counting a 2 switch logic circuit

gc3076 · 2006-02-13 14:39

I am still a newbee to the BS2 programming and can't believe what a powerful learning tool this form is, amazing !

I am trying to complete, what I am assuming would be a pretty simple task. I would like to keep a running incremented / decremented real time count of a 2 switch logic circuit.··

Suggested approaches or sample sites would be appreciated................

SW1······ ·SW2

0··············· 0······· no change of state, count remains 0

0··············· 1

····· then·············incremented count, +1

1·············· 0

1·············· 0

····· then··········decremented count, -1

0············· 1

·

PJAllen · 2006-02-13 17:49

Start with a variable, X = 0
If Button2 pushed Then X = X + 1
If Button1 pushed Then X = X - 1

·

gc3076 · 2006-02-13 18:26

I see the the below logic but am finding·it hard to get through in my head how to code the momentary change in logic state.

x=0
x=x+1
x=x-1

Here is the thing, I am using 2 stationary hall-effect sensors mounted closely together ·and 1 rotating magnet. I am not sure how to code the below logic.

1. A_hall goes high then B_hal goes high, increment counter (CW) or x=x+1

2. B_hall goes high then ·A_ hall goes high, decrement counter (CCW) or x=x-1

Help !!!!!!!!

Post Edited (gc3076) : 2/16/2006 8:27:36 PM GMT

gc3076 · 2006-02-13 20:02

Post Edited (gc3076) : 2/14/2006 11:44:24 AM GMT

gc3076 · 2006-02-16 20:29

Sorry to be a pest but I am struggling here any ideas ??

PJAllen · 2006-02-16 20:44

· I figured that you were using buttons, or something, but you're actually trying to do an encoder wheel of some sort (??).· I don't think you can make that happen with two sensors and one magnet.
· An optical encoder wheel·has two sensors and a number of alternating dark and white (or dark and clear) vanes.· The sensors have to be positioned so that neither will transition at the same time.

http://www.active-robots.com/products/motorsandwheels/wheel-encoders.shtml

Post Edited (PJ Allen) : 2/16/2006 8:51:41 PM GMT

SN96 · 2006-02-16 21:05

There needs to be some kind of flip flop system (John Kerry Effect?) in the code. Then there is the issue of a/b b/a getting confused. say you are on an a/b sequence, and then "a" is miss read by the sensor, you would then be on a b/a sequence again. I don't know on this one.

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Mike

·

Bruce Bates · 2006-02-16 21:36

Folks -

A flip-flop is easily accomplished in software by exclusive ORing a bit with 1. This can be seen in the following truth table:

/code

Exclusive OR
Bit with One
1

0 1

1 0
code/

Then you can use the following:

flip_flop var bit

flip_flop = flip_flop ^ 1

ON flop_flop, GOTO Routine1, Routine2

I'm not sure what you were trying to accomplish however.

Regards,

Bruce Bates

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gc3076 · 2006-02-16 22:24

The Oring sounds like an interesting approach.

I am trying to use the 2(qty) hall sensors, mounted·closely together (stationary) and 1(qty) magnet rotating with a spinning jack screw. I want to keep count of the jack screws rotations and display the·total result of the +·\ - rotations· that happened on a LCD.

-5 CCW + 6 CW = 1 rotation

Cheers,

g.c.

gibbman · 2006-02-17 01:38

Mike (SN96) said...
There needs to be some kind of flip flop system (John Kerry Effect?) in the code. Then there is the issue of a/b b/a getting confused. say you are on an a/b sequence, and then "a" is miss read by the sensor, you would then be on a b/a sequence again. I don't know on this one.

Oh joy, politics on a Parallax forum! My guess is that the a/b b/a confusion factor is more of a W effect. Excuse my disassembling....
With good nature,
Jim

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In the end, it seems that it's all about getting the LEDs to blink....

Jon Williams · 2006-02-17 04:37

Have a look at Scott Edwards' rotary encoder program for the BS1 -- it might lead to an answer.

http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv8.pdf

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Jon Williams
Applications Engineer, Parallax

gc3076 · 2006-02-17 19:37

Ok, I think I am moving away from the Hall-effect sensor to complete this task. What do you think about a rotary encoder as shown in the example Jon has mentioned. I want this to count revolutions and show CW/CCW direction.

6CW-10CCW= 4 revolution result

Will the below/enclosed encoder count CW/CCW revolutions ?

Post Edited (gc3076) : 2/17/2006 7:46:17 PM GMT

PJAllen · 2006-02-17 20:49

gc3076 said...
Will the below/enclosed encoder count CW/CCW revolutions ?

Yes, but...
Actually --·you're going to get several "clicks"/pulses·per revolution (hence, "16 or 32"), not one pulse per revolution.

Bruce Bates · 2006-02-17 21:35

gc3076 -

Now that you've been a bit more specific about what you're intending to do, what you need is a quadrature encoder. There are Hall Effect quadrature encoders, as well as optical ones, and other types as well.

Allegro makes a nice small Hall Effect one which I've used quite successfully before. You can find it here: http://www.allegromicro.com/sf/3425/

Thanks to Dr. Tracy Allen, here are some excellent applications notes on the use of quadrature encoders with the PBASIC Stamp:
http://www.emesystems.com/BS2fsm.htm#twobit

Regards,

Bruce Bates

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counting a 2 switch logic circuit

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