Position sensor - or something

continued from https://www.ghielectronics.com/community/forum/topic?id=13512&page=2#msg219264

I’ve got a bit of weird scenario where 10 g120 products are on a production conveyer and going around in circles. There is power on the line that they are connected to through some brushes. Once on the conveyer they are networked with CAN. But in order to function they need to know what zone they are in after a power out etc. I’d like do use IR or some type of light beam. So that on startup. the one in the beam can know it’s position and relay the info to the others.

Any Idea’s, I’d like the range to be at least 1m but closer to 2 is better. And it has to have about a 1m wide beam at that range.


do you have any type of drawing or pictures of the applications? Its kind of hard to visualize what you have.

How far apart are the G120’s from each other?

I’d just like to see if I understand the setup. You’ve got a circular conveyor with 10 G120s spaced roughly evenly around the belt. You’d like to “light up” a 1 meter segment of the belt so any G120 in the “spot light” knows it is in the spot light and can tell all the other G120s it is “the one”. And you’d like the spot light to be 1 - 2 meters away from the G120s.

Is that anywhere close to being right? If so, there are a variety of light sensors that might work. The kind of thing you see at the bottom of an automatic garage door opener. The module on one side of the door is a light source. The module on the other side is a receiver that sets its output high when it is lit up by the source. When your dog runs through the beam and the sensor doesn’t see any light, it’s output goes low. Put the light source above or to the side of the conveyer. Connect a receiver to every G120 on the conveyor. When a G120 enters the light beam, its output goes high. All the other G120s are low. You’ll have to find a source with the right beam pattern for your geometry.

Here are some examples: McMaster-Carr McMaster doesn’t give the manufacturer but companies like Omron, Banner Engineering and maybe Honeywell and Turck make this kind of stuff. Try googling “light beam sensing switch” There are also ultrasonic and IR devices that do the same thing.

You can also find similar stuff at Digikey and Newark that might work.

@ skeller You call on me to embarrass myself with a picture? Doh!

Just a thought, here is a schematic that mimics a remote control, (both RX & TX).


The interesting thing is, if you already have a G120, just use the front end from the schematics, to drive the TX, or RX.



The RFID reading is not 100% reliable (maybe not 50% for something moving with any more than trivial velocity). Is there any reason that a simple hall-effect sensor and a magnet is not good enough?

@ mcalsyn - I don’t think that I can get that type of range and spread from a magnet system. but correct me if I’m wrong.

What’s wrong with these.

The g120s aren’t moving that fast, only about 20cm a second max.

@ stotech - you only need position after an outage right? why?

Always need it, sorry I didn’t explain well. What I was trying to say was the width of the beam needs to be so, that it covers 2 units wide so that if the power cycles. There wont be a scenario where it has no clue of position.

@ stotech - The sketch you provided looks pretty much like exactly what the sensors I suggested are designed for. The ones I described are called something like direct or through beam photoelectric sensors. They also make reflective types where the transmitter and the receiver are one unit which you connect to the G120 and just mount a reflector or reflectors or a reflective strip at some convenient place.

I propose a 10.95 USD solution.
You paint, along ths belt, some kind of very simplified bar code representing the position.
on the G120 side, you put a GHI camera module or some other cheap camera, no need for a high frame speeed.
Just be sure at least one mark is always in the field of view of the camera.
Extracting the mark from the image will be trivial.
You will be able to know the location of the belt with a precision of a few % of a slot.
You may even, with a little more code, check continuously the speed of the belt, early detect a stall, of provide some information to external systems.

@ Gene - I need to make hundreds, and the cost of those retro reflective sensors would add up to too much and sink the budget. Even if I were to use the cheaper ones from Omron.

@ SouthernStars - I sort of went down that route for a while until I went out to see the machine in action, it’s a filthy, wet and dirty nightmare. Got to be IP65 at least I recon. With some sort of light solution I’ve just got to get them to keep a little window clean on both units.

Would ultrasonic work? Check out www.maxbotix.com
They sell outdoor rugged ultrasonic sensors with a range of up to 10meters.

Someone might sell a TX and RX version that would work similar to a light beam.

Perhaps you must provide more information if you want some help.
Having windows on each device and maintaining them clean has probably a cost higher than the electronic devices by themselves.
May you provide some pictures of the real machine?
Did you consider a camera (WiFi ?) at the level of the ceiling and seeing the belt from above.
There is probably some clean places in the machine, like the motor and you may capture the information from here…

I am not sure what you really have there but from what I have read I would think that hall effect sensors are what you need.

Ok, wet / dirty environment, Info that wasn’t previously available. Just a suggestion, as it already connects to lines on the conveyor, is add one more line, without doing the math, as not enough info available, a 1k resister every 10’ / 50’, what ever makes sense. Add a 12v / 24v, again, what makes sense power supply, and read the voltage. Knowing the voltage would tell you where you were at. No sensors needed, other than the built in A/D, a powersupply, and some radio shack resistors…
Nothing to keep clean, and if your connections is good enough for communication, should be good enough to read the voltage.