Voltase hobby

Friday, October 31, 2014

The monophonic 270 watt Double barreled Amplifier

This amplifier is the monophonic 270 watt Double barreled Amplifier. For the original article, I specified plus and minus 85 V dc power supply voltages. The voltage can be increased to about 93 V to obtain a power rating of 300 W. The amplifier can be built either as a stereophonic or a monoponic unit. My original amps were mono units because the heat sinks, transformer, and filter caps that I used were too large for a stereo amp.

The circuit described on this page is a modification of the original Double Barreled Amplifier. The circuit has been simplified somewhat. The circuit board layout is smaller and much more compact. The driver transistors now mount on the circuit board instead of on external heat sinks. And the circuit has the feedforward compensation that I describe for the Low TIM Amplifier.

If you build this amplifier, you must keep the wiring between the heat sinks and the circuit boards as short as possible if you dont want oscillation problems.

When you test the circuit boards before connecting the power transistors, temporarily connect a 10 ohm resistor in series with a 0.1 ufd capacitor from the loudspeaker output to the power supply ground.

The Circuit Boards

I do not have circuit boards for the Double Barrelled Amplifier. If you wish to build it, you must make your own. Two drawings show the parts layout on the board, one with circuit traces and one without. These are scaled by a factor of 1.5. The other shows the circuit traces only. All layout views are from the component side of the board. You must flip the layout for the foil traces over to obtain the solder side view. The circuit board measures 4 inches by 6 inches. To my knowledge, there are no errors in the layout. If you decide to use it, you should carefully check it for errors because I could have easily made a mistake.

I do not recommend that you make the circuit boards unless you have experience in doing it. A source of materials for making your own printed circuits can be found here. I have been told that their "Press and Peel Blue" product (not the wet stuff they sell) can be used to successfully make boards with traces as narrow as 0.01 inch. The smallest traces on the amplifier layout are 0.03 inch wide. The PnP Blue product is basically a transfer medium that allows you to transfer the toner image from a laser printer directly onto bare copper clad board and then etch it in FeCl3 (ferric chloride).

After you etch the board, the copper should be cleaned with steel wool, lightly coated with solder flux, and then "tinned" with a soldering iron and rosin core solder. Do not use a commercial tinning solution that you dip the board into. It is almost impossible to solder a board that is tinned with one of these products because they corrode very quickly. When you drill the board, you should use the correct size drill bit for the pads. The hole diameters I recommend are: small pads - 0.032 inch, medium pads - 0.040 inch, large pads - 0.059 inch, mounting holes - 0.125 inch. If you do not use a sharp drill bit, you can pull the pads off the board when you drill it.

Circuit Description

If you compare the Double Barreled circuit to the Low TIM circuit, you will see a lot of similarity between the two. Indeed, there is a Low TIM Amplifier embedded in the Double Barreled Amplifier. The major difference between the two is that transistors are added in series with those in the Low TIM circuit to form the Double Barreled circuit. By doing this, the voltage across the transistors is decreased so that the power supply voltage can be increased for higher output power.

Basically, the circuit description for the Low TIM Amplifier also applies to the Double Barreled Amplifier. The major difference between the two is the addition of transistors Q22 through Q31. Q22 is connected as a common base stage at the output of Q12. The two transistors form a cascode stage. The base of Q22 connects to the junction of R52 and R54. These two resistors are equal and are connected as a voltage divider between the loudspeaker output and the positive rail. This forces the base voltage of Q22 to float half way between the loudspeaker output voltage and the positive power supply rail. Similarly, Q13 and Q23 form a cascode stage. R53 and R55 force the base of Q23 to float half way between the loudspeaker output voltage and the negative power supply rail. The addition of Q22 and Q23 cause the collector to emitter voltages of Q12 and Q13 to be approximately one-half of what the voltages would be without Q22 and Q23.

Transistors Q24 and Q25 connect in series with the pre-driver transistors Q14 and Q15. The base of Q24 floats half way between the output voltage and the positive rail. The base of Q25 floats half way between the output voltage and the negative rail. The addition of Q24 and Q25 cause the voltages across Q14 and Q15 to be approximately one-half of what they would be without Q24 and Q25. Similarly, transistors Q26 through Q31 cause the voltages across Q16 through Q21 to be approximately one-half of what they would be without Q26 through Q31. By connecting the transistors in series in this way, the rail voltages can be increased for higher output power.

