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]
Small FAT Arduino Library SD Card Reader
The library supports FAT16 formatted SD cards up to 2GB in size. 4GB FAT16 formatted SD cards might work, but is untested. Long file names are not supported. Keep you file names compliant with the old 8.3 standard. The SD card should be connected to the SPI-pins on your Arduino. Pin connections are available in the documentation in the download. [Link]
Color Lights on USB
This project is a remake of an old discolights pod. Original 24V 5W bulbs are changed to 230V 40W with E14 thread. Original driver board has non-typical signal input. This driver is based on the FT245RL chip, a USB-LPT converter – so you can use it with PC applications such as discolitez. Low voltage part is supplied directly from the USB so there is no need to to use any transformer…
Device uses a MOC3041 optotriac and a BT136 triac in a standard application to drive bulbs. Note if you want to use stronger bulbs, like 100W or more, you need to use some little radiators to cool down the triacs. There are 4 channels, 3 are used for bulbs and 4th is used as an extra 230V output – in this case for a mini strobe. You can find 4 goldpins on board, these are a 4 extra output channels – so you can expand device to another optotriacs and triacs to use 4 more 230V devices. To your own safety, use a proper fuse, and remember that device works on a 230V potential. You can use it with 110V devices instead of 230V, no problem. [Link]
Rascal Combines Linux and Arduino
Does this sound familiar to you? After spending many hours on optimizing for speed and memory your super-duper MCU application, you can only conclude that it will not run on an Arduino board. You have built the shield (the Arduino compatible extension board) with your special I/O and you wrote most of the software, but these last functions that should add that finishing touch just don’t fit in the board’s memory. Maybe Rascal can help?
Built around a 400 MHz AT91SAM9G20 ARM9 from Atmel, the Rascal is an open source Linux board compatible with Arduino extension cards or shields. Programming the board is easy thanks to a library written in Python from Pytronics that allows easy access to peripherals and shields. The Rascal’s firmware comes with a web server that can serve as a programming interface; you can write your applications directly in a web browser connected to the Rascal board.[Link]
TV B Gone Ported to PIC 12F1840
Exapod ported TV-B-Gone, the universal TV off button, to the tiny PIC12F1840. He used the free version of the Hi-Tech compiler so the optimizations leave a lot to be desired, but the code only uses 17% of program memory. The prototype was made on a protoboard and an SOIC packaged PIC. [Link]
Arduino Based Low Power Wireless Solution
panStamp is an open source project created for the enthusiasts that love measuring and controlling things wirelessly. panStamps are small wireless boards specially designed to fit in low-power applications, simple to program and simple to work with. With panStamps, you can measure almost everything by simply connecting your panStamp to the sensors, placing a battery and sending wireless data from the first moment.
panStamps are suitable for any kind of project needing remote control and low-power wireless transmissions, including home automation, energy metering, weather monitoring and robot control. If you are one of these three things: a hobbyist, a professional or an end-user, you will find that panStamps provide extreme flexibility and power when creating custom wireless networks. [Link]
Simple MiniCom An Arduino LCD DSLR Remote Control
It’s my first post in English on this blog, just to get to the broader English crowd of the maker world. I’ll present my latest project, the fifth iteration in my quest to create a remote control for my DSLR.
There’s a night-mode, where all the LCD turns red, useful for astro-photography, when you need to be able to look at it without compromising your acquired night vision. The interface is limited to a single rotary knob you can push to validate your choices. It remains easy and intuitive to use even when it’s minus 20°C and it’s pitch black. The output is a standard 3.5mm stereo jack, you can use different cables to control different brand of DSLRs. [Link]
Hg Lamp to a Powerful UV Light Source
I got myself some UV-curable solder mask for my PCB workshop, and as soon as i got it, i discovered that my UV artwork transfer box is totally incapable to activate the UV paint and cure it. I began searching the net for powerful UV lamps, and then it hit me: Some months ago i uploaded a theory regarding the Cold and Hot cathode discharge lamps. During my research for these lamps i found out that they can provide directly visible light (lamps without internal coating), or they produce UV radiation. The lamps that produce UV radiation have an extra coating on their internal surface which glows when excited by the UV rays, thus producing light! [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]
New MEMS Device Generates More Energy From Small Vibrations
Researchers at MIT have designed a novel device the size of a U.S. quarter that harvests energy from low-frequency vibrations, such as those that might be felt along a pipeline or bridge. The tiny energy harvester — known technically as a microelectromechanical system, or MEMS — picks up a wider range of vibrations than current designs, and is able to generate 100 times the power of devices of similar size.
