Diagram for Reference

Simple Tone Control specifically designed for the 3 - 5 Watt Class-A audio amplifiers. Traditional Bass, Treble Controls and DC 24V power supply. A Bass and Treble frequency control to be added to the 3 - 5W Class-A Amplifier was required by some audio enthusiasts. Therefore, this circuit has been designed keeping in mind the extreme simplicity of the amplifier circuit to which it should be linked and was carried out using as few as components possible.

Simple Tone Control Circuit Diagram

Parts

P1______________47K Log. Potentiometer (See Notes)
P2,P3___________47K Linear Potentiometers
R1,R3,R5_________4K7 1/4W Resistors
R2______________22K 1/4W Resistor
R4_______________1M 1/4W Resistor
R6_______________1K8 1/4W Resistor
R7_____________560R 1/4W Resistor
C1,C4,C5,C7_____10µF 63V Electrolytic Capacitors (See Notes)
C2______________47nF 63V Polyester Capacitor
C3_______________1nF 63V Polyester Capacitor (See Notes)
C6_____________220µF 35V Electrolytic Capacitor
Q1____________BC550 45V 100mA NPN Low noise High gain NPN Transistor

Q1 is the only active component forming a straightforward single-stage transistor amplifier with the tone control network in the ac feedback path. Taking this feedback from the split load of Q1 we obtain an ac stage gain of about 3: this can be useful to cope with low output voltage audio sources.

The hobby circuit below uses an unusual method to generate about 12,000 volts with about 5uA of current. Two SCRs form two pulse generator circuits. The two SCRs discharge a 0.047uF a 400v capacitor through a xenon lamp trigger coil at 120 times a second. The high voltage pulses produced at the secondary of the trigger coil are rectified using two 6KV damper diodes.


The voltage doubler circuit at the secondary of the trigger coil charges up two high voltage disc capacitors up to about 12KV. Although this circuit can’t produce a lot of current be very careful with it. A 12KV spark can jump about 0.75 of an inch so the electronic circuit needs to be carefully wired with lots of space between components.

The use of solar photovoltaic (PV) energy sources is increasing due to global warming concerns on the one hand, and cost effectiveness on the other. Many engineers involved in power electronics find solar power tempting and then addictive due to the ‘green’ energy concept. The circuit discussed here handles up to 4 amps of current from a solar panel, which equates to about 75 watts of power. A charging algorithm called ‘pulse time modulation’ is introduced in this design. The current flow from the solar panel to the battery is controlled by an N-channel MOSFET, T1. This MOSFET does not require any heat sink to get rid of its heat, as its RD-S(on) rating is just 0.024 Ω.

Schottky diode D1 prevents the battery discharging into the solar panel at night, and also provides reverse polarity protection to the battery. In the schematic, the lines with a sort-of-red highlight indicate potentially higher current paths. The charge controller never draws current from the battery—it is fully powered by the solar panel. At night, the charge controller effectively goes to sleep. In daytime use, as soon as the solar panel produces enough current and voltage, it starts charging the battery. The battery terminal potential is divided by resistor R1 and trimpot P1.

4 Amps Photovoltaic (Solar) Charge Controller Circuit Diagram

The resulting voltage sets the charge state for the controller. The heart of the charge controller is IC1, a type TL431ACZ voltage reference device with an open-collector error amplifier. Here the battery sense voltage is constantly compared to the TL431’s internal reference voltage. As long as the level set on P1 is below the internal reference voltage, IC1 causes the MOSFET to conduct. As the battery begins to take up the charge, its terminal volt- age will increase. When the battery reaches the charge-state set point, the output of IC1 drops low to less than 2 volts and effectively turns off the MOSFET, stopping all current flow into the battery.


With T1 off, LED D2 also goes dark. There is no hysteresis path provided in the regulator IC. Consequently, as soon as the current to the battery stops, the output of IC1 remains low, preventing the MOSFET to conduct further even if the battery voltage drops. Lead-acid bat- tery chemistry demands float charging, so a very simple oscillator is implemented here to take care of this. Our oscillator exploits the negative resistance in transistors—first discovered by Leo Esaki and part of his studies into electron tunneling in solids, awarded with the Nobel Prize for Physics in 1973. In this implementation, a commonplace NPN transistor type 2SC1815 is used.

