Schematics Simple Battery Charger using LM350

Simple Battery Charger using LM350 circuit diagram

The schematic diagram can be used for charging the 12V lead acid batteries.

The circuit is designed as a constant voltage source with a negative temperature coefficient. The transistor Q1 (BD 140) is used as the temperature sensor. The transistor Q2 is used to prevent the battery from discharging through R1 when the mains power is not available. The circuit is designed based on the voltage regulator IC LM350. The output voltage of the charger can be adjusted between 13-15 V by varying the POT R6.

The LM350 will try to keep the voltage drop between its input pin and the output pin at a constant value of 1.25V. So there will be a constant current flow through the resistor R1. Q1 act here as a temperature sensors with the help of components R6/R3/R4 which more or less control the base current of Q1. As the emitter/base connection of transitor Q1, just like any other semiconductor, contains a temperature coefficient of -2mV/°C, the output voltage will also show a negative temperature coefficient. That one is only a factor of 4 larger, because of the variation of the emitter/basis of Q1 multiplied by the division factor of P1/R3/R4. This results in approximately -8mV/°C. The LED will glow whenever the mains power is available.

The transistor Q1 must be placed as close as possible to the battery.
Use a 20 to 30 V / 3A DC power supply for powering the circuit.
This circuit is not possible for charging GEL type batteries as it draw large amounts of current.

Here the LM350 pin layout:
 Here the LM350 pin layout
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7805 Regulator schema
If you want to build a small power supply + 5 V, regulator 7805 is a superb selection, specifically for experiments with digital circuits that the IC is commonly available on the market. This IC overheating security attributes, stops current supply additional heat.This circuit can provide the output of V + 5 to about one hundred and fifty my present, but is often improved to 1 A once great cooling is additional to your IC 7805 regulator.Capacitors should be adequate to high voltage rating to manage safely on the circuit of power supply input voltage. The 7805 regulator circuit is extremely simple to do a bit of stripboard for example. Case modified existing exit and VolatgesIn you want to last output of more than 150 mA, make sure that you update this output about 1. transform the processor that you use for your transformer who has an existing rating more than ever before. Really don't forget to put the heatsink in the IC 7805 regulator.If you need an output greater than + 5 voltage V, sure that you change the circuit by changing the 7805 IC regulator to a single regulator 78xx ICs output voltage. You must understand that neither less 3V of entry than the voltage of output you will want to carefully for function of IC.

View the original article here
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LM56 diagram of Circuit of the Thermostat project

The values of LM56 Thermostat project Circuit diagram of R1, R2 and R3 for the points of travel, VT1 and VT2 can be determined using the subsequent equations.
VT1 = 1. 250V x (R1) / (R1 R2 + R3)
VT2 = 1. 250V x (R1 + R2) / (R1 R2 + R3)
(R1 R2 + R3) = 27 k Ohms and
VT1 or T2 = [6.20 mV/degree Celsius x T] = 395 mV thus:
R1 = VT1 / (1. 25V) x 27 k Ohms
R2 = (VT2 / (1. 25V) x 27 k Ohms)-R1
R3 = 27 k Ohms - R1, R2
This thermostat of electronic circuit with IC LM56 diagram what simple project, you can use as reference. As you know, IC LM56 is correct double output thermostat low power characterized by National Semiconductors. trip temperature stable 2 points called VT1 and VT2 are made with dividing the LM56 IC 1,250 reference internal voltage volts by three outside resistors (R1, R2 and R3) component. There are 2 digital outputs for LM56 IC which is that output1 becomes weak when the temperature increases over T1 and goes high when the temperature decreases below (temperature T1±Hysteresis). Component IC LM56 has a variety of useful features as internal voltage reference internal temperature sensor, 2 internal voltage comparators, etc.
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Automatic reversing loop control circuit

Automatic control inverter Circuit automatic reversing loop Circuit loop - Notes*
It is not the purpose of this page to provide a detailed explanation of the IC used by this circuit. If you want more information on this subject, please refer to page of made in the section with a chip LM556 Timer toggle various circuits of this site and, also, the Visible light Photo detector Circuits.
The circuit uses the circuit of sensor based phototransistor in the sense of the position of a train is approaching or is in the loop of inversion.
Track polarity reversing is not covered by this page and will have to be determined by the user.
Please read before using these Circuit ideas
Explanations for the circuits on these pages cannot hope to cover all situations on each page layout. For this reason be willing to do some experiments to get the results you want. This is particularly true of circuits such as circuits "Across Track Infrared Detection", and any other circuit based on other than to direct, as electronic input switches.
If you use one of these circuit ideas, ask your parts supplier for a copy of the data sheets of the manufacturers for all components that you have not used before. These leaves contain a wealth of information of design data and circuit that no electronic or printed article could approach and will save time and may cause damage to the components themselves. These data sheets can often found on the web site of device manufacturers.
Although the circuits are functional pages are not intended to be a complete description of each circuit, but rather as guides to adapt them for use by others. If you have any questions or comments please send them to the email address on the page Index of Circuit.
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Infrared wireless headphones amplifier circuit

