[Today’s run: none yet, hope for 3+ by end of day]
I had put the nixie clock project on the shelf.
I got the digits running and the increment roll-over from seconds to minutes and minutes to hours. I was happy with myself for getting that to work (even though it is a well-known problem and I just copied something I found on the net).
My next problem was trying to set up some switches to change the time, for setting it to the correct time. Plain switches didn’t work because they caused multiple signals to come through at random times. This is because most any normal on-off switch has some in-between state where the contacts are just closing or just opening and the signal will bounce on and off multiple times during this time.
I tried a couple of hair-brained things but they didn’t work.
Anyway, recently I was reading my new 2014 ARRL handbook that I got for Christmas and the light came on. I could use a capacitor and resistor to make a debounce circuit.
I had seen the debounce circuits on the net, I googled on switch debounce. But they were showing a switch to ground and that is not what I have. Mine is a switched signal path. I couldn’t get how to modify that.
But with the RC chapter reading it seemed like I ought to be able to make that work somehow.
So I put it together, and it seems to work OK! An on-line RC calculator helped me find some values that were in the .01-0.1 second range. What I have is a 220 microFarad electrolytic capacitor and a ~250 ohm resistor in parallel to ground. The signal in and the signal out both attach to the “high” side of the resistor/cap pair.
I breadboarded that and I think it will work!
Here’s a picture:
I’m going to have three of these switches:
- The seconds adjust switch
- normal – 1 pps
- stopped – no input
- fast – 10 pps
- The minutes adjust swtich
- normal – rollover from the seconds
- fast – 10 pps
- The hours adjust switch
- normal – rollover from minutes
- fast – 10 pps
To set the clock I can turn the seconds to off. I can then adjust the minutes, then adjust the hours. I then wait until the right second and switch the seconds switch to normal and away we go. (It sounds like maybe I could do without the ‘fast’ setting for the seconds if I want.)