Showing posts with label for. Show all posts
Showing posts with label for. Show all posts
Wednesday, November 12, 2014
indicator alarm for Water level circuit with explanation
This electronic circuit is a simple water level indicator alarm that is based on few transistors . The circuit is very simple and it has a very low current consumption , so you can use a 9 volts battery to powering this water level indicator alarm . This water level indicator alarm electronic circuit can be used even for rain alarm or short circuit alarm , a resistance with a value from 0 to about 1 M ohm will trigger it . The Q1 transistor acts as a switch which applies current to the unijunction relaxation oscillator Q2 . The signal frequency of the alarm circuit is give by the values and ratios of the C1 / R2 .
If you don’t have the transistors marked on the schematic diagram you can replace them almost with any similar types . As you can see in the schematic diagram , between probes is mounted a switch ( you can use a push-button) for testing the circuit , but it can be removed .
The speaker used in this project must have a impedance between 15 and 90 ohms .
Monday, November 3, 2014
Automatic cooler fan for amplifiers
The schematic of an automatic cooler fan for audio amplifiers is given here. The circuit automatically switch ON the cooler fan whenever the temperature of the heat sink exceeds a preset level. This circuit will save a lot of energy because the cooler fan will be OFF when the amplifier is running on low volume. At low volume less heat will be dissipated and it will not trigger the cooler fan ON.The temperature is sensed using an NTC (negative temperature coefficient) thermistor R2. Junction of thermistor r2 and resistor R1 is connected to the inverting input (pin3) of IC1 which is wired as a comparator. The non-inverting input (pin2) is given with a reference voltage using the preset R3. As temperature increases the resistance of NTC thermistor will drop and so do the voltage across it. When the voltage at the inverting input becomes less than that of the reference voltage (set for a particular threshold temperature) the output of the comparator goes high and switches the transistor Q1 ON. This will activate the relay and the cooler fan will be switched ON. When the temperature decreases the reverse happens. LED D2 will glow when the fan is ON. Diode D1 is a freewheeling diode.
Notes.
The circuit can be assembled on a Vero board.
Use 12V DC for powering the circuit.
The circuit can be calibrated by adjusting the preset R3.
K1 can be a 12V, 200 ohm, SPST relay.
LM311 must be mounted on a holder.
Sunday, October 26, 2014
Playback Amplifier For Cassette Deck
For some time now, there have been a number of tape cassette decks available at low prices from mail order businesses and electronics retailers. Such decks do not contain any electronics, of course. It is not easy to build a recording amplifier and the fairly complex magnetic biasing circuits, but a playback amplifier is not too difficult as the present one shows. The stereo circuits in the diagram, in conjunction with a suitable deck, form a good-quality cassette player. The distortion and frequency range (up to 23 kHz) are up to good standards. Moreover, the circuit can be built on a small board for incorporation with the deck in a suitable enclosure. Both terminals of coupling capacitor C1 are at ground potential when the amplifier is switched on.
Circuit diagram:
Because of the symmetrical ±12 V supply lines, the capacitor will not be charged. If a single supply is used, the initial surge when the capacitor is being charged causes a loud click in the loudspeaker and, worse, magnetizes the tape. The playback head provides an audio signal at a level of 200–500 mV. The two amplifiers raise this to line level, not linearly, but in accordance with the RIAA equalization characteristic for tape recorders. Broadly speaking, this characteristic divides the frequency range into three bands:
Circuit diagram:
Cassette Deck Playback Amplifier Circuit Diagram
Because of the symmetrical ±12 V supply lines, the capacitor will not be charged. If a single supply is used, the initial surge when the capacitor is being charged causes a loud click in the loudspeaker and, worse, magnetizes the tape. The playback head provides an audio signal at a level of 200–500 mV. The two amplifiers raise this to line level, not linearly, but in accordance with the RIAA equalization characteristic for tape recorders. Broadly speaking, this characteristic divides the frequency range into three bands:
- Up to 50 Hz, corresponding to a time constant of 3.18 ms, the signal is highly and linearly amplified.
- Between 50 Hz and 1.326 kHz, corresponding to a time constant of 120 µs, for normal tape, or 2.274 kHz, corresponding to a time constant of 70 µs, for chromium dioxide tape, the signal is amplified at a steadily decreasing rate.
