AVR-Chat

I don't think a reliable solution (e.g., cannot alter existing
handrail and/or deal with a gloved hand) is feasible.
--- In AVR-Chat@yahoogroups.com, xolang1 <xolang1@...> wrote:

>
> Hi again,
> 
> There is this 3 meter long "stainless" hollow metal rod.
> This is the kind of material used in hand railings and
> barriers. A person might grasp anywhere along the length
> of this rod.
> 
> The requirement is for an AVR to be able to detect if a human hand
> is there or not(a 1 or 0 will do).
> 
> Was thinking of capacitance sensors, however, I havnt seen one
> that uses a rod instead of a metal plate.
> 
> Anyone here encountered one? or is there a better way to do this
> kind of sensing?
> 
> thanks
> 
> chris
>

Hi again,

There is this 3 meter long "stainless" hollow metal rod.
This is the kind of material used in hand railings and
barriers. A person might grasp anywhere along the length
of this rod.

The requirement is for an AVR to be able to detect if a human hand
is there or not(a 1 or 0 will do).

Was thinking of capacitance sensors, however, I havnt seen one
that uses a rod instead of a metal plate.

Anyone here encountered one? or is there a better way to do this
kind of sensing?

thanks

chris

----- Original Message ----- 

From: "xolang1" <xolang1@yahoo.com>
To: <AVR-chat@yahoogroups.com>
Sent: Wednesday, November 19, 2008 6:12 AM
Subject: [AVR-Chat] touch sensor?


> Hi again,
>
> There is this 3 meter long "stainless" hollow metal rod.
> This is the kind of material used in hand railings and
> barriers. A person might grasp anywhere along the length
> of this rod.
>
> The requirement is for an AVR to be able to detect if a human hand
> is there or not(a 1 or 0 will do).
>
> Was thinking of capacitance sensors, however, I havnt seen one
> that uses a rod instead of a metal plate.
>
> Anyone here encountered one? or is there a better way to do this
> kind of sensing?

Make it an element of an RF oscillator and detect the change in frequency 
when it is grasped?

Leon

----- Original Message ----- 

From: "John Samperi" <samperi@ampertronics.com.au>
To: <AVR-Chat@yahoogroups.com>
Sent: Wednesday, November 19, 2008 9:09 AM
Subject: Re: [AVR-Chat] touch sensor?


> At 07:55 PM 19/11/2008, you wrote:
>>Make it an element of an RF oscillator and detect the change in frequency
>>when it is grasped?
> 
> What happens if the rod is outdoor and it is raining?

I assumed it was indoors.

Leon

At 07:55 PM 19/11/2008, you wrote:
>Make it an element of an RF oscillator and detect the change in frequency
>when it is grasped?

What happens if the rod is outdoor and it is raining?

Regards

John Samperi

********************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Website  http://www.ampertronics.com.au
*Electronic Design * Custom Products * Contract Assembly
********************************************************

The railing is located indoors.
Its ok not to detect gloved hands. what is important is 
to detect bare hands.

--- On Wed, 11/19/08, John Samperi <samperi@ampertronics.com.au> wrote:

> From: John Samperi <samperi@ampertronics.com.au>
> Subject: Re: [AVR-Chat] touch sensor?
> To: AVR-Chat@yahoogroups.com
> Date: Wednesday, November 19, 2008, 5:09 PM
> At 07:55 PM 19/11/2008, you wrote:
> >Make it an element of an RF oscillator and detect the
> change in frequency
> >when it is grasped?
> 
> What happens if the rod is outdoor and it is raining?
> 
> Regards
> 
> John Samperi
> 
> ********************************************************
> Ampertronics Pty. Ltd.
> 11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
> Tel. (02) 9674-6495       Fax (02) 9674-8745
> Website  http://www.ampertronics.com.au
> *Electronic Design * Custom Products * Contract Assembly
> ********************************************************

On Wed, Nov 19, 2008 at 1:12 AM, xolang1 <xolang1@yahoo.com> wrote:

>   There is this 3 meter long "stainless" hollow metal rod.
> This is the kind of material used in hand railings and
> barriers. A person might grasp anywhere along the length
> of this rod.
>
> The requirement is for an AVR to be able to detect if a human hand
> is there or not(a 1 or 0 will do).
>
> Was thinking of capacitance sensors, however, I havnt seen one
> that uses a rod instead of a metal plate.
>




The inductive based ones from Microchip would not have glove issues.
Capacitive based ones would, as well as water issues.
Here is a comparasion chart:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2599&param=en531501


-- 
http://www.wearablesmartsensors.com/
http://www.softwaresafety.net/
http://www.designer-iii.com/
http://www.unusualresearch.com/


[Non-text portions of this message have been removed]

At 08:20 PM 19/11/2008, you wrote:
>The railing is located indoors.
>Its ok not to detect gloved hands. what is important is
>to detect bare hands.

I have used the Qprox (now Atmel) chips with touch pads.

They have some good application notes and it may just do the trick.

I guess other techniques would work well in doors.

Regards

John Samperi

********************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Website  http://www.ampertronics.com.au
*Electronic Design * Custom Products * Contract Assembly
********************************************************

> I have used the Qprox (now Atmel) chips with touch pads.

You may be able to do this by hitting the rail with a short pulse and
measuring ringing or reflection time.
Depends too on how the rail is mounted.

There's always the theremin approach, output is a frequency.
You can auto-zero on slow changes, and accept a fast drop in the
variable oscillator's frequency as the touch event.

Theremins are surprisingly sensitive, at least