To harvest electricity from environmental vibrations, researchers have typically looked to piezoelectric materials, or PZT, such as quartz and other crystals. Various designs are based on a small microchip with layers of PZT glued to the top of a tiny cantilever beam. As the chip is exposed to vibrations, the beam moves up and down like a wobbly diving board, bending and stressing the PZT layers.
The stressed material builds up an electric charge, which can be picked up by arrays of tiny electrodes. However, the beam itself has a resonant frequency and outside of this frequency, the beam’s response drops off, along with the amount of power that can be generated. [Link]
The stressed material builds up an electric charge, which can be picked up by arrays of tiny electrodes. However, the beam itself has a resonant frequency and outside of this frequency, the beam’s response drops off, along with the amount of power that can be generated. [Link]
Simple Wireless TRIAC Dimmer
This project was used as a wireless light dimmer, but in principle can be used to dim resistive loads and wirelessly turn on/off loads. The current code includes a routine to dim a light bulb in a “heartbeat” pattern, with the heartbeat frequency remotely adjustable.
The top left of the schematic shows the wall outlet (US 120VAC) being stepped down with a small transformer, then full rectified and regulated. This powers the entire board from the wall. The top right shows a microcontroller, ATmega48, its programming header, and a UART connection to the microcontroller (for debugging). The bottom right shows the XBee and its basic voltage regulation (it’s 3.3V), as well as an LED that indicates when the XBee is connected. [Link]
Circuit Design of a Photoflash Unit
A photoflash unit has a simple circuit design: a high-voltage direct current (DC) supply is connected in series with a high-resistance resistor (which we’ll call ‘R1′). This resistor limits the current flow. A capacitor ‘C’ is connected in parallel with a flash lamp. The resistance ‘R2’ of a flash lamp is of small value. The circuit contains a switch between the large resistance ‘R1’ and a small resistance flash lamp ‘R2’, such that it can connect either resistance at any time during the process. [Link]
Making A Self Watering Plant with Arduino
Plants liven up any space by adding a sense of airiness and life. That is – of course – when you don’t forget to water them, and they shrivel up and die. I am very bad at remembering to water plants. That is why I built this self-watering plant to do it for me. Using a soil sensor, and an Arduino-controlled water pump, I have created a system that will never forget to do it.
Instead of remembering to water my plants when the soil goes dry, I only have to remember to once and a while refill the water reservoir. In this way, I have decreased my obligation to these plants and put it off to a much later date. Perhaps further iterations of this device can be connected to a rain barrel so that I won’t even have to worry about refilling my reservoir, and the entire system can be fully automated. [Link]
DIGITAL AUDIO VIDEO INPUT SELECTOR
Need to connect more than one audio-video (AV) source to your colour television? Don’t worry, here’s an AV input expander for your TV. It is inexpensive and easy to construct.
The working of the circuit is simple and straightforward. Whenever 12V DC is applied to the circuit, power-on LED1 glows. Now reset the decade counter by momentarily pressing switch S2 to make Q0 output of IC1 high. LED2 glows to indicate that the circuit is ready to work.Switch S1 is used for selecting a particular audio-video (AV) signal. To select the first AV signal, press switch S1 once. To select the second AV signal, press switch S1 twice. In the same way, you can select the other two signals.
The working of the circuit is simple and straightforward. Whenever 12V DC is applied to the circuit, power-on LED1 glows. Now reset the decade counter by momentarily pressing switch S2 to make Q0 output of IC1 high. LED2 glows to indicate that the circuit is ready to work.Switch S1 is used for selecting a particular audio-video (AV) signal. To select the first AV signal, press switch S1 once. To select the second AV signal, press switch S1 twice. In the same way, you can select the other two signals.
DIGITAL AUDIO/ VIDEO INPUT SELECTOR CIRCUIT DIAGRAM
Momentarily pressing of switch S1 once results in clocking of the decade counter and relay driver transistor T1 conducts to energise relay RL1. Now normally opened (N/O) contacts of two-changeover relay RL1 connect the television set’s inputs to the first AV signal (marked as Video-In 1 and Audio-in 1). LED3 glows to indicate this.
