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Cake day: July 5th, 2023

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  • The output is stuck at low.

    The input keeps alternating high/low. I’ve checked by disconnecting it and then measuring it. I’ve also checked by substituting the source for identical brand and model spare unit.

    E: Something really bizarre to me happened during testing today. I decided to change the buffer power supply to another 5V rail to isolate the DC-DC from the equation. The buffer still got stuck. But that’s not the funny part. After getting stuck, I disconnected the 5V power to the buffer to let it rest. To my shock, the output went high. I cycled the input and to my surprise output signal at the bike computer was correctly registering high/low. With no power going into the buffer. 🫢 That is, the buffer has its input, output and GND wired, 5V disconnected. I never tested this scenario before because I was disconnecting the whole circuit, upstream of the DC-DC, which also feeds the torque sensor (input). I wish I understood enough to explain why this unpowered IC makes the bike computer recognize the signal it otherwise wouldn’t. 😂

    E2: For completeness, the original problem that necessitated this whole operation was that when directly connected to the computer, the signal low never fell below 1.2V and the computer’s threshold for registering low is around 1-1.1V. High was registering correctly.