PWM to Voltage Converter Issues - Again!

Nightowl

@gloomyandy said in PWM to Voltage Converter Issues - Again!:

Since you have decided to start a new thread on this topic, you should post details of the converter you are using and your config.g file. Otherwise folks need to go looking for your previous thread...

Ok, sorry.

This is a link to the converter I'm using, which appears to be similar to the one you linked to.

The spindle section of the config.g file is shown below:

; Milling motor and relay configuration
M950 R0 C"vfd+out7" L4000:25000 Q1000	; enable router relay on out7
M563 P0 S"George" R0 			; assign spindle 0 to tool 0 and name it George
T0					; select tool 0
M5					; ensure motor is turned off

Note: out7 enables/disables the relay providing mains power to the spindle. This is because the minimum speed, when connected to a digital interface is 4,000rpm (not 0rpm).

I've attached the config.g as a .txt file, in case you want to check it out.

What I needed to be sure of was that "...feeding a 100% signal..." to the converter is exactly the same as "...applying 3.3V..." to it, although it seems this one requires 5V (according to the product page), but I understand that now.

I'll test it tomorrow and report back here.

Thank you

config.txt

Nightowl

@gloomyandy

Tested the converter and it is defective. I cannot get more than 8.4V out from the spindle control pins when I actually need 10V, so a new one is on order!

Thanks for pointing me in the right direction in getting this sorted.

Nightowl

@gloomyandy

I've ordered two of these, from different manufacturers (at least as far as the trading name goes) but both of the new ones have an output of between 0 and 8.6VDC, and turning the small screw has absolutely no effect at all.

The input voltage is 12VDC (measured) and the PWM voltage is 5VDC (measured) to get an output of 8.4VDC, or a PWM voltage of 0VDC to get an output of 0.0VDC

So now I'm clean out of ideas.

dc42

@Nightowl can you trace the schematic of them?

Nightowl

@dc42
Not very well, I'm afraid. What would I need to know?

I could provide a photo

dc42

@Nightowl I have one somewhere, but it may take me a while to find it.

Nightowl

@dc42 Isn't it in the cupboard, behind the clock?

That's where I keep finding 'lost' stuff

T3P3Tony

@Nightowl said in PWM to Voltage Converter Issues - Again!:

've ordered two of these, from different manufacturers (at least as far as the trading name goes) but both of the new ones have an output of between 0 and 8.6VDC, and turning the small screw has absolutely no effect at all.

I would return them as faulty as a start!

Nightowl

@T3P3Tony

Yup, they're gone!

Further to this, though... The one that does come close still only provides 9.6VDC, and that's with the brass screw all the way in, but I had to use 24V directly from the PSU, not 12V/GND supply adjacent to the VFD/Laser/Servo Driver header.

I really don't understand why the converter won't give the 10V the spindle needs.

Perhaps it's time to persuade Duet to design it into the control board

Nightowl

So, I've been out to the workshed (too small to be a workshop, too big to be a toolshed) and, with the (cheapest) PWM-Voltage converter managed to achieve the following:

Programmed - Actual Speeds
M10000 gives 10,150rpm
M14000 gives 14,010rpm
M18000 gives 18,000rpm

As this is the speed range within which I primarily use the spindle, I think that'll do!

Thanks to you all for your help!

alankilian

@Nightowl EXCELLENT!!!