Car Amplifier Schematic

The design of Car Amplifier Schematic is made by Mr. T.Giesberts. The article consist of 13 pages. If you read them till finish, you will be able to make yourself car amplifier.This Project is “Car amplifier” and its basic parts- SMPS, Amplifier, Preamplifier and Protection circuit witch are based on originally schematic from service manual of Kenwood Auto amplifier KAC-716.
I've work on this project about five mounts and it WORKS.
From originally schematic of KAC-716, I have produced PCB’s separately for SMPS, Amplifier, Preamplifier and Protection sow it can be develop extremely effortless.
All electronics capacitor from Amplifier, Preamplifier and Protection are 50 volts range. Input capacitors 2x 3300uf/16volts and output capacitors 2x2200uf/50volts and additionally 2x1500uf/50volts need to have 105 C temperature ranges.
All documents are in PDF format and JPEG. The PCB’s are in original sizes.
The SMPS isn't regulated so the output voltage will depend on turns ratio in ferrite core. I used 2 x 4 turn’s primary wire and for second it depends of why high will likely be the output voltage.
By choosing a appropriate resistance for resistor R222/1W connected with pin 6 of UPC1237 we should set up maximum current of 80mA. The valley of R222 depends of internal resistance of relay and supply. For much better calculation download the datasheet for UPC1237 form Internet-Read the note for utilizing UPC1237 and you are able to recognize what kind of other protections are given from this IC’s and employed in this style.

There are many designs of good amplifier published, solid state (SS) or tube designs. But few have written the design of car power amplifierActually the difficulty of designing the car power amplifier does not lies with the audio power amplifier, but it is more to providing the switching power supply.As we knows, the output power of any audio power amplifier is approached by formula :

P = Vpp2/(8*Rl)

where Vpp= peak to peak supply voltage, Rl is the speaker impedance load. For car voltage of 12Vdc, if we connect it to 4 Ohm speakers we will only have power of 144/32 = 4,5 Watt.Bridging the amplifier will double the power, but will never be more than 40 W.

If we want to make more powerful amplifier, lets say 170 watt at 4 ohm speaker load, we will need supply voltage of 74Vpp, or +/- 37 Vdc. The way to have this voltage from car supply of 12VDC is to make DC-DC converter.
In this article, I will discussed the car power amplifier in 3 steps :

1. The design of audio power amplifier

2. The design of DC-DC converter

3. Miscellenous tips for making car power amplifier.


In fig1 we can see that audio power amplifier can be splitted into 3 main functions, that is:

- First stage / input stage

- Second stage / voltage amplifier stage

- Third stage / output stage

First stage is the stage that receives the input audio signal and Negative Feedback (NFB) signal from the output of the amp. Feedback is the back signal used to stabilized the audio amplifier, like the gain factor. For first stage built by discrete transistors, both signals is fed to basis of the transistor, like in fig1. Both basis of the transistors is the Non- Inverting input and Inverting Input, like those in the op-amp.Second stage is the stage that responsibles for the Voltage Gain in the power amplifier.

Third stage is the Current Gain.

We can explain those stages in a simple way like this : Input signal, like from car radio or CD player have low voltage, about 1Vpp with few milliampere current. To produce power of 170 Watt at 4 ohm speaker load, than the signal has to have maginitude of 28Vpp and current of 6.5A (from the equation of P=I2*R = V2/R)

The first stage receives this signal in the non-inverting input and the inverting input receives NFB signal to make sure the voltage gain that the amplifier produces has a constant number, lets say 28 x. The output signal from the first stage has not reach 28Vpp, it tends to have the magnitude similiar to the input voltage. Second stage amplifies the voltage that the first stage generates. Second stage will amplifies the voltage to produce a signal that is enlarge 28x for the amplifier to have a 28Vpp signal from 1Vpp signal, but this 28Vpp signal still have small current , only a few mA and cannot drive the speaker load. The third stage amplifies the current from few mA to 6.5 A.

Offcourse the explenation for three stages above is not that simple in the real amplifier. We should take the nature's law for a transistor gain, that is G=RC/RE. This principles must be applied in each transistor in those 3 amplifier stages.


First stage designs have main component, that is Constant Current Source (CCS) which can be seen in fig2. One of the basic of electronic law that works on every circuit is that the voltage drop of Basis and Emitor (Vbe) equals the drop voltage of one dioda = 0.67V. It can be seen in fig2 that the voltage drop of 2 dioda IN4148 = 2 x 0.67V = 1,34V. We can see in RE and Q1, then V=0,67 is substracted by Vbe of Q1 and the other 0,67V will be the drop of RE. So we will have a Constant Current Source of 0,67/RE. In fig2 the Ic is = 4,4mA. CCS first stage varies between 1-4mA.

