BrianV

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  • in reply to: low stepper motor current ?? #21273
    BrianV
    Keymaster

    Well, the board is able to deliver 3 amps into that stepper motor (and it gets those motors damn hot too!).

    Tip 1: Setting the motor current: Stepper Motor Current Calculator
    Tip 2: Checking voltages FAQ
    Tip 3: Is it a Rev 1 or Rev 2 board. It is possible the motor low current enable is somehow turned on. The mechanism is different between Rev 1 and Rev 2.
    PRO 1: Idle Current Reduction must be disabled PRO board only – install J4 on all the 8-pin headers when setting the voltage.
    PRO 2: Take a look at the Pin 1 enable signal. Did you jumper it? Is your system sending a ‘disable’ signal?

    Let me know some more detail.
    BrianV

    BrianV

    in reply to: Before you post . . . #20733
    BrianV
    Keymaster

    The word “Opposing” has me confused.
    Do you mean one spinning CW and the other CCW, or (more commonly) do you want to “mirror” two steppers for a single axis (both spin the same direction and number of steps in sync).
    this is a great question that I do get asked from time-to-time, I’ll need to add it to the FAQs.
    Here’s the deal, you CAN NOT put two stepper motors onto one driver chip.
    Here’s how it’s done – for the sake of this discussion, let’s say you have two motors driving your Y-axis gantry:

    • Connect one stepper motor to the “Y” axis output
    • Connect the second motor to the “A” axis output (one motor, one driver chip)
    • Your CAM software should allow you to define what pins are the step-and-direction for each axis. Configure the Y axis step and direction to BOTH the Y and A inputs.
    • If you want that second motor to spin the opposite direction, then, in your CAM software where you just assigned the Y outputs to the Y and A axis, select the option to invert one of the direction signals.

    And that’s that!

    [Edit: change to “Y-axis ganty”]

    BrianV

    in reply to: Two Stepper Motors on one axis #20055
    BrianV
    Keymaster

    Great question. The reason you find very little info, is that you can’t just wire two motors to the same driver. Not a wise idea.
    Instead, you “Mirror” the second axis. You can do this two ways:

    1. The Bodge. You can physically cut some traces on the PC board to disconnect the A-axis ‘Step and Direction’ signals from the input connector, then run the Step and Direction signals from, say, the X-axis signals into the D connector, and route them over to the A-Axis also. Then you have one chip driving one motor, but both chips receiving the same input signals.
    2. The right way. In the LinuxCNC STEPCONFIG utility, you can specify what signals are output to what pins. Just make the A-Axis into another X-Axis highlighted in the image below. You can mirror any axis in this manner.
      LinuxCNC STEPCONF utility to mirror an axis

    I would imagine there would be similar configuration settings for all CNC software.

    Let me know how it works out!

    BrianV

    in reply to: What is pin 1 on the DB25 connector used for? #19451
    BrianV
    Keymaster

    Sorry for the super-late response. Not sure how I missed your post!!!

    1. I appear to have a Rev 1 board. Is there any way that I can run a jumper to some part of the HobbyCNC Pro 4 circuit from this pin so as to gain the Enable-pin function?

    A: Yes, but some parts need to be removed and some jumpers added and some traces cut.
    I just documented the process here: http://hobbycnc.com/pro-rev1-enable-signal/

    2. Is the Enable pin on the Rev 2 board an input or an output?

    A: Input

    3. I like to provide isolation between different power domains whenever possible. My concern here is that I would like to limit the damage if, for some reason, one of the SLA7078MR chips were to fail. By using optoisolators, I limit the damage to the HobbyCNC Pro 4 in that eventuality and protect the controller board from damage. Since my controller board requires me to make an adapter card, this would be an opportunity to put optoisolators on all signals to/from the HobbyCNC Pro 4 as well as on all limit-switch, home switch and tool touch-off points.

    A: There’s a lot to unpack here.

    PC to HobbyCNC board. Although possible, I’ve never run across a reason why to do this. Unlike the Inputs (TB 5), these signals are all contained in a single bundle from PC to board. Very little (none?) potential to add goofy voltages here.

