Friday, September 19, 2014
Build a Auto Anti Hijack Alarm Circuit Diagram
This Auto Anti-Hijack Alarm Circuit Diagram was designed primarily for the situation where a hijacker forces the driver from the vehicle. If a door is opened while the ignition is switched on - the circuit will trip. After a few minutes delay - when the thief is at a safe distance - the Siren will sound.
Where it differs from the first two alarms - is in what happens next. Im obliged to Victor Montanez from the USA who suggested that the engine cut-out should not operate - until the vehicle comes to a stop. That way - the engine will not fail suddenly or unexpectedly. And the hijacker will retain control.
I havent been able to implement Victors excellent suggestion completely - because I couldnt think of a simple, reliable and universally applicable way of sensing when the vehicle has come to a stop.
Instead - I have postponed engine failure until the ignition is switched off. Once the thief turns off the ignition - the engine will not re-start. Clearly - there is no certainty as to when this will occur. But I think it will occur sooner rather than later. Because theres a strong possibility that the hijacker will turn off the ignition - in an attempt to silence the siren.
Auto Anti-Hijack Alarm Circuit Diagram
As well as acting as a Hijack Alarm - this circuit offers some added protection. Like the Enhanced Hijack Alarm - it incorporates Jeff Chias suggestion. That is - every time the ignition is switched on - the alarm will trip. So it will protect the vehicle whenever you leave it unattended with the ignition switched off - even overnight in your driveway.
Importance
Before fitting this or any other engine cut-out to your vehicle - carefully consider both the safety implications of its possible failure - and the legal consequences of installing a device that could cause an accident. If you decide to proceed - you will need to use the highest standards of materials and workmanship.
Notes
Youre going to trip this alarm unintentionally. When you do - the LED will light and the Buzzer will give a short beep. The length of the beep is determined by C4. Its purpose is to alert you to the need to push the reset button. When you push the button - the LED will switch-off. Its purpose is to reassure you that the alarm has in fact reset.
If the reset button is not pressed then - about 3 minutes later - both the Siren and the Buzzer will sound continuously. The length of the delay is set by R8 & C5. For extra effect - fit a second siren inside the vehicle. With enough noise going on - you may feel that its unnecessary to fit the engine cut-out. In which case - you can leave out C7, D8, R12, R13, Ty1 & Ry2.
When the ignition is switched on - C3 & R4 are responsible for tripping the alarm. By taking pin 1 low momentarily - they simulate the opening of a door. If you dont want the alarm to trip every time you turn on the ignition - simply leave out C3 & R4.
Because the voltage on C3 may be reversed - the capacitor needs to be non-polarized. But connecting two regular 22uF capacitors back to back as shown - will work just as well. Because non-polarized capacitors are not widely available - the prototype was built using two polarized capacitors.
To reset the circuit you must - EITHER turn off the ignition - OR close all of the doors - before you press the reset button. While BOTH the ignition is on - AND a door remains open - the circuit will NOT reset.
The reset button carries virtually no current - so any small normally-open switch will do. Eric Vandel from Canada suggests using a reed-switch hidden behind (say) the dash - and operated by a magnet. I think this is an excellent idea. As Eric said in his email: - "... that should keep any thief guessing for a while."
Veroboard Layout
How you prevent the engine from starting is up to you. It should happen when Ry2 de-energizes. The contacts of Ry2 are too small to do the job themselves. So use them to switch the coil of a larger relay. Remember that the relay must be suitable for the current its required to carry. Choose one specifically designed for automobiles - it will be protected against the elements - and will give the best long-term reliability. You dont want it to let you down on a cold wet night - or worse still - in fast moving traffic!!! Remember also that you must fit a 1N4001 diode across YOUR relays coil - to prevent damage to the Cmos IC
YOUR relay should drop-out when Ry2 de-energizes. Wire YOUR relay so that when it drops-out the engine will not start. Because turning-off the ignition will cause both Ry2 and YOUR relay to de-energize - the standby current will be low - and the engine will be disabled while the vehicle is parked.
