BA5417 STREREO POWER AMPLIFIER CIRCUIT

BA5417 Stereo Power Amplifier Circuit

BA5417 stereo amplifier circuit has of good features like thermal shut down, standby function, soft clipping, wide operating voltage range etc. The circuit can be deliver 5W × 2 when VCC = 12V and RL = 4Ω, or 2.8W x 2 when VCC = 9V RL = 3Ω.This and amplifier circuit has excellent sound quality, and low THD (total harmonic distortion) around 0.1% at F = 1kHz; Pout = 0.5W

BA5417 Stereo Power Amplifier Circuit

C-in are DC decoupling capacitors which block any DC level present in the input signals. C3 and C5 couples the Amplifiers left and right power outputs to the corresponding loud speakers. C2 and C6 are bootstrap capacitors. Bootstrapping is a method in which a portion of the amplifiers is taken and applied to the input. The prime objective of bootstrapping is to improve the input impedance. Networks R1,C1 and R2,C7 are meant for improving the high frequency stability of the circuit. C4 is the power supply filter capacitor. S1 is the standby switch. C8 is a filter capacitor. RF1 and RF2 sets the gain of the left and right channels of the amplifier in conjunction with the 39K internal feedback resistors.

Automatic lamp Circuit

type='html'>This series will work as the lighting will automatically turn on when the voltage net PLN off. If the net voltage on the series will off automatically.

Emergency Light chain scheme can be viewed directly on the image above


Components list:

R1 R2 C1 D1,D2 S1 Tr1 Trafo L1,l2 Batery

: 33 Ohm : 470 Omh : 470 uF/16v : 1n4001 : switch (push on push off) : BC 160 or BC 143 : 4,5 volt 200 mA : lamp 2,5 volt : NiCd 2x1,25 volt 2-4 Ah

Series of automatic lighting unit is very simple. Voltage electricity from the net PLN revealed by transformer Tr1 and change in DC with half-wave system by dioda D1 and capacitor C1.

Next portion 6 Volt DC is used to fill the 2 Ni-Cad Battery through R1 and D2 with a continuous flow of about 100 mA (charging current to a safe a Ni-Cad battery 2 Ah).

reverse bias between the base of emitor transistors T1 obtained from the voltage fall on the D2 will make transistors T1 does not work so that lamp will be off. When voltage net PLN suppressed, T1 base transistors will be biased flow through R2, transistors T1 will work and lamp on.

When the voltage net PLN entry, transistors T1 will does not work, the lamp will be off and the battery charged through R1 and D2

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Circuit of Mouse Repellent

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A simple series of mouse repellent is a oscilator the issue on the ultrasonic wave frequency range 20 - 40 kHz. The ultrasonic waves will not be heard in the ear, but we will be with the one for the mouse ear. Base Frequency will be modulation with a 50 Hz signal is obtained from the frequency PLN through capacitor C4 (to avoid a mouse immune to it) so that the resulting swing frequency between 20 - 40 kHz periodically. Effects experienced mouse feels very good, seems like we are at a music concert with the rhythm of perplexedly ragged and could not enjoy at all. (What the human ear will not hear at all).
Circuit of Mouse Repellent

Components list:

R1 R2,R3 C1 C2 C3 C4 C5 D1,D2,D3,D4 IC1 TR1 TD1 F1

: 1 K : 15 K : 1 nF : 1 uF/16v : 100 nF : 220 nF : 1000 uF/16v : 1n4001 : LM 555 : Trafo 6v/200mA : Speaker twiter : fuse 100 mA

Heart of a series of repellent electronic mouse is a type of IC 555 that have been very popular, cheap and versatile. Use of the piezo electric loudspeaker (tweeter speaker ) so that the ultrasonic frequency is more effective. Electronic rat repellent is effective for rooms up to 200 m2 area of origin appropriate placement. Can be placed in the top corner of the room so that its frequency noise can be spread to all rooms without a hitch. Turn on continuously to ensure that the mouse does not come again.

