Hello Guest it is April 21, 2021, 02:30:29 PM

Author Topic: Setting up Spindle/VFD control Issues  (Read 1845 times)

0 Members and 1 Guest are viewing this topic.

Re: Setting up Spindle/VFD control Issues
« Reply #10 on: February 08, 2019, 07:16:46 PM »
Hi,
yes you could use a simple voltage divider but you can't be sure how much current the G540 will draw and whether it will
be constant. The output voltage of the voltage divider will vary with the current drawn.

The attached is a simple Zener diode regulator with just a diode and a resistor. I'm going to guess that the G540 will draw
10 mA or so. Zener diodes come in a variety of sizes, 500mW being the common small size. You can get 1W and 3W Zeners
as well. I would recommend 1W or 3W if you can find one locally. The resistor should be 1/2W or thereabouts.

You can use an adjustable regulator, the LM317 is very common, its like an asshole....everyones got one!
It would require a 317 reg, a 100mA TO92 size would be plenty big enough. Two resistors, or better one
resistor and an adjustable resistor would allow you to adjust it perfectly. The only draw back is the dropout voltage.
A linear regulator like this lets say has an output voltage of 10V. The device requires, according to the LM317 spec,
an input voltage of at least 2.5V MORE than the output voltage. So our reg will require 12.5V minimum. If the input
voltage drops below 12.5V then the output voltage may no longer get to the required 10V output, in fact it might stop
altogether. That is called the 'dropout voltage'. With 13.2V from the VFD you are awfully close to the minimum required
input voltage.

There are regulators which have lower than normal dropout voltages, called LDO regulators. They tend to be a little more
specialized and you are less likely to fin one in your local electronics shop.

I would try the Zener reg to start with, I'm 99% confident it will work for you. If not Then we start looking at slightly more
sophisticated designs.

Quote
Lastly why does the VFD have a 12V (13V) output when its analog inputs only work with 0-10v :S

I suspect that the VFD manufacturer sees the 12V nominal output as a purely auxillary supply and did not waste any resources
on its design, a standard off the shelf IC and that is that. The manufacturer might reasonably assume that the PWM
can handle the extra.

Geckos have an excellent reputation for robustness and it surprises me that they have specified such a close tolerance between
the expected max output (10V) and an input supply (12V). Without being privy to the circuit diagram I can't say for sure
why that is or if indeed 13.2V would cause damage. For the sake of a Zener and a resistor why risk it?

Craig
« Last Edit: February 08, 2019, 07:22:22 PM by joeaverage »
My wife left with my best friend...
     and I miss him!
Re: Setting up Spindle/VFD control Issues
« Reply #11 on: February 08, 2019, 07:21:33 PM »
Hi,

Quote
also has a Analog output which you can configure to output between 0-10v!

that output is NOT A SUPPLY for the PWM circuit!

Its meant to be a signal output, probably less than 10mA. Depending on how you program the drive the output
might be an analogue representation of the VFD ouptut power, or output current, or output frequency, or temperature of
the IGBT's, or whatever.....It meant so you can monitor the VFD or motor it drives.
My wife left with my best friend...
     and I miss him!
Re: Setting up Spindle/VFD control Issues
« Reply #12 on: February 08, 2019, 07:59:34 PM »
Oh oops ok, lucky... I had configured it and wired it up and it was working  but yes the voltage output was changing depending on what frequency i was commanding.

Ill grab a zener and resister as you specified tho.

p.s. connecting the Gecko's -ve to the VFD comm fixed the X1 issue. it now turns on the spindle as expected :) I guess this was due to the VFD not being connected to the same power source (its connected directly to AC mains and the Gecko off a 48V DC supply) they are both earthed to the same earth star but i guess the Comm and Earth terminal on the VFD are isolated
Re: Setting up Spindle/VFD control Issues
« Reply #13 on: February 08, 2019, 09:02:51 PM »
Ok I can get these locally:

220 Ohm 5 Watt Wire Wound Resistor or 220 Ohm 0.5 Watt Metal Film Resistor Either is cheap so I guess 5watt is overkill but better?

Also have the choice between a 9.1V zener or 10.0V zener both 1watt. Would the 10v Zener be better?
Re: Setting up Spindle/VFD control Issues
« Reply #14 on: February 08, 2019, 09:12:20 PM »
Hi,

Quote
Would the 10v Zener be better?

Yes, I don't ever recall seeing a 10V zener.

Craig
My wife left with my best friend...
     and I miss him!
Re: Setting up Spindle/VFD control Issues
« Reply #15 on: February 08, 2019, 09:17:15 PM »
Re: Setting up Spindle/VFD control Issues
« Reply #16 on: February 08, 2019, 09:25:33 PM »
Hi,
yes we do but 10V is not an E12 value.

Craig
My wife left with my best friend...
     and I miss him!
Re: Setting up Spindle/VFD control Issues
« Reply #17 on: February 08, 2019, 09:39:20 PM »
Whats a E12 Value? does that mean it wont work?
Re: Setting up Spindle/VFD control Issues
« Reply #18 on: February 08, 2019, 10:17:44 PM »
Hi,
no, everything will be fine.

Often component values are broken into standard steps. In the case of E12 it means '12 values per decade', the E signals
exponential increments. 

Thus E12 resistors are in values:
1       eg 1k        10k      100k     1M
1.2         1k2      12k      120k
1.5         1k5      15k
1.8         1k8
2.2
2.7
3.3
3.9
4.7
5.6
6.8
8.2
9.1

So you can routinely buy 4.7kOhm resistors but not 5kOhm. There are other 'series' like E24 and E96 but E12 is the
common one.

Craig
« Last Edit: February 08, 2019, 10:20:06 PM by joeaverage »
My wife left with my best friend...
     and I miss him!
Re: Setting up Spindle/VFD control Issues
« Reply #19 on: February 15, 2019, 06:42:19 PM »
So picked up the parts during the week and wired as per your diagram and is working perfectly Thanks! https://www.machsupport.com/forum/Smileys/default/grin.gif

Just for my understanding and curiosity is it working by the zener diode "bleeding" off any voltage it "see's" above its set value to ground (in this case 10v)

What I don't understand is how this does not create a short circuit and overload the amp capacity of the VFD 12v output?

Also can you explain what the resistor does for this setup please.

I did have a small issue where the commanded hz was not matching the output. say I commanded M3 S12000 the Gecko output (reading with a multimeter) is spot on 5.00V but the VFD is outputting 210-220hz  (should be 200hz) similar at M3 S24000 Gecko output = 9.98v VFD 385hz (should be 400hz)

Im guessing this is just due to the cheap chinese VFD, I adjusted the settings in the VFD to Max expected voltage to be 9.8V and now it puts out 400hz at 24000rpm commanded but 12000rpm is still the same or slightly higher from memory... which is fine for what Im doing, no need to be exactly spot on