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Messages - MN300

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121
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 30, 2020, 08:20:35 AM »
This tutorial covers back EMF and the relationship of current and voltage.
https://www.electronics-tutorials.ws/inductor/inductor.html

Stepper current is specified in amps per phase (winding)

122
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 29, 2020, 11:04:04 PM »
You seem eager to learn but was my mention of stepper magic too much, too soon?

I think the BOB will draw less than 250mA (0.250A) from the 5V supply. A USB 1.0 or 2.0 port can provide up to 500mA.
While checking the manual for info on this issue I noticed they show the 5V USB jack connecting to the computer. I don't see a reason that shouldn't work if there is a spare port.
Any small power supply intended to emulate a USB port's DC will do the job too.

The 24V power supply is not a place to cut corners. ZASto has suggested a supply known to work, best to stick with that.
Most power supplies these days will accept AC mains voltage from about 100V to 240V. There should be no need to involve a stepdown transformer.

123
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 29, 2020, 09:58:47 AM »
ZASto,  Sorry for misplacing you. Your profile lists your location as Vanuatu. Google maps puts that in the South Pacific near Australia.
Your power supply selection sounds good. Four motors (who knows the future) times 2 windings = 8 windings. 3 ohms times 2.5 amps squared times 8 = 150 watts. I would expect the actual motor current to be less.

Sherwood, Here is a bit of explanation about the magic the stepper drives do. If you add up the motor currents, 8 times 2.5 amps, you get 20 amps. A 24V/240 watt supply can only provide 10 amps.
The system works because the stepper drive contains a switching power supply that efficiently converts the incoming voltage and current to whatever is needed to establish the selected current.

At the maximum expected current setting, when the drive is stopped, the voltage on a winding will be 7.5 volts.
Voltage = 2.5 amps times the resistance 3 ohms. (both sides of the 1.4 ohm halves plus a bit for wiring loss).

In this example the output of 7.5V at 2.5A (18.75 watts) is converted from an input of 24V at .78A (18.75 watts).
Actually the conversion is probably 80% efficient so the input current is closer to 1A. Times 8 windings = 8 amps from the 24V supply.

When the drive is stepping the current changes with each step. When the inductance of the winding sees a change in current it creates a back voltage which resists that change. The drive momentarily raises the voltage applied to the motor to overcome this and speed up the rate of change. 24V is about 3 times 7.5V so the current rises 3 times faster. Motor torque is related to current so this allows a motor to have more torque a high speeds.

My max current estimate of 2.5 amps would produce a lot of heat in the motors. Your system should run well at 1.5 or 2 amps.

124
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 29, 2020, 12:21:42 AM »
As ZASto lives in your part of the world (Vanuatu) he can better recommend a local supplier for the stepper supply. I'm 17 time zones away from you, GMT-6.
The presence of a USB type connector on the BOB for the 5V power indicates it's expecting the type of small supply you mentioned. Just make sure it's 5V.
You may want to purchase a cheap digital multimeter. Once you learn a few basics it will be useful for setting up and trouble shooting.
I would have to see information about your drive to know if it's possible and is it's safe to connect it to the BOB. The relay and analog output share a common with the switch inputs. The drive could put a hazardous voltage on the switch wiring. There is equipment you could add to isolate the drive if that's a goal.

125
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 28, 2020, 10:33:59 PM »
A jumper is a short wire or clip connecting two point of a circuit. They typically enable or disable functions or set the configuration. The jumper in the BOB diagram enables the signal on the port pin 17 to operate the relay as opposed to providing a digital output.
PWM is pulse width modulation. The off and on time of a constant frequency signal is varied to encode an analog value. It's a way to transfer a numeric value using just one output. In the case of the spindle speed 10% on time is converted to 1 volt output, 50% = 5 volts etc.
Did you buy the power supplies?

126
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 28, 2020, 02:27:45 PM »
Thanks to ZASto for providing the missing documentation. I looked for links in the AliExpress item but could not find them or a model number with which to search the web.
It's good to see the 12 to 24 volt side of the circuit is isolated from the parallel port. This includes the 12V switch inputs, the relay common, and the 10V analog output. The TB6600 stepper drive is opto-isolated completing the isolation between the parallel port and the rest of the CNC controls.

127
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 28, 2020, 09:50:42 AM »
The CNC Router Source was a good find!
Yes, simple is good. It will get you running and give you the experience to decide what to do next.
The stepper drives in ZASto's earlier post look like good value for money but I would do further research before committing to the no name breakout board. The chinglish description in the AliExpress site is hard to interpret. Compare that information to the manual for a similar BOB.
https://www.cnc4pc.com/pub/media/productattachments/files/c11g-r9_user_manual_2.pdf
If ZASto has used it and can support you then it sounds like a suitable device. Does your computer meet the requirements for using that board?

The stepper drives are for bipolar motors. Ignore the center taps on your steppers and connect the ends of the windings to the drive.

We need more information to decide if/how the breakout board can control your spindle. The picture of the breakout board shows a relay but I would hesitate to run mains power through it. Does the spindle have a variable speed drive?

128
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 27, 2020, 01:23:47 PM »
I have looked at the specifications for motors with a the same frame size and similar holding torque and resistance. Their amps/phase is around 2 to 2.5 amps. If you apply too much current the motor will run hotter and the magnetic field will saturate give you no further improvement in performance. Too little current will reduce the torque but still be much better than the current system.

129
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 27, 2020, 09:48:42 AM »
To answer your configuration question about encoders, most hobbyist CNC machines are open loop. They don’t feed back the position to the controller with encoders.

The equipment ZASto suggested should be a bit better that what you have but has little extra for adding more features. Also you will need a power supply for the steppers. The stepper drive photos show they can use 9 to 42 volts. The higher the voltage, the more torque and speed you will get from the motors.

Here are a number of things to consider before you select your new equipment. I am including features you may want in the future. There are many posts discussing
 specific pieces of equipment.

Type of Interface to PC  BOB
Parallel - 1 port, limited number of Inputs and outputs.
USB, Ethernet - Multiple ports, some have an External motor controller
http://support.machsupport.com/en/kb/articles/what-is-an-external-motion-device

Electrical Isolation from the PC protects circuits from damage and interference. Isolation between the interface and the steppers and spindle is important too. The drives in ZASto’s link are optically isolated.
Many interfaces need a power supply, usually 5 volts.

Equipment to be interfaced
Limit and home switch inputs – more IO ports allows separate input of switches to help with troubleshooting.
E-Stop input
Stepper motor drives
Relays for Spindle On/Off - direction, Coolant, etc
Analog output for spindle speed

Stepper motor drives
Motor current, speed
Stepper motor power supply
Current setting for your steppers – we will need to determine that later

Optional equipment
Probe – set tool height
MPG – manual pulse generator to manually move the axes
LASER

130
General Mach Discussion / Re: Looking for good DIY controller kit supplier
« on: November 24, 2020, 09:25:12 PM »
You calculated Z and Y to be 39.37steps /mm and Z to be 31.25. That puts Z traveling about 25% faster -2500mm/min. I had to guess at several factors so my number could be well off, I chose the conservative answer.
When troubleshooting a problem a good method is to consider what has changed. In this case it's changing to MACH 3 software. Inadvertently selecting too high max speed seems to be a possibility.

Your photo just showed up. I notice the part number on the board is MAXNC CL 10108C. The circuit diagram is for 10108A. I don't see any obvious differences in the parts used, maybe the PIC program is the difference.

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