Mixed acoustic connection to an amplifier with two bridge output channels

Consider the circuit connection to the AC amplifier with two bridge output channels. Dynamic head BA1, BA2 speakers form the left and right stereo channels. They are shown conventionally broadband. Low-frequency head BA3 is connected between the output of the amplifier left and right channels, the signals are summed and head reproduces a mono signal.

This connection will be sure to have two high-pass and low-pass filter for the stereo for the total channel. Their mission - to eliminate the parallel operation and overload amplifier heads. Usually used for stereo first order filters (C1, C2), for the total - the second (C3L1) or third.Their payment is made in the usual way. Crossover frequency of the LPF and the order chosen in the range 80 ... 200 Hz, depending on the location of the low-frequency head. If it is placed in the rear compartment, the crossover frequency should be selected as low as possible, and the order - up to avoid reproducing the subwoofer "voice" of the range. However, this requires the manufacture of relatively large inductors.Used in their construction ferromagnetic yokes undesirable because the distortion caused by the inevitable core magnetization significantly degrade sound quality.

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FAQ on the speakers and subwoofer

Introduction

Recently could hear a lot of questions about speakers and subwoofers. The vast majority of responses can be found on the first three pages of any book written by professionals. Material is addressed primarily to beginners, lazy ;) and rural Homebrew, prepared on the basis of books I.A.Aldoschinoy, V.K.Ioffe partly Ephrussi, journal publications in Wireless Worrld, AM and (some) personal experience. NOT used information from the Internet and Fidonet. The material is in no way purport to lighting problems, and is an attempt to explain the basics of acoustics on the fingers.

Most often, the question goes something like this: "the speaker found that to do with it?" Or "tovarischch and say such subwoofers are>." Here we consider only one solution to this problem: For existing dynamics to make a box, with the optimal settings for HCH as possible. This option differs from the task factory designer-pull system to lower the frequency of the required quantity of TU

[Q] Hashel large speaker on the occasion unmarked. How to know whether you can make him a subwoofer?

[A] Hujno measure its T / S parameters. Ha Based on these data to decide on the form of HCH clearance.

[Q] What is the T / S parameters?

[A] The minimum set of parameters for the calculation of HCH design proposed by Till and Small.

Fs-resonant frequency of the speaker without registration

Q factor Qts-full dynamics

Vas-equivalent volume of the speaker.

[Q] How to measure the T / S parameters?

[A] To do this, you need to collect from the generator circuit, a voltmeter, a resistor, and the test speaker. The speaker is connected to the output of the generator with an output voltage of several volts across the resistor of about 1 kOhm.

1. Remove V (F) = AFC resistance dynamics in the resonance region. The speaker must during this measurement to be in the free space (the distance from the reflecting surfaces). Hahodim speaker impedance on the current fasting person (useful), write in the air resonance frequency Fs (this is the frequency at which the voltmeter maximal :), the voltmeter Uo at minimum frequency (well, for example 10 Hz) and Um at the resonance frequency Fs.

2. Hahodim frequencies F1 and F2, in which the curve V (F) intersects the level of V = SQRT (Vo * Vm).

3. Hahodim Qts = SQRT (F1 * F2) * SQRT (Uo / Um) / (F2-F1) is the total quality factor of the dynamics, we can say, the most important value.

4. To find Vas need to take a small indoor Boxes volume Vc, with a hole a little smaller than the diameter of the diffuser. Tightly to lean to the speaker hole and repeat the measurements. From these measurements, you will need a resonant frequency dynamics in the housing Fc.Hahodim Vas = Vc * ((Fc / Fs) ^ 2-1).

This procedure is written in the audio shop • 4 for 99 year. I had checked it out .. There are others, when measured mechanical properties of the head, weight, flexibility, etc.

[Q] I now have options speaker, what to do?

[A] Each speaker in the design sharpen a certain kind of acoustic design. To find out under what is, look at the quality factor.

Qts> 1,2 it heads for the open boxes, optimally 2.4

Qts <0.8-1.0 - head for closed boxes, optimally 0.7

Qts <0.6 - for bass reflex, optimum - 0.39

Qts <0.4 - for horns

Wise to sort head is not on good quality and value for Fs / Qts. Cite from memory, the reluctance of the formula to calculate.

