Sunday, 24 June 2012
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Solar Lamp Using PR4403
The PR4403 is an enhanced cousin of the PR4402 40mA LED driver. It has an extra input called LS which can be taken low to turn the LED on. This makes it very easy to build an automatic LED lamp using a rechargeable battery and a solar module. The LS input is connected directly to the solar cell, which allows the module to be used as a light sensor at the same time as it charges the battery via a diode. When darkness falls so does the voltage across the solar module: when it is below a threshold value the PR4403 switches on. During the day the battery is charged and, with the LED of, the driver only draws 100µA.
Circuit diagram:
At night the energy stored in the battery is released into the LED. In contrast to similar designs, here we can make do with a single 1.2 V cell. The PR4403 is available in an SO-8 package with a lead pitch of 1.27 mm. The other components are a 1N4148 diode (or a Schottky 1N5819) and a 4.7µH choke. Pin 2 is the LS enable input, connected directly to the solar module. According to the datasheet, it is possible to connect a series resistor at this point (typ. 1.2 M) to increase the effective threshold voltage. The LED will then turn on slightly earlier in the evening before it is not completely dark. Pins 3 and 6 of the device must be connected together and together form the output of the circuit.
Burkhard Kainka
Elektor Electronics 2008
Copyright: http://www.extremecircuits.net
6-Channel Running Light
The circuit of the running light comprises two integrated circuits (ICs), a resistor, a capacitor and seven light-emitting diodes (LEDs), Decade scaler IC2 ensures that the LEDs light sequentially. The rate at which this happens is determined by the clock at pin 14. The clock is generated by IC1, which is arranged as an astable multivibrator. Its frequency is determined by R1-C1. The touch switch, consisting of two small metal disks is optional. When switch S1 is in position ‘off’, the circuit may be actuated by the touch switch. By the way, this enables the circuit to be used as an electronic die (in which case the LEDs have to be numbered from 1 to 6). The running light is powered by a 9 V battery or mains adapter. It draws a current not exceeding 20 mA.
Circuit diagram:
Author: L. v/d Heeden
Copyright: Elektor Electronics 1998
Mains Powered White LED Lamp
Did it ever occur to you that an array of white LEDs can be used as a small lamp for the living room? If not, read on. LED lamps are available ready-made, look exactly the same as standard halogen lamps and can be fitted in a standard 230-V light fitting. We opened one, and as expected, a capacitor has been used to drop the voltage from 230 V to the voltage suitable for the LEDs. This method is cheaper and smaller compared to using a transformer. The lamp uses only 1 watt and therefore also gives off less light than, say, a 20 W halogen lamp. The light is also somewhat bluer. The circuit operates in the following manner: C1 behaves as a voltage dropping ‘resistor’ and ensures that the current is not too high (about 12 mA).
The bridge rectifier turns the AC voltage into a DC voltage. LEDs can only operate from a DC voltage. They will even fail when the negative voltage is greater then 5 V. The electrolytic capacitor has a double function: it ensures that there is sufficient voltage to light the LEDs when the mains voltage is less than the forward voltage of the LEDs and it takes care of the inrush current peak that occurs when the mains is switched on. This current pulse could otherwise damage the LEDs. Then there is the 560-ohm resistor, it ensures that the current through the LED is more constant and therefore the light output is more uniform.
There is a voltage drop of 6.7 V across the 560-Ω resistor, that is, 12 mA flows through the LEDs. This is a safe value. The total voltage drop across the LEDs is therefore 15 LEDs times 3 V or about 45 V. The voltage across the electrolytic capacitor is a little more than 52V. To understand how C1 functions, we can calculate the impedance (that is, resistance to AC voltage) as follows: 1/(2π·f·C), or: 1/ (2·3.14·50·220·10-9)= 14k4. When we multiply this with 12 mA, we get a voltage drop across the capacitor of 173 V. This works quite well, since the 173-V capacitor voltage plus the 52-V LED voltage equals 225 V. Close enough to the mains voltage, which is officially 230 V.
