Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Graham Waterworth on January 15, 2006, 10:38:08 AM
-
Hi All,
My lathe has a variable speed controller that is operated by a rotary resistor that has a value of 4K7, my question is, can I connect the wires from the speed control into the parallel port without any other resistors.
Also it has a collar round the spindle with slots in and a infra red detector with 3 wires from it, can I also use these for the pulse count.
Thanks
Graham.
-
I don't think you can hook them in...
-
The voltages on the speed control pot are floating at AC line voltage. Connecting them anywhere without isolation will make a big bang and incinerate things. Lookup Digispeed for more info, I think Campbell is also working on a similar unit.
The optical pickup could be electrically compatible if it was disconnected from the lathe electronics and only hooked to the computer, however you would need to change or modify the slotted wheel on the spindle since Mach is expecting a single pulse per spindle revolution.
Pete C.
-
Graham, I have use Bob Campbells board and it works very very well. (have not test the digispeed yet) I believe the multi pulses will work you just have to tell mach How many per rev. Also a while back Art gave me an alternate hookup for multi pulses I'll look up the notes and see what it was. Terry
-
Graham, Here is the note from Art
>
> > Terry:
> >
> > Most have found one is good enough. 36 may work just as well
> though, if
> > you use the 36 per rotation, feed them into the timing input, not
the
> index
> > input..
> >
> > Thanks,
> > Art
My Boxford lathe has two sets
1 is 1 PPR
2 is 36 PPR.
I know 1 works ok and am still experimenting with 36. (:~)= Terry
-
Sorry folks, I may have been economical with the facts here.
The spindle is DC drive
The drive card is a :-
KB Electronics KBLC-240D (4771B)
Input 115/230 VAC
Output 0-90/180 VDC
Rated 6.0 ADC
I am asking the questions as the KB Elec. site seems to be off line, so this is making it very difficult to fine any data on this unit.
The only site I can find with anything like it is Chinese and I am not fluent in Chinese or Googles translated gibberish.
Thanks
Graham.
-
The speed control pot on that drive is *definately* floating at AC line potential i.e. 120VAC. In order to control these drives from Mach or other software you need an interface that provides both isolation and conversion of the signal from the computer into a control voltage for the drive. Below are two commercial options.
http://www.homanndesigns.com/DigiSpeed.html
http://www.campbelldesigns.com/mach-spindle-speed-control.php
Pete C.
-
Graham the KB website is up !!!! Just came from there Do you have a KBLC or KBIC board?
-
Graham, I looked and I have a D&M mill that uses the same style controller
KBLC-240DS the speed control part of it that hooks to the control board appears to run off of 0-7vdc. I measured it and referenced the manual. There is also several ways it can be controlled with a pot so please check with KB to be sure. It will still take a control interface board such as has been mentioned to make it work. The Campbell board has an adjustable output so you can tune the control to calibrate your RPM.
(:~)= Terry
-
Hi Vmax,
It is a KBLC 240D (4771B) board. I will try the KB Electronics site again.
Graham
-
Vmax - Try measuring the voltages at the speed control pot relative to the AC line neutral. While the control is indeed using low DC control voltages, the entire drive electronics, including those DC voltages is floating at the AC line voltage. You can not connect those control voltages anywhere without isolation and indeed you can be electrocuted working on the "low voltage" control signals if you are not careful.
Remember, everything is relative, and even though the leads on the speed pot only show low DC voltages relative to each other, this does not mean that they do not have a different voltage realtive to something else like ground.
Pete C.
-
I am well aware of floated voltages I retired out of the power industry we worked from 24vdc to well over 500kv. I don't see from looking at the board schematic how you can have that voltage level present at the pot hookup. I double checked the readings from the pot leads to GRND, AC neutral, dc common. Both Aver and RMS. Where exactly is the voltage sourced from that could be present. I do not see it nor can I measure it. Both leads are hooked to a computer mother board and I do not see any means that the manf has isolated it.???? Help me to understand the problem. Now of course if a component failure occured anything is possible. Same is true with any ac/dc conversion where you do not have an isolation transformer to step the needed voltage down before it is rectified.( even then you could have a shorted transformer H-L that is where the chassis grnd comes into play. Not failsafe for sure but if properly connected it is a good safety net. (;~)= Terry
-
Ok lets see if I have this figured out. The Speed control board if completely floated from any reference could be energized at full potential? That "is" a scary thought. I guess I cannot see it here because the board and components are all bonded and cannot float from the reference neutral or common. Definantly something to keep in mind. We always lived by the Checkit before you touch it and groundit or gloveit. Except for those that did barehand work.( Energize yourself to the same potential 500KV and isolate yourself from any reference.) those were the Brave(nutty)ones.
(;~)= Terry
-
Hi,
Just found this thread. :) The speed control potentiometers on these controllers are fed by a DC voltage of approx 14Vdc, derived from a zener diode style regulator.
The positive side of this voltage (P3) basically sit at mains potential. The 0V for the potentiometer sits at mains potential minus 14V. The KBiC controller speed trimpot just sits in series with the manual speed potentiometer to reduce the maximum speed.
As the voltages are around mains potential, you need to have isolation from any control voltage being generated from Mach2/3. This is where the DigiSpeed comes in. http://www.homanndesigns.com/DigiSpeedDeal.html It isolates the PC control voltage from the mains referenced control voltage in the KBIC controller.
Cheers,
Peter.