The basic construction details of the Low TIM Amplifier also apply to the Double Barreled Amplifier. There are two short circuit jumper wires that must be soldered on the circuit board. These are marked with a J on the layout. In addition, you must solder a short circuit jumper in place of C6B if you use a non-polar capacitor for C6A. This is explained in the parts list for the Low TIM Amplifier. Because there are eight output transistors, two main heat sinks per channel are required. Q18, Q20, Q28, and Q30 should be mounted on one and Q19, Q21, Q29, and Q31 on the other. Resistors R61 through R64 and wires connecting the collectors of Q18 and Q20 and the collectors of Q19 and Q21 mount on the heat sinks. These connect between lugs on the transistor sockets. The four bias diodes D1 through D4 can be mounted on either heat sink. It is not necessary to divide the diodes between the two heat sinks because both heat sinks will operate at the same temperature. I recommend setting the voltage across Q7, i.e. the voltage between the collectors of Q22 and Q23, so that that amplifier is biased at 120 mA. This will give the same quiescent power dissipation per heat sink as in the Low TIM Amplifier.

Testing the Circuit Boards

After you solder the parts to the circuit board, it is tested using the same procedure specified for the Low TIM circuit board. First, you must solder the short circuit jumper across Q7 and you must solder the 100 ohm 1/4 W resistors from the loudspeaker output to the emitters of Q16 and Q17. If you dont have a bench power supply that puts out plus and minus 85 to 93 V dc, you can test the circuit board at a lower voltage. I would prefer test voltages of at least plus and minus 50 V dc. An option is to connect bench power supplies in series to obtain the plus and minus 85 to 93 V dc. I have routinely connected two 40 V Hewlett Packard power supplies in series with the positive and negative outputs of a Hewlett Packard 50 V dual power supply, and I have never had any problems. To protect the circuit boards, you might want to put a 100 ohm 1/4 W resistor in series with the plus and minus power supply leads for the tests. The current drawn by the circuit should be low enough so that the voltage drop across these resistors is less than 1 V if nothing is wrong on the circuit board. There are 2 ground wires from the circuit board. Both must be connected when testing the boards.

I cant stress how important it is to be careful in testing a circuit board. Even simple errors can cause the loss of many expensive transistors. I always use current limited bench power supplies to test a circuit board before and after connecting the power transistors. I also bias an amplifier using current limited power supplies in place of the amplifier power supply. When I initially power up an amplifier with its own power supply, I always use a Variac variable transformer to slowly increase the ac input voltage from 0 to 120 V rms while observing the amplifier output on an oscilloscope with a sine wave input signal. If I see anything wrong on the oscilloscope, I turn the Variac to zero and try to diagnose the problem using the bench power supply. I never use a load on the amplifier for these tests.

Parts List

With the following exceptions, the parts for the Double Barreled Amplifier are the same as for the Low TIM Amplifier.
Capacitors

C10, C11 - 15 pF mica
C13, C14 - 100 uFd 100 V radial electrolytic
C21, C22 - 47 uFd 100 V radial electrolytic
C26, C27 - 270 pF mica
C28 - 0.01 uFd 250 V film

Transistors

Q1, Q2, Q5, Q7, Q9, Q10 - MPS8099 or MPSA06
Q3, Q4, Q6, Q8, Q11 - MPS8599 or MPSA56
Q23, Q24 - 2N3439
Q22, Q25 - 2N5415
Q26 - MJE15030
Q27 - MJE15031
Q28, Q30 - MJ15003
Q29, Q31 - MJ15004

Diodes

D5, D6 - 1N4934 fast recovery rectifier
D13 through D16 - 1N5250B 20 volt zener diode

Resistors

R13, R14 - 5.6 kohm 1 watt (This value is for 85 V power supplies. For other power supply voltages, the formula is on the Parts List page for the Leach Amp.)
R28, R29 - 200 ohm 1/4 watt
R30, R31 - 3.9 kohm 1 watt
R37 through R40 - 470 ohm 1/4 watt
R41 through R44 - 10 ohm 1/2 watt (changed 6/27/00)
R52 through R55 - 6.2 kohm 1 watt
R56 through R59 - 10 ohm 1/2 watt (changed 6/27/00)
R60 - 39 ohm 1/4 watt
R61 through R64 - 0.33 ohm 5 watt. These 4 resistors are mounted on the heat sinks between solder lugs on the power transistor sockets. The wires that connect the collectors of Q18 and Q20 and the collectors of Q19 and Q21 are also soldered between the lugs on the sockets. Keep all leads as short as possible and use insulation stripped from hookup wire around the bare leads of the resistors.
R65, R66 - 300 ohm 1/4 watt

Dual 3v White LED Flasher and Dual 1v5 White LED Flasher

This circuit alternately flashes 2 white LEDs, on a 3v supply and produces a really bright flash. The circuit produces a voltage above 5v if the LED isnt in circuit however the LED limits the voltage to its characteristic
voltage of three.2v to 3.6v. The circuit takes concerning 2mA and is actually a voltage-doubler (voltage incrementer) arrangement.

