Cool Electronic Circuits
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Variable DC Power Supply LM317
2009-10-09 10:51:00
This DC power supply circuit is adjustable using IC Voltage Regulator LM317. LM317 is a versatile and highly efficient 1.2-37V voltage regulator that can provide up to 1.5A of current with a large heat sink. It's ideal for just about any application. This was my first workbench power supply and I still use it. Since LM317 is protected against short-circuit, no fuse is necessary. Thanks to automatic thermal shutdown, it will turn off if heating excessively. All in all, a very powerful (and affordable!) package, indeed. Although voltage regulator LM317 is capable of delivering up to 37V, the DC power supply output circuit here is limited to 25V for the sake of safety and simplicity. Any higher output voltage would require additional components and a larger heat sink. Make sure that the input voltage is at least a couple of Volts higher than the desired output. It's ok to use a trimpot if you're building a fixed-voltage supply. Problems: Follow all the safety precautions when worki
2009-10-09 10:51:00
This DC power supply circuit is adjustable using IC Voltage Regulator LM317. LM317 is a versatile and highly efficient 1.2-37V voltage regulator that can provide up to 1.5A of current with a large heat sink. It's ideal for just about any application. This was my first workbench power supply and I still use it. Since LM317 is protected against short-circuit, no fuse is necessary. Thanks to automatic thermal shutdown, it will turn off if heating excessively. All in all, a very powerful (and affordable!) package, indeed. Although voltage regulator LM317 is capable of delivering up to 37V, the DC power supply output circuit here is limited to 25V for the sake of safety and simplicity. Any higher output voltage would require additional components and a larger heat sink. Make sure that the input voltage is at least a couple of Volts higher than the desired output. It's ok to use a trimpot if you're building a fixed-voltage supply. Problems: Follow all the safety precautions when worki
DC- DC Converter 12V to 24V
2009-10-09 10:09:00
This simple circuit is a DC-DC converter that converting up 12V source to a 24V. It can be used to run radios, small lights, relays, horns and other 24V accessories from a 12V vehicle with a maximum draw of about 800mA. This DC-DC Converter can be used to charge one 12V battery from another, or step up the voltage just enough to provide necessary overhead for a 12V linear regulator. Using one op-amp as a squarewave oscillator to ring an inductor and another op-amp in a feedback loop, it won't drift around under varying loads, providing a stable 24V source for many applications. With a wide adjustment in output this circuit has many uses. Parts List R1-R4,R7-R8 100K 1/4W Resistor R5 470 Ohm 1/2W Resistor R6 10K Linear Pot C1 0.01uF Mylar Capacitor C2 0.1uF Ceramic Disc Capacitor C3 470uF 63V Electrolytic Capacitor D1 1N4004 Rectifier Diode D2 BY229-400 Fast Recovery Diode See Notes Q1 BC337 NPN Power Transistor U1 LM358 Dual Op Amp IC L1 See Notes MISC Board, Wire, Socket
2009-10-09 10:09:00
This simple circuit is a DC-DC converter that converting up 12V source to a 24V. It can be used to run radios, small lights, relays, horns and other 24V accessories from a 12V vehicle with a maximum draw of about 800mA. This DC-DC Converter can be used to charge one 12V battery from another, or step up the voltage just enough to provide necessary overhead for a 12V linear regulator. Using one op-amp as a squarewave oscillator to ring an inductor and another op-amp in a feedback loop, it won't drift around under varying loads, providing a stable 24V source for many applications. With a wide adjustment in output this circuit has many uses. Parts List R1-R4,R7-R8 100K 1/4W Resistor R5 470 Ohm 1/2W Resistor R6 10K Linear Pot C1 0.01uF Mylar Capacitor C2 0.1uF Ceramic Disc Capacitor C3 470uF 63V Electrolytic Capacitor D1 1N4004 Rectifier Diode D2 BY229-400 Fast Recovery Diode See Notes Q1 BC337 NPN Power Transistor U1 LM358 Dual Op Amp IC L1 See Notes MISC Board, Wire, Socket
NiCad Battery Charger
2009-10-09 09:12:00
This battery charger circuit is designed for recharging NiCad batteries based on an AC-powered current source method. It can crank out as much as 1 amp and can be modified to go even higher by choosing different devices for Q1. Since this circuit uses AC line voltages and currents, please exercise extreme caution during assembly, turn-on, and test. NiCAD batteries have a capacity specification called milliamp-hours. This value called "C" is a measure of how much total current they can provide in one hour. Milliamp-hours is another way to express the energy contained in the battery. To recharge a NiCAD battery conservatively, it is common practice to pump a current of 0.1 C into the anode or positive terminal for about 12 hours. Therefore, if you had a D-size NiCAD with a capacity of 4000mAh, you would want to charge it at 400mA for about 12 hours. Another advantage of this charging technique is that it is gentle on batteries and doesn't cause them to lose capacity as quickly as the
2009-10-09 09:12:00