CIRCUIT OF SIMPLE ON LINE UPS

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physical irfz44 & CD4047 chip

Simple Circuit of UPS on line

UPS (Uninterruptible Power Supply), is used to anticipate the power off. Output series UPS has a power of 60W (if the transformer is used the greater the power will higher). Before the series there is a major series of the adapter has a voltage between 9V - 12V with strong currents of 5A. Voltage generated is used to operate the series and fill the battery. UPS is designed to keep electronic devices can run even if the electricity off.

simple circuit of infra red remote control

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By using the NE 555 and LM 567we can create a system of remote control via infra red light media. This system works based on the frequency of reading the signal transmitted, so that the frequency of the signal transmitter in the series must be the same as the receiving frequency.

Frequency on the transmitter is determined by the value of R1 and C1 based on the following equation:

infra red remote control Transmitter

As mentioned above, the recipient must also have the same detection frequency with a frequency that transmitted by a circuit of transmitter. Frequency of a circuit of receiver is determined by the following equation:

infra red remote control Reciever

To simplify the process of tunning, R1 on the part of the receiver is a variable resistor. while at the transmitter is still valuable. When the series was ready, so that the system can work well, the first step is to do tunning, with the way the transmitter is turned on continuously, while R1 is set in the value until the recipient can detect the signal transmitter

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Simple circuit of elektronic buzzer

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Gbr. Skema Rangkaian Elektronic buzzer

Simple Electronic buzzer series is a series that only use 2 resistor, 3 capacitor , NE555 Chip, switch, and speaker. string up series of simple electronic buzzer is also very easy and simple. IC NE555 is the frequency of 1 kHz when the switch is pressed. This frequency can be set using the potensiometer 10 KOhm. Picture a series of simple electronic buzzer can be seen above:


IC NE555

555 timer IC provides practical solutions and relatively inexpensive for a variety of electronic applications related to the timing (timing). Especially two of the most popular application is a series of monostable and astable timing.

• Pin 1: Ground, is the input pin of the source of the negative DC voltage
• Pin 2: trigger, negative input from the lower comparators (comparator B) that maintain oscillation capacitor voltage in the lowest 1 / 3 Vcc and set RS flip-flop
• Pin 3: output, the output pin of the IC 555.
• Pin 4: reset, the pin that serves to reset the latch inside the IC to be influential to reset the IC work. This pin is connected to a PNP-type transistor gate, so the transistor will be active if given a logic low. Normally this pin is connected directly to Vcc to prevent reset
• Pin 5: control voltage, this pin serves to regulate the stability of the reference voltage negative input (comparator A). This pin can be left hanging, but to ensure the stability of the reference comparator A, usually associated with a capacitor of about 10nF to berorde pin groun
• Pin 6: threshold, this pin is connected to the positive input (comparator A) which will reset the RS flip-flop when the voltage on the capacitor from exceeding 2 / 3 Vc
• Pin 7: discharge, this pin is connected to an open collector transistor Q1 is connected to ground emitternya. Switching transistor serves to clamp the corresponding node to ground on the timing of certain
• Pin 8: vcc, pin it to receive a DC voltage supply. Usually will work optimally if given a 5-15V. the current supply can be seen in the datasheet, which is about 10-15mA.

10-Band Graphic Equalizer Circuit Diagram

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This circuit allows you to equlize the audio signals in 10 band. It uses low amount op-amps (TL074 - JFET op-amp) to anatomy a able blaster circuit. The affection of the architecture is a classical band-pass alive filter. The VCC is in ambit of 12 ~ 15 VDC and The VDD is in ambit of -12 ~ -15 VDC respectively.

Skema rangkaian 10-band
graphic equalizer

Note:
For more details the circuit scheme, click on the picture

As shown in the diagram, there are 10 same units that only differ in capacitance values of capacitors which determine the frequency band of each filter. The potentiometers adjust the predetermined regions of frequency in each unit.

The components must be high quality and have low tolerance, Specifically potesometer RV1... the 10 and capacitors.. The resistors must be metal-film type.

If it is intended for stereo use then it will be supposed it is made in two pieces with as much as possible suited the materials, between the channels, so that do not exist differences in the regulation of each band frequencies.

Switch S1 isolates the circuit EQ, when him we did not need and it ensures level [ flat ] response in the exit of circuit. The circuit should be connected between preamplifier and in a final power amplifier.

