Monday, September 30, 2013

Soft Start For Torch Increases The Life Of Torch Bulbs

The halogen or krypton bulbs in modern torches (USA and Canada: flashlights) have a limited life and are not particularly cheap. A simple modification in the torch lengthens the life appreciably. It is a fact of nature that any incandescent bulb has a finite life. However, the bulbs in modern torches (US and Canada: flashlight) have a less-than-average life. The reason for this is that the halogen or krypton bulbs used are operated at over-voltage to give as bright a light as feasible. The life of these bulbs may be extended simply by connecting a resistor in series with the bulb.

For instance, when the battery voltage is 6V and the bulb is a 500mA type, a series resistor of 1Ω will reduce the voltage across the bulb by about 0.5V. This will certainly lengthen the life of the bulb, but it will also cause a reduction in the available brightness. Also, energy is wasted in the resistor (evinced by heat production). Clearly, this is not a very good solution to the problem. A better one is shunting the bulb with a transistor in series with a resistor.

Soft Start For TorchMOSFET:

Another well-known fact is that incandescent bulbs normally burn out when they are being switched on. This is because the resistance of the cold filament is significantly lower than that during normal operation. This results in a switch-on current that is much higher than the normal operating current. Clearly, much is to be gained by damping the switch-on current. The switch-on current may be limited by a simple circuit that is small enough to allow it to be built into most types of torch. As the diagram shows, such a circuit consists of nothing more than a metal-on-silicon-field-effect-transistor, or MOSFET, and a resistor.

Soft Start For Torch - Increases The Life Of Torch BulbsThe transistor may be almost any current n-channel type that can handle the requisite power. The popular BUZ11 or BUZ10 is eminently suitable for the present application. The requisite limiting of the start-up current is provided by the internal gate capacitance of the transistor in conjunction with the large gate resistor. If needed, a small capacitor may be added between gate and drain. Once the transistor is conducting hard, the remaining losses are negligible. This is true also when the torch is switched off: the quiescent current flowing through the transistor is much smaller than that caused by the self-discharge of the batteries.


Since it is much simpler to break into the positive supply line of a torch than into the negative line, the addition of the limiting circuit makes it necessary for the batteries to be inserted into the torch the other way around from normal (as indicated by the manufacturer). Also, the on/off switch of a modified torch works the other way around from normal. Fitting the modification in some of the popular Mag-Lite torches is fairly straightforward.

After the rubber cover of the on/off switch has been removed, the entire push-button switch mechanism may be removed by releasing a central hexagonal bolt. The switch terminals may serve as soldering supports for the transistor-resistor series network. If it proves impossible to obtain a 47 MΩ resistor, four or five surfacemount-technology (SMT) resistors of 10 MΩ may be linked in series. Such a link works just as well and is almost as small as a normal 47MΩ resistor.
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Sunday, September 29, 2013

Curve Tracer Adaptor

This unit employs a dual trace oscilloscope with X-Y function as a display to test and demonstrate the action of circuits and components such as transistors, diodes, zener diodes, and terminated and unterminated transformers. A low frequency sinewave (ie 10Hz - 1kHz) is applied to op amp IC2a via potentiometer VR1 to set the "X" and "Y" levels for the X-Y display on the scope. The output of IC2a is applied to the X input via R4 and IC2b and also to Probe 1 via the contacts of relay 1. IC2b provides a low impedance drive for the X input and also isolates the X input cable capacitance from probe 1. The current flowing into the probes develops a voltage across R4 which is processed by IC2d and applied to the CRO Y input to represent current.

Curve Tracer Adaptor circuit schematic

The scope display thus represents an X-Y graph where voltage across a circuit under test is displayed on the X axis (horizontal) and the current though it displayed on the Y axis (vertical). With a calibrated scope this equates to 1mA/V. IC1 and a relay are included to enable two probes to be used and comparisons made between a known good device and a faulty one. The relay should be a low capacitance reed type. By using the scope’s X and Y gain controls, the sinewave applied to the device under test should be adjustable from a few millivolts up to 24V peak-peak to get a very useable display.

