Voltmeter Circuits
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This circuit was designed for testing fuel cells, but it could also be used for testing batteries under a constant current load. It provides a dynamic, constant current load, eliminating the need to manually adjust the load to maintain a constant load. For.... -
Continually monitors battery voltage during use and consumes only about 250 ? A (until the end point is reached). Near the end point Trl turns off, allowing Tr2 to illuminate the LED to increase current drain further leading to a distinct turn off point... -
This circuit gives an early warning of the discharge of batteries. Zener diode Dl is chosen for the voltage below which an indication is required (9 V). Should the supply drop to below 7 V, Dl will cease conducting causing Ql to shut off... -
The LM39X4 acts as a LED-driving vol-tometer that has its basic maximum and minimum readings determined by the values of R2 and RV2. When correctly adjusted, the unit actually covers the 2 volt to 3 volt range, but it is made to read a supply voltage span of.... -
A zener diode placed in series with a voltmeter will prevent the meter from reading until the applied voltage exceeds the zener voltage.. -
The sensing circuit rapidly disconnects the battery voltage and load whenever the voltage drops below a preset threshold. One-way operation prevents the circuit from reconnecting the load if the voltage should then rise above the threshold. Cl ensures that.... -
When Sl is depressed, Cl begins to charge to the supply voltage. That places a forward bias on the gate of Ql turning it on and supplying current to load resistor RL. When the charge on Clleaks off, the transistor shuts off, cutting off current to the.... -
If a NiCad battery is discharged to a point at which the lowest capacity cell becomes fully discharged and reverses polarity, that cell will usually short internally and become unusable. To prevent this type of damage, this circuit detects a one-cell drop of.... -
Circuit provides a minimum of 7 V until the 9-V battery voltage falls to less than 2 V. When the battery voltage is above 7 V, the MAX630"s IC pin is low, putting it into the shutdown mode which draws only 10 nA. When the battery voltage falls to 7 V, the.... -
Most of the circuitry is contained in the LM3914 dot/bar-graph driver IC chip. In addition to the comparator circuitry within the package, it also contains a stable reference supply and the drivers for the LEDs. Resistor R2 acts as the current limiter.... -
Because NiCad batteries maintain a constant output voltage, it is difficult to determine how much of the battery"s charge remains. The circuit provides a way of determining the capacity of a battery by draining it at a preset current to its depleted voltage.... -
To prevent battery damage due to over -disc barge, a low-voltage detector and switch should be included in the design of the battery backup circuit. The detector circuit should consume extremely low current. The switch should exlnbit a low-voltage drop and.... -
NiCad batteries are excellent rechargeable power sources for portable equipment, but ~care must be taken to ensure that the batteries are not damaged by overdischarge. Specifically, a NiCad battery should not be discharged to the point where the polarity.... -
The test circuit gives an indication of the capacity remaining in a battery. By noting the time in seconds that the LED remains on after you depress the test switch Sl. The circuit has proven reliable in testing NiCad-, carbon-, and alkaline-type.... -
A common need in many systems is to obtain positive and negative supplies from a single battery. Where current requirements are small, the circuit shown is a simple solution. It provides symmetrical ± output voltages, both equal to one half the input.... -
The battery life and operating cost of an electric vehicle is severely affected by overdischarge of the battery. This circuit provides both warning and shutdown. An electronic switch is placed in series with the propulsion motor contactor coil. Three modes.... -
A tricolor LED, acts as the visual indicator of the voltage level. The voltage to be measured is connected to the two comparators in parallel. The first 20-KO trimmer defines a voltage between ±5 V and this becomes the full-scale value of the reference.... -
Any potential from 1 to 15 V can be monitored with this circuit. Two lamps alert any undesirable variation. The voltage differential from lamp tum-on to tum-off is about 0.2 Vat any setting. High and low set points are independent of each other. The SCRs.... -
This voltmeter exploits a number of tbe CA3160 BiMOS op amp"s useful characteristics. The available voltage ranges from 10 mV to 300 V. Powered by a single 8.4-V mercury battery, this circuit, with zero input, consumes approximately 500 p,A. .. -
This de voltmeter, with high input resistance, uses a CA3130 BiMOS op amp and measures voltages from 10 m V to 300 V. Resistors R12 and Rl4 are used individually to calibrate tbe meter for full:scale deflection. .. -
A2N3819 FETprovides a solid-state VOM. The 2N3819 acts as a cathode follower in a VOM. The bias offset (meter null) is obtained with R14 and R12 sets full-scale calibration. R2 through R9 should total about 10 MO. .. -
This schematic shows a peak-reading diode voltmeter driven by two stages of amplification. A 100-ILF capacitor provides a fairly large time constant, which results in satisfactory meter damping. The limited differential output voltage coupled with an.... -
If the battery voltage exceeds about 11 V, current flows through R1, D1, and R2. The voltage produced as a result of current flow through R2 is sufficient to bias transistor Q1 into conduction. That places the collector voltage of Q1 virtually at.... -
Capacitor C4 couples the output of U1 to a simple attenuator, which is used to provide a loss of 0 dB, 20 dB, or 40 dB, depending on the setting of range switch Sl. The circuits sensitivity is 10-V rms for fullscale deflection, so the attenuator gives.... -
Input terminal VIN is connected to the +V line of tbe circuit that the indicator is to monitor, and the grounds of botb circuits are connected togetber. The position of potentiometer Rl"s wiper determines Q1"s base voltage. As long as the transistor.... -
This circuit uses only one JC, either 1, LM393 dual comparator or 1/z, LM339 quad comparator. RV1 and RV3 set the full scale reference voltage, and RV2 and RV4 set the switching thresholds to a value between 0 V and the full-scale reference. .. -
This circuit will allow a multimeter to display the positive or negative peaks of an incoming signal. A 741, JC1, is used in the noninverting mode with R1 defining the input impedance. D1 or D2 will conduct on a positive or negative peak, charging C2 until.... -
This current source has continuous control of the magnitude and polarity of its amplifier gain and needs only one voltage reference. The circuit includes reference ~, voltage-amplifier circuit A1 with gainsetting resistor Rs, and bootstrap-follower.... -
This circuit shows a simple method of achieving a voltage reference which can be trimmed using an 8bit DAC with an on-chip voltage reference. The analogue output from the DAC drives the trim pin of the ZNREF025 via a resistor, R,. When Rs = 0, this circuit.... -
The voltage to be measured is digitized in an analog-to-digital (A/D) converter and then displayed in three decimal d.. -
The current range in multimeters, particularly the more inexpensive ones, is restricted by the load limits of the internal.. -
This circuit detects brief shorts or opens. When S2 is in the up position, the circuit indicates if there is or..
New Circuits
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This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of.... -
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is.... -
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to.... -
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This.... -
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the.... -
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,.... -
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the.... -
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power.... -
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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