"" "Browser amplifier" home "" Rangkaian infrared Wireless Headphone Amplifier

Rangkaian infrared Wireless Headphone Amplifier using the low cost project, can reproduce AUDIO of TV without disturbing anyone. It uses not all wire between TV and the helmet. Instead the pair of wires, it uses the invisible infrared light to transmit audio signals from TV to the helmet. Without the help of a wide range of lens 6 metres is possible. Scope can be extended using lenses and reflectors with sensors IR transmitters and receivers. IR Transmitter uses amplifier transistor two-storey driving two IR LEDs connected in series. An audio output transformer is used (on the back) to couple the Audio of TV output to the IR transmitter.
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Series of USB Sound Card PCM2702

The core of this construction is 16-bit stereo digital-to-converter analog with USB interface PCM2702.
PCM2702 needs only a few additional parts to work. The schema is not complex. Sound card may be supplied directly by the USB (jump W1) or feeding external supply (hopping W3). PCM2702 requires two power supply 3. 3V (3V-3. 6V) and 5V (4 5V-5. 5V). I used fixed output LDO TPS76733Q for 3 voltage. 3V (IO2) and adjustable output LDO TPS76701Q to 5V (IO3) voltage. The two LDO are produced by it, I used this because I had it in my drawer. Any similar LDO may be used. IO3 output voltage must be set to somewhat less than the input voltage to allow good stabilization LDO, in my case of output voltage is set to 4. The output voltage can be set by adjustable resistance R33. Provision of low-power, IO3 may be shorted by hopping W3. LED D3 signalizes power on.
Small ferrite beads are placed before all the pins of the power of PCM2702 and Vbus and GND of the USB. These small beads reduce high-frequency buzzing. I had a problem to find this small SMD ferrite beads in the stores of but finally I acquire few old hard disk. They are not absolutely necessary, you can use zero resistance ohm instead of them.
Low-pass filter is placed in the output path to reduce the frequency of sampling. A double OPA2353UA op amp is configured as a lowpass filter of order 2 at the stereo address. Diode D1 LED is illuminated when PCM2702 plays the audio data received by the USB bus. Diode D2 LED is illuminated when the USB bus suspends transmission of audio data to the PCM2702.
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Schematic Diagram HP TX1000 Entertainment Tablet PC GPU Fix

A friend of mine ask for a favor to take a look at his HP TX1000 Entertainment Tablet PC blackout LCD problem. I have no idea on how to fix this until I found below video.

Instead of using bulb, I used a heat blower to re-flow the chip.

From my observation, there is a the gap between the GPU and the heat sink was join by a burned thermal conductive silicone sponge.

I replace this with an aluminum foil folded a couple of times to get just the right thickness.

After reassemble it back together and now, the moment of truth, Hey! it works! :-)

Thanks a lot jasonshay2. You really save my day.
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Schematics Dual Mono PSU & Velleman K4700 in a Quad 405 PCB

Joost built a Velleman K4700 Loudspeaker-protection kit in a Quad 405 with a Dada Electronics Dual Mono Power-supply.

As there is no space above the PSU he fixed it to the Back-panel behind the transformer. This may be the best solution with a classical PSU as well...

The "-" of the Speakers goes to the Power-supply and from there to the central Mass-point. Another wire from the central Mass-point goes to the Velleman.

This is not only a practical solution, it works very well!
Click on the picture to enlarge.

The Velleman K4700 kit and the Assembled version are available in the Webshop.

