Hi
I'm thinking of using AT90USBKEY (http://www.atmel.com/Images/doc7627.pdf) to control my circuit.
The problem is, I don't know if I will get enough current from the USB port and output ports of the controller. USB should always give at least 100mA and more if it has a high power supply but can the AT90USBKEY also supply enough?
I need to run 7 optocouplers from the output ports. I'm thinking of using 4N25-M:
http://www.farnell.com/datasheets/683405.pdf
If I understand it rigth then it needs a min of 10mA? Would the AT90USBKEY be able to give over 70mA in total, I'll probably need to add some other stuff too but that takes less current?
If its not a great solution, where could I get the power from? Would taking the 5V from USB power pin (I'm thinking from the AT90USBKEY board before it is converted to 3,3V) be a bad idea?
I have a 12V power supply to run relays and LEDs. Would it perhaps be more effective to convert it to 5V and use this? Would converting about 100mA from 12V to 5V make a lot of heat?
Thank you
I'm thinking of using AT90USBKEY (http://www.atmel.com/Images/doc7627.pdf) to control my circuit.
The problem is, I don't know if I will get enough current from the USB port and output ports of the controller. USB should always give at least 100mA and more if it has a high power supply but can the AT90USBKEY also supply enough?
I need to run 7 optocouplers from the output ports. I'm thinking of using 4N25-M:
http://www.farnell.com/datasheets/683405.pdf
If I understand it rigth then it needs a min of 10mA? Would the AT90USBKEY be able to give over 70mA in total, I'll probably need to add some other stuff too but that takes less current?
If its not a great solution, where could I get the power from? Would taking the 5V from USB power pin (I'm thinking from the AT90USBKEY board before it is converted to 3,3V) be a bad idea?
I have a 12V power supply to run relays and LEDs. Would it perhaps be more effective to convert it to 5V and use this? Would converting about 100mA from 12V to 5V make a lot of heat?
Thank you