Need help picking technology for a proximity/presence sensor

Thread Starter

Aleksey Shurtygin

Joined Dec 21, 2018
62
Happy New Year!

I need some help trying to sort out technology that I can use for the human/obstacle sensor. I am building a vanity mirror lighting circuit and want it to turn on the LED lights only when person stands in front of the mirror.

I've been looking around and see that there are multiple options. I've seen sensors that are based on IR or ultrasound. I took a chance and bought some IR sensor from amazon. It appears that I somehow missed that it was only working within 30 cm or so. After digging some more it feels like most if not all IR sensors are only working at a close range.

Anyway, I was wondering if someone can provide me some guidance for choosing what technology best fits for the task.

I have a vanity mirror with an opposite wall about a 1 meter (3-4 feet) away. I am not looking at the occupancy sensor, the one that switches when motion is detected. However I may consider it if no other viable options found. I need a sensor that will trigger when someone stands in front of the mirror. The range should be 0.5-1 meters. Also, preferrably that its not complicated to build for a relative beginner.

I am not expecting a full circuit (however would really be helpful) but some direction and explanation will be sufficiend for now.

Thank you in advance!
 

Thread Starter

Aleksey Shurtygin

Joined Dec 21, 2018
62
You can choose the PIR Sensor.
Thanks but this is the one I am not considering yet. I am looking for something more directional. Only in front of the mirror and not while in shower or in the walk-in closet.

I bought this one but its range is too small. https://www.amazon.com/gp/product/B00KVFG9S6 I am looking for something similar.
Product description says that sensor distance is within 25cm which is a bit too short.
 

Thread Starter

Aleksey Shurtygin

Joined Dec 21, 2018
62
LED can be modulated and lenses are just optional.
View attachment 167014
Thanks! I've seen this option as well. Forgot to mention this in my original post. It presents its own challenges. I'd like to avoid pulling wires around the bathroom and opening up walls is out of the question. Wires and hanging LED emitter is not aesthetically pleasing. So, ideally something that emits and receives some signal at the same spot using some kind of reflection.

https://circuitdigest.com/electronic-circuits/ir-sensor-circuit-diagram
I am currently hoping this approach would be sufficient and sensitivity will be acceptable (within few feet). Planning to attach the device under the mirror itself out of the view.
 

MisterBill2

Joined Jan 23, 2018
6,997
There are a number of optical sensors that use a retro reflector and so they only need connections at one point, with the reflector at the far end of the sensor range. That would make installation simpler. But if you have access to the underside of the floor then a version of a capacitive presence sensor would be possible with nothing at all showing, and it would only detect a person in the specified location. A variation of the PIR sensor could also work, one that detected the increased heat from a person, rather than the motion of a person. If there is lighting around the mirror then a system to detect the reflected light from a person in front of the mirror could be effective.
So there are quite a few options available without any thing visible and no external wiring. It all depends on the particular area. So a few more details could help get a better answer.
 

MisterBill2

Joined Jan 23, 2018
6,997
I just looked at the Amazon post, and that device could work if you positioned an IR LED source to reflect off the wall behind the mirror. Then when one stepped in front of the mirror and blocked the IR the light would switch on. Sensitivity might be an issue, though.
 

MaxHeadRoom

Joined Jul 18, 2013
21,402
I think if I were to install that type of sensor/application, I would add a delay-off circuit, this would avoid 'nuisance' or intermittent triggering off etc when in use.
Max.
 

Reloadron

Joined Jan 15, 2015
5,646
Just keep in mind any sensor using a beam be it reflective or not will trigger when the beam is broken. Waking past it will trigger it. I don't know your layout but you may wish to consider that. There are also somewhat reduced sensitivity PIR sensors like those used on toilets and urinals for automation. Then too, if I am that close to a mirror I can turn a simple switch on to illuminate it without any need for automation. There are also the sensors used on sinks in public rest rooms.