The circuit board must be protected from the elements. Dampness or condensation will cause malfunction. Fit a 1-amp in-line fuse AS CLOSE AS POSSIBLE to your power source. This is VERY IMPORTANT. The fuse is there to protect the wiring - not the components on the circuit board. Please note that I am UNABLE to help any further with either the choice of a suitable relay - or with advice on installation.
Both the Siren and the Buzzer will go on sounding until the alarm is reset. The circuit is designed to use an electronic Siren drawing up to about 500mA. Its not usually a good idea to use the vehicles own Horn because it can be easily located and disconnected. However, if you choose to use the Horn, remember that Ry1 is too small to carry the necessary current. Connect the coil of a suitably rated relay to the "Siren" output. This can then be used to sound the Horn.
Friday, January 10, 2014
Super Hi Fi Headphone Amplifier Circuit Diagram
This is a Super Hi-Fi Headphone Amplifier Circuit Diagram.
Super Hi-Fi Headphone Amplifier Circuit Diagram
Super Hi-Fi Headphone Amplifier Circuit Diagram
Most mobile phones on the market today or a single CPU
Most mobile phones on the market today or a single CPU.
S40, nokia mobile phone operating system developed by the face of low-end customers, support kjava the development, its processor efficiency is not high, low memory, screen size 128 * 128. S60, is based on the Symbian operating system, that is, before the epoc processor arm9 high processing efficiency, considerable memory, screen size is 208 * 176 support both kjava and C + + development. S90, is a handheld device, the Symbian operating system, but robust, equivalent to a PDA. In fact, says the technology to the S40 with the S60 is the difference between system platforms, like WIN98 now WIN2000 but the phone unlike the PC, the screen size is indeed a mark. The technical review of Cell Phone Jammers is important too.In order to prevent dust and foreign matter into the sound chamber, can be affixed inside the enclosure dust network, for the beautiful, the sound hole on the outside can be affixed to the nickel plate, PC tablets, and other decorative pieces, small mesh diameter of the nickel plate 0.3mm, nickel plate, inside the enclosure can not affixed to the dust network. speaker after tune the low frequency part of the main impact of ringtones, high frequency part is smaller, you can not do the requirements. In order to get good bass, no component interference on the motherboard, you can use the antenna bracket and motherboard with affixed foam speaker Tune closed after the formation of the sound chamber in order to get more awesome bass vibration effects, speakers, family speaker.
Give priority to the purchase and the successful capital increase, will promote Symbian to the next stage of growth. Today, shareholders and unified commitment to a strong proof of the Symbian are fully capable to meet the needs of current and future industry development. Yoshiaki Kushiki, president of Panasonic Mobile Communications, said: "Panasonic is fully exercised the right of first refusal to the Psion shares. This shows our strong commitment to the independence of Symbian through a broad, balanced and equity basis to maintain this independence is critical This will be conducive to the Symbian operating system in the mobile phone industry to maintain its objective criteria, and continue to receive long-term support and backing of a number of manufacturers and network operators. " The individual quality assurance can not assure the quality of Cell Phone Jammers totally.
We must consider the draft between the various shell upper and lower shell along the mold more than 3 degrees, metal decorative pieces around the draft to be more than 5 degrees. Appearance of the side is the outer contour surface of the phone, a good curve out surface, described line be sure to close the ID of the wireframe ID creative respect the basic accomplishment of structural engineers and lines but also try smoothing as much as possible uniform change of curvature, draft angle should be taken into account, if the ID of the line pull draft angle and structural requirements are inconsistent, and ID consultation appearance by the structure in the description line directly to fix the draft angle of the contour lines, if the plastic shell to retain the draft angle is larger ID of the creative destruction plastic mold, you might consider doing the four sides of line spaces, after all, the phone is a high-end consumer goods, this investment is worth. It is to strengthen the quality control of Cell Phone Jammers .