Fs / Qts> 30 (?) Screen and open housing

Fs / Qts> 50 closed body

Fs / Qts> 85 Tubes

Fs / Qts> 105 Bandpassy (bandpass resonators)

Elasticity, meatiness, dryness and other similar characteristics of the sound emitted by Bass speakers, are largely determined by the transient response of the system formed by the speaker, woofer design and the environment. To this system was not to release the impulse response, its quality factor should be less than 0.7 for systems with one side of the radiation dynamics (closed and phase inverter) and 1.93 for two-way systems (design type screen and open box)

[Q] Where to read about the open design?

[A] Open boxes and screens is the simplest type of decoration. Pros: ease of calculation, no increase in the resonant frequency (the size of the screen depends only view of the frequency response), almost constant quality factor. Disadvantages: large size of the front panel. Sufficiently competent and simple calculations of this type of design can be found in VK Joffe M.V.Lizunkov. Household speakers, M., Radio and Telecom.1984. And in the old Radio certainly have primitive amateur calculations.

[Q] How to calculate the closed box?

[A] Making "closed box" is of two types, infinite baffle and suspension compression. Getting into a particular category depends on the ratio of suspension dynamics and flexibilities in the air box, denoted alpha (by the way, you can try on the first and second count and change by filling).For an infinite screen ratio is less than 3 flexibilities for suspension compression more than 3-4. Can be considered as a first approximation that the heads with high Q sharpened by an infinite baffle, with less-under suspension compression. Taken to advance the speaker enclosure is closed infinite baffle has a larger volume than the compression box. (Generally speaking, when there is a speaker, the optimal body under it is clearly a certain amount. Errors encountered when measuring the parameters and calculations, can be slightly corrected by filling).Speakers for closed shells have powerful magnets and soft suspensions unlike heads for the open boxes. The formula for the resonant frequency of the dynamics in the design of volume V Fc = Fs * SQRT (1 + Vas / V), and an approximate formula relating the resonant frequency and quality of the head in the body (the subscript "c") and open space (subscript "s") Fc / Qtc = Fs / Qts

In other words, it is possible to implement the required quality factor only way speaker system, namely the choice of the volume of a closed box. What is the quality factor to choose? People who have not heard the sound of natural musical instruments, usually choose speakers with Q bolee1 0. In columns with a quality factor (= 1.0) the smallest uneven frequency response in the lower frequencies (and what does that sound?) Achieved at the cost of a small release on the transient response. Maximally smooth frequency response is obtained when Q = 0.7, and fully aperiodicity impulse response with Q = 0.5. Homogrammy for calculations can be taken in the above book.

[Q] Articles about speakers often words like "approximation of Chebyshev, Butterworth," etc. How does this relate to the speakers?

[A] The speaker system is a high-pass filter. The filter can be described by the transfer function. Transfer characteristic is always possible to fit a known function. In the theory of filters use several types of power functions, named for mathematicians first licked a particular function.Function determined by the order (maximum exponent, ie H (s) = a * S ^ 2 / (b2 * S ^ 2 + b1 * S + b0) has the second order) and the set of coefficients a and b (from these coefficients You can then move on to the values ​​of the real elements of the electric filter, or electro-mechanical parameters.) Next, when it will go on the approximation of the transfer characteristic polynomial Butterworth or Chebyshev or something else, it should be understood so that the combination of the properties and dynamics of the body (or containers and inductance in an electric filter) turned so that most accurately the frequency and phase characteristics can be adjusted to a particular polynomial. Most smooth frequency response is obtained if it can be approximated by a polynomial Butterworth. Chebyshev approximation is characterized by the wave-frequency response and a large stretch of the working area (according to GOST to -14 dB) in the region of lower frequencies.

[Q] What kind of approximation to select the phase inverter?

[A] So before the construction of a simple bass reflex need to know the volume of the box and reflex tuning frequency (pipes, holes, passive radiator). If as a criterion to select the most smooth response (and this is not the only possible criterion), we get the following label A) Qts <0,3-most smooth curve will kvazitretego order B) Qts = 0,4 - better described battervortovskimi curves in) Qts > 0.5 - will allow the waves on the AFC, Chebyshev. In case A) bass reflex tuned to 40-80% higher than the resonance frequency in case b), the frequency of resonance, in case B) below the resonance frequency. Also in these cases will be a variable volume enclosure .. In order to find the exact frequency tuning, we must take the original formula, rather cumbersome to bring them here. Therefore, I refer interested in AudioMagazin 1999, then there is an educational program can be sorted out, or book Aldoshina. And even in the article Ephrussi Radio for '69 amiss.