When you press switch S1 twice, the Q2 output of IC1 goes high. Consequently, 2C/O relay RL2 (not shown in the circuit) energises and television inputs are connected to the second AV signal (not shown in the figure). LED4 (not shown in figure) glows to indicate this.
Similarly, pressing switch S1 thrice makes the Q3 output of IC1 high. Consequently, 2C/O relay RL3 (not shown in the figure) energises and the television inputs are connected to the third AV signal source. LED5 (not shown in the figure) glows to indicate this. Again, pressing switch S1 four times makes the Q4 output of IC1 high. Consequently, 2C/O relay RL4 energises and the TV inputs are connected to the fourth AV signal source (marked as Video-in 4 and Audio-in 4). LED6 glows to indicate this.
Further pressing of switch S1 resets the decade counter and LED2 glows again. Thereafter, the cycle repeats. The circuit is wired for four-input selection, therefore the Q5 output of IC1 is connected to reset pin 15 of IC1.
Enclose the assembled PCB along with the relays in a cabinet with the input/output sockets and indicators mounted on the body of the cabinet.
Author: T.K. HAREENDRAN
Wireless Stepper Motor Controllers Circuit Diagram
Here is a low-cost and simple wireless stepper motor controller using infrared signals. Using this circuit you can control the stepper motor from a distance of up to four meters.
The circuit comprises transmitter and receiver sections. The communication between the transmitter and receiver sections is achieved through infrared signals.
The circuit comprises transmitter and receiver sections. The communication between the transmitter and receiver sections is achieved through infrared signals.
Wireless Stepper Motor Controllers Circuit Diagram
In the transmitter section, timer NE555 ICs (IC1 and IC2) are configured as astable multivibrators with frequencies of around 1 Hz and 38 kHz, respectively. The output of IC1 is given to reset pin 4 of IC2, so the 38kHz carrier signal is modulated by 1Hz modulating signal. The modulated signal from pin 3 of IC2 is transmitted by the infrared LED. Resistor R5 limits the current through the IR LED.
The transmitted signal is sensed by IR receiver module TSOP1738 (IC6) of the receiver section and its output at pin 3 is used as clocks for dual flip-flop 74LS74 Ics (IC3 and IC4), which are configured as a ring counter.
Fig. 2: Infrared receiver and stepper motor driver circuit
The outputs of flip-flops are amplified by the Darlington transistor array inside ULN2003 (IC5) and connected to the stepper motor windings marked ‘A’ through ‘D.’ The common point of the windings is connected to +12V DC supply.
To stop the motor, the flip-flops can be reset manually by pressing reset switch S1. On releasing the reset switch, the stepper motor again starts moving. If any interruption occurs between the transmitter and the receiver, the motor stops
Sourced By EFY Author Jaydip Appasaheb Dhole
Mantis 9 1 CNC Mill
The Mantis 9.1 design is a radical departure from version 8 and earlier. Most notably, the part count has been almost halved! The current design has 13 parts, all of which can be made with a handsaw and a drill press. Also, I’ve traded away my alignment free exactly-constrained design for extra stiffness. Several unsuccessful attempts to eradicate the last of the slop in the Z axis on version 8 lead me back to the world of over-constrained parallel rods. My previous attempts at an over-constrained design (versions 1-5) all failed because I was unable to make the rods sufficiently parallel to avoid jamming. What to do? [Link]
Sub Woofer and Controller Circuit Diagram
Sub woofers are popular, with home theater being of the driving forces. However, a nice sub adds considerably to normal hi-fi program material, & so if it is predictable & has nice response characteristics.
all of sub woofers use a immense speaker driver in a immense box, with tuning vents & all the difficulties (& vagaries) that conventional operation entails. By conventional, I mean that the speaker & cabinet are operated as a resonant technique, using the Thistle-Small parameters to get a box which will (if everything works as it ought to) provide excellent performance.
all of sub woofers use a immense speaker driver in a immense box, with tuning vents & all the difficulties (& vagaries) that conventional operation entails. By conventional, I mean that the speaker & cabinet are operated as a resonant technique, using the Thistle-Small parameters to get a box which will (if everything works as it ought to) provide excellent performance.