Read More..
S40, nokia mobile phone operating system developed by the face of low-end customers, support kjava the development, its processor efficiency is not high, low memory, screen size 128 * 128. S60, is based on the Symbian operating system, that is, before the epoc processor arm9 high processing efficiency, considerable memory, screen size is 208 * 176 support both kjava and C + + development. S90, is a handheld device, the Symbian operating system, but robust, equivalent to a PDA. In fact, says the technology to the S40 with the S60 is the difference between system platforms, like WIN98 now WIN2000 but the phone unlike the PC, the screen size is indeed a mark. The technical review of Cell Phone Jammers is important too.In order to prevent dust and foreign matter into the sound chamber, can be affixed inside the enclosure dust network, for the beautiful, the sound hole on the outside can be affixed to the nickel plate, PC tablets, and other decorative pieces, small mesh diameter of the nickel plate 0.3mm, nickel plate, inside the enclosure can not affixed to the dust network. speaker after tune the low frequency part of the main impact of ringtones, high frequency part is smaller, you can not do the requirements. In order to get good bass, no component interference on the motherboard, you can use the antenna bracket and motherboard with affixed foam speaker Tune closed after the formation of the sound chamber in order to get more awesome bass vibration effects, speakers, family speaker.
Give priority to the purchase and the successful capital increase, will promote Symbian to the next stage of growth. Today, shareholders and unified commitment to a strong proof of the Symbian are fully capable to meet the needs of current and future industry development. Yoshiaki Kushiki, president of Panasonic Mobile Communications, said: "Panasonic is fully exercised the right of first refusal to the Psion shares. This shows our strong commitment to the independence of Symbian through a broad, balanced and equity basis to maintain this independence is critical This will be conducive to the Symbian operating system in the mobile phone industry to maintain its objective criteria, and continue to receive long-term support and backing of a number of manufacturers and network operators. " The individual quality assurance can not assure the quality of Cell Phone Jammers totally.
We must consider the draft between the various shell upper and lower shell along the mold more than 3 degrees, metal decorative pieces around the draft to be more than 5 degrees. Appearance of the side is the outer contour surface of the phone, a good curve out surface, described line be sure to close the ID of the wireframe ID creative respect the basic accomplishment of structural engineers and lines but also try smoothing as much as possible uniform change of curvature, draft angle should be taken into account, if the ID of the line pull draft angle and structural requirements are inconsistent, and ID consultation appearance by the structure in the description line directly to fix the draft angle of the contour lines, if the plastic shell to retain the draft angle is larger ID of the creative destruction plastic mold, you might consider doing the four sides of line spaces, after all, the phone is a high-end consumer goods, this investment is worth. It is to strengthen the quality control of Cell Phone Jammers .
Electrical Schematic Symbols
Electrical Schematic Symbols:
Electrical circuit schematic symbols are graphical sign, that is used to design electronic, electrical circuit schematic diagram. There is a quite adequate collection of symbol for electrical, electronic circuit. You can use this high quality schematic symbols to design your own schematic circuit diagram. Download high quality electrical schematic symbols image. |
| High Quality Electrical Schematic Symbols |
Click on the image of Schematic Symbols to enlarge.
Special thanks to the author of www.ARRL.org for these high quality electrical schematic symbols.
This circuit schematic symbols are for educational purposes only, not for any industrial use.
This circuit schematic symbols are for educational purposes only, not for any industrial use.
Thursday, December 26, 2013
Battery Equality Monitor
Almost all 24V power systems in trucks, 4WDs, RVs, boats, etc, employ two series-connected 12V lead-acid batteries. The charging system can only maintain the sum of the individual battery voltages. If one battery is failing, this circuit will light a LED. Hence impending battery problems can be forecast. The circuit works by detecting a voltage difference between the two series connected 12V batteries. Idle current is low enough to allow the unit to be permanently left across the batteries.