Component list of graphic equalizer circuit

• R1-R20= 10Kohms
• R21-R40= 1Mohms
• R41-R10Kohms
• R42= 1Kohms
• R43-R52= 2.2Kohms
• R53-R62= 47Kohms
• R63-64-66-67= 47Kohms
• R65= 10Kohms
• R68-69= 47 ohms 1/2W
• RV1-RV10= 100Kohms lin FADER
• RV11= 10Kohms log.
• C1= 180nF polyester
• C2= 18nF polyester
• C3= 100nF polyester
• C4= 10nF polyester
• C5= 47nF polyester
• C6= 4.7nF polyester
• C7= 22nF polyester
• C8= 2.2nF polyester
• C9= 12nF polyester
• C10= 1.2nF polyester
• C11= 5.6nF polyester
• C12= 560pF polysterine
• C13= 2.7nF polyester
• C14= 270pF polysterine
• C15= 1.5nF polyester
• C16= 150pF polysterine
• C17= 680pF polysterine
• C18= 68pF polysterine
• C19= 360pF polysterine
• C20= 36pF polysterine
• C21= 4.7uF polyester
• C22-23= 33pF polysterine
• C24= 10uF 25V
• C25,C26= 47uF 25V
• C27-C32= 47nF polyester
• IC1-IC3= TL074
• S1= 2X4 SW for stereo

600 Watt Darlington Power Amplifier Circuit

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This Power amplifier circuit is based around IC audio power amplifier driver (LM4702) manufactured by NATIONAL and darlington power transistors MJ11029 - MJ11028 by ON semiconductors

Rangkaian 600 Watt
Darlington Power Amplifier

Note:

• Recommended power supply voltage : 30V to 35V
• Max power supply voltage : 45V

This Power amplifier circuit produces output power up to 300 watts ( 8ohms) pada masing-masing channelnya. It is a high fidelity audio power amplifier. Designed for demanding consumer and pro-audio applications. You can also use this circuit with AV receivers, Audiophile power amps, Pro Audio High voltage industrial applications etc

Amplifier output power maybe scaled by changing the supply voltage and number of output devices. The circuit includes thermal shutdown circuitry that activates when the die temperature exceeds 150. CIRCUIT mute function, when activated, mutes the input drive signal and forces the amplifier output to a quiescent state.

IC audio power amplifier driver

(LM4707) Pinning

IC 555 Motorcycle Alarm Circuit

type='html'>Rangkaian Motorcycle Alarm

This circuit features an intermittent siren output and automatic reset. It can be operated manually using a key-switch or a hidden switch; but it can also be wired to set itself automatically when you turn-off the ignition. By adding external relays you can immobilize the bike, flash the lights etc. I have used Andy's Asymmetric Timer as the basis for this design.

Skema Rangkaian IC 555 Motorcycle Alarm

Any number of normally-open switches may be used. Fit "tilt" switches that close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. Use micro-switches to protect removable panels and the lids of panniers etc.

The alarm's standby current is virtually zero - so it won't drain your battery. Once activated - the rate at which the siren switches on and off is controlled by R7, R8 & C4. For example, increasing R7 will make the sound period longer - while increasing R8 gives longer silent periods.

The circuit is designed to use an electronic Siren drawing 300 to 400mA. It's not usually a good idea to use the bike's own Horn because it can be easily located and disconnected. However - if you choose to use the Horn - remember that the alarm relay is too small to carry the necessary current. Connect the coil of a suitably rated relay to the "Siren" output. This can then be used to sound the Horn, flash the lights etc.

The circuit board and switches must be protected from the elements. Dampness or condensation will cause malfunction. Connect a 1-amp in-line fuse AS CLOSE AS POSSIBLE to your power source. This is VERY IMPORTANT. The fuse is there to protect the wiring - not the alarm. Exactly how the system is fitted will depend on the make of your particular machine - so I'm unable to provide any further help or advice in this regard.

