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The Motorola spec sheet for the 4543 (14543) notes an LED display could be driven, but the IC only supplies about 10ma per segment. Not much. It suggests it's "Phase" be connected to low for C/C Leds, and high for C/A Leds, but it also suggests for higher draws (VDD <= 10 V or Iout >= 10 mA) that a bipolar transistor be used. Anybody, I'm sure a Darlington driver array (such as a ULN2003a, for 5V devices) would do "the trick", but I don't need 500ma for each segment. How about a package that supplies less current, w/o me having to do 35 transistors individually ?? If I do the Qs individually, which (TO-92) might someone suggest for this common cathode task?
Anybody on the Bi-Polar transistor array driver thing, for less than 500ma per channel (segment)? What about a TO-92 which would be ideal w/o extra discreet components?
To me it looks grounded ("Clear" on your divider 390...IC6B pin 14 which in the spec sheet is identified as "Master Reset"). How do you speak of it being inverted? It has the Ground signification on it.
With my ten second gate, I would have the display blank for ten seconds, then display the most recent latched/decoded binary values for ten seconds. I want it to display for ten seconds, blank (long enough to load the BCD codes), and then start counting all over again (which would require the J-K to reset, but since it's being used in toggle mode, I would actually have to reset it's clock input back to low, hence, MR the divider 390s). Any idears ??
I wonder why the notice of a reply to this thread ended in my SPAM folder?
What a <74LS112> J-K flip flop does in the toggle state is that every low to high transition of the clock input...So NO, it does not oscillate...
The reason it is needed is that the decade counters do not produce a 50 percent duty cycle from their Q outputs. Only Binary counters do that. But the decade counter will divide by 10. Its just that the Qd output will not be useful as a gate pulse because it is not 50/50 duty cycle.
The J-K flip flop's "preset & clear" functions are asynchronous meaning they happen immediately. They do not wait for any signal or gates to change. They do it instantaneously.
Well it does reset.