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2.2 - Status LED

There is a green status LED on the LabJack U3. This LED blinks on reset, and then remains steadily lit. Other LED behavior is generally related to flash upgrade modes (Section 1.2).

Normal Power-Up Status LED Behavior: When the USB cable is connected to the U3, the Status LED blinks 5-6 times over 2 seconds and then remains solid on.

LED blinking continuously at about 4 Hz, even with no software running: This indicates that the U3 is in flash mode. See Section 1.2 and reprogram the device.


When I connect my labjack to the computer the status LED blinks a few times and then stops glowing. My computer fails to detect LabJack. Everything was working fine until this one time when it suddenly stopped working. Any clue what could be wrong?

Thanks for the reply. Turns out, restarting windows worked!

If it happens again, see if it is enough to disconnect/reconnect the USB cable from the U3, or if you have to restart the computer.

Sounds like the USB sub-system on your computer was confuzzed.  What version of Windows?

Reconnecting the USB cable did not help, even on different USB ports. The VI that I was using to read out labjack ports returned a communication error, and the LJControlPanel did not detect labjack. This is on Windows 7.

OK.  Used to have some problems on XP related to Windows bugs with selective suspend and power save, but have not seen any such issues on Windows 7.  Just in case, though, for the sake of long-term operation you might want to "disable usb selective suspend", and even disable as many windows power saving features as you are willing to disable.