The 1k charges the 100u and therefore the diode drops zero.6v to prevent the LED from setting out to illuminate on 3v. When a transistor conducts, the collector pulls the 100u down towards the 0v rail and therefore the negative of the electro is actually concerning 2v below the 0v rail. The LED sees 3v + 2v and illuminates terribly brightly when the voltage reaches about 3.4v. All the energy within the electro is pumped into the LED to supply a really bright flash.

DUAL 1v5 WHITE LED FLASHER
This circuit alternately flashes 2 white LEDs, on a 1.5v supply and produces a really bright flash. The circuit
produces a voltage of concerning 25v when the LEDs dont seem to be connected, however the LEDs scale back this as they need a characteristic voltage-drop across them after they are illuminated. dont use a offer voltage above one.5v.

The circuit takes concerning 10mA. The transformer consists of thirty turns of terribly fine wire on a 1.6mm slug 6mm long, however any ferrite bead or slug will be used. the amount of turns isnt crucial. The 1n is very important and using the other worth or connecting it to the positive line can increase the provision current.

Using LEDs apart from white can alter the flash-rate considerably and each LEDs should be identical color.

Thursday, October 30, 2014

Outdoor LED Solar Lights Circuit Schematic

This Outdoor LED Solar Garden Lights project is a hobby circuit of an automatic garden light using a LDR and 6V/5W solar panel. During day time, the internal rechargeable 6 Volt SLA battery receives charging current from the connected solar panel through polarity protection diode D9 and current limiting resistor R10. If ambient light is normal, transistor T1 is reverse biased by IC1 (LM555). Here IC1 is wired as a medium current inverting line driver, switched by an encapsulated light detector (10mm LDR). Multi-turn trimpot P1 sets the detection sensitivity. When ambient light dims, transistor T1 turns on to drive the white LED string (D1-D8). Now this lamp load at the output of T1 energizes. Resistors R1-R8 limits the operating current of the LEDs. When the ambient light level restores, circuit returns to its idle state and light(s) switched off by the circuit.

Outdoor LED Solar Lights Circuit Schematic

Outdoor Garden Solar Lights Circuit Diagram

Assemble the Outdoor Solar Lights circuit on a general purpose PCB and enclose the whole assembly in a transparent plastic box. Drill suitable holes on the top of the enclosure to mount the mini solar panel (SP1) and the light sensor (LDR), and in front for fitting power switch (S1) and the sensitivity controller (P1). Fix the battery inside the cabinet using a double-sided glue tape/pad. Finally, the LDR should not be mounted to receive direct sunlight. It must be mounted at the top of the enclosure, pointing to the sky say southwards. This circuit is very simple. So interested and experienced hobbyists can alter/modify the whole circuit as per their own ideas without any difficulty (Just try a 6V relay with T1 to drive more number of LED strings).

Thermopile Sensors LMP91050

Thermopile Sensors seeing that typically used trendy NDIR applications

The LMP91050 is a programmable integrated Sensor Analog Front side (AFE) optimized on behalf of thermopile sensors, as typically used in NDIR applications. It provides a complete sign path solution amid a sensor and microcontroller to generates an output voltage proportional to the thermopile voltage. The LMP91050s programmability enables it to support multiple thermopile sensors with a single design because different to the multiple discrete solutions.

Programmable gain amplifier
“Dark indication” offset cancellation
ropes outdoor filtering
collective mode generator and 8 morsel DAC
Ideal pro NDIR Sensing, Demand control ventilation, Automotive CO2 hut control, Alcohol detection

datasheet download : LMP91050

source

Wednesday, October 29, 2014

Low Voltage Cut Out Circuit Diagram

This circuit will detect when the voltage of a 12v battery reaches a low level. This is to prevent deep-discharge or maybe to prevent a vehicle battery becoming discharged to a point where it will not start a vehicle. This circuit is different to anything previously presented. It has HYSTERESIS. Hysteresis is a feature where the upper and lower detection-points are separated by a gap.