When you set the alarm - if one of the switches is closed - the siren will sound. This could cause annoyance late at night. A small modification will allow you to Monitor The State Of The Switches using LEDs. When the LEDs are all off - the switches are all open - and it's safe to turn the alarm on


Source: http://www.zen22142.zen

Megabass Circuit

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The following is megabass circuit schematic (rangkaian megabass) . The megabass circuit is a modified Baxandall tone control with no bass cut and no treble control. It boosts frequencies from about 30Hz to 160Hz can boost by 14dB.

Skema Rangkaian megabass

Note:

• The input capacitor can be replaced with a .01uf cap if you wish.
• The 10pf capacitor is optional and will start rolling off everything over 15kHz. 5pf will double this to 31kHz.
• The tone control requires a low impedence input. If you already have a low impedence input, the input buffer can be removed. However, the output is inverted.
• The opamp is not critical. A 4558 would be just fine.
• I do not show the parts for the +4.5 reference. Here is the +4.5 voltage divider I used.

IC A4558 Pinning

The A4558 is a monolithic Integrated Circuit designed for dual operational amplifier.

Absolute maximum ratings of A4558 Ap-amp

• Supply voltage VCC 20 or ±10 V
• Differential input voltage VIND 20 V
• Input voltage VIN ±10 V
• Power Dissipation PD 300 mW
• Operating temperature Topr -45 ~ +85 °C
• Storage temperature Tstg -55 ~ +150 °C

220 Volt Disco Lamp circuit

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This disco lamp circuit is not a voice operated switch (VOX) because this circuit is too dumb to differentiate between musical sound or human voice. This is rather a sound activated than voice activated. One interesting application is to control your disco lighting automatically by the musical sound from high power amplifier, when the music signal is dominating the sound space. The disco lamp circuit schematic diagram is shown below.

You can use either moving coil microphone or condenser microphone for this circuit. Make sure the electrolytic capacitor is rated for 16 volt or more. The potentiometer shown in the schematic diagram is used to adjust the gain of the pre-amplification. You can adjust this potentiometer to get a proper sound level where the relay would be activated.

List Componet Of Disco Lamp circuit

• R1 : 22k 1/4 watt resistor
• R2 : 4K7 watt resistor
• R3 : 2K2 watt resistor
• R4,R8 : 10K watt resistor
• R5 : 33K watt resistor
• R6 : 56K watt resistor
• R7 : 1M watt resistor
• Potensio: 50K
• C1 : 470uf/35V electrolytic capacitor
• C2 : 22n ceramic capacitor
• C3 : 100n ceramic capacitor
• C4 : 1Uf/50V electrolyticcapacitor
• D1 - D5 : 1N4007
• D6 : Zener 5.1v
• D7 : 1N4148
• IC : CD 4069
• SCR : FIR 3D
• Mic : Mic Condensor

Mobile Phone Battery Charger Circuit

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This Mobile phone chargers circuit presented here comes as a low-cost alternative to charge mobile telephones/battery packs.

Circuit of Mobile Phone Battery Charger

The 220V AC mains supply is downconverted to 9V AC by transformer X1. The transformer output is rectified by diodes D1 through D4 wired in bridge configuration and the positive DC supply is directly connected to the charger’s output contact, while the negative terminal is connected through current limiting resistor R2. LED2 works as a power indicator with resistor R1 serving as the current limiter and LED3 indicates the charging status. During the charging period, about 3 volts drop occurs across resistor R2, which turns on LED3 through resistor R3. An external 12V DC supply sourcecan also be used to energise the charger, where resistor R4, after polarity protection diode D5, limits the input current to a safe value. The 3-terminal positive voltage regulator LM7806 (IC1) provides a constant voltage output of 7.8V DC since LED1 connected between the common terminal (pin 2) and ground rail of IC1 raises the output voltage to 7.8V DC. LED1 also serves as a power indicator for the external DC supply. After constructing the circuit on a veroboard, enclose it in a suitable cabinet. A small heat sink is recommended for IC1.

Circuit Design By: PRINCE PHILLIPS
Source: www.electronicsforu.com

Microphone Condenser Pre Amplifier Circuit

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This is a simple preamplifier circuit for electret condenser microphone. using a LM1458 dual op amp IC. The circuit takes the audio signal rom the condenser microphone and amplifier it, so you can use the microphone as the input to some device which wouldn’t normally accept microphone level signals .