Conclusion

If after reading all this, you still have the desire to rivet something yourself, you can take online nifty program type WinspeakerZ and calculate it all myself, remembering that of G.. candy not do. Not to be carried away by a decrease of the cutoff frequency, in any case, do not try to compensate for the roll off the amplifier. AFC can be leveled and a little bit, but the sound is enriched harmonics and subharmonics weight.On the contrary, the best results, in terms of pleasantness to the ear can be achieved forcibly ruining inlet UM very lowest frequencies, iefrequencies below the cutoff frequency HCH column. Another remark concerning the phase inverter configuration error in the resonance frequency of the phase inverter 20% leads to a surge or decline in response at 3 dB.

Oh, I almost forgot to say about subwoofers that actually strip resonators. Q-factor of the speakers for them should be even lower. The simplest bandpass too incalculable, but this ends my courtesy.

Original article sourse cxem.net

UM protection unit and acoustics overcurrent

It is based in protection circuit Audio Analogue Aida - from the site of its designer Federico Paoletti . I developed it a little bit and used in his new mobile amplifier - also borrowing from Paoletti. The scheme is applicable to any PA whose output - compound emitter follower (2 stages or more, or a Darlington Naturally - silicon, or a cascade of CMOS).

In the original scheme in the traditional circuit protection (voltage drop across the emitter resistor opens key bypass transition BE composite output transistor) added two optocoupler (circuit shunt base for the upper and lower arm). Current drawn from the shunt base flows through the LED of optocoupler and opens galvanically isolated key. Fine, but the same node can not just arbitrarily turn off power, but doing it on the pitch outside. Need another pair of optocouplers, shunt BE transitions output transistors:

Threshold set divider R1-R2 based on the current limit for each transistor and the emitter resistance in the circuit output. The total resistance R1 + R2 must be in the range 10 .. 100 ohms. Thanks circuit R3-C1-R4-D1, R8-C2-R9-D2 (LPF) threshold DC is much higher than the AF.Furthermore, the threshold decreases with increasing temperature T1, T2.

The first and fourth (vertical) optocouplers - security sensors (closed = alarm), second and third - the keys controlled by an external signal (sink current = off UM). In the chain of forced shutdown necessarily provide current-limiting resistor. Resistors R9-10 - I put instead of jumpers on the board, whether they are as such - probably not.

Despite the additional voltage drop across the LED, the scheme is guaranteed off the PA with a repeater on single and dual Darlington (0.33 ohms under the emitter). The main thing that current drawn T1, T2 in the "triangle" - the voltage amplifier - was sufficient to guarantee the inclusion of optocouplers (not less than 1 mA for TLP521). Optocouplers - any except Darlington (well, they go to hell, and do not need much gain here). Requires current transfer ratio is determined by currents and levels of automatic protection, as well as current shunt which will select from the "triangle". T1, T2 - any thin with low saturation voltage.

Incidentally, memorized by heart half volt LED on - not quite right. The LED TLP521 in this scheme falls at room temperature not more than 0.9V.

When designing the board first, "the mind" is placed own mind and protection circuit - second. In this "ground" defense to hold separate and connect with other "lands" at a common point "star." If a car amplifier analog ground unleashed current board of land and automation unit usually sits on the board, the circuit R4D1 R9D2 connect with analog power and ground otpronov - with on-board.