Completed Prototype
A fast word is warranted here, to let you decide if the speaker you have will actually work in a little sealed enclosure. The EAS principle will permit any driver to extend to twenty Hz or even lower. A lovely fast check is to stick the speaker in a box, and drive it to 100W or so at twenty Hz - you ought to see lots of cone movement, a few things will rattle, but you should not actually listen to a tone. A "bad" speaker will generate 60 Hz (third harmonic) - in the event you dont listen to anything, the speaker will work in an equalized sub.
If a tone is audible, or the speaker shows any signs of distress (such as the cone breaking up with appropriate terrible noises), then the driver cannot be used in this manner. Either discover a different driver, or use a vented enclosure.
Before you can build your own EAS box, you will require to pick an appropriate driver, using the above as a guide. Cone tour will be high at the lowest frequencies, so the speaker needs to be able to high power, lovely tour, & of reasonable size (there is no substitute for cone area for moving air at low frequencies). I am using a 380mm (15") driver, but smaller drivers (say 300mm - 12") can be used, or even a bigger number of smaller drivers. I have also had excellent results with a single 300mm driver, which has lower sensitivity (as would expect) but is perfectly adequate for normal usage.
The check methods I used are applicable to any combination, but in general I recommend either a single giant driver or a pair of (say) 300mm units. The next hurdle is the amplifier needed to drive the speaker. This is not trivial. If the selected driver has a sensitivity of 93dB / W @ one metre, then you can safely assume that the efficiency will be less than this below resonance, by a factor of possibly 6dB or more. In case you are used to driving a sub with 100W, this means that you have increased the power to 400W - although this is an over-simplification.
If they are to operate the sub from 60Hz (my aim from the outset), they will increase the power by 12dB for each octave, so if 20W is necessary at 60Hz, then at 30Hz this has increased to 320W, & at 15Hz, you will require over 5kW.
Fortunately, the reality is a tiny different, & 400W or so will be over sufficient for a powerful process, due chiefly to the fact that the energy content in the low bass region is not normally all that great. (Although some program material may have high energy content, in general this is not the case). The EAS process augments the existing process, which is allowed to roll off naturally - contrast this with the normal case, where a crossover is used to separate the low bass from the main process, so existing speaker capability is lost.
The box I built is made from 25mm (1") MDF (Medium Density Fiberboard), & filled with fiberglass. Apart from the fact that it is very heavy (which is a lovely thing, because it desires to walk with low frequencies), the cabinet is acoustically dead, with no resonances in the low frequencies at all ( unlike my house & furniture, dammit !). The woofer is recessed in to the baffle, & sealed with weather sealing foam. When attaching the speaker, do NOT use wood screws, or any other screw in to the MDF. I used "Tee" nuts. I have no idea what they are called elsewhere in the world, but they look like this
TEE NUT
The middle is tapped, and accepts a metal thread screw, and the small spikes mean that you must drill a hole, and hammer in the Tee nut. In case you use a screw through the hole and screwed lightly in to the Tee nut, you can hold it in place as you bash away at it, and can also see that it is straight when you are done. make sure that the finish of the screw doesnt stick out the finish, or you will seldom remove it again after the hammering! I recommend that you lock the tee nut in to place with some construction adhesive (dont get any in the threaded section) so they dont fall out while you are installing the speaker.
The EAS Controller
The controller is (actually very) simple, & the circuit is shown in Figure one. An input buffer ensures that the input impedance of the source does not affect the integrator performance, & allows summing of left & right channels without any crosstalk. The output provides a phase reversal switch, so that the sub can be properly phased to the remainder of the process. If the mid-bass disappears as you advance the level control, then the phase is wrong, so switch to the opposite position.
The controller is (actually very) simple, & the circuit is shown in Figure one. An input buffer ensures that the input impedance of the source does not affect the integrator performance, & allows summing of left & right channels without any crosstalk. The output provides a phase reversal switch, so that the sub can be properly phased to the remainder of the process. If the mid-bass disappears as you advance the level control, then the phase is wrong, so switch to the opposite position.
Figure 1 - The Original EAS Filter / Controller
It turns out that the controller can be simplified, but there is no point. While the dual pot appeared like a lovely suggestion when I built my unit, it actually only changes the gain. Now, having experimented some more, this is an excellent thing, since it means that the level through the controller can be set to make positive that there is no distortion - there can be a immense amount of gain at low frequencies, & if the gain is high, distortion is assured!
