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- so these two guys are having lunch at the worksite
- pisse dher off, oh well nothing new
- one of them is chuckling to himself, the other asks whats so funny
- he says "aw, man, I had the most embarassing Freudian Slip last night"
- the other guy says "what the hell is a Freudian Slip?"
- "it's when you accidentally say what you're thinking about, instead of saying what you're talking about"
- he gets a blank stare, so he says "OK, so last night, I'm taking the subway home"
- and the lady at the ticket counter has the biggest tits I've ever seen. enormous. I couldn't stop staring"
- "so when it gets to my turn, I meant to ask for my change in nickels"
- "instead I asked for my change in nipples"
- lololol
- they both laugh and the other guy says "Ok, ok, I think I get it... I had one of those last night too"
- I'll take the nipples
- "I was at the dinner table with the family, and I meant to say 'honey, please pass the salt"
- "but instead I said "BITCH YOU RUINED MY LIFE"
- oooo tough crowd
- I guess it's better delivered in person?
- OMG I've wanted to say something like that soooo many times over the past 39 years.
- lol
- Yet I would say what the frack did you get yourself into? Well Got a good cook out of the deal anyway.
- lol
- OK, have you ever seen the inside of a stepper motor?
- Did I show you those pics?
- yes
- ok, you remember what makes them different from normal motors
- what happens when you apply a constant current to a NON-stepper motor
- magnets
- lol bingo
- spinning magnets
- normal motor + electricity = spinning
- +-+-+-
- stepper motor + constant electricity = ?
- (hint: from "off" to "on" would be one step)
- positive switches to negative and vice versa
- Yes
- and in a big motor with only a few poles, that's a relatively large rotation
- in a stepper motor, it's a small movement, but very precise
- now, how do we know how many steps a motor has in one revolution?
- By telling it what it is suppose to do
- you're one step early, I think
- The number of steps in a rotation is a physical property of the motor... like the gear ratio in a differential
- no matter what settings you change, how much voltage you apply, the number of steps you need to send to that motor to get one rotation does not change
- now, with some fancy footwork, we can create "pretend" steps in between the real ones
- it's just the speed of which it reaches that full rotation
- I think so... your wording is different, but it sounds like you follow
- So a stepper motor makes steps. There are a fixed number of steps in a rotation, so each step has a fixed step angle
- if you have a 200-step motor, and you send 200 steps in half a second, and then 200 steps over ten seconds
- okay, sorry, step Angle?
- yes
- don't apologize, this is good feeedback for me
- imagine a staircase
- rise height
- you like to build shit, this will be a good analogy
- you have to go up 40'm
- sorry
- 40'
- and you have to build exactly 48 steps
- assuming they're all the same height
- how tall is each step?
- 10 inches per step
- bingo
- now
- this is going to be the most useless staircase every
- lol
- you have to go up 30'
- and you have to build exactly 200 steps
- how tall is each step
- might as well just build a ramp, 1.8"
- now, imagine that same staircase as a ladder instead
- one rung every 1.8"
- now wrap it in a circle
- the whole ladder is 360 degrees
- and there are 200 steps
- each step is 1.8 degrees
- so the step angle is 1.8 degrees
- was that helpful?
- okay.for now it's in there.
- lol, okay
- now every time you send a pulse to the motor, it turns one step
- so in this example, it turns 1.8 degrees
- right
- if you send 100 steps, how far does it turn?
- half way
- bingo
- ok, now we need to translate that ladder into the little black boxes on your printer
- if you send 100 steps to the motor, the shaft will turn one-half rotation
- you still with me?
- so if there are 200 steps in a revolution and one revolution travels 5mm then you would have 80 revolutions in a 400mm x travel. Please be right
- that is correct
- but
- only if the motor travels 5mm in one rotation
- ours do not
- but that statement is correrct
- *correct
- I see where your confusion lies
- I'm going to re-word your statement
- in pieces
- with one small but critical change
- if there are 200 steps in a revolution
- and one STEP travels 5mm
- then 80 STEPS
- would travel 400 mm
- would be 400mm
- does that make sense?
- 'yep
- ok, now
- the reason you got mixed up there
- is becuase you jumped a step
- we need to translate step ANGLE into step DISTANCE
- now, we don't have to think about diameters or pi or any of that bullshit
- because we know two things
- I don't know pi that's one
- sorry
- 1) we're using a toothed belt with ONE tooth every 2 mm
- and 2) the pulley on our motor has EXACTLY 20 teeth
- okay
- so
- if we rotate our motor one HALF rotation, how far does the belt move?
- sorry
- 20mm
- imagine there's a black line on the face of the motor, from the centre of the shaft to the middle of one edge
- like this
- so you need to know the radius too?
- Of the pulley?
- nope
- one sec
- k
- phew
- that was stressful to pull of quickly
- now
- that pulley on the motor has 20 teeth
- and before we send any signals, the red one is lined up with the black line
- still with me?
- yep
- ok
- now, we send 100 steps
- how many teeth go past that black line?
- ooooh you're overthinking it
- I can tell
- back it up, how many teeth on the pully total?
- 20 each 2mm aaprt
- yes!
- okay, now how far does the shaft rotate with 100 steps?
- half way
- yes!
- ok, now, if the pulley is GLUED to the shaft, 1:1 movement, no questions, how many teeth have rotated past that black line after 100 steps?
- 50
- whoops
- try again
- noooooo 10
- YES!
- now, how far apart are the teeth on the belt?
- 2mm
- so how far has the belt moved after 100 steps?
- 20mm
- YES!
- NOW
- Now, how far does the belt move for 10 steps?
- 2mm
- fucking yes
- now
- how far does the belt move for one step
- .2mm
- oh my god, almost there
- now
- how many steps to move one mm
- 5
- ladies and gentlemen, I give you
- steps /mm
- phew
- I enjoyed that
- OMG, I need to copy and paste this to my notepad.
- LOL
- take your time, I need a cigarette
- I'm kidding I don't smoke
- same here, more like a mouthful of nicorrete
- Have a shot of scotch on me.
- damn straight
- let me know when you're ready to continue
- WHAAAA, ALOL
- go for it
- Did you get all that copied?
- No will do it later can only copy and past one message at a time. takes too long
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