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Schematic Diagram Wireless Dimmer Circuit Project

AVR wireless dimmer Project
At first we have to modify the layout of the old Avr dimmer. I don't think the RS232 interface will be used much when we have the wireless option available, so all the parts for the RS232 will have to go, the other thing that we don't really need anymore is the crystal with the 2 capacitors, because the ATtiny2313 has a build in RC clock of 4 and 8 Mhz which is more than sufficient. One more thing that could go is the infrared receiver, but this doesn't take much room on the circuit board so I will leave it on for the moment. The last thing we need to change is the power supply. The iDwaRF module needs between 2.7 to 3.6 Volts. The ATTiny2313 will run on a voltage between 2.7 to 5.5 volts and the infrared receiver needs 2,7 to 5,5 Volts if we use the TSOP 31236. So if we decide on a power supply of 3.3 Volts all the components will be happy.

Changing the voltage from 5 to 3.3 Volts sounds easier then it turned out to be. Negative regulators of -3.3 Volt are rare and if that is not all the Wireless module seems to have a peak current of more than 60 mA. Our old design could only supply an average of 20 mA. Also I want the dimmer to be power efficient, since I might end up with 10 or more dimmers, regulating everything in the house. So I am thinking of a switching regulator. This way we have a very efficient power supply that can temperarely supply higher currents. More will follow. This will need some testing.

At first we have to modify the layout of the old Avr dimmer. I don't think the RS232 interface will be used much when we have the wireless option available, so all the parts for the RS232 will have to go, the other thing that we don't really need anymore is the crystal with the 2 capacitors, because the ATtiny2313 has a build in RC clock of 4 and 8 Mhz which is more than sufficient. One more thing that could go is the infrared receiver, but this doesn't take much room on the circuit board so I will leave it on for the moment. The last thing we need to change is the power supply. The iDwaRF module needs between 2.7 to 3.6 Volts. The ATTiny2313 will run on a voltage between 2.7 to 5.5 volts and the infrared receiver needs 2,7 to 5,5 Volts if we use the TSOP 31236. So if we decide on a power supply of 3.3 Volts all the components will be happy.

Changing the voltage from 5 to 3.3 Volts sounds easier then it turned out to be. Negative regulators of -3.3 Volt are rare and if that is not all the Wireless module seems to have a peak current of more than 60 mA. Our old design could only supply an average of 20 mA. Also I want the dimmer to be power efficient, since I might end up with 10 or more dimmers, regulating everything in the house. So I am thinking of a switching regulator. This way we have a very efficient power supply that can temperarely supply higher currents. More will follow. This will need some testing.

IR Light Dimmer v.1
This is a device for adjusting lights in your home with any type of remote controller (tv, dvd, video,…). Today we are using many devices in our homes to improve quality of our life and this is another example on how you can enhance a simple procedure like switching the lights ON/OFF. It may be difficult to many of us to stand up from our chair only to switch lights, so try imagining yourself doing this with your remote controller.

Projects/IR light dimmer v1
This is a very simple IR light dimmer that you will wish to have sooner or later, especially those who are lazy enough to get up and turn off the lights. There are two versions of PCB for two sizes of capacitors, so PCBs are: 32.5 x 26.5mm and 28.5 x 27mm.

Features of current beta version of firmware:
- Soft start (gradually turning on the light bulb)
- Soft down (gradually turning off the light bulb)
- Learning IR codes from RC5 and NEC remotes
- Dimming in 10 levels by using only IR remote
- Previous dimm-level remembering when operating with remote
- Sleep timer in duration of 1.6min for 60Hz version and 2min for 50Hz version
- ON/OFF control with wall pushbutton

LM3445 TRIAC Dimmer Demo Video

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Schematic Diagram Blinking LED Circuit Diagram

This is a blinking LED circuit diagram.Here I have used common IC NE555.If you want to change the speed of this circuit you can change the value of R2.Then you can do that.


* Use a PCB to build this circuit
* You can operate this circuit with 9V

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Schematics 2×22W Stereo Car Audio Amplifier schematic diagram

This is a schematic diagram of stereo audio amplifier for your car. The circuit is powered by a single IC TDA1553 with some external components, this IC will handle your stereo car audio system.

2x22W Stereo Car Audio Amplifier circuit diagram

The TDA1553CQ is a monolithic integrated class-B output amplifier in a 13-lead plastic DIL-bent-SIL power package. It contains 2×22 W amplifiers in BTL configuration. The device is primarily developed for car radio applications.

The TDA1553CQ contains two identical amplifiers with differential input stages and can be used for bridge applications. The gain of each amplifier is fixed at 26 dB.

