+, -, GND

I understood until now, that electronics, when it uses GND (ground), it means " - " (minus). On a motor I've got, it has a + (plus), - (minus), and GND (ground). What does the GND do? :~

GND is really the reference point. If you are standing at street level, the first floor is one level above ground (so you might call it plus) and the basement is one level below ground (so you might call it minus).

As for your motor, what type is it?

Wouldn't surprise me of the GND tab on the motor goes to the can, so assuming it's brushed you can easily add some caps for suppression.

In a house you would call it the hot,neutral and earth ground You would never use a ground as a neutral although it technically would work ground is more for protection(from say shock or noise) in a circuit you assume - means gnd when it really doesn't, most circuits are simple so people say ground but it is truly negative on a battery you say its the positive and negative terminal, there is no ground terminal maybe only a ground connection on the motor the ground is a connection to the chassis, this would protect you from shock if say the positive wire was touching the chassis and potentially could electrocute you, instead it hits the ground and would trip the overload or watever protection device implemented now gnd in a dual polarity circuit means the common connection point and has no relation to the actual earth ground, so it does get a little confusing in that case it refers to like said before the common reference point, but in this case with a motor it refers to earth ground used for protection that should(but isn't always) at the same potential as the negative leg of the supply

As to Nick Gammon, I have a 1000kv 400xt brushless motor. www.hobbypartz.com/40tyoubrmo.html

The "ground" doesn't actually exist.

It is merely a term used for the point in a circuit at which all voltages are measured with reference to. It is entirely arbetrary what that point is.

Normally the "ground" node of a circuit is that node to which the majority of components are connected to. If there is no such node, then 9 times out of 10 it is taken to be the point of lowest potential in the circuit - for instance the negative terminal of a battery. Other circuits may take that point to be a place where the other voltages in the circuit cancel each other out.

The Arduino (and the Atmel datasheets) actually label things wrongly. They talk of Vcc and GND as pins, which is entirely wrong in every respect. What they should actually be talking about is Vss and Vdd - the source and drain voltages - and all voltages in the data sheet are measured with respect to Vss (Max Vdd above Vss = 5.5V for example). The "GND" pin may not be connected to the same node as you have taken a GND in the rest of the circuit. Vcc itself means "Collector voltage", and is as relevant to a CMOS system (which uses MOSFETs, not BJTs) as the ants crawling up the wall are to the current value of the Dow Jones index.

As far as motors are concerned, the "GROUND" could be many things. For instance:

  • It may be a connection to the metal exterior of the motor, to be used for noise reduction and/or safety.
  • It may be a reference point for applying the voltages to the + and - pins - the motor might be inteligent, and you apply voltage to + and GND for spinning one way, and - and GND for spinning the other way.

Vcc and GROUND are pins… designated places where these Sources are found and connected to. As to VCC most all the people learning here don’t realize that Mosfets are relatively New parts… ALL Logic less than 30 years ago WAS Transistors at that time Cmos was the New kid on the block 40 years ago the Vast majority od electronics produced was still vacuum tubes. Power mosfets were very rare (N Ch) and P Ch were impossible smalll low current devices that were difficult to use as they were most fragile and had Rdson values it the 10’s to 100’s of ohms. I can clearly remember CD4017’s that cost $12.00+ each, a CD4022 was 8 dollars in 1972 and a CD4011 was $2.31 and I was making 7.25/hr I got a raise to 9.00/hr and thought I could buy the world (It’s a bit over 30.00/hr now)... and pop bottles were worth .02 Ea refund value and a guy could collect 5 of them and buy enough candy to last all afternoon. There were also a great surprising number of people that believed the moon was made of Green Cheese. Luddites were coming into their own… sometimes I wonder if they hadn’t the right of it.

Doc

yosler: As to Nick Gammon, I have a 1000kv 400xt brushless motor. www.hobbypartz.com/40tyoubrmo.html

That motor doesn't have +/-/gnd, it has red/black/yellow phases - its a 3-phase sensorless brushless motor.

I do actually need more info on the motor

Idk without a datasheet its hard to say exactly what that motor needs
just says 12v,

MarkT:

yosler: As to Nick Gammon, I have a 1000kv 400xt brushless motor. www.hobbypartz.com/40tyoubrmo.html

That motor doesn't have +/-/gnd, it has red/black/yellow phases - its a 3-phase sensorless brushless motor.

What is a 3-phase sensorless brushless motor??

What is a 3-phase sensorless brushless motor??

See:- www.atmel.com/images/doc8012.pdf

the document is WAY too long and complicated!
In a nutshell please…

Wikipedia it

MarkT: Wikipedia it

Makes a change from "JFGI" I suppose...

the document is WAY too long and complicated! In a nutshell please...

It is a motor. It requires no sensors and has no brushes.

One wire is for each of the phases. You need to supply a three phase signal to make it turn. That is three sin waves 120 degrees apart. The frequency of the sin waves will determine the speed of the motor.

Ground is basically connected to the main switch in house as we do not give ground to every device (some may not need ground so ground do act as negative in devices) so the two wires attached to motor are two,one + and other - which is also ground.

Sorry but that doesn't make any sense and does not address the problem in this post.

I think you are referring to how the physical earth ground in a regular electrical service is connected at the main panel with the neutral, and how essentially grounding the motor casing gives it the same potential as the neutral(hopefully assuming the ground is electriclly clean) and would provide protection from shock in the case of instead of electrifying the outer case due to a failure, the breaker would trip disconnecting power to the circuit however in this case it seems this motor isn't going to be connected to the mains, and so it wouldn't protect it from say the 12v supply shorting to the case, not that that would hurt anyone anyway All your questions could be answered if you were to find the datasheet

There are obviously two different subjects being interleaved in this thread. First is about the definition and usage of the word 'ground' as it applies to electronics. While the OP used it his original posting, it's pretty clear he really wanted to know what/how to wire up a 3 phase brushless DC motor, which has no use for nor applicable to 'ground'. So while most post responces here talking about ground are not incorrect, they are not what the OP really meant to ask for, nor requires to understand what he needs to get his motor to run.

The motor in questions has more in common with a 3 phase AC motor then a true DC motor. It requires a motor driver/controller to generate the proper 3 phase signal at the proper frequency, voltage, and current capacity required for the motor. In reality one never just purchases such a motor without also purchasing a driver/controller module compatible to the actual motor selected. These are usually called ESC, for electronic speed controller. Then one controls the ESC by sending in standard +5vdc servo ppm control pulses. There is usually a start-up 'arming' sequence one has to send to the ESC before the motor will actually obey the servo control pulses, for motor start-up safety. Most ESCs also output a regulated +5vdc power source pin suitable for powering things requiring up to around 2-3 amps for +5vdc loads, this is usually called a BEC feature, for battery eliminator circuit. The main power source for a ESC is usually battery power specified for a certain voltage range and rated to be able to supply the peak current demand for the ESC and motor. Again the main battery, brushless motor, and ESC must be selected as a set to insure they are all of a compatible voltage and current range suitable for the motor.

Lefty