In fig1 first stage, each component will be explained like this:

- R1 is the impedance of the audio amplifier, the range is 10 Kohm – 47Kohm

- C1 is the highpass filter from the equation : Fhp = 1/(2 x pi x R1 x C1)

- RED1 and RED2 is between 50-150 ohm

- RM1 and RM2 is picked up so the voltage drop will be 50mV – 150mV

- Q3 and Q4 is the Current Mirror that ensures the current in RM1 and RM2 will have the same magnitude.

- RF and CF will be discussed later.

Before we discuss Second Stage and Third stage, first we will discuss the amplifying effect of a transistor. In fig3a we will see a circuit of Common Emitor Mode (CEM). This circuit will amplifies the voltage. In fig3b we see a Common Colector Mode (CCM). This circuit is the current amplifier without voltage amplifier. So if we want to amplifies voltage we use CEM circuit and to amplifies current we use CCM circuit.


The Second stage responsibles for all voltage gain (Maximum Voltage Swing) in an audio power amplifier. This is why the Second stage is generally known as VAS or Voltage Amplifier Stage. This stage consist of a voltage amplifier/CEM transistor(Q5 in fig1) in the bottom, Constant Current Source in the top, and a bias control circuit in the middle. Second stage CCS has current magnitude between 4-8mA

In the second stage there is an important capacitor for an audio power amplifier , that is Miller Capacitor (CC in fig1). CC defines the pole of the frequency response for an audio amplifier and the magnitude usually in small order (severalpF).

Bias control circuit consist of a transistor, resistor and a VR like in fig5. This circuit uses a transistor that is placed in the heatsink, because the transistor have good heat compensation factor (for bipolar transistors). For the amplifier that uses mosfet transistor for the final device, the bias circuit only needs potentio or dioda only because mosfets have different heat characteristic than bipolar transistors. The bias voltage magnitude depends on the type of the third stage used, which will be discussed later.


Third stage / Output Stage is the current amplifier. Third stage and the bias circuit will defines whether an amplifier works in class A, class AB or class B.

It can be said that almost 90 % of car audio power amplifier works in class B. Operation in class B does not mean that the sound produced is not good or corrupted. With good design, we will have good audio results, both from class A or class B. The choice of class B in car audio power amplifier is conected to efficiency and the heat generated. Heat generated is a very important factor, because if not considered carefully, it will lead to amplifier breakdown.

Many configurations of the output stage can be seen in fig4. Each configuration has different optimum bias voltage. It depends on how many Vbe's that have to be passed. Example : In fig4(a) the signal has to pass 4 Vbe's, which is Vbe Q1, Q3, Q4 and Q2. So the optimum bias = 4 x 0.67V = 2.8V.

Both 3 stages that we have discussed above, if we connect the together will be a circuit that can be seen in fig5. Parts of this circuit can be explained like this:

- The value of Negative Feedback (NFB) resistor is determined by determining the gain factor with the equation : Gain = 1+(R10/R8) = 1+10k/500 = 21 x. The value of R10 = value of R1 to balance input. R20 and C7 are the pole and slope compensator.

- C2 limits the DC gain factor, value ranging from 47-220 uF, usually using a nonpolar capacitor.

- R21, R22 and C11 will stabilize CCS. Here we use CCS with 2 transistor system,but the equation used still the same, that is Ic = 0,67/RE .

- The output of differential pair tapped from collector of T10 and send to VAS which is built by T12 and T4. This configuration is called Darlington VAS and the value of R8 is standard.

- C3 is the Miller capacitor with value of 100pF.

- C5 is called Speed Up Capacitor. Several designs do not use this capacitor

- R18, C6,L1 and R19 are output power stabilisator. If there is any oscilation occur in the audio power amplifier, the first tobe effected is R18 besides the final transistors.

Car Power amplifier usually loaded by low impedance speakers, usually 4 ohms and can reach ½ ohm on bridge mode. Here we know the term “High Current Amplifier”. The difference is the number of final transistors, or in fig5 it is the number of pairs of T7 and T8. As a rule of thumb, the number of transistor needed first has tobe calculated by equations above, and then we determine the number of final transistor needed with assumption that 1 transistor can handle 50 Watt output. A pair of bipolar transistor can handle 100 Watt. The power is raised by parrarelling several output transistors, so the currrent flowing will be larger. For large number of final transistors, we change the predriver stage with darlington configuration.