    Inputs (TB 5). I’m a fan of this since the “inputs” (e.g. limit switches, probe, e-stop, home switches) are “outside” the safety of the electronics enclosure, and anything can come in contact with these wires. I think opto isolation here is a good idea. Remember, a completely separate, isolated power supply is required. I especially recommend opto isolation here if there are ‘false triggers’ of limit switches, etc.

    Outputs to Stepper Motor. This is not something that can be done.

    4. How much power, if any, can I draw from the +5VDC pad? I could mount a heatsink on the LM317. Would it be preferable to use a separate regulator for my adapter card?

    A: I prefer you don’t tap into the +5V line. Since that regulator needs to drop from 24 to 5 V, it can need to dissipate a LOT of power. It’s designed to just power the circuitry on the board.
    Details here: http://hobbycnc.com/sp_faq/checking-voltages/

    Regards, BrianV

    BrianV

    in reply to: What is pin 1 on the DB25 connector used for? #19001
    BrianV
    Keymaster

    Peter,

    Let’s start with Pin 1 on the D connector.

    • PRO Rev 1 boards, Pin 1 (and pins 14, 16 & 17) are NOT used, however these pins are available via solder pads, near the 25-Pin D connector. Most often these are used as ‘output’ to drive spindle control relays, mist/lubricant pumps, etc.
    • PRO Rev 2 boards, similar with ONE exception: pins 14, 16 & 17 are NOT used, and these pins are available via solder pads (these pads are on 0.100″ spacing, so a standard pin-header can be used), near the 25-Pin D connector. Difference – Pin 1 can be either a generic output OR you can add a small ‘solder-blob-jumper’ to turn this into an enable signal.

    The optoisolation:
    I’d never considered using them for step and direction. Since these signals are “inside” the control box, between a computer and the PRO board, I’ve never even suggested putting opto’s there.

    Where I do recommend opto isolation, is anytime a wire leaves the safety of the control box (particularly limit and home switches), where there is a possibility of induced noise or (worse) a high voltage being applied on accident.

    See my post: To Shield or Not To Shield (your wiring)

    BrianV

    BrianV

    in reply to: Timing requirements for driving HobbyCNC Pro 4 #18993
    BrianV
    Keymaster

    Thanks Richard, yes, this is the right answer. Step and direction signals route directly to the chip from the 25pin D connector.

    https://www.semicon.sanken-ele.co.jp/sk_content/sla7077mprt_ds_en.pdf

    As long as you keep the voltage to those pins at 5V (I’m pretty sure they work with 3.3V too).

    Although it’s for Arduino, you can probably get some info from here: http://hobbycnc.com/hobbycnc-and-arduino/

    BrianV

    BrianV

    in reply to: Mach3 Software Configuration #18982
    BrianV
    Keymaster

    Here’s everything I know:

    http://hobbycnc.com/hobbycnc-and-mach3/

    Regards, BrianV

    p.s. if you learn anything else, please do let me know and I’ll update the page!

    BrianV

    in reply to: Z Probe pin 15 #18929
    BrianV
    Keymaster

    Dear Jacques,
    Microprocessor I/O pins are quite delicate. They are not designed to string long wires from them into the ‘real world’, especially if there is ANY chance of ANY voltage getting applied to that wire. I always use opto-isolation on any/all inputs and driver chips (like a ULN-200X) on all output pins.

    “The Arduino input impedance of an ADC (analog-to-digital converter) pin is specified as 100 megohms.” (source). This is ripe for any noise on that line to damage the input, quickly and easily.

    Not sure why you’re using ADC for a probe. Typically this is just a switch input, like any limit switch.

    I would not exceed a few inches on any wire connected directly to a microprocessor input, and if I went longer, I’d be double-damn sure they’re not running near anything that could pump electromagnetic noise into the wire (like, say, the wiring that carries the current to the stepper motors.

    You need to put some isolation/buffer/driver between all I/O pins and the real world.