R1 = 2.K
R2 = 4.7K
R3 = 39K
R4 = 39K
R5 = 1.5K
R6 = 1.5K
Q1 = BC547
Q2 = BC547
Q3 = BC557
D1 = 3mm Red LED
D2 = 3mm GreenLED
B1 = DC 12 Volt
B2 = DC 12 Volt
Tuesday, December 24, 2013
cell phone jammer will have the normal dissipation as the working time accumulates
In addition, we can uninstall all the software, and then see if there is no similar "system
error". If there is no similar "system error" and then the lattice machine. Various GSM, CDMA cell phones including PAS, 3G can be shielded through cell phone jammer .
Is to set the error causes the device is not working: do not have lattice machine, as long as you restore the factory settings, Note that this command only to restore the settings, different from
the lattice machine, after the resumption of business card holder, pictures, documents, etc. all still there, just set to restore some friends set incorrectly I do not know how to change it back,
you can use this command. After the above five ways to exclude, if the cell phone is still a problem, often re-start, the machine can not start or turn on the power but you can not enter the
standby or standby process only bright for a few seconds, the cell phone on their own restart repeatedly after turned off state, the Department of the serious problems to the general grid machine.
cell phone jammer will have the normal dissipation as the working time accumulates.
Note: in the grid before formatting the data before backup: No matter what way lattice machine, format, all cell phones C drive is restored to the factory when the state, of course, include your
text messages and cell phone book, so the formatting before they want to keep the program or other documents should be retained. Available reader to operate. To determine in advance you want to
back up data, such as SMS, Contacts, Calendar, and the software installed. Lattice machine should be backed up? Firstly I should say is not backed up as possible, because often you backup is the
wrong place. Backup some of the card holder must be on the line, the personality machine will only backup the card holder and procedures for the classification of documents.
Mostly software presentations and to use the E text. Mostly software presentations and use their softwares home page link. Mostly software presentations and to use the E text. General decryption
introduction can be used to open the handwritten, and sometimes there will bear the registration code of the software. Software to back up data, which will bear the registration information of the
software. Can extract the first on the PC Take a look, if there are * sis suffix software to unlock and install the SIS file sent to your cell phone, if the decompression is open, which have "META
-INF folder also There are a lot of other files, the Java software, general JAR format of java is a special format, suffix is *. jar, RAR compression software that can be mistaken for a rar format
on a PC, you do not unpack. cell phone jammer of high quality will gain more and more customers.
Read More..
error". If there is no similar "system error" and then the lattice machine. Various GSM, CDMA cell phones including PAS, 3G can be shielded through cell phone jammer .
Is to set the error causes the device is not working: do not have lattice machine, as long as you restore the factory settings, Note that this command only to restore the settings, different from
the lattice machine, after the resumption of business card holder, pictures, documents, etc. all still there, just set to restore some friends set incorrectly I do not know how to change it back,
you can use this command. After the above five ways to exclude, if the cell phone is still a problem, often re-start, the machine can not start or turn on the power but you can not enter the
standby or standby process only bright for a few seconds, the cell phone on their own restart repeatedly after turned off state, the Department of the serious problems to the general grid machine.
cell phone jammer will have the normal dissipation as the working time accumulates.
Note: in the grid before formatting the data before backup: No matter what way lattice machine, format, all cell phones C drive is restored to the factory when the state, of course, include your
text messages and cell phone book, so the formatting before they want to keep the program or other documents should be retained. Available reader to operate. To determine in advance you want to
back up data, such as SMS, Contacts, Calendar, and the software installed. Lattice machine should be backed up? Firstly I should say is not backed up as possible, because often you backup is the
wrong place. Backup some of the card holder must be on the line, the personality machine will only backup the card holder and procedures for the classification of documents.