- Above 1.326 kHz or 2.274 kHz, as the case may be, the signal is slightly and linearly amplified. This characteristic is determined entirely by A1 (A1’). To make the amplifier suitable for use with chromium dioxide tape, add a double-pole switch (for stereo) to connect a 2.2 kΩ resistor in parallel with R3 (R3’). The output of A1 (A1’) is applied to a passive high-pass rumble filter, C3-R5 (C3’-R5’) with a very low cut-off frequency of 7 Hz. The components of this filter have exactly the same value as the input filter, C1-R1 (C1’-R1’). The second stage, A2 (A2’) amplifies the signal ´100, that is, to line level (1V r.m.s.).
Saturday, October 25, 2014
Compressor For Electret Microphone Diagram Circuit
The ‘FM Remote Control Receiver’ (available on this website in Infra-red circuits section) has a connector where an analogue output is made available. To make a simple intercom or P.A. system the associated transmitter needs a microphone pre-amplifier that outputs a signal at the correct level. And that is exactly the function of this circuit. Actually, this design is adapted from a circuit published last year (‘AM Modulator for Intercom’). A few things have been changed so that it can work with the 5 V supply from the transmitter module. The OTA (IC1) used here is the single version (CA3080), which has slightly different characteristics from the dual CA3280.
The quad opamp is the same rail-to-rail TS924IN, made by ST. The turnover frequency of the filter (3rd order 1 dB Chebyshev) has been increased slightly to improve the intelligibility of speech and is now about 5.5 kHz. The filter now amplifies the signal by a factor of 10. In practice it is possible that due to various tolerances and the fact that the opamp is not perfect, the filter characteristic shows some deviation from that required. In our prototype it was necessary to change R15 into 2k7 to straighten the response curve. The DC current variation at the output of the OTA and the resulting offset variation at the output of current/voltage converter IC2d is such that the gain of IC2d has to be substantially smaller than in the ‘old’ design.
Otherwise the output could easily rise to the supply voltage at low signal levels. The value of R6 has therefore been made smaller by a factor of 10. This has reduced the gain of the circuit by 20 dB, which is compensated for in the filter. The amplitude of the signal from IC2d is fed back as a control current to the OTA by peak rectifier D1/C3 and inverting amplifier IC2b. R7 limits the loading on IC2d. P1 can be used to adjust the amplifier between a fixed gain and maximum compression. Figure A shows clearly what effect the circuit has. 0 dBr corresponds to 100 mV. The maximum gain, with P1 set to maximum compression, is about 48 dB (250 Ω) for small signals.
The minimum gain is about 20 dB (10 Ω). The OTA is then slightly overdriven and the distortion becomes several percent! With a fixed gain selected (P1 shorted) the gain is about 42 dB (125 ×). The middle curve was measured with P1 in its central position. The curve drawn for a fixed gain (the straight line) doesn’t finish at the edge of the graph because the end of the line corresponds to the maximum possible output level, which is 25 dBr (≈1.76 V or 5 / 2√2). Figure B shows the frequency response. The low turnover frequency is mainly determined by C8 (and to a lesser extent by C1) and is about 120 Hz.
The current consumption is about 7 mA When the circuit is battery powered we recommend the use of three AA cells, because the circuit still works perfectly at 4.5 V. If you want to use a higher supply voltage (maximum 12 V for the de TS924IN and 30 V for the CA3080, but you should also think of the voltage across the electret microphone!) you have to keep in mind that the maximum current through R9 (which is IABC) is only 2 mA. When we consider a maximum chosen current of 1 mA and the maximum output voltage of IC2b (half the supply voltage, which is 2.5 V), then the value of R9 should be (2.5 – 0.7) V / 1 mA = 1.8 kΩ. The value of 0.7 V corresponds to the potential between pin 5 and earth.
For a larger safety margin R9 is calculated with the full supply voltage and a current of 2 mA: (5 – 0.7) V / 2 mA = 2k2 (rounded upwards). Of course the regulation will then be different (a little less gain). This circuit and the transmitter module can therefore be fed from the same 5 V supply. Because the transmitter requires a DC offset at its input, a resistor is connected to +5 V via a jumper, which biases the output to half the supply voltage. With the jumper open R17 functions as a load resistor when the output is not connected, because C9 still has to charge up even without a load. If you’re designing a PCB for this compressor then it makes sense to include the transmitter module as well. The current consumption then increases by about 10 mA.