    From: https://http://www.rugged-circuits.com/10-ways-to-destroy-an-arduino
    —————————————————
    Method #3: Apply Overvoltage to I/O Pins
    HOW

    Apply a voltage exceeding 5.5V to any I/O pin. The I/O pin is destroyed.

    WHY
    This method of destruction forward-biases the ESD protection diode built-in to the microcontroller. Here is a model of each microcontroller I/O pin from the Atmel ATmega328P datasheet:

    Once the voltage at the I/O pin is greater than the supply voltage (5V) by about 0.5V, the top diode starts to conduct current. This is OK for diverting a short-duration overvoltage event, like ESD (electro-static discharge), but that diode is not meant to be on all the time. It will simply burn out and stop protecting the pin.
    —————————————————

    BrianV

    BrianV

    Attachments:
    in reply to: Dave’s original plans for foam cutter. #17417
    BrianV
    Keymaster

    Keith,
    I contacted Dave, and he never had plans for a foam cutter. He did at one time sell plans for a hobby router, but he’s since sold the rights to that.
    So, I’ve got nothing for you regarding plans for a mill or foam cutter.
    If you do need manuals for old HobbyCNC boards, check out the FAQs (under “support”) and scroll to the bottom.
    BrianV

    BrianV

    in reply to: assembled pro boaed #17054
    BrianV
    Keymaster

    Don, I don’t see any photos.

    Under normal operation, the heatsink will get too hot to touch for more than a few seconds. This is why a fan is recommended for 2A or more (I’d put a fan on it regardless, but that’s just me).

    Here’s where I point everyone when there is a problem:

    FAQ: No Motor Movement
    FAQ: Missing steps – motor not behaving properly

    FAQ: Microstepping Configuration
    FAQ: Product Manuals / Assembly Instructions
    FAQ: Is a special cable required to connect to my PC?
    FAQ: What Power Supply do I need?

    BrianV

    in reply to: New pro board with GMFC #16335
    BrianV
    Keymaster

    Don,
    The HobbyCNC boards haven’t had the timer feature for quite some time.
    Unfortunately, I can’t help you with answers regarding the GMFC software – you’ll need to ask them what work-arounds they suggest. The USB/Ethernet to parallel port devices I’ve see are all software-dependent, so what works with one CAM system likely won’t work with another.
    Sorry, but I’m sure the GMFC folks (or perhaps the website) can give you an answer.
    Regards, BrianV

    BrianV

    in reply to: Troubleshooting a 4 axis Pro assembly #16226
    BrianV
    Keymaster

    Well, there’s not really a lot of things that can go bad, and there’s not really a lot of diagnosis that can be done either.

    I’d have you start at the FAQs

    http://hobbycnc.com/sp_faq/no-motor-movement/

    and

    http://hobbycnc.com/sp_faq/missing-steps/

    If it’s a bad chip, email me brian at hobbycnc dot com and we’ll work it out.

    BrianV

    in reply to: Current Revision #16193
    BrianV
    Keymaster
    in reply to: E-Stop awareness #7684
    BrianV
    Keymaster

    Well, that isn’t the proper way to wire the switch. It is behaving exactly as I’d expect it to (e.g. it will do nothing).

    The e-stop switch needs to be connected at one side to the GND of TB5 and to one of the remaining open pins on that same connector (Pin 11, in your case). The pin needs to be pulled to ground, not V+ (it’s already at +5V).

    Another option is to put the e-stop switch in the same chain as the limit switches. See FAQ Home & Limit Switches. Regardless if it is a limit-reached or an e-stop, you want everything to stop moving.

    You could go the relay route, but I think it’s overkill.

    BrianV

    in reply to: E-Stop awareness #7683
    BrianV
    Keymaster

    The old forum is still available for reading: https://groups.yahoo.com/neo/groups/HobbyCNC/info.

    I’m not familiar with the 4AUPC boards, but I’ll give the drawing a look-over.

    BrianV

Viewing 15 posts - 1 through 15 (of 55 total)