Ron
 

Thread Starter

Aleksey Shurtygin

Joined Dec 21, 2018
62
There are a number of optical sensors that use a retro reflector and so they only need connections at one point, with the reflector at the far end of the sensor range. That would make installation simpler. But if you have access to the underside of the floor then a version of a capacitive presence sensor would be possible with nothing at all showing, and it would only detect a person in the specified location. A variation of the PIR sensor could also work, one that detected the increased heat from a person, rather than the motion of a person. If there is lighting around the mirror then a system to detect the reflected light from a person in front of the mirror could be effective.
So there are quite a few options available without any thing visible and no external wiring. It all depends on the particular area. So a few more details could help get a better answer.
This is a rental apartment and for obvious reasons any relatively large-scale options are not feasible. The response below may provide some better idea of the room layout.

I think if I were to install that type of sensor/application, I would add a delay-off circuit, this would avoid 'nuisance' or intermittent triggering off etc when in use.
Max.
Just keep in mind any sensor using a beam be it reflective or not will trigger when the beam is broken. Waking past it will trigger it. I don't know your layout but you may wish to consider that. There are also somewhat reduced sensitivity PIR sensors like those used on toilets and urinals for automation. Then too, if I am that close to a mirror I can turn a simple switch on to illuminate it without any need for automation. There are also the sensors used on sinks in public rest rooms.

Ron
Actually adding delay-off is not a bad idea. I will see if I can add it. The area is rather tight and there is little space for anyone to walk by. So I am not really concerned about anyone walking by. I will try to sketch quick plan if it will help.
 

Reloadron

Joined Jan 15, 2015
5,646
If walking past is not an issue I would look at a ir photo-reflective sensor. Something modular leaving little wiring to do and something non permanent since this is an apartment. Something with a dry contact out which should make it easier to power your LED lighting. Try a Google of "ir photo-reflective sensor".

Ron
 

cspwcspw

Joined Nov 8, 2016
72
I had some fun with these really cheap radar sensors: https://www.banggood.com/5pcs-RCWL-0516-4-28V-3mA-Microwave-Radar-Sensor-Human-Body-Induction-Switch-Module-Prober-p-1193425.html They're cheap, and seemed to work fine over a few meters in my study (although they claim up to 9m detection, I never tried more than about 3 meters). You can adjust three parameters - distance (sensitivity), how long after last sense event before it turns off, and interval time before it can re-trigger. In all three cases you have to add an external component (resistor or capacitor) to make the adjustment.

We have security monitoring in our home. The service provider now advertises quite expensive augmentation-of-IR motion detectors because criminals are increasingly using IR cloaking that renders them invisible to off-the-shelf IR sensors. I suspect this is the basis of the new technology they're deploying.

Peter
 

splud

Joined Jun 30, 2013
15
Doppler radar modules can detect people (and other materials which cause a change in the absorption/reflection of the signal ) on the other side of a solid wood door. That can be useful, but at the same time would be annoying for a vanity, where someone in the next room could trigger it.

It isn't clear whether this is intended to be a near-discrete drive circuit, or if there is a microcontroller involved.

PIR would be reasonably ideal here - they don't require a lot of current. If the field of view is the concern, then recess the PIR sensor element (and its diffuser lens), which will make the FoV narrower. If you're using a uC, you could set the PIR module up to re-trigger, and not utilize a delay, then your uC can get repeated signals while there is detected motion in front of it - a trigger or two might be ignored (someone walking past) while more than that would indicate someone lingering. You can reset your own timeout each time there is a signal from the PIR.

With a uC, you could better fine-tune how the switching responds to the input signal. You could also make use of more than one sensor - PIR + Ultrasonic for instance.

Note that PIR detects a changing heat pattern hitting the halves of its sensor. This shouldn't be confused for "motion detector", though that's what a lot of people refer to a PIR as.
 

jipristt

Joined Jun 4, 2017
20
Does it have to be an optical sensor? How about a mat that can sence pressure when someone steps on it?
This way you can know exactly were to stand to turn on the leds.
You could use forse sense resistors as voltage deviders and then turn on the lights with relays or transistors.
 

MisterBill2

Joined Jan 23, 2018
6,997
The original post was asking for a sensor to switch on a light when somebody stopped in front of a mirror, quite a LONG WAY FROM SECURITY SYSTEM SENSORS.
 

Thread Starter

Aleksey Shurtygin

Joined Dec 21, 2018
62
Sorry for a long delay in responses. I've received IR LEDs and photo diodes I mentioned earlier and was playing around with it. I was actually getting some promising results however as I later found out that it really depends on lighting level. I was able to get meter or two sensitivity when room is only lightly lit (just enough to work comfortably during day-time), but when I turn on the lights, sensor becomes always on until i turn down the sensitivity but then range drops to couple of feet at the most.

