Delay the power on of a USB device using a 555 timer IC.

I have a TV with ample USB power coming out of the back to power a Raspberry Pi, however the USB port is only powered when the TV is on. It then takes about 20 seconds from turning the TV on to it being able to initialise graphics on the Raspberry Pi.

To solve this problem I built this delayed power on circuit, so 20 or so seconds after I turn the TV on, the Raspberry Pi gets power and the graphics initialises correctly.