Checker Circuits

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Capacitance multiplier

The circuit can be used to simulate large capacitances using small value components. With the values shown and C - 10 ÂµÂ¥, an effective capacitance of 10,000 ÂµF was obtained. The Q available is limited by the effective series resistance. .
Simple continuity checker

The pitch of the tone is dependent upon the resistance under test. The tester will respond to resistance of hundreds of kilohms, yet it is possible to distinguish differences of just a few tens of ohms in low-resistance circuits. Ql and Q2 form a multivibrator, the frequency of which is influenced by the resistance between the test points. .
Shift register

The shift pulse amplitude is less than 15 volts. If a stage is off, the shift pulse will not be coupled to the next stage. If it is on, the diode will conduct triggering the next stage. Just prior to the shift pulse the anode supply is interrupted to turn off all stages. .
Car Exhaust Meter

Bridge circuit contains two resistors lOO-ohm (R3 and R4), and two thermistors (Tl and T2). At room temperature, the resistance of T1 and 1'2 is about 2000 ohms. When they are each heated to 150 Â° C by an RNA 10 current, the resistance value decreases to 100 ohms. So. the four elements include a bridge circuit. CO is a characteristic that...
Static charge-electricity detector

The detector will sense static charges and free ions in the air. It can be used to indicate the presence of ion emission, high voltage, static electricity, and electrostatic fields. The ground can be an earth ground or a touching metal by your hand. .
Battery status indicator circuit diagram

741 op amp can be used as a voltage comparator. Non-inverting input and a zener control source. The reference voltage is 5.1V. R2 can adjust the in-phase input voltage becomes .
The power indicator circuit

ACER PM02 MP4 machine shows voltage status indicator circuit, when there is power red LED lights when entering the work, the green LED lights. .
Used in conjunction with multimeters FET Vp Vas checker

Chen is in the OP put too amplifying circuit, so that the comb over current feedback loop with input resistance determined current roll, so FET drain current, a gate by the det .
Clamp-on-current probe compensator

A clamp-on "current probe" such as the Tektronix P6021 is a useful means of displaying current waveforms on an oscilloscope. Unfortunately, the low-frequency response is somewhat limited, as shown in the Table. The more sensitive range on the P6021 is 2 mA/mV, but it has a roll-off of 6 dB per octave below 450 Hz. The compensator counteracts the... .
Build your own bypass-capacitor tester

The circuit in Figure 1 tests these characteristics. It charges the capacitor under test through 100 k for approximately 1 msec and then discharges it through 10 for approximately 40 nsec. The cycle then repeats. The circuit uses a double-sided copper-clad pc board. All the components except the 10 resistor connect to one side of the board, so...
Schottky Field Strength Meter

When an antenna is attached, (or even if not, in the presence of a strong RF field) the field strength meter has a moving coil meter to indicate relative field strength. The box holds a Schottky diode detector, a DC amplifier, and a meter display. If the parts used in construction are the same values shown in the schematic, the meter shows full... .
Clock multiplier circumvents PLL

Using a standard PLL circuit, such as the CMOS 4046B with some passive components, is a well-known way to design a clock multiplier. Unfortunately, using a PLL in a digital circuit has two disadvantages: It takes a long time for the circuit to reach a stable output frequency, and the frequency-drift compensation has a complex design.
Simple Transistor Tester

This is basically a high gain amplifier with feedback that causes the LED to flash at a rate determined by the 10u and 330k resistor. Remove one of the transistors and insert the unknown transistor. When it is NPN with the pins as shown in the photo, the LED will flash. To turn the unit off, remove one of the transistors. .
LED Crystal Tester

Transistor Q1, a 2N3563, and its associated components form an oscillator circuit that will oscillate if, and only if, a good crystal is connected to the test clips. The output from the oscillator is then rectified by the 1N4148 signal diode and filtered by C3, a 100pF capacitor. The positive voltage developed across the capacitor is applied to... .
Inductance adapter for frequency meter

The following circuit enables me to measure inductance of the inductor labeled LX which is the inductance to be measured. The o/p of the circuit is a TTL square wave whose frequency relates to the inductance being measured. The heart of the circuit is the buffer colpitts oscillator(the first stage) which resonates with the unknown inductance to... .
RF probes

An RF probe is used to directly measure the level of RF voltage present at a particular point and is one of the most useful test instrument in the hands of the home brewer. It is normally used with a digital multi meter to indicate the voltage level as dc voltage which is equivalent to the RMS value of the RF voltage being measured. However, the... .
Scope Probe Adapter