Original article sourse cxem.net

Protection device speakers

In life, frequent situations where, for whatever reason speakers connected to an audio amplifier, the power of which exceeds the maximum allowed for a system that, on the one hand, often produce the best sound quality, increase the dynamic range, with another - increases the risk of damage due to overload dynamic heads. This is especially true when using the speaker on school, student, youth parties, where the acoustics are often connected to the first that fell known good amplifier that is "powerful." To prevent damage to the speakers when applying for her power, exceeding the nominal, it is necessary to equip the unit overload protection, built-in speakers and requires no additional power supply. Schematic diagram of such a device designed to protect the AC power 10 ... 35 W is shown in below

Protection device speakers circuits

Also in case of overload tripping SS, this device also protects it from damage by the dynamic head in the event of failure of the transistor amplifier and its output appears on the DC voltage. The device is connected to the output of the power amplifier audio frequency. The AC voltage is rectified by a bridge diode VD1. Resistor R1 eliminates the influence of a job amplifier. The rectified voltage is smoothed oxide capacitors NW, C2. While the output power of the amplifier does not exceed the maximum allowable for the AU, the voltage at the capacitor C2 is small, the zener diode VD3 closed, hence also closed and SCR VS1. In the micro-current SCRs of this type are controllable, ie, they can close the control voltage. Since VS1 is closed and will be closed transistor VT2. K1 relay contacts are closed, dynamic head at AU will do 100% of capacity. As soon as the output power of the amplifier exceeds permissible for AC voltage on C2 increases so that opens zener VD1, open SCR VS1 and the transistor VT2, K1 relay contacts open, the power supplied to the speakers will be limited by resistors R11-R13. These load resistors are a power amplifier, which improves stability of the amplifier in case of disconnection of speaker system, moreover, these resistors reduces arcing between the relay contacts when closing and opening. When protection against overload LED lights HL1. Transistor VT1, emitter junction which operates as a diode with a micropower voltage stabilization 7 ... 12 V protects the FET from the breakdown of a gate insulator. Once the voltage at the amplifier output is reduced, zener VD3 closes closed VS1, VT2, relay K1 is closed, on the AU will come back full power. Resistor R8 introduces small hysteresis to prevent cyclic circuit-opening relay contacts at a constant power output, slightly higher than the threshold. R9 resistor reduces the current through the relay coil by opening its contacts, capacitor C6 accumulates enough energy required for reliable operation of the relay.

When placing the speaker structure within the housing structure elements operate in a fairly strong vibrations in a wide range of sound frequencies produced by the dynamic head, moreover, in some cases, should also be considered an alternating magnetic field from the dynamic head. PCB should be located at a maximum distance from the open magnetic systems dynamic heads.

The device used fixed resistors MLT, Cl-4, C2-23 or imported analogues. Trimmer R3 is desirable to use a sealed enclosure, for example, SP4-1, GPA-16c, SP5-16A, SDR-19a-3 SP4. After setting up the rotation axis of the resistor must be assigned a drop of paint. Capacitor C1 terephthalate film ethyl K73-17, K73-9 or similar. C4 - ceramic K10-17, CM-5, oxide capacitors - K50-35 or imported analogues. NW capacitor can be formed from two 470 uF (provided on the circuit board). If necessary, the capacitor C6 also be used for the operating voltage of 100 V. In the case when the device is applied with amplifiers having a supply voltage output stages more than ± 50 V electrolytic capacitors need to be at the voltage of 160 V, the power and the resistance of resistors Rl, R2 , R9 also need to increase. Capacitors NW, C6 set parallel to the PCB, and further secured with wire clamps on it. Diode bridge can be replaced by a similar low-power, for example, DB103-DB107, RB153-RB157 or make up of four rectifier diodes with a working voltage of at least 100 V. Instead KD243A can install any of a series of KD243, KD247, KD208, KD105, 1N4002-1N4007. 1N4738A Zener diode can be replaced by KS175A, KS175ZH, KS126K LED - any other. Instead trinistor KU112A can apply CG 112 AM in the TO-92. N-channel field effect transistor in this embodiment IRF9540 can operate without the heat sink. Its maximum drain-source voltage of 100 V, the domestic counterpart - KP785A. Instead, the transistor can be used IRF9634, KP796A having UCH MAX> 250 V. Instead KT315A can apply any of the series KT312, KT315, SS9014. Relay K1 - REC-29, passport DUSCH4.501.56.Resistance of the coil of the relay about 950 ohm stable switching contacts occurs at a voltage of 15 V, the minimum voltage retention - 7 V. This type of relay modules used in the control of domestic TV USTST. For replacements, consider the fact that the contacts of the relay must commute significant current.

PCB protection device speakers 

The apparatus may be mounted on a printed circuit board size 140x50 mm, wherein all the elements are installed than the LED. On Figure 2shows the circuit board from the conductors. 

