[Robotgroup] BASIC STAMP II EMERGENCY!! (was Robot Head: BS2 Stamp)

[Gray Mack]

If you can make the meeting tonight, bring your stuff and a multimeter and we can troubleshoot it.

Some questions.
What battery voltage are you using?
What stamp board are you using?
Are the servos running directly off the batteries or through a 7805 regulator such as on the Board of Education?

notes on servos:
The standard range for standard servos is 90degrees.
Thus pulses from 1000 uSec to 2000 uSec produce this travel with 1500 uSec being centered.
Most servos can go outside of this range and may be able to do 180degrees or so. 
Going beyond this extent will cause a servo to mechanically stop and the motor will stall and draw excess current and overheat. (Some servos like the Bluebird ones I have will self-destruct immediately.)
So you may be able to use a range or 500 uSec to 2500 uSec but you may want to play it safe at say 600 uSec to 2300 uSec or whatever.

The stamp pulseout command takes values of half this so 500 is about -45deg, 750 is centered, 1000 is about +45deg and the limits would be 300 to 1150 for a 600 uSec to 2300 uSec extended movement.

Your stamp code needs to send pulses about every 20 mSec (20000 uSec), no more than 30 mSec and no less than 10 mSec apart. 

Your stamp code should verify before sending the pulse that it is in the valid range that you set. For example pulseout of 300 to 1150 values, not something like 0 to 1300 values.

Some servos stutter momentarily if you instantly change the pulse value drastically but then should go to the position at max speed. It is best to move from the old value to the new over several pulses.

These rules are what makes having an external servo controller an inviting option based on the BasicStamps capabilities. You can send a position command to it and forget about it until you want movement again.


-Gray


--- On Wed, 8/6/08, LHudson <lhudson73 at yahoo.com> wrote:

> From: LHudson <lhudson73 at yahoo.com>
> Subject: Re: [Robotgroup] BASIC STAMP II EMERGENCY!! (was Robot Head: BS2 Stamp)
> To: "The Robot Group Mailing List" <robotgroup at puremagic.com>
> Date: Wednesday, August 6, 2008, 9:20 PM
> <i>
> Okay the SEND button got sent again for some reason.  For
> those of you who haven't enough to read already,
> here's the rest of it:
> </i>
>  
> Well there wasn't any magic smoke this time.  It just
> stopped working...
>  
> I was doing the Pan and Tilt code that was discussed
> originally on the thread, and it was working for the most
> part.  However, there were limitations to the extent of the
> panning and tilting:  i.e. -- if "650" is the
> center, the panning servo had a range of 300 - 1100,
> and the tilting servo had an even smaller range of 600 -
> 700.  The tilt was noticeable enough for a demo and the
> degree of rotation was perceptible on the webcam, however I
> was trying to push it to 590 - 575, as this angle was
> sufficient enough to see watch Bonnie sitting at the table
> from my office workstation.
>  
> What would happen if I went outside of the established
> boundaries was the same weirdness that I was experiencing
> earlier:  the stamp would appear to "reboot" and
> the initialization sequence would repeat in a loop.  Now,
> if this was the panning servo, it would "bounce"
> the head a few degrees toward the center while the
> initialization LEDs were blinking, and once it established
> the 650 "center" point, the DO...LOOP would
> execute and the SERIN statement could receive for commands
> from the dotNET application.  But, if this was the tilt
> servo, I'd actually have to get up, go to the next room,
> turn off the BOE power switch, re-position the head, and
> then re-start the BOE.
>  
> This went on for a few hours, and then all of a sudden it
> stopped working.  The green LED on the BOE was still on. 
> However the reset button didn't turn on the
> initialization sequence (which causes the LEDs to blink). 
> Most importantly, when I go the Stamp Editor Debug Terminal,
> I get the message "No Basic Stamps found".  My
> first assumption was that the servos were overloaded and
> drawing too much current, which did something to the stamp.
>  
> Now it just occurred to me that it could still be the
> batteries.  I tested them yesterday, and they were all
> "Green" on the battery tester.  However the thing
> has been running nearly non-stop for about a week now, and
> the battery tester is still showing them all as
> "Green", but I am going to try it with a brand new
> pack of batteries and see if that makes a difference.
>  
> Thanks,
>  
> Scott
>