This project is a VGA tester using a Attiny2313 running at 20MHz. This device can be used to test VGA monitors. Check schematic and source code on the link below.
VGA tester using Attiny2313 – [Link]
CHEX is a perfect device for testing CCPM servo setup. This device allows you to connect 1-3 servos simultaneously. It can be used as a servo signal generator for testing electronic speed controller (ESC) without using a transmitter and receiver. Also, this device can be used to check other RC devices as shown in the features below.
E-CHEX : Multi-purpose RC devices checker - [Link]
This project is a servo tester based on PIC16F690 and with code written in C. The timing loop is a crude one relying on a simple tight loop, so the pulses are not massively accurate.The board has four modes of operation, selected using TACT switches with the status indicated on LEDS built into the switches .
Servo Tester Module - [Link]
This project is a LAN cable tester able to check any type of LAN cables (straight or cross). Using this tool you are able to check for possible faults on LAN cables. Just connect the cable and watch the led glow one by one. If there is a faulty cable then the corresponding led won’t light. Check schematic on the link below.
LAN cable tester - [Link]
This simple circuit is an IR tester able to test and help troubleshoot any infrared control. The circuit is using an UA741 OPAMP and a BPW41 IR detector to produce a visible light on red LED when infrared signal is detected from BPW41.
Simple IR tester - [Link]
This project shows how to build a N type MOSFET tester that will help you find out if a MOSFET is working or not. The circuit is really simple and uses only a few components. Check schematic and building diagrams on the link below.
N-type MOSFET tester - [Link]
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.
Simple Crystal Tester - [Link]
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.
Transistor tester - [Link]

Using Arduino True Battery Capacity Tester you are able to measure the charging capacitance of Li-Ion/NiMH/NiCD/Pb batteries and display results on character LCD screen or aquire full discharge characteristic graph on PC. Tester supports auto battery type detection and discharge takes from 30-120 minutes to complete, giving you an indication of battery’s quality.
Arduino True Battery Capacity Tester (Li-Ion/NiMH/NiCD/Pb) - [Link]

Many people assume that all LEDs can be powered with a constant 3V power source. LEDs in fact have a non-linear current-voltage relationship. The current grows exponentially with the voltage supplied. There’s also the misconception that all LEDs of a given color will have a specific forward voltage. The forward voltage of an LED does not depend on the color alone and is affected by other factors such as size of the LED and its manufacturer. The point is, the life expectancy of your LED may degrade when its not powered properly.
Current Regulated LED Tester - [Link]







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