Mostly software presentations and to use the E text. Mostly software presentations and use their softwares home page link. Mostly software presentations and to use the E text. General decryption
introduction can be used to open the handwritten, and sometimes there will bear the registration code of the software. Software to back up data, which will bear the registration information of the
software. Can extract the first on the PC Take a look, if there are * sis suffix software to unlock and install the SIS file sent to your cell phone, if the decompression is open, which have "META
-INF folder also There are a lot of other files, the Java software, general JAR format of java is a special format, suffix is *. jar, RAR compression software that can be mistaken for a rar format
on a PC, you do not unpack. cell phone jammer of high quality will gain more and more customers.
Sunday, December 22, 2013
Dual Power Amplifier
As readers will know, there are already several power amplifier projects, two using IC power amps (aka power opamps). Both have been popular, and this project is not designed to replace either of them. However, it is significantly smaller than the others, so it makes building a multiple amp unit somewhat easier because the space demand is much lower. Its quite simple to include 4 amps (two boards) into a small space, but be aware that good heatsinking is essential if you expect to run these amps at significant power levels.
Photo of Completed P127 Board
The TDA7293 IC uses a MOSFET power stage, where the others featured use bipolar transistors. The main benefit of the MOSFET stage is that it doesnt need such radical protection circuitry as a bipolar stage, so unpleasant protection circuit artefacts are eliminated. There are no apparent downsides to the TDA7293, although it was found that one batch required a much higher voltage on the Standby and Mute pins than specified, or the amps would not work. This is not a limitation, since both are tied to the positive supply rail and are therefore disabled. This particular project has been planned for a long time, but for some reason I never got around to completing the board or the project description. This is now rectified, and its ready to "rock and roll". The board is very small - only 77 x 31mm, so getting it into tight spaces is easy ... provided adequate heatsinking is available of course.
Description
The TDA7293 has a bewildering number of options, even allowing you to add a second power stage (in another IC) in parallel with the main one. This improves power into low impedance loads, but is a rather expensive way to get a relatively small power increase. It also features muting and standby functions, although Ive elected not to use these.
The schematic is shown in Figure 1, and is based on the PCB version. All unnecessary functions have been disabled, so it functions as a perfectly normal power amplifier. While the board is designed to take two TDA7293 ICs, it can naturally be operated with only one, and the PCB is small enough so that this is not an inconvenience. A LED is included to indicate that power is available, and because of the low current this will typically be a high brightness type.
Figure 1 - Schematic of Power Amplifier (One Channel Shown)
The IC has been shown in the same format thats shown in the data sheet, but has been cleaned up for publication here. Since there are two amps on the board, there are two of most of the things shown, other than the power supply bypass caps and LED "Power Good" indicator. These ICs are extremely reliable (as are most power amp ICs), and to reduce the PCB size as much as possible, fuse clips and fuses have not been included. Instead, there are fusible tracks on the board that will fail if there is a catastrophic fault. While this is not an extremely reliable fuse, the purpose is to prevent power transformer failure, not to protect the amplifiers or PCB. I normally use a gain of 23 (27dB) for all amplifiers, and the TDA7293 is specified for a minimum gain of 26dB, below which it may oscillate. Although this is only a small margin, tests so far indicate that the amp is completely stable. If you wish, you may increase the gain to 28 (29dB) to give a bit more safety margin. To do this, just change the input and feedback resistors (R3A/B and R4A/B) from 22k to 27k.
The circuit is conventional, and is very simple because all additional internal functions are unused. The LED is optional, and if you dont think youll need it, it may be omitted, along with series resistor R3. All connections can be made with plugs and sockets, or hard wired. In most cases, I expect that hard wiring will be the most common, as the connectors are a pain to wire, and add unnecessary cost as well as reduce reliability. The TDA7293 specifications might lead you to believe that it can use supply voltages of up to ±50V. With zero input signal (and therefore no output) it might, but I dont recommend anything greater than ±35V if 4 ohm loads are expected, although ±42V will be fine if you can provide good heatsinking. In general, the lower supply voltage is more than acceptable for 99% of all applications, and higher voltages should not be used unless there is no choice. Naturally, if you can afford to lose a few ICs to experiments, then go for the 42V supplies (obtained from a 30+30V transformer).
