Diagram Exclusive |top| - Blue Ring Tester Schematic
A shorted turn lowers the inductance significantly and increases the damping effect.
If you are currently building this circuit or troubleshooting a specific piece of equipment, let me know:
: It is optimized for high-frequency wound components. It may fail to accurately test inductors with very low or very high inductance, such as simple wall-adapter transformers. blue ring tester schematic diagram exclusive
If you are building this circuit on a custom PCB, keep the traces between the test leads, the tank capacitor, and the comparator input pins as short as possible to minimize stray inductance and resistance.
I have designed this to look like a high-value "share" within the electronics community. A shorted turn lowers the inductance significantly and
| Reference | Value | Notes | |-----------|-------|-------| | U1 | NE555 | Timer IC | | U2 | LM393 | Dual comparator (one used) | | D1, D2 | 1N4148 | Fast switching diodes | | D3 | Red LED | Fault indicator | | D4 | Green LED | Pass indicator | | C1 | 100nF | Ceramic disc | | C2 | 10nF | Polyester | | C3 | 100µF / 16V | Electrolytic | | C4 | 10pF | Ceramic (critical) | | R1 | 10kΩ | 1/4W | | R2 | 1kΩ | 1/4W | | R3 | 100Ω | 1/4W | | R4 | 1MΩ | 1/4W | | R5 | 47kΩ | 1/4W | | R6 | 10kΩ | 1/4W | | R7 | 330Ω | 1/4W | | R8 | 220Ω | 1/4W | | RV1 | 10kΩ trimpot | Calibration | | Lx | Coil under test | External connection | | Power | 9V battery (or 9-12V DC) | Regulated recommended |
The is a specialized, high-performance Q-meter designed to send a high-frequency pulse into a transformer or coil winding, causing it to resonate or "ring." If you are building this circuit on a
Connect a known-good SMPS transformer primary winding. Adjust the variable resistor connected to the LED driver pin until all LEDs just light up. This establishes your baseline "good" reading. Troubleshooting Common Layout Issues
: It cannot detect an open-circuit winding. If a coil is completely broken, 0 LEDs will light up, mimicking a dead short. Always verify continuity with a standard ohmmeter first.