Compressor for Electret Microphone
The quad opamp is the same rail-to-rail TS924IN, made by ST. The turnover frequency of the filter (3rd order 1 dB Chebyshev) has been increased slightly to improve the intelligibility of speech and is now about 5.5 kHz. The filter now amplifies the signal by a factor of 10. In practice it is possible that due to various tolerances and the fact that the opamp is not perfect, the filter characteristic shows some deviation from that required. In our prototype it was necessary to change R15 into 2k7 to straighten the response curve. The DC current variation at the output of the OTA and the resulting offset variation at the output of current/voltage converter IC2d is such that the gain of IC2d has to be substantially smaller than in the ‘old’ design.
Otherwise the output could easily rise to the supply voltage at low signal levels. The value of R6 has therefore been made smaller by a factor of 10. This has reduced the gain of the circuit by 20 dB, which is compensated for in the filter. The amplitude of the signal from IC2d is fed back as a control current to the OTA by peak rectifier D1/C3 and inverting amplifier IC2b. R7 limits the loading on IC2d. P1 can be used to adjust the amplifier between a fixed gain and maximum compression. Figure A shows clearly what effect the circuit has. 0 dBr corresponds to 100 mV. The maximum gain, with P1 set to maximum compression, is about 48 dB (250 Ω) for small signals.
The minimum gain is about 20 dB (10 Ω). The OTA is then slightly overdriven and the distortion becomes several percent! With a fixed gain selected (P1 shorted) the gain is about 42 dB (125 ×). The middle curve was measured with P1 in its central position. The curve drawn for a fixed gain (the straight line) doesn’t finish at the edge of the graph because the end of the line corresponds to the maximum possible output level, which is 25 dBr (≈1.76 V or 5 / 2√2). Figure B shows the frequency response. The low turnover frequency is mainly determined by C8 (and to a lesser extent by C1) and is about 120 Hz.The current consumption is about 7 mA When the circuit is battery powered we recommend the use of three AA cells, because the circuit still works perfectly at 4.5 V. If you want to use a higher supply voltage (maximum 12 V for the de TS924IN and 30 V for the CA3080, but you should also think of the voltage across the electret microphone!) you have to keep in mind that the maximum current through R9 (which is IABC) is only 2 mA. When we consider a maximum chosen current of 1 mA and the maximum output voltage of IC2b (half the supply voltage, which is 2.5 V), then the value of R9 should be (2.5 – 0.7) V / 1 mA = 1.8 kΩ. The value of 0.7 V corresponds to the potential between pin 5 and earth.
For a larger safety margin R9 is calculated with the full supply voltage and a current of 2 mA: (5 – 0.7) V / 2 mA = 2k2 (rounded upwards). Of course the regulation will then be different (a little less gain). This circuit and the transmitter module can therefore be fed from the same 5 V supply. Because the transmitter requires a DC offset at its input, a resistor is connected to +5 V via a jumper, which biases the output to half the supply voltage. With the jumper open R17 functions as a load resistor when the output is not connected, because C9 still has to charge up even without a load. If you’re designing a PCB for this compressor then it makes sense to include the transmitter module as well. The current consumption then increases by about 10 mA.Author: T. Giesberts - Copyright: Elektor Electronics
Friday, October 17, 2014
Electrical protective circuit for Bench
The bench or table is the kingdom of a technician, hobbyist or electronics student. A Work benches must have at least an antistatic rubber surface, a good grounding system and a power strip with fuse protection. In case of sensitive equipment, the ideal is to work with a personal grounding straps, and even a little extra protection as an antistatic mat and grounded on the workbench surfaces, this protection prevents damage by static discharge.
![Electrical]()
Operation of electrical protection Bench
We can increment a counter with two simple circuits that will display its operation and how to build. One is the isolation transformer, which serves mainly to avoid electric shocks during construction or repair of circuits that are energized, such as switching power supplies, etc.. The other protection circuit bench is the lamp in series, a tool able to avoid further damage to electronic equipment. With just a light bulb in series with the AC mains and the circuit to be tested or repaired can avoid further damage in case of short circuit.
Isolation transformer easy and cheap
What is an isolation transformer
Isolation transformer as the name implies, isolates the mains of an appliance or power network, it depends on your usage. Various devices and old appliances, or even modern does not have transformer, they use a direct source, where coach or even curious how we run the risk of a shock, which in some cases can be fatal.
