Simple Proximity Sensor question

Thread Starter

Jwooky

Joined Mar 16, 2019
11
Hello, I recently purchased these:
https://www.amazon.com/dp/B0872Y3C7D/ref=cm_sw_em_r_mt_dp_wWtWFbRRTRM79?_encoding=UTF8&psc=1


I would like to use the output to drive the control side of a 12V relay. (Either ground or bat doesn't matter)

I’m not clear based on the description, what the output is however. If I hook it up to a 12V power supply and activate it , the output is continuous with both the positive and negative side of the sensor.

Appreciate your thoughts.
 

AlbertHall

Joined Jun 4, 2014
10,908
Providing your relay coil needs less than 300mA then it should be simple. The picture below from the website shows the connections and a 12V supply would be good for the sensor.
The + and - indicate the connections to your 12V supply. The little box connected between brown and black wires is your relay coil.
1606500199576.png
 

MaxHeadRoom

Joined Jul 18, 2013
22,346
I’m not clear based on the description, what the output is however. If I hook it up to a 12V power supply and activate it , the output is continuous with both the positive and negative side of the sensor.

Appreciate your thoughts.
Remember the output is open collector so you need the pull up resistor.
If attempting to drive a relay direct, ensure it is within the current range of the sensor.
Also you need the BEMF diode across the coil.
Max..
 

MisterBill2

Joined Jan 23, 2018
7,981
The connections information is all on that blue tag wrapped around the base of the device shown in the link. So if you can post a good image of that drawing then it will be easy to provide the information that you seek.
 

Thread Starter

Jwooky

Joined Mar 16, 2019
11
The connections information is all on that blue tag wrapped around the base of the device shown in the link. So if you can post a good image of that drawing then it will be easy to provide the information that you seek.
Looks like this.
1607704711548.png
 
Last edited:

Thread Starter

Jwooky

Joined Mar 16, 2019
11
Thank you all. I tried the relay in the position of the box in the schematic as suggested by @AlbertHall and it will in fact operate the relay.

I’m not sure if I understand it still however.
It must be driving the black output to ground?

if so, why would it have continuity with the positive brown side.

keep in mind you are dealing with a ME.
 

Thread Starter

Jwooky

Joined Mar 16, 2019
11
Yes, I forgot that requirement.
Remember the output is open collector so you need the pull up resistor.
If attempting to drive a relay direct, ensure it is within the current range of the sensor.
Also you need the BEMF diode across the coil.
Max..
Sorry, can you explain the need for the diode?
With only 300 mA dosent seem much risk to a 12v system
 

Thread Starter

Jwooky

Joined Mar 16, 2019
11

MisterBill2

Joined Jan 23, 2018
7,981
Thank you all. I tried the relay in the position of the box in the schematic as suggested by @AlbertHall and it will in fact operate the relay.

I’m not sure if I understand it still however.
It must be driving the black output to ground?

if so, why would it have continuity with the positive brown side.

keep in mind you are dealing with a ME.
OK, and WOW! As an EE I had ti take Statics, Dynamics, kinematics, and properties of materials. All of them ME level courses, by my evaluation. Dynamics and kinematics are so useful for understanding the real world, they should be taught in elementary school, on an appropriate level, of course. And the ME folks did need to take circuits 1 and 2, introductory courses.
 

Thread Starter

Jwooky

Joined Mar 16, 2019
11
OK, and WOW! As an EE I had ti take Statics, Dynamics, kinematics, and properties of materials. All of them ME level courses, by my evaluation. Dynamics and kinematics are so useful for understanding the real world, they should be taught in elementary school, on an appropriate level, of course. And the ME folks did need to take circuits 1 and 2, introductory courses.
All true, just stating I’m not an expert and some things not as intuitive.
 

MisterBill2

Joined Jan 23, 2018
7,981
The reason that the back EMF diode is not needed in this application is because the current does not change that fast. The breakingof the beam is not an instant thing, it takes a finite time to happen. With the slower rate of change the spike is a whole lot smaller. It is not that the relay is any different.
 

MaxHeadRoom

Joined Jul 18, 2013
22,346
The reason that the back EMF diode is not needed in this application is because the current does not change that fast. The breakingof the beam is not an instant thing, it takes a finite time to happen. With the slower rate of change the spike is a whole lot smaller. It is not that the relay is any different.
Are you saying a proximity switch does not switch fast??
Often they have Schmidt trigger output. Just as a quadrature optical encoder does.
 

MisterBill2

Joined Jan 23, 2018
7,981
OK, wrong thread! I was thinking of the thread with the photoelectric sensor that the TS called a proximity sensor. THOSE do not change so rapidly. The industrial configuration prox switch may change fairly fast, but usually the good ones all use a high enough voltage rated output transistor to not need the diode.
I have seen way too much grief caused by improperly polarized protection diodes so that I prefer RC snubbers.
 

MaxHeadRoom

Joined Jul 18, 2013
22,346
OK, wrong thread! I was thinking of the thread with the photoelectric sensor that the TS called a proximity sensor. THOSE do not change so rapidly. The industrial configuration prox switch may change fairly fast, but usually the good ones all use a high enough voltage rated output transistor to not need the diode.
Photo electric can just as fast, depends on the internal conditioning, e..g. the slot opto's I use have a Schmidt trigger output.

I have seen way too much grief caused by improperly polarized protection diodes so that I prefer RC snubbers.
If the one setting up the system is proficient, then I would go with Diodes for DC, ;) I reserve the R/C version for AC applications.
Max.
 
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