Special features of the device are:

3-state mode switch
· standby: low supply current (<100>

Loudspeaker protection
When a short-circuit to ground occurs, which forces a DC voltage across the loudspeaker of >= V, a built-in protection circuit becomes active and limits the DC voltage across the loudspeaker to <= V. Pin 12 detects the status of the protection circuit (e.g. for diagnostic purposes).

Short-circuit protection
If any output is short-circuited to ground during the standby mode, it becomes impossible to switch the circuit to the mute or operating condition. In this event the supply current will be limited to a few milliamps.

Download the TDA1553CQ datasheet

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6 Watts FM broadcast 87,5-108MHz

The layout of the BFR91-BFR96(S)-2SC1971 6 Watts FM broadcast (87,5-108MHz) Profline
Broadband RF-amplifier has been created with sPRINT Layout v3.0.
You can get a Shareware copy at:
The pcb outline is: 85 x 55 mm (width x height), bitmap resolution is 600dpi.
Use FR-4 double sided photoresist epoxy pcb material for best results.

(*) When printing the layout, be sure to resize it!

Design (C)2005 Rdvv, The Netherlands.
Rework (C)2006 by Helix. The Netherlands.
Intitial 2SC1971 microstripline design (C)2002 Sotiris Papadimitriou/ASPiSYS, Ltd. Greece.
(That should cover it!)

Breedband%20Foto_Radio Transmitter Amplifier 6Watt MicroStripline 2SC1971 2sc1971-microstripline(comp)_Radio Transmitter Amplifier 6Watt MicroStripline 2SC1971 2sc1971-microstripline(pcb)_Radio Transmitter Amplifier 6Watt MicroStripline 2SC1971 2sc1971-microstripline(silk)_Radio Transmitter Amplifier 6Watt MicroStripline 2SC1971

BFR91-BFR96(S)-2SC1971 6 Watts FM broadcast (87,5-108MHz) Profline Broadband RF-amplifier

All component values are drawn on the .comp and .silklayer bitmaps, with the following

1.- mount a ferroxcube bead (3 mm diameter, 5 mm length) over one of the wires of the 56E
    resistor (i.e. the wire wich is connected to the base of the 2SC1971 rf-transistor)
2.- the 1uH and 4.7uH coils are ready-made molded type coils.
3.- resistor values are in Ohms, 0.25watts (carbon or metalfilm).
4.- the 47E adjustable resistor measures 10mm diameter, vertical mount (Piher).
5.- all capacitor are ceramic except the 10nF and 100nF ones, these are multilayer types.
6.- the two trimmer capacitors are 22pF, Green (Philips).
7.- the two 150E resistors (at the collector of the BFR96(S) are mounted vertically.

(I)  make sure to mount the rf-transistor on a appropriate heatsink and use some thermal
     heatsink compound between the flange of the rf-transistor and the heatsink or cabinet!
     (Thermal resistance heatsink at least 6°C/W.)
(II) all parts are soldered directly on the toplayer of the pcb.

NOTE: on several places connect the groundplane (bottomlayer) to the groundplane on the
      toplayer, choose at will.

Happy constructing!

(C)2006 Helix. The Netherlands.

URL  :

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RF circuit Amplifier sd1127 transmitter 5Watt

SD1127 RF power transistor 5watt. This transistor circuit amplifier mounts somewhat differently from all the other parts. Turn over the PC board and set the transistor snugly into the large hole and bend the leads over and into
the indicated holes. The leads should be as short as possible without shorting against the transistor case. Solder the three transistor leads. See drawing in the step below.

Now we call for something unusual - soldering the transistor case to the PC board. Run a neat "flow" of solder around the transistor case to the PC board ground plane. The SD1127 power transistor is designed by the manufacturer to be soldered directly to a PC board ground plane for heat sinking and proper VHF performance. This part is different from other metal can transistors in that the case is connected internally to the emitter rather than the collector.

This provides much higher gain at VHF frequencies.

sd1127_RF_circuit_Amplifier 5Watt (SD1127)

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Circuit Running Message Display Schematics

