#robotics Logs

Aug 15 2019

01:47 AM rue_mohr: heard of 'motion'?
01:52 AM rue_mohr: software package
05:07 AM veverak: good thing
08:39 AM D4mned: hello
08:43 AM D4mned: i have an old broken rc truck that i want to controll with a raspberry pi
08:43 AM D4mned: the truck uses 2 12v dc brushed motors and a servo
08:44 AM D4mned: iam planning on hooking the motors to motor driver l298n
08:44 AM D4mned: now my question is will i need a speed controller board for the motors too
08:44 AM D4mned: does brushed motors require a speed controller ?
08:45 AM D4mned: or is that what the motor driver for
09:05 AM ib0t: theoretically the l298 is a speed controller for a dc motor
09:05 AM ib0t: but I think it can handle to less power for your motors
09:06 AM ib0t: so the better idea would be perhaps to use a speed controller instead of the l298
09:07 AM D4mned: so brushed motors can be hooked on brushed motors ?
09:07 AM D4mned: so speed controllers can be hooked on brushed motors ?*
09:08 AM ib0t: yeah you can buy speed controllers where burshed motors can directly be driven by
09:09 AM D4mned: thank you very much
09:13 AM ib0t: you can also use a H-Bridge which can handle larger currents and a PWM as an input, than you has built a speed controller by your self
09:13 AM D4mned: that l298n is H bridge
09:14 AM D4mned: but i guess it would be running the 12v motors on 5v
09:15 AM ib0t: yeah but it can only handle 4A and usually rc truck dc motors use more current sometimes
09:15 AM ib0t: and than the smoke will come out of your l298n
09:15 AM D4mned: lol
09:15 AM D4mned: yeah
09:15 AM D4mned: which h bridge would u suggest for me to use ?
09:16 AM ib0t: the output voltage of the l298n will be equal to the input voltage and it can handle up to 46V so this would not be the problem
09:17 AM ib0t: not adhoc I think you have to make a little research by yourselv
09:17 AM D4mned: yeah
09:17 AM D4mned: its my 1st time messing arround with this stuff
09:19 AM ib0t: perhaps you can use a VNH5019 it can handle up to 30A peak
09:19 AM ib0t: I also used such a controller to run a rc car
09:20 AM D4mned: cool
09:20 AM D4mned: it feels like iam biting more than i can chew
09:21 AM D4mned: but i just wanna do it
09:21 AM D4mned: thank u for ur help
10:41 AM D4mned: i tested the motors with a multimeter to check the A withdrawal
10:41 AM D4mned: it sucks 1.3A withload
10:42 AM D4mned: like i blocked it with my hand and it sucked 1.3A
10:42 AM D4mned: and while its running free it registered 0.50A
10:42 AM ib0t: okay perhaps it is a much smaller truck as I aspected
10:43 AM D4mned: yeah
10:43 AM D4mned: i just dont know on how many volts should i run them
10:43 AM D4mned: i tried with a 12v
10:43 AM D4mned: it sounded like its working okay
10:43 AM D4mned: and not over heating
10:44 AM ib0t: the voltage you give is proportional to the rotational speed of the motor
10:44 AM D4mned: yeah
10:45 AM ib0t: and the current is proportional to the torque
10:46 AM D4mned: excuse my stupid question :$
10:46 AM D4mned: but this H bridge the l298n
10:46 AM D4mned: how many volts would it be running the motors at
10:46 AM D4mned: if i got it connected to a 12v
10:46 AM ib0t: with the voltage you give to the input
10:47 AM D4mned: i read that it had a regulator that regulate to 5v
10:47 AM D4mned: okay
10:47 AM D4mned: awesome
05:57 PM gartt: rue_mohr: Ah yes, you mean "motion" for the Pi? From my reading it seems the best way to go. Pi + Pi camera and motion
06:02 PM gartt: ~35 Pi 3, $30 camera that's guaranteed to be compatible with the Pi, sounds good to me
06:13 PM logb0t_ is now known as logb0t
06:34 PM D4mned: hello
06:36 PM D4mned: so 2xmotors 6v running on a motor driver + raspberry pi 3 + 2 servos + raspberry pi cam module
06:36 PM D4mned: what would u suggest to power up all of that
07:19 PM Tom_L: hydrogen reactor
07:23 PM flyback: + flyback surge diodes to protect the rpi if the motor vomits
07:24 PM * flyback bites D4mned
07:24 PM D4mned: :o
07:25 PM flyback: ALWAYS
07:25 PM flyback: USE
07:25 PM flyback: PROTECTION
07:26 PM D4mned: i was just looking at this https://cdn.instructables.com/FYE/O8QZ/H21CGJYJ/FYEO8QZH21CGJYJ.LARGE.jpg?auto=webp&frame=1&width=329&fit=bounds
07:26 PM flyback: FLYBACK DIODES OWN YOUR "CANUCK"
07:26 PM D4mned: and wondering why is he using diodes
07:26 PM * flyback DROPKICKS rue_*.*
07:26 PM D4mned: they are diodes right ?