The integrators (U1B & U2A) include shelving resistors (R6 & R9), & the capacitor / resistor networks (C1-R4, C3-R7) be positive that signals below 20Hz are attenuated. In case you dont require to go that low, then the worth of the caps (or the resistors R4 & R7) can be reduced. I used four.7uF caps, & these are non-polarized electrolytic - a high value was needed to keep the impedance low to the integrators. I originally included the dual pot (VR1) to permit the upper frequency roll off to be set - however it does no such thing (as described above). The final output level is set with VR2, which may be left out if your power amp has a level control.
The integrators (U1B & U2A) include shelving resistors (R6 & R9), & the capacitor / resistor networks (C1-R4, C3-R7) be positive that signals below 20Hz are attenuated. In case you dont require to go that low, then the worth of the caps (or the resistors R4 & R7) can be reduced. I used four.7uF caps, & these are non-polarized electrolytic - a high value was needed to keep the impedance low to the integrators. I originally included the dual pot (VR1) to permit the upper frequency roll off to be set - however it does no such thing (as described above). The final output level is set with VR2, which may be left out if your power amp has a level control.
It is OK to substitute different op amps, but there is tiny reason to do so. Any substitution tool ought to be a FET input op amp, or DC offset may be an issue. Do not be tempted to make use of a DC coupled amp. If the you are planning to make use of is DC coupled, the input ought to be isolated with a capacitor. Pick a value to give a -3dB frequency of about 10Hz, as this will have tiny effect on the low frequency response, but will help to attenuate the subsonic frequencies.
The unity gain range (using a 20k pot as shown) is from 53Hz to 159Hz. This ought to be sufficient for most systems, but if desired, the resistors (R5 & R8) can be increased in value to 22k, or you can select a bigger value pot. Using 22k resistors & the 20k pot will give a range from 36Hz to 72Hz.
The unity gain range (using a 20k pot as shown) is from 53Hz to 159Hz. This ought to be sufficient for most systems, but if desired, the resistors (R5 & R8) can be increased in value to 22k, or you can select a bigger value pot. Using 22k resistors & the 20k pot will give a range from 36Hz to 72Hz.
To permit lower frequencies, you can increase the 100k shelving resistors (R6 and R9) to 220k, and increase the high pass capacitors (four.7uF) with 10uF (or R4 & R7 may be increased - a maximum of four.7k is recommended). This will give a turnover frequency of around 8Hz, but expect to make use of much more power, as there will likely be significant sub-sonic energy that will generate huge cone excursions with no audible benefit.
The input must be a standard full range (or for a stampeded method, the whole low frequency signal). Do not use a crossover or other filter before the EAS controller. For final modification, and to integrate the method in to your listening room, I recommend the constant-Q equalizer. The final result using this is extraordinarily nice - I have flat in-room response to 20Hz!
The input must be a standard full range (or for a stampeded method, the whole low frequency signal). Do not use a crossover or other filter before the EAS controller. For final modification, and to integrate the method in to your listening room, I recommend the constant-Q equalizer. The final result using this is extraordinarily nice - I have flat in-room response to 20Hz!
For the power supply, use the in anything else will provide +/-15V at a few Milli amps. My supply is not even regulated, & the whole method is as close to noiseless as you will listen to (or not listen to). Construction is not critical - I built mine on a piece of Overboard (perforated prototype board), & managed to fit everything (including the power supply rectifier & filter) on a piece about 100 x 40 millimeters with room to spare.
The EAS method is surprisingly simple to set up with no instrumentation. Of coursework in case you have an SPL meter & oscillator you can also confirm the settings with measurements. Keep in mind that the room acoustics will play havoc with the results, so unless you require to drag the whole method outside, setting by ear might be the simplest. Even in case you did get it exactly right in an anechoic surroundings, this would alter one time it was in your listening room anyway.
It takes a small experimentation to get right, but is surprisingly simple to do. When properly set, a check track (or bass guitar) ought to be smooth from the highest bass note to the lowest, with no gross peaks or dips. Some are inevitable because of room resonances & the like, but you will discover a setting that sounds "right" with small difficulty.
The EAS method is surprisingly simple to set up with no instrumentation. Of coursework in case you have an SPL meter & oscillator you can also confirm the settings with measurements. Keep in mind that the room acoustics will play havoc with the results, so unless you require to drag the whole method outside, setting by ear might be the simplest. Even in case you did get it exactly right in an anechoic surroundings, this would alter one time it was in your listening room anyway.
