confused about external driver and wiring

Posts: 24
Joined: Fri May 18, 2018 1:11 pm

Re: confused about external driver and wiring

Post by ckoppenaal » Mon Feb 10, 2020 1:31 pm

ckoppenaal wrote:
Wed Feb 05, 2020 12:44 pm
GeoffS wrote:
Tue Feb 04, 2020 12:23 am
ckoppenaal wrote:
Mon Feb 03, 2020 12:40 pm
''You need to take the 5v from the rpi or you loses your reference and never know the voltage.''

I don't really understand what this means. The 5 volt power supply never changes. What do you mean by '' lose reference''?

Is this how you have it wired up?
You only show +5V coming from the 5V supply, where does the other connection on the 5V supply go to? It needs to be connected to a common ground point on the controller i.e. pi or pi hat. If not, you won't be getting 5V on the stepper driver.
That is how I have mine wired up and it works great?
I looked at my set-up again and I forgot that I am also using the 5v power supply to power the PI. Maybe that is how it is able to work?

Posts: 26
Joined: Tue May 09, 2017 11:12 am

Re: confused about external driver and wiring

Post by ljungberg » Tue Feb 18, 2020 11:20 pm

GeoffS wrote:
Mon Feb 10, 2020 1:36 am
ljungberg wrote:
Sat Feb 08, 2020 1:25 am

well you are lucky then. its probably one in a million.
its like this.
take a friend with you and stand in a steep hill.
you have a tank of water each with you.
its five meter high, this five meters of water can is known and can be measured at he bottom of the water tank.
if you walk upp the hill from your friend both will still have 5 meters of water pressure in their own water tank at the bottom of the tank.
now blind fold your friend, empty his tank and attach a garden hose at the bottom of each tank.
now if you walk up the hill the pressure in your friends tank will rise, if you walk bellow him it will be less.
only if you stand at the same high as your friend he will have 5 meter of water pressure.
its kind of the same your friend never knows if you are standing 20 meter above him or 2 bellow him.

i cant remember what or why this fenomen is called or precisely how it works.
i have at least a few books explaining it at home, but in my work this information is not needed, you only need to accept its true.
I fail to see how this is in any way relevant to the previous posts. What's the point you're trying to make here?
an easy way to explain about why you cant take just a 5v+ and not a gnd.
think its called floating voltage

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