Thus, the unit can be used on voltage sensitive devices and at the other end of the scale apply enough voltage to check the operation of, say, a 10V zener diode. Note that all devices should be tested in the unpowered condition. If used for in-circuit tests, the effects of circuit components will need to be taken into account. Shielded coax leads should be used for the X and Y inputs and the probe leads should have zero resistance. Normal scope probes should not be used as these usually have significant built-in resistance which will interfere with measurements.
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Saturday, September 28, 2013

Infrared Remote Tester

Suitable for any Infrared emitting device, 3V battery supply

A very simple device allowing a quick check of common Infra-red Remote-Controls can be useful to the electronics amateur, frequently asked to repair or test these ubiquitous devices. A reliable circuit was designed with a handful of components: the LED will flash when any of the Remote-Control push buttons will be pressed. The side of the Remote-Control bearing the IR emitting diode(s) must be directed towards the Photo Transistor (Q1) of the checker circuit: maximum distance should not exceed about 20 - 25cm.

Circuit Diagram:

IR-RemoteTester Infrared Remote Tester Circuit Diagram


R1 = 470K
R2 = 47R
D1 = LED Any Type
Q1 = Photo Transistor
Q2 = BC327
B1 = 3V Battery or 2 AA cell


  • Current drawing of the circuit is less than 1mA when the LED illuminates and 0mA when no signal is picked-up by the Photo Transistor: therefore, SW1 can be omitted.
  • SW1 will be SPST Toggle or Slider Switch

Source :

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Friday, September 27, 2013

Solar Battery Protector Prevents Excessive Discharge

This circuit prevents the battery in a solar lighting system from being excessively discharged. Its for small systems with less than 100W of lighting, such as several fluorescent lights, although with a higher rated Mosfet at the output, it could switch larger loads. The circuit has two comparators based on an LM393 dual op amp. One monitors the ambient light so that lamps cannot be turned on during the day. The second monitors the battery voltage, to prevent it from being excessively discharged. IC1b monitors the ambient light by virtue of the light dependent resistor connected to its non-inverting input. When exposed to light, the resistance of the LDR is low and so the output at pin 7 is low.

Solar battery protector prevents excessive discharge circuit schematic

IC1a monitors the battery voltage via a voltage divider connected to its non-inverting input. Its inverting input is connected to a reference voltage provided by ZD1. Trimpot VR1 is set so that when the battery is charged, the output at pin 1 is high and so Mosfet Q1 turns on to operate the lights. The two comparator outputs are connected together in OR gate fashion, which is permissible because they are open-collector outputs. Therefore, if either comparator output is low (ie, the internal output transistor is on) then the Mosfet (Q1) is prevented from turning on. In practice, VR1 would be set to turn off the Mosfet if the battery voltage falls below 12V. The suggested LDR is a NORP12, a weather resistant type available from Farnell Electronic Components Pty Ltd.
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Thursday, September 26, 2013

Super Simple 3 Watt Audio Power Amplifier

Here is the circuit diagram of superb mini audio power amplifier, That can be power with 4.5 volt dc to 18 volts dc (maximum). This amplifier is based on TDA1015, Product of NXP Semiconductors formerly PHILIPS Semiconductors. The TDA1015 is a monolithic integrated audio amplifier circuit in a 9-lead single in-line (SIL) plastic package. The device is especially designed for portable radio and recorder applications and delivers up to 4 watt in a 4 ohm load impedance. The very low applicable supply voltage of 3,6 V permits 6 V applications.

3 Watt Audio Power Amplifier circuit project
3 Watt Audio Power Amplifier circuit schematic
click on the images to enlarge


  • In-car use
  • Your own unique application
  • Power amplifier for audio projects
  • For use with portable audio equipment
  • Small but powerful multi-purpose amplifier
Special features:
  • Low current drain
  • High output power
  • Thermal protection
  • High input impedance
  • Separated preamplifier and power amplifier
  • Limited noise behavior at radio frequencies
  • Single in-line (SIL) construction for easy mounting
  • Quiescent current : 12mA
  • Thermal and short circuit protection
  • Frequency Response : 60Hz - 15Khz
  • Max. output power : 3W (4ohm/12V)
  • Input sensitivity : 20-15mV selectable
  • Power supply : 4.5 - 15V DC @ 400mA
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Wednesday, September 25, 2013