Schematic Circuit of Microphone Electret
Condenser Pre Amplifier

The circuit requires a 6-9 volt supply. Output of the microphone amplifier can be made variable by connecting a 10kΩ potentiometer . Circuit’s gain can be increased by men perbesar the value of 47K, depending on the input sensitivity of the main amplifier system. The microphone should be housed in a small round enclosure.

List componet of condenser pre-amp mic circuit

Q1,Q2 : LM1458 Op-Amp
R1,R2,R3 : 4.7k ohm resistor
R4, R5 : 10k ohm resistor
R6,R7 : 47k ohm resistor
C1, : 0.22uF ceramic capacitor
C2 : 1uF ceramic capacitor

Absolute maximum ratings of LM 1458 IC

Supply Voltage : ±18V
Power Dissipation : 400 mW
Differential Input Voltage : ±30V
Input Voltage : ±15V 
Output Short-Circuit Duration: Continuous
Operating Temperature Range : 0°C to +70°C
Storage Temperature Range : −65°C to +150°C
Lead Temperature :(Soldering, 10 sec.) 260°C

LTC4060 - NiMH/NiCd Battery Charger Circuit

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This cheap and easy to build NiCd/NiMH Battery Charger circuit is suitable for automatically charging a wide range of batteries for many applications. This 'intelligent' charger was designed for high current and rapid charge applications such as cordless power tools and model racing cars. These battery packs are expensive and sometimes difficult to purchase. This charger uses the cell manufacturer's recommended charge method, to safely and quickly charge batteries.

Skema Rangkaian NiMH/NiCd Battery Charger

Linear Technology Corporation introduces the LTC4060, an autonomous 1- to 4-cell, 0.4A to 2A linear NiMH and NiCd battery charger. The LTC4060 includes all the functions required for a battery charger circuit. The design is simple and needs only three passive components. The LTC4060 also eliminates the need for a sense resistor and blocking diode, which increases efficiency and lowers the solution cost. This IC is targeted at applications including portable medical equipment, automotive diagnostic systems and industrial/telecom test devices.

The LTC4060 - NiMH/NiCd Battery Charger circuit Features

• Complete Fast Charger Controller for Single, 2-, 3- or 4-Series Cell NiMH/NiCd Batteries
• No Firmware or Microcontroller Required
• Termination by –∆V, Maximum Voltage or Maximum Time
• No Sense Resistor or Blocking Diode Required
• Automatic Recharge Keeps Batteries Charged
• Programmable Fast Charge Current: 0.4A to 2A
• Accurate Charge Current: ±5% at 2A
• Fast Charge Current Programmable Beyond 2A with External Sense Resistor
• Automatic Detection of Battery
• Precharge for Heavily Discharged Batteries
• Optional Temperature Qualified Charging
• Charge and AC Present Status Outputs Can Drive LED
• Automatic Sleep Mode with Input Supply Removal
• Negligible Battery Drain in Sleep Mode: <>
• Manual Shutdown
• Input Supply Range: 4.5V to 10V
• Available in 16-Lead DFN and TSSOP Packages

220V AC Ultra Bright LEDs lamp Circuit

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This ultra-bright white LED lamp works on 230V AC circuit with minimal power consumption. Ultra-bright LEDs available in the market cost Rs 8 to 15. These LEDs emit a 1000-6000mCd bright white light, like the welding arc and work on 3 volts, 10 mA. Their maximum voltage is 3.6 volts and the current is 25 mA. Anti-static precautions taken Pls Should Be handling the LEDs. The LEDs in a water-clear plastic package emit spotlight, while diffused type LEDs have a wide-angle radiation pattern.

220V AC Ultra Bright LEDs lamp Circuit

The schematics circuit of above employs capacitive reactance for limiting the current flow through the LEDs on the application of mains voltage to the circuit. We use only if a series resistor for limiting the current with mains operation. The 100-ohm, 2W resistor series avoids heavy 'inrush' During current transients. MOV at the input prevents surges or spikes, protecting the circuit. The 390-kilo-ohm, ½-watt resistor acts as a bleeder to Provide discharge path for capacitor Cx Pls mains supply is disconnected. The zener diode at the output section prevents excess levels of reverse voltage appearing across the LEDs During the negative half-cycles. During the positive half cycle, the voltage across the LEDs is limited to the zener voltage.