From the installation fee is desirable to cover three or four thin layers of epoxy glue. Each subsequent layer is applied after setting the previous one. Fee is attached to the body with five screws inside AU MOH or screws. If possible it is desirable to close deaf thick-walled (> 0.5 mm) casing, which also reduce the probability of failure of the device due to vibrations in the powerful speakers, as well as reduce the likelihood of contact bounce relay. 

Manufactured author two instances these devices are used in conjunction with speakers 15AS-220, which uses dynamic head 25GDN-3-4.These systems start to wheeze and rattle when the input power more than 40 watts. Protection threshold set to 25 watts. These speakers are powered by an amplifier "Orbit UM-002 stereo", 

which is able to develop power above 50 watts at 4 ohms. Other two copies installed in homemade sealed AC collected on broadband heads 10GDSH-1 powered by an amplifier "Corvette 50U-068 C". On threshold of protection is also installed at the rate of 25 watts of amplifier at 4 ohms. If you are working with powerful speakers (> 35 ... 5O W) and a powerful amplifier SCR will close at too low power for this case, the resistance of the resistors R4 and R7 can be doubled. 

This device can be modified by setting instead of fixed resistor R2 thermistor NTC resistance of 3.3 ... 4.7 ohms at 25 ° C, which, through a pad of heat conductive rubber should be rigidly secured to the magnetic system, a powerful low frequency driver. In this case, strong heating of the magnetic system will include device protection with less output power amplifier.

Original article sourse cxem.net

Calculation subwoofer using WinISD

In this article I want to talk about and show how you can calculate the subwoofer and what you should pay attention when designing in the following programs: WinISD 0.44, WinISD 0.50a7. Detailed description of the program WinISD .

Payment will be made ​​for a box of ten-inch speaker Audiobahn 1051T. Let's start! Run the program WinISD 0.50a7

1. Create a new project (New Project). 

2. By pressing this button, select the speaker of the database program. 

3. View the T / S parameters.

4. T / S parameters. Click on (Next)

5. Selecting the number of speakers. 

6. Type of installation.

Normal - all the speakers are on the same panel.

Isobaric speakers are face to face.

Click on (Next)

7. Efficiency speaker. Shows what type of housing is more suitable. 

8. Selecting the type of box.

Sealed box - the name speaks for itself

Vented - box equipped with a pipe (Bass reflex).

Band pass 4th order - the speaker is located between the two chambers, one of which has a phase inverter.

Band pass 6th order - is between the two cameras equipped with both phase inverter.

Passive radiator - one closed box speaker and passive radiator (speaker without magnet)

Choosing which type suits us and click on (Next)

Next, the program offers a way to design the frequency response in different ways. I do not focus on this point and click Next. 

If you select Passive Radiator enter the program will offer the following T / S parameters of the passive radiator:

Vas - is excited indoor air volume speaker.

Fs - resonant frequency.

Xmax - the maximum stroke of the diffuser.

QMS - Mechanical Q.

SD - diffuser area.

Next we consider the example program Band pass fourth order.

Tab Driver.

9-10. Again, you can specify the number and type of installation speakers. 

11. Additional features. 

Tab Box.

12-13. Camera box 

14. Volume of the chamber. 

15. The frequency of the camera settings. 

Tab Vents (Phase inverter (s))

16. Number of bass reflex (s) 

17. Fazoinvertor diameter (s) 

18. Length bass reflex (s) 

19. Type of round or rectangular. You can change the nav on a circle. 

20. View fazoinvertora.

Turn to the main calculation box:

21. Click on the box shown schematically on the right mouse button while holding move the cursor along the axis (X) in-law to change the volume on the horizontal axis (Y) vertically to change the frequency. Similarly, the left mouse button to change the parameters of the lower chamber. The top of the curve should be above the red line between 35Hz and 120Hz if this subwoofer as widely as possible and smoother.

Transfer function magnitude. Amplitude frequency characteristic 

Like this, but the lower limit of 40 Hz and the upper 113Gts is also suitable. 

Where I marked with red dotted lines in practice there will be cut frequency crossover.

Select dates: Maximum Power. 