This battery charger circuit is designed for recharging NiCad batteries based on an AC-powered current source method. It can crank out as much as 1 amp and can be modified to go even higher by choosing different devices for Q1. Since this circuit uses AC line voltages and currents, please exercise extreme caution during assembly, turn-on, and test. NiCAD batteries have a capacity specification called milliamp-hours. This value called "C" is a measure of how much total current they can provide in one hour. Milliamp-hours is another way to express the energy contained in the battery. To recharge a NiCAD battery conservatively, it is common practice to pump a current of 0.1 C into the anode or positive terminal for about 12 hours. Therefore, if you had a D-size NiCAD with a capacity of 4000mAh, you would want to charge it at 400mA for about 12 hours. Another advantage of this charging technique is that it is gentle on batteries and doesn't cause them to lose capacity as quickly as the
Laptop Power Supply for Car 95W
2009-09-22 09:27:00
A laptop or notebook computer user while they are away from the home or office knows that sooner or later they will need to plug into a mains outlet to top up the batteries. The car cigarette lighter socket in the car is also an electrical outlet but it can only supply 12 V. That’s no problem for the Laptop Power Supply described here. The laptop power supply described here plugs into a car cigarette lighter socket and produces a 19V nominal output voltage adjustable by + - 0.5V. The input voltage range is from 9.2V to 15V and the output voltage shows good regulation even with large fluctuations of the input voltage. The output can supply 5A continuosly with brief excursions up to 10A. The power semiconductor heatsinks of this laptop power supply are dimensioned fo 5A continuous so extended operation up to 10A will increase dissipation in the adapter and in extreme cases will cause the input fuse to complain. Laptop PSU Adaptor Parts List Resistors: R1 = 5k6 R2 = 51k (51k1) R3
2009-09-22 09:27:00
A laptop or notebook computer user while they are away from the home or office knows that sooner or later they will need to plug into a mains outlet to top up the batteries. The car cigarette lighter socket in the car is also an electrical outlet but it can only supply 12 V. That’s no problem for the Laptop Power Supply described here. The laptop power supply described here plugs into a car cigarette lighter socket and produces a 19V nominal output voltage adjustable by + - 0.5V. The input voltage range is from 9.2V to 15V and the output voltage shows good regulation even with large fluctuations of the input voltage. The output can supply 5A continuosly with brief excursions up to 10A. The power semiconductor heatsinks of this laptop power supply are dimensioned fo 5A continuous so extended operation up to 10A will increase dissipation in the adapter and in extreme cases will cause the input fuse to complain. Laptop PSU Adaptor Parts List Resistors: R1 = 5k6 R2 = 51k (51k1) R3
Power Converter 12 VDC-220 VAC 50W
2009-09-22 08:50:00
The power converter circuit is aimed to convert 12 VDC to 220 VAC and the process known as inverter. By inverting process will produce a 50W power converter that would supply different small appliances. The DC to AC inverters are widely used in rural electrification the require AC power which includes solar home systems, health clinics, and community centers. Power Converter can also be used for other photovoltaic systems that convert light energy into electricity such as weekend homes and remote cabins, boats and caravans, and small telecom photovoltaic systems. Power Converter Circuit Explanation The power converter circuit is constituted by the oscillator, round the IC1, one divider IC2, one unstable multivibrator IC3, which give in the output symmetrical square signal of frequency 50HZ, follow a buffer stage with Fet Q1-2, the drive stage Q3-4 and the power stage Q4-5, the power transistors Q5-6, should they are placed in heatsink. The diodes Zener D2-3, protect the power
2009-09-22 08:50:00
The power converter circuit is aimed to convert 12 VDC to 220 VAC and the process known as inverter. By inverting process will produce a 50W power converter that would supply different small appliances. The DC to AC inverters are widely used in rural electrification the require AC power which includes solar home systems, health clinics, and community centers. Power Converter can also be used for other photovoltaic systems that convert light energy into electricity such as weekend homes and remote cabins, boats and caravans, and small telecom photovoltaic systems. Power Converter Circuit Explanation The power converter circuit is constituted by the oscillator, round the IC1, one divider IC2, one unstable multivibrator IC3, which give in the output symmetrical square signal of frequency 50HZ, follow a buffer stage with Fet Q1-2, the drive stage Q3-4 and the power stage Q4-5, the power transistors Q5-6, should they are placed in heatsink. The diodes Zener D2-3, protect the power
VHF FM Receiver TDA7000 88-108 MHz
2009-09-18 20:02:00
Here is a very simple VHF FM receiver which is little more than a single IC and a "slack handfull" of capacitors. Note that an external amplifier is a really necessity since the unit only delivers about 70mV of AF. See High Power FM Wireless Microphone transmitters, probably because it is so simple too. The 10K resistor (*) is only required if you want the receiver to mute (squelch) under no-signal conditions. You could add a 100K in series with this resistor to get an adjustable squelch. This circuit will JUST drive a crystal earphone or high impedance headphones directly, but an output isolating capacitor (100nF) is needed for any other device. L1 is 6 turns No 18 SWG enamelled wire on a 5mm former, but you may have to play with the values a bit. I used a coil fabricated on the PCB itself, tuned with a trimmer capacitor. All the other components are just a bunch of capacitors which are fitted to the board at the other side of the chip, just to make it look a bit prettier.
