| ??? 05/06/06 09:23 Read: times |
#115753 - Another suggestion... Responding to: ???'s previous message |
Scott said:
Basicly, there is octal latch 74lcx245 that accepts the input. The input has 1k pull-up resistor to 5V. There is push button switch that is connected to the pull-up resistor and gnd. When the switch is pushed the input goes low. And: I believe the 74LCX245 is blowing out do to power surges and 11Vac noise/crosstalk. I don't believe the 110Vac lines is actually making physcial connect. The low and high voltage lines are taped next to each other. Assuming I have understood the above correctly, you could try making the pullup 270R, and add a 1K2 'pulldown' resistor at the input of the 74LCX245. This way, any input noise would be forced to 'drive' a 'load' (in this case, the 1K2 pulldown). However, when the switch is closed, the 270R will have the full 5 Volts across it, drawing nearly 20mA from your PSU - so make sure you allow for this if you have to apply this circuit to five inputs or more etc. You may have to adjust these values where desired. This is, of course, an addition to the tranzorb and input filtering. Valentin |