Several designs uses symetrical design, like those used in AXL and Crescendo schematic. this design is developed from the basic principal above, but the signal handling for + and - part is handled by complementary circuits.

I have an example about another kind of power amplifier, that is a non-feedback amplifier. You can view the principles of the "millenium power amplifier" in the . This amplifier has a certain gain factor in first and second stage, while the third stage is only current amplifier.


For building car power amplifier, we need symmetrical power supply (+, 0, -) by building DC-DC converter. The converter system discussed below will be the SMPS(Switch Mode Power Supply) type PWM (Pulse Width Modulation). This system will deliver stable output voltage, regardless of the input voltage (usually the car electrical system will range in 9-15Vdc).

To explain the SMPS type PWM, it can be analogued by the next example. Look at fig6. There is a voltage pulse V1 on-off with 50% wide. These pulses if passed through suitable L and C filter will be transformated into straight voltage of V2 which is V2 = ½ V1. (noticed the marked area below pulsed V1 is the same total area of the marked straight V2 ). With the same logic, if the pulse width of V1 is narrowed, we will have a lower V2 and if we enlarge the width of V1 pulse, we will have higher V2. Some may ask, how can we get 30VDC from the car's 12VDC? The answer is simple. If we get the V1 voltage to 60VDC, then in the 50% duty cycle, we will get 30VDC straight. This is the part where the power switching transformer takes control, to make the 60VDC from 12VDC, and then chopped by the PWM. This is the princip of PWM. (Like the principal of class D digital power amplifier). In this design, we use regulating PWM IC's, like TL494, TL594, SG3524, SG3525. These IC's will compare the output of DC-DC converter with a reference voltage. If the output of DC-DC converter is smaller than reference voltage, then the IC will enlarge the pulse width so the voltage will raise equally to to reach determined voltage. So as if the output of DC-DC converter is higher than the reference voltage, the IC will narrow the pulse width so the output voltage will be lowered to the determined voltage.

Generally SMPS used in car audio amplifier is the push-pull system with switching frequency between 20-70Khz. In push pull sytem like in fig7, Q1 and Q2 gives alternating switched current pulses so the transformator will be objected to maximum flux swing change without saturating the core.

In this design we will use PWM IC with SG3524 from SGS Thompson. Specifications can be seen in SGS Thompson's website. Fig8 shows the configuration of 16 pins on this IC. To make is simpler, lets design a SMPS by explaining the function of each pin.

For the stereo power amplifier in fig5, we will need a SMPS 12Vdc input and summetrical output of +/- 37Vdc with 8A rating.

1. First we make the Remote Turn On circuit , which is connected from the car radio / CD player. The circuit can be seen in fig9a. This circuit will turn on the SMPS by giving 12Vdc to pin 12, pin 13 and pin 15.

2. The SMPS switching frequency is determined 50Khz. For this, the clock inside IC SG3524 is adjusted 2 x 50 Khz = 100Khz. This clock is built up by pin 7(Ct) and pin 6(Rt). The approach can be done with equation Fclk = 1 /(Rt x Ct). Here we use Ct = 1nF and Rt = 10Kohm like in fig9b

3. Pin 2(Non Inv In). In pin 2 we put stable reverence output for the SMPS. Here we use reference voltage of ½ from reference pin 16.

4. Pin 1(Inv In) is the output voltage detector . Pin 1 is connected to the optoisolator type 4N35 like in fig9b. Optoisolator is an important component in making this SMPS so we can have Floating Secondary Ground which will prevent noises (especially whine/storing) if the power amplifier is placed in car. The value of zener diode is 2 x 37V = 74V. If it is difficult to have zener voltage of 74 V, then we can series several zener values until we have total of 74 V.

5. Pin (4) and pin(5) are not used and connected to ground, pin(8) and pin(10) connected directly with ground.

6. Pin no 9(Comp) determines slope and pole of feedback from the whole SMPS system. In this design we use only 1 capacitor of 100nF.

7. Pin no 16(Vref) gives reverence voltage of 5,1 Vdc . This pin is placed with 10nF as a voltage stabilisator.

8. The output ripple (Vr) of the SMPS is determined by equation :

Vr = 8 x 10-6 x I / Co. With I = 8A and Vr = 0,029V we will have Co of 2.200uF in +37Vdc ->-37Vdc rail or 4400uF each in +37Vdc_0 and 4.400uF in 0_-37Vdc.

