Charging is accomplished with a constant current of 60 mA for AA cells to a cutoff voltage of 2.4 V per cell at which point the charge must be terminated. The charging system shown is designed for multi-cell battery packs of 2 to 6 series-connected cells or....

This design measures the differential temperature between two sensors. Sensor Tl, located before the heater resistor, assumes the fluid"s temperature before it is heated by the resistor. Sensor TZ picks up the temperature rise induced into the fluid by the....

The laser light detector utilizes a sensitive photo transistor (Q5) placed at the focal point of a lens (LE2). The output of Q5 is fed to a sensitive amplifier consisting of array (Al) and is biased via the voltage divider consisting of R14 and Rl. The base....

This inexpensive dc supply-voltage monitor sounds a warning when the voltage falls below a preset value. It is ideal for monitoring rechargeable batteries since it draws only a few microamperes when not sounding. The voltage at which the alarm sounds is....

The amplifier provides a total power gain of about 25 dB, and the construction technique allows the use of inexpensive components throughout. The MRF476 is specified as a 3 watt device and the MRF475 has an output power of 12 watts. Both are extremely....

This preamplifier has a built-in regeneration control boost gain selectivity. CI is a single or multi-gang AM broadcast-band tuning capacitor. LI is a ferrite loop antenna, tapped at about 15 to 25% of total turns. This circuit should prove useful for....

In a half-duplex system, information can flow in both directions, but only one direction at any given time. The conventional method of building a half-duplex link requires a separate emitter and detector, connected with directional couplers, at each end of....

Lamp II is a household lamp. When the switch is in the center position, the lamp is operated on half-wave rectified ac; the ef..

The amplifier provides 10 dB of gain from 10-600 MHz and has a 1-to-l match at 50 ohms. The BFR91 has a 1 dB noise figures at 500 MHz, The circuit requires 13 Vdc at about 13 mA. Keep the leads on the 150 pF emitter bypass capacitor as short as possible. The....

This circuit utilizes an HA-5152 dual op amp and FET to produce a low-voltage, low-power, Weinbridge sine-wave oscillator. Resistors R and capacitors C control the frequency of oscillation; the FET, used as a voltage-controlled resistor, maintains the gain....

This circuit provides a linear increase of frequency of 10 Hz/°C over 0-100 °C and can thus be used with logic systems, including microprocessors. Temperature probes Ql Vbe changes 2 mV/°C. This transistor is incorporated in a constant current source....

Brief full-power flashes are obtained when the SCR conducts during positive half cycles of the line voltage. The SCR fires when the voltage at the divider, R3 and R4, reaches the gate-firing level. ..

The 741 op amp integrator signal is fed into the Schmitt trigger input of an inverter. When the signal reaches the magnitude of the positive-going threshold voltage, the output of the inverter is switched to zero. The inverter output controls the FET....

A simple level of power meter can be arranged to give a bar or dot display for a hi-fi system. Use green LEDs for 0 to 7; yellow for 8 and red for 9 to indicate peak power. The gain control is provided to enable calibration on the equipment with which the....

This tester can be used to check IC printed circuit boards. Two 4 K resistors and the transistors connected to them prevent current flow through the operational amplifier until the probe circuit is completed..

The probe indicates a high or low at 70% and 30% of V+ (5 to 12 V). One section of the voltage comparator (LM393) senses V in over 70% of supply and the second section senses V in under 30%. These two sections direct-drive the appropriate LEDs. The pulse....

Latching is obtained by storing the gate trigger energy from the preceding half cycle in the capacitors. Powe..

The gate drive that phase controls the four parallel SCRs is accomplished with complementary MOS hex gate MC14572 and two bipolar transistors. This adjustable line-synchronized driver pennits SCR conduction from near zero to 180 degrees. A Schmitt trigger....

This circuit furnishes an initial voltage of 2.5 V per cell at 25° C 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....

A1 and its associated components furnish an amplitude stable sine wave source. All positive feedback path is a Wein bridge, tuned for 1.5 kHz, Ql, the LT1004 reference, and additional components in Al's negative loop unity-gain stabilize the amplifier. Al's....

The two probes shown are held in the hands and the skin resistance applies bias to the transistor. The 5 k ohm pot is set for zero deflection on the meter. When the ' 'subject'' is embarrassed or lies, sweating on the hands takes place, increasing the bias....

Each and every time a phone on the same line or calling numberis taken off-hook, the circuit will be activated to control an external electronic circuit. If several extension telephones are used on one phone line, the circuit can be useful as a busy....

With both the ignition and the car lights on, piezo transducer BZl draws no current and remains silent. With only the ignition on, diode Dl is reverse-biased and so prevents current flow through BZL. However, when the lights are on and the ignition is....

The circuit is based on the grid-dip or absorption effect, which occurs when a parallel resonant circuit is coupled to an oscillator of tbe same frequency. Ql operates in a conventional Colpitts oscillator circuit at a fixed frequency of approximately 4....

The circuit uses CA3290 BiMOS dual voltage comparators. Non-inverting inputs of A1 and A2 are tied to voltage divider reference. The input signal is applied to the inverting inputs. ..

A voltage divider consisting of Rl, R2, and R3 is used to set the input reference voltage below which the batteries are to be replaced. That reference voltage, at point A, is varied by Rl. With the voltage divider shown in Fig. 9-7, a range of 2 to 3.5 Vis....

There are two switches: a memory disable switch and a pulse polarity switch. Memory disable is a push-button that resets the memory to the low state when depressed. Pulse polarity is a toggle switch that selects whether the probe responds to a high-level or....

Here are two FM generators for low frequency, less than 0.5 MHz center frequency, applications. Each uses a 566 function generator as a modulation generator and a second 566 as the carrier generator. Capacitor Cl selects the modulation frequency adjustment....

The circuit is light seeking; it will follow a flashlight around a darkened room. A pair of photocells determine the direction in which the robot will move. Each photocell is connected to an op amp configured as a comparator. When sufficient light falls on....

The circuit is built around two power FETs, which are configured as a simple astable multivibrator to alternately switch the two lamps on and off. The rc values given sets the flash rate to about 1/3 Hz. By varying either the resistor or capacitor....

Up to six lights can be sequentially flashed using this circuit. LED1 through LED6 can be replaced by optocouplers (MOC3010..

Under good battery conditions the LED is off. As the battery voltage falls, the LED begins to flash until, in the low battery condition, the LED lights continuously. Designed for a 9-volt battery, with the values shown the LED flashes from 7.5 to 6.5 volts. ..