When the LED goes out, R4 charges a 22-μF capacitor (C1) until the voltage is high enough to cause the emitter-base junction of T2 to avalanche. At that point, the transistor turns on quickly and discharges the capacitor through R5. The voltage drop across R5 is sufficient to actuate T3, which in turn alters the reference voltage setting. Now the MOSFET again tries to charge the battery. As soon as the battery voltage reaches the charged level once more, the process repeats. A 2SC1815 transistor proved to work reliably in this circuit. Other transistors may be more temperamental—we suggest studying Esaki’s laureate work to find out why, but be cautioned that there are Heavy Mathematics Ahead.

As the battery becomes fully charged, the oscillator’s ‘on’ time shortens while the ‘off’ time remains long as determined by the timing components, R4 and C1. In effect, a pulse of current gets sent to the battery that will shorten over time. This charging algorithm may be dubbed Pulse Time Modulation. To adjust the circuit you’ll need a good digital voltmeter and a variable power supply. Adjust the supply to 14.9 V, that’s the 14.3 volts bat- tery setting plus approximately 0.6 volts across the Schottky diode.

Turn the trimpot until at a certain point the LED goes dark, this is the switch point, and the LED will start to flicker. You may have to try this adjustment more than once, as the closer you get the comparator to switch at exactly 14.3 V, the more accurate the charger will be. Disconnect the power supply from the charge controller and you are ready for the solar panel. The 14.3 V setting mentioned here should apply to most sealed and flooded-cell lead-acid batter- ies, but please check and verify the value with the manufacturer. Select the solar panel in such a way that its amps capability is within the safe charging limit of the battery you intend to use.


Resistors:
R1 = 15kΩ
R2,R3 = 3.3kΩ 1% R4 = 2.2MΩ
R5 = 1kΩ
P1 = 5kΩ preset

Capacitors:
C1 = 22μF 25V, radial

Semiconductors:
D1 = MBR1645G (ON Semiconductor) D2 = LED, 5mm
IC1 = TL431ACLP (Texas instruments)
T1 = IRFZ44NPBF (International Rectifier)
T2 = 2SC1815 (Toshiba) (device is marked: C1815)
T3 = BC547

Miscellaneous:
K1,K2 = 2-way PCB terminal block, lead pitch 5mm

Some of you might wonder why a charger is needed at all, to charge a 12 Volt battery from a 12 Volt source! Well, firstly the "12 Volt" source will typically vary anywhere from 11 Volt to 15 Volt, and then a battery needs a controlled charge current and voltage, which cannot result from connecting it directly to a voltage source. The charger described here is intended for charging small 12 Volt lead acid batteries, such as the gelled or AGM batteries of capacities between about 2 and 10 Ah, using a cars electrical system as power source, regardless of whether the car engine is running or not.



I built this charger many years ago, I think I was still in school back then. On request of a reader of my web site, Im publishing it now, despite being a rather crude circuit. It works, it is uncritical to build, and uses only easy-to-find parts, so it has something in its favor. The downside is mainly the low efficiency: This charger wastes about as much power as it puts into the battery. The charger consists of two stages: The first is a capacitive voltage doubler, which uses a 555 timer IC driving a pair of transistors connected as emitter followers, which in turn drive the voltage doubler proper.



The doubler has power resistors built in, which limit the charging current. The second stage is a voltage regulator, using a 7815 regulator IC. Its output is applied to the battery via a diode, which prevents reverse current and also lowers the voltage a bit. The resulting charge voltage is about 14.4V, which is fine for charging a gelled or AGM battery to full charge, but is too high as a trickle charger, so dont leave this charger permanently connected to a battery.

If you would like to do just that, then add a second diode in series with D3! There is a LED connected as a charge indicator. It will light when the charge current is higher than about 150mA. The maximum charge current will be roughly 400mA. There is an auxiliary output, that provides about 20V at no load (depending on input voltage), and comes down as the load increases. I included this for charging 12V, 4Ah NiCd packs, which require just a limited current but not a limited voltage for charging.



