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Author Topic: Looking for good DIY controller kit supplier  (Read 4046 times)

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Offline MN300

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Re: Looking for good DIY controller kit supplier
« Reply #80 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?
Re: Looking for good DIY controller kit supplier
« Reply #81 on: November 28, 2020, 11:12:13 PM »
Good to know.
No, I have not yet bought the power supplies. I have a shed full of those little AC/DC adaptor transformers that power TVs, amplifiers, laptops and a variety of other electrical devices that I thought might be suitable - could be mistaken. I have here for instance a Toshiba N17908, AC 100V, 50-60Hz, 1.5A to DC 19V, 4.74A, or a Simsukian with an output of 9V DC and 1.5A .... would that be a suitable approach, and what Voltage and Amperage parameters should I look for?
By the way, could the Bosch router speed potentiometer be replaced by another devise that can be activated by Mach 3?
So I will be running the steppers in an open loop config, without encoders; should I expect missing step and stalling difficulties and what should I do to minimise or eradicate the chances of these happening?

Offline MN300

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Re: Looking for good DIY controller kit supplier
« Reply #82 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.
Re: Looking for good DIY controller kit supplier
« Reply #83 on: November 29, 2020, 12:42:21 AM »
The BOB purchased is the ST V2 and the Drives purchased are the TB6600 and I've purchased a digital Digitech multimeter to play with.
ZASto, would you please tell me what power supplies you use to power these devices?

Offline ZASto

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Re: Looking for good DIY controller kit supplier
« Reply #84 on: November 29, 2020, 05:23:55 AM »
@MN300: Actually my TimeZone is GMT+1 :)
To be on topic, PC side supply can be a simple USB cable from computer connected to USB connector on BOB.
The other power supply depends on your motors. I use 24V / 240W MeanWell switching power supply and on PC side 5V 15W also MeanWell power supply. I prefer a separate power supply for 5V side.
Power rating on 24V side is determined by your motors and oversized supply will be happier when it is not loaded 100%
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Offline MN300

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Re: Looking for good DIY controller kit supplier
« Reply #85 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.
Re: Looking for good DIY controller kit supplier
« Reply #86 on: November 29, 2020, 09:33:08 PM »
Yep, I follow the formulas mathematically; conceptually somewhat hazy but that will settle.

What do you think of some of the cheaper ebay transformers from China at about AU$20 to $25. I bought a 240 - 110V step down transformer from China quite some time ago and it's still working.

Also, the 5V power supply, any particular wattage to consider?

Offline MN300

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Re: Looking for good DIY controller kit supplier
« Reply #87 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.
Re: Looking for good DIY controller kit supplier
« Reply #88 on: November 30, 2020, 07:25:43 AM »
Yes MN300, challenging

As far as the stepper electronic magic is concerned, I'm reading and comprehending more.
I see how you arrive at all the values. I see how the 24 V power source sets up the stepper winding's potential energy (PE) and how the stepper drive is basically a switch that raises the PE levels (Voltage) required to start the Flow of electrons (Amperage) to generate the Power (Wattage) required to rotate the stepper motor 1 step at the time.

Question: Was the 2.5 Amps per winding or per motor (2 windings)?

Question re: "When the inductance of the winding sees a change in current it creates a back voltage which resists that change" How does that occur, is that an opposing electromagnetic force?

I'll have a good view of the entire process depending on the answers to those questions.

I'll provide the 5 V and 24 V of the BOB with a reliable separate power supplies.

Offline MN300

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Re: Looking for good DIY controller kit supplier
« Reply #89 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)