Circuit diagram:
Moreover, the latter calculation is not very accurate because the mains voltage is in practice not quite sinusoidal. Furthermore, the mains voltage from which 50-V DC has been removed is far from sinusoidal. Finally, if you need lots of white LEDs then it is worth considering buying one of these lamps and smashing the bulb with a hammer (with a cloth or bag around the bulb to prevent flying glass!) and salvaging the LEDs from it. This can be much cheaper than buying individual LEDs…
Copyright: http://www.extremecircuits.net
White LED Lamp
Nowadays you can buy white LEDs, which emit quite a bit of light. They are so bright that you shouldn’t look directly at them. They are still expensive, but that is bound to change. You can make a very good solid-state pocket torch using a few of these white LEDs. The simplest approach is naturally to use a separate series resistor for each LED, which has an operating voltage of around 3.5 V at 20 mA. Depending on the value of the supply voltage, quite a bit of power will be lost in the resistors. The converter shown here generates a voltage that is high enough to allow ten LEDs to be connected in series. In addition, this converter supplies a constant current instead of a constant voltage.
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A resistor in series with the LEDs produces a voltage drop that depends on the current through the LEDs. This voltage is compared inside the IC to a 1.25-V reference value, and the current is held constant at 18.4 mA (1.25 V ÷ 68 Ω). The IC used here is one of a series of National Semiconductor ‘simple switchers’. The value of the inductor is not critical; it can vary by plus or minus 50 percent. The black Newport coil, 220 µH at 3.5 A (1422435), is a good choice. Almost any type of Schottky diode can also be used, as long as it can handle at least 1A at 50V. The zener diodes are not actually necessary, but they are added to protect the IC. If the LED chain is opened during experiments, the voltage can rise to a value that the IC will not appreciate.
Resistors:
R1 = 1kΩ2
R2 = 68Ω
Capacitors:
C1 = 100µF 16V radial
C2 = 680nF
C3 = 100µF 63V radial
Inductors:
L1 = 200µH 1A
Semiconductors:
D1 = Schottky diode type PBYR745 or equivalent
D2-D5 = zener diode 10V, 0.4W
D6-D15 = white LED
IC1 = LM2585T-ADJ (National Semiconductor)
Copyright: http://www.extremecircuits.net
High-Intensity, Energy-Efficient LED Light
Here is a rechargeable LED lamp that gives you bright light for a long duration of time as it consumes little power. The circuit presented here is compact, automatic, reliable, low-cost and easy to assemble. The circuit comprises power supply, battery charging and switching sections. The power supply section takes power from 230V AC mains supply without using a transformer. Capacitor C1 is used as an AC voltage dropper a well-known transformer-less solution. This helps to make the circuit compact without generating heat, as capacitor C1 dissipates negligible power. Capacitor C1 also protects against fluctuations in mains.
Current required for the battery charging circuit is provided by capacitor C1. Capacitor C1 discharges through resistor R1 when the circuit is disconnected from the mains voltage. This helps to prevent a fatal shock due to any voltage remaining in the input terminals. Capacitor C1 must be rated at least 440V AC, with mains application class X2. The AC mains voltage after capacitor C1 is given to bridge rectifier diodes D1 through D4 to convert alternating current into direct current and filtered by capacitor C2. The voltage from point B+ is given to positive terminal of the battery (BATT), anodes of LEDs (LED2 through LED21) and transistor base-bias resistor R3 through slide switch S1.
The circuit is operated in three modes (AC/charge, off and batt) by using three-position switch S1. When switch S1 is in middle position, the circuit is off. When S1 is towards right, white LEDs glow by drawing power from 4V battery. When S1 is towards left, the circuit connects to AC mains and battery starts charging. The presence of AC mains voltage and battery charging is indicated by LED1. White LEDs remain off if AC mains supply is available and glow in the absence of AC mains. When switch S1 is towards left position and AC mains is available, the battery charges through diode D6 and the white LEDs don’t glow. The negative DC path through diode D5 makes the transistor cut-off, preventing the battery current from LEDs to the negative terminal through the transistor.
