#robotics Logs

Feb 02 2020

12:48 AM rue_mohr: ok I'm back
12:53 AM rue_mohr: there were no disasters
12:53 AM rue_mohr: challanging fixture to put in tho!
12:53 AM rue_mohr: ok, maybe the fpga stuff finished compiling while I was gone
12:53 AM rue_mohr: where is my tea
01:05 AM Jak_o_Shadows: Oh yeah, Tom_L, there is a config sequence you gotta get right for the OLED as well
01:05 AM Jak_o_Shadows: I can imagine the e-ink wouldn't be any easier
01:29 AM mun: anyone know if a vacuum pump like this can be reliably used as a compressed air pump? i'm trying to drive a hydraulic cylinder. https://bit.ly/2SbJxd9
01:30 AM rue_shop2: hmm
01:30 AM rue_shop2: if you want pressure, I'd find a pressure pump
01:31 AM rue_shop2: vaccum pumps may only be able to take 14psi
01:36 AM mun: right
01:37 AM mun: any reason why vacuum pumps give less pressure than pressure pumps?
01:38 AM Jak_o_Shadows: I mean, vacuum pumps probably don't have hte same kind of flow rate/duty cycle?
01:38 AM Jak_o_Shadows: Get the vacuum down, then you just have to maintain it
01:38 AM rue_shop2: a vacuum pump does not need to be designed for more than 14psi
01:39 AM rue_shop2: thats the absolute max pressure diff it could ever have
01:39 AM rue_shop2: a car tire pump could be rated for 150psi
01:40 AM mun: how come the ceiling is 14psi?
01:40 AM rue_shop2: thats what air pressure is
01:40 AM rue_shop2: that your breathing
01:40 AM rue_shop2: space is 0
01:41 AM mun: but can't it be designed for more than 14psi?
01:41 AM rue_shop2: its probably not
01:43 AM mun: right
03:10 AM Tom_L: Jak_o_Shadows, OLED was what i was referring to
03:47 AM Jak_o_Shadows: This one, a SSD1306 doesn't seem so bad
03:58 AM deshipu: you have to reset the oled with the reset pin a short time after powering it up, otherwise it will display random pixels
03:58 AM deshipu: some of the ready modules have a transitor on them that does that for you
03:59 AM Jak_o_Shadows: eh. This one has RAM backing
03:59 AM Jak_o_Shadows: so you just program blanks in
03:59 AM deshipu: all of them have ram backing, problem is, writes to that ram don't work until you do that reset
04:04 AM Jak_o_Shadows: The one I have does not have a reset pin
05:22 AM mun: i'm reading this page about vacuum pump vs venturi for a pick and place system. there's this paragraph which i don't quite understand: "The pump will run continuously with the vacuum being turned on and off via a vacuum solenoid valve. The venturi will run only when required (during the lift part of the cycle), turned on and off using a compressed air solenoid valve."
05:22 AM mun: https://fluidpowerjournal.com/pump-or-venturi/
05:22 AM mun: anyone know why the pump has to run continuously?
05:23 AM mun: oh, nevermind
05:24 AM mun: but the vacuum pump setup could have a valve as well, right
08:44 AM BitEvil is now known as SpeedEvil
10:46 AM mun: i'm reading this article about venturi vs pump: https://fluidpowerjournal.com/pump-or-venturi/
10:46 AM mun: it says, for a pick and place application, "The pump will run continuously with the vacuum being turned on and off via a vacuum solenoid valve. The venturi will run only when required (during the lift part of the cycle), turned on and off using a compressed air solenoid valve."
10:46 AM mun: the argument is that the venturi is more efficient
10:47 AM mun: but why does the vacuum pump need to be switched on 24/7? can't it be switched off after the solenoid valve shuts?
11:10 AM rue_bed: http://www.kiblerelectronics.com/bob/app_notes/note11/images/schematic1_zvs_driver.png
11:11 AM rue_bed: https://i.ytimg.com/vi/NVfw2gXysV0/maxresdefault.jpg
11:11 AM rue_bed: https://i.stack.imgur.com/m6WAa.png
11:12 AM rue_bed: mun, because they didn't do it with a vacuum accululator and a valve
11:13 AM rue_bed: mun, part of the reason for using a venturi is that most other things run from air pressure, so a venturi is more compatible with existing equipment
11:13 AM rue_bed: if that made sense...
11:13 AM rue_bed: everyone has a shop compressor, nobody really has a shop vacuum pump
11:14 AM rue_bed: venrutis are horridly inefficient
11:14 AM rue_bed: but convenient
11:14 AM rue_bed: who the heck would call me at 8am on sunday
11:15 AM rue_bed: ok, I need to get up and play motor driver
11:15 AM rue_bed: I need an ir2110 application sheet
11:17 AM mun: rue_bed the argument that venturis are more efficient because they can be switched off during the transfer...
11:19 AM rue_bed: a vacuum pump with a regulator and a valve is MORE efficient energy wise
11:19 AM rue_bed: I think a good venturi is like 30% energy efficient?
11:21 AM mun: yeah, if efficiency = (output pressure)/(input pressure)
11:22 AM mun: i've seen a few claim to be around 50%
11:22 AM rue_bed: talking input watts vs output watts, but ok
07:03 PM logb0t_ is now known as logb0t
07:46 PM SpeedEvil is now known as Guest21098
09:31 PM rue_shop1: so, this is cool
09:31 PM rue_shop1: I put away power supplies for a large cnc machine
09:31 PM rue_shop1: for the motors I have planned, I need 20A supplies each, at about 24 - 30V
09:32 PM rue_shop1: I'd stashed away, for a large cnc machine, 4 24V 25A power supplies
09:32 PM rue_shop1: :)
09:36 PM BitEvil is now known as SpeedEvil