[takeda]

Hello.

Is it possible to get the PWM out of parport, convert it to DC (with RC filter) and them amplify that to 0-10V with an opamp, and then control spindle speed by using the VI and ACM inputs of the DZB200?

I can't figure why not, please some help!

Thanks

[neilw20]

You are right. Just an RC filter will do it, but you only will get 2-3v DC usable so can amplify it if needed.
I have found with the VFD I used, that you need to detect if there are any PWM pulses, so you can release the stop button line on the VFD to make it safe.
The VFD I used had the option to set a scaling factor, so I did not need an amplifier. I just made it about 1.4v for full speed.

[takeda]

Thanks a lot.

I am already looking at the manual for a scaling factor in fuction and configuration but it's a messy manual. .

rgrds,
Petros

PS I cant understand the following though:

[quote]I have found with the VFD I used, that you need to detect if there are any PWM pulses, so you can release the stop button line on the VFD to make it safe.[\quote]

[neilw20]

PS I cant understand the following though:

I have found with the VFD I used, that you need to detect if there are any PWM pulses, so you can release the stop button line on the VFD to make it safe.[\quote]

Petros.

You can bring the command voltage to zero and the spindle will stop.
Consider if the parallel cable gets unplugged, and the control line floats in a positive direction. The spindle will start.
If spindle start requires the presence of the PWM pulses, then it works sort of like a watchdog, and ensure that the spindle cannot start unexpectedly.
SAFETY FIRST! Schematic quality a bit rough, but you get the idea?

The input to this circuit should be AC coupled, so that it will only work if pulses are present. AC coupling not shown.
/Safety switch at bottom right was to a door switch for tool change access.

[takeda]

PS I cant understand the following though:

Petros.

You can bring the command voltage to zero and the spindle will stop.
Consider if the parallel cable gets unplugged, and the control line floats in a positive direction. The spindle will start.
If spindle start requires the presence of the PWM pulses, then it works sort of like a watchdog, and ensure that the spindle cannot start unexpectedly.
SAFETY FIRST! Schematic quality a bit rough, but you get the idea?

The input to this circuit should be AC coupled, so that it will only work if pulses are present. AC coupling not shown.
/Safety switch at bottom right was to a door switch for tool change access.

Yes I understand (I think). I have to find an input in the VFD to connect the "/stop line" in order to ensure that spindle will start only if PWM pulses are present from the parport.

I will double check the manual and I will try to find a connection (I think that this could be configured through M0, M1, etc inputs). Although, since it's the first time I get involved with VFD and stuff for mechanics, It's easier for me to design a circuit that gives a 0V output if the parport get's disconnected (using a buffer or something with pull down input).

I already found the threshold configuration for VI (minimum and maximum limits)

Thanks for the tips
Petros

[takeda]

I finally used an RC filter to smooth the pwm into DC, just for a check.

After using a voltmeter I measured the output voltage rated 0V to 3V.

The DBZ200 I found in the cnc installation has on input pin for both VI and CI and its called AI (Analog input probably), plus a mechanical switch to select VI or CI.

The problem is that when I configured the VFD to be controlled from Terminal (and not from keyboard) I had no success with AI configured as VI. When I changed the input to VI+CI from within the VFD the spindle worked.

I guess I need a voltage buffer or something in order to work as Voltage controlled.

Then I had to configure the CI min and CI max value from 0.05 to 1.6 almost to fully control the spindle speed.


The strange thing is that when i set the mechanical switch VI,CI to CI it was not working.

[neilw20]

Do you have the VFD manual in electronic form? A pdf maybe.
I am sure there is a way. Just have to study it in more detail.
Trial usually leads to error. Analyze the problem, and solve it.
Then wire it up and it will work. There are so many combinations that may not work, so trial and error will probably frustrate you eventually.