Note that if the charge output is short-circuited, the over-current protection of U2 will kick in, but the current is still high enough to damage the diodes, if it lasts. So, dont short the output! If instead you short the auxiliary output, the fuse should blow. I built this charger into a little homemade aluminum sheet enclosure, using dead-bug construction style. Not very tidy, but it works. Note the long leads on the power resistors. They are necessary, because with shorter leads the resistors will unsolder themselves, as they get pretty hot! The transistors and the regulator IC are bolted to the case, which serves as heat sink. The transistors dont heat up very much, but the IC does.

It is the time when the shipment of phone booster has been arranged.
Belonging to the target customers potential consumers in order to turn them into effective customer must understand why the customer needs your product, your product can help customers solve any problem, which needs to be done a lot of market research and customer interviews work, to really understand consumers, to achieve "customer-centric". Compared with similar products, your product to potential customers in what has created a unique value, unique advantages, there must be rational, objective analysis, in order to find the target consumer "non-bought compelling reasons"; If your products are differentiated features, you can communicate the value of your product information with potential customers. The manufacturer can get rid the inappropriate part of the imported technology of phone booster .
They agree with the value of your product, enlarge your advantage, weakening your shortcomings, to "sell ideas" of the realm, in order to sell a higher price; If your product does not have any differences in features, belonging to the popular and dependable, and competitors the product compared to what unique value, can only rely on the lowest price to attract consumers. Each customer inquiry when we have to try to understand clearly the customer via chat and meet with the judge, his right to speak, is the boss or just a messenger? Price: to the price, but also pay attention to skills for their own interests, not to indulge in (if you feel that one up to ask the price, that is asked many home, the price is certainly care about. It is to ensure the good quality, strict parameter, perfect technology and high performance of phone booster .
The best time directly to the reserve price, you can retain customers, this is a very important step to pull). The interests of customers first, that you do and the people that do (you do not know to say goodbye to home in the end to what price, but you at least want to investigate how the market is almost the price is kind of, so as not to report the outrageous.) services: services must be better, do not look to be a single, feeling a bit indifferent, emotions without reservation by phone to convey the past must be enthusiastic, to help customers solve problems, understand the customers questions about the point where the right remedy (to make people feel, your service really let him enjoy, even if you price a little bit higher than the others will leave because of your service). The customer will definitely have high and higher requirements towards quality and performance of phone booster .
Switch on the power supply of phone booster

This Wien bridge oscillator (after Max Wien, 1866–1938) produces a low-distortion sine wave of constant amplitude, from about 15 Hz to 150 kHz. It requires just four opamps and will work off a single 9-volt battery. Also, unlike most Wien bridge oscillators, it does not require a dual-gang potentiometer for tuning. Op amp IC2b provides an artificial ground so that the circuit will operate from a unipolar supply (9 V battery or power pack). IC2a is the main amplifier for the oscillator. The frequency range is divided into four decades by 2-pole, 4-way rotary switch SW1.

Only one arm of the Wien network is varied, but the change in positive feedback that would normally result is compensated for by IC1b, which works to bootstrap R2, thereby changing the negative feedback enough to maintain oscillation. A linear change in the resistance of the tuning pot results in a roughly logarithmic change in frequency. To get a more conventional linear change a log-taper pot is used wired so that rotating the knob anticlockwise causes frequency to increase.


You could use an anti-log pot the other way around if you prefer, but these things are notoriously hard to find. IC1A is an integrator that monitors the amplitude of the output signal and drives an LED (D2). This must be mounted facing the LDR (light dependent resistor) and shielded from ambient light (for example, with a piece of heat-shrink tubing). IC1a is then able to control the gain of IC2a so that oscillation is maintained with minimum distortion.