Light emitting diodes are advan- tageous due to their smaller size, low current consumption and catchy colours they emit. Here is a running message display circuit wherein the letters formed by LED arrangement light up progressively. Once all the letters of the message have been lit up, the circuit gets reset. The circuit is built around Johnson decade counter CD4017BC (IC2). One of the IC CD4017BE�s features is its provision of ten fully decoded outputs, making the IC ideal for use in a whole range of sequencing operations. In the circuit only one of the outputs remains high and the other outputs switch to high state successively on the arrival of each clock pulse. The timer NE555 (IC1) is wired as a 1Hz astable multivibrator which clocks the IC2 for sequencing operations. On reset, output pin 3 goes high and drives transistor T7 to �on� state. The output of transistor T7 is connected to letter �W� of the LED word array (all LEDs of letter array are connected in parallel) and thus letter �W� is illuminated. On arrival of first clock pulse, pin 3 goes low and pin 2 goes high. Transistor T6 conducts and letter �E� lights up. The preceding letter �W� also remains lighted because of forward biasing of transistor T7 via diode D21. In a similar fashion, on the arrival of each successive pulse, the other letters of the display are also illuminated and finally the complete word becomes visible. On the following clock pulse, pin 6 goes to logic 1 and resets the circuit, and the sequence repeats itself. The frequency of sequencing operations is controlled with the help of potmeter VR1.
The display can be fixed on a veroboard of suitable size and connected to ground of a common supply (of 6V to 9V) while the anodes of LEDs are to be connected to emitters of transistors T1 through T7 as shown in the circuit. The above circuit is very versatile and can be wired with a large number of LEDs to make an LED fashion jewellery of any design. With two circuits connected in a similar fashion, multiplexing of LEDs can be done to give a moving display effect
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Circuit Automatic Room Lights Schematics

An ordinary automatic room power control circuit has only one light sensor. So when a person enters the room it gets one pulse and the lights come �on.� When the person goes out it gets another pulse and the lights go �off.� But what happens when two persons enter the room, one after the other? It gets two pulses and the lights remain in �off� state. The circuit described here overcomes the above-mentioned problem. It has a small memory which enables it to automatically switch �on� and switch �off� the lights in a desired fashion. The circuit uses two LDRs which are placed one after another (separated by a distance of say half a metre) so that they may separately sense a person going into the room or coming out of the room. Outputs of the two LDR sensors, after processing, are used in conjunction with a bicolour LED in such a fashion that when a person gets into the room it emits green light and when a person goes out of the room it emits red light, and vice versa. These outputs are simultaneously applied to two counters. One of the counters will count as +1, +2, +3 etc when persons are getting into the room and the other will count as -1, -2, -3 etc when persons are getting out of the room. These counters make use of Johnson decade counter CD4017 ICs. The next stage comprises two logic ICs which can combine the outputs of the two counters and determine if there is any person still left in the room or not. Since in the circuit LDRs have been used, care should be taken to protect them from ambient light. If desired, one may use readily available IR sensor modules to replace the LDRs. The sensors are installed in such a way that when a person enters or leaves the room, he intercepts the light falling on them sequentially�one after the other. When a person enters the room, first he would obstruct the light falling on LDR1, followed by that falling on LDR2. When a person leaves the room it will be the other way round. In the normal case light keeps falling on both the LDRs, and as such their resistance is low (about 5 kilo-ohms). As a result, pin 2 of both timers (IC1 and IC2), which have been configured as monostable flip-flops, are held near the supply voltage (+9V). When the light falling on the LDRs is obstructed, their resistance becomes very high and pin 2 voltages drop to near ground potential, thereby triggering the flip-flops. Capacitors across pin 2 and ground have been added to avoid false triggering due to electrical noise. When a person enters the room, LDR1 is triggered first and it results in triggering of monostable IC1. The short output pulse immediately charges up capacitor C5, forward biasing transistor pair T1-T2. But at this instant the collectors of transistors T1 and T2 are in high impedance state as IC2 pin 3 is at low potential and diode D4 is not conducting. But when the same person passes LDR2, IC2 monostable flip-flop is triggered. Its pin 3 goes high and this potential is coupled to transistor pair T1-T2 via diode D4. As a result transistor pair T1-T2 conducts because capacitor C5 retains the charge for some time as its discharge time is controlled by resistor R5 (and R7 to an extent). Thus green LED portion of bi-colour LED is lit momentarily. The same output is also coupled to IC3 for which it acts as a clock. With entry of each person IC3 output (high state) keeps advancing. At this stage transistor pair T3-T4 cannot conduct because output pin 3 of IC1 is no longer positive as its output pulse duration is quite short and hence transistor collectors are in high impedance state. When persons leave the room, LDR2 is triggered first followed by LDR1. Since the bottom half portion of circuit is identical to top half, this time with the departure of each person red portion of bi-colour LED is lit momentarily and output of IC4 advances in the same fashion as in case of IC3. The outputs of IC3 and those of IC4 (after inversion by inverter gates N1 through N4) are ANDed by AND gates (A1 through A4) are then wire ORed (using diodes D5 through D8). The net effect is that when persons are entering, the output of at least one of the AND gates is high, causing transistor T5 to conduct and energise relay RL1. The bulb connected to the supply via N/O contact of relay RL1 also lights up. When persons are leaving the room, and till all the persons who entered the room have left, the wired OR output continues to remain high, i.e. the bulb continues to remains �on,� until all persons who entered the room have left. The maximum number of persons that this circuit can handle is limited to four since on receipt of fifth clock pulse the counters are reset. The capacity of the circuit can be easily extended for up to nine persons by removing the connection of pin 1 from reset pin (15) and utilising Q1 to Q9 outputs of CD4017 counters. Additional inverters, AND gates and diodes will, however, be required
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Schematic Diagram Biquad ant. for WLAN

