for the lights or the motor.
A Car Battery Monitor Circuit Diagram
After the initial shock wore off, I put on my thinking cap to come up with a PIC-based solution to the problem. What was really needed was a display and a buzzer, to get my attention should the voltage fall outside a specified range. So my design criteria was set, a series of LEDs could indicate the voltage and a buzzer would also be used to warn of problems.
Main Features:
- Visual indication of battery voltage
- Audible warning when voltage becomes low
- Screw terminals for easy connection
- Simple and easy to build
Circuit details:
The schema is based on PIC16F819 18-pin microcontroller which has an analog-to-digital (A/D) input to monitor the battery voltage and outputs capable of driving LEDs directly, to keep the component count down. There are seven LEDs in all, giving a good range of voltage indication. The topmost LED, LED1, comes on for voltages above 14V which will occur when the battery is fully charged. LED2 indicates for voltages between 13.5V and 14V while LED3 indicates between 13V and 13.5V. Normally, one of these LEDs will be on. LED4 covers 12.5V to 13V while LED5 covers 12V to 12.5V. LED6 covers from 11.5V to 12V while LED7 comes on for voltages below 11.5V. These two LEDs are backed up by the piezo chime which beeps for voltages between 11.5V and 12V and becomes more insistent for voltages below 11.5V.
That might seem fairly conservative. After all, most cars will start with no troubles, even though the battery voltage might be a touch below 12V, wont they? Well, no. Some modern cars will happily crank the motor at voltages below 11V but their engine management will not let the motor start unless the voltage is above 11V. So dont think that a modern car will always start reliably. This little battery monitor could easily prevent a very inconvenient failure to start! So lets describe the rest of the schema. The incoming supply is connected via diode D1 which provides protection against reverse polarity while zener diode ZD1 provides protection from spike voltages.
A standard 7805 3-terminal regulator is then used to provide a stable 5V to the microcontroller. The battery voltage is sensed via a voltage divider using 33kΩ and 100kΩ resistors. This brings the voltage down to within the 0-5V range for the A/D input of the PIC16F819. Port B (RB0 to RB7) of the microcontroller is then used to drive the various LEDs, with current limiting provided via the 330Ω resistor network. RB7, pin 13, drives a switching transistor for the piezo buzzer.
Software:
The schema is based on PIC16F819 18-pin microcontroller which has an analog-to-digital (A/D) input to monitor the battery voltage and outputs capable of driving LEDs directly, to keep the component count down. There are seven LEDs in all, giving a good range of voltage indication. The topmost LED, LED1, comes on for voltages above 14V which will occur when the battery is fully charged. LED2 indicates for voltages between 13.5V and 14V while LED3 indicates between 13V and 13.5V. Normally, one of these LEDs will be on. LED4 covers 12.5V to 13V while LED5 covers 12V to 12.5V. LED6 covers from 11.5V to 12V while LED7 comes on for voltages below 11.5V. These two LEDs are backed up by the piezo chime which beeps for voltages between 11.5V and 12V and becomes more insistent for voltages below 11.5V.
That might seem fairly conservative. After all, most cars will start with no troubles, even though the battery voltage might be a touch below 12V, wont they? Well, no. Some modern cars will happily crank the motor at voltages below 11V but their engine management will not let the motor start unless the voltage is above 11V. So dont think that a modern car will always start reliably. This little battery monitor could easily prevent a very inconvenient failure to start! So lets describe the rest of the schema. The incoming supply is connected via diode D1 which provides protection against reverse polarity while zener diode ZD1 provides protection from spike voltages.
A standard 7805 3-terminal regulator is then used to provide a stable 5V to the microcontroller. The battery voltage is sensed via a voltage divider using 33kΩ and 100kΩ resistors. This brings the voltage down to within the 0-5V range for the A/D input of the PIC16F819. Port B (RB0 to RB7) of the microcontroller is then used to drive the various LEDs, with current limiting provided via the 330Ω resistor network. RB7, pin 13, drives a switching transistor for the piezo buzzer.
Software:
For the software, the design follows the basic template for a PIC microcontroller. Port A and its ADC (analog-to-digital converter) function are set up while port B functions as the output for the LEDs and buzzer. Once the set-up is complete, a reading will be taken at port RA2, the input for the A/D convertor. This reading is then compared with a series of values to determine the range of the voltage. This is similar to a series of "if" statements in Basic language. If the voltage is found to be within a certain range, the relevant port B pin will be turned on. If the voltage is below 12V, the buzzer will be turned on for a brief period, to signal a low battery condition. As the voltage falls below 11.5V, the frequency of the beeps will increase, to signal increased urgency.
Building it:
All the parts are mounted on a small PC board measuring 46 x 46mm (available from Futurlec). The starting point should be the IC socket for the PIC16F819, as this is easiest to mount while the board is bare. The next item can be the PC terminal block. The resistors and capacitors can then follow. Make sure the electrolytics are inserted with correct polarity.