The maximum output amplitude of the generator is about 2 Vp-p when the LED and LDR are mounted as close as possible. Distortion is less than 0.5 % in the lowest range, and too low for the author to measure in the higher ranges. Any LDR should work, provided its dark resistance is greater than 100 kO. If you do not have an LDR with such high resistance, try increasing R5 until oscillation starts. Breadboarded prototypes of the circuit were built by the author using dual and quad opamp packages, and both work equally well.

Author: Merlin Blencowe (Elektor)

Resistors:
R1,R2,R3,R6,R10,R11 = 10kO
R7 = 100kO
R4,R9,R12 = 100O
R5 = 12kO
R8 = 1kO
P1,P2 = 10kO potentiometer, logarithmic law
R13 = LDR, R(dark) >100kO, e.g. Excelitas Tech type
VT90N1 (Newark/Farnell # 2568243)

Capacitors:
C1,C5 = 1µF solid
C2,C6 = 100nF
C3,C7 = 10nF
C4,C8 = 1nF
C9-C12 = 47µF 16V, electrolytic, radial

Semiconductors:
D1,D2,D3 = 1N4148
D4 = LED, red, 5mm
IC1,IC2 = TL072ACP

Miscellaneous:
SW1 = 2-pole 4-position rotary switch, C&K Compo-
nents type RTAP42S04WFLSS
K1,K2 = PCB terminal block, 5mm pitch

Some cell phone jammer do not own the cooling function or cooling mechanism.
Domestic brand mobile phone companies do not have the core technology, the development of the control of others. The key components needed for the production of the domestic mobile phone baseband chip, RF chip and the underlying software are largely controlled by foreign companies. CDMA mobile phones due to lack of core technology, currently only take a "market for technology" Sino-foreign cooperative way, the development is fully controlled by others. Insufficient international marketing and export capacity is not strong. Domestic brand mobile phone, although in recent years has developed rapidly, but the products are mainly sold in the country, the vast majority did not go to foreign markets. These issues have become important issues constraining the development of the industry urgently to be addressed. Strategic Analysis of Japanese and Korean mobile phone manufacturer. Some cell phone jammer have the built-in cooling mechanism.
Domestic mobile phone manufacturers in the fashion of the prominent mobile phone design personalized features, price triggered a round of Diving Emergency perspective of Japanese and Korean mobile phone market strategy, we can say, not without reference to the domestic mobile phone manufacturers. Beijing in the enterprise market research study shows that personalized products lead the fashion to become the holy grail of Japanese and Korean manufacturers, especially MMS, color screen and camera phones. Made mobile phones to launch a rapid offensive in the price for the Pioneer, and triggered a collective "diving" of the mobile phone market, some foreign brands face the surging wave of price cuts had to fight with shine, Samsung, LG, Panasonic, NEC, Kyocera many days, the Korean brand in the Chinese market, has recently been the bright spot, have to be very impressive. Some cell phone jammer has the cooling fan.
Japanese and Korean mobile phone the way to win. European and American firms long-term leading the consumption trend of Chinas mobile phone market, so they bring in every shape design innovations have attracted many consumers to follow and favor. In fact, Japan and South Korea series of brand mobile phones in innovative design and personalized applications on the Ling-hui, to some extent higher than the European and American firms, just because they did not occupy the mainstream market, coupled with some manufacturers are not synchronized in China to promote the newly developed products , so can not give full play to their advantage. Faced with the enormous pressure of the American and European brands and domestic brands powerful offensive. Some cell phone jammer have some special cooling design.Japanese and Korean brand mobile phone manufacturers are not willing to supplement, the only market to continue to increase efforts to research and development of new products and push the new speed, began to clash with European and American brands. At the same time, Samsung also introduced a built-in rotating camera phone products to the China market.

As a guide, a one-inch reed switch with 40 turns reliably switched on with the current flowing through a 150-watt lamp (approx. 625 mA) but larger reeds may require more turns. If the master appliance draws less current (which is unlikely with power tools) more turns will be required. The reed switch is used to switch on transistor T1 which in turn switches the relay RE1 and powers the slave appliance. Since reed switches have a low mechanical inertia, they have little difficulty in following the fluctuations of the magnetic field due to the alternating current in the coil and this means that they will switch on and off at 100 Hz.


