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Messages - MN300

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251
The zener plus 470 ohms is a practical solution for this application.
The 470 ohm resistor will see about 1/8 watt so use 1/4 watt resistors.
Like a blocking diode, it's in series with the 10k pull-up resistor. The voltage drop will be about 0.23 volts. On a system with a lower value pull-up that voltage would be higher so others should check before copying this method.
This combination will also work with systems that can be configured for a pull-down resistor.

252
When a transistor is used as a switch the VCE(sat), the collector saturation voltage, is typically around 0.05-0.2 Volts. This is what the input would see as a low level.
A blocking diode in series with the input raises the low level about 0.6 volts, lowering the noise margin a bit.

If the pull-up of the sensor is just the 4700 ohm resistor, adding another 470 ohms in series makes little difference. Just the zener across the input will protect it.

If the sensor had an active pull up to 12 volts that would be a different case, the 470 ohm resistor would limit the current into the zener.

253
General Mach Discussion / Re: Limit switches and PWM for laser
« on: March 25, 2019, 11:13:01 AM »
It occurred to me that your system has only a software E-Stop. On an industrial machine the E-Stop hardware stops motion independent of the main control. Better BOB boards have a dedicated E-Stop input that will stop the steppers and the spindle immediately. You have to decide how much risk there is of damage to the machine and of personal injury.

The inverter wiring can be tied to the E-Stop, this probably will involve adding a relay.

Info on your stepper driver boards will show if they have an enable input that can be shutdown by an E-Stop.


254
General Mach Discussion / Re: Limit switches and PWM for laser
« on: March 25, 2019, 10:41:34 AM »
Yes, the equipment you have is limited but usable.

Could you get away without using shielded cable? - Maybe, but you don't want to find out the hard way. Run a separate shielded pair to each switch, someday you will probably invest in a better BOB board with more inputs.
I suggest that you start up the system is stages, First get the axes moving, then the spindle.

I can't find a manual for the hardware side of your PRT-e1500w inverter. Did you get a paper copy? A picture of its terminal strip(s) would be a help if nothing else is available.

255
General Mach Discussion / Re: Limit switches and PWM for laser
« on: March 24, 2019, 06:25:02 PM »
xlr8sion,

Your laser board appears to be a SW-LD73 V1.1 which uses PWM to control the output.

reuelt asked earlier if you are using all 4 axes. If one axis is free it can be used to provide PWM for the laser. If none are free and the laser is a must then you will need a different BOB board.

The documentation for the BSMCE04V USB board is questionable. The diagram seems to be from an Aliexpress site selling a controller and drive package. The PDF file says it's the Mach3 USB Motion Card STB4100 V2.1 Installation manual.

There is no explanation of the uses of AVI+ and AVI- terminals. In the diagram AVI- connects to the Inverter GND terminal, this would say it's the same as COM. If so, why isn't it just labeled COM? Although it's normally a high end feature maybe the analog output is opto-isolated. Use your ohmmeter to measure from the COM terminal to AVI+ and to AVI-. If the readings are infinite then the output is isolated.

Since this board is what you have let's make our best attempt to make it work.

First you can follow instructions and do the setup to get the axes moving. Leave the spindle and laser wiring for later. The switches in the diagram are all normally open. The home switches are connected in parallel. You will have to make sure none are on at the start of the homing sequence. If one is actuated at the start the controller would have no way to determine which it is and which axis to move to clear it. Actually I suppose if just the Z switch is on and the Z axis is first the homing will work.

Once you have things moving you can go on to the spindle and the laser.

MN300

256
General Mach Discussion / Re: Limit switches and PWM for laser
« on: March 23, 2019, 01:56:50 PM »
It would help to know if your laser is looking for an analog signal or PWM signal (digital). As an example, Opt Laser’s PLH3D will work with either.

257
You have said the error is small. You could do a high speed move to a location near home before the G28.1 command to speed things up.

258
Video P*r*o*b*i*n*g / Re: 3d Probing on Granite slabs
« on: March 22, 2019, 08:52:33 AM »
The sliding ring may not work for all applications. Sometimes the background may be cut away leaving the lettering. Then there may not be enough supporting material for the ring.

259
Video P*r*o*b*i*n*g / Re: 3d Probing on Granite slabs
« on: March 22, 2019, 08:15:09 AM »
Cutting granite makes stone dust. Will sliding a ring across the dirty surface make scratches in the polished surface?

260
Connecting the ground of the computer to the ground of the machinery can provide a path for noise to enter and affect the computer, regardless of the limit switch filtering. If none of the previous suggestions solve the problem an opto-isolator type BOB may be needed.

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