Re: Need a LED switch

On Sep 27, 2:37 pm, ehsjr <eh...@xxxxxxxxxxxxxxxxx> wrote:
Allen Bong wrote:
On Aug 15, 5:54 am, John Fields <jfie...@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Wed, 12 Aug 2009 19:35:30 -0700 (PDT), catdady2k <carleca...@xxxxxxx>
wrote:

I want to use a switch to step through a ten LED string one LED at a
time. I also need to bypass a LED (take it out of the sequence) when I
want. I'm ginna be using a foot swtich if this matters. Any advice
will be greatly appreciated.

---
Interesting task.

I'm assuming that you'll have a switch at each position which will cause
the circuit to bypass that position from the sequence in one position
and include it in the sequence in the other position.

In other words, if all of the switches are in the, say, 'include'
position, the sequence will be 1,2,3,4,5,6,7,8,9,10,1,2...
with an increment made every time you push the footswitch.

On the other hand, if you place the '2' and '6' switches in the 'bypass'
position, then the sequence will be 1,3,4,5,7,8,9,10,1,3,4..

Is that what you want?

JF  

Hi John,

After spending a few hours on my PC, I finally came out with this
circuit:

http://www.flickr.com/photos/11236051@N08/3955055816/

you can get a larger print using the "All sizes".  But some how it
doesn't work if 2 switches are ON next to each other, ie you cannot
bypass led 2&3 or 4&5&6.  Is there anyway to get around this problem?
The 555 is used as a one shot and the 4081 may be replaced with 4011
to make an RS FF to debounce the foot switch.  Sine only 1 LED is
switched on at one time I used only one 330 resistors.

So in this project, I think it is defintely more appropiate to use a
PIC.

Allen.

Hi Allen,

It looks like a timing problem. The 555 extra clock pulse kicks
the 4017 to increment by 1, and you need that increment to trigger
the 555 to produce another extra pulse when bypassing consecutive
LEDs. Trouble is, the 555 pulse is still active, and in addition,
the C2/R6 TC hasn't allowed C2 to discharge enough.  You need to
wait for the 555 to time out, and for the C2/R6 TC before generating
the second (third, fourth etc) extra clock pulse.

The relay circuit I posted a while back allows bypassing multiple
consecutive lights, but requires SPDT switches.  I can post a complete
tested** PIC solution using a 16F84A chip if you like. Complete = code
(assembler) and schematic. I can also post a picture of it wired on perf
board to ABSE or send you email with the schematic & photo if you don't
have access to ABSE. The PIC solution also allows bypassing any
combination of LEDs.

** = tested with a PC board switch.  I don't know how much your
foot switch bounces, so I wrote the debounce routine with a
multiplier that can be increased to handle badly bouncing
switches.

The PIC solution offers the advantage of low parts count:
6 resistors, 1 cap, the 10 position dip switch, the LEDs and the
PIC (18 pins). On my perf board, I added a 5V regulator (78L05
and 2 caps).  The PIC disadvantage is that you need a programmer
and software and have to know how to use them. If you're already
set up for that, the disadvantage disappears.

If you want a good no relay hardware solution , use whatever John
recommends.  His circuits are NICE!

Ed- Hide quoted text -

- Show quoted text -

Hi Ed,

Thanks very much for your comments on my circuit. Yes I would like a
copy of your pic solution as well as the software. I have a 16F628
which is similar to 16F84A to try out your circuit. I've already made
the PIC programmer that uses RS232 and it can handle 8/18/28/40 pin
PIC.

AFAIK, John has not designed any circuit regarding this application.
Actually I enjoyed studying his circuit very much but I was
disappointed this time.

As for my circuit, I would see if I can have a workaround on it when I
have time.

Allen.
.

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