Very well put, John. I was thinking along these lines as well. You don't
need to have a nixie to start a nixie clock project. In fact, the nixie
can be the very last component. You might even have a stage with
7-segment LED's and 7-segment BCD drivers to get your clock code up and
running. One could replace the 7-segment drivers and LED's with 74141's
and nixies at a later stage, once the BCD and blanking was working
correctly.
-Adam W7ATJ (soon AJ9D)
On 9/30/2011 6:41 AM, John Rehwinkel wrote:
Hi mike, you might have considered this and rejected it, but how about
doing your first clock with numitrons? They don't require the elevated
voltage and small ones can be bought off ebay cheaply.
Another idea is to go ahead and use a 74141 type drivers with an ordinary five
volt supply and ten LEDs with a 1k anode
resistoror or even small incandescent lamps (you can chop up a holiday light
string to get cheap bulbs and sockets).
This could be done cheaply or even free. A dead ethernet hub will generally
get you a five volt supply and several
LEDs. You can get a 74141 chip for a buck or so. You can start lighting LEDs
even before you round up a driver chip.
Once you have that, you and your kids can manually tie the various input pins
to the positive supply or ground,
and see how the chip works to drive a single output at a time.
You could proceed forward in two ways. You could add a microprocessor and work
out how to program the micro
and light up the LEDs or bulbs. Or you could try to scrounge up a high voltage
supply and some small neon bulbs.
Supply the neons with your HV supply, and change the anode resistor to 470k or
so, and your 74141 will light them
instead of the LEDs.
Then, when you find a nixie tube, you can just swap it for the neon bulbs, and
change the anode resistor appropriately,
still using the same 74141 chip to drive it.
This way, you have something up and running soon and cheaply (I find this the
best encouragement), you start with
safe low voltage, and you can learn about microprocessors a step at a time.
If you add a second 74141 or a pair of anode drivers, you get a two-digit
display, which is sufficient for getting
started with a thermometer. You can quickly learn to read a column of ten
lights (LEDs or neons), or you can
arrange for them to shine through digit cutouts. This is exactly how the
display worked in some HP frequency
counters:
http://www.hpmemory.org/wa_pages/wall_a_page_11.htm
As you can see, I'm a big fan of getting something working at an early stage,
doing things on the cheap, and
electronics in general.
- John KG4L
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