# Eagle snafu,CIRCLE command

Discussion in 'Electronic Design' started by Robert Baer, Dec 3, 2013.

1. ### Robert BaerGuest

The following commands were tried (no more, and no less):
CHANGE LAYER 121
CHANGE WIDTH 0.0005
CIRCLE (0.496 2.842) (1 0)
Note that last command is EXACTLY from the so-called help; gives
radius of 2.884957 and if i try CIRCLE (0.496 2.842)(0 0) the result is
exactly the same.
The position of the center does have some effect on this bogus
"diameter".

2. ### Robert BaerGuest

Now files are getting corrupted during editing.
SCR commands now have no VISIBLE effect, but Eagle thinks there has
been a change.
I only know after the fact - which is when all is settled.
Real crap!

3. ### Jasen BettsGuest

sounds unusual, more people swear by it that at it. perhaps run a
generic diagnositc like memtest-86+ overnight?

4. ### Jasen BettsGuest

oops:

more people swear by it THAN at it.

5. ### John SGuest

It's doing exactly as it is told. The problem is that the second set of
enclosed numbers (1 0) is NOT the radius, it is a POINT on the
circumference. Notice that your circle's circumference passes through
the point x=1, y=0 in the first case and through x=0, y=0 in the second
case. Of course, it defines the same circle because one circle passes
through both points.

6. ### John SGuest

To follow up with an example, if you want a circle with center at
0.496,2.842 and a 1 inch radius:

* Make sure your grid is set for inches
* CIRCLE (0.496 2.842) (1.496 2.842)

7. ### Martin RiddleGuest

Looks like the info command does not calculate the radius correctly.
I tried with various placements, only origin placements give the

very Interesting....

Cheers

8. ### Robert BaerGuest

Then explain why the CIRCLE (0.496 2.842) (0 0) gives the *same* results.

9. ### Robert BaerGuest

Well, the "help" indicates that is a diameter...contrary to what you
say. Vary parameters in the second set and see no or little change.

10. ### Robert BaerGuest

NOT what the "help" sez....Syntax CIRCLE • •.. [center, circumference]

11. ### Robert BaerGuest

So the work-around would be to generate wanted circle at 0,0 and then
move it to correct place.

12. ### John SGuest

Notice it says circumference. Center is a pair of numbers. Circumference
is a pair of numbers. Diameter or radius would be a single number.
Circumference is a POINT (x,y) on the circles CIRCUMFERENCE.

13. ### John SGuest

As I said above, it defines the same circle because both (0 0) and (0 1)
define the (x y) coordinates on the same circle's circumference.

14. ### John SGuest

Help says nothing about the diameter. It indicates a coordinate pair on
the circumference.

15. ### John SGuest

I gave an example to show how it is done.

16. ### John SGuest

That is one way to do it. But, I gave an example to show you how to do it.

17. ### John SGuest

It says ...[center, CIRCUMFERENCE]. That means two sets of coordinates.
Let me try this another way...

What is the radius of a circle whose center is at (0.496 2.842) and
whose circumference passes through (1 0)? Does the same circle's
circumference just happen to pass through (0 0)?

Now try CIRCLE (0.496 2.842) (1.496 2.842) and use the info button to
read the circle's radius. You will see that it is 1 inch. That's because
the circumference passes through (1.496 2.842). As you can see, the
horizontal value 1.496 is one inch greater than 0.496 and the y
coordinate has not changed.

This is the way Eagle has done it for over 10 years. It is not the usual
way CAD programs work, but there you have it.

18. ### Robert BaerGuest

Words from one "radius", words from another "circumference", words
from "help" is "circumference" with ZERO examples.
Results from experimentation so far totally inconsistent with any
interpretation.

19. ### Robert BaerGuest

Dew tell.
Draw a circle with center at x=0.496, y=2.842 and circumference
crossing x=0, y=0.
Now draw a NEW circle with center at x=0.496, y=2.842 and
circumference crossing x=0, y=1.