Keyboard Mouse Switch Unit

Unplugging or re-connecting equipment to the serial COM or PS2 connector always gives problems if the PC is running. Even if you only need to swap a mouse or changeover from a graphics keyboard to a standard keyboard. The chances are that the connected equipment will not communicate with the PC, it will always be necessary to re-boot. If you are really unlucky you may have damaged the PC or the peripheral device. In order to switch equipment successfully it is necessary to follow a sequence. The clock and data lines need to be disconnected from the device before the power line is removed. And likewise the power line must be connected first to the new device before the clock and data lines are re-connected.

This sequence is also used by the USB connector but achieved rather more simply by using different length pins in the connector. The circuit shown here in Figure 1 performs the switching sequence electronically. The clock and data lines from the PC are connected via the N.C. contacts of relay RE2 through the bistable relay RE1 to connector K3. Pressing push-button S1 will activate relay RE2 thereby disconnecting the data and clock lines also while S1 is held down the semiconductor switch IC1B will be opened, allowing the voltage on C4 to charge up through R4. After approximately 0.2 s the voltage level on C4 will be high enough to switch on IC1A, this in turn will switch on T1 energizing one of the coils of the bistable relay RE1 and routing the clock, data and power to connector K2.

When S1 is released relay RE2 will switch the data and clock lines through to the PC via connector K1. It should be noted that the push-button must be pressed for about 0.5s otherwise the circuit will not operate correctly. Switching back over to connector K3 is achieved similarly by pressing S2. The current required to switch the relays is relatively large for the serial interface to cope with so the energy necessary is stored in two relatively large capacitors (C2 and C3) and these are charged through resistors R1 and R6 respectively. The disadvantage is that the circuit needs approximately 0.5 minute between switch-overs to ensure these capacitors have sufficient charge.

The current consumption of the entire circuit however is reduced to just a few milliamps. The PCB is designed to accept PS2 style connectors but if you are using an older PC that needs 9 pin sub D connectors then these will need to be connected to the PCB via flying leads. In this case the mouse driver software configures pin 9 as the clock, pin 1 as the data, pin 8 (CTS) as the voltage supply pin and pin 5 as earth.

R1 = 2kΩ2
R2 = 47kΩ
R3 = 10kΩ
R4 = 4kΩ7
R5 = 1kΩ
R6 = 1kΩ2
C1 = 10µF 10V radial
C2 = 1000µF 10V radial
C3 = 2200µF 10V radial
C4 = 2µF2 10V radial
D1-D5 = 1N4148
T1 = BC547
IC1 = 4066 or 74HCT4066
RE1 = bistable relay 4 c/o contacts
RE2 = monostable relay 2 c/o contacts
K1,K2,K3 = 6-way Mini-DIN socket (pins at 240°, PCB mount
S1,S2 = push-button (ITTD6-R)
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Tuesday, September 24, 2013

