Simple Auto Turn Off Battery Charger Circuit Diagram

This Auto Turn-Off Battery Charger Circuit Diagram for series-connected 4-cell AA batteries automatically disconnects from mains to stop charging when the batteries are fully charged. It can be used to charge partially discharged cells as well. The circuit is simple and can be divided into AC-to-DC converter, relay driver and charging sections. In the AC-to-DC converter section, transformer X1 steps down mains 230V AC to 9V AC at 750 mA, which is rectified by a full-wave rectifier comprising diodes D1 through D4 and filtered by capacitor C1. Regulator IC LM317 (IC1) provides the required 12V DC charging voltage.



 Auto Turn-Off Battery Charger Circuit Diagram

When you press switch S1 momentarily, the charger starts operating and the power-on LED1 glows to indicate that the charger is ‘on.’ The relay driver section uses pnp transistors T1, T2 and T3 (each BC558) to energise electromagnetic relay RL1. Relay RL1 is connected to the collector of transistor T1. Transistor T1 is driven by pnp transistor T2, which, in turn, is driven by pnp transistor T3. Resistor R4 (10-ohm, 0.5W) is connected between the emitter and base of transistor T3.

When a current of over 65 mA flows through the 12V line, it causes a voltage drop of about 650 mV across resistor R4 to drive transistor T3 and cut off transistor T2. This, in turn, turns transistor T1 ‘on’ to energise relay RL1.


Now even if the pushbutton is released, mains is still available to the primary of the transformer through its normally open (N/O) contacts.  In the charging section, regulator IC1 is biased to give about 7.35V. Preset VR1 is used for adjusting the bias voltage. Diode D6 connected between the output of IC1 and battery limits the output voltage to about 6.7V, which is used for charging the battery.  Pushing switch S1 latches relay RL1 and the battery cells start charging. As the voltage per cell increases beyond 1.3V, the voltage drop across resistor R4 starts decreasing. When it falls below 650 mV, transistor T3 cuts off to drive transistor T2 and, in turn, cuts off transistor T3.


As a result, relay RL1 de-energises to cut off the charger and red LED1 turns off.  You may determine the charging voltage depending on the NiCd cell specifications by the manufacturer. Here, we’ve set the charging voltage at 7.35V for four 1.5V cells. Nowadays, 700mAH cells are available in the market, which can be charged at 70 mA for 10 hours. The open-circuit voltage is about 1.3V. The shut-off voltage point is determined by charging the four cells fully (at 70 mA for 14 hours). After measuring the output voltage, add the diode drop (about 0.65V) and bias LM317 accordingly.

Author : Y.M. Anandavardhana

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Here will introduce a palm size cell phone jammers

The manufacture process and technology of cell phone jammers will be renewed and revised.
To pay a certain amount of calls per month, pay the full two years can have this phone and given 14 days probation period, if you are not satisfied, you can cancel the agreement, returned to the mobile phone network operators. This is our country, "China Mobile and China Unicom launched prepaid calls to send the phone is somewhat similar, the difference is more humane, the foreign service, you can have the 14-day trial period, if you use unhappy, and free exchange within 14 days of the other models, this machine without the network or not, you have the final say. All there is this machine 14 days. The machine fineness of good items fineness of 99 to 100%, all original accessories. The working instruction of cell phone jammers should be renewed too.
14 secret in a foreign country, tried, strictly speaking, not a new machine, it should be said to be filling the new machine; appearance is difficult to identify due to foreign network operators require the phone to fourteen days trial period can not be damaged, it will be net of depreciation expense, so a lot of fourteen days the machine appearance is unable to identify whether the new machine; concrete from several aspects: 1, the packaging is worn; a close look at the phone The charging port and battery with or without scratches headphones and related accessories to be opened too; 3, enter the mobile phone interface to see whether the call records and contacts with or without record. It is the three-antenna wireless signal cell phone jammers .Here will introduce a palm size cell phone jammers
Purchase Note: the 14 secret 14 secret and a new machine purchase price difference of $ 100-200, do not rule out some distribution will take the 14 secret when a new machine for sale, at the time of purchase must be carefully view; not all phones 14 secret, and generally there are 14 secret specific models are as follows: Nokia N-GAGE, Dopod 686, the XDA, the SIEMENS SX65, Dopod 515 (SPV) Sony Ericsson T610, Panasonic GD87, NEC, C616, C313, Motorola A835, a920 models . Trigger is also the last one to two years to appear. The so-called trigger is assembled machine. Outflow from the mobile phone production factory accessories by skilled workers, self-assembly sales. Here will introduce a new type of three antenna wireless signal cell phone jammers .
For example, the past two years the fire of the Sony Ericsson T618, factories located in Beijing, workers tried a variety of ways to take the accessories directly from the pipeline, and then brought back home, assembled, sold to wholesalers. This phone a lot of accessories do not go through quality inspection, so the quality is uneven, and definitely do not recommend the purchase. On one of the phones the difference between parallel and mainstream. First affirmed either parallel or licensed, are regular manufacturers. Parallel does not mean that products mixed with water made a false parallel as counterfeit, counterfeiting, the degree of integration of mobile phone technology is not yet behind to make people imitation, unless it is a OEM product, for example, Kejian and Samsung. Lenovo and LG, Capitel, and Nokia, and so on.  cell phone jammers is recently well received by the customer in the domestic market and oversea market.

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Simple Switching Regulator Converter Circuit Diagram

This is a Simple Switching Regulator Converter Circuit Diagram  . The Max650 switching regulator produces a regulated 5 V from large negative voltages, such as the -48 V found on telephone lines. The resulting power supply operates with several external components, including a transformer, and it delivers 250 mA. The device includes a 140-V 250-mA pnp transistor, short-circuit protection, and all necessary control circuitry.

Simple Switching Regulator Converter Circuit Diagram

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