C3 is therefore fitted to slow down the transistor response and keep the relay energised during the mains zero crossings when the current drawn by the appliance falls to zero and the reed switch opens. C1 drops the mains voltage to about 15 V (determined by zener diode D1) and this is rectified and smoothed by D2 and C2 to provide a d.c. supply for the circuit. The relay contacts should be rated to switch the intended appliance (vacuum cleaner) and the coil should have a minimum coil resistance of 400 R as the simple d.c. supply can only provide a limited current. C1 drops virtually the full mains voltage and should therefore be a n X2-class component with a voltage rating of at least 250V a.c.

Warning:
The circuit is by its nature connected directly to the mains supply. Great care should therefore be taken in its construction and the circuit should be enclosed in a plastic or earthed metal box with mains sockets fitted for the master and slave appliances.

The LP2951 regulator is manufactured by National Semiconductors. The choice of values is from an application note "Battery Charging", written by Chester Simpson. Diode D1 can be any diode from the 1N00x series, whichever is conveniently available. It functions as a blocking diode, to prevent a back flow of current from the battery into the LP2951 when the input voltage is disconnected. Charging current is about 100+mA, which is the internally-limited maximum current of the LP2951. For those wondering, this is compatible with just about any single-cell li-ion battery since li-ion can generally accept a charging current of up to about 1c (i.e. charging current in mA equivalent to their capacity in mAh, so a 1100mAh li-ion cell can be charged at up to 1100mA and so on).

Circuit diagram:

 Li-Ion Battery Charger Circuit diagram

A lower charging current just brings about a correspondingly longer charge time. IMHO 100mA is quite low, low enough that the circuit can be used for an overnight charger for many typical single-cell li-ion batteries. The resistors are deliberately kept at large orders of magnitude (tens/hundred Kohm and Mohm range) to keep the off-state current as low as possible, at about 2?A. Resistor tolerances should be kept at 1% for output voltage accuracy. The 50k pot allows for an output voltage range between 4.08V to 4.26V - thus allowing calibration as well as a choice between a charging voltage of 4.1V or 4.2V depending on the cell to be charged. The capacitors are for stability, especially C2 which prevents the output from ringing/oscillating.

Parts
IC1 = LP2951, voltage regulator
D1 = 1N4002, General purpose diode
R1 = 2M, 1%, metal-film
R2 = 806K, 1%, metal-film
P1 = 50K, potentiometer
C1 = 0.1uF, polyester
C2 = 2.2uF/16V, electrolytic
C3 = 330pF, ceramic

Source :www.extremecircuits.net

This automatic door opener can be made using readily available components. The electromagnetic relay at the output of this gadget can be used to control the DC/AC door-opener motor/solenoid of an electromechanical door opener assembly, with slight intervention in its electrical wiring. A laser diode (LED1) is used here as the light transmitter. Alternatively, you can use any available laser pointer. The combination of resistor R1 and diode D1 protects the laser diode from over-current flow. By varying multi-turn trimpot VR1, you can adjust the sensitivity. (Note that ambient light reflections may slightly degrade the performance of this unit.) Initially, when the laser beam is falling on photo-transistor T1, it conducts to reverse-bias transistor T3 and the input to the first gate (N1) of IC1 (CD4001) is low.

The high output at pin 3 of gate N1 forward biases the LED-driver transistor (T4) and the green standby LED (LED2) lights up continuously. The rest of the circuit remains in standby state. When someone interrupts the laser beam, photo-transistor T1 stops conducting and transistor T3 becomes forward-biased. This makes the output of gate N1 go low. Thus LED-driver transistor T4 becomes reverse-biased and LED2 stops glowing. At the same time, the low output of gate N1 makes the output of N2 high. Instantly, this high level at pin 4 of gate N2 triggers the monostable multivibrator built around the remaining two gates of IC1 (N3 and N4). Values of resistor R8 and capacitor C1 determine the time period of the monostable.

