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.
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