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Messages - MN300

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This file refers to the MD430
It says the EN (enable) input can be left vacant if not used. Your USB board doesn't seem to have enable outputs. More information would be need to find its manual.

5V          +5V
XP          STEP
XD          DIR
--            EN - NO CONNECTION

The same pattern applies for the remaining axes.

The inputs are opto isolated so there is no problem in connecting the ground of the PoKeys to the minus side of the opto couplers. They are not connected to the ground of the CWD250.
My only doubt is if the current supplied by PoKeys  is higher than the minimum required by the opto coupler input. Perhaps the folks at cw-motor could answer that question.

I downloaded the manuals for the PoKeys57CNC and the CWD250 thinking it would just be a matter of finding the right pins to connect. However it turns out not to be that simple.

Page 4 of the CWD250 manual shows two options for using the opto isolated inputs.
Figure 1, common cathode, uses the controller outputs and ground for positive logic.
Figure 2, common anode, uses the controller outputs and +5V for inverted logic.
The table on page 5 shows the external resistor is not needed for 5V operation.
Either method will work as long as the settings in MACH program match.

The problem is the limited current output of the PoKeys57CNC.
Page 16 lists the enable, step and direction outputs as type DO5. Page 18 shows type DO5 outputs have a 100 ohm resistor in series and the maximum current is 8 mA.

The CWD250 inputs consist of a opto coupler input diode and a 270 ohm resistor is series. This would draw about 12 mA if connected to 5V.
When the 100 ohm resistor of the PoKeys output is taken into account the current would be about 9 mA, if the output actually can do a bit more than the 8 mA.

So, the question is, would connecting as per the CWD250 figures work reliably? My guess is yes but there is no guarantee.
Detailed information needed to verify that operation is not available.

A buffer could be added between the outputs and input to supply the full current. Two ways that come to mind would use hex inverter ICs or CMOS transistors.
I suspect building such a circuit would take you out of your comfort zone.

General Mach Discussion / Re: Index
« on: March 01, 2020, 11:06:55 AM »
My first idea for an alternative was a system we used in the 1990s as an inexpensive and rugged encoder. Sold by Xolox, it consisted of a magnetic wheel with an alternating pattern of north and south poles around the circumference and a hall effect sensor. Unfortunately that company is no longer around.

Today I found equivalent wheels at Digi-Key. I believe the small hole for the shaft can be bored a bit larger if necessary.

4 pole Wheel, equivalent to two vanes

Hall sensor example,  You can probably find less expensive sensors at a hobby electronics site. There are also sensors in a transistor-like package but those will be harder to mount.

General Mach Discussion / Re: Index
« on: March 01, 2020, 09:00:57 AM »
Yes, 5V should be fine.
By the way, I made a mistake in converting the maximum switching frequency of 200 KHz to motor speed. It should have been 100,000 revs per second.

General Mach Discussion / Re: Index
« on: March 01, 2020, 07:37:27 AM »
There is a diagram in the datasheet.

Pin 1 is VCC (12V)
Pin2 is Ground
Pin 3 is the output.
You can attach the 10K resistor there. It may not actually be needed if your BOB provides pull up, but it won't hurt.
There is a figure in the datasheet that shows a 820 ohm resistor. This value would be needed to operate at the device's maximum speed. That would be 100,000 rpm with two vanes. I assume you aren't going that fast.

The vane is interrupting a magnet field so it needs to be a ferrous material.

General Mach Discussion / Re: Index
« on: February 29, 2020, 09:08:48 AM »
A magnetic solution such as a hall effect sensor wouldn't suffer from contamination but the part you attach to the shaft is more difficult to make.
Here is a example of a vane sensor  https://www.digikey.com/product-detail/en/tt-electronics-optek-technology/OHB900/365-1002-ND/374780
You would have to make a disk with slots. One vane would not be balanced so there would need to be two. I image someone could make a one vane design with a counterweight but that's way above my pay grade.
You have started on the optical route, it will be informative to hear how successful that is for your application.

General Mach Discussion / Re: Index
« on: February 29, 2020, 08:06:00 AM »
The OPB606A is specified as having an output of 500 uA under the test conditions. This is barely enough to drive the 10K resistor shown in the diagram found in the link TPS provided. Your conditions will be less than ideal as dirt and film build up on the sensor and the shaft. Also your reflector is curved, reducing the effective area.

The OPB607A uses a Darlington photo transistor and has a much higher output - up to 25 mA (50 times more).

The diagram's R1 which sets the diode current is a bit low. Nominal current is 20 mA, 100 ohms would result in 33 mA. 150 ohms would be a safer choice. You could overdrive the diode but run the risk of overheating and failure.

Your reflective surface should be 50% white and 50% matte black, a bare shaft may reflect light.

An open photo sensor is a high maintenance item. It will take frequent cleaning to keep it running.

General Mach Discussion / Re: pwm spindle control help needed
« on: February 28, 2020, 08:47:23 AM »
It's unlikely something on the VFD has changed to increase the loading of the signal. However before you spend £50 for a new BOB it would be good to know for sure it's faulty.
You could substitute resistors for the VFD. I would guess the VFD input is equivalent to about a 10K resistor and would expect the BOB to handle a lower value of 5K .
Also you could use your meter to measure the current draw. Improper connection of a meter set to measure current can damage the meter so I don't recommend it unless you have enough experience and understanding to do it safely or know someone who does.

Troubleshooting the board without a detailed schematic is difficult. It maybe a faulty voltage regulator, a poor solder joint, a bad electrolytic capacitor or many other things. Again it would take someone with experience to do this. You could beg cnc4you for the schematic but I doubt they would be willing to share it.

If you do buy a new board the old one could be used to add IO for more limit switches and outputs should you want them.

General Mach Discussion / Re: pwm spindle control help needed
« on: February 26, 2020, 11:26:59 AM »
Your initial post reads as if you have only changed the motor, is that the case?

Another item on the list of possible faulty components is the external voltage supply ( 12V?) used by the 0-to-10V circuit. That would be easy to check when the VFD is connected.

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