Machsupport Forum
Third party software and hardware support forums. => PoKeys => Topic started by: flim63 on December 23, 2016, 10:04:00 PM
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Just finished building a Routakit and fit a Pokeys57cnc to it. Tonight I tried to connect the Huanyang VFD to the board. The relay turns it on and I finally got speed control but not full RPM and it is VERY non-linear. First, symptoms.
S24000 only gets me 20200 RPM, voltage reads 8.1v. S12000 produces 13200 with 4.0v. S6000 is 11000RPM and 2v. So far linear voltages but not VFD response (I'll look into the VFD after I solve the voltage). Then it gets screwy. S3000=9000RPM and 1.4v. S1000=13000RPM with voltage back UP to 4v. If I close Mach4 and use the Pokeys utility and move the PWM slider, same voltage profile is output 0% is 4v, 25% is 2v, 50% is 4v and 100% is 8.1v. In Mach4 diagnostics of the Pokeys plugin, the monitor box tracks correctly from 0% to 100%, but shows it on pin 18 for some reason. All spindle settings are set to pin 17 as spindle control. Board power is from a 24v 5A "laptop" type supply and the jumper is set to EXT for power. I have measured the voltage at both the VFD and Pokeys end and even disconnected the 10v wire and measured output. Ground wire is connected to GNDi and I tried both terminal 1 and 4 for GNDi. Mach spindle settings have been varied with no change in results (i.e. range 6000-24000, 0-24000, PWM frequency varied from 800 to 20000. HELP
Jason
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Did some experimenting and when I disconnect the VFD from the Pokeys, the voltage output behaves like it is supposed to. It is when the VFD is attached that the Pokeys output gets messed up. Is this ground loop? What would be a solution to try?
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The analog output is galvanically isolated and can handle limited amount of current (<50 mA). Check the input impedance of the VFD's analog input.
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With the VFD on and the jumper set to remote speed control, the impedance of the VI terminal and analog ground terminal is 19.9K ohms
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sorry I see you have played with pwm but have you actually used the voltage trim pot on the card?
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Yes, the output is 10v at 100% if I don't connect the VFD. When the VFD is connected it goes to 8.1 max. If I trim it up to 10v I can get full speed but the slowest it will go is 9000 rpm, and thats at 25%. Lower percentages than 25 start giving higher voltages and speed increases.
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Do you have any other loads connected to PoKeys device?
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I've the same problem. I could set the rpm in mach4 "spindle" "min and max rpm" to adjust the outputvoltagespektrum of the pokeys57cnc. The rpm area isn't as big as needed. I can start from 9000 to 22000. i've used the pot too. regards
www.cncprint.blogspot.com
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How do you power the PoKeys57CNC device?
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I power it directly with a 24V wall plug.
regards
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The adjustment pot is really small and relatively stiff. Are you sure that you indeed rotated it? Observe the flat region on one side of the pot head.
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I'am sure that i can turn the pot without any problems. I've bought a special small screwdriver for it. In Mach3 it works without any problems.
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Simple test. With the vfd disconnected put a 20K resistor across the pokeys output and vary the input across the range of speeds. If you see the voltage drop off same as for VFD then you will be sure the problem is a combination of low output current from pokeys combined with low input impedence of the VFD. Back before you youngins were playing with this kind of stuff we had to resort to vacuum tube voltmeters so the meter itself wouldn't pull the voltage down!
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Cncprint did you fix this in the end? I am having a similar problem. Works perfect when not connected to VFD (even with 15k ohm across it.) As soon as its connected to VFD voltage drops. The max voltage i can get is 2.8 even trimmed with POT. This is Pokeys57cnc
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The pokeys output current is too low to drive the input impedance of the VFD. So you will need an amplifier circuit that can provide more drive current than the Pokeys. I know the why, but I am not not an electronics guy to suggest a circuit.
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The measured impedance of the VFD input which is the same on most VFDs is 19.8kOhm. If you do the math the input pulls almost nothing. Also with the wires disconnected from the VFD and 1kohm load between the wires the voltage does not drop.
Im stumped on this one.
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THANK THE F@#KING LORD!!
I have figured it out!
I figured it must be high frequency noise coming out of the VFD but dont have an osiliscope so i wrapped both the 0v line and the 10v line around some ferrite chokes as many times as i could and boom off she went perfect speeds and perfect voltages.
Photo for others struggling with this. Only took me about a solid week to find it dam it!
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Nice work Peter.
Thanks for posting so that someone else can benefit from it.
Mike