It takes a small experimentation to get right, but is surprisingly simple to do. When properly set, a check track (or bass guitar) ought to be smooth from the highest bass note to the lowest, with no gross peaks or dips. Some are inevitable because of room resonances & the like, but you will discover a setting that sounds "right" with small difficulty.
Performance Of My Prototype
I measured 80dB SPL at one meter in my workshop (sub-woofer perched on a chair in more or less the middle of the space) with at 25Hz & 70W. This improved dramatically when the unit was installed in the listening room, but as I said earlier, there is usually not a lot recorded below around 35Hz. The longest pipe on the organ is usually about 16Hz, but larger pipes still may be used. It was found necessary to cease group of diapasons (able to 8Hz) in the famous Sydney Town Hall organ because when they were used, the very low frequency caused building destroy.
I measured 80dB SPL at one meter in my workshop (sub-woofer perched on a chair in more or less the middle of the space) with at 25Hz & 70W. This improved dramatically when the unit was installed in the listening room, but as I said earlier, there is usually not a lot recorded below around 35Hz. The longest pipe on the organ is usually about 16Hz, but larger pipes still may be used. It was found necessary to cease group of diapasons (able to 8Hz) in the famous Sydney Town Hall organ because when they were used, the very low frequency caused building destroy.
A couple of orchestral recordings revealed traffic (or perhaps underground railway) rumble that I was unaware of before (however this was before it was set correctly, and the bass was a tad louder than needed). One time set up properly, its presence is unobtrusive - except I now have about and a half octaves of additional bottom finish.
I finally decided on a 20Hz maximum frequency (-3dB), and this is reflected in the part values shown in Figure one. The actual roll-over frequency is 16.5Hz, after which the output is attenuated at about 12dB / octave (see Figure two). Without the roll off capacitors, the gain would be 20dB at 20Hz. Unity gain frequencies are about 4Hz and 63Hz with the 20k pot(s) centered.
Figure 2 - Frequency Response of EAS Controller
awesome Australian readers may recognize the woofer brand in the picture (Figure three) of my done unit. The compact size of the box can be seen from the fact that there is tiny spacing around the speaker itself, and most of what is there is the top and sides - I used 25mm MDF, so it makes the outside of the box a bit bigger than the inside. Outside dimensions are 470W x 450H x 410D (18 1/2"W x 17 1/2"H x 16"D), which gives a capacity of 60 liters (about two.1 ft³ - excluding the internal space occupied by the speaker. I think you would agree that this is a small box indeed for a 380mm loudspeaker that performs down to 15Hz.
Figure 3 - Photo of Completed EAS Cabinet
Overall, I would must say that I doubt that any conventional design would be as compact, or would have such clarity & solidarity. Being a sealed box, there is not of the "waffle" that ported designs often give, & the speaker is protected against excessive tour by the air pressure in the box itself (below the cutoff frequency, anyway).
The bottom finish in my technique is now staggering. It is rock solid, & absolutely thunders when called on. The 400W amp is over sufficient for the job, thinking about its to keep up with a biamped main technique able to high SPL (up to 120dB at my listening position). In fact a fast check indicates that 200W would have been (but . better to have it & not require it than require it & not have it).
The fact that the EAS design augments the existing speakers than taking over from them with a crossover goes a long way towards ensuring the power requirements do not get out of hand. As an added benefit, I have found that I get the same aural sensation at much lower SPLs - I can listen happily at 90dB, but it sounds much louder. I may even listen to the phone ring while listening now !
All in all, I feel it is unlikely that anything other than an isobaric enclosure could give the same performance for a box size even close to the EAS box,& even then would be limited to about 35Hz. Added to this is the unpredictable combined response of the main speakers and the sub, which is not an Problem with this design. With an EAS system, more power is necessary than a standard design, but for plenty of people, power is less costly than space.
Sourced by : Streampowers
Sourced by : Streampowers
100W Guitar Power Amplifier Circuit Diagram
The power amp board has remained unchanged since it was first published in 2002. It definitely is not broken, so there is no reason to fix it. The picture below shows a fully assembled board (obtainable as shown as M27). Using TIP35/36C transistors, the output stage is deliberately huge overkill. This ensures reliability under the most arduous stage conditions. No amplifier can be made immune from everything, but this does come close.
