Better reset circuit
I found that the Webpal did not reset
reliably after short power losses. Since I was using the
Webpal in server
applications in hard-to-get-to locations, I wanted a more reliable
reset circuit.
To improve the reset circuit, I added a MC34064
Undervoltage Sensing Circuit. This provides a more reliable
reboot on short power losses. The MC34064 should be wired across
the
existing reset switch as shown in the photo.
A datasheet for the MC34064 can be found here.
The MC34064 should be wired as follows:
- PIN 1 (RESET -- MC34064 right pin in photo) connects to the upper
terminal of the reset switch.
- PIN 2 (Input -- MC34064 center pin in photo) connects to the +5V
at the ISA connector PIN A3.
- PIN 3 (GND -- MC34064 left pin in photo) connects to the lower
terminal of the reset switch.
As shown in the photo, by mounting the MC34064 upside down, its outside
leads match up with the wiring of the reset switch and then the center
pin can be wired to a source of +5V.
Last updated: Feb 19 2004