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Wiring Wild Horse Econo Probe
« on: November 30, 2014, 01:39:24 PM »
I am my wits end.  I am trying to wire the probe up to my BOB (DB-25) but I can’t get it to work.  I know little if anything about electrical stuff, so whether I need a pull up resistor, and pull down resistor, or an in between resistor has me stumped.  I do know that an LED requires a resistor but just don't know if board has one built in.  

I cut the wire about 6” from the probe body and soldered in a female 3.5 stereo plug so I would have a short wire from the probe in case I wanted to turn it manually for aligning or whatever.  The wiring inside the probe is as follows:
right side of circuit - blue wire
left side circuit -  green wire
the yellow wire goes underneath the circuit board, so I am assuming it to be grounded to the probe case

It appears to me that I attach the the green wire to ground, the blue wire to pin 10, but am not sure if I connect the yellow wire to anything.  Since it is normally a closed circuit, I am thinking that maybe the yellow is a common and has to go to the 5v terminal, but I would ask and see if anyone can give me some advice.  I don’t want to blow it up.
I realize I still have a lot to learn, but am too deep into this hobby to give it up, and too stubborn to admit defeat!
Re: Wiring Wild Horse Econo Probe
« Reply #1 on: November 30, 2014, 04:17:17 PM »
Hi fortdick:

If you log in to www.cnc4pc.com, and go the the section "Touchprobe(4)" Arturo has very clear schematics on wiring your probe.


Re: Wiring Wild Horse Econo Probe
« Reply #2 on: December 01, 2014, 03:42:35 PM »
Thanks for the response John,

I have tried those schematics, and that is my problem.  I don't quite understand.  It appears I hook the left channel of the stereo plug to ground and the right to the input terminal, in my case, number 10.  I have tested all the connections and have conductivity between the probe and the plugs and at the wire ends.  I wired it up the way the schematics showed and had power on the left channel (2.5v), which I had plugged into the ground.  That made no sense to me, so I switched the left and right channels and still no joy.  The LED doesn't work and I get no response from Mach3.

I have it connected in inputs to terminal 10, port 1, enabled, low.  It must be that I have to wire in a pull down resistor because that is the only thing I haven't done.  I am confused about why I have the ground wire coming from the plug/probe hanging out the doing nothing.

Did I say that electrical stuff confuses the hell out of me?  I will never understand how breaking a closed circuit will make the LED go on! 

Thanks for the tie to look and help if you can.

Re: Wiring Wild Horse Econo Probe
« Reply #3 on: December 01, 2014, 06:33:27 PM »
I will try to make some sense out of the probe logic.

The signal the probe circuit sees is either a Hi, or Low. It was designed to work with a touch plate
for tool setting. A "Tool Setting" touch plate is insulated from the machine table, and wired to the
probe input pin. Its overall thickness is measured, and entered into the probe program set-up box.

A special tool is used to set-up the Z0 position of a job. This tool is usually an edge finder, or some
other type tool that does not get changed, or used to cut metal. All tool offsets are relative to this
first tool.

1.  When the G31 signal is received by Mach3, the spindle starts moving down.
2.  The tool in the spindle touches the insulated metal touch plate;
3.  The probe circuit immediately changes from an active HI (+5 volts) to a Low (0 volts) because the
    tool bit is at "Ground";
4.  Mach3 immediately stops.
5.  The program reads the Z axis position, and enters it into a parameter;
6.  The touch plate thickness has previously been entered into the probe "set-up";
7.  The probe program adds the touch plate thickness to the Z position parameter;
8.  This new calculated number becomes the "Tool Height offset" for the tool in the spindle.
9.  This value is usually put into the tool offset table, by the program, which requires a tool# before
    each probing cycle.

Now, the probe is entirely different. Instead of a signal going from a Hi (+5v) to a Low (0v), by
grounding the tool bit,  it must go from a closed circuit, that conducts +5v, to an open circuit 0v.
This would work OK, except for the LED in the circuit. The LED is wired across the probe circuitry, with
a 1K resistor in series. The LED can only take a tiny amount of current to light up. A full 5v would
burn it out.

So the probe circuit is seeing a solid 5v, and the LED does nothing because the voltage goes past it,
because the probe contacts are closed. The LED does not turn on, because the +5v is going right around it.

Now, the probe makes contact, and the probe circuit opens; Instead of the probe circuit going to 0v,
a tiny bit of voltage is now going through the LED circuit, and the probe circuit. Because of this small
current, there is a tiny voltage, maybe 1 or 1.5v and about 20 milliamps flowing in the circuit.

As far as the probe program and Mach3 are concerned (Mach3 does think, you know), the probe has not yet
made contact!

Since the circuit is still not 0 volts, it requires pull-up, or pull-down resistors to trigger the probe

There are better explanations than this one, and a diagram helps a bunch.

Lots of people have wrecked their probe contact tips getting everything working OK. Certainly NOT a
"Plug and Play" operation.

While you are working out the bugs, get it working without driving the fragile probe tip up against
a solid object with the machine axis motors. Just move the probe by hand, and watch the probe activity light
on the Mach3 screen.

