Infra-red Remote Control Tester

As I was developing my IR Extender Circuit, I needed to find a way of measuring the relative intensities of different Infra red light sources. This circuit is the result of my research. I have used a photodiode, SFH2030 as an infra red sensor. A MOSFET opamp, CA3140 is used in the differential mode to amplify the pulses of current from the photodiode. LED1 is an ordinary coloured led which will light when IR radiation is being received.

The output of the opamp, pin 6 may be connected to a multimeter set to read DC volts. Infra red remote control strengths can be compared by the meter reading, the higher the reading, the stronger the infra red light. I aimed different remote control at the sensor from about 1 meter away when comparing results. For every microamp of current through the photodiode, about 1 volt is produced at the output. A 741 or LF351 will not work in this circuit. Although I have used a 12 volt power supply, a 9 volt battery will also work here.

Circuit diagram:

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Lamp Fuse Tester Circuit Diagram

Why a lamp tester or fuse tester? Testing cables, wires, lamps… belongs to a repair job and sometimes this becomes too cumbersome since one has only two hands and too often, one has to hold the part being tester and the two probes of an ordinary continuity tester all at the same time.

This fuse and lamp tester enables easy testing of lamps and fuses by using the conductivity of the human body. One of the test probes is connected to the part under test while the other probe is hel dby the normal hand.

Lamp & Fuse Tester Circuit Diagram

When the lamp or fuse is working properly, your eyes will glow in the dark! Just kidding :) . When the lamp or fuse is working properly, a small amount of current flows through the hand which is enough to switch the transistors and light the LED. Link

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Reliable Car Battery Tester Circuit Diagram

This circuit uses the popular and easy to find LM3914 IC. This IC is very simple to drive, needs no voltage regulators (it has a built in voltage regulator) and can be powered from almost every source. This circuit is very easy to explain: When the test button is pressed, the Car battery voltage is feed into a high impedance voltage divider. His purpose is to divide 12V to 1,25V (or lower values to lower values).

This solution is better than letting the internal voltage regulator set the 12V sample voltage to be feed into the internal voltage divider simply because it cannot regulate 12V when the voltage drops lower (linear regulators only step down). Simply wiring with no adjust, the regulator provides stable 1,25V which is fed into the precision internal resistor cascade to generate sample voltages for the internal comparators. Anyway the default setting let you to measure voltages between 8 and 12V but you can measure even from 0V to 12V setting the offset trimmer to 0 (but i think that under 9 volt your car would not start).

There is a smoothing capacitor (4700uF 16V) it is used to adsorb EMF noise produced from the ignition coil if you are measuring the battery during the engine working. Diesel engines would not need it, but I'm not sure. If you like more a point graph rather than a bar graph simply disconnect pin 9 on the IC (MODE) from power. The calculations are simple (default)

For the first comparator the voltage is : 0,833 V corresponding to 8 V
* * * * * voltage is : 0,875 V corresponding to 8,4 V
for the last comparator the voltage is : 1,25 V corresponding to 12 V
Have fun, learn and don't let you car battery discharge... ;-)

author: Jonathan Filippi
e-mail: jonathan.filippi@virgilio.it

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Circuit Board Checker Circuit Diagram

This little circuit indicates the basic integrity of a printed board, detecting 0V, positive supply voltage from less than 3V to 30V and floating parts. If the probe is floating, as it would be in a broken track, then both LEDs barely light up, since there is no current to drive the transistors, but if the probe touches 0V or a positive voltage one or other lights. A digital signal should light them in proportion to the mark-space ratio whereas the output of a circuit oscillating at a frequency rate below about 20Hz will cause the LEDs to flicker alternatively. The LEDs will illuminate always at a constant intensity, no matter the voltage supply used, because they are fed by a very simple FET constant-current generator (Q1).

