Review on Digital Red/Blue LED Tachometer RPM Speed Meter with Hall 🔴 Proximity Switch Sensor NPN for LED Panels and Modules - EEEkit by Mike Wallace

I'll let my photo provide most of the details but I'm very frustrated that I've spent hours trying to figure out this apparently faulty unit. I modified the cable during testing, so I cannot return it. I will buy a competitor product with better documentation. Symptoms: After the device was connected according to these instructions, the display remained dark and did not show any numbers when the Hall sensor was subjected to an alternating magnetic signal. The polarity of the power supply and main wiring was confirmed by the hall effect sensor glowing and flickering in response to the movement of the magnet. Then I read more comments and saw that the number on the sticker was upside down. I reassembled the unit according to the working configuration shown in the YouTube video "HOW TO CONNECT A DIGITAL TACHOMETER" cited in the comment. This is the last schematic in my picture. I also tried flipping the magnet, as per the other review, to no avail (apart from a small reduction in sensor LED flicker). The fact that the schematic and markings on the case are suspect (see other reviews) should have told me it wasn't worth the money and time. It's outrageous that this type of device doesn't have any wiring specs other than the Revain page! Please give us the key.