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- Newsgroups: sci.electronics
- Path: sparky!uunet!charon.amdahl.com!pacbell.com!decwrl!sdd.hp.com!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!cbnews!wrb
- From: wrb@cbnews.cb.att.com (wallace.r.blackburn)
- Subject: Re: Idea for LED sequencer
- Organization: AT&T
- Distribution: usa
- Date: Thu, 5 Nov 1992 18:50:45 GMT
- Message-ID: <1992Nov5.185045.28493@cbnews.cb.att.com>
- References: <1992Nov3.094923.44351@kuhub.cc.ukans.edu> <Bx7Ez4.MIM@news.cso.uiuc.edu>
- Lines: 53
-
- In article <Bx7Ez4.MIM@news.cso.uiuc.edu> rky57514@uxa.cso.uiuc.edu (Tall Cool One ) writes:
- >heacock@kuhub.cc.ukans.edu (Doug Heacock) writes:
- >
- >>I'm putting together a quick-and-dirty circuit that will light 10
- >>LED's in sequence, one after the other. Here's my idea so far: I
- >>intend to use half of a 4011 (quad 2-input NAND gate) as a clock
- >>oscillator to drive half of a 4518 (dual synchronous up counter),
- >>which will in turn drive a 4028 (BCD-to-decimal decoder), which will
- >>actually drive the LED's. I was thinking I could connect all of the
- >>LED cathodes to ground through a single 330-ohm resistor, since only
- >>one would be lit at a time.
- >
- >>Does this sound workable? I welcome more elegant solutions--these
- >>chips just happen to be the ones I have on hand at the moment.
- >>+-----------------------------------------------------------------+
- >>| Doug Heacock, Academic Computing | heacock@kuhub.cc.ukans.edu |
- >>| Services, The University of Kansas | heacock@ukanvax.bitnet |
- >>| Lawrence, KS 66045 | Amateur radio: N0NZQ |
- >>+-----------------------------------------------------------------+
-
- Oh, what the hell? Might as well give the "swatting a mosquito with a
- sledgehammer" approach.
-
- IF you have access to a programmer and IF you wouldn't mind writing some
- very simple assembler (I know, pretty big ifs):
-
- A tiny microcontroller like the MC68HC705K1 could do this easily and
- cheaply. The 'K1 has 10 I/O lines - one for each LED. They can drive the
- LEDs directly since they can source 25 mA. The code would just be:
-
-
- START BSET LED1 ;turn on 1
- JSR DELAY ;delay subroutine
- BCLR LED1 ;turn it off
- BSET LED2 ;turn on 2
- JSR DELAY
- .
- .
- .
- BCLR LED10
- JMP START
-
- I know this is overkill, but since the 'K1 sells in singles for $3.35 and
- you would need no other chips, it's really not that crazy. Physical design
- becomes trivial and the software would take less than an hour (10 minutes).
-
- I've been playing with this MCU a lot lately, so maybe it's a case of "if
- all you have is a hammer, everything starts to look like a nail".
-
- Comments to att!ccsitn!wrb, flames to /dev/null/eatme.
-
-
- Wally Blackburn AA8DX
-