The second monostable built around IC2 (CD4538) is enabled by the high-going pulse at its input pin 12 through the output of gate N4 of the first monostable when the laser beam is interrupted. As a result, relay RL1 energizes and the door-opener motor starts operating. LED3 glows to indicate that the door-opener motor is getting the supply. At the same time, piezo-buzzer PZ1 sounds an alert. Transistor T5, whose base is connected to Q output (pin 10) of IC2, is used for driving the relay. Transistor T6, whose base is connected to Q output of IC2, is used for driving the intermittent piezo-buzzer. ‘On’ time of relay RL1 can be adjusted by varying trimpot VR2. Resistor R9, variable resistor VR2 and capacitor C3 decide the time period of the second monostable and through it on time of RL1.

The circuit works off 12V DC power supply. Assemble it on a general-purpose PCB. After construction, mount the laser diode and the photo-transistor on opposite sides of the door-frame and align them such that the light beam from the laser diode falls on the photo-transistor directly. The motor connected to the pole of relay contacts is the one used in electromechanical door-opener assembly. If you want to use a DC motor, replace mains AC connection with a DC power supply.

Ic (constant current) is charge capacitor C, where Ic = Vsc/R.

The output reaches its nominal value after the time ton. Vo-Vsc=(Ic.ton)/C.

ton=C.[(Vo-0.45)/0.45].R = CVoR/0.45.

Vo follows the voltage in pin 2 at less than 0.45 volt. It is because voltage of more than 0.45 V can’t be produced between pin 2 and pin 5.

The compact, low-cost condenser mic audio amplifier described here provides good-quality audio of 0.5 watts at 4.5 volts. It can be used as part of intercoms, walkie-talkies, low-power transmitters, and packet radio receivers. Transistors T1 and T2 form the mic preamplifier. Resistor R1 provides the necessary bias for the condenser mic while preset VR1 functions as gain control for varying its gain. In order to increase the audio power, the low-level audio output from the preamplifier stage is coupled via coupling capacitor C7 to the audio power amplifier built around BEL1895 IC.


BEL1895 is a monolithic audio power amplifier IC designed specifically for sensitive AM radio applications that delivers 1 watt into 4 ohms at 6V power supply voltage. It exhibits low distortion and noise and operates over 3V-9V supply voltage, which makes it ideal for battery operation. A turn-on pop reduction circuit prevents thud when the power supply is switched on. Coupling capacitor C7 determines low-frequency response of the amplifier. Capacitor C9 acts as the ripple-rejection filter.

Capacitor C13 couples the output available at pin 1 to the loudspeaker. R15-C13 combination acts as the damping circuit for output oscillations. Capacitor C12 provides the boot strapping function. This circuit is suitable for low-power HAM radio transmitters to supply the necessary audio power for modulation. With simple modifications it can also be used in intercom circuits.

Phonographs are gradually becoming a rarity. Most of them have had to yield to more advanced systems, such as CD players and recorders or (portable) MiniDisc player/recorders. This trend is recognized by manufacturers of audio installations, which means that the traditional phono input is missing on increasingly more systems. Hi-fi enthusiasts who want make digital versions of their existing collections of phonograph records on a CD or MD, discover that it is no longer possible to connect a phonograph to the system.

However, with a limited amount of circuitry, it is possible to adapt the line input of a modern amplifier or recorder so that it can handle the low-level signals generated by the magnetodynamic cartridge of a phonograph. Of course, the circuit has to provide the well-known RIAA correction that must be used with these cartridges. The preamplifier shown here performs the job using only one opamp, four resistors and four capacitors. For a stereo version, you will naturally need two of everything. Any stabilized power supply that can deliver ±15V can be used as a power source.

Chances are youll want this amplifier portable. Batteries do the trick fine, but you wont get much power out of a couple of 1.5V cells. Unfortunately the size of a decent amount of battery power will mean that the overall size of this amp will be much bigger and for that there are more benefits to be had using a device like the TDA7052 or TDA2822 for stereo.

