Hi all,
I'm using ULN2803 to control some LED, driven by a 7HC595 and encountered a problem i cant figure out yet. Theoretically, when 7HC595 outputs are low (0v), LED at the output of ULN2803 should be off; but in my case they are on, and when high they are also on but brighter! They are direct connected with no pull down/up resistors. I'm using Arduino SPI to control the 7HC595. I'm thinking that maybe the 7HC595 low outputs are not true at 0v but floating; I did measure with an oscilloscope and got 0v though. I'm not sure whats going on here. Please help.
I'm using ULN2803 to control some LED, driven by a 7HC595 and encountered a problem i cant figure out yet. Theoretically, when 7HC595 outputs are low (0v), LED at the output of ULN2803 should be off; but in my case they are on, and when high they are also on but brighter! They are direct connected with no pull down/up resistors. I'm using Arduino SPI to control the 7HC595. I'm thinking that maybe the 7HC595 low outputs are not true at 0v but floating; I did measure with an oscilloscope and got 0v though. I'm not sure whats going on here. Please help.