![Isolation]()
In Figure 2 we see a typical circuit power strip with an isolation transformer, the transformer primary is connected to AC mains that has a "live" phase and another phase neutral or earth (were not talking about the central ground pin ). This means that the mains 110 Volts AC (127 Volts) has a phase that is in the neutral or ground potential. The fatal crash occurs precisely for the reason that when you play barefoot or grounded the living phase of the network.
![Isolation]()
Already with the transformer T1 in its secondary, none of the terminals is grounded, if you accidentally touch one or other of the two wires of the secondary you will not receive shock. But if you touch both simultaneously you will receive a shock which can be fatal, but it is just touching the two at once.
Making our own isolation transformer
In Figure 1 we have a low cost circuit, this circuit uses two transformers, T1 and T2 are two common transformers, need not be equal, but must have the same tensions, the primary with the desired voltage, 110 volts, or both and the secondary 12 volt type 12v-0v-12v. The connection is simple, the secondary of T1 is connected to the secondary of T2. The chain should be at least 5 amps for a good performance.
The isolation transformer also keeps us away from equipment damage when were doing repairs on appliances, because it will have an AC output low. This does not prevent component damage, but it certainly will not help to have bigger problems.
Whats Lamp series , how it works and HOW ?
Since I can remember I use the protection system made with lamp in series , this is an extremely simple tool , easy to make and extremely efficient. When using the lamp in series on a counter-top is possible to avoid serious accidents , further damage equipment , detect serious problems etc. . I always say that every technician and hobbyist must have a lamp standard on your counter-top .
Since the lamp works in series
We never know what is really happening when we have a device with the fuse blown input , can be an internal short circuit or blown fuse for a small outbreak that neither damaged the equipment. Replace the fuse and put the equipment in the electrical network can be risky , and would run the risk of having a new short - circuit, burns again the input fuse or worse.
Not to mention the equipment and appliances that do not have fuse, you would be taking a risk on these test equipment , without support , without protection for your wiring, it could even cause an explosion or fire . These times is that the use of a tool that had the ability to diagnose faults such as excessive consumption and short - circuit current limiting and not letting something more serious occurs with the equipment is necessary and indispensable on the bench .
It is precisely what the lamp in series makes it limits the electrical current ( according to the lamp power / watts ) , with all this we prevent current from passing to the unit , it will not have a blown fuse input and also we will not risk further damage the appliance , the power grid and safeguard the user of an explosion and fire .
How to make a lamp in series
The lamp in series bench if analyzed in a technical way , is a resistive load , we can easily replace the bulb wire resistors , but besides being more expensive , it has the advantage of a visual monitoring because the lamp increases brightness according to the increased consumption of the device under test . If the instrument is shorted visual indication will be the total brightness of the lamp . The resistive load does not affect the operation of the appliance , it means that he will usually work if connected in series with a lamp .
![Lamp]()
In Figure 3 we have a power strip circuit which uses a lamp in the series. The ideal is to have some lamps with different devices to test at least one of 40, 60, 100, 150 Watts power. There is no rule, but to test a device with less than 40 Watts consumption use the lamp 40 Watts or 60 Watts to test device with consumption of more than 40 Watts to 80 Watts lamps use 60 Watts and 100 Watts and consumption above 100 Watts 150 Watts use the lamp. But it has the technical decision in accordance with the terms of the apparatus and its use.
Using the Lamp series
The operating mode of the lamp in series is simple , lets assume that you have a sound system that has burned the fuse AC input , first lets replace that input fuse with another of equal value and connect equipment in lamp series.
If it is the case replace the lamp with an ideal power for the equipment . Surrounded by all the care and protection switch on the device , and make note of the brightness of the lamp .
The amount of glow will be important for the detection of the problem , if the lamp light with maximum brightness , surely remains short and the circuit should be checked more carefully . Components as the primary winding and secondary winding of the transformer , rectifier diodes , signs of overheating, smoke , components changed , jaded or leaking characteristics should be measured and analyzed .
To the extent that you are detecting problems , reconnect the appliance bulb in series . If the lamp brightness decrease , this is the time to connect the unit directly to the grid without the lamp in series .
But if the lamp does not light when the power is turned on , it is a sign that the short may have caused the burning of essential components for the source , as processor can have open or capacitors and integrated circuits oscillators in the case of switching power supplies .
Electrical protective circuit for Counter tops
In Figure 1 we have the complete scheme using the two protection circuits suggested, the lamp in series and the isolation transformer.