9. For output filter capacitor of 2.200uF, we will need approximately 4x 2.200uF or 8.800uF in the SMPS's input 12Vdc . The larger the value of this capacitor, more energy stored for the SMPS.

10. Output filter inductor Lo is determine by : Lo = 0,5 x Vout/ (I x F). With Vout = 2 x 37V = 74V, I = 8A dan F = 50Khz, we will have Lo = 0,092mH or Lo = 0,046mH on each supply rail + and – 37Vdc.

11. Pin 11 and pin 14 are output pins that will drive the primary winding switching mosfets. Inside IC SG3524 both pins have already opereated in mode push-pull. The circuit for driving power mosfets can be seen in fig9b. The number of power mosfet used is 3 in each transformator primary. So total there is 6 power mosfets type BUZ11.

12. Transformator(trafo) for SMPS is selfwould from ferrite toroidal core (like donuts) like in fig10. It is very important that for SMPS frequency above 20Khz, we cannot use iron core transformator like we use in homes. The ferite core transformator will have black color like in the speaker magnets, but do not have magnetizing force. The basic of equation for switching power supply with 12Vdc input is:

(1) Np = 1,37 x 105 / (F x Ae), where Np= primary number of turns, F = switching frequency, Ae = X x Y = window area of ferrite in cm2. Look at fig10. To make it easy to wound the transformator, we will have to choose the toroid core with minimal diameter of 2,5 cm and window area minimal of 0.75cm2.This is necessary for the easyness of self handwound. Remember that in push-pull system there is 2 primary windings.

(2) Ns/Np = Vo/8,8, where Ns = secondary number of turns, Vo = secondary output voltage

(3) Ap = 0,004 x Vo x Io, where Ap = window area of primary wire in mm2, Vo = output voltage, Io = output current.

(4) As = 0,13 x Io, where As = window area of secondary wire in mm2.

Example : If we use toroidal ferrite core with window area of Ae = 1 cm2. then from equation no. 1 we will have number of primary turn Np = 1,37 x 105 / (50Khz x 1 cm2) = 2,74 turns. In practice, number of minimal primary turns is 4 so the primary will cover the whole toroidal core. So we use 4 turns for Q1 and 4 turns for Q2.

From equation (2) we have that Ns/Np = 37/8.8 = 4,2. From here we can calculate that the number of secondary windings is = Np x Np/Ns = 4 x 4,2 = 16,8 or 17 windings. Like the primary, in secondary we use 2 x 17 turns, that is 17 turns for +37V –> 0 and 17 turns for 0-> -37V

Equation (3) is used tp determine the number of primary winding wires. We have Ap = 0,004 x 74 x 8 = 2,36mm2. If we use a 1mm diameter magnet wire, we will have window area of 0,785mm2 so we will need 3 wire magnets for each primary windings

Equation (4) is used to determine the number of wire needed for secondary windings. We have As = 0,13 x 8 = 1mm2 So if we use wire magnet with diameter of 0,8mm(window area = 0, 5mm2), then we will need 2 wires with diameter 0,8mm for each secondary windings.

13. The secondary output voltage is rectified by full bridge configuration like in fig11. Bridging diode must be the type of fast rectifier, usually looks like transistor TO220 with plate heatsink. For SMPS we cannot use ordinary 50/60Hz rectifier diode. For this design we use diode type BYW29-150, which have rating of 8A, 150V. We can also use other diodes like with prefixes FE…,MUR..., as long as it is a fast rectifier diode with minimal specification like above.
This is Power Acoustik PCX-30F
30.0 Farad hybrid digital power capacitor
24V DC foil-carbon internal capacitor
Digital blue voltage display
Tinted plexiglas with blue LED lights inside for viewing
Electronics polarity circuit
Over voltage protection circuit
Platinum plated ring terminals
Satin finish with chrome end caps and mounting brackets
Authorized Internet Dealer
1-year Manufacturer's warranty
Product Summary
Manufacturer: Power Acoustik
Model number: PCX-30F
UPC: 709483028005
Weight: 7.00 lbs
Internal SKU: pcx30f
Internal Product ID: 12024Power Acoustik PCX-30F
Power Acoustik PCX-30F
some told methat he can drive 4 hours without an alternator, is it possible
Id also go with no...but who knows Ive driven only 30 miles with no alternator...didnt seem to do the battery real harm but I remember when I was trying to trace the reason why my alternator wasnt charging the battery when I shorted the terminals I turned my car on and off about 8 times and left it running for more than 45 mins with only a .5 voltage drop amps unhooked...and idling all for about 4 mins..
Shunt compensators for harmonic compensation, load balancing and power factor correction have been proposed within the literature. The compensator consists of a VSI operated as a present source using hysteresis band current control. Numerous methods for generation of reference compensator currents have been used, e.g. the theory of instantaneous symmetrical components, instantaneous pq theory, etc. A considerable problem in these compensators that has two or much more capacitors is the capacitor voltage unbalance and drift because of the DC component of the current inside the neutral path. This degrades the tracking performance of the VSI and should be corrected. The paper describes an inverter chopper configuration and the various control methods to regulate the capacitor voltages to a reference value. The operation of the program has been verified via simulation of a 440 V, 3-phase program supplying unbalanced 3-phase R-L load and 3-phase half wave rectifiers. Detailed simulation outcomes utilizing MATLAB have been given
12 volt to 12, 15, 18, 21, or 24 DC DC Boost Converter (Adjustable DC DC regulator) Price $19.95 each.
PST-DC2171 1-10 11-50 51-100 100+
Price $19.95