Make sure that you do not confuse the zener (ZD1) with the diode when you are installing them; the diode is the larger package of the two.
All the parts are mounted on a small PC board measuring 46 x 46mm (available from Futurlec). The starting point should be the IC socket for the PIC16F819, as this is easiest to mount while the board is bare. The next item can be the PC terminal block. The resistors and capacitors can then follow. Make sure the electrolytics are inserted with correct polarity.
Make sure that you do not confuse the zener (ZD1) with the diode when you are installing them; the diode is the larger package of the two.
Even more important, dont get the 78L05 3-terminal regulator and the 2N3906 transistor mixed up; they come in identical packages. The 78L05 will be labelled as such while the 2N3906 will be labelled "3906". And make sure you insert them the correct way around. The buzzer must also be installed with the correct polarity. The 330Ω current limiting resistors are all in a 10-pin in-line package. There are four green LEDs, two yellow and one red. They need to be installed in line and with the correct orientation.
Testing:
Before you insert the PIC16F819 microcontroller, do a voltage check. Connect a 12V source and check for the presence of 5V between pins 14 & 5 OF IC1. If 5V is not present, check the polarity of regulator REG1 and the polarity of the diode D1. If these tests are OK, insert the IC and test the unit over a range of voltage between 9V and 15V. Make sure that all LEDs come on in sequence and the piezo buzzer beeps for voltages below 12V.
Now it is matter of installing the unit in your car. It is preferable to install the unit in a visible position for the driver. However, it should not obscure any other instruments. The unit should be connected to the cars 12V supply after the ignition switch. This will turn the unit off with the other instruments and prevent battery drain while the motor is not running.
Author :Alan Bonnard Copyright : Silicon Chip Publications Pty Ltd
DELL 22 inch WIDE LCD MONITOR 2208WFP SMPS WORKING PRINCPLE
DELL MONITOR 2208WFP _ SMPS [Power Supply] _ WORKING
CN850 is a connector for connecting AC Power. F850 is a fuse to protect all the schema AC. Input voltage is from 90Vto 264V. R850/3851are joined between two inputting main schema to prevent man from shock. L850 is used to filter low frequency noise. C850and C851are used to discharge the noise that L850 produced. High frequency waves are damped by C852.
High Voltage to Low Voltage Control Circuit
D850 is a rectifier in which there are 4build-in diodes, inverting AC to DC. C854 is used to smooth the wave from rectifier. U850 is a highly integrated PWM controller. Typical start-up current for U850 is only 20uA, When current flow through R8 1/R842/R843 gets to Pin 3of U850,with VDD hold-up capacitor C855, U850 is enough for starting up.
WhenU850 begins to operate Pin8of U850 will output square wave to drive Q850, then the main current flow get to GND bypassing through T850, Q850. Because of the change of current flow, wires in the other side of T850 will induct current. In the same time, the current inducted by wires which
connected T850 Pin 1 and Pin 3, with components of D852, R856 and C855 ,will be supplied to U850 for normal operating.
When the sense voltage across the sense resistor R859, reaches the threshold voltage around 0.85v, the output GATE drive will be turned off. Every time when the output of power supply is shorted or over loaded, the FB voltage will increase, the build-in PWM output will then be turned off. Both of two will prevent the power supply from being overheated under over loading condition. The PWM duty cycle is determined by this current sense signal and VFB, the feedback voltage, when the voltage on sense pin reaches V- (PWMcopm) = (Vcomp-2Vf) / 3, A switch cycle will be terminated immediately, Vcomp is internally clamped to a variable voltage around 0. 85V for output power limit.
When Q850 are turned off, the main current flow will be consumed through D851, C875, R853/R854/R855 and D853, This will prevent Q850 from being damaged under large current impulse and voltage spike.
DC_24V ,12Vand 5VOutput Circuit and Feedback schema.
D854&D855 are used to rectify the inducted current. C862 are used to store energy when current is reversed. The parts including L852 are used to smooth the current waves that are from D854&D855, and then 24Vvoltage is supplied. D880&D881 are used to rectify the inducted current. C881 is used to store energy when current is reversed. The parts including U880 are used to change the voltage from about 13Vto steady 12V, and then 12Vvoltage is supplied. D856 is used to rectify the inducted current. C874, C864&C875are used to store energy when current is reversed. The parts including L851, and C876are used to smooth the current waves that are from D856, and then 5Vvoltage is supplied. 5Vsupply voltage feed back to PWM controller U850 via R861, R860,and I850,I851.R859,C859 and C863 are used to control response time. LD7575 implements an OVP function on Vcc .Whenever the Vcc voltage is higher than the OVP threshold voltage, the output gate drive schema will be shutdown simultaneously thus to stop the switching of the power MOSFET until the next on.
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