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Question #: 14378

Question: My pokeysCNC board creates and analog signal of 0-10V for 0 to 24000 spindle rpm just like it should from Mach3. However, when the spindle is on, the voltage only gets to about 3.8V for 24000 rpm. It seems like the vfd is drawing more current than the pokeyscnc analog output can produce. It there an easy solution to this problem?

Current Solution

Do you have the Pokeys57CNC connected to a 24V external power supply?

Additional Information:
Yes, a 24V external power supply with the jumper positioned. I'm using the ethernet port so the 24v is the only source of power. I plan to measure the amp draw when I have a chance to see how much the vfd is drawing on the analog out.

Additional Information:
Further information. The resistance across the terminals on the vfd is 22k ohms. With an independent 0-10v current source I can run the spindle from 20 to 400 Hz. The PokeysCNC only gets to 3.8v with the vfd attached (and the vfd is at 150 Hz) compared to 10v when the vfd is not attached. The power to the PokeysCNC is steady at 24.18 V, so I'm not maxing out the power supply. Still looking for thoughts on what might be going on?

Additional Information:
And the other thing - The measured amperage is 0.17 mA for the 0-10 V signal (which makes perfect sense for 3.7 V and 22k Ohms).

Additional Information:
Just to bring finality to this issue - I added a 2.2 microfarad capacitor across the 0-10V input terminal (from signal to ground). This solved the issue. Evidently, it was an electrical noise issue.


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