current set resistor question

[m8kingit]

I'm using 5 amp motors, so according to this formula i need 117k ohm resistors. I'm told they don't make such a thing. Is it possible that i can use a 120k ohm resistor without any issues?
Gecko 201's
Thanks
Mark

[H.O]

Yes, you can use 120k without any problems. The difference is only ~2.5% which is within the 5% tollerance of standard resistors anyway - besides, it's not THAT critical. Good luck!

EDIT: If you're picky, grab a bunch of 5% 120k resistors (Brown Red Yellow Gold), measure each of them and pick the one closest to 117k.

[m8kingit]

Originally Posted by H.O Yes, you can use 120k without any problems. The difference is only ~2.5% which is within the 5% tollerance of standard resistors anyway - besides, it's not THAT critical. Good luck! EDIT: If you're picky, grab a bunch of 5% 120k resistors (Brown Red Yellow Gold), measure each of them and pick the one closest to 117k.

Thank you. I do appreciate your quick response. Do you have any experience or knowledge with the c-11g bob. My next question involves wiring the bob to the speedmaster vfd. The first question will be easy. I purchased a small power supply to power the bob, however it has two outputs 5v and 12v. I'll need both one for the logic and the other for the analog to the vfd. My question is that this particular power supply shares a common ground, should i or should i not consider using this common ground for both, or should i just consider getting another power supply for the other voltage?
Thanks
Mark

[H.O]

Without knowing more about your particullar VFD I would suggest NOT to use the 12V from that power supply if it shares its ground with the 5V.

Usually the VFD has an auxillary voltage that can be used to power external things like this. Usually it's 24V but a simple 7812 voltage regulator and two small capacitors would take care of it. (That's how I'm doing it on my C11 and my Siemens VFD).

[m8kingit]

Originally Posted by H.O Without knowing more about your particullar VFD I would suggest NOT to use the 12V from that power supply if it shares its ground with the 5V. Usually the VFD has an auxillary voltage that can be used to power external things like this. Usually it's 24V but a simple 7812 voltage regulator and two small capacitors would take care of it. (That's how I'm doing it on my C11 and my Siemens VFD).

This is a cnc masters mill. They had some sort of integrated card attached to the inverter, which sounds like what you've described. I'm lost when it comes to electronics, very newbie.

So are you using the power from the inverter to power the analog signal on thc-11g board?

[H.O]

Yes, my inverter provides 24V which I'm using to power the analog section of my C11 board (note that I don't have the C11G, just a plain C11 but I don't think the 0-10V output is any different).

So basically, instead of a separate 12V supply for the analog section the VFD supplies 24V to regulator which outputs 12V to the C11. This keeps everything separated.

Attached are two pages from my schematic. The first page shows the VFD, in the top middle section you can see the 24V and GND (0V) connections comming "out" of the VFD and going to the right, ending in small arrows.

These arrows points to the second page, which shows the C11 break-out-board. The 24V goes thru the 12V regulator and then feeds the analog section of the C11. The 0-10V signal leaves the break-out-board and returns to first page, entering the VFD on its AD1+ and AD1- connection. (Don't worry about the rest....)

Does that make sense?

/Henrik.

[m8kingit]

Originally Posted by H.O Yes, my inverter provides 24V which I'm using to power the analog section of my C11 board (note that I don't have the C11G, just a plain C11 but I don't think the 0-10V output is any different). So basically, instead of a separate 12V supply for the analog section the VFD supplies 24V to regulator which outputs 12V to the C11. This keeps everything separated. Attached are two pages from my schematic. The first page shows the VFD, in the top middle section you can see the 24V and GND (0V) connections comming "out" of the VFD and going to the right, ending in small arrows. These arrows points to the second page, which shows the C11 break-out-board. The 24V goes thru the 12V regulator and then feeds the analog section of the C11. The 0-10V signal leaves the break-out-board and returns to first page, entering the VFD on its AD1+ and AD1- connection. (Don't worry about the rest....) Does that make sense? /Henrik.

I'll have to look at the manual on mine and see if this is possible for me to do. i like that pretty neat

[m8kingit]

Originally Posted by H.O Yes, my inverter provides 24V which I'm using to power the analog section of my C11 board (note that I don't have the C11G, just a plain C11 but I don't think the 0-10V output is any different). So basically, instead of a separate 12V supply for the analog section the VFD supplies 24V to regulator which outputs 12V to the C11. This keeps everything separated. Attached are two pages from my schematic. The first page shows the VFD, in the top middle section you can see the 24V and GND (0V) connections comming "out" of the VFD and going to the right, ending in small arrows. These arrows points to the second page, which shows the C11 break-out-board. The 24V goes thru the 12V regulator and then feeds the analog section of the C11. The 0-10V signal leaves the break-out-board and returns to first page, entering the VFD on its AD1+ and AD1- connection. (Don't worry about the rest....) Does that make sense? /Henrik.

Henrik, If i showed the pdf of my vfd, do you think you could help in getting it wired to my c-11g. They give a schematic, but a few things aren't real clearto me, i'm not and electronics person.
Thanks
mark

[m8kingit]

Originally Posted by m8kingit Henrik, If i showed the pdf of my vfd, do you think you could help in getting it wired to my c-11g. They give a schematic, but a few things aren't real clearto me, i'm not and electronics person. Thanks mark

There was another three wire method shown in the attached pdf, but for some reason it wouldn't allow me to attach it. I tried resizing, but still to no ado. See what you think, let me know if you can help.