07:26 PM D4mned: lol
07:26 PM flyback: YES
07:26 PM flyback: ONE for each direction per wire it looks like
07:27 PM flyback: probably avalance or zener in this case
07:27 PM flyback: so they don't short the thing out
07:27 PM D4mned: iv only soldiered twice in my life
07:27 PM flyback: they will only conduct if the voltage goes over
07:27 PM D4mned: and its been in the last week
07:27 PM flyback: it's ok
07:27 PM flyback: use a breadboard
07:27 PM flyback: only downside is speed limits
07:27 PM flyback: see any time you charge a coil
07:27 PM D4mned: yah :D
07:27 PM flyback: relay
07:27 PM flyback: motor
07:27 PM flyback: loop of wire
07:28 PM flyback: when y ou cut off the power the collapsing field produces a reverse high voltage pulse
07:28 PM D4mned: oh
07:28 PM D4mned: and it burns stuff !
07:28 PM flyback: so the diodes direct it to ground
07:28 PM Tom_L: back emf
07:28 PM D4mned: yeah
07:28 PM flyback: now since he's going both ways like Tom_L
07:28 PM flyback: you have to use avalanche or zener
07:29 PM D4mned: lol
07:29 PM * flyback ducks
07:29 PM D4mned: hahaha
07:29 PM flyback: they won't conduct normally unless you go over voltage
07:29 PM flyback: so if you have 5v circuit you would use like 5.5 or 6v ones
07:29 PM flyback: think of it this way
07:30 PM Tom_L: 2x
07:30 PM flyback: suspend a 1 ton safe 50 feet on a pole above your head
07:30 PM flyback: now kick out the pole
07:30 PM Tom_L: back emf is 2x v
07:30 PM * Tom_L kicks flyback
07:30 PM flyback: yeah but you only need it to trigger above a cetain amount
07:30 PM flyback: then it will ground and the voltage won't rise anymore
07:31 PM D4mned: cool
07:31 PM D4mned: thank u !
07:31 PM flyback: you don't want a 10v zener that's it will rise to 10v before it's ground out
07:31 PM flyback: that's going to fry shit
07:31 PM flyback: yep
07:31 PM flyback: that's a common mistake first timers make
07:31 PM flyback: not using flyback diodes
07:31 PM Tom_L: diode rated current must exceed the current
07:31 PM flyback: and their chip burns out pretty quick
07:31 PM D4mned: yeah
07:32 PM flyback: they are cheap it's not a big deal
07:33 PM flyback: yeah he;s right about t he current rating though
07:33 PM flyback: hmm that's a 3v circuit so probably a 4v or 5v zener or avalanche
07:34 PM flyback: ask ##electronics Tom_L and others to confirm the correct set point
07:34 PM D4mned: excuse my ignorance :$
07:34 PM flyback: you aren't ignorant at all
07:34 PM D4mned: so if its 6v i have to get a 7v diode ?
07:35 PM flyback: yeah otherwise since you are going both directs
07:35 PM flyback: and he has 2 diodes per wire
07:35 PM D4mned: yeah
07:35 PM flyback: you can't just use normal diodes that only conduct in reverse the oppositve polarity of whatever the motor is
07:36 PM flyback: tbis is both polarities on the motor
07:36 PM flyback: so you can't have normal diodes they would short
07:36 PM flyback: you need ones that only conduct xxx above normal voltage
07:36 PM flyback: such as a motor field collapsing
07:36 PM flyback: checking
07:37 PM D4mned: yeah
07:37 PM flyback: wrong voltage but example
07:37 PM flyback: https://www.ebay.com/itm/DL403-Surge-Suppressor-Diodes-Hard-to-Find-Diode-25-Lot-Great-Price/291527954141?hash=item43e06b8edd:g:AAIAAOSw9N1Vu4Pt\
07:38 PM gartt: flyback: The reverse pulse is enough to damage the Pi?
07:38 PM flyback: yeah
07:39 PM flyback: the chips have protection but it's not designed to be continiously pulsed it will heat up and burn
07:39 PM Tom_L: naw it just opens the blue smoke door
07:41 PM flyback: oh wow they have bidir tvs diodes?
07:42 PM flyback: https://www.ebay.com/itm/QTY-100-P6KE6-8A-LITTELFUSE-DO-15-UNIDIRECTIONAL-TVS-DIODES-6-8V-600W-ROHS/111669513037?epid=1304665795&hash=item1a00058b4d:g:cMEAAOSwBahVUo4E:sc:USPSFirstClass!15010!US!-1
07:42 PM flyback: close to what you need
07:43 PM flyback: they have a 4v tvs but can't find it in thru hole
07:44 PM flyback: wow they are cheaper than I thought
07:45 PM * flyback adds some to his mouser order he is placing soon
07:49 PM flyback: I am not the expert on what is the right one to use
07:49 PM flyback: so ask around
07:54 PM flyback: tvs are espically made for surges etc
07:54 PM flyback: might not need that for just a small motor
07:54 PM flyback: but you do need some kind of surge surpress