Maximum Power 

In this graph, the program shows the maximum power versus frequency. It can be seen that there is recession recession peak power 60 watts 39 hertz in practice cone speaker lacks stroke (Xmax) and an unpleasant sound - distortion. On the finished product it must also take into account and to limit the power

Select dates Maximum SPL 

Maximum SPL. This chart shows the maximum sound pressure 

Also seen a decline. For the same reason. Last two graphs from another speaker, I showed them to have clarity. 

Here are graphs for our guinea. First a little far-fetched at a frequency of 0 Hz to 25 Hz and all the speakers there is a recession.

Now we must determine the size of the box will be installed speaker. 

To do this, run the program WinISD 0.44 push a new project.

We need to introduce our dynamic parameters in this program because at its base it is not for this press «New» 

We proceed to WinISD 0.50a7

22. By clicking this button you can see the T / S parameters that need to be put in WinISD 0.44.

Introduce the parameters and click OK to close the window so as not to interfere. 

Create a new project.

23. Reposition the tick to select a speaker. 

Press on, and do just as well as in WinISD 0.50a7

Transferring the parameters of the box in WinISD 0.50a7 WinISD 0.44. 

24. Push to start to count the size of the box. 

25. Press and the program provides the optimal dimensions in her opinion. 

In disposal we have 10-inch speaker complete with its outer diameter of 300 mm to fit it into the box dimensions W and D Undue be less 300mm 

26. Width 300mm inscribe equals 0,300 METERS 

30. You can change the unit of measure by simply clicking on the dimension in this case the letter «m» 

28. Length of 0,300 meters is entered 

27. Push the «H» program shows height. 

31. Pay attention to the L1 and L2 is the height of the cameras should look to tie the speaker depth does not exceed the value of L2. 

But we must take into account the thickness of the material he is still in the lap of nutria has a shelf where the speaker stands and also take into account the thickness of the speaker himself, he, too, takes a beat him if I already priced big box in there to stand spacers they should also be taken into account. 7 parts obtained to calculate the correct items is necessary to consider that some of them will be unnecessarily whipped program shows the inner diameters. Letter «P» I'll puncture the material thickness which must be added to the other values. 

1) D x W 

2) D x W 

3) D x W 

4) H + (P * 3) x D 

5) H + (P * 3) x D 

6) H + (P * 3) x W + (P * 2) 

7) H + (P * 3) x W + (P * 2) 

Gets the size of the items if the material thickness of 20mm: 

1) 300x300 

2) 300x300 

3) 300x300 

4) 420h300 

5) 420h300 

6) 420h 340 

7) 420h 340

Now we can proceed to the calculation of the phase inverter.

32. Type fazoinvertora we use a rectangular 

33. Length. When the end of the phase inverter is shifted to the wall box 

it virtually lengthened, and in fact it turns out that he is not listening on that frequency and greater long WinISD 0,44 ignores this virtual extension can be calculated by the formula itself but it's easier to look in the program WinISD 0.55a7 

I repeat: it is really only when the end of the phase inverter is shifted to the wall box and when he speaks it is not valid. So the program shows WinISD 0,44 28,86 cm and WinISD 0,55 25,64 a7 sm.F phase inverter will be installed in the item number 4 420h300 subtract 20 from 420 is the height fazoinvertora get exactly 400 square fazoinvertor unnecessarily adds another item 8) 300h255

Here are the final dimensions of parts and their number. 

1) 300x300 

2) 300x300 

3) 300x300 

4) 400x300 

5) 420h300 

6) 420h340 

7) 420h340 

8) 300h255

34. Air resistance. Air resistance in a vented enclosure to do as little as possible by increasing the opening area of ​​the phase inverter.