MP3 FM Transmitter Circuit Diagram

Heres a simple VHF FM transmitter that could be used to play audio files from an MP3 player or computer on a standard VHF FM radio. The circuit use no coils that have to be wound. This FM transmitter can be used to listen to your own music throughout your home. When this FM transmitter used in the car, there is no need for a separate input to the car stereo to play back the music files from your MP3 player.
Project image :
MP3-FM-Transmitter Projecat
To keep the circuit simple as well as compact, it was decided to use a chip made by Maxim Integrated Products, the MAX2606 [1]. This IC from the MAX2605-MAX2609 series has been specifically designed for low-noise RF applications with a fixed frequency. The VCO (Voltage Controlled Oscillator) in this IC uses a Colpitts oscillator circuit. The variable-capacitance (varicap) diode and feedback capacitors
for the tuning have also been integrated on this chip, so that you only need an external inductor to fix the central oscillator frequency.
t is possible to fine-tune the frequency by varying the voltage to the varicap. Not much is demanded of the inductor, a type with a relatively low Q factor (35 to 40) is sufficient according to Maxim. The supply voltage to the IC should be between 2.7 and 5.5 V, the current consumption is between 2 and 4 mA. With values like these it seemed a good idea to supply the circuit with power from a USB port.
Circuit diagram:
MP3-FM-Transmitter-Schematic -Circuit Diagram
Resistors (all SMD 0805)
R1,R2 = 22kΩ
R3 = 4kΩ7
R4,R5 = 1kΩ
R6 = 270Ω
P1 = 10kΩ preset, SMD (TS53YJ103MR10 Vishay Sfernice, Farnell # 1557933)
P2 = 100kΩ preset, SMD(TS53YJ104MR10 Vishay Sfernice, Farnell # 1557934)
Capacitors (all SMD 0805)
C1,C2,C5 = 4μF7 10V
C3,C8 = 100nF
C4,C7 = 2nF2
C6 = 470nF
L1 = 390nF, SMD 1206 (LQH31HNR39K03L Murata, Farnell # 1515418)
L2 = 2200Ω @ 100MHz, SMD, common-mode choke, 1206 type(DLW31SN222SQ2L Murata, Farnell #1515599)
IC1 = MAX2606EUT+, SMD SOT23-6 (Maxim Integrated Products)
K1 = 3.5mm stereo audio jack SMD (SJ1-3513-SMT
CUI Inc, DIGI-Key # CP1-3513SJCT-ND)
K2 = 5-pin header (only required in combination with 090305-I pre-emphasis circuit)
K3 = USB connector type A, SMD (2410 07 Lumberg, Farnell # 1308875)
A common-mode choke is connected in series with the USB connections in order to avoid interference between the circuit and the PC supply. There is not much else to the circuit. The stereo signal connected to K1 is combined via R1 and R2 and is then passed via volume control P1 to the Tune input of IC1, where it causes the carrier wave to be frequency modulated. Filter R6/C7 is used to restrict the bandwidth of the audio signal. The setting of the frequency (across the whole VHF FM broadcast band) is done with P2, which is connected to the 5 V supply voltage.
The PCB designed uses resistors and capacitors with 0805 SMD packaging. The size of the board is only 41.2 x 17.9 mm, which is practically dongle-sized. For the aerial an almost straight copper track has been placed at the edge of the board. In practice we achieved a range of about 6 metres (18 feet) with this. There is also room for a 5-way SIL header on the board. Here we find the inputs to the 3.5 mm jack plug, the input to P1 and the supply voltage. The latter permits the circuit to be powered independently from the mains supply, via for example three AA batteries or a Lithium button cell. Inductor L1 in the prototype is a type made by Murata that has a fairly high Q factor: minimum 60 at 100 MHz.
PCB Layout :
Take care when you solder filter choke L2, since the connections on both sides are very close together. The supply voltage is connected to this, so make sure that you don’t short out the USB supply! Use a resistance meter to check that there is no short between the two supply connectors before connecting the circuit to a USB port on a computer or to the batteries.
P1 has the opposite effect to what you would expect (clockwise reduces the volume), because this made the board layout much easier. The deviation and audio bandwidth varies with the setting of P1. The maximum sensitivity of the audio input is fairly large. With P1 set to its maximum level, a stereo input of 10 mVrms is sufficient for the sound on the radio to remain clear. This also depends on the setting of the VCO. With a higher tuning voltage the input signal may be almost twice as large (see VCO tuning curve in the data sheet). Above that level some audible distortion becomes apparent. If the attenuation can’t be easily set by P1, you can increase the values of R1 and R2 without any problems.
Measurements with an RF analyzer showed that the third harmonic had a strong presence in the transmitted spectrum (about 10 dB below the fundamental frequency). This should really have been much lower. With a low-impedance source connected to both inputs the bandwidth varies from 13.1 kHz (P1 at maximum) to 57 kHz (with the wiper of P1 set to 1/10). In this circuit the pre-emphasis of the input is missing. Radios in Europe have a built-in de-emphasis network of 50 μs (75 μs in the US). The sound from the radio will therefore sound noticeably muffled. To correct this, and also to stop a stereo receiver from mistakenly reacting to a 19 kHz component in the audio signal, an enhancement circuit Is published elsewhere in this issue (Pre-emphasis for FM Transmitter, also with a PCB). Author: Mathieu Coustans, Elektor Magazine, 2009
Notice. The use of a VHF FM transmitter, even a low power device like the one described here, is subject to radio regulations and may not be legal in all countries.

