Circuit and LED Datasheet are attached
This circuit is used to monitor the status of a 9VDC supply that powers an X-ray Source (XRS) Controller. An Altera Cyclone FPGA is used to control the supply. When the 9VDC is on, the LED will shine and the XRS Controller will turn on. If the LED is off, the XRS Controller is not getting 9VDC.
My problem is with the LED. It sometimes lights up dimly, or does not shine at all, even though the 9VDC is on.
As I start to measure the voltage across, I first attach a probe to the anode of the LED. Once this is done, the LED shines bright, as it should! I measure the voltage to be 1.965VDC.
I then turn off the 9VDC, then turn it back on. The LED shines bright. I turn it off again, then turn it back on, now the LED shines dimly. So I go to measure the voltage across the LED again, this time, it does not light up right away. I get an initial voltage reading of ~1.4-1.5VDC for about 2sec (LED is off), then the voltage jumps to 1.965VDC (LED shines bright).
Has anyone ever seen this before? Can someone please explain this please?
This circuit is used to monitor the status of a 9VDC supply that powers an X-ray Source (XRS) Controller. An Altera Cyclone FPGA is used to control the supply. When the 9VDC is on, the LED will shine and the XRS Controller will turn on. If the LED is off, the XRS Controller is not getting 9VDC.
My problem is with the LED. It sometimes lights up dimly, or does not shine at all, even though the 9VDC is on.
As I start to measure the voltage across, I first attach a probe to the anode of the LED. Once this is done, the LED shines bright, as it should! I measure the voltage to be 1.965VDC.
I then turn off the 9VDC, then turn it back on. The LED shines bright. I turn it off again, then turn it back on, now the LED shines dimly. So I go to measure the voltage across the LED again, this time, it does not light up right away. I get an initial voltage reading of ~1.4-1.5VDC for about 2sec (LED is off), then the voltage jumps to 1.965VDC (LED shines bright).
Has anyone ever seen this before? Can someone please explain this please?
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