I have a printer that requires 5VDC and 28VDC power. The original power supply is not available, and I was unable to find an affordable power supply with the required voltage and current ratings. So I'm using two power supplies, one for 5V and one for 28V. The problem is that upon power up, the 5V comes up immediately, but the 28V supply takes between one and two seconds to come up. I need a simple (i.e. low component count) circuit that will hold RESET low on the uP until both 5V and 28V are up. Whatever I use must be through hole. Any suggestions would be appreciated.
12 years ago