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satchid
07-30-2009, 01:07 PM
Dear all,
This is my first post for a long time, but now I run into problems.

I have purchased an Elte TMPE2 0.75Kw with integrated inverter 400Hz. This inverter has terminals for a 1Kohm potentiometer for the speed control.

In the (bad) manual it is said that remote speed control is to be with a potentiometer, nothing is said to control it with a 0 to 5V or 10V DC.

Here are some measurements on the potentiometer:

one fixed terminal of the pot is 0V
the other fixed terminal of the pot is 5V
when the wiper-terminal of the pot is at 5V the speed of the spindle is 3,000RPM , and when the wiper terminal is at 0V the speed of the spindle is maximum 24000 RPM.
So, speed gos up when the voltage gos down.

Now, I want to controle this spindle with Mach3, so I have some Questions:

1, can I control this spindle-inverter with a DC voltage from 5V to 0V?
2, could it be that if I input say 7 volts to the wiper for an even lower speed. (I have to cool extra of cause)?
3, Is there a way to convert the output (in PWM or puls) from a program like mach3 to this 5V to 0V knowing that a lower voltage is making the spindle go faster?

help is always very appreciated
Thank you,

Willy

PS, there are more terminals on the pcb, but the technician of Elte sais that they are not functional jet.

ger21
07-30-2009, 01:37 PM
Will this work for you?

http://www.cnc4pc.com/Store/osc/product_info.php?cPath=25&products_id=179

eSilviu
07-30-2009, 01:52 PM
1, can I control this spindle-inverter with a DC voltage from 5V to 0V?

put a capacitor (220nF or so) between cursor of the pot and "0V". If it's keep working, you can control the spindle with a DC voltage.

2, could it be that if I input say 7 volts to the wiper for an even lower speed. (I have to cool extra of cause)?

I doubt. I recommend NOT TRYING. It's possible (99.9% chances) that the inverter to have the internal IC powered on 5V. Putting a voltage bigger than that on any input pin, will destroy your controller.
so.. DO NOT TRY!

3, Is there a way to convert the output (in PWM or puls) from a program like mach3 to this 5V to 0V knowing that a lower voltage is making the spindle go faster?

I've attached a schematic that will work, assuming point 1. can be applied.
It has galvanic isolation between input and output, so it saves you of troubles.
How it's working:
- you apply PWM from parallel port to the optocoupler, that will drive the NPN transistor (any NPN will do the job)
-in collector of the transistor you get inverted PWM signal.
-you filter the !PWM with RC filter, to obtain a DC voltage, proportional to the inverse of the duty-cycle of the original signal.

satchid
07-31-2009, 03:53 PM
Thank you very much both of you for a complete and fast solution, I am investigating these solutions.

Willy

satchid
07-31-2009, 04:12 PM
I somehow like the "C6 - Variable Speed Control Board" from CNC4PC becouse it is ready made but it is straight in straight out.
The schematic attached to message #3 has the transistor to invert the PWM signal behind the optocoupler. This is not possible with the above board without drastically changing it.
Therefore, could the transistor arrangement be placed before the optocoupler to invert the PWM signal? If this is possible, then it is much less work to arrive at the finished solution, and is less expensive as the "C18 - Pot Driven Speed Control Board"

Thanks, Willy

eSilviu
07-31-2009, 06:55 PM
I somehow like the "C6 - Variable Speed Control Board" from CNC4PC becouse it is ready made but it is straight in straight out.
The schematic attached to message #3 has the transistor to invert the PWM signal behind the optocoupler. This is not possible with the above board without drastically changing it.

Thanks, Willy

What’s the problem with transistor behind the optocoupler?!
As I've draw the schematics, it will function very well, exactly for what you've asked.

Are you scared to power a transistor from your speed controller?

satchid
08-01-2009, 02:21 AM
I am very grateful for your solution, there is noting wrong with the schematic as you made it. The only thing is that I am in a hurry at this moment and need a controller quick. Therefore I wanted to purchase an already build piece that is working as a standard "0v low speed and 10V high speed" and then putting the transistor-inverter part of your schematic in front of this ready-made board might solve the problem and is much quicker in service, but I am not sure of this.
In the mean time I ordered the following:
http://www.cnc4pc.com/Store/osc/prod...roducts_id=179
I will use the above on the CNC machine for now until I build your schematic later and will use the above solution on an other machine.
But I still would like to know, can I put the inverter in front of a ready made board?

Thanks,
Willy