PDA

View Full Version : Proximity Sensors / Mach3 not showing



dudz
12-06-2013, 09:09 PM
I have wired in 2X Proximity sensors on the X axis on my cnc. Ebay Item 32113180610 (http://www.ebay.co.uk/itm/321131806103)
I am using a USB BOB (Ebay Item number 26116368592 (http://www.ebay.co.uk/itm/251261559067))

The normal micro switches I have on Y and Z axis work fine, but I want to use Proximity switches for X, as they will get splashed with liquids.

I have used the BOB DC +5V supply to power the P switches (as it states on the specs 5-24V). I have tested the output of both the switches which is again 5V DC. Plus the LED on the switches light up when metal is passed over the sensor part *all good so far*. But the BOB does not light up its input LED's, Nor does Mach3 diagnostics recognise that there is anything connected to these pins (14 / 15). I have tryed swapping to other input pins, and all the ports and pins settings in Mach3 are correct.

Any Ideas ?

msanderson
12-06-2013, 09:31 PM
I use prox sensors on my system. I used 24vdc and ran the output to a relay. I then wired the contact in the relay to the BOB. The transistor in the prox sensor never really is going to operate the input pins directly reliably. Thanks. Mike

m_c
13-06-2013, 12:45 AM
fedupwiththecontinualchanges.

dudz
13-06-2013, 07:29 AM
When I test across the connections on the bob it shows 0V

CNC Controller Mill Router Home & Limit switch Proximity Sensor Panic Button | eBay (http://www.ebay.co.uk/itm/321131806103?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649)

http://www.ebay.co.uk/itm/CNC-3-axis-USB-Mach3-200KHz-interface-breakout-Card-Adapter-windows2000-XP-Vist-/251261559067?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item3a805b211b

dudz
13-06-2013, 07:33 AM
I use prox sensors on my system. I used 24vdc and ran the output to a relay. I then wired the contact in the relay to the BOB. The transistor in the prox sensor never really is going to operate the input pins directly reliably. Thanks. Mike


I use a 48V DC supply for my Drivers/Motors. I hope I have not got to start adding more PSU's or relays. The reason I chose these Sensors is because it shows them wired to the PC +5V supply and directly into the input pins on the BOB.

dudz
13-06-2013, 07:39 AM
Contacted the Ebay Member with the sensors. Replyed that I can go direct to the parallel port without the BOB. I guess I just change the "Port" setting in Mach3 "ports and pins" ?

9048

cropwell
13-06-2013, 10:20 AM
This is just as unlikely to work as the problem could be switching reliability at the 5v end of the operating supply voltage range. The BoB I use is voltage switchable would not run the sensors at 5v and so the inductive switches now operate at 12v. I would never advise going directly in to a printer port, unless you have a ready supply of spare computers.

Cheers,

Rob - A man of great girth.

Jonathan
13-06-2013, 11:46 AM
Contacted the Ebay Member with the sensors. Replyed that I can go direct to the parallel port without the BOB. I guess I just change the "Port" setting in Mach3 "ports and pins" ?

9048

It doesn't say in the listing (Edit: Just spotted the datasheet in the eBay listing, which does say open-collector), but the inductive sensors are probably an open collector output, in which case you need a pull-up resistor from the signal to +5V. Use something like 4.7k, exact value isn't critical.

You're much less likely to have problems with noise if you use a breakout board and run the sensors at a higher voltage. Connecting to the parallel port directly can work, just make sure you connect it up correctly on the first go otherwise the port could be damaged.

m_c
13-06-2013, 11:51 AM
allmyworthwhilepostsaregoing

dudz
13-06-2013, 02:03 PM
in which case you need a pull-up resistor from the signal to +5V. Use something like 4.7k, exact value isn't

Ok, So it "may" work if I add the pull up resistor while still using the +5v power and the USB BOB?
Other than that I would need to use 43V (my PSU is set at) and use a resistor to lower the power into the Sensor ?

m_c
13-06-2013, 02:31 PM
8901234567

dudz
13-06-2013, 02:53 PM
So after the resistor is in place from the output wire to the +5v, if the switched wire goes to Gnd, does that mean the 5v will go to ground also ? (sorry for my lack of understanding)

dudz
13-06-2013, 04:15 PM
Ok, I understand now. I wasnt sure if the resistor was enough to stop the voltage going to Gnd and damaging something.

m_c
14-06-2013, 12:36 AM
abcdefghij

Jonathan
14-06-2013, 12:45 AM
The resistor is sized so that when the output switches to ground, there's only a few milliamps flowing through it.

I just ran the figures, and with a 4k7 resistor connecting 5V to ground, it's only allowing slightly over 1mA through, so you could use a lower resistance value.
Using a standard 1/8W resistor, you could go as low as 200ohm before resistor overheating becomes a problem. I'd personally opt for something in the 1-2K range, but it's not critical.

Resistor overheating isn't the limiting factor. With 200 ohms you'd have 5/200=25mA. The parallel port can (apparently (http://www.edaboard.com/thread49356.html#post223577)) only source/sink about 14mA, hence to avoid damaging the port if connecting directly I'd use something higher. So I'd agree to sticking with at least 1k just to be on the safe side.

m_c
14-06-2013, 01:09 AM
xyz123abc.

dudz
14-06-2013, 07:42 AM
Some specs from the BOB Manual

9053 9055

9054 9056


The Sensors are NPN.

m_c
14-06-2013, 02:38 PM
mycncuksucks

irving2008
14-06-2013, 04:45 PM
Looking at that, the inputs require 7mA at 5V, which somewhat complicates things if using a NPN sensor, as the inputs obvisouly have resistors installed to drive the Optos.

I've got to head to work now, but if nobody has replied by later, I'll figure out some values to use the sensors you have.

assuming 1.2v forward voltage on the opto means that the existing series resistor is (5 - 1.2)/.007 =542, so probably 560R. the suggested series resistors of 1,5k for 12v and 3k for 24v give currents of 6.9mA and 6.4mA respectively.

dropping the 'on' current to 5mA will need a pull up resistor of 220R and the 'off' current through the 220R would be (5-.4)/220=21mA and 0.1W dissipation, needing a 0.25W resistor. I guess 5mA through the opto will be ok and not have noise immunity issues.

It would be better to use a higher supply rail, e.g. 12 or 24v and use the suggested 1k5 or 3k resistors 'off' current/power being 7.7mA/0.1W or 7.9mA/0.2W respectively.

dudz
14-06-2013, 06:40 PM
Ok... I have a spare PC PSU. 12V (Model LC B200SFX)

If I use this to power the sensor, I connect the PSU -0V to the sensor and to the Gnd terminal on the BOB as shown "right ?" plus the +12V to the sensor input. Using the 1K5 to limit the input to the BOB.
Do I still need a pull up resistor ?..... Its getting a bit confusing for me.

m_c
15-06-2013, 12:47 AM
6543210987

dudz
15-06-2013, 09:47 AM
I feel a bit annoyed with myself. I had a diploma in Electronics servicing in 1986. I looked at my college folder from back then, And to be honest I don't understand much of it now. There was more work in Electrics rather than electronics back then, so didn't take it any further.