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Author Topic: PoKeys57CNC 10 PIN IDC connector to CWD250 ground wires/pins?  (Read 825 times)

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Hello, I have a "Industrial Brand" CNC router that I am converting to use the Poykeys57CNC board because it actually has documentation and many more inputs/outputs available. I have the Pokeys wiring ribbon cable kit to run my ribbon wire from the PoKeys BOB 10 Pin connectors to CWD250 stepper motor controllers that came with the router. I saw one helpful video where the person just cut the ribbon cable ground wires off the cable but I am thinking they should be there for a reason? But where does one wire them to on the CWD250 stepper controller? I have what little info that CW-Motor provides but it does not answer this question. Any helpful suggestions will be appreciated. Thanks, BSA-LLC

Offline MN300

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Re: PoKeys57CNC 10 PIN IDC connector to CWD250 ground wires/pins?
« Reply #1 on: March 09, 2020, 10:52:59 AM »
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.
https://www.poscope.com/wp-content/uploads/downloads/Pokeys/Manuals/PoKeys57CNC%20user%20manual.pdf
http://www.cw-motor.com/uploadfile/file/20150603/201506030428050.rar

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.
Re: PoKeys57CNC 10 PIN IDC connector to CWD250 ground wires/pins?
« Reply #2 on: March 09, 2020, 11:18:06 AM »
Hello MN300,

Thank you for your answer. I had looked at the 2 manuals before posting but was not sure whether it was advisable to connect the grounds from the ribbon cable of the motor control from the bob to the Enable Signal ground of the CWD250?  I guess I will wait and see whether there is any other suggestions and I have submitted a request with the folks at PoLab. Thanks, BSA-LLC

Offline MN300

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Re: PoKeys57CNC 10 PIN IDC connector to CWD250 ground wires/pins?
« Reply #3 on: March 09, 2020, 11:52:35 AM »
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.
Re: PoKeys57CNC 10 PIN IDC connector to CWD250 ground wires/pins?
« Reply #4 on: March 09, 2020, 06:24:26 PM »
Here is the reply I received from the folks at PoLabs regarding the motor control ribbon cable ground pins and ribbon wires going to the Stepper Controller Drive that I have.

Dear BSA-LLC,


All ground wires are connected together on the device - any of them can be used, others can be left unconnected.