Lead-acid battery charger
This circuit delivers an initial voltage of 2.5V per cell to rapidly charge a battery. The charging current decreases as the battery charges and when the current drops to 180 mA the charging circuit reduces the output voltage to 2.35 V per cell, leaving the battery in a fully charged state. This lower voltage prevents the battery from overcharching, which will shorten its life.
The LM301A compares the voltage drop across R1 with a 18 mV reference set by R2. The comparator’s output controls the voltage regulator, forcing it to produce the lower float voltage when the battery-charging current, passing through R1, drops bellow 180 mA.
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Radio beacon 2m 144 MHz
The transmitter on 2 meters 144 MHz was designed mainly for use by radio amateurs as radio beacon and to this end, it produces a signal of good quality and without unwanted harmonics. T1 transistor, in association with cristall X1, works as oscillator on 36 MHz. L1-C3 filter eliminates any tendency of the circuit oscillation on 12MHz (fundamental frequency of the crystal).
L2-C4 circuit is tuned on the fourth harmonic of oscillator signal (144 MHz). This signal reaches the antenna after passing through a buffer consisting of T2, a FET with 2 gates. The signal modulator (amplitude) is applied to the second gate of the buffer.
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Portable NiCd battery charger
The portable batteries charger has been designed to provide an opportunity to load NiCd batteries even in the outdoors from a 12 V battery of a vehicle. When the circuit is connected to the vehicle battery, D2 lights only if NiCd battery was connected with the correct polarity. Since even on the discarded batteries we have a certain tension, T1 opens and D2 flashes.
As the NiCd battery starts to charge, thru R and D6, lights D6. In the meantime C4 is slowly loading thru P1 and R4. The value of these components determines IC2 monostable period and thus loading time of the NiCd battery. For the components values shown in the schematic, this period can be
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