David A's New 2x3 Bench Top CNC

[Ntl]

Can you also post a picture of the resistor they are talking about? I'm having a hard time trying to visualize how it's getting wired up. I'm sure down the road when you get it figured out it will be helpful for others since it seems like a common problem with the clearpaths. This whole topic could have a thread of it's own honestly.

[davida1234]

Can you also post a picture of the resistor they are talking about?

I don't know what kind of resistor and what kind of value it will be. They will suggest one after this email, I think.

[Ntl]

I don't know what kind of resistor and what kind of value it will be. They will suggest one after this email, I think.

Where does it go? That's what I'm trying to picture. I'm like you as far as wiring goes, my previous experience was limited to industrial network wiring and automotive type wiring. CNC equipment is very new to me still and I have a lot to learn.

[davida1234]

I don’t know yet how it will be wired as they haven’t responded yet.

[davida1234]

Email from Teknic:

Hi David,

Thank you for running these tests, it's been very helpful.

Based of the schematics for the C11G breakout board, there is a 4.7 kOhm resistor configured to pull-down, or pull-up based on jumper positions on the board. Based on how you described wiring the motors, you likely have this configured as a pull-down resistor.

This resistor will limit the amount of current flowing through the motor's HLFB. Given the small voltage drop with one motor, the current would be (4.96 V - 0.197 V)/4700 Ohm = 1.013 mA which is barely enough current to drive the output. As you increase the number of motors the voltage drop increases since there is a drop on each motor which reduces the current. By the time 4 motors are connected, there is no longer enough current for the HLFB to function.

An easy way to address this would be to "reduce" the pull down resistance to allow more current to flow. You can do this by putting a new resistor in parallel to the built in resistor on the board. Something between 1-5kohm should be adequate to allow enough current to run all four motors. This should give you an approximate voltage drop between 4.96 V (disabled), and ~0.8 V (enabled) depending on which exact resistor you use.

To wire the resistor simply connect one end to Input 10, and the other to GND.

Best Regards,

[Ntl]

Nice sounds like a easy fix I'm surprised no one else thought of using additional resistor's. Post a picture when I you have it up and running.

[davida1234]

Nice sounds like a easy fix

Well, in this case, I think it's too good to be true.

My email back to Teknic:

Hi,

Did as you instructed.

Both with a 2 kohm and a 4.7 kohm between Input 10 and GND, there is no change.

The readings are the same as with a 4 motor setup:

4 Motors:
Enabled voltage: 4.92 Volts
Input 10 (active low): black

Disabled voltage: 4.95 Volts
Input 10 (active low): black

[Ntl]

Well that answers the question I didn't ask. How adding a resistor would change the internal board resistor? I didn't ask because I don't know alot about circuit boards. Maybe they thought you could swap out the board's 4.7k resistor for a different one? Question, you didn't add a 4.7k+2k right? The way I understand the manual for your board the 4.7k the guy was referring to is built-in to your breakout board and he wanted you to just add the 1-5k not a additional 4.7k +2k.

[davida1234]

Well that answers the question I didn't ask. How adding a resistor would change the internal board resistor? I didn't ask because I don't know alot about circuit boards. Maybe they thought you could swap out the board's 4.7k resistor for a different one? Question, you didn't add a 4.7k+2k right? The way I understand the manual for your board the 4.7k the guy was referring to is built-in to your breakout board and he wanted you to just add the 1-5k not a additional 4.7k +2k.

Maybe my wording was a bit confusing.

I first tried a 4.7 kohm resistor (in addition to whatever the board has built-in as a pull-down resistor) and then I tried a 2 kohm resistor.
Both with the same results.

[Ntl]

Here's a calculator that may be helpful. It sure looks like what I thought that if you add a resistor, you will lower the current. I really think that they are thinking the 4.7k is removable or somehow adding one it bypasses the internal resistor. But that makes no sense to me personally.

https://www.rapidtables.com/calc/ele...alculator.html

[davida1234]

"An easy way to address this would be to "reduce" the pull down resistance to allow more current
to flow. You can do this by putting a new resistor in parallel to the built in resistor on the board."

