Showing posts with label electronics circuit. Show all posts
LED Voltmeter for car battery by LM324
The circuit, is a comparator, can measure with step of 1Volt, the voltage of battery of car. The clue of voltage become after comparison of voltage of battery, that is applied in the inverting inputs of amplifiers, with voltages of reference that are produced by a Zener D1,the value of which is such so that it present good thermic stability. With the RV1, we regulate the gradation of voltage that we want.
The optical clue become from four Led.
R1=1K2 R6=10K D2-3-4-5=LED
R2-3-4=680R R7-8-9-10=1K IC1=LM324
R5=15K D1=5V6 /0.5W Zener RV1=10K trimmer
ic TDA2050 based 32W HI-FI AUDIO POWER AMPLIFIER full
The TDA 2050 is a monolithic integrated circuit in Pentawatt package, intended for use as an audio class AB audio amplifier. Thanks to its high power capability the TDA2050 is able to provide up to 35W true rms power into 4 ohm load @ THD = 10%, VS = ±18V, f = 1KHz and up to 32W into 8ohm load@ THD = 10%, VS = ±22V, f = 1KHz.
Moreover, the TDA 2050 delivers typically 50W music power into 4 ohm load over 1 sec at VS= 22.5V, f = 1KHz.The high power and very low harmonic and crossover distortion (THD = 0.05% typ, @ VS = ±22V, PO = 0.1 to 15W, RL=8ohm, f = 100Hz to 15KHz) make the device most suitable for both HiFi and high class TV sets
PC FAN SPEED CONTROLLER - FOR A LOW-NOISE PC
PC FAN SPEED CONTROLLER - FOR A LOW-NOISE PC
The fan runs constantly in many PCs, which may not even be necessary. A simple controller circuit can regulate the fan speed according to demand. This not only saves energy, it also reduces irritation from the fan noise. Only three components are needed to allow the fan speed to be controlled according to the actual demand: one adjustable voltage regulator and two resistors that form a voltage divider. One of the resistors is a NTC thermistor (temperature-sensitive resistor), while the other is a normal resistor. If the 12-V power supply is not located close to the regulator, a decoupling capacitor is also required (see Figure 1).
The thermistor has a rated value of 470 Ω. It sets the output voltage of the LM317T to approximately 7 V at 25 ºC. This should ensure reliable starting of the fan. If the temperature rises to roughly 40°C, the output voltage of the regulator reaches its maximum value and the fan runs at its maximum speed. The voltage drop across the regulator is at least 1.75 V for a motor current of (for example) 300mA, and in any case 2V at the maximum current level of 1 A. You thus might want to consider using a low-drop regulator, such as the National Semiconductor LM2941CT.
To be sure, this increases the size of the circuit to a full five components, which are arranged as shown in Figure 2. However, this approach reduces the voltage drop to 0.2 V at 300 mA or 0.5 V at 1 A. By the way, low-drop voltage regulators are not available in a three-lead package. The circuit can be constructed as a well-insulated ‘free-standing’ assembly, or it can be built on a small piece of prototyping board. In either case, it should be fixed to one of the mounting holes of the fan body (via the cooling tab of the TO-220 regulator package for the free-standing construction). The circuit board should be mounted out of the air stream, but the NTC thermistor must extend into the air stream.
Panasonic Microwave Oven Inverter HV Power Supply ++
early all Panasonic microwave ovens now use an Inverter, and are always labelled with “Inverter” on
the front.
the front.
The High Voltage Power Supply Unit (HV PSU)
The HV PSU measures 165mm x 105mm x 60mm and weighs 650g.
At left is the control daughter board. In front of that on the main board are the opto-isolators for the control and status signals brought out to the green connector. Back left is the rectified mains filter choke. The mains rectifier and switching transistors can just be seen on the heatsink behind the transformer. The mains filter capacitor is at right rear. The HV rectifiers and filters (doubler) are right front – white wires are the HV output from the transformer. The green wire is for grounding the HV +ve. The two lugs t right are for connecting HV -ve and heater to the magnetron. The winding thatcan be seen on the transformer is the primary and is made from 3mm finely stranded wire.
Here’s a view of the control end:
This is the high voltage end:
The circuit for the HV PSU is below
Notes about the circuit:
1. Apart from the block diagram, there is no information on the Inverter cont(o)rol circuit. The circuit itself is centred on one large, unmarked IC, so no help there.
2. The control and status signals seem to be a digital stream (2-3v suggestsa 5V data stream). They are opto-isolated because the majority of the circuit is at mains potential (**BEWARE**). The part that isn’t is at 4kV (*** REALLY BEWARE ***)
3. The mains input side is monitored for both current and (under) voltage. No indication of what the control circuit does with this information.
4. The mains filter capacitor (C702) is very small – only 4uF. In a “normal” switching supply, there is usually 220 or 470 uF in this position.
5. Q701 that does all the hard work is a very heavy duty IGBT – a GT60N90 - 900V @ 60 A. Q702 forms some sort of flywheel circuit. This circuit from a Toshiba IGBT application note looks similar:
6. The HV side has a full-wave doubler rectifier and is marked 4kV @ 300mA. Unlike the classic microwave oven transformers (where one side of the winding is grounded), this means that the secondary must be well insulated from ground on both sides. A simple reconfiguration of the rectifier (replace the caps with diodes) into a bridge circuit should yield 2kV @ 600mA (depending on the diode ratings)
7. The HV filter capacitors are only 8200 pF each, effectively giving 4100pF in the doubler. Considering that the inverter runs at about 30kHz, the reactance is equivalent to that of a 5uF capacitor at 50Hz.
8. The positive side of the HV is grounded, so it’s a –4kV supply. Don’t simply swap the ground from the positive to the negative to get a +4kV supply, as the core of the transformer is also connected to this ground trace and will suddenly rise to 4kV above ground with disastrous and potentially fatal results. Instead, reverse the polarity of the rectifier diodes to get +4kV.
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