[Heathkit] SB-650/led modification

Sun, 02 May 2004 21:59:11 +0000

  I'm an RF man myself, but I know TTL.

>  Of course the +170 volt supply for the nixies would no longer
> be needed, just the 5 volt supply for the LED's, and I think the
> stock circuit board can remain, just pull out the 7441's and run the 
> four lines from each storage register to each 7447 input.

>  Any thoughts?

   With 7 segment LED displays you need to light several segments at the same 
time, therefore you need a current setting (and limiting) resistor for each
segment.  (these control the brightness)

   With the common anode type of display you need a resistor for each BCD to
7 segment decoder IC output pin to the display device.

   You can get almost any color LED's now-a-days, do you want RED or YEL or 
GREEN (my favorite)?

   The LEDs can be powered from 5, 12 or, 24 Volts, by changing the resistor's 
value, it could even be BEFORE the existing 5 Volt regulator, which the displays 
might tax.  You could build a separate variable 5 to 12 Volt regulator for the 
displays so you can control the brightness with a shaft or knob.
-- 
        73 (= Best Regards) de: Ron [email protected]
     100% LINUX, since July, 1997   SENT Time and Date are UTC
        Visit my HAM Web SITE at: http://www.qsl.net/ka4inm