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Monday, September 23, 2013

High Input Voltage Linear Regulator

Commonly used 3-pin linear voltage regulators, for example the LM317, cannot handle input voltages in excess of about 30V. The LR8A from Supertex Inc is a new, adjustable three pin regulator that can accept input voltages up to 450V and can supply an output current of 0.5mA to 10mA. Using this device it is possible to work with rectified 230VAC. The LR8 has a wide input voltage range of +12 V to +450V. Two external resistors (R1 and R2) allow the output voltage to be adjusted from 1.20 V to 440 V provided that the input voltage is at least 10 V greater than the output voltage. The LR8 adjusts the voltage difference between the Vout and ADJ pins to a nominal value of 1.20V.

High Input Voltage Linear Regulator circuit diagramThis 1.20V is amplified by the external resistor ratio of R1 and R2. An internal constant bias current of 10µA is connected to the ADJ pin so that Vout is increased by a constant voltage of 10µA times R2. The formula for calculating the output voltage is given next to the circuit diagram. To ensure stable operation of the regulator a minimum output current of 500µA is necessary and a bypass capacitor of minimum 1.0µF should be used. Protection circuits in the LR8 limit the output current to 15mA typically and temperature protection ensures that the device temperature will not exceed 125oC.

High Input Voltage Linear RegulatorWhen the device reaches its temperature limit, the output voltage/current will decrease to keep the junction temperature within limits. The two circuit diagrams show the LR8 used as a voltage regulator and as a constant current source. The current source can be used to a drive an LED. This configuration would give an LED with super-wide input voltage range, i.e., from +12V to +450V. The LR8 was originally designed to be used for switch mode supply start-up applications so it incorporates a feature which shuts down the LR8 when the output voltage exceeds the input voltage. Diode D1 is therefore necessary in the voltage regulator circuit diagram to prevent the output voltage exceeding the input voltage at any time.

LR8 PinoutThe minimum value of the input capacitor C1 can be calculated from the following formula: C1(min) = (IL t ) / (Vpk – Vout – 10V) Where IL is the load current, and t the period between two voltage peaks. At 50 Hz, using one rectifying diode this will give a value t = 20 ms. Vpk is the peak input voltage, while Vout is the selected output voltage. The LR8 is available in two package outlines. The LR8N8 is a SOT89 SMD package while the LR8N3 is the familiar TO92 Transistor outline (e.g. BC 238). The TO-92 package can dissipate a maximum of 0.74W while with suitable heatsinking, the SMD package can dissipate 1.6W.
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Sunday, September 22, 2013

Speech Eroder

Nowadays, the speech quality on our telephone systems is generally very good, irrespective of distance. However, there are occasions, for instance, in an amateur stage production, or just for fun, when it is desired to reproduce the speech quality of yesteryear. The eroder circuit accepts an acoustic (via an electret micro-phone) or electrical signal. The signals are applied to the circuit inputs via C1 and C2, which block any direct voltage. The input cables should be screened. The signals are brought to (about) the same level by variable potential dividers P1-R1-R4 and P2-R2-R3, and then applied to the base of transistor T1. The level of the combined signals is raised by this preamplifier. The preamplifier is followed by an active low-pass filter consisting of T2–T4, C3, C4, R6–R8, and P4.
Speech Eroder Circuit DiagramAlthough, strictly speaking, P3 serves merely to adjust the volume of the signal, its setting does affect the filter characteristic. Note, by the way, that the filter is a rarely encountered current-driven one in which C3 and C4 are the frequency-determining elements. It has a certain similarity with a Wien bridge. Transistors T3 and T4, and resistors R8 and P4 form a variable current sink. The position of P4 determines the slope of the filter characteristic and the degree of overshoot at the cut-off frequency. The low-pass filter is followed by an integrated amplifier, IC1, whose amplification is matched to the input of the electronic circuits connected to the eroder with P5. The final passive, third-order high-pass filter is designed to remove frequencies above about 300 Hz. The resulting output is of a typical nasal character, just as in telephones of the past.
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Saturday, September 21, 2013

