scribbler stall sensor question
Hi, I recently got a scribbler and have a question about the stall sensor for the motors.· My robot will get hung up and try to push itself forward even when its path is blocked.· It takes quite a bit of resistance and motor slow-down to trigger the stall sensor so that the robot will, say, move backwards and turn around.· Is this typical?
Related, there is a sample program in the introductory programming guide for this robot that lets you use the DEBUG command to see the state of the stall sensor.· This is neat.· My observation after running the program was that if I let the motors run full blast forward or backward and tried to stall them with my hand, I could see the stall sensor change from 0 to 1.· But you had to really slow them down before it would trigger.··If I ran the motors slowly and then try to manually slow the wheel down the stall sensor would never trigger.
It is fun to let the robot loose on the floor and see what it does, but it tends to get hung up if it cant tell its stuck.· I wonder if someone with more experience could advise me if this is normal operation or if there is a way to increase stall sensor sensitivity.
Thanks,
Jeff
Post Edited (Jeff11) : 1/7/2008 9:48:22 PM GMT
Related, there is a sample program in the introductory programming guide for this robot that lets you use the DEBUG command to see the state of the stall sensor.· This is neat.· My observation after running the program was that if I let the motors run full blast forward or backward and tried to stall them with my hand, I could see the stall sensor change from 0 to 1.· But you had to really slow them down before it would trigger.··If I ran the motors slowly and then try to manually slow the wheel down the stall sensor would never trigger.
It is fun to let the robot loose on the floor and see what it does, but it tends to get hung up if it cant tell its stuck.· I wonder if someone with more experience could advise me if this is normal operation or if there is a way to increase stall sensor sensitivity.
Thanks,
Jeff
Post Edited (Jeff11) : 1/7/2008 9:48:22 PM GMT
Comments
How many seconds does it take for your stall sensor to be triggered?··On mine it·ususally takes a few to several seconds of resistance and motor slow-down to kick in.·Does it detect stalls sooner on hard floors or on carpets? Is wheel-slip a factor? If it was sensitive enough to trigger instantly while running on smooth surfaces,·I'm thinking it would falsely trigger on surfaces with a bit of drag or perhaps while changing direction abruptly when prompted·by other sensor input.
Now I'm not exactly sure why you are not seeing the stall sensor work at all at low speeds.· Some·people were actually experiencing false triggers during low-speed maneuvers such as in the line-following demo, so the stall sensor was taken out of that demo for the default "restore" ·program in version 1.0a of the Scribbler Program Maker GUI.· I·will make some inquiries about the way the stall sensor operates.
Hope you are having fun with the Scribbler otherwise,
-Stephanie Lindsay
Editor, Parallax Inc.
After writing my message I messed around with it for an extended period of time.··I now think it works fine·but is sensitive to the floor it is on and whether it is stuck bad (grinding·stuck)·or just·kind of half-stuck (kind of spinning·stuck).· There are different kinds of 'stuck', and·I·hadnt let it roam around long enough on its own to get a good feel for its operation under a variety of circumstances.···It does seem to be the case that at low motor speeds it may not stall hard enough to trigger the sensor, but this situation is better than the one you describe of stalling too often.· It is actually kind of interesting that it should take·some time to·understand the robots 'character'.
It is a great robot, and·we·are having a blast with it!
Jeff
·
I'm glad it's working fine after all, and that you and your Scribbler are having a good time [noparse]:)[/noparse].
-Stephanie