Hi, I'm trying to run a 700mA LED load through a one-shot 555 timer circuit, using a hall effect sensor as the trigger and with a 12V power source (schematic attached). I can't make my TIP122 transistor switch properly - it opens the current even when the hall sensor is not triggered.
How do I determine the necessary base current? The TIP122 datasheet (https://www.electro-tech-online.com/custompdfs/2013/04/TIP122.pdf) suggests that the DC current gain is 1000...so I think I need a 7mA base current? Assuming 11.3V gets through the timer: 11.3V/0.007A = 1.6K base resistor?
Any help GREATLY appreciated I'm going crazy. I can make it work with a 2N2222, but I believe that transistor is not rated for more than about .8A and I need 1.4A here.
Thank you!
How do I determine the necessary base current? The TIP122 datasheet (https://www.electro-tech-online.com/custompdfs/2013/04/TIP122.pdf) suggests that the DC current gain is 1000...so I think I need a 7mA base current? Assuming 11.3V gets through the timer: 11.3V/0.007A = 1.6K base resistor?
Any help GREATLY appreciated I'm going crazy. I can make it work with a 2N2222, but I believe that transistor is not rated for more than about .8A and I need 1.4A here.
Thank you!