I think his statement is pretty clear.

Besides, he is talking about a parallel resistor.
That reduces the resistance = higher current.

https://www.allaboutcircuits.com/too...ce-calculator/

[Ntl]

So what I'm trying to understand is if the HLFB can accept a maximum of 30mA and the board puts out 24mA if I read it right. Then each motor has internal current limiters and the max output current is 9ma per apendex d of the clearpath manual.

Hopefully your following me so far.

So let's say you get the maximum current going in to the drives, the drives reduce the current to 9mA max output regardless of what the current coming in is. So how will increasing the current going to the first motor do anything for the current coming out of the last motor going to the bob?

Wouldn't the current after the first motor now be reduced to 9ma and start dropping lower and lower as it travels through the additional motors?

That's where I get lost, also what is the current drop? The current is what matters especially considering you can run up to 30v for the HLFB.

I'm tapping out and will just wait and see what they come back with. I obviously don't understand how it works or how it's supposed to work or I'm not understanding their manual or all of the above. It just doesn't make sense and makes my little brain hurt lol

[davida1234]

It just doesn't make sense and makes my little brain hurt lol

That's why I let them figure it out.

They are corresponding even today with me, on a Saturday.

Like you suggested, I tested the last servo by itself. Had
different readings than the other three.

They asked me to send a "Configuration" and a "Support Package"
file of that servo which I did.

[davida1234]

A nicely surfaced spoil board:


The pop-outs of the spoil board are for boundary pins.
Set them at any of the 24 positions.
SS or nylon setscrews:


Boundary pins installed:

[davida1234]

A 18mm BB ply piece on the spoil board, up against the pins:


I could use the standard T-channel clamps but too
high and too much effort to dodge them for me.

These are the clamps I use. Truss head bolts and
T-nuts. All stainless steel:


Tongue of the T-nut goes in first, towards the material:

[GME]

A nicely surfaced spoil board:


The pop-outs of the spoil board are for boundary pins.
Set them at any of the 24 positions.
SS or nylon setscrews:


Boundary pins installed:

Very nice, David. Boundary pins . . . (visualize stroking my beard). Unless there is another purpose I'm missing, I assume they are used to align stock along X-axis, Y-axis, or both axes. I haven't seen this particular solution before. I like it for it's compactness and overall elegance. I also like it for the ability to use it on either the plywood or HDPE levels. Unfortunately, not necessarily reliable for use with an MDF level (poor treading/screw holding, and doubtful reliability when it comes to holding a set screw vertically over time). Definitely has promise. Got the wheels turning to figure an adaptation for MDF.

Gary

[davida1234]

Push the clamp up against the material and tighten down:


The T-nut tongue keeps the clamp bolts tight and upright against the material.
The head height of the bolt is below the safe-Z. You can jog right over it:


Scrap piece clamped down:

[mactec54]

Very nice, David. Boundary pins . . . (visualize stroking my beard). Unless there is another purpose I'm missing, I assume they are used to align stock along X-axis, Y-axis, or both axes. I haven't seen this particular solution before. I like it for it's compactness and overall elegance. I also like it for the ability to use it on either the plywood or HDPE levels. Unfortunately, not necessarily reliable for use with an MDF level (poor treading/screw holding, and doubtful reliability when it comes to holding a set screw vertically over time). Definitely has promise. Got the wheels turning to figure an adaptation for MDF.

Gary

Don't have to be screwed in Dowels work just as well, I use dowels the same way all the time, even on machining centers and if you want to be creative you can use pneumatic air cylinders that pop up for location and down once the part is clamped down

[davida1234]

Don't have to be screwed in Dowels work just as well

Yes, dowels or nylon set screws work just as well.

[davida1234]

I also like it for the ability to use it on either the plywood or HDPE levels.

You can also use some or all of those positions
as a clamp. Like this one in the middle: