I understand that the goal of the AR is to be as cheap as possible however it would be so cool if it did not have to deal with the limit switches and the robot know its position at bootup. Are there some reasons @Chris Annin that it does not use them ? Have you you looked into using them before? Is it mostly a cost thing? Or were there design issues that you ran into where the cons outweighed the pros.
top of page
bottom of page
@Redlunn
Sounds like a neat solution with the AMT21s. I see that you found a solution to the turns count problem as well, with the battery. Another solution would be to modify the firmware for the Teensy slightly, to store and retrieve the turns count from the EEPROM (non-volatile memory). Preferably, you would only store it on shutdown, to alleviate the issue of exceeding the maximum rated (100,000) write cycles of the EEPROM in the Teensy board.
Hi Joseph,
My build is using the CUI AMT21 "multi-turn absolute" encoders which communicate over RS485 network. Despite their name, these encoders only retain absolute position for a single turn, the turns counter gets reset on power cycle. I am using them with the encoder power hooked up to battery supply to retain the turns count. I was unable to find a true multi turn absolute encoder that appeared feasible to implement with the AR3/4 mechanical design. Of course, if you can mount the encoder to the joint rather than the motor, then single turn absolute would be sufficient.
Redlunn