Biquad Antenna for 2.4 GHz - 802.11b/g - WiFi - WLAN

After some research, I found out that the simplest type of
homemade WLAN antenna is BiQuad antenna. Many sites provide good
instruction on how to assemble it.

(refer below)

I'm not going to repeat it.

My Antenna

So I start by recycling some parts that I found in my workshop
and construct it.

I took about 10-20 min. for me to finished it.

The critical process is to make the element.

With proper method and dimension this thing will work.

Good Luck!!!

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Circuit Emergency Light Schematics

The circuit of automatic emergency light presented here has the following features: 1. When the mains supply (230V AC) is available, it charges a 12V battery up to 13.5V and then the battery is disconnected from the charging section. 2. When the battery discharges up to 10.2V, it is disconnected from the load and the charging process is resumed. 3. If the mains voltage is available and there is darkness in the room, load (bulb or tube) is turned on by taking power from the mains; otherwise the battery is connected to the load. 4. When the battery discharges up to 10.2V and if the mains is not yet available, the battery is completely disconnected from the circuit to avoid its further discharge. The mains supply of 230V AC is stepped down to 18V AC (RMS) using a 230V AC primary to 0-18V AC, 2A secondary transformer (X1), generally used in 36cm B&W TVs. Diodes D1 through D4 form bridge rectifier and capacitor C5 filters the voltage, providing about 25V DC at the output. Charging section includes 33-ohm, 10-watt resistor R2 which limits the charging current to about 425 mA when battery voltage is about 10.2V, or to 325 mA when battery voltage is about 13.5V. When the battery charges to 13.5V (as set by VR2), zener diode D17 goes into breakdown region, thereby triggering triac TR1. Now, since DC is passing through the triac, it remains continuously �on� even if the gate current is reduced to zero (by disconnecting the gate terminal). Once the battery is fully charged, charging section is cut-off from the battery due to energisation of relay RL2. This relay remains �on� even if the power fails because of connection to the battery via diode D10. S4, a normally closed switch, is included to manually restart the charging process if required. Battery disconnect and charging restart section comprises an NE555 timer (IC2) wired in monostable mode. When the battery voltage is above 10.2V (as indicated by red LED D15), zener diode (D16) remains in the breakdown region, making the trigger pin 2 of IC2 high, thereby maintaining output pin 3 in low voltage state. Thus, relay RL3 is �on� and relay RL4 is �off.� But as soon as the battery voltage falls to about 10.2V (as set by preset VR1), zener diode D16 comes out of conduction, making pin 2 low and pin 3 high to turn �on� relay RL4 and orange LED D13. This also switches off relay RL3 and LED D15. Now, if the mains is available, charging restarts due to de-energisation of relay RL2 because when relay RL4 is �on,� it breaks the circuit of relay RL2 and triac TR1. But if the mains supply is not present, both relays RL3 and RL1 de-energise, disconnecting the battery from the remaining circuit. Thus when battery voltage falls to 10.2 volts, its further discharge is eliminated. But as soon as the mains supply resumes, it energises relay RL1, thereby connecting the battery again to the circuit. Light sensor section also makes use of a 555 timer IC in the monostable mode. As long as normal light is falling on LDR1, its resistance is comparatively low. As a result pin 2 of IC3 is held near Vcc and its output at pin 3 is at low level. In darkness, LDR resistance is very high, which causes pin 2 of IC3 to fall to near ground potential and thus trigger it. As a consequence, output pin 3 goes high during the monostable pulse period, forward biasing transistor T3 which goes into saturation, energising relay RL5. With auto/bypass switch S2 off (in auto mode), the load gets connected to supply via switch S3. If desired, the load may be switched during the day-time by flipping switch S2 to �on� position (manual). Preset VR3 is the sensitivity control used for setting threshold light level at which the load is to be automatically switched on/off. Capacitors with the relays ensure that there is no chattering of the relays. When the mains is present, diode D8 couples the input voltage to regulator IC1 whereas diode D10 feeds the input voltage to it (from battery) in absense of mains supply. Diode D5 connects the load to the power supply section via resistor R5 when mains is available (diode D18 does not conduct). However, when mains power fails, the situation reverses and diode D18 conducts while diode D5 does not conduct. . The load can be any bulb of 12 volts with a maximum current rating of 2 amperes (24 watts). Resistor R5 is supposed to drop approximately 12 volts when the load current flows through it during mains availability . Hence power dissipated in it would almost be equal to the load power. It is therefore desirable to replace R5 with a bulb of similar voltage and wattage as the load so that during mains availability we have more (double) light than when the load is fed from the battery. For setting presets VR1 and VR2, just take out (desolder one end) diodes D7, D10 and D18. Connect a variable source of power supply in place of battery. Set preset VR1 so that battery-high LED D15 is just off at 10.2V of the variable source. Increase the potential of the variable source and observe the shift from LO BAT LED D13 to D15. Now make the voltage of the source 13.5V and set preset VR2 so that relay RL2 just energises. Then decrease the voltage slowly and observe that relay RL2 does not de-energise above 10.2V. At 10.2V, LED D15 should be off and relay RL2 should de-energise while LED D13 should light up. Preset VR3 can be adjusted during evening hours so that the load is �on� during the desired light conditions
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Circuit Automatic Dual output Display Schematics

