pfelecan

I succeeded to answer to the original topic using a Chrome 55.0.2883.91 on Android 6.0.1 but after 3 answers I’m stuck on this one also.

The measurements are between Gnd and 3.3V and the reading is 3.41V, on every one.

Now, even creating a topic is not working anymore but when I retry to create a topic it gives me the same error as previously mentioned. IMHO the data store has an issue.

I am logged otherwise how could I start a new topic?
Anyhow, I logged out and in again to no avail: my submission/reply is not taken into account. I never thought that I have black cats in my ancestry.
Maybe should I start a new topic ?

When I’m measuring the 3.3V supply, i.e. between Gnd and 3.3V sockets on the J7 terminal block I get 3.415V; the same on J8.

By the way, I was quite surprised to see that when you activate the Spin with M03 the voltage is varying between 3.1V and 3.3V measured between the Spin and Gnd on J6, but that it’s another story.

Here is a follow-up:

I’m using an opto-coupler to isolate the inductive
proximity switch and the input to the X min of the
TinyG. Unfortunately it doesn’t work as expected.

The schema of the circuit is https://drive.google.com/file/d/0B5X2WpozISvuV2pjY004eEZESlU/view?usp=sharing

The inductive proximity switch LJ12A3-4-ZBX is connected
to a 12V PSU as follows: the brown wire to the positive,
the blue wire to the negative. When the IPS does not
detect the tension on the black wire (the signal) is 12V;
when the IPS detects the tension drops to 0V.

In order to use an opto-coupler, the Sharp PC817, I connect
the signal to a resistor of 808 Ohm which is connected to
the anode of the opto-coupler; the cathode is connected to
the ground of the PSU. The collector is connected to the
Xmin on the J7 of the TinyG and the emitter to the ground
on the same bank.

In this configuration, the tension measured between the
collector and the emitter is of 3.3V when the IPS is not
detecting and, as expected, the tension drops to 0V when
the IPS is detecting.

I’ve set the switches type to NC with $st=1.

The Xmin type is set to limit with $xsn=2.

However, the board is not reset and the SpDir LED
doesn’t flash when the IPS detects.

Just for completeness I tried with the $st=0 but to no
avail. Also tried the Zmax because it works with a
micro-switch. Finally, I tried also to reverse the
connection on the collector/emitter side to Gnd/Xmin.

I saved the board’s configuration https://drive.google.com/file/d/0B5X2WpozISvub21aek90eUExQWs/view?usp=sharing

My two questions are:

1. Is the circuit correct?

2. If the circuit is correct, why the limit tripping is
not detected?

Yeah, I know, using an SSR is a desperate mean and a perfect illustration of the syndrome of knowing how to use a hammer so that everything seems to be a nail. However, functionally it’s a valid solution even though a little bit over-engineered, isn’t it?

Thank you for your answer.

The issue with these cheap inductive proximity switches is the difficulty to find reliable, i.e. non contradictory documentation. I bought them as NPN NC and, in my foggy understanding, the behavior is NC, i.e the circuit is closed (conducting) when not detecting. This is why I use an empirical method to determine what should be done.

The only data-sheet that I found on the LJ12A3-4-ZBX is:
https://www.alibaba.com/product-detail/M12-Cylinder-inductive-proximity-switch-LJ12A3_60380094925.html

From what you’re writing I understand that you are worrying about a variability of the device’s resistance which will make a variation in the overall characteristics of the circuit and the value of my resistors will have a different effect, i.e. the voltage can be higher or lower than what’s expected.

Still, I have 2 questions:

1. is the circuit diagram correct?
2. what’s the most reliable solution when using these devices to reliably pull-down the tension toward the TinyG?

TIA