I am making a digital clock. You can see the progress on youtube:
DIY Clock powered by Arduino - YouTube
But I want it to only be on when the TV is on. The TV has USB ports for diagnostics and F/W upgrades.
These USB ports only output power when the TV is on. So, I'd like to use a few mA to trigger the clock's power latch.
This is what I've got so far. It uses just about the same latch as my power supply does but I moved some resistors to eliminate the voltage divider and still maintain t=0 short protection.
Please let me know what you think.
*** Edit: Updated schematic *** in comment 4
I haven't specified Q1 yet because I'm still shopping. It will be capable of passing at least 8A (exceeds clock's max draw) with a -4.5V trigger.
I also have a few questions:
What should I do with pin 6 on U1?
What should I do with the shield and data pins on J1?
I didn't know what symbol to use for the 5VDC power supply input. Is that symbol clear or should I switch it to a 5V arrow like the other side and add an annotation?