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Messages - MN300

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111
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: December 03, 2020, 11:25:33 AM »
It's kind of people not to point out the mistakes in the last drawing. Errors are bound to creep in. All the more reason for you Sherwood to go over it and ask about anything that seems wrong or you don't understand. Also it's amazing how much you forget after a year or two. The more detail we put in the easier it will be to repair or upgrade the system later.

I was going to use a solid state relay for the spindle but decided not to. It would have meant using P17 which is shared with the onboard relay, that's why the relay jumper was OFF. However I'm using the small onboard relay to control the spindle relay so it needs to be ON.
A copy and paste error affects the text for the limit switches. i forgot to go back and change "X AXIS LS" to Y and Z on their lines.

Some items will require more input to finish the drawing.
Details of the power supplies. I have drawn components in as semi-pictorial manner to make them clearer to beginners.
There should be a mains switch. Is there something now?
Verify the BOB relay common is connected to the 12-24V common.
Notes about where to use shielded cable.
Notes about shield grounding points. Generally they go to the ground of the equipment sourcing the signal.
Final selections for motor current and micro-stepping.

We'll catch up with these in later revisions.

112
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: December 03, 2020, 08:16:14 AM »
I used to design controls for industrial equipment, $50 for an E-STOP switch would not have been out of line because a switch intended to last for decades of hard use costs money. However we are in the hobby world where things are much more relaxed. If something has crashed or is smoking having the second E-STOP contact to interrupt the power to the motors is not a bad idea. The E-STOP switches found so far have 1 NO and 1 NC contact but we need 2 NC's. Major vendors sell the contacts and the operators ala carte so you can make what you need. At this point the cheapest option might be to buy two and move a contact.

ZASto is quite right about no need for capacitors on NC switches that only open in emergencies. Additionally The 10 volt levels into a relatively high current input (the optos) will be fairly immune to noise. Your machine is small and you should be able to keep power wiring away from the signal wiring. These all reasons you should not need caps.

Here are some cables from Maker Store. Could you contact the store to find out if they are all copper? I imagine they are but aluminium wires that break under vibration would be no fun.
Limit switches - https://www.makerstore.com.au/product/2-core-cable-70-2/
Motors and maybe stepper driver inputs - https://www.makerstore.com.au/product/shielded-4-core-cable/

113
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: December 02, 2020, 08:32:16 PM »
Here is a second draft of the wiring diagram.

Stepper input signal wiring changed to use the 4 pin connectors. Do you have a place to buy the cables or the materials?
Second limit switches added.
Wires grouped to indicate cabling.
Second E-STOP contact used to break AC mains to the 24V supply and the spindle.
Optional Relay added to start and stop the spindle under MACH control. The selected relay has a test button so the operator can run the spindle manually.

I would prefer to use a major supplier for some parts like the relay and socket. Minimum order value or minimum for free shipping might make that impractical. Candidates are element14, Mouser and Digi-Key.

Maker Store may have the best price on cable but one item has aluminium conductors, others don't specify. That's something to check before ordering.

114
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: December 01, 2020, 09:35:53 PM »
Here is item I forget to mention. If your E-STOP switch has two contacts we should use one to interrupt the 24 DC to the steppers.

115
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: December 01, 2020, 09:24:47 PM »
The drawing was made with the classic version of ExpressPCB software. I've used it for well over 10 years to design PCBs.

Let me discuss the most rigorous method of wiring. To get some idea of cost I found an eBay site with cable that looks to be a reasonable prices. This is just to get a general idea and not a recommendation. I know someone who bought inexpensive cable only to find out it was copper plated aluminium and not suitable for his use.
https://www.ebay.com/itm/RVSP-2-4-6-8-10-12-14-16-20-Core-Double-Twisted-Shielded-Cable-485-Signal-Wire/254397336055?hash=item3b3b4349f7:g:JE8AAOSwgqZdrqCW

Motor wiring would be done with shielded 2 pair cable.
4 core 0.5 mm2  5 meters US $13.30

Stepper drivers would be connected with 3 pair shielded cable, one pair for each of the three optos.
6 core 0.2 mm2 5 meters  US $11.02

Limit switches would be connected with twisted pairs, individually shielded or grouped into one cable as the physical configuration requires.
More of the 6 core or 2 core 0.2 mm2 5 meters US $5.87

24 volt power would connected with loosely twisted hookup wire to each stepper drive from a distribution terminal block. This is because if they were daisy chained the first part from the supply would be carrying all the motor current and need large conductors. I should change the drawing to reflect this.

There would be many commons and shield grounds going to the same places. On a industrial machine we would use lots of terminals the cost of which adds up fast. For hobby use they could be spliced together. You may have to learn how to solder.

This is a a belt and braces approach to the job. You might get away with extending the existing wiring with whatever scraps of wire you can find but...
Short runs need less protection so you may not need the expense of all that shielding but I don't know the details of your mill. I'd like to hear about the mill and what materials you have on hand. Who are the reputable vendors in your part of the world? Can your friend make recommendations?

116
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: December 01, 2020, 07:06:00 PM »
Here is a start on a wiring diagram. We can improve it when we learn more about the power supplies and any features you want to add. If you decide to use the 4 pin connectors instead of the terminals for the stepper drivers I could revise it for that.