This circuit lights up ten bulbs sequentially, first in one direc- tion and then in the opposite direction, thus presenting a nice visual effect. In this circuit, gates N1 and N2 form an oscillator. The output of this oscillator is used as a clock for BCD up/down counter CD4510 (IC2). Depending on the logic state at its pin 10, the counter counts up or down. During count up operation, pin 7 of IC2 outputs an active low pulse on reaching the ninth count. Similarly, during count-down operation, you again get a low-going pulse at pin 7. This terminal count output from pin 7, after inversion by gate N3, is connected to clock pin 14 of decade counter IC3 (CD4017) which is configured here as a toggle flip-flop by returning its Q2 output at pin 4 to reset pin 15. Thus output at pin 3 of IC3 goes to logic 1 and logic 0 state alternately at each terminal count of IC2. Initially, pin 3 (Q0) of IC3 is high and the counter is in count-up state. On reaching ninth count, pin 3 of IC3 goes low and as a result IC2 starts counting down. When the counter reaches 0 count, Q2 output of IC3 momentarily goes high to reset it, thus taking pin 3 to logic 1 state, and the cycle repeats. The BCD output of IC2 is connected to 1-of-10 decoder CD4028 (IC4). During count-up operation of IC2, the outputs of IC4 go logic high sequentially from Q0 to Q9 and thus trigger the triacs and lighting bulbs 1 through 10, one after the other. Thereafter, during count-down operation of IC2, the bulbs light in the reverse order, presenting a wonderful visual effect
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Circuit Light Flasher Schematics

This is a very basic circuit for flashing one or more LEDS and also to

alternately flash one or more LEDs.
It uses a 555 timer setup as an astable multivibrator with a variable

With the preset at its max. the flashing rate of the LED is about 1/2 a second.

It can be increased by increasing the value of the capacitor from 10uF to a

higher value. For example if it is increased to 22uF the flashing rate becomes

1 second.

There is also provision to convert it into an alternating flasher. You just

have to connect a LED and a 330ohm as shown in Fig.2 to the points X and Y of

Fig.1. Then both the LEDs flash alternately.
Since the 555 can supply or sink in upto 200mA of current, you can connect upto

about 18 LEDS in parallel both for the flasher and alternating flasher (that

makes a total of 36 LEDs for alternating flasher).
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Schematic Diagram Fixing a Mouse Double Click Problems

Have you ever experience a bad optical mouse? It went double click action whenever you did a single click action? At first, I try to Google for answer but none of them help. I’ve tried every combination of settings but the problem doesn’t go away. I really suspected there must be something wrong with the circuit. After I made a conclusion that it is a mechanical related issue (maybe the switch it self), I replace the switch from an old mouse available.

