12v --> 10v Nowforever D100S2R2B inverter & MKS-V-V02 CDXHCTECH board

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Originally Posted by Doddy

I'm impressed with the inverter - the manual claims the electrolytic caps within are "wearing parts" and must be replaced after 5 years.

At least they're honest.

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That's interesting, I have a couple of 1hp Siemens VFDs which are well over 10 years old and get daily use, standards must be slipping ;-)

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Originally Posted by magicniner

That's interesting, I have a couple of 1hp Siemens VFDs which are well over 10 years old and get daily use, standards must be slipping ;-)

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...or Siemens don't push the limits quite as much as the Chinese? I seem to remember that the HY manual says that you need to re-form the electrolytics if the inverter isn't used for a year, and you should use a variable voltage supply and work up to full voltage slowly. My guess is that daily use is actually better for the caps than letting the thing stand unused for long periods. I try to use 105degC caps for high-power applications rather than the cheaper 70degC versions - maybe Siemens do as well!

The reason I suggested changing the parameters is this;

The manual for a Nowforever E100 shows that it uses 12v for the 0-10 input.
The graph shown in the first post of this thread shows that speed error gets worse as the frequency increases.
It suggests to me that the upper frequency setting should be adjusted so that at maximum input voltage to Analogue Input 1, the frequency was such that spindle speed was correct.

Regarding diodes, we used to use this method on reversing roller tables to give a central dead band for the operators, but on some of the newer drives this did not work as planned.

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Originally Posted by EddyCurrent

The reason I suggested changing the parameters is this;

The manual for a Nowforever E100 shows that it uses 12v for the 0-10 input.
The graph shown in the first post of this thread shows that speed error gets worse as the frequency increases.
It suggests to me that the upper frequency setting should be adjusted so that at maximum input voltage to Analogue Input 1, the frequency was such that spindle speed was correct.

Regarding diodes, we used to use this method on reversing roller tables to give a central dead band for the operators, but on some of the newer drives this did not work as planned.

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My interpretation of the E100 manual is that - yes - it provides a 12V supply to the speed controller but that the AI1 input still remains expecting a value from 0-10V from 0-100% RPM. That's pretty much backed off with the graph that the OP provided (full RPM at 20000dmd/24000full x 12V(ref) = 10V). Reading the manual the value for the AI1 input is programmable from 0..10V, but not beyond. There is a gain setting that can be applied also, but I'd expect, again, that requires that the AI1 input is limited to 10V. My concern is that the response to the AI1 input will be limited at 10V, and so no amount of scaling applied by the controller in the VFD would counter this.

Of course, remote interpretation of a Chinglish manual is never an exact science.

Ref the diodes / roller table - I guess you're using the forward bias of the diode to generate a dead-band around the pot's central position?, nice idea (strange that modern machines didn't work with that - be interesting to look at the input characteristics of the modern machines - maybe super hi-z could cause some unexpected results. In the OP's case though - driving the interface board down through 3 silicon diodes should generate a reasonably steady voltage drop somewhere around the 2V region.

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Originally Posted by Doddy

My interpretation of the E100 manual is that - yes - it provides a 12V supply to the speed controller but that the AI1 input still remains expecting a value from 0-10V from 0-100% RPM. That's pretty much backed off with the graph that the OP provided (full RPM at 20000dmd/24000full x 12V(ref) = 10V). Reading the manual the value for the AI1 input is programmable from 0..10V, but not beyond. There is a gain setting that can be applied also, but I'd expect, again, that requires that the AI1 input is limited to 10V. My concern is that the response to the AI1 input will be limited at 10V, and so no amount of scaling applied by the controller in the VFD would counter this.

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What you say is correct but;
1. Regardless, the vfd diagram does show the input connected to 12v
2. I never intended that the parameter should go beyond 10v because that is obvioulsy it's limit set in the firmware, my intention was to set it so that whatever was output from Mach3 e.g. S20000 actually produced 20k RPM at the spindle.

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Originally Posted by EddyCurrent

What you say is correct but;
1. Regardless, the vfd diagram does show the input connected to 12v

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Again, we are interpreting a Chinglish manual (or diagram, in this case) so there is a bit of guesswork here! The given diagram shows a pot supplied with 12V. If the idea is that the pot is uncalibrated and you use it in conjunction with the VFD display, then this is fine - in effect, it just reduces the rotation of the pot spindle to go from zero to full. Ditto, I guess, if the pot has a calibrated scale associated but again you won't use the full pot travel.

Slightly different situation where the analogue input is driven from an external source, although it's a pity that the BOB or whatever doesn't regulate the DC input to ensure that the output range is correct.

Guys,
With the right pot the source voltage is close to irrelevant so long as you can't blow the VFD input with the output.
Instead of arguing semantics why not posit a functional solution to the problem as it stands.
Offsetting voltage with diodes chops off the bottom of the range BTW ;-)

- Nick

No it doesn't. Read my post - it's reducing the Vref voltage from 12V to 10V. The controller's charge-pump will then generate a voltage proportional to the M-S ratio of the demand vs Vref - from 0v to 10v.

It is a functional solution.

I didn't think the OP had a "pot" - if he did, then the solution would be to introduce a positive-side static resistance, e.g. 2k on top of a 10k pot, which would give a sufficient offset from the 12V reference voltage. But that's not the design case here.

Re. the chop-off. Nope, what you have interpreted is the insertion of the diode chain into the Ain1 input, that's not what I posted.

So the BOB will function properly with 10V input rather than 12V?

Bonus, you've fixed it!

Nice one!

The BoB requires a 10V ref input. The implementation is flawed by driving that with a 12V reference.

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