2000 Chevrolet 2500 Express Van Wiring Diagram

2000 Chevrolet 2500 Express Van Wiring Diagram

The Part of 1957-58 Dodge 4-Way Power Seat Wiring Diagram: power distribution, relay center,
ignition switch, fusible link, red wire, yellow wire, fuse block, starter motor, solenoid, generator, battery, black wire, fuse relay center, neutral position switch, starter relay, solenoid contacts, generator, black wire
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Friday, September 20, 2013

1988 Ford F150 Wiring Diagram

1988 Ford F150 Wiring Diagram
(click for full size image)

 The Part of 1988 Ford F150 Wiring Diagram:fuse link, black wire, electronic eigne control, start, starter relay, batterey, starter motor, radio mouse capacitr, starter igmition, instrument cluster, charger, indicator lamp, fuse panel, charge power distribution.
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Wednesday, September 11, 2013

Pneumatic Starter Motor

Pneumatic Starter Motor
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Tuesday, September 10, 2013

Simple Subwoofer Lowpass Filter using uA741 Single Op Amp Ic

This is the simplest Sub woofer Low Pass filter Circuit using uA741 single op amp ic.The circuit is very low cost with respect to their work. The cut off frequency of this circuit is 25Hz to 80Hz maximum.

Using this circuit , you can easily design a 2.1 Sub-woofer Speaker System at your own Home. The circuit contains very few components.In Pakistan, the cost of this circuit with PCB is Rs:45. The same circuit is working in my own hand made sub-woofer system.So Try this

 Sub-woofer Low-pass Filter using uA741 Single Op-Amp Ic  Circuit Diagram

Subwoofer Lowpass Filter using uA741 Single Op-Amp Ic

Parts List:
R1,R3,R4 = 10K 1/4W
R2=100K 1/4W
CY1,CY2 = 0.22uF Polyester
C1,C2 = 10uF/25V Electrolytic
IC1 = uA741A Single Op-Amp Ic + 8 Pin Ic Socket
3 Pin Male & Female Connector x 2
2 Pin Male & Female Connector x 1
PCB as in required size 4.5 cm x 3.4 cm

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Wednesday, September 4, 2013

Active Audio System Use three TDA2052

This active audio audio system use three TDA2052 chips and 5 speakers ( one woofer, two tweeters and two midranges ) .For this TDA2052 active audio system we need dual 20 volts power supply and five volts supply for the stand by function.To the input of the every audio IC chip is placed an audio filter for filtering the audio signal for used speakers ( low pass for woofer , high pass for midranges and tweeters )

Active Audio System Circuit Diagram

The subwoofer plays the 20 to 300 Hz frequency range, while the remaining 300 Hz to 20KHz are sent to two separate channels with stereo effect.If one of the amplifier is affected by clipping distortion the others amplifiers are not affected .
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Tuesday, September 3, 2013

9 Sec Timer with LED Indication and Control Relay

The electronic circuit provides a visual time 9 second delay using ten LED before control by closing a 12 Vdc relay. That the reset switch has closed, IC 4017 decade counter will be reset to zero count which illuminates the LED driven from pin 3. IC 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 Vdc.

9 Sec Timer with LED Indication and Control Relay Circuit Schematic

That time the switch is opened, the transistor in parallel with the timing capacitor (22uF) is shut off allowing the capacitor to begin charging and the IC 555 timer circuit to produce an approximate one second clock signal to the decade counter. The counter advances on each positive going change at pin 14 and is enabled with pin 13 terminated low. When the 9th count is reached, pin 11 and 13 will be high, stopping the counter and energizing the relay. Longer delay times can be obtained with most capacitor or most resistor at pins 2 and 6 of the IC 555 timer.
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Monday, September 2, 2013

Alternating Square Pulse Generator

The generator circuit was designed to produce alternating square pulses with vibrations in different parts of the circuit.

4027 – a dual JK flip flop that has independent clock, set, and reset inputs for each flip flop used in toggle, register, and control functions due to its features such as capability of driving two low power TTL loads, logic edge clocked flip flop design, logic swing independent of fanout, toggle rate of 3 MHz at 5 Vdc, supply voltage range of 3 V to 6 V, protection of diodes on all inputs, noise immunity, and quiescent current of 2 nA at 5 Vdc. 4001 – a quad 2-input NOR gate integrated circuit, generally characterized by small fluctuation in voltage supply, very high impedance, outputs that can sink and source, one output can drive up to 50 inputs, high speed gate propagation time, high frequency, and low power consumption.