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Electrical protective circuit for Counter top (Figure 1)
Operation of electrical protection Bench
We can increment a counter with two simple circuits that will display its operation and how to build. One is the isolation transformer, which serves mainly to avoid electric shocks during construction or repair of circuits that are energized, such as switching power supplies, etc.. The other protection circuit bench is the lamp in series, a tool able to avoid further damage to electronic equipment. With just a light bulb in series with the AC mains and the circuit to be tested or repaired can avoid further damage in case of short circuit.
Isolation transformer easy and cheap
What is an isolation transformer
Isolation transformer as the name implies, isolates the mains of an appliance or power network, it depends on your usage. Various devices and old appliances, or even modern does not have transformer, they use a direct source, where coach or even curious how we run the risk of a shock, which in some cases can be fatal.
.png)
Isolation transformer (figure 2)
In Figure 2 we see a typical circuit power strip with an isolation transformer, the transformer primary is connected to AC mains that has a "live" phase and another phase neutral or earth (were not talking about the central ground pin ). This means that the mains 110 Volts AC (127 Volts) has a phase that is in the neutral or ground potential. The fatal crash occurs precisely for the reason that when you play barefoot or grounded the living phase of the network.
Isolation Transformer
Already with the transformer T1 in its secondary, none of the terminals is grounded, if you accidentally touch one or other of the two wires of the secondary you will not receive shock. But if you touch both simultaneously you will receive a shock which can be fatal, but it is just touching the two at once.
Making our own isolation transformer
In Figure 1 we have a low cost circuit, this circuit uses two transformers, T1 and T2 are two common transformers, need not be equal, but must have the same tensions, the primary with the desired voltage, 110 volts, or both and the secondary 12 volt type 12v-0v-12v. The connection is simple, the secondary of T1 is connected to the secondary of T2. The chain should be at least 5 amps for a good performance.
The isolation transformer also keeps us away from equipment damage when were doing repairs on appliances, because it will have an AC output low. This does not prevent component damage, but it certainly will not help to have bigger problems.
Whats Lamp series , how it works and HOW ?
Since I can remember I use the protection system made with lamp in series , this is an extremely simple tool , easy to make and extremely efficient. When using the lamp in series on a counter-top is possible to avoid serious accidents , further damage equipment , detect serious problems etc. . I always say that every technician and hobbyist must have a lamp standard on your counter-top .
Since the lamp works in series
We never know what is really happening when we have a device with the fuse blown input , can be an internal short circuit or blown fuse for a small outbreak that neither damaged the equipment. Replace the fuse and put the equipment in the electrical network can be risky , and would run the risk of having a new short - circuit, burns again the input fuse or worse.
Not to mention the equipment and appliances that do not have fuse, you would be taking a risk on these test equipment , without support , without protection for your wiring, it could even cause an explosion or fire . These times is that the use of a tool that had the ability to diagnose faults such as excessive consumption and short - circuit current limiting and not letting something more serious occurs with the equipment is necessary and indispensable on the bench .
It is precisely what the lamp in series makes it limits the electrical current ( according to the lamp power / watts ) , with all this we prevent current from passing to the unit , it will not have a blown fuse input and also we will not risk further damage the appliance , the power grid and safeguard the user of an explosion and fire .
How to make a lamp in series
The lamp in series bench if analyzed in a technical way , is a resistive load , we can easily replace the bulb wire resistors , but besides being more expensive , it has the advantage of a visual monitoring because the lamp increases brightness according to the increased consumption of the device under test . If the instrument is shorted visual indication will be the total brightness of the lamp . The resistive load does not affect the operation of the appliance , it means that he will usually work if connected in series with a lamp .
.png)
Lamp in series (Figure 3)
In Figure 3 we have a power strip circuit which uses a lamp in the series. The ideal is to have some lamps with different devices to test at least one of 40, 60, 100, 150 Watts power. There is no rule, but to test a device with less than 40 Watts consumption use the lamp 40 Watts or 60 Watts to test device with consumption of more than 40 Watts to 80 Watts lamps use 60 Watts and 100 Watts and consumption above 100 Watts 150 Watts use the lamp. But it has the technical decision in accordance with the terms of the apparatus and its use.
Using the Lamp series
The operating mode of the lamp in series is simple , lets assume that you have a sound system that has burned the fuse AC input , first lets replace that input fuse with another of equal value and connect equipment in lamp series.
If it is the case replace the lamp with an ideal power for the equipment . Surrounded by all the care and protection switch on the device , and make note of the brightness of the lamp .