Construction
Because of the pin spacings, these ICs are extremely awkward to use without a PCB. Consequently, I recommend that you use the ESP board because it makes building the amplifier very simple. The PCBs are double sided with plated-through holes, so are very unforgiving of mistakes unless you have a good solder sucker. The best way to remove parts from a double sided board is to cut the pins off the component, then remove each pin fragment individually. This is obviously not something youd wish to do if a power amp IC were installed incorrectly, since it will be unusable afterwards.
Figure 2 - TDA7293V Pinouts
The diagram above shows the pinouts for the TDA7293V (the "V" means vertical mounting). Soldering the ICs must be left until last. Mount the ICs on your heatsink temporarily, and slide the PCB over the pins. Make sure that all pins go through their holes, and that there is no strain on the ICs that may try to left the edge off the heatsink. When ICs and PCB are straight and aligned, carefully solder at least 4 pins on each IC to hold them in place. The remaining pins can then be soldered. Remember, if you mess up the alignment at this point in construction, it can be extremely difficult to fix, so take your time to ensure there are no mistakes. This amplifier must not be connected to a preamp that does not have an output coupling capacitor. Even though there is a cap in the feedback circuit, it can still pass DC because there is no input cap on the PCB. I normally include an input cap, but the goal of this board was to allow it to fit into the smallest space possible, and the available board space is not enough to include another capacitor. A volume control (typically 10k log/ audio taper) may be connected in the input circuit if desired.
Note that the metal tab of the TDA7293 is connected to the -Ve supply, so must be insulated from the heatsink. The more care you take with the mounting arrangement, the better. While you can use a screw through an insulating bush and a piece of mica to insulate the tab, a better alternative is to use a clamping bar of some kind. How you go about this depends a lot on your home workshop tools and abilities, but one arrangement Ive found highly satisfactory is a suitable length of 6.25mm square solid steel bar. This is very strong, and allows good pressure on the mica (or Kapton) for maximum heat transfer. Naturally, heatsink compound is absolutely essential. Do not be tempted to use silicone insulation washers unless you are using the amp at very low supply voltages (no more than ±25V). Its thermal transfer characteristics are not good enough to allow the amp to produce more than about 10 - 20W of music, and even that can be taxing for silicone washers. The amp will shut down if it overheats, but that curtails ones listening enjoyment until it cools down again.
Power Supply
A suitable power supply is shown below, and is completely unremarkable in all respects. The transformer may be a conventional (E-I) laminated type or a toroid. The latter has the advantage of lower leakage flux, so will tend to inject less noise into the chassis and wiring. Conventional transformers are usually perfectly alright though, provided you take care with the mounting location. The bridge rectifier should be a 35A 400V type, as they are cheap, readily available and extremely rugged. Electrolytic capacitors should be rated at 50V. The cap connected across the transformer secondary (C4) should be rated at 275V AC (X Class), although a 630V DC cap will also work. This capacitor reduces "conducted emissions", namely the switching transients created by the diodes that are coupled through the transformer onto the mains supply. The power supply will work without this cap, and will most likely pass CE and C-Tick tests as well, but for the small added cost you have a bit of extra peace of mind as regards mains noise.
