Hi guys

As of the title saiys, thanks guys!

I have already look at those sensor mat type solution (two sheets of conductor sandwich a thin sheet of foam), they are too easy to break. I am hoping something I can attach to a bed/frame/legs/etc.. and somehow I can do the detection.

Thoughts??

Thanks guys!!

 

Small flat load cell?
Max.

 

Small flat load cell?
Max.

Good idea!! Are you suggesting putting it under 4 legs??

 

Some hospital beds are capable of weighing people in the bed. You'd likely need 4 sensors, one for each leg if you go that far.
It would likely be the most reliable.

You could probably get away with two at the head of the bed feet and check the additive weigh distribution on the two feet. Raise the other legs to compensate for no sensor.

Check www.omega.com under load cells.

A non-load cell cheap sensor https://www.sparkfun.com/products/8685.
<$20.00 USD

The evaluation kit from tekscan is pricy.

 

Hi guys

As of the title saiys, thanks guys!

I have already look at those sensor mat type solution (two sheets of conductor sandwich a thin sheet of foam), they are too easy to break. I am hoping something I can attach to a bed/frame/legs/etc.. and somehow I can do the detection.

Thoughts??

Thanks guys!!

How many legs does the bed have?

The first thing that comes to mind is a small load cell under each leg, but you might get away with a single load cell under just one leg since you aren't trying to weigh the person, just detect that the load has gone up. How will it be monitored? I can imagine that things get set on an empty bed that would be heavy enough to be seen as a person on a fairly frequent basis.

Depending on the frame structure, another possibility might be putting a strain gauge on the bed frame somewhere.

 

How many legs does the bed have?

The first thing that comes to mind is a small load cell under each leg, but you might get away with a single load cell under just one leg since you aren't trying to weigh the person, just detect that the load has gone up. How will it be monitored? I can imagine that things get set on an empty bed that would be heavy enough to be seen as a person on a fairly frequent basis.

Depending on the frame structure, another possibility might be putting a strain gauge on the bed frame somewhere.

Just a typical 3 legs bed. Strain gauge is another good idea.

 

Just a typical 3 legs bed.

3?

 

Just a typical 3 legs bed. Strain gauge is another good idea.

I'm not at all familiar with a typical 3 legs bed. Did you mean 4 legs?

I would imagine that a strain gauge midway along one of the head-foot rails will give a usable signal.

 

Ooops, I mean 4, duh!

 

How about an infrared detector? or a microswitch on a lever underneath mattress
from centre of the bed to a leg or frame?

 

How about an infrared detector? or a microswitch on a lever from centre of the bed to a leg?

How do you plan to detect with infrared? Could be not reliable in my opinion, unless what you are suggesting is different from what I got in mind.

And about the micro switch, are you suggesting a lever from the bottom centre?

 

The challenge with PIR (infrared) devices is they only detect change. If someone hops in bed then falls asleep (stops moving), you'll see the motion when they arrived, but you won't know if they're still there or not. A load cell is probably the most reliable. I don't know if an FSR would work or not. It would behave similar to a load cell (resistance changes with load) and it's very thin and relatively inexpensive, but I don't think they're as linear as load cells. Something like this, but with a higher rating:

http://www.kr4.us/force-sensitive-resistor-0-5.html

 

Infrared as in the way an alarm sensor works, aim it at the bed from a wall etc.
and without seeing the bed I can't say where to put the microswitch lever, but seeing as there must be some deformation of the mattress and whatever it is on, there must be someway to fit one.

 

Ive just thought of another cheap way, you can buy a pressure switch mat that goes under carpets used in alarm systems. put one between the mattress and bed base.

 

Even though you say they break easily, these are supposed to be tough. The poor ones just have a soft foam inside, have a look at the medical fall mats.

Digiteck
B7-HIDDEN PRESSURE ACTIVATED MAT ALARM CHIME ALERT/STAIR MAT FOR INTRUDER ALARM
On Amazon

• 

Click to open expanded view

Arun Large Pressure Mat (700mm x 560mm)

 

Hi guys

As of the title saiys, thanks guys!

I have already look at those sensor mat type solution (two sheets of conductor sandwich a thin sheet of foam), they are too easy to break. I am hoping something I can attach to a bed/frame/legs/etc.. and somehow I can do the detection.

Thoughts??

Thanks guys!!

Someone on this forum occasionally posts; "Nurse - they're out of their beds again!!!" - probably just right for this application.

 

Could you show us how is the bed look like?

For the IR sensors then you can put them at two sides of the bed, maybe three pairs.

 

Good idea!! Are you suggesting putting it under 4 legs??

Omega is a little steep for load cell prices prices, there are fairly flat ones on ebay, you could use just one and then even up on the other leg with a shim the right height.
Max.

 

Even though you say they break easily, these are supposed to be tough. The poor ones just have a soft foam inside, have a look at the medical fall mats.

Digiteck
B7-HIDDEN PRESSURE ACTIVATED MAT ALARM CHIME ALERT/STAIR MAT FOR INTRUDER ALARM
On Amazon

• 

Click to open expanded view

Arun Large Pressure Mat (700mm x 560mm)

These break easily

 

Could you show us how is the bed look like?

For the IR sensors then you can put them at two sides of the bed, maybe three pairs.

Not the same one, but could be something like this, also, I properly prefer to have the sensor stay with the bed, not on a wall of a room. Unless, the senor is portable.