16-LED/46-LED combination

Aseries combination of 16 LEDs Gives a luminance (lux) equivalent of a 12W bulb. But if you have two series combinations of 23 LEDs in parallel (Total 46 LEDs), it Gives equal to a 35W light bulb.

Diode D1 (1N4007) and capacitor C1 act as rectifying and smoothing elements to Provide DC voltages to the row of LEDs. For a 16-LED row, use Cx of 12:22 μF, 630V; C1 of 22 μF, 100V; and zener of 48V, 1W. Similarly, for 46 LEDs combination use Cx of 0:47 mF, 630V; C1 of 33 μF, 150V; and zener of 69V, 1W. This circuit (inclusive of LEDs) costs Rs 200 to Rs 400.

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220V AC Operated Christmas Light Star Circuit

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Here is a simple circuit of Christmas light star that can be easily constructed even by a novice. The main advantage of this circuit is that it doesn’t require any step-down transformer or ICs.

Circuit of 220V AC Operated Christmas Light Star

Components like resistors R1 and R2, capacitors C1, C2, and C3, diodes D1 and D2, and zener ZD1 are used to develop a fairly steady 5V DC supply voltage that provides the required current to operate the multivibrator circuit and trigger triac BT136 via LED1. The multivibrator circuit is constructed using two BC548 transistors (T1 and T2) and some passive components. The frequency of the multivibrator circuit is controlled by capacitors C4 and C5 and resistors R3 through R7. The output of the multivibrator circuit is connected to transistor T3, which, in turn, drives the triac via LED1. During positive half cycles of the multivibrator’s output, transistor T3 energises triac BT136 and the lamp glows. This circuit is estimated to cost Rs 75.

Note:
This circuit directly connected to the netting of electricity, voltage 220V electricity it could sting you. Avoid working in damp and directly with ground

Circuit Design By: PRINCE PHILLIPS
Source: www.electronicsforu.com

Sound Level (Decibel) Meter Circuit

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This is a decibel meter electronic circuit, For an audio engineer, this circuit seems to be very helpful, especially for checking of sound pressure levels from about 60 to 70 Decibel (dB). EACH light represents about a 3dB change in sound level so That Pls all three lights are on, the sound level is about 4 times Greater than the level needed to light one lamp. The sensitivity cans be adjusted with the 500K pot so That one lamp comes on with a reference sound level. The other two lamps will from then indicate about a 2X and 4X increase is in volume.

Circuit of Sound Level (Decibel) Meter

In operation, with no input, the DC voltage at pins 1,2 and 3 of the op-amp will be about 4 volts, and the voltage on the (+) inputs to the 3 comparators (pins 5,10,12) will be about a half volt less due to the 1N914 diode drop. The voltage on the (-) comparator inputs will be around 5.1 and 6.5 which is set by the 560 and 750 ohm resistors.

When an audio signal is present, the 10uF capacitor connected to the diode will charge toward the peak audio level at the op-amp output at pin 1. As the volume increases, the DC voltage on the capacitor and also (+) comparator inputs will increase and the lamp will turn on when the (+) input goes above the (-) input. As the volume decreases, the capacitor discharges through the parallel 100K resistor and the lamps go out. You can change the response time with a larger or smaller capacitor.

Source: www.bowdenshobbycircuits.info

Simple Switch On Time Delay Circuit

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This Switch On Time Delay circuit has been designed to create a lamp switch operated electronically with an option of setting a delay in the time of execution of operation to reduce one or more lamps in a stairwell or any other places where this circuit may be useful. The circuit can be useful to control various lamp or appliances that can be connected in relay contacts.