Circuit diagram:

Circuit Board Checker Circuit Diagram

Parts:

R1 = 22K
R2 = 22K
D1 = Red LED
D2 = Green LED
Q1 = BF245
Q2 = BC547
Q3 = BC557

Notes:

• The Black clip must be connected to the negative ground of the board under test.
• The Red clip should be connected to a positive voltage source (not exceeding 30V) available on the same board.
• Metal probe is suitable for this circuit.
• Two Miniature Crocodile Clips (Red and Black) are also necessary.

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Simple Temperature Monitor Circuit Diagram

This is the Simple Temperature Monitor Circuit Diagram. This temperature monitor is practical to monitor the level of heat from its power transistors and heatsinks and if needed, to automatically turn off the amplifier to avoid damage to the vital components. Since it is not required to monitor the temperature by strict degree resolution, this simple monitor will work very well.

The temperature monitor circuit works by comparing the voltage drop of a “cold” diode (T1) with the base emitter voltage of a “warm” transistor (T2). The transistor must be attached physically closest to the heat source, ideally it should be attached to the heatsink of the power transistors.

The diode T1 must be positioned away from the heat source to ensure that it is always at room temperature. The circuit “measures” the heat difference between the transistor and the diode. T2 should not conduct as long as the temperature level being monitored is below the set threshold. The base-emitter voltage of T2 decrease by 2 mV per 0C. Once the voltage is below the level set by P1, the T2 conducts and the LED begins to light up.

Temperature Monitor Circuit Diagram

The values of R1 and R2 are dependent on the power supply voltage. The values can be computed using the following formulas:

    R1 = (Ub/V – 0.6)/5 kΩ
    R2 = (Ub/V – 1.5)/15 kΩ

For example: by 12 volts power supply, the R1 is 2.2 kΩ while R2 is 680 Ω. The maximum current consumption of the temperature monitor circuit when the LED lights up is 20 mA. Take nothe that the T2 must not become hotter than 1250C. Sourced By: Circuitsproject

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Zener Tester Circuit Diagram

The circuit can be simply Q1 is connected as a current source. By D1, there is a constant voltage on the base, and it is worth considering the selected resistor in the emitter approximately 5.6 V. With an emitter resistor of 5K6 R2 will then 1mA through the transistor.

With the chosen resistors in the circuit the current is approximately: 1mA, 2mA, 5mA, 10mA and 20mA. Great precision is not required.

If meter is chosen here for a small DVM module. However, every other meter is applicable, provided that the input resistance is high enough.

Construction:
The circuit is simple to build on a piece of PCB holes. Note that the DVM module separate from the circuit galvanic isolated power supply needs.

Using
Connect the test zener diode between the terminal A and K. Start with a current of 2mA. This is a safe value for most type zener diodes. Depending on the type of zener diode, may be chosen for a greater current. Than the Zener voltage will vary slightly.

Join the zener diode on backwards, the meter will indicate approximately 0.7V. The same picture shows an ordinary silicon diode. A germanium diode, a voltage of about 0.3 V to 0.4 V indicate when a Schottky approximately 0.2 V indicates.

Connect an LED to A and K, it will be highlighted and the Vforward (LED voltage) of the LED indicate.
The diode / LED failure, the meter displays zero if the voltage at the collector of Q1 is, this is> 25V.

 Simple Zener Tester Circuit Schematic

parts List

     Bridge rectifier BR1 = 40V 500mA
     R1 = 3k3 ¼ W
     R2 = 5K6 ¼ W
     R3 = 2k7 ¼ W
     R4 = 1k ¼ W
     R5 = 560 ohm W ½
     R6 = 270 ohm ½ W
     C1 = 470µF 35V
     D1 = 6V2 zener 400mW
     Q1 = BC161-16
     S1 = on / off switch
     S2 = 5 modes 1 mom ignition switch
     ENG = The diode under test (Device Under Test)
     DVM DVM = module of BACO or Dick Best (input adapted to 200V)

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