The capacitance between the wire and the probe would form a capacitive voltage divider with the probe's input capacitance, and at frequencies significantly higher than the low frequency roll off created by the probe's input capacitance and the probe's resistance, the wave form would be faithfully reproduced, although it would have a reduced... .
MOSFET Tester circuit

This is a variation on the astable multivibrator. Circuit was recently developed to test for N-mosfets(the power kind e.g irf830). I don?t claim circuit can test all bad mosfets or all fault mosfet conditions. If mosfet is working it will operate in the astable multivibrator circuit causing the Led to flash. A bad mosfet will not cause the LED... .
Simple Digital Potentiometer with DS1869

The experimenter's pot is a solid state potentiometer using Dallas semiconductor?s DS1869 and National?s LM78L05 two electrolytic capacitor two small push button switch and two optional Molex connector. this project is very useful especially in finding the right value of resistor in your experiments, you can attach this circuit to your next... .
Oscilloscope AC Probe

The probe described here was designed to be used over the range of several tens of Hz to a couple MHz with currents from a few tens of milliamps to about 10 amps peak-to-peak. Formulae are give which will allow you to create a design suitable for your own applications. To use this probe, a wire is connected in series with the load that you want... .
µCurrent Adaptor for multimeters

The µCurrent is in many cases also able to improve upon your meters current range accuracy by using your meters more accurate mVDC or mVAC voltage ranges instead to display the DC or AC current. With AC the frequency response extends flat up to 10KHz, but THD increases substantially above 2KHz. Still a very respectable AC response range,... .
1 Khz Inductance Meter ATTINY861

1 kHz is a commonly used test frequency, and I resolved to see if I could make an inductance meter that uses a 1 kHz test signal at a low level. I also wanted to use a low level test signal so that the test current would have a minimal effect on the measurement. Magnetic cores, and soft ferrites in particular, change in permeability as a... .
16-300 MHz Testing Colpitts oscillator

The circuit is a modified Colpitts oscillator, tuned with MV209 varactor diodes. The resonating inductor and the drain choke are selected by a rotary switch. 1N5711 Schottky diode, D, clamps the maximum positive voltage on the gate of oscillator FET, Q1 to just above ground to reduce the distortion in the wave form on the gate of Q1. Buffer Q2... .
Negative Resistance Oscillator with Tunnel Diode

This circuit can be easily powered from a 1.5 volt battery. One characteristic of N type negative resistance devices is that they typically require a very low bias source resistance in order to keep the bias voltage stable within the negative resistance region. With too high of bias resistance, the voltage, as it enters the negative resistance... .
220V Mains Quality Monitor

With this circuit you will be able to monitor the quality of the mains. There are 4 distinct sections, each supervising a parameter pertinent to the quality of the supply line. The noise section consists of a 50Hz filter and a speaker where you will hear the noise present on the line. The bicolor LED should be adjusted for the least light with... .
Analogue Tachometer and Dwellmeter

This circuit as first published in Wireless World September 1975 and subsequently in MECRM. It's built around a TTL quad NOR gate, though CMOS could be used. .
Km Counter / meter circuit

This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1 (the least significant digit)... .
Finding an Electrical Short

Over time, many things can cause electrical problems with your Mustang. Components will get old and worn or a wire can rub against something and expose the wire to metal. I have seen where a body shop will inadvertently crimp a wire when they install a body panel. Sometimes, when mechanical repair is done, the wiring just gets in their way. This i .
12V Battery Checker Circuit

This is a 12V battery checker circuit that uses 3 LEDs that light up at their respective voltages. The red LED lights up when the battery voltage is between 8 to 10V, the orange one at voltages between 10. 5V to 12V and the green one when the battery voltage is above 12. 5V. This is a tried and tested battery checker circuit using one NPN and... .
IR Remote-Control Checker

R2_47R 1/4W Resistor D1_LED (Any dimension, shape and color) Q1_Infra-red Photo Transistor (Any cheap type) Q2_BC327 45V 800mA PNP Transistor SW1_SPST Toggle or Slide Switch (Optional, see Note) B1_3V Battery (2 x 1. 5V AA, AAA or smaller type Cells in series) A very simple device allowing a quick check of common Infra-red Remote-Controls can be us .
ADC Tester (A2100)

The ADC Tester (A2100) is a LWDAQ device that records the output and power consumption of two ADC s. Its original purpose was comparative testing of two ADCs at different temperatures, but it turned out that the A2100 makes a good dual-channel eighteen-bit oscilloscope. Figure: ADC Tester (A2100A) with Two LTC1865L Auxilliary Boards. The flex cabl .
BC107 Transistor For 12V Battery Operated Heater Circuit

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