#robotics Logs

Mar 28 2019

12:14 AM rue_mohr: I'm using one of the timers, to measure the time between the ticks.
12:19 AM rue_mohr: doing the maths
12:19 AM rue_mohr: but a problem comes up if the encoder is vibrating and not moving
12:19 AM rue_mohr: not quite sure how to get around that one
12:19 AM rue_mohr: the system yields a nice update rate and resolution
04:41 AM veverak: rue_mohr: vibrating?
04:41 AM veverak: as changing direction between pulses?
04:42 AM veverak: afaik encoders usually have two pulse sources, with which you should be able to detect the change in direction
08:30 AM rue_bed: if the motor is just pulsed and the encoder if just picking up on it, it thinkgs its turning'
08:31 AM rue_bed: so yea, I might need to say if the last speed was + or -
08:31 AM veverak: yup
08:57 AM rue_mohr: I suppose as long as the target speed is signed, it would work out
08:57 AM rue_mohr: tho
08:57 AM veverak: well, it has to be signed for this
08:58 AM veverak: :)
08:58 AM rue_mohr: hmmmm yea, its a resonance thing too
08:58 AM veverak: from the description, I sort of expect that it will do something like: -1,1,-1,1,-1,1 on velocity?
08:58 AM rue_mohr: yea, where 1 is at or over the target velocity
08:59 AM rue_mohr: prolly over, cause its making the sign flip
08:59 AM rue_mohr: er, no
08:59 AM rue_mohr: I locked it to only use + values on the motor
08:59 AM rue_mohr: so, its a drive:relax based vibration
03:41 PM SpeedEvil is now known as Guest64462
05:23 PM BitEvil is now known as SpeedEvil
08:57 PM gaze___: @rue_mohr how much can you load a potentiometer diametrically to the shaft and not substantially decrease its lifespan?
08:58 PM orlock: that would depend on the pot
08:58 PM gaze___: with what pots can you get away with it?
08:59 PM orlock: that would depend on the load
08:59 PM orlock: you could just add bearings...
08:59 PM orlock: or have an properly designed load bearing shaft that interacts with a pot
09:01 PM gaze___: the latter option is attractive... I just now need to couple to the pot in a way that is somewhat insensitive to misalignment
09:01 PM gaze___: what's a cheap and cheerful backlash-free way to do that?
09:02 PM orlock: belt
09:03 PM gaze___: yeah maybe that's the move. I'm a bit worried about belt slippage... I guess I could use a full-on timing belt but that seems a little overkill
09:03 PM gaze___: the load is maybe 200-300 g
09:04 PM gaze___: I suppose tape players are able to do this without the belt slipping
09:04 PM orlock: yeah, timing belt is what i meant sorry
09:04 PM gaze___: seems very overkill
09:05 PM orlock: nah?
09:05 PM orlock: and the load isnt actually between the pot and the shaft
09:05 PM orlock: friction drive would probably do it
09:06 PM gaze___: that feels a little better. I should note that I don't need this thing to complete a full rotation.
09:06 PM orlock: yeah, figured that from the use of the pot
09:06 PM gaze___: so maybe a spring loaded lever and cam is the right move
09:06 PM orlock: otherwise i'd be suggesting optical encoders
09:06 PM orlock: repurposing of a mouse scroll wheel maybe
09:07 PM orlock: it will also depend on your adc
09:07 PM gaze___: oh now we're talking
09:07 PM orlock: 10 bit are common, so you get 1024 positions
09:07 PM orlock: also, are you familiar with hobby servo's and how they work?
09:07 PM gaze___: ideally I just make this out of trash
09:08 PM orlock: as it's basically the same thing
09:08 PM gaze___: yeah I've taken a few apart and modified them for continuous rotation and all that, but that was a long time ago
09:08 PM zhanx: orlock,
09:08 PM zhanx: https://imgur.com/a/g8mmFKO
09:09 PM zhanx: home made maple syrup
09:09 PM orlock: eh cool
09:10 PM orlock: so you just boil it off until it thickens?
09:11 PM zhanx: 15galons to 2 liters
09:11 PM orlock: Damn!
09:11 PM zhanx: don't ask me how many gallons are in a liter
09:11 PM zhanx: took my 8 hours 32 minutes
09:11 PM orlock: 1 gallon = 3.7l
09:12 PM orlock: 56 liters damn
09:12 PM zhanx: orlock 500ml here is 6.99 usd for it
09:12 PM orlock: zhanx: just saw this - https://imgur.com/gallery/ynKe9rN
09:13 PM zhanx: dude is stacked for non combat arms
09:15 PM orlock: you mean he has a lot of decoration for not being one of the combat MOS?
09:15 PM zhanx: yes
09:16 PM zhanx: his right chest is the awards
09:16 PM zhanx: well left for him right for you veiwing
10:37 PM rue_mohr: gaze___, I'v not put a lot of load on them consistantly, but I'v never had one wear out
10:38 PM rue_mohr: toothed belt
10:38 PM rue_mohr: you making a servo?