Figure 3 - Suggested Power Supply
The supply shown includes a "loop breaker", which is intended to prevent earth/ ground loops to prevent hum when systems are interconnected. Please be aware that it may not be legal to install this circuit in some countries. The diodes must be high current types - preferably rated at no less than 3A (1N5401 or similar). The loop breaker works by allowing you to have the chassis earthed as required in most countries, but lets the internal electronics "float", isolated from the mains earth by the 10 ohm resistor. RF noise is bypassed by the 100nF cap, and if a primary to secondary fault develops in the transformer, the fault current will be bypassed to earth via the diodes. If the fault persists and the internal fuse (or main power circuit breaker) hasnt opened, one or both diodes will fail. Semiconductor devices fail short-circuit, so fault current is connected directly to safety earth.
Be very careful when first applying mains power to the supply. Check all wiring thoroughly, verify that all mains connections are protected from accidental contact. If available, use a Variac, otherwise use a standard 100W incandescent lamp in series with the mains. This will limit the current to a safe value if there is a major fault. When the loop breaker is used, all input and output connectors must be insulated from the chassis, or the loop breaker is bypassed and will do nothing useful. The body of a level pot (if used) can be connected to chassis, because the pot internals are insulated from the body, mounting thread and shaft.
Note that the DC ground for the amplifiers must come from the physical centre tap between the two filter caps. This should be a very solid connection (heavy gauge wire or a copper plate), with the transformer centre tap connected to one side, and the amplifier earth connections from the other. DC must be taken from the capacitors - never from the bridge rectifier. The order of the fuse and power switch is arbitrary - they can be in any order, and in many cases the order is determined by the physical wiring of the IEC connector if a fused type is used. With a fused IEC connector, the fuse is before the switch and it cannot be removed while the mains lead is inserted.
I have shown a 2A slow-blow fuse, but this depends on the size and type of transformer and your mains supply voltage. Some manufacturers give a recommended fuse rating, others dont. The fuse shown is suitable for a 150VA transformer at 230V AC, and is deliberately oversized to ensure that it will not be subject to nuisance blowing due to transformer inrush current. A 2A fuse will fail almost instantly if there is a major fault. Make sure that the mains earth (ground) is securely connected to guarantee a low resistance connection that cannot loosen or come free under any circumstances. The accepted method varies from one country to the next, and the earth connection must be made to the standards that apply in your country.
WARNING: This power supply circuit requires experience with mains wiring. Do not attempt construction unless experienced, capable and suitably qualified if this is a requirement where you live. Death or serious injury may result from incorrect wiring.
Never attempt to operate the amplifier without the TDA7293 ICs attached to a heatsink!
Connect to a suitable power supply - remember that the supply earth (ground) must be connected! When powering up for the first time, use 100 ohm 5W "safety" resistors in series with each supply to limit the current if you have made a mistake in the wiring. If available, use a variable bench supply - you dont need much current to test operation, and around 500mA is more than enough. If using a current limited bench supply, the safety resistors can be omitted. Do not connect a speaker to the amplifier at this stage!
Connect to a suitable power supply - remember that the supply earth (ground) must be connected! When powering up for the first time, use 100 ohm 5W "safety" resistors in series with each supply to limit the current if you have made a mistake in the wiring. If available, use a variable bench supply - you dont need much current to test operation, and around 500mA is more than enough. If using a current limited bench supply, the safety resistors can be omitted. Do not connect a speaker to the amplifier at this stage!
If using a normal power supply for the amp tests, apply power (±35V via the safety resistors) and verify that the current is no more than 60mA or so - about 6V across each 100 ohm resistor. No load current can vary, so dont panic if you measure a little more or less. Verify that the DC voltage at both outputs is less than 100mV. Using another 100 ohm resistor in series with a small speaker, or an oscilloscope, apply a sinewave signal at about 400Hz to the input and watch (or listen) for signal. The signal level needs to be adjusted to ensure the amp isnt clipping, and the waveform should be clean, with no evidence of parasitic oscillation or audible distortion. If everything tests out as described, wire the amplifier directly to the power supply and finish off any internal wiring in the amp. Once complete, its ready to use.
Source : www.ecircuitslab.com/.../dual-power-amplifier-using-tda7293.html
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