Model Number PST-DC2171 DC DC Converter
Input Voltage Range 10 VDC to 14 VDC (see chart below)
Peak Output Power 50 Watts (see chart below)
Peak Output Current 2.5 Amps
Output Voltage Nominal Adjustable 12, 15, 18, 21, 24 Volts DC
Output Voltage Typical See chart below
No-Load Overhead 15 mA
Dimensions 122 x 76 x 60 mm
Fuse 10A fuse in cigarette lighter plug
Input cord 8 inch zip cord with cigarette lighter plug
Output cord 6 foot zip cord with 6 interchangeable adapters
Agency Approvals CE e4 approved

Test Data
Voltage Setting Typical
Voltage Used on Equipment Requiring* Minimum
Input V Maximum Input Voltage for regulation Maximum
Output A Efficiency
at 2.5 Amps,
12 Volts Input Line
Regulation at 1 Amp Load
at 12 V input No-Load
at 12 V input
12 Volts 12.5 V 4.5 volts 10.5 volts 2.5 Amps
15 Volts 15.5 V 4.5 volts 16 volts 2.5 Amps
18 Volts 18.5 V 4.5 volts 19.3 volts 2.5 Amps
21 Volts 21.7 4.5 volts 21.6 volts 2.5 Amps
24 Volts 23.1 - 24.3 V 4.5 volts 24.8 volts 2.5 Amps
the shema of 12volt to 16volt car adaptor scheme A 16 volt battery system requires a charging system that exceeds 18 volts 18+ volts will start frying most automotive electrical components
Most 16 volt systems are separated or isolated from the vehicles electrical systems
Turbo start use to make a 16 volt battery with 12 volt output post for the vehicles system
I’m nor aware of another battery with this 12 volt output.
A 16+ volt system is a expensive project; over 1,000.00
line follower robots are robots that can move to follow the line in the AUTO In fact, if readers are googling, lots of tutorials to make robots line follower on the internet, but almost all of them complicated and use a microcontroller that has not been understood by the boys' high school is much comment in my previous posting. .. Below are examples of line follower robot.

Rangkian Robot Line Follower Sederhana
Connect the battery or adapter with this audio mixer circuit. Enter Casset deck, or microphone output at input A1. Slowly rotate P1 toward maximum until the loudest sound was obtained but not broken. After that turn slowly toward a maximum until P4 obtained loudest sound but not broken. The same process performed on the input A2, A3.

Do not forget the time adjustment of S123 in the open position (ON position). After adjustment is complete, do not be amended again except P456 P123 that serves as a volume.

This audio mixer output can be connected to other recording media such as tape recorders, Cassette recorders, computers and much more. In addition, with the two LM 3900 you can have 6 channel audio mixer. Enough to build a simple studio and receive orders.
Fig circuit above can be applied to create an adapter or power suplly with the output voltage (V DC 12V output). Power supply above will only be protected by a capacitor as a safety when the power supply is connected with the burden on the circuit. Therefore recommended to use 35V capacitor with a minimum specification. To power the power supply more security we can menggunakkan TIP transistors, but I have yet to discuss it. For the diode bridge can be collated from four diodes then you solder into a bridge rectifier or you can buy a comb-shaped bridge rectifier (sideways) or the box. At least I would suggest using the diode bridge 1 Ampere, in a series adapter, the bigger the better way ampere diode currents in the circuit. Diodes like highways, and flow as the car passed. The larger and the width of existing highways, the faster the flow of runs and through the circuit.