Guitar Power Amplifier Board
The power amp (like the earlier version) is loosely based on the 60 Watt amp historically in the past published (Project 03), but its increased gain to match the preamp. Other modifications include the short circuit protection - the tiny groups of parts next to the bias diodes (D2 and D3). This new version is not massively different from the original, but has adjustable bias, and is designed to provide a "constant current" (i.e. high impedance) output to the speakers - this is achieved using R23 and R26. Note that with this arrangement, the gain will change depending on the load impedance, with lower impedance giving lower power amp gain. This is not a controversy, so may safely be ignored.
Ought to the output be shorted, the constant current output characteristic will provide an preliminary level of protection, but is not foolproof. The short circuit protection will limit the output current to a comparatively safe level, but a sustained short will cause the output transistors to fail if the amp is driven hard. The protection is designed not to operate under normal conditions, but will limit the peak output current to about 8.5 Amps. Under these conditions, the internal fuses (or the output transistors) will probably blow if the short is not detected in time.
Figure 2 - Power Amplifier
Figure two shows the power amp PCB parts - except for R26 which doesnt mount on the board. See Figure 1B to see where this ought to be physically mounted. The bias current is adjustable, & ought to be set for about 25mA dormant current (more on this later). The recommendation for power transistors has been changed to higher power devices. This will give improved reliability under sustained heavy usage.
As shown, the power transistors will have an simple time driving any load down to four ohms. In case you dont use the PCB (or are happy to mount power transistors off the board), you can use TO3 transistors for the output stage. MJ15003/4 transistors are high power, & will run cooler because of the TO-3 casing (lower thermal resistance). Watch out for counterfeits though! Theres plenty of other high power transistors that can be used, & the amp is tolerant of substitutes (as long as their ratings are at least equal to the devices shown). The PCB can accommodate Toshiba or Motorola 150W flat-pack power transistors with relative ease - in case you desired to go that way. TIP3055/2966 or MJE3055/2955 may even be used for light or ordinary duty.
At the input finish (as shown in Figure 1B), there is provision for an auxiliary output, & an input. The latter is switched by the jack, so you can use the "Out" & "In" connections for an outside effects unit. Alternatively, the input jack can be used to connect an outside preamp to the power amp, disconnecting the preamp.
The speaker connections permit up to 8 Ohm speaker cabinets (giving four Ohms). Do not use less than four ohm lots on this amplifier - it is not designed for it, & wont give reliable service!
The speaker connections permit up to 8 Ohm speaker cabinets (giving four Ohms). Do not use less than four ohm lots on this amplifier - it is not designed for it, & wont give reliable service!
All the low value (i.e. 0.1 & 0.22 ohm) resistors must be rated at 5W. The 0.22 ohm resistors will get warm, so mount them away from other parts. Needless to say, I recommend using the PCB, as this has been designed for optimum performance, and the amp gives an excellent account of itself. So nice in fact, that it may even be used as a hi-fi amp, and it sounds excellent. In case you were to make use of the amp for hi-fi, the bias current ought to be increased to 50mA. Ideally, you would use better (faster / more linear) output transistors as well, but even with those specified the amp performs well indeed. This is largely because they are run at comparatively low power, and the extreme non-linearity effects would expect with only transistors do not occur because of the parallel output stage.
Make positive that the bias transistor is attached to of the drivers (the PCB is laid out to make this simple to do). A some quantity of heat sink compound as well as a cable tie will do the job well. The diodes are there to protect the amp from catastrophic failure ought to the bias servo be incorrectly wired (or set for maximum current). All diodes ought to be 1N4001 (or 1N400? - anything in the 1N400x range is fine). A heat sink is not needed for any of the driver transistors.
The life of a guitar amp is a hard, and I recommend that you use the largest heat sink you can afford, since it is common to have elevated temperatures on stage (chiefly due to all the lighting), and this reduces the safety margin that normally applies for domestic equipment. The heat sink ought to be rated at 0.5° C/Watt to permit for worst case long term operation at up to 40°C (this is not unusual on stage).
Make sure that the speaker connectors are isolated from the chassis, to keep the integrity of the earth isolation parts in the power supply, & to make sure that the high impedance output is maintained.
Make sure that the speaker connectors are isolated from the chassis, to keep the integrity of the earth isolation parts in the power supply, & to make sure that the high impedance output is maintained.
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