Alternating Square Pulse Generator Circuit Diagram

BC550 – an NPN general purpose transistor with low current and low voltage used for low noise stages in audio frequency equipment

The generator functions without distortion when it reaches 100 KHz. The square pulses are produced when the selector switch S1 is turned ON, which matches the output of Q3 at pin 7. The 5V pulse line is applied to J1 input, the signal is fed to T-flip flop IC1A through S2 which creates pulses indicated at half of the duration time where pin 2 handles the division of pulse frequency. The pulses are applied to IC2 pin 14 and IC3A input. IC2 acts as decimal counter with decode outputs where each entry produces HIGH on one of the outputs. From the initial pulse entry, the output of Q1 becomes HIGH while others are LOW. The second pulse entry causes HIGH output on Q2, and third entry applies on Q3. The same operation occurs for the succeeding pulse line entry, since the counter checks the number of pulses that passes the generator output.

The generator output stage is considered on levels where the driving stage of Q2 creates positive output voltage and the saturation of Q 3 in the cutoff region. Through the potentiometer, the signal is applied in the output of J2. Using the gates of IC3B-C-D, the sine wave or triangular wave can be changed to square pulses in the circuit input. The conversion is directly made from the command of S2. The switching can also be done by DIP switch S2. A suitable power supply or two NiCd batteries can maintain the circuit with the stabilization of voltage achieved by two Zener diodes.

R1-10= 10Kohm
R2= 47Kohm
R3= 22Kohm
R4-5= 18Kohm
R6-7= 4.7Kohm
R8= 1.2Kohm
R10= 100Kohm
R11-13= 470 ohm
R12= 1.5Kohm RV1= 1.2Kohm linear pot.
C1= 15pF ceramic
C2-3= 10nF 63V MKT
C4-5= 470uF 16V
C6= 1uF 63V MKT
D1-2= 5.1V 0.5W zener
D3-4= 1N4148
Q1-2= BC560C
Q3= BC550C IC1= 4027
IC2= 4027
IC3= 4001B
S1= switch DIL 10S
S2-3= 2X2 mini switch
BATT= 9V Battery NiCd

The generation of square pulses can bring about plenty of usages by adjusting the input in digital circuits and controlling the frequencies of amplifiers, loudspeakers, rooms of hearings, and others. One popular application is in the camera flash temporal profile where square pulses act as a heating source in the photoflash technique. The amount of light emitted by an electronic flash is controlled by the shunted output of a pulse generator known as tailbiters where longer pulses are made with the biting off the tail of the impulse.
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Sunday, September 1, 2013

Power Failure and Low Line Signals

This is a circuit of Power-Fail and Low-Line Signals. This circuit is used to warn the processor when the power failure or a brownout is occurs. The processor will enter a power-down routine, when either of those signals interrupts the processor. Back up important data prior to the POR placing the processor in reset and cease its current  activities are things that the processor do when enter the routine. Here is the circuit.Power-fail comparator is used to create a power-fail signal by monitoring the unregulated DC voltage. The regulator powers both supervisor circuit and the processor by using the the unregulated DC voltage.

Power-Failure and Low-Line Signals Schematic

Power-Failure and Low-Line Signals
 The regulator’s output capacitor retains its output voltage, so the unregulated voltage drops before the regulator’s voltage. And also, we can know drop in the regulator’s voltage. The processor can enter its power-down routine prior to being reset, if the power supply voltage were to drop low enough because of Detecting the regulator’s voltage drop.A supervisor provides a low-line signal, which goes active whenever the monitored power supply drops to a level slightly above the reset threshold so the processor can still receive warning of an imminent power failure when there is no access to the unregulated voltage.

To cause the POR to issue a reset, the processor warned that the power-supply voltage may decrease enough by the low-line signal. To anticipate the POR generating a reset, the processor backs up important data because of power failure  or a brownout.
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