If you buy or salvage transformers it would be quite difficult to identify the high voltage and low voltage side of the transformer without a testing tools. However you can solve this problem using LCR digital multimeter to measure the identify the connecting pins using continue test and also measure the inductance to find out the low voltage side and high voltage side of the transformers. And with that you can start your electronic project with confident.
Step 1: Find Out the Connecting Pin of Transformers
Guessing the connecting pins of the transformers can be very difficult especially multi-phases primary and secondary such as the flyback transformers. Fortunately most if not all the digital multimeters have the continuity test. Using the continuity test you can identify which are the connecting pin of the transformers. However this it will not tell you the low voltage winding coil or the high voltage coil of the transformers. Therefore follow step 2 to identify the low voltage and high voltage phase of the transformers.
Step 2: Identify the Low Voltage and High Voltage Winding of the Transformer
In order to find out the low voltage and high voltage coil winding of the transformers we can use the LCR digital multimeter to measure the inductance value of the transformer. Lower inductance value is the low voltage coil winding of the transformers whereas the Higher inductance value signify the high voltage side of the transformers. Now you can start your DC to AC inverter using transformer either step up or step down with confident :).