For the 5 V power supply circuit, you can replace the above-volt regulator with the type 7805 and 7905. This application applies equally in this circuit. For variations, such as fuse or circuit switch on / off you can try yourself.
Skema Rangkaian Adaptor
There are two types of amplifier circuit that we often hear that the amplifier inverting (flipping) and Non-inverting (no reverse). For the circuit above is the type of inverting amplifier circuit. The above amplifier circuit using the IC which is often used and easy to find the op-amp IC LM741. To more easily understand the working principle of this amplifier circuit is deliberately examplize circuit is quite simple. Because by being able to understand the working principle of this circuit you will be able to easily understand the development of a series of Op-Amp rangakaian this as ADC (Analog to Digital Converter), DAC (Digital to Analog Converter), summing (sum) and others.

In the circuit on the input signals to be strengthened is one volt AC signal with a frequency of 1 Hz. The amount of amplified gain is divided by the input resistance of strengthening prisoners-R5 / R4 = -30/10 = -3. To determine the voltage gain of the output is x Vin = -3 x 1 volt = -3 volts. The minus sign shows the opposite phase with the input signal. This means that if the input signal is positive, the output signal will negatiif and if the input signal the output signal is negative then positive. For details try to notice the picture above input and output signals. The input signal is red and blue output signals. Vertical lines indicate the voltage and the horizontal line indicates the time. Signal input voltage 1 volt at the position (Vpuncak = 1V2 volts) and the output voltage is 3 volts (Vpuncak = 3V2 volts) are consistent with the strengthening of which is 3 times larger than the input signal.
Rangkaian Penguat Inverting Gambar
Light sensor circuit according to me is a series of sensors are the easiest and most often used as an experiment. Because with a little can make a component of this series, and its components easily available in the market. As with other series switching transistor circuit above also apply the basic principles of the saturated and cutoff transistors. To obtain a more accurate circuit and perfect could be using IC op-Amp.

In the above picture there are two conditions that the application of the light sensor when the bright lights and the lights on when dark. It should be understood from the above series is how we position the amount of current that will be received by the base of the transistor by utilizing the VR (variable resistor) as a determinant.
Rangkaian Sensor Cahaya Dengan LDR
Note the picture Below, when the switch SW1 is pressed and released back then obtained by the same signal as the signal in the image above. Initially when SW1 is connected with the supply voltage, the capacitor will charge quickly. Then when SW1 is released charge on the capacitor will be used by the inductor as the supply voltage. In accordance with the general nature of the inductor that the DC signal will be considered ordinary wire inductor such that current flowing through the inductor and fast charge on the capacitor decreases rapidly running out. Uniquely currents were flowing through the inductor and capacitor will fill the empty capacitor back through the other terminal (negative cycle). Kapasior rapid filling, then return to inductor will burden the load discharge occurs again. That so happens repeatedly (resonance occurs between L and C) until the electrical charge was used up by these two components in power losses. Equations between regular wire inductor is the inductor with wire work as usual at the time of her current flows in the same direction. Inductor, wire But unlike ordinary moment in an alternating current flows back to him. So it will not happen short circuit if the inductor to get the supply voltage alternating current (AC). But in ordinary wire short circuit will still occur even if the voltage is alternating current.
Rangkaian Resonansi LC Gambar
How Principle circuit Frequency Estimator work

Workings of frequency above the measuring circuit is actually very easy to understand. You should not be fooled by the number of components used. Circuit above looks more crowded because of the support series for seven segment display and a timer or a monostable circuit. The above series of works that deliberately use a timer set for the time period 1 (one) second. While the number of frequencies used to calculate the positive cycle of input signal itself. Where the input signal is used as a clock counter circuit. Then a second timer signal from the monostable circuit logic is then multiplied by the input signal using an AND gate. So that when the signal from the monostable logic high for one second, then the input clock counter circuits will get the same logic as in the measurement input signal. But after one second signal from the monostable will be worth 0 volts so that the frequency calculation is stopped.

Frequency counter circuit above is an example of a very simple and is applicable to the measurement signals that have a 3-volt voltage to 9 volts. While for the voltage measurement is less than 3 volts will be read by a logic AND gate as low despite the swing signals. Then the voltage is too large will also be able to cause damage to the circuit.
My Zimbio
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