2009-09-18 20:02:00
Here is a very simple VHF FM receiver which is little more than a single IC and a "slack handfull" of capacitors. Note that an external amplifier is a really necessity since the unit only delivers about 70mV of AF. See High Power FM Wireless Microphone transmitters, probably because it is so simple too. The 10K resistor (*) is only required if you want the receiver to mute (squelch) under no-signal conditions. You could add a 100K in series with this resistor to get an adjustable squelch. This circuit will JUST drive a crystal earphone or high impedance headphones directly, but an output isolating capacitor (100nF) is needed for any other device. L1 is 6 turns No 18 SWG enamelled wire on a 5mm former, but you may have to play with the values a bit. I used a coil fabricated on the PCB itself, tuned with a trimmer capacitor. All the other components are just a bunch of capacitors which are fitted to the board at the other side of the chip, just to make it look a bit prettier.
LED Power Meter Using Digital Multimeter
2009-09-18 18:44:00
LED power Meter circuit is a simple RF detector using diodes to charge a capacitor. The voltage developed across the capacitor is indicated by a multimeter set to a low voltage range. The circuit is soldered together without the need for a PC board, as can be seen in the diagram below and paper clips are used for the positive and negative terminals of the multimeter. The level power output of an FM transmitter is indicated by the illumination of a LED and the voltage reading on the multimeter gives a further indication of the output. A digital multimeter may be used but the presence of RF may produce a false reading. Likewise, the radiated energy may upset some analogue meters and you may get full scale deflection on the 15v range as well as the 250v range! But the LED won't lie. It will accurately indicate the RF and you can see the change in brightness as you adjust the coils in the output stage. Some of the cheapest and simplest multimeters will give the best results as they h
2009-09-18 18:44:00
LED power Meter circuit is a simple RF detector using diodes to charge a capacitor. The voltage developed across the capacitor is indicated by a multimeter set to a low voltage range. The circuit is soldered together without the need for a PC board, as can be seen in the diagram below and paper clips are used for the positive and negative terminals of the multimeter. The level power output of an FM transmitter is indicated by the illumination of a LED and the voltage reading on the multimeter gives a further indication of the output. A digital multimeter may be used but the presence of RF may produce a false reading. Likewise, the radiated energy may upset some analogue meters and you may get full scale deflection on the 15v range as well as the 250v range! But the LED won't lie. It will accurately indicate the RF and you can see the change in brightness as you adjust the coils in the output stage. Some of the cheapest and simplest multimeters will give the best results as they h
LED Indicator Relay Timer Circuit-9 Second
2009-09-15 05:59:00
This Relay Timer circuit provides a visual time 9 second delay using ten LED before control by closing a 12 VDC relay. That the reset switch has closed, IC 4017 decade counter will be reset to zero count which illuminates the LED driven from pin 3. IC 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 Vdc. That time the switch is opened, the transistor in parallel with the timing capacitor (22uF) is shut off allowing the capacitor to begin charging and the IC 555 timer circuit to produce an approximate one second clock signal to the decade counter. The counter advances on each positive going change at pin 14 and is enabled with pin 13 terminated low. When the 9th count is reached, pin 11 and 13 will be high, stopping the counter and energizing the relay. Longer delay times can be obtained with most capacitor or most resistor at pins 2 and 6 of the IC 555 timer Source: 9 Sec Timer with L
2009-09-15 05:59:00
This Relay Timer circuit provides a visual time 9 second delay using ten LED before control by closing a 12 VDC relay. That the reset switch has closed, IC 4017 decade counter will be reset to zero count which illuminates the LED driven from pin 3. IC 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 Vdc. That time the switch is opened, the transistor in parallel with the timing capacitor (22uF) is shut off allowing the capacitor to begin charging and the IC 555 timer circuit to produce an approximate one second clock signal to the decade counter. The counter advances on each positive going change at pin 14 and is enabled with pin 13 terminated low. When the 9th count is reached, pin 11 and 13 will be high, stopping the counter and energizing the relay. Longer delay times can be obtained with most capacitor or most resistor at pins 2 and 6 of the IC 555 timer Source: 9 Sec Timer with L