This is the simple circuit I was using - https://circuitdigest.com/electronic-circuits/ir-sensor-circuit-diagram.

I also had a PIR sensor that I tried to use (https://www.amazon.com/gp/product/B00KTCTV8G). To my surprise it seemed to exhibited similar behavior. When I tried both sensors in the "field" they would turn on when sun came out and turned off when sun went behind clouds.

Is that behavior expected?

I had some fun with these really cheap radar sensors: https://www.banggood.com/5pcs-RCWL-0516-4-28V-3mA-Microwave-Radar-Sensor-Human-Body-Induction-Switch-Module-Prober-p-1193425.html They're cheap, and seemed to work fine over a few meters in my study (although they claim up to 9m detection, I never tried more than about 3 meters). You can adjust three parameters - distance (sensitivity), how long after last sense event before it turns off, and interval time before it can re-trigger. In all three cases you have to add an external component (resistor or capacitor) to make the adjustment.

We have security monitoring in our home. The service provider now advertises quite expensive augmentation-of-IR motion detectors because criminals are increasingly using IR cloaking that renders them invisible to off-the-shelf IR sensors. I suspect this is the basis of the new technology they're deploying.

Peter
Thanks, but this seems to be over my head at this point. Too complicated for my level and my project.

Doppler radar modules can detect people (and other materials which cause a change in the absorption/reflection of the signal ) on the other side of a solid wood door. That can be useful, but at the same time would be annoying for a vanity, where someone in the next room could trigger it.

It isn't clear whether this is intended to be a near-discrete drive circuit, or if there is a microcontroller involved.

PIR would be reasonably ideal here - they don't require a lot of current. If the field of view is the concern, then recess the PIR sensor element (and its diffuser lens), which will make the FoV narrower. If you're using a uC, you could set the PIR module up to re-trigger, and not utilize a delay, then your uC can get repeated signals while there is detected motion in front of it - a trigger or two might be ignored (someone walking past) while more than that would indicate someone lingering. You can reset your own timeout each time there is a signal from the PIR.

With a uC, you could better fine-tune how the switching responds to the input signal. You could also make use of more than one sensor - PIR + Ultrasonic for instance.

Note that PIR detects a changing heat pattern hitting the halves of its sensor. This shouldn't be confused for "motion detector", though that's what a lot of people refer to a PIR as.
I may be one of those people. Is there a good article or resource on that? Which motion detector are you referring to (image based or IR)? I actually now considering ultrasonic. I was searching around for a sensor and only can find the ones that are used with adruino. I also did some search if there is a way to use those sensors without adruino and found this article. Anyone knows if that approach makes sense and may work? https://www.buildcircuit.com/how-to-test-dyp-me007-ultrasonic-range-finder-using-ne555-and-multimeter/

On some other sites I've seen people mentioning that its not possible or hard to do. So, being suspicious on whether this actually works.

Does it have to be an optical sensor? How about a mat that can sence pressure when someone steps on it?
This way you can know exactly were to stand to turn on the leds.
You could use forse sense resistors as voltage deviders and then turn on the lights with relays or transistors.
I would like to avoid to pull any wires around too much (on the floor in case of the pressure sensor). It will get in a way when someone will try to wipe the floor, and also it being in the bathroom it has a chance of getting drops of water.

The original post was asking for a sensor to switch on a light when somebody stopped in front of a mirror, quite a LONG WAY FROM SECURITY SYSTEM SENSORS.
Yeah, not looking for anything complicated. If nothing works that is simple enough for me, I will go for simple IR wave switch. Simple IR LED/photo diode combo should work fine in this case in any lighting conditions.
 

Thread Starter

Aleksey Shurtygin

Joined Dec 21, 2018
62

djsfantasi

Joined Apr 11, 2010
6,792
Are you using a microprocessor to process the signal? Or are you thinking along the lines of a stand-alone sensor? One that provides a binary person/ no person output?

Perhaps you could use an ultrasonic sensor. This one has a range of 1”-13’.

A simple microprocessor can process the output and provide your binary output. I’d recommend either an Arduino Nano or an ATTiny85.

Or you might be able to design a stand-alone circuit.
 
Top