Quick ref data of TDA1015T Chip

•     Supply voltage range: 3,6 to 12 V
•     Peak output current: 1 A
•     Output power: 0,5 W
•     Voltage gain power amplifier: 29 dB
•     Voltage gain preamplifier: 23 dB
•     Total quiescent current: 22 mA
•     Operating ambient temperature range: -25 to +150 °C
•     Storage temperature range: -55 to + 150 °C

This handy circuit can be used to charge from one to 12 NiCd cells from a car battery. Up to six cells can be charged with switch S1 in the "normal" position. The LM317regulator operates as a simple current source, providing about 530mA when R1 = 2.35O (two 4.7O resistors in parallel). For more than six cells, S1 is set to the "boost" position. This applies powers to IC1, a 10W (or 20W) audio power amplifier. Positive feedback from its output (pin 4) to non-inverting input (pin 1) causes IC1 to act as a square wave oscillator. This square wave signal is coupled to the junction of Schottky diodes D1 and D2 via a 330µF capacitor, forming a conventional charge-pump voltage doubler. Over 20V (unloaded) appears at the input to REG1 - enough to charge a maximum of 12 cells!

This circuit enables any infrared (IR) remote control to control the outputs of a 4017 decade counter. Its quite simple really and uses a 3-terminal IR receiver (IRD1) to pick up infrared signals from the transmitter. IRD1s output is then coupled to NPN transistor Q1 via a 220nF capacitor. Transistor Q1 functions as a common-emitter amplifier with a gain of about 20, as set by the ratio of its 10kO collector resistor to its 470O emitter resistor. Q1 in turn triggers IC1, a 4047 monostable which in turn clocks a 4017 decade counter (IC2).


Basically, IC1 provides a clock pulse to IC2 each time a remote control button is pressed. If you dont wish to use all 10 outputs from IC2, simply connect the first unused output to pin 15 (MR). In this case, only the first four outputs (O0-O3) of the counter are used and so the O4 output is connected to pin 15 to reset the counter on the fifth button press. Power for the circuit is derived from the mains via a transformer and bridge rectifier which produces about 15-27V DC. This is then fed to 3-terminal regulators REG1 & REG2 to derive +12V and +5V supply rails.

A low resistance ( 0.25 - 4 ohm) continuity tester for checking soldered joints and connections.

This simple circuit uses a 741 op-amp in differential mode as a continuity tester. The voltage difference between the non-inverting and inverting inputs is amplified by the full open loop gain of the op-amp. Ignore the 470k and the 10k control for the moment, and look at the input of the op-amp. If the resistors were perfectly matched, then the voltage difference would be zero and output zero. However the use of the 470k and 10k control allows a small potential difference to be applied across the op-amp inputs and upset the balance of the circuit. This is amplified causing the op-amp output to swing to full supply voltage and light the LEDs.

Setting Up and Testing:

The probes should first be connected to a resistor of value between 0.22 ohm and 4ohm. The control is adjusted until the LEDs just light with the resistance across the probes. The resistor should then be removed and probes short circuited, the LEDs should go out. As the low resistance value is extremely low, it is important that the probes, (whether crocodile clips or needles etc) be kept clean, otherwise dirt can increase contact resistance and cause the circuit to mis-operate. The circuit should also work with a MOSFET type op-amp such as CA3130, CA3140, and JFET types, e.g. LF351. If the lEDs will not extinguish then a 10k preset should be wired across the offset null terminals, pins 1 and 5, the wiper of the control being connected to the negative battery terminal.

The above pictured schematic diagram is just a standard constant current model with a added current limiter, consisting of Q1, R1, and R4. The moment too much current is flowing biases Q1 and drops the output voltage. The output voltage is: 1.2 x (P1+R2+R3)/R3 volt. Current limiting kicks in when the current is about 0.6/R1 amp. For a 6-volt battery which requires fast-charging, the charge voltage is 3 x 2.45 = 7.35 V. (3 cells at 2.45v per cell).