Variable Dual Power Supply LM317-LM337
2009-09-15 05:37:00
This is a bench top power supply that can be used to power circuits or devices during development work in the lab. More specifically it is an adjustable, tracking, dual rail supply which means there are two supply voltages, one positive, one negative, that are adjusted by a common potentiometer such that supply voltages are equal in magnitude. It is capable of supplying up to +/- 15V DC at up to 1A. This is sufficient for the majority of small signal electronic projects. Power Supply Schematic Power Supply circuit above shows the circuit layout for this project. A centre tapped transformer (TR1) is used with two 12V secondary windings with its centre tap tied to ground. This allows positive and negative voltages to be generated with respect to the central ground. Rectification follows based upon the bridge rectifier (BR1) and smoothing capacitors (C1, C2, C4 and C5). Two linear regulators are used, an LM317 on the positive side and an LM337 on the negative side. These regulators k
2009-09-15 05:37:00
This is a bench top power supply that can be used to power circuits or devices during development work in the lab. More specifically it is an adjustable, tracking, dual rail supply which means there are two supply voltages, one positive, one negative, that are adjusted by a common potentiometer such that supply voltages are equal in magnitude. It is capable of supplying up to +/- 15V DC at up to 1A. This is sufficient for the majority of small signal electronic projects. Power Supply Schematic Power Supply circuit above shows the circuit layout for this project. A centre tapped transformer (TR1) is used with two 12V secondary windings with its centre tap tied to ground. This allows positive and negative voltages to be generated with respect to the central ground. Rectification follows based upon the bridge rectifier (BR1) and smoothing capacitors (C1, C2, C4 and C5). Two linear regulators are used, an LM317 on the positive side and an LM337 on the negative side. These regulators k
Thermistor Temperature Monitor Circuit
2009-09-11 14:17:00
Here's a simple op-amp circuit with a NTC thermistor as sensor that will trigger a relay when a preset temperature is reached. There is no hysteresis in this circuit, so that if the temperature changes rapidly, then the relay may switch rapidly. This sensor circuit uses an ordinary NTC thermistor with a resistance of 47k at room temperature. A suitable part from Maplin Electronics is FX42V. The circuit is set in balance by adjusting the the 47k potentiometer. Any change in temperature will alter the balance of the circuit, the output of the op-amp will change and energize the relay. Swapping the position of the thermistor and 47k resistor makes a cold or frost alarm. At room temperature (25 degrees Celsius) a 47k NTC thermistor resistance is approximately 47k. The non-inverting op-amp input will then be roughly half the supply voltage, adjusting the 47k pot should allow the relay to close or remain open. To calibrate the device, the thermistor ideally needs to be at the required ope
2009-09-11 14:17:00
Here's a simple op-amp circuit with a NTC thermistor as sensor that will trigger a relay when a preset temperature is reached. There is no hysteresis in this circuit, so that if the temperature changes rapidly, then the relay may switch rapidly. This sensor circuit uses an ordinary NTC thermistor with a resistance of 47k at room temperature. A suitable part from Maplin Electronics is FX42V. The circuit is set in balance by adjusting the the 47k potentiometer. Any change in temperature will alter the balance of the circuit, the output of the op-amp will change and energize the relay. Swapping the position of the thermistor and 47k resistor makes a cold or frost alarm. At room temperature (25 degrees Celsius) a 47k NTC thermistor resistance is approximately 47k. The non-inverting op-amp input will then be roughly half the supply voltage, adjusting the 47k pot should allow the relay to close or remain open. To calibrate the device, the thermistor ideally needs to be at the required ope