Reverse Engineering a circuit.

[D.A.(Tony)Stewart]

Sorry your specs are inadequate to design a reliable solution due to reflectivity of object range, skew motion, room reflections etc. It would be complicate to focus ultrasound, or laser without scattering and invalid measurements.

So again I say why not keep it simple ... How 4 narrow beam ultrabright 5mm LEDs in a light guide tube. (5mm black heat shrink)

LED's Horizontally emitting just below shoulder height but separated and by 1 meter and each pair of crossing beams overlaps at the desired position your want from reference points.

If they move until the beams converge, it might look as below. I chose a pair of blue to aim at left should and a pair of red for the right shoulder. with a Red Blue pair separated by say 1 m so slightly less than 45deg cross beams.


aligned at right distance.

aligned but wrong distance

misaligned on left shoulder only

One arrangment of LEDs cast across shoulders intersecting on chest..

User has a mirror to aid in visual alignment.
Does that work for you? if not why not?

 

[stephkre]

Now I get what you mean about the cross beams. I could mount a mirror on the device that would show the dots. That is a very easy way to produce the outcomes. The only issue I see is when it is outdoors you could get the reflection of the sun shining right at you. I like this as a good solution. However you do not think that I could be able to produce an ultrasonic solution also which would produce a nicer product? I used the laser distance device on many different materials of clothing and I have been able to get very accurate readings, but I think a laser device would be over kill and ultrasonic now that I have looked into it more would be a good solution also if I can test it in many different scenarios and it still gives a good reading. I don't think it will take me long to throw together a ultrasonic sensor and try that out. What you think?

 

[D.A.(Tony)Stewart]

You should have included in your design spec ambient sunlight as part of the environmental spec.
Laser LED's are cheap. and you can pulse them on and off.< 1/4 sec and they will be much brighter than the sun.

Ultrasonic will not be accurate with broad beam without beam scanner ($)
Optical is better.

You can also use interrupter beams across the subject below shoulder height. (which you should also have a spec for)

You could also use VHF Tx antenna with Return Loss bridge running between 1/4 & 1/2 wavelength. CHeap but requires too much explaining and may be too reflective for large subject vs tiny at same distance.

 

[stephkre]

I thought about the barrier beams in which when the person breaks the beam ill get a signal however that would not give the person a sense of direction on which way to lean or twist.

Thats sad that the ultrasonic wont work. I looked at the site you sent me for ultrasonic sensors and it looked promising. Your saying it will be a broad beam due to the surface it will be hitting? How certain are you that it wont be able to give me accurate enough data? I'm asking because I don't know much about ultrasonic except what I have research over the past couple days.

Im having a feeling this device wont be able to be as sophisticated as I thought it would be. I thought a person would be able to walk up to where the beams line up with the each side of the upper part of the chest and lean forward or twist based on the indications the device gives off through leds.

 

[D.A.(Tony)Stewart]

in order for the signal to be directional the wavelength has to at least be of the order of magnitude of the distance (VHF) or much smaller ( IR, optical) but audio or ultrasonic is many times that distance so even a small aperture the sound directed in a pipe would radiate in a Lambertian wide angle. However, that is not to say direction audio pipes cannot be made with parabolic dishes or Helmholtz resonators but very poor acuity.

I was think sonic was ok until you said both shoulders had to be same distance.

 

[stephkre]

I think IR is out of the questions due to the different colors that it will need to reflect off of.(Black) I will look into optical sensors and get back to you.