So the total value for R2 + P1 is then about 585 ohm. For a 12 V battery the value for R2 + P1 is then about 1290 ohm. For this power supply to work efficiently, the input voltage has to be a minimum of 3V higher than the output voltage. P1 is a standard trimmer potentiometer of sufficient watt for your application. The LM317 must be cooled on a sufficient (large) coolrib. Q1 (BC140) can be replaced with a NTE128 or the older ECG128 (same company). Except as a charger, this circuit can also be used as a regular power supply.

 

 

Parts List:

R1 = 0.56 Ohm, 5W, WW
R2 = 470 Ohm C2 = 220nF
R3 = 120 Ohm
R4 = 100 Ohm
C1 = 1000uF/63V
Q1 = BC140
Q2 = LM317, Adj. Volt Reg.
C3 = 220nF (On large coolrib!)
P1 = 220 Ohm

Source : www.extremecircuits.net

The continuity tester can distinguish between high-, medium-, and low-resistance connections. When there is a conductance between the inputs, which are linked to small probes, a current flows from the +9 V line to earth via R1 and R2. The consequent potential difference, p.d., across R2 is used to determine the transfer resistance. Operational amplifier IC1c amplifies the p.d. across R2 to a degree that is set with P1. A window comparator, IC1a and IC1b, likens the output of IC1c to the two levels set with potential divider R4–R6. Depending on the state of the outputs of the two comparators, three light-emitting diodes (LEDs) are driven via the gates and inverters contained in IC3 and IC2 respectively in such a way that they indicate the transfer resistance in three categories.

When the resistance is high, green diode D3 lights; when it is of medium value, yellow diode D2 lights, and when it is low, red diode D1 lights. The levels at which the diodes light is set with P1, but note that in any case the minimum value depends on the p.d. across R2. It is possible to reduce the value of the p.d. to enable lower transfer resistances to be detected, but this would mean an increase in the test current through R2. With values as specified, the circuit in its quiescent state draws a current of about 17 mA, but in operation each LED adds about 10 mA to this. The LM324 (IC1) may be operated from a single supply line: R1 prevents the voltage at the input from reaching the level of the supply line (which is not permissible). The supply voltage may be 5–18 V. The LEDs are driven directly by the inverters in the 4049 (IC2), which can switch currents of up to 20mA to earth.

5 to 15V supply - LED indicator Adjustable time detection

A circuit capable of detecting even a very short power outage, can be useful, mainly if embedded into existing appliances like mains powered counters, timers, clocks and the like.

At switch-on of the appliance, the LED illuminates, but pressing on P1 it goes off and remains in this state until a power outage occurs. When power supply is restored, the LED illuminates steadily until you press P1 again.

The circuit sensitivity can be adjusted by Trimmer R5. This means that, under the control of R5, the LED may not light if the mains is missing for a short interval in the 1 to 15 seconds range.

Circuit Diagram :

 Power Outage Warning Circuit Diagram

Circuit Operation :

IC1A and IC1B NAND gates are wired as a set-reset flip-flop. R1 and C1 provide auto-set of the flip-flop when the circuit is powered, so pin 3 of IC1A goes high and pin 4 of IC1B goes low. This allows the outputs of IC1C and IC1D, wired in parallel as inverters, to go high driving the LED D1 on. The flip-flop is reset by pushing on P1.

As the circuit is intended to be powered from the same appliance that is monitoring, the supply is derived from the ac voltage available at the existing transformer secondary winding (see the upper box of the circuit diagram enclosed in the dashed blue line). The circuit will work with ac voltage values in the 5 - 15V range.

A simple diode-capacitor cell (D2-C2) is sufficient to provide the necessary dc voltage. A rather low value was chosen for C2 in order to allow the circuit to detect very short periods of power failure.

The resistance value of R4 + R5 controls the discharge time of C2: with R5 set to the minimum value, the circuit will signal power outages from 1 sec. onwards. If R5 is set to the maximum, the circuit will signal power outages from about 15 sec. onwards.

Notes :

• R3 value should be reduced accordingly if the transformers secondary ac voltage is below 10V
• The circuit can be constructed as an independent unit by simply adding a small transformer with a primary winding suited to the local mains voltage and a secondary winding rated from 5 to 15V AC.

Source :www.redcircuits.com