Posted by Bill Lash on 17, 2000 at 7:28 PM:
In Reply to: Built ArcadeOS printer hardware - but on cold boot, defaults to ON! posted by Edge on 17, 2000 at 1:47 PM:
I wish he had real schematics there instead of showing the outlines of the chips, but anyway...
You might look at a couple of things. First, other than the way it powers up, does everything work the way you expect? Many relays come with both "normally open" and "normally closed" contacts, so if the circuit works backwards, that is a possibility.
If the circuit works correctly, except for the power-up condition, you might try providing a power-up reset to the chip you are using. For the 74HCT161, if you connect pin 1 through a resistor to +5 and through a capacitor to ground, you will hold the reset pin low until the capacitor has time to charge. If you use a 10K resistor and a .1 uF capacitor, you should get enough of a reset pulse to start out in the right state. Resistors in the range from 1K to 10K should be fine, and anything from .1 uF to 10 uF should work. The bigger these component values are the longer reset will be held low. HCT components should work ok this way, but some of the older CMOS parts (4000 series CMOS and the early 74HC series) could behave strangely when input voltages were between logic levels.
I hope this works out for you.