The amount of glow will be important for the detection of the problem , if the lamp light with maximum brightness , surely remains short and the circuit should be checked more carefully . Components as the primary winding and secondary winding of the transformer , rectifier diodes , signs of overheating, smoke , components changed , jaded or leaking characteristics should be measured and analyzed .
To the extent that you are detecting problems , reconnect the appliance bulb in series . If the lamp brightness decrease , this is the time to connect the unit directly to the grid without the lamp in series .
But if the lamp does not light when the power is turned on , it is a sign that the short may have caused the burning of essential components for the source , as processor can have open or capacitors and integrated circuits oscillators in the case of switching power supplies .
Electrical protective circuit for Counter tops
In Figure 1 we have the complete scheme using the two protection circuits suggested, the lamp in series and the isolation transformer.
Attention!
Some equipment may not be connected in series lamp. These devices did not function smoothly even when used in series with the lamp. Article in All About the Lamp Usage in the Series Electronically you will find more information about the videos with lamps in series. In addition to a secure bench, safety rules will keep you away from the dangers of electricity, most accidents are preventable. Accidents do not happen without a cause, and most accidents are the result of not following operational security procedures. Read our disclaimer site.
Wednesday, October 15, 2014
Simple RF Transmitter for PIR Sensors Circuit Diagram
This is the Simple RF Transmitter for PIR Sensors Circuit Diagram.
![]( "Simple")
Wednesday, September 24, 2014
Active Bass Enhancer with Correction Circuit for Subwoofers
Active loudspeakers offer the only way f obtaining good bass reproduction from inexpensive or small enclosures.
The design described does not make use, therefore, of large, heavy enclosures to obtaion a good result, but of acoustic feedback. A microphone placed in close proximity of the bass drive unit unfailingly registers every movement of the loud-speaker. It is, of course, important that proper attention is paid to the maximum movement of the speaker.
The microphone output is coupled . into the negative feedback loop ofthe output amplifier. In this way, the input sig- nal to the amplifier is compared with the acoustic signal produced by the speaker. In practice, this arrangement appears to work well only with low-frequency signals. Experiments have shown that if the microphone is placed about 10 mm from the cone of the woofer, signals at e frequencies of up to 500 Hz are fed back faithfully.
To make absolutely certain of correct operation, in the present circuit the upper frequency has been set to 300 Hz; above it, the correcting action gradually ceases. Note, however, that the phase behaviour of the loudspeaker is corrected also for signals above 300 Hz. lf the change-over frequency ofthe cross- over filter ofthe loudspeaker lies at 300 Hz, it is advisable to make the cut-off frequency ofthe present circuit, determined by R6-C8, lower than 300 Hz. The gain of lC2 over the operating range of the circuit is 20 dB, which reduces to 0 dB for frequencies above 300 Hz. This amplifier, which provides the correction up to the cut~off point, also serves as buffer for the microphone signal.
Preset Pl serves to set the signal level on the basis of the power rating of the n outpu amplifier and the efficiency of the microphone. lf this control is set too high, corection is also applied to frequencies above the cut-off point; if it is set too low, little correction will be applied and signals between 20 Hz and 300 Hz will increase along a standard lst order characteristic. The choice of microphone is a matter of some experimentation, particularly with high-power amplifiers.
That used in the proposed subwoofer bass enhancer prototype proved to work well with low-power systems with a relatively low efficiency. If another type is used, make sure that the potential across the microphone is about half the supply voltage. This is arranged by R8 and R9. Also make sure that the cut-off point set by P1-C9 remains well below 20 Hz (no signal at P1 results in an increase of the final amplification). The frequency up to which the microphone signal is compensated is determined by R8-P1-Cm.
This time-constant must be equal to R6-C8. The present circuit can magnify frequencies down to 20 Hz by roughly 20 dB. Since most loudspeakers cannot cope with that frequency, the circuit includes a 3rd order Butterworth section with a cut-off point of 37 Hz.
This frequency may be altered by changing the values of C1, C2, and C3. This filter prevents the loud-speaker being loaded with signals which it cannot reproduce. The bass correction circuit is of particular use with active loud speaker systems.M2 makes sure that the loudspeaker phase is sh ifted by l80° to prevent positive feedback. This may be done by adding an inverter-buffer before K2. The circuit draws about t5 mA, of which only 0.25 mA is drawn by the microphone.
