#robotics Logs

Dec 09 2012

03:34 rue_shop3 the 555 output is 11V p-p, lose about a volt in the rest of it
03:35 Triffid_Hunter charge pump eh
03:35 rue_shop3 yup
03:35 rue_shop3 need -12V on buddy for the rs232
03:35 rue_shop3 how to get it into the SBC is another matter
03:37 rue_shop3 !time
03:37 tobbor My watch says its 01:26AM Sun Dec 09 2012
03:42 Triffid_Hunter rue_shop3: that's basically how the max232 works. -10 is plenty, max232 only puts out +/-9 or so
03:45 rue_shop3 the max232 only outputs +-10
03:45 rue_shop3 but its inverting from 5 too
09:48 Tom_itx rue_mohr, maybe i should send you one of these PC104 PSUs
09:51 Tom_itx http://tom-itx.dyndns.org:81/~webpage/SBC/sbc1.jpg
09:51 Tom_itx the one on the right
13:06 rue_bed nope, dont need it
15:26 Ademan I'm interested in getting started with robotics, I have a few boards with GPIO pins that I know how to program, some rudimentary EE experience, and a desire to learn. With that in mind, does anyone recommend a low-ish cost servomotor I could buy a few of to reuse in various projects and/or screwing around? Since the plan is to reuse them I assume I should get 180 or 360 degree servos.
15:48 Triffid_Hunter Ademan: I'm partial to MG996 these days.. haven't opened one up to check possibility of modifying for continuous rotation, but they're extremely strong and run around $10-12/ea from hobbyking and similar outlets
17:35 Ademan Triffid_Hunter: thanks!
17:53 rue_shop3 drat
17:53 rue_shop3 eagle cant produce milling outlines for board worth a damn
17:59 rue_shop3 useless without an hpgl editor
18:13 Ademan man... thingiverse has a love affair with M3 socket head cap screws...
18:27 Ademan I understand that it's typical to use PWM to control servomotors, is is possible to "read" the current location of a servo? I understand the feedback loop is closed, but it seems like it would be useful for the main board to be able to say "hey rotating to this position isn't, for whatever reason, working"
19:00 Triffid_Hunter Ademan: no. you have to open it up and tap the feedback potentiometer
19:00 Triffid_Hunter Ademan: or alternatively, find the feedback osc output which might be more stable, there's zero guarantee that the pot is hooked up as a divider
19:00 Triffid_Hunter Ademan: if you want to read position, you want a fancy digital pot which will run a lot more than $12/ea, or reimplement the servo yourself with suitable outputs
19:01 Triffid_Hunter Ademan: if you just want arrived? yes/no then monitor current
19:01 orlok ahh, hobby servos.
19:04 Ademan Triffid_Hunter: hrm alright, that makes sense but is unfortunate. Thanks.
19:04 Ademan It's not an immediate worry of mine anyways
19:18 Triffid_Hunter Ademan: the way a hobby servo works is that on the rising edge of the input pulse, it starts a monastable timer with the position sense pot. it then ANDs each pulse with the inverse of the other and feeds the results to pulse extenders which connect to the motor h-bridge. if one pulse is longer than the other, it causes the motor to turn in that direction for a moment
19:19 Triffid_Hunter digital pots use a microcontroller or ASIC which allows somewhat finer control, smaller dead zone and less hunting since it can run the feedback a lot faster
20:45 rue_mohr I just found out that the $40 mp3 player I lost would cost $60 to replcae
20:46 rue_mohr I bought a lesser one and it wont take a charge
20:46 rue_mohr FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
20:47 Tom_itx give it overnight
20:47 Tom_itx i had one i ran thru the wash that did that
20:47 Tom_itx but finally charged
20:54 Tom_itx working on a pin board for the 2560 so i can add stuff to it easier
21:40 rue_mohr there was a nortel 'release' button on the deck
21:40 rue_mohr the cat puked on it
21:40 rue_mohr I think thats funny somehow
21:41 rue_mohr the mp3 player has been missing for 2 weeks