The circuit relies on a low-cost microcontroller or a specialized comparator circuit to pulse the transformer and count the resulting oscillations. Below is the functional architecture of the exclusive Blue Ring Tester circuit. 1. Power Supply Section
Using the Blue Ring Tester is incredibly straightforward. Connect your test leads across the primary winding of the transformer or inductor under test (ensure the circuit board you are testing is completely powered down and discharged).
After assembly, .
Happy diagnosing, and may your LOPTs always ring true!
A momentary negative-going excitation pulse (typically generated by an onboard 555 timer circuit or a micro-controller tuned to a low frequency like 10Hz to 50Hz) shocks the tank circuit into oscillation through resistor R5cap R sub 5 2. The Comparator Stage (LM393) blue ring tester schematic diagram exclusive
To use the tester:
: Keep the traces between the test leads, the protection diodes, and the 10nF tuning capacitor as short and thick as possible. Stray inductance or resistance in these traces can artificially lower the "Q" reading. The circuit relies on a low-cost microcontroller or
: Common designs utilize the CD4015BE (shift register) and CD4069 (hex inverter).
To calibrate the Blue Ring Tester, adjust the R19 sensitivity potentiometer until the first two LEDs (or the first red one) just barely illuminate with the test leads open. Power Supply Section Using the Blue Ring Tester
Beyond flybacks, it is excellent for testing deflection yokes in TVs and inductor coils in audio gear.
Every time the ringing voltage swings above this threshold, the LM393 outputs a clean, 5V square-wave pulse. 4. LED Bar Graph Display