Simple Switch On Time Delay Circuit

The circuit that takes advantage of the emitter/base breakdown voltage of an ordinary bi-polar transistor. The reverse connected emitter/base junction of a 2N3904 transistor is used as an 8 volt zener diode which creates a higher turn-on voltage for the Darlington connected transistor pair. Most any bi-polar transistor may be used, but the zener voltage will vary from about 6 to 9 volts depending on the particular transistor used. Time delay is roughly 7 seconds using a 47K resistor and 100uF capacitor and can be reduced by reducing the R or C values. Longer delays can be obtained with a larger capacitor, the timing resistor probably shouldn't be increased past 47K. This Switch On Time Delay circuit should work with most any 12 volt DC relay that has a coil resistance of 75 ohms or more. The 10K resistor connected across the supply provides a discharge path for the capacitor when power is turned off and is not needed if the power supply already has a bleeder resistor.

Sumber: http://www.bowdenshobbycircuits.info

Simple switch-Off Time Delay Circuit

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Designing a switch off delay circuit is quite simple and will cost you no more than $5 to make. All parts can be picked up from Radio Shack or Fry's if you have them as well as Parts Express. This will cover the mechanical aspects of it - theoretical topics can come later. If you suffer from pops on your amps or any other components, this will help you eliminate it, but it does not work in all cases.

Simple switch-Off Time Delay Circuit

Designing a swictch off delay circuit is quite simple and will cost you no more than $5 to make. All parts can be picked up from Radio Shack or Fry's if you have them as well as Parts Express. This will cover the mechanical aspects of it - theoretical topics can come later. If you suffer from pops on your amps or any other components, this will help you eliminate it, but it does not work in all cases.

The two circuits di atas illustrate opening a relay contact a short time after the ignition or ligh switch is turned off. The capacitor is charged and the relay is closed when the voltage at the diode anode rises to 12 volts. The circuit on the left is a common collector or emitter follower and has the advantage of one less part since a resistor is not needed in series with the transistor base. However the voltage across the relay coil will be two diode drops less than the supply voltage, or about 11 volts for a 12.5 volt input. The common emitter configuration on the right offers the advantage of the full supply voltage across the load for most of the delay time, which makes the relay pull-in and drop-out voltages less of a concern but requires an extra resistor in series with transistor base. The common emitter (circuit on the right) is the better circuit since the series base resistor can be selected to obtain the desired delay time whereas the capacitor must be selected for the common collector (or an additional resistor used in parallel with the capacitor).

The time delay for the common emitter will be approximately 3 time constants or 3*R*C. The capacitor/resistor values can be worked out from the relay coil current and transistor gain. For example a 120 ohm relay coil will draw 100 mA at 12 volts and assumming a transistor gain of 30, the base current will be 100/30 = 3 mA. The voltage across the resistor will be the supply voltage minus two diode drops or 12-1.4 = 10.6. The resistor value will be the voltage/current = 10.6/0.003 = 3533 or about 3.6K. The capacitor value for a 15 second delay will be 15/3R = 1327 uF. We can use a standard 1000 uF capacitor and increase the resistor proportionally to get 15 seconds.

Source: bowdenshobbycircuits.info

IC 555 Monostable Circuit

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Monostable circuit produces one pulse of a set length in response to a trigger input Such as a push button. The output of the circuit stays in the low state Until there is a trigger input, Hence the name "monostable" meaning "one stable state".

This type of circuit is ideal for use in a "push to operate" system for a model displayed at EXHIBITIONS. A visitor cans push a button to start a model's mechanism, moving, and the mechanism will from automatically switches off after a set time.

The circuit diagram of the 555 monostable circuit is given as follows.

Monostable Using IC 555 Circuit

IC 555 Pinout

Note:

• resistor value R and the capacitor value C are unspecified. The values of these components determine the length of time that the monostable output is in the high state, and they may be calculated using the equation below
• T = 1.1RC or R = T/1.1C
  

In the monostable mode, the timer 555 acts as a "one-shot" pulse generator. The pulse Begins Pls the 555 timer receives a signal at the trigger input That falls below a third of the voltage supply. The width of the output pulse is determined by the time constant of an RC network, the which consists of a capacitor (C) and a resistor (R). The output pulse ends Pls the charge on the C equals 2 / 3 of the supply voltage. The output pulse width cans be lengthened or shortened to the need of the specific application by adjusting the values of R and C