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Messages - MN300

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1
When the transistor turns off the falling current in the relay coil creates a reverse voltage spike. This is typically several times your applied voltage and can damage the transistor. Normally a diode is placed across the coil, cathode to positive. When the voltage reverses the diode conducts and the resistance of the coil absorbs the energy that was stored in the coil's magnetic field.
As the breakdown voltage of the BC337 is 50 VDC you appear to be getting away without the diode, so far. If you were using a 12 volt relay you may not be so lucky. Small diodes are cheap and good insurance against that type of failure. A 1N4148 is a commonly available diode as is any one from the 1N4001 to 1N4007 series. The difference in the 1N4000 series numbers is the voltage rating but they are all high enough for this use.

2
A quick look gave no results from Omron, you'll have to widen the search. Probably you will have to make a new mount to fit what you find.
The correct sensor needs to run on 12V input power and have a PNP transistor output, Also the output needs to turn on when the light is blocked.
Post a part number if you find a likely candidate.

3
Sorry to disappoint you but 2.2.8 shows the inputs expect a connection to 12V, not to ground like many breakout boards.

The sensor you have chosen will not work with this type input. Perhaps Omron makes a version with the same physical dimensions that has the right electrical features. I take a look.

oh, and you're welcome

4
This is what I think you are asking for, two switches from the same axis connected to one input

5
Yes you can power all the sensors with one supply, its 3A output is enough for 100 30mA sensors.

Quote
then simply take vcc out
x axis x++ and x--
y axis y++ and y--
z axis z++ and y--

I'm not sure what you mean by vcc out, do you mean the output of the sensor? It's not Vcc, The output just makes a connection to ground when on.
You can connect two of these outputs to one input. The input needs to be the type that works with a switch contact to ground

6
Quote
pardon my ignorance, but i dont undestand 10v in and 28v out

The input voltage powers the photosensor. The maximum voltage is 10V. However 5V is all it requires.
The output uses an open collector transistor that acts like a normally open contact to ground, just like a mechanical switch. The maximum voltage it can withstand is 28V.

There are many low cost voltage regulators on eBay, Here is one example.
https://www.ebay.com/itm/403714437758?
You can use it to reduce your 12V to 5V for supplying the photo sensor.

This one's output is set by two areas marked A and B where you blob two pads together with solder.
There is a chart to show you how to set the voltage. For 5V there's no blob on A and a blob on B.


7
Mach4 General Discussion / Re: Lua script: Pause for operator to jog?
« on: November 10, 2022, 08:53:49 AM »
Could you reverse the order of the operations? If the tap of the fixed touch off plate can be done by the Lua script do the manual table touch first and then let the script take over and find the touch off point.

8
Mach4 Toolbox / Re: Automatic gearbox with 20 speeds
« on: October 15, 2022, 07:58:33 AM »
It may well be worth the effort to build a manual control panel with 6 pushbuttons for the motors and 6 LEDs for the hall sensors. A small bit of LUA code could display the desired speed and wait for an operator response to continue. This would allow you to learn learn how often the planned sequence fails, either due to gears not meshing or some other motor stall.
Information gathered by manual testing will help you design the automatic control. If there are failures an automatic sequence won't be able to handle you will have to plan for manual intervention.
If the motors can tolerate a stall that condition could be detected by timing the cycle.

I'm curious about how 20 speeds can be set by 3 motors going to 2 positions. That's only 8 combinations.

John

9
Mach4 General Discussion / Re: Servo Wiring
« on: May 20, 2022, 04:41:50 PM »
Hi Craig,
Yes, anti-parallel diodes will protect the opto-isolators. It's rare for manufacturers to publish a schematic with that much detail so I assume the worst.

Quote
Any one optoisolator is biased by one supply only.
Your drawing indicates multiple servos with individual power supplies sharing the reset and enable lines. This does create the situation where a dead supply will attempt to reverse bias the optos. The active supply will pull up the shared lines when the open collector output is off.

John

10
Mach4 General Discussion / Re: Servo Wiring
« on: May 20, 2022, 08:45:22 AM »
There is a risk to the opto-isolators created by paralleling inputs powered by different 24V supplies. If one supply is off its opto-isolators will receive a reverse bias from the other supply. Their cathodes will see about 22V or 23V from the shared signal line ( 24V minus the emitter drop of the other optos) while the anodes will be at zero volts ( the unpowered 24V rail).
The maximum reverse rating of the typical opto-isolator is about 5 volts. In the real world the maximum is usually far higher than the spec but applying 4 times the rating is a risk.

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