Separation filter crossover for car subwoofer

The figure shows a circuit diagram of car crossover (cr

ossover) for the subwoofer. The input stage of the transistor Q1 is a differential summing amplifier, and the switch S1 is used to switch polarity. Switched-capacitor filter with a slope of 24 dB per octave (chip IC1) is the basis of continuously tunable filter. Potentiometer R13 controls the filter cutoff frequency on the chip IC1, adjusting its clock speed. Because the switched-capacitor filters, by definition, work with discrete signals at the input of IC1 should be restrictive filter (antialiasing). Such a low pass filter of the second order constructed by transistors Q2 and Q3 and associated elements. The output signal of IC1 via pin 5 served on a subsonic filter with the possibility of lifting the lowest frequencies. When switch S2 is closed, then on the rise of the frequency characteristic occurs. Additional filtering is provided by infrasound capacitors C1 and C2 directly to the input of the crossover. The resistor R18 and the capacitor C 10 is assembled so-called remodeling filter, eliminating the remnants of the quantization noise. The power supply circuit, gathered on the integral regulator 78L08 (chip IC2), and provides the main supply voltage of 8.6 V, and the bias voltage of 4.8 V. The diode D1 protects the circuit from negative voltage spikes and incorrect wiring. Diode D2 displaces the output reference voltage stabilizer 78L08 0.6 V for receiving an output voltage of 8.6 V, and not B. 8

Original article source cxem.net

Circuit diagram capacitor charge control

The scheme is designed to protect against inrush current when the battery uncharged capacitor on-board network. Who has not tried to include uncharged faradnik network without limiting resistor - better not ... At a minimum, get burnt contacts.

When you turn the discharged capacity in network capacity C1 is discharged, T1 (n-MOSFET switch with low channel resistance) is closed.Capacitance C2 (the same faradnik) is charged through a low-resistance R5. T2 opens almost instantly, the shunt to ground C1 and T1 gate.When the potential negative terminal C2 falls below 1V (charge to Uakb - 1B), T2 closes smoothly C1 is charged to about 9/10 Uakb opening T1. The time constant R2C1 is large enough so that the current surge T1 (pre-charge C2 +1 V to Uakb) does not exceed the rating for T1.

In the future, the negative terminal of C2 constantly shorted to ground through T1, regardless of the direction CURRENT T1 (both literally - from drain to source, and in the opposite direction). Nothing wrong with "rollover" OPEN TIR transistor not. When choosing a good enough conductive transistor entire reverse current flow through the channel, and a built-wheeling diode will not open because the voltage drop across the channel at times less than required for the opening of 0.5-0.8 V. By the way, there is a whole class of TIR devices (eg FETKY ), designed specifically to work in the opposite direction (synchronous rectifiers), they have built a diode is shunted by an additional force Schottky diode.

Calculation: for transistor IRF1010 (Rds = 0.012 ohms) voltage drop of 0.5 ohms will only be achieved with the current channel 40A (P = 20W).For four of these transistors in parallel and the same discharge current of 40A - on each transistor will dissipate 0,012 * (40/4) ^ 2 = 1.2 W, ieradiators they are not required (the more that will dissipate 1.2W only when differential current consumption but not consistently).

Dense installation (you have plenty of space for extra radiator?) - Advisable parallels small (body TO251, DIP4) transistors, generally do not provide radiators, based on the ratio of current (power) consumption of the amplifier - Rds - limit power dissipation. Since Pds max is typically 1W (800 mW for DIP4), the number of n transistors (c Rds each) for the amplifier with an output power Pout must be at least n> 1/6 * Pout * sqrt (Rds) at 12V supply (dimension in the formula I omitted). In fact, given the short duration current pulses, n can be easily reduced by half compared with a given formula.

Resistor R5 is selected from the charge compromise heat output and charging time. When these 22 ohms - charge time of about 1 minute at power dissipation 7 watts. R5 can instead include 12V bulb, say, indicator. Resistors R1, R3 - reinsurance (discharged capacity when disconnected from the network).

Connect to indicate activation of additional inverter (reducing R2). Attention! The scheme is efficient at using npn transistors T2, T3 with h21e> 200 (KT3102). Depending on the brightness of the LED, R1, select the range of 200 ohms - 1k.

But the view of the circuit in which the key shutter control signal REMOTE (And transistor). The non-connected or off REMOTE key transistor guaranteed closed. D3-D4 LEDs indicate charging C1, D5-D6 - the open state of the key.

Accurate indication of the threshold voltage is provided easiest IP TL431 (KR142EN19) in a typical mode voltage comparator (with the corresponding subgroup in the input circuit and current-limiting circuit cathode R).

Loss schemes largely depend on the installation. Ensure that the minimum resistance (and corresponding current thickness of the wires) in the power circuit (terminal + / C2 / T1 /-terminal). In amateur practice, I think, make outgoing terminals impractical - it is better to unsolder the short wires AWG8, which binds to the terminal block diagram of the amplifier.

Original article source cxem.net