The design described does not make use, therefore, of large, heavy enclosures to obtaion a good result, but of acoustic feedback. A microphone placed in close proximity of the bass drive unit unfailingly registers every movement of the loud-speaker. It is, of course, important that proper attention is paid to the maximum movement of the speaker.
The microphone output is coupled . into the negative feedback loop ofthe output amplifier. In this way, the input sig- nal to the amplifier is compared with the acoustic signal produced by the speaker. In practice, this arrangement appears to work well only with low-frequency signals. Experiments have shown that if the microphone is placed about 10 mm from the cone of the woofer, signals at e frequencies of up to 500 Hz are fed back faithfully.
To make absolutely certain of correct operation, in the present circuit the upper frequency has been set to 300 Hz; above it, the correcting action gradually ceases. Note, however, that the phase behaviour of the loudspeaker is corrected also for signals above 300 Hz. lf the change-over frequency ofthe cross- over filter ofthe loudspeaker lies at 300 Hz, it is advisable to make the cut-off frequency ofthe present circuit, determined by R6-C8, lower than 300 Hz. The gain of lC2 over the operating range of the circuit is 20 dB, which reduces to 0 dB for frequencies above 300 Hz. This amplifier, which provides the correction up to the cut~off point, also serves as buffer for the microphone signal.
Preset Pl serves to set the signal level on the basis of the power rating of the n outpu amplifier and the efficiency of the microphone. lf this control is set too high, corection is also applied to frequencies above the cut-off point; if it is set too low, little correction will be applied and signals between 20 Hz and 300 Hz will increase along a standard lst order characteristic. The choice of microphone is a matter of some experimentation, particularly with high-power amplifiers.
That used in the proposed subwoofer bass enhancer prototype proved to work well with low-power systems with a relatively low efficiency. If another type is used, make sure that the potential across the microphone is about half the supply voltage. This is arranged by R8 and R9. Also make sure that the cut-off point set by P1-C9 remains well below 20 Hz (no signal at P1 results in an increase of the final amplification). The frequency up to which the microphone signal is compensated is determined by R8-P1-Cm.
This time-constant must be equal to R6-C8. The present circuit can magnify frequencies down to 20 Hz by roughly 20 dB. Since most loudspeakers cannot cope with that frequency, the circuit includes a 3rd order Butterworth section with a cut-off point of 37 Hz.
This frequency may be altered by changing the values of C1, C2, and C3. This filter prevents the loud-speaker being loaded with signals which it cannot reproduce. The bass correction circuit is of particular use with active loud speaker systems.M2 makes sure that the loudspeaker phase is sh ifted by l80° to prevent positive feedback. This may be done by adding an inverter-buffer before K2. The circuit draws about t5 mA, of which only 0.25 mA is drawn by the microphone.
Tuesday, September 16, 2014
Power Line Modem Circuit for Home Automation Application
Imagine you have a master controller device that control other devices in your house, and you don’t need to install any additional wires to facilitate the data communication between the master controller and the controlled devices. Yes you’s life will be easier since all you need is just plugging your devices into your power line outlet, the devices will communicate each-other through the power line while using the line to enpower them! The secret is the powerline modem, a modem that use the powerline wiring as their media to exchange the data. Philips Semiconductors has a single chip powerline modem solution, a TDA5051A IC chip. Here is the schematic diagram of this powerline modem circuit.
The TDA5051A single chip power line modem is equipped with protection of its output power stage and automatic gain control (AGC) of input signal. With simple coupling network, this power line modem is compliance with EN50065-1 power line communication standard.This power line modem circuit uses ASK (amplitude shift keying) for the modulation, and operate on 5V supply.
Monday, September 15, 2014
Microphone for Computer
Friday, June 6, 2014
Regulators for Battery Powered Systems
Maxim describes various SMPS regulator topologies for battery powered systems. Isolated and non-isolated topologies are covered. This tutorial presents an overview of regulator topologies for battery-powered equipment. The discussion covers linear regulators, charge pumps, buck and boost regulators, inverters, and flyback designs. The importance of peak current is explained, and schematics of each topology are shown. [Link]
An LCD Clock Kit Suitable for Beginners with Open Source Arduino Firmware
Simpleclock is an easy to assemble attractive 4-digit 7-segment LED display clock with temperature and alarm function. It is available in three display colors: Red, Blue and White. It comes as a kit of through-the-hole parts and can be soldered by any person with basic soldering experience. An attractive acrylic stand is included. [Link]
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