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how to sense angle of movement
Posted 05 November 2011 - 10:03 AM
I am trying to coach a science team in a high school. During their robot building, I would like to teach them a way to remember the robot position. That will require remember all the angles of each joint.
But I don't know what sensor to use to measure the joint position - cheap and reliable. Any suggestion is welcome.
Posted 05 November 2011 - 11:00 AM
Posted 05 November 2011 - 05:49 PM
Posted 06 November 2011 - 12:16 AM
Posted 07 November 2011 - 10:22 AM
Step motors can be handled in much the same way but there is a possibility that the system will not always move all the step supplied to the motor (if the unit hits some obstruction for example).
If RC servos are used for the joints the feedback pot is already built into the servo. That is probably your best bet for your project and should give reasonable (but not great) resolution.
Posted 07 November 2011 - 12:41 PM
Even if it can't be adapted, it would be a learning experience to tear down the seat.
Edited by Lou Apo, 07 November 2011 - 12:42 PM.
Posted 08 November 2011 - 01:32 AM
Lou's idea to reference car seat is not bad. Just there is no junkyard nearby. I would guess car seat using encoder to remember the position. It might be easier to get a service manual to check.
I have to talk to kids about the possibility. Although some of them took Java programming classes, programming Arduino in C is probably little too hard. They don't have a lot of budget, either.
Posted 08 November 2011 - 07:57 AM
Posted 09 April 2013 - 03:09 PM
optical/rotary/shaft encoder (call them what you want)? Might get expensive for multiple joints - perhaps on the joints with limited movement you might be able to get away with a variable resistor?
- Encoders http://www.digikey.c...=rotary encoder
- Thru-Shaft Position Sensor http://www.digikey.c...3280-ND/1956410
- SoftPot rotartypotentiometer (if your robot pushes on this as it rotates, it's angular position is given simply by measuring resistance or voltage). https://www.sparkfun.com/products/8678
- Stepper motors do not require encoders in order to know their absolute position (but not sure if practical solution for you). A great mfg is Lin Engineering (http://www.newark.co...lues=422+200066
Posted 10 April 2013 - 07:38 PM
Stepper motors do not require encoders in order to know their absolute position (but not sure if practical solution for you).
Not true. They have the same problem as 2 channel encoders and are incremental. As one example steppers are used in printers and drive to one end or the other where a sensor is used to determine when it has reached that position. Then all moves are relative to that. They have the additional problem that they can miss steps if driven too fast or they meet resistance (encoders don't have the missed steps issue).
The easiest/cheapest way is probably to use RC servos. They use a built in pot to determine position. But that might not meet all your other requirements...
Edited by JimS, 10 April 2013 - 09:01 PM.
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