Circuit diagram :

Low Voltage Cut-Out Circuit Diagram

Normally, the circuit will deactivate the relay when the voltage is 10v and when the load is removed. The battery voltage will rise slightly by as little as 50mV and turn the circuit ON again. This is called "Hunting." The off/on timing has been reduced by adding the 100u. But to prevent this totally from occurring, a 10R to 47R is placed in the emitter lead. The circuit will turn off at 10v but will not turn back on until 10.6v when a 33R is in the emitter. The value of this resistor and the turn-on and turn-off voltages will also depend on the resistance of the relay.

Author : Colin Michel - Copyright : 200 Transistor Circuits

600 Watt Quasi Amplifier With Mosfet IRFP460

ACTK 400/600 Watt
Two versions of a robust module capable of delivering high powwer for extended periods. The Actrk400 uses 6 n-channel Mosfets in the output stage to deliver around 400 watts into 4 ohms while the Actrk600 uses 12 n-channel Mosfets in the output stage to deliver power in excess of 600 watts into 4 ohms. One constructor has achieved almost 900 watts with the Actrk600 layout using 12 IRFP460 Mosfets.

Actrk 600W schematic

ACTK 400W Layout

ACTK 600W Layout

ACTK Power Supply
Schmatic

Layout power supply

Final Set up And Adjustment
No attempt should be made to set up or test a power amplifier module that is not correctly mounted on
a heatsink. Make sure the main power supply is fused and the work area is clear. First check all your
work and make sure the output devices are insulated from heatsink. The set up is done without an
input or a load connected to the power amplifier.
1. Check the power supply is operating correctly and verify the rail voltages. Switch the power
supply off and check with a multimeter that the rail capacitors have discharged.
2. Using a multimeter measure the resistance of VR2 and set it for maximum resistance.
3. Correctly connect the ground lead, the two positive leads plus the negative lead to the power
amp module.
4. Remove the PCB fuses and replace with 100 ohm 5 watt resistors. Connect a multimeter that
is set to the 20 volt scale across the positive rail 100 ohm resistor.
5. Check that the power supply connections are correct one last time and switch on. If the
multimeter reading goes off-scale, turn off immediately and find the problem. Check also the
100 ohm 5 watt resistors; they may have gone open cct.
6. If everything seems ok adjust VR2 to set the output stage bias current, by measuring the
voltage across the positive rail resistor. Adjust for a reading of 4 volts per output FET pair. I.e.
For a 6 FET board set for a voltage of 12 volts. This equates to a bias current of 40mA per FET
pair or 120 mA total. For the 12 FET board set for a voltage of 24 volts.
7. If everything seems ok, check the output offset voltage and adjust VR1 to achieve an offset of
less than 10 mV. You will need to wait briefly between adjustments for the offset to settle.
8. All being well switch off, back off the bias control trimmer (VR2) and replace the 100 ohm
resistors with 10 ohm 1 watt resistors. Switch on again and re-adjust VR2 to get 0.4 volts per
FET pair.
9. Switch off, remove the resistors and put the fuses back in. Switch on, re-check the offset
voltage and adjust with VR1 if necessary.
The amp module is ready, connect the input and output and enjoy.

Tuesday, October 28, 2014

250mW 16 dB VHF amplifier Circuit diagram

A high efficiency simple 2-transistor VHF amplifier electronic circuit project can be designed using this electronic circuit diagram . This VHF amplifier electronic circuit has a very high efficiency of about 16dB gain, and requires no tuning or alignment procedures. Wideband techniques have been used in the design and the circuit is equipped with a "lowpass" filter to ensure good output spectral purity. This VHF power amplifier circuit is specifically designed to amplify the output of 7mW to 10mW WBFM transmitters to a final level of 250mW to 300mW, after the filter.
The output of this stage is around 70mW of RF power.
The transistor is biased by means of R5, R6 and L6, and the residual DC current is set by R4. The input signal is coupled by C9 to the Base of the transistor.
The input signal from Q1 is coupled to the Base of Q2 via C7.The 78L08 voltage regulator is used to regulate the supply voltage to Q1 and the bias votages to both Q1 and Q2 so that the output RF power is relatively constant, even with large variations of supply voltage.
The output of the amplifier is filtered with a low-pass filter to reduce the output spurious and harmonic content.
The output filter consists of C3, C4, L1 and L2.
This RF power amplifier must be powered from a simple 12 volts DC power supply circuit.