detect pressure of the arm coming together

Thread Starter

athulascc

Joined Aug 15, 2014
94
hi
I am developing simple circuit where I am trying to detect pressure when arms coming together when hand bended. the device will be placed near the L bow of hand and when user bend the arm, the device measure the pressure and beep if pressure is higher than set limit.

I know micro controller programming and pcb design but I need assistance for selecting proper pressure sensor for this application. I do not have idea normal range of pressure applied when arm is bended. the device will be placed here, check the picture below.
Attachment_1625625961.jpeg

can anyone tell me the range of pressure I should consider when selecting the pressure sensor and the type of pressure sensor which match for this application.

Thank you
 

RBR1317

Joined Nov 13, 2010
674
Not sure what you are trying to measure. Compression is normally something applied to the arm with a blood pressure cuff, and the air pressure in the cuff is measured. But if you have a band around the arm, then the expansion of the muscles in the arm could generate tension in the band which might possibly be measured with a strain gauge. You may find it necessary to manufacture this band/gauge yourself.
 

Thread Starter

athulascc

Joined Aug 15, 2014
94

Thread Starter

athulascc

Joined Aug 15, 2014
94
Not sure what you are trying to measure. Compression is normally something applied to the arm with a blood pressure cuff, and the air pressure in the cuff is measured. But if you have a band around the arm, then the expansion of the muscles in the arm could generate tension in the band which might possibly be measured with a strain gauge. You may find it necessary to manufacture this band/gauge yourself.
This idea is good but bit complicated. when arm is bended there is a force like this attached picture, I want to measure it
 

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Irving

Joined Jan 30, 2016
2,308
A small air-filled bladder connected to an air pressure gauge such as these from Panasonic. But be careful to choose the right type and sensitivity.

The bladder could be as simple as a short length of thin-walled 5mm silicon rubber tube blocked at each end with silicon sealant and a length of 2mm tubing to the sensor embedded in the seal at one end of the bladder.
 
Last edited:

sparky 1

Joined Nov 3, 2018
607
This is how I reword the question.
Which arduino thin film pressure sensor with module is available with sufficient source code and working examples
that will be the closest to my biosense application ?
 

shortbus

Joined Sep 30, 2009
8,952
when arm is bended there is a force like this attached picture, I want to measure it
Why? That area is probably going to be a very small force in arm movement as it is just a joint with muscle attachment points, a bio-metric hinge, not a muscle. And will change much depending on what load the arm is doing.
 

MrAl

Joined Jun 17, 2014
8,548
This idea is good but bit complicated. when arm is bended there is a force like this attached picture, I want to measure it
That's a cute picture did you draw that?
It is a good illustration i dont often see one that good.
It looks like a woman's arm because of the hand and nails and even the way the fingers are positioned.
If you did draw that i would love to see how you would draw the rest of 'her' too :)

The main reason i am replying though is to mention another aspect of this kind of project which is the human aspect which might be called "ergonomics" or "human factors engineering".
This is the study and application of design ideas that affect the human associated with the device such as a keyboard, mouse, some kind of tool or other device that a human has to use or be around usually over a lengthy time period but i guess it could also be a short time period.
For this project that would equate to comfort during and after use and there may be other related issues to consider.

As for comfort one thing i can see that might come up is the pressure the device may put on the human operator's skin where it digs in a little and causes operator stress during use. The other is after use it may leave marks on the skin because of the way the 'band' fits around the arm and this would cause itching after use.

Sometimes the appearance can affect the use of the device also such as shape or color and possibly print patterns. If it looks stylish the operator will feel more comfortable with it than if it looks like a strange out of place piece of junk hanging off of their arm.

So some thought has to go into this from the perspective of the human operator too.

In my experience over the years i have seen these kinds of issues come up many times. Some were related to the appearance which doesnt affect the working properties of the device but just looks bad. Others were purely operational where one user performs the operation slightly different than another so the effectiveness of the device suffers, and others were so bad that the users didnt want to have to be associated with the design in any way if they could help it.
For this last one, it was a very very large power converter the size of a typical clothes closet. It made so much of a buzzing noise during operation that the users were constantly complaining when they had to sit in the same room with it (which was a computer room where employees had to be in for long periods of time). The only way out of this was with a retrofit to quiet down the buzzing noise which came from the large transformers inside. That was a lesson learned that was carried over to other future designs.
 
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Phil-S

Joined Dec 4, 2015
224
I can't work out what you want to measure.
Is it the pressure between the lower arm and the upper arm measured at the inside surface of the elbow joint?
I ought to know the specific terms for these positions as each bone in arms and legs has a distal and a proximal end when measured relative to the heart.
For example, a DVP (distal volar plate) is a plate fitted to a broken wrist where the ulna or radius bone is broken close to the joint.
I would think the simplest solution would be, as mentioned before, a bladder of some sort, something like a scent bottle sprayer bulb, and a simple digital or sphygmomanometer dial gauge.
Alternatively, use some calibrated eggs and see how long it takes to break them. Might need Popeye biceps, though.
 

Juhahoo

Joined Jun 3, 2019
249
the question is again too much lacking info, what are we trying to measure and why? is the device mobile or how is it supposed to use/work operate and when ?
 

djsfantasi

Joined Apr 11, 2010
7,913
the question is again too much lacking info, what are we trying to measure and why? is the device mobile or how is it supposed to use/work operate and when ?
Is there a reason that you want it inside the elbow? If you mount it on the outside, the distance between two points on the arms will be minimal when the elbow is extended; longer when the elbow is bent. A simple stretch resistor can be used to fairly reliably determine the bend.
F1C55249-B785-42B4-BFD0-1172FDF922BE.jpeg
 
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