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24V Signals
« on: November 08, 2014, 10:11:21 PM »
Hello,
I am trying to use some servo drives that require 24V instead of the LPT 5V stuff. Is there a simple way to convert the step/dir to 24V signals?
Thanks
Re: 24V Signals
« Reply #1 on: November 09, 2014, 06:10:42 PM »
It should surprise me if someone doesn't already make an interface board that will do this.

A SN7407N IC (Hex Buffer/driver with open collector) might serve as a basis although I am sure there are newer, faster chips that might be better. Changing the signal levels should be fairly easy but you would have to be cognizant of the implications on timing. The 7407 is a very old chip and has average propagation delays of 14 nanoseconds.

Unfortunately, unless you can find someone already producing an interface board, you would have to design the complete circuit around your selected chip, although that should not be too complicated.

Graham
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Graham
Re: 24V Signals
« Reply #2 on: November 09, 2014, 06:27:16 PM »
Yes, there are a couple of similar chips that act like that, however I couldn't find any exact implementation. I assume just putting the chip between the 5V from the LPT breakout board and the servo drive that expects 24V instead of 5V, would not be the most reliable way to do it.

According to the servo drive datasheet, the pulse width should be >= 2.5us and pulse pause >= 2.5us.
Re: 24V Signals
« Reply #3 on: November 09, 2014, 07:00:35 PM »
I did a quick Google and came up with this. I only took a superficial look but it might do what you need.
http://www.talent-hk.com/data/TEK6%20DatasheetR2.0.pdf

I assume just putting the chip between the 5V from the LPT breakout board and the servo drive that expects 24V instead of 5V, would not be the most reliable way to do it.

According to the servo drive datasheet, the pulse width should be >= 2.5us and pulse pause >= 2.5us.

This is essentially how to do it. you would need a 24VDC supply, some pullup resistors and probably a capacitor or two on the power supply circuits to help avoid noise. It might also be a good idea to opto isolate the inputs from the parallel port. In theory it would not be complicated. In practice it will be all about timing errors and pulse shape. If it were my machine, I would probably rough something up and see how it works but tweaking it to work reliably (if possible) would require hands on analysis with at least a DSO to study the timing.

The 2.5uS pulses would be no problem. You can set them in Mach3 and the IC would reproduce them within its timing constraints.

Graham
« Last Edit: November 09, 2014, 07:02:45 PM by GBowes »
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Graham
Re: 24V Signals
« Reply #4 on: November 09, 2014, 07:17:37 PM »
Well :)
The motors I am trying to use are Berger Lahr VRDM 3910/50 LWB (VRDM 3910 LW 4 Nm 230 V 2,00 A). They are driven by Berger Lahr WD3-007.0501 (WD3-007.0501 230VAC 24V-signal-input). The drivers were signaled by a Siemens PLC.
The driver in the link will not work.

There is a 5V signal version of the Berger Lahr (WD3-007.1501 230VAC 5V-signal-input) but the costs for the buying 3 units for 3 motors is ridiculous. I would rather buy modern servos at that price, the WD3 was released somewhere around 2003. The only chance would be to bump the LPT 5V signals to 24V, in theory even optocouplers would work. I was hoping somebody already went through this (being a common problem if you wish to use 24V industrial stuff via Mach3 and LPT).

Also, the specs of the driver:
Uhigh, min 20 V
Uhigh, max V 30 V
Ulow, max 3 V
Ulow, min -30V
Imax = 30 mA
Current Control
Ihigh, min 7 mA
Ihigh, max 15 mA
Ilow, max 0.2 mA
Ilow, min -25 mA
Umax = 5.25 V
« Last Edit: November 09, 2014, 07:20:39 PM by MPower »

Offline TPS

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Re: 24V Signals
« Reply #5 on: November 10, 2014, 03:01:35 AM »
Hi,

have a look for CS-Lab controllers, they are on 24v industrial standard.

Thomas
anything is possible, just try to do it.
if you find some mistakes, in my bad bavarian english,they are yours.
Re: 24V Signals
« Reply #6 on: November 10, 2014, 06:10:15 AM »
Re: 24V Signals
« Reply #8 on: November 10, 2014, 07:46:32 AM »
Looks like it could handle the task. Did you use this or similar SSR for converting the signal voltage? I am not sure if I just plug the LPT on one side and the Berger driver on the other side and that's it, or I have to add some extra filters for the signal quality improvement.

Offline TPS

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Re: 24V Signals
« Reply #9 on: November 10, 2014, 08:00:16 AM »
hi,
i think on the 5v side its only to connect to lpt port,
but on the 24v side you need to add a power supply,
because the berger lahr is only a input.

Thomas
anything is possible, just try to do it.
if you find some mistakes, in my bad bavarian english,they are yours.