[Runner4404spd]

i am trying to hook up my geckos and was wondering where to get the common 5vdc? i was wondering if there is any easy way to pull it off the cnc4pc c10 breakout board that i have. or do i have to try and get it directly from the computer power supply? i was really hoping not to have to run another wire from the computer other than the parallel cable. i will be using mach 3 so if there is some way to configure one of the pins please let me know.

thanks
JErry

[Willbird]

I'm running a seperate PC power supply(in my control box) This will provide the 12vdc and the 5vdc My C11g board requires, and the 5vdc for the gecko's. Some folks use Wal Wart transformers, but I had several PC power supplies anyway.

http://www.makezine.com/blog/archive...ench_unit.html


That link explains the basics of the deal :-)

[bill south]

Hey Runner;
I attempted on two different occasions to use a separate power supply to power my 320's and never did get it to work. I think is has something with the grounding of the signal lines and the grounding of the power supply. Heck, don't know but I fourd that if I used an old USP cable, cut off the end, measured for 5 volts on the cut end (once it's plugged into the couputer) and used that to power the 320's, all the old headaches went away. A different cable but an easy fix.
Hope you have better luck than I.
Bill from Spartanburg.
:wave:

[Runner4404spd]

Bill thats what i'm finding as well. i tried using a seperate power supply, my geckos aren't working and i'm wondering if thats why.

keep the ideas coming guys.

[CJL5585]

Guys,
It is really simple.

The positive wire of the 5 volt source goes to the Gecko's.

The common or ground side of the 5 volts must go to the grounds on the breakout board. (That's pins 18 thru 25 on the breakout board and also the same pins on the parallel output port. One should only have to connect to ONE of the ground pins as they are connected on-board in most cases.)

Jerry

[Runner4404spd]

well that clears alot of it up. what your really after is a common ground. i've identified that i'm missing this. but you want the computer and all the power supplies to have a common ground. i will check this out and keep you posted on whether this works or not.

[CJL5585]

well that clears alot of it up. what your really after is a common ground. i've identified that i'm missing this. but you want the computer and all the power supplies to have a common ground. i will check this out and keep you posted on whether this works or not.

Do you want every voltage spike and the noise and trash (EMI) from the acceleration and de-acceleration of the motors getting into your computers logic circuits? Do you have a desire to blow up the computer electronics or parallel port electronics? Don't think so. That is what can happen when the CNC power supplies have a common ground with the logic supplies.

What you DO want is the LOGIC supply (5V) for the Gecko's, the breakout board, and the computer parallel port to have the same common. This is accomplished by connecting the 5v common (sometimes called ground) to the common pins on the breakout board which automatically are connected to the computer logic supply common inside the computer when the breakout board is connected via the DB-25 cable.

The only COMMON GROUND that you need in a system is the EARTH or utility system ground from the power company. It attaches to the equipment enclosure(s) which contains the CNC components. This Earth ground should not be attached to any power supply outputs. It goes only to the input voltage side of transformers and other equipment designed to be connected to the earth ground. If in doubt, read the NEC Codebook, insurance company regulations, the National firecode, and attend a seminar or two on proper grounding techniques for electronic equipment.

[Runner4404spd]

well now i'm confused again. i though that i needed +5V on the common pin on the geckos? if i connect this pin to the ground connections on the breakout board, this will not accomplish this. or will it? someone really needs to make a more clear schematic so us mechanical engineering folk can understand it.

[Al_The_Man]

What you DO want is the LOGIC supply (5V) for the Gecko's, the breakout board, and the computer parallel port to have the same common. This is accomplished by connecting the 5v common (sometimes called ground) to the common pins on the breakout board which automatically are connected to the computer logic supply common inside the computer when the breakout board is connected via the DB-25 cable.

The only COMMON GROUND that you need in a system is the EARTH or utility system ground from the power company. It attaches to the equipment enclosure(s) which contains the CNC components. This Earth ground should not be attached to any power supply outputs. It goes only to the input voltage side of transformers and other equipment designed to be connected to the earth ground. If in doubt, read the NEC Codebook, insurance company regulations, the National firecode, and attend a seminar or two on proper grounding techniques for electronic equipment.

This can be misleading, as there is also a common practice to ground all power supply commons to a ground plate set up in the enclosure which is connected to the incoming service ground conductor, including the PC supply common and all shields, this is something I have practiced for many years and have never had a problem, this includes many PC based systems, using servo's and other equipment.
This method relies on having the lowest resistance path possible to earth ground for all of these components.
Ref: NFPA Electrical Standard for Industrial Machinery.
'Control Circuits shall be permitted to be grounded or un-grounded'.
In any event, you should follow the recomendations by Gecko as the above preferences are my own.
Al.

[CJL5585]

well now i'm confused again. i though that i needed +5V on the common pin on the geckos? if i connect this pin to the ground connections on the breakout board, this will not accomplish this. or will it? someone really needs to make a more clear schematic so us mechanical engineering folk can understand it.

See attached drawing in pdf format.

Jerry

[Runner4404spd]

i have a two transformers running my driver supply. one is set at 24v and the other is a 12 volt supply that feeds a 12volt regulator circuit as well as a 5volt regulator circuit.

i think, i will add a 5 volt transformer in there and divorce the supplies and the attach the ground for the 5volt supply like you have in the pdf.

thanks for the help

[CJL5585]

i have a two transformers running my driver supply. one is set at 24v and the other is a 12 volt supply that feeds a 12volt regulator circuit as well as a 5volt regulator circuit.

i think, i will add a 5 volt transformer in there and divorce the supplies and the attach the ground for the 5volt supply like you have in the pdf.

thanks for the help

The 5 volt supply only needs to be able to furnish about 250 milliamps of current, so the regulated supply would most likely be more than sufficient.

The 5 volt current draw thru the Gecko's is 16 milliamps max for each of the step and direction signals, or 32 ma per drive.

The current per each output on the BOB is also limited to about 20-22 ma.

Jerry

[kentavv]

Regarding commons (aka grounds): consult your breakout board manual for recommendations. Connecting commons across the breakout board will likely prevent the breakout board from providing isolation.

[Runner4404spd]

The 5 volt supply only needs to be able to furnish about 250 milliamps of current, so the regulated supply would most likely be more than sufficient.

The 5 volt current draw thru the Gecko's is 16 milliamps max for each of the step and direction signals, or 32 ma per drive.

The current per each output on the BOB is also limited to about 20-22 ma.

Jerry

the reason for adding a seperate power supply is because the ground from the 5 volt is also tied in with the motor ground as well as the relay ground. i think if i do it this way then i will have two distinct ground loops.