Unfortunately the problem is still there. This is dangerous since you might drag a folder by accident and move it into another folder. This problem always happening to a first time touch-pad user with tapping function turned on.

So next I’m thinking it maybe related to a noise in the circuit. So without any calculation, I try to salvage a capacitor that l can find from an old circuit board and solder it parallel to the switch.

:-) Now it become “click and hold” for about 10 seconds. The capacitor value that I used to smooth the noise from the circuit is too big causing it to simulate “click and hold”. After measuring the capacitance it shows about 2µF. Too big maybe.

Next I try to find a capacitor with quite smaller capacitance value (~2nF). Maybe this will do. So I just replace it.

Walla! At last like a brand new mouse looks and feel. Good luck.
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Schematic Diagram L293D Sebagai Driver Motor

IC driver L293D merupakan H-bridge driver dengan kemampuan yang jauh lebih unggul dibandingkan H bridge biasa (terbuat dari transistor yang dirangkai menjadi H-bridge). Kelebihan itu antara lain:
1. lebih mudah pembuatannya
2. mampu menangani 2 motor
3. arus dan tegangannya relatif lebih besar daripada transistor
berikut adalah gambar datasheetnya;

gambar berikut adalah salah satu contoh design untuk mikrokontroler

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Schematics 25W Power Amplifier based IC LM1875

Short circuit protection, 94dB supply rejection ratio, thermal protection, S/N ratio in excess of 100dB, Open loop gain typically 90dB and 70mA quiescent current, LM1875 is great enough to give you good audio performmance. This power IC will amplify the audio signal up to 30W output power.

25W Power Amplifier based IC LM1875

Component part list

R1 _____________ 1K
R2 _____________ 1M
R3 _____________ 22K
R4 _____________ 10K
R5 _____________ 180K
R6 _____________ 1R

IC1 ____________ LM1875
C1 _____________ 1uF 50V
C2,6 ___________ 100nF
C3 _____________ 22uF 63V
C4 _____________ 0.22uF
C7,5 ___________ 220uF 50V

Fuse holder & cover
2 amp fuses

Visit this 25W Power Amplifier page for detail explanation
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Circuit 5 band graphic equalizer using a single IC/chip Schematics

This circuit uses a single chip, IC BA3812L for realizing a 5 band graphic equalizer for use in hi-fi audio systems. The BA3812L is a five-point graphic equalizer that has all the required functions integrated onto one IC. The IC is comprised of the five tone control circuits and input and output buffer amplifiers. The BA3812L features low distortion, low noise, and wide dynamic range, and is an ideal choice for Hi-Fi stereo applica-tions. It also has a wide operating voltage range (3.5V to 16V), which means that it can be adapted for use with most types of stereo equipment.

The five center frequencies are independently set using external capacitors, and as the output stage buffer amplifier and tone control section are independent circuits, fine control over a part of the frequency bandwidth is possible, By using two BA3812Ls, it is possible to construct a 10-point graphic equalizer. The amount of boost and cut can be set by external components.

The recommended power supply is 8V, but the circuit should work for a supply of 9V also. The maximum voltage limit is 16V.

The circuit given in the diagram operates around the five frequency bands:

  • 100Hz
  • 300Hz
  • 1kHz
  • 3kHz
  • 10kHz
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Schematics Digital Sound Level Meter

This circuit is a digital sound level meter with a LCD screen, capable of displaying 80 characters (4 rows with 20 characters on each). You can build this LCD display. It also provides more debugging information, such as the minimum and maximum analog-to-digital samples that were measured during each period.

Analog Amplifier Circuit
This is a simple model for the NPN bipolar junction transistor (BJT), biasing, how to calculate gain, and adding more gain at higher frequenies with a technique called "bypassing".

In the sound meter schematic, the 100K potentiometer is adjusted until the transistor's collector current is approximately 100 microamps (10-4 amps). This is measured with a voltmeter across RE until the voltage is approximately 0.33 volts. Please watch the video for a full explanation of the transistor model and how we build up to this circuit.

Source Code
Microcontroller are based around an Atmel ATmega168 series microcontroller (MCU). These are powerful, industrial grade MCUs, and we help you build a full system around them. This microcontroller has a CPU, permanent storage (flash memory), temporary storage (static RAM), and inputs and outputs.

You can download the source code here. Start with the standard NerdKits microcontroller project and Makefile (included with the kit) and plug in this source code.

Source: Piezoelectric Sound Meter
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