I couldn't see the legends for the BOB relay terminals in the available information. Also it would be useful to verify the relay common is connected to the 24V common.

If the stepper motor windings are run in twisted pair and kept well away from the other wiring it will greatly reduce the change of problems with noise. Of course the spindle motor wiring need to be separated too. 
https://audiouniversityonline.com/twisted-pairs/

The 10 volt powered opto-isolated inputs give you better noise rejection than the usual 5 volt BOB wiring.
If the four wires to the stepper driver inputs are twisted together that will reduce noise pickup too.

When you decide where to mount the new equipment you will be able to determine if longer wires will be need.

117
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: December 01, 2020, 10:38:05 AM »
Pin 14 is one of the buffered outputs, no different from the others except that it is used to control more than one device. Here is a description of the BOB that might be informative.

Pins 10, 11, 12, 13 and 15 are the inputs for the limits switches or whatever you chose to connect to them.  The switches are powered by a 10 volt supply regulated down from the 24 volt supply. Their connection to the parallel port inputs is isolated through 5 of the opto couplers.

The 6th opto coupler connects pin 1, an output from the parallel port, to the circuit that changes the PWM spindle signal to analog. In the BOB diagram just to the left of the 6th opto-isolator there are two triangle symbols. These the sections of the SN74HD245s that buffer pin 1. Those sections and the 10K resistor are also shown on the left side of the diagram as IC2 and the resistor attached to pin 1.

Other outputs from the parallel port are not opto-isolated by the BOB. They are buffered by the SN47HC245 ICs and connect to the terminal strip. Stepper signals also connect to the 4 pin connectors. The opto couplers in the drivers isolate them from the parallel port and the 5V supply.

Pin 17 can be jumpered to operate the relay. That circuit is on the middle right of the diagram. The resistor and SN74HC245 section are also shown on the left like the analog circuit. The relay common is shown connected to the 24 volt common. That seems a bit strange as relays are often used to isolate circuits.

The relay, the input switches and the analog output share the same common which is isolated from the parallel port, the buffered outputs and 5 volt common. The parallel port receives ground from the PC. The 24 volt common should be separately grounded for safety, especially if the connections to the limits switches are not protected.


118
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 30, 2020, 11:23:07 PM »
Better information may come with the items but I wouldn't count on it.

If damage were to occur it would be to the SN74HC245. Another possible problem would be if the opto-coupler is just barely being turned on. Then it would be more susceptible to noise and could be the cause of missing steps. Since there is an unused buffer why not use it?

ZASto has provided the information for the BOB in a previous post.
https://www.machsupport.com/forum/index.php?topic=43939.msg282588#msg282588

Here is what I found for the TB6600.
https://www.mcielectronics.cl/website_MCI/static/documents/TB6600_data_sheet.pdf

Have you planned a clean place with good ventilation to mount the new equipment?

119
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 30, 2020, 06:05:49 PM »
I can't argue with your successful use of the BOB board. As I said, the IC specs define use in a logic system and the IC will put out more current if overloaded. It would be interesting to know the actual voltage being delivered to the opto input or better yet the current.
Hopefully the designer of the stepper driver left a safety margin between the minimum current that will just trigger the input and the minimum operating level in the spec. I don't have the information to decide if you are operating in the area between or are over the 8 mA minimum.

120
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 30, 2020, 04:45:23 PM »
I have been looking at how the BOB board connects to the rest of the system and see a problem with the stepper drivers. The TB6600 stepper drivers have opto-isolator inputs. The input signal current is a minimum of 8 mA. This is far more current than a normal logic input would require. The signals from the parallel port are buffered by SN74HC245 Octal Bus Transceivers. The datasheet says the output current of that device is 7 mA. That’s not to say it can’t provide more, but the voltage out may be lower than the level that is guaranteed to work with the input of other logic ICs. While this may be marginal design my main concern is with the enable signals.

Unlike the other signals, the enable signal, Pin 14, connects to 3 buffers. There are five  4 pin connectors provided for connecting to the stepper drivers. X and Y are connected to one output, Y, A and B are connected to the second. The third output goes to the P14 terminal. If the 4 pin connectors are used as intended the output shared by X and Y will have to supply 16 mA. As there is no A or B, the Z axis doesn’t have to share.
A solution would be to connect the enable of either X or Y to the Pin 14 terminal.

Another alternative way to wire would be to use the P terminals. The step and direction signals, P2 to P9 plus P16 and P17, also appear on the terminal strip. The 3 stepper drivers could be wired to the terminal strip instead of the 4 pin connectors. The driver enables would connect to P14 and the enable pins of the X (or Y) 4 pin connector and the Z connector. I think the connectors advertised as DuPont connectors would fit onto single pins of the 4 pin connectors. Many hobby sources carry these. Here is an example.
https://www.ebay.com/itm/40pcs-Dupont-Male-to-Female-10cm-Jumper-Wire-Connectors-Lead/254793576268?hash=item3b52e16f4c:g:bPAAAOSwASBdJbQJ
This method also gives you a way to connect if the mating 4 pin plugs do not come with the BOB.

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