Thus the white LEDs don’t glow. On the other hand, if AC mains is not available, charging stops and the base of transistor SS8050 gets positive voltage from the battery through slide switch S1 and resistor R3. The transistor conducts and the current flows from the battery’s positive terminal to the negative terminal of the battery through the LEDs (LED2 through LED21), collector to emitter of transistor T1 and switch S1. Thus the white LEDs glow. When the switch is in ‘batt’ position, the white LEDs (LED2 through LED21) get the supply directly from 4V battery through switch S1 and therefore all the white LEDs glow. Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Fix the mains power cord on the back of the cabinet and slide switch and LEDs on the front side.
Source:EFY Mag
Copyright: http://www.extremecircuits.net
9 Volt 2 Ampere DC Power Supply Circuit Diagram
There is little to be said about this circuit. All the work is done by the regulator. The 7809 can deliver up to 2 amps continuous output whilst maintaining a low noise and very well regulated supply. The circuit will work without the extra components, but for reverse polarity protection a 1N5400 diode (D1) is provided at the input, extra smoothing being provided by C1. The output stage includes C2 for extra filtering, if powering a logic circuit than a 100nF (C3) capacitor is also desirable to remove any high frequency switching noise.
Circuit diagram:
Parts:
C1 = 100uF-25V electrolytic capacitor, at least 25V voltage rating
C2 = 10uF-25V electrolytic capacitor, at least 6-16V voltage rating
C3 = 100nF-63V ceramic or polyester capacitor
IC = 7809 Positive Voltage Regulator IC
D1 = 1N5400 Diode
Copyright: http://www.extremecircuits.net
12V Regulated Inverter Supply
When running 12V electronic devices from lead-acid battery banks, the voltage to the appliance can vary from below 11V with discharged batteries, to well above 14V during charging. Many appliances will not tolerate such a wide fluctuation and may perform poorly or be damaged.
This step-up inverter, combined with a 12V fixed regulator, is a good solution. Q1 & Q2, together with the ferrite pot-core transformer, comprise a DC-to-AC inverter. The turns ratio steps down the input voltage by about 30%. The square wave output voltage is rectified and added to the input DC voltage. The stepped up DC is then fed to a 7812 12V regulator (REG1).
Circuit diagram:
The specified regulator will supply 1.5A at 12V out, from any input into the inverter between 9V and 15V, with the inverter making up the shortfall. Current requirements are kept to a minimum by not having the inverter supplying the total current.
By substituting a higher rated linear regulator, up to 5A can easily be supplied by this simple circuit. The transistors can be almost any general-purpose power type while the twin diode (D4/D5) is a high-speed device commonly found in defunct computer power supplies. Normal rectifier diodes can be used with a slight decrease in efficiency. The same comment applies to D2/D3. D6 is a protection diode and any 3A type will be suitable.
By slightly modifying the turns ratio, and substituting the linear regulator, 24V devices can be operated from a 12V supply. Laptops requiring around 18V can be powered as well.
This diagram shows how to wind the transformer. L1 & L2 are six turns bifilar wound using 1mm-diameter enameled copper wire, while L3 & L4 are four turns bifilar wound.
Source: Silicon Chip 01 May 2009
Copyright: http://www.extremecircuits.net
Low-Cost Dual Power Supply
This circuit shows how to symmetrically split a supply voltage using a minimum of parts - one LM380 power amplifier plus two 10µF capacitors. It was originally published in National Semiconductor's AN69 and provides more output power than a conventional general-purpose op amp split power supply. Unlike the normal power zener diode technique, the LM380 circuit does not require a high standby current to maintain regulation. In addition, with a 20V input voltage (ie, for ± 10V outputs), the circuit exhibits a change in output voltage of only about 2% per 100mA of unbalanced load change. Any balanced load change will reflect only the regulation of the source voltage, Vin.
Circuit diagram:
The theoretical plus and minus output tracking ability is 100% since the device will provide an output voltage at one-half of the instantaneous supply voltage in the absence of a capacitor on the bypass terminal. The actual error in tracking will be directly proportional to the unbalance in the quiescent output voltage. An optional 1MO potentiometer may be installed with its wiper connected to pin 1 of the LM380 IC to null any output offset. The unbalanced current output is limited by the power dissipation of the package.
In the case of sustained unbalanced excess loads, the device will go into thermal limiting as the internal temperature sensing circuit begins to function. And for instantaneous high current loads or short circuits, the device limits the output current to approximately 1.3A until thermal shutdown takes over or the fault is removed. For maximum output power (2.5W), all ground pins (3-5 & 10-12) should be soldered to a large copper area (the LM380 data sheet contains more details).
Copyright: http://www.extremecircuits.net
Overvoltage Protection
When a sensitive circuit must under no circumstances have too high a supply voltage applied, then some means of disconnecting the supply must be provided. One way to achieve this is to trigger a thyristor to blow a fuse. A less destructive alternative possibility is to use a MOSFET to disconnect the supply. An over-voltage protection IC, the LTC1696 from Linear Technology (www.linear-tech.com), has recently become available, which is suitable for triggering and driving such a device. It operates from a power supply in the range 2.7 V to 27 V and can be connected to the unregulated input of a voltage regulator. Two voltages can be monitored using feedback pins FB1 and FB2, suitably divided down using potential dividers.
The trigger threshold for both FB1 and FB2 is +0.88 V. The value of the upper resistor in the potential divider can be calculated using the following formula: R1 = 33 kΩ× [(VLIMIT – 0.88 V)/0.88 V] The value of the capacitor connected to the TIMER/RESET pin sets the delay before the protection is triggered. The charging current for this capacitor depends non-linearly on the amount by which the voltage exceeds the threshold value. The greater the over-voltage, the faster the IC triggers. Once triggered the IC remains in that state until either the input voltage is removed or the internal latch is cleared using the MOSFET connected to the TIMER/RESET input.
Copyright: http://www.extremecircuits.net
Contactless AC Mains Voltage Detector
This is a CMOS IC (CD4033) based circuit which can be used to detect presence of AC mains voltage without any electrical contact with the conductor carrying AC current/voltage. Thus it can be used to detect mains AC voltage without removing the insulation from the conductor. Just take it in the vicinity of the conductor and it would detect presence of AC voltage. If AC voltage is not present, the display would randomly show any digit (0 through 9) permanently. If mains supply is available in the conductor, the electric field would be induced into the sensing probe. Since IC used is CMOS type, its input impedance is extremely high and thus the induced voltage is sufficient to clock the counter IC. Thus display count advances rapidly from 0 to 9 and then repeats itself. This is the indication for presence of mains supply. Display stops advancing when the unit is taken away from the mains carrying conductor. For compactness, a 9-volt PP3 battery may be used for supply to the gadget.
Copyright: http://www.extremecircuits.net
36 Watt Audio Power Amplifier Using TDA1562Q
It's based on a Philips class-H audio amplifier IC and can deliver 36W RMS OR 70W music power, all from a 13.8V supply. Our new Mighty Midget Amplifier can really pack a punch - around 36W RMS continuous into a 4-ohm load when using a 13.8V supply. However, it's the 70W of output power that it can deliver during dynamic (music) signal conditions that really make you sit up and take notice.
As can be seen from the photos and the circuit diagram, the Mighty Midget uses just a handful of parts. It's built on a PC board that measures just 104mm x 39mm but while its size may be modest, these's nothing at all modest about its power output. And the noise and distortion figures are pretty good too.
Circuit diagram:
At the heart of the circuit is the TDA1562Q IC, described by Philips as a "monolithic integrated Bridge-Tied Load (BTL) class-H high-efficiency power amplifier". It comes in a 17-pin "DIL-bent-SIL" plastic package and is not only designed for use in car audio and portable PA work but for mains applications as well; eg, mini/midi audio components and TV sound.
Parts layout:
PCB layout:
Performance:
Output power:----------------------36W RMS into 4R
Music power:-----------------------70W into 4R
Frequency response:---------------1dB down at 28Hz and 55kHz
Input sensitivity:-------------------130mV RMS (for 36W into 4?)
Harmonic distortion:----------------typically 0.2% (see graphs)
Signal-to-noise ratio:----------------95dB unweighted (22Hz to 22kHz)
Source: Silicon Chip March 2002
Copyright: http://www.extremecircuits.net
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