High Voltage Meter or Probe Design

Common voltmeters, digital or analog, usually range to some hundred volts maximum. Higher voltages not only cannot be indicated, but will also destroy the instrument. However, the range of any voltmeter can easily be extended using extra series resistance, as shown in the figure. Calculating the necessary resistance implies knowledge of the input impedance of the voltmeter.

Circuit and formula for constructing high voltage probes. For example, let's assume we want to extend the range of a standard digital voltmeter (input impedance 10MOhm) to 100kV. The maximum DC voltage the meter can take is 1000V. This means we need an external 1GOhm high voltage resistor in series with the meter. The total voltage ios given by the value indicatedby the meter, times 100. If we wanted to read the voltage in kV directly, we would need a resistor 1000 times as large as the input impedance of the voltmeter, i.e. 10GOhm.

Such home-brew high voltage probes are good for DC only. For AC voltages, capacitive input impedance of the meter and capacity of the probe must be matched, which is difficult to achieve because of parasitic capacitance of the resistor chain. A few pF (the capacitance of a 1cm radius metallic sphere) make a big difference, especially at higher frequencies.

Source: kronjaeger.com

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Rangkaian Transistor Tester

The circuit shown below is a simple circuit transistor tester. In some digital and analog avometer now mostly been contained this feature, but it can not hurt us a little more creative. This circuit can also be used to detect whether a transistor is NPN / PNP.

Skema Rangkaian Transistor Tester

Circuit operation is as follows. The 555 timer is set up as a multi-vibrator 12hz. The output on pin 3 drives the 4027 flip-flop. This flip-flop divides the input frequency by two and delivers complementary voltage outputs to pin 15 and 14. The outputs are connected to LED1 and LED2 through the current limiting resistor R3. The LED's are Arranged so Pls That the polarity across the circuit is one way only one LED will from light and Pls the polarity reverses the other LED light earnest, therefore Pls no transistor is connected to the tester the LED's will from alternately flash. Also The 4027 outputs are connected to resistors R4 and R5 with the junction of these two resistors connected to the base of the transistor being tested. With a good transistor connected to the tester, the transistor will of turn on and Produce a short across the LED pair. If a good NPN transistor is connected then LED1 will from flash by Itself and if a good PNP transistor is connected then LED2 will from flash by Itself. If the transistor is open both LED's will from flash and if the transistor is shorted then neither LED will from flash.

IC NE555 Pinout

IC 4027 Pinout

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Rangkaian Regulator Variable Sederhana

Regulator Variable Sederhana

A simple but less efficient method of controlling a DC voltage is to use a voltage divider and transistor emitter follower configuration. The figure below illustrates using a 1K pot to set the base voltage of a medium power NPN transistor.

Skema Rangkaian Regulator Variable Sederhana

The collector of the NPN feeds the base of a larger PNP power transistor which supplies most of the current to the load. The output voltage will be about 0.7 volts below the voltage of the wiper of the 1K pot so the output can be adjusted from 0 to the full supply voltage minus 0.7 volts. Using two transistors provides a current gain of around 1000 or more so that only a couple milliamps of current is drawn from the voltage divider to supply a couple amps of current at the output.

Note that this circuit is much less efficient than the 555 timer dimmer circuit using a variabe duty cycle switching approach. A fairly large heat sink is required to prevent the PNP power transistor from overheating. The advantage of the circuit is simplicity, and also that it doesn't generate any RF interference as a switching regulator does. The circuit can be used as a voltage regulator if the input voltage remains constant.

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Simple switch-Off Time Delay Circuit

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

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Simple Switch On Time Delay Circuit

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

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9 Second Countdown Power-On Relay With 7 segment Display

9 Second Countdown Power-On Relay Circuit

This circuit provides a 9 second delay using a 7 segment display. When the switch is closed, the CD4010 up/down counter is preset to 9 and the 555 timer is disabled with the output held high. When the switch is opened, the timer produces an approximate 1 second clock signal, decrementing the counter until the 0 count is reached. When the zero count is reached, the 'carry out' signal at pin 7 of the counter moves low, energizing the 12 volt relay and stopping the clock with a low signal on the reset line (pin 4). The relay will remain energized until the switch is again closed, resetting the counter to 9. The 1 second clock signal from the 555 timer can be adjusted slightly longer or shorter by increasing or decreasing the resistor value at pin 3 of the timer.

Note:

• The circuit can be powered from a 9V PP3 battery or 12V DC power supply.
• The time delay can be varied by replace the resistor value at pin 3 IC555.
• The push button switch is for starting the timer.
• The appliance can be connected via contacts relay.

Source: bowdenshobbycircuits.info

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Driver Relay Menggunkan Transistor

Basic Transistor relay driver

Bipolar transistor is a component that works based on the presence or absence of flow in the foot triggers the base. In the relay driver applications, the transistor works as a switch that at the time did not accept the current triggers, then the transistor will be in the position of the cut-off and does not conduct current, Ic = 0. And when the base receives the flow triggers, then the transistor will turn into a state of saturation and delivers current. The following is a practical circuit of relay drivers that are reliable for use in microcontroller projects.

Skema Rangkaian Driver Relay
Menggunkan Transistor

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

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Rangkaian Ampere Meter Digital

This is a circuit of a digital ampere meter with 4 digit LED 7-segment display, the circuit capable of measuring the current consumption up to 10A with selected 100mA, 10mA and 1mA accuracy, and consumes only about 25mA of current. The ammeter is based on single ICL7107 chip and 3.5-digit seven segment LED displays. Due to a Relatively small number of components That the circuit is using it is possible to fit it on a small 3cm x 7cm printed circuit board.

Skema Rangkaian Ampere Meter Digital

0.01 Ohm resistor should be made out of 1.5mm thick / 5cm long copper wire. 0.1 Ohm and 1 Ohm resistors should have 5W ratings.

For highest accuracy it is recommended that the ICL7107 ampere meter module should be supplied with its own voltage supply. If measurement of the current of the same supply is needed, ICL7107 ampere meter would have to sample negative not positive voltage supply.

Brightness of the LED displays can be varied by adding or removing 1N4148 small signal diodes that are connected in series. Use two 1N4148 diodes for higher brightness.

Also, the use of 7805 5V voltage regulator is highly recommended to prevent the damage of ICL7107 and 7660 ICs. .

Source: http://electronics-diy.com

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Power Meter Schematic For Audio Amplifier

This is a simple schematic of audio power meter using LM3915 IC, this schematic can be used to measure the actual output power of your amplifier. For an audio engineer, this schematic Seems to be very helpful, especially for checking of sound system installation and field testing. Due to its logarithmic scale, the wide range of audio output with only ten scales cans Also be measured. If you take an attention to the pin number 5 of the LM3915, see That you will from the input is not yet Rectified. At this input pin, the negative swing will from the present. However, it is harmless since the current is limited by R1, the LM3915 earnest therefore respond only to positive cycle.

Schematic of Power Meter For Audio Amplifier

Note:

When the speaker resistance is 4Ω, then, make R1=10kΩ, if the resistance of speaker is 8Ω, make R1=8kΩ, and if the resistance of speaker is 16Ω, make R1=30kΩ.

The absence of peak detector or the detector will of averages give the circuit a fast reading of instantenous power, and this Gives us insight of both average and peak condition. For more readable peak or average mesurement, you cans use peak or average detector circuit.

source : national semiconductor application notes

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Sound Level (Decibel) Meter Circuit

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

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220V AC Operated Christmas Light Star Circuit

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

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220V AC Ultra Bright LEDs lamp Circuit

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.

Source

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LTC4060 - NiMH/NiCd Battery Charger Circuit

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

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Rangkaian 50Hz Accurate Oscillator

This circuit is a getting a 50Hz pulse. The oscillator circuit need only provide the IC ELM446, crystal and two appropriate loading capacitors

Skema Rangkaian 50Hz Accurate Oscillator

Note:

• for greater accuracy as usual, it is also good practice to place a bypass capacitor across the power supply as well

The IC ELM446 is an 8 pin digital divider integrated circuit, that provides both 50Hz and 1Hz outputs from a common 3.58MHz NTSC colourburst crystal. Externally, the designer need only provide the crystal and two appropriate loading capacitors, as well as a suitably bypassed power supply. Internal Oscillator circuits then use this reference frequency to precisely derive a stable 50Hz signal. For convenience, a complementary 50Hz signal is also provided. This signal is then further divided to provide a 1Hz signal output. By ELM Electronics

This is pinout of IC ELM446, If you need more detail please download ELM446's pdf datasheet.

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Microphone Condenser Pre Amplifier Circuit

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

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Mobile Phone Battery Charger Circuit

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

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