Re: Wiring Wild Horse Econo Probe
« Reply #4 on: December 01, 2014, 07:18:54 PM »
Thanks John,  that clears a lot up for me.  So the switch going from closed to open is telling the input pin that the probe has made contact and the pin knows this because there is no more current.  Is that correct?  Now the LED is connected to the one side of the circuit with a resistor to reduce the flow of power to the LED while the main circuit is broken.  This is because with the main circuit is closed the resistor send the power down the main circuit because there is less resistance?  The LED is then ground to the probe case, independent of the main circuit?

So if it is too much power going to the LED I need a pull down resistor and wire a jumper wire with a resistor in series between the input wire and a 5v terminal?  Using the same wire as the to the input pin, with the resistor wire running to power connected and then do I still run the ground wire like before?

How can I tell if there is too much power?

Geez I feel sleazy taking the knowledge that you spent time, money and sweat acquiring!

Re: Wiring Wild Horse Econo Probe
« Reply #5 on: December 01, 2014, 08:50:36 PM »
Hi fortdick:

The forum is for all of us. I am just a machine shop guy who uses Mach3, and far from an expert in such things.
It is not that the LED uses too much power; it is just a visual signal the probe circuit has opened. Study the schematics, and
make sure the wires you are playing with are the right ones.
All of the things on the CNC4PC schematics are correct, and the probe correct functioning is one of the big-time Mach3 problems
constantly befuddling members.

There is a good write-up on the web site for Mach Standard Mill, or the MSM Screen set; http://www.calypsoventures.com/forums/.
Dave Bagby is the author of the MSM screen, and is extremely knowledgeable, and thorough with his explanation about the probing problems. He has an extensive write-up on his forum, with sketches of the circuit, and makes it his business to get probing working, as it is integral to his screen set.

In regard to your question about the LED circuit, the LED is not "IN" the circuit with the probe contacts closed. When the probe contacts
open (only one of three points of the probe can be open, depending on the direction of force on the probe), the voltage still has a path to ground, through the LED+resistor, which is now the only path remaining  to ground, and that tiny current flowing through the LED, still has a voltage with respect to ground. So, the circuit is not at 0v yet; close to 0v, but not 0v.

The above referred to site has a good diagram showing this. Dave also mentions that he has smashed lots of probes, and tips
getting to the solutions.

Mach3 helps build patience.


Re: Wiring Wild Horse Econo Probe
« Reply #6 on: December 02, 2014, 01:29:54 PM »
That MSM looks interesting.  Is it t worth a download?
Re: Wiring Wild Horse Econo Probe
« Reply #7 on: December 02, 2014, 11:59:42 PM »
The MSM screen set is an amazing piece of work. I think he has a trial version, which runs for 30 days to evaluate. Also, he is 100% involved with answering in detail, any questions users may ask. The manual is huge; over 300 pages. I used it for over a year, but have not upgraded to his later versions that work with a probe and touchplate for tool setting and probing.

Re: Wiring Wild Horse Econo Probe
« Reply #8 on: December 03, 2014, 11:16:05 AM »
I have been through his stuff and the MSM is impressive.  There is a personal edition that is free to download and use.  I have downloaded, but not installed it.  I want to finish this bit up before I take the time to read the manual on MSM.

I went through his PDF and tried the tests.  Removing the probe from the BOB I placed a single wire running from gnd to pin 10.  I got a reading of 0 volts, which is what I wanted.  Then cut the wire in the middle and got a reading of 1.4 volts.  This is where I get lost.  Dave talks about the mAmps at this point and I did not test for that.   It just seems that the solution Arthuro has at CNC4PC, wiring a connection and a resistor between the 5v terminal and the wire connected to the input terminal is just likely to get me around 2.5v.  I am not sure this is enough or too much.

What I am going to do is test the BOB by putting a resistor and LED connected to the plain wire I have coming from pin 10 and see if it lights up.  If that works, then I know that I don't need the resistor and 5v connection and the problem is on the probe side.  If it doesn't work, then I will rig it up connected to the 5v and see what happens.  At least I can do this without the probe being in the circuit so I won't blow it up.

I know this is too much info and most folks know this stuff, but I wanted to get it all down so that anyone that is searching for a solution to the problem might find this discussion and save themselves some time.

Thanks again
Re: Wiring Wild Horse Econo Probe
« Reply #9 on: December 03, 2014, 01:08:27 PM »
Alrighty.  My probe works.  The LED does not, but at least my BOB is finally connecting and stopping the move of a G31 command.  I bypassed the stereo plug and using test leads connected the probe directly to the board.  Still didn't work, so I went into the auto set of the input pin menu and determined that the pin should be set to active high.  With the plug I had tried active high and low with no luck, so the problem has to be in the stereo plug.  I have continuity from the plug through the wires, but evidently the circuit looses something in the connection.  I will either get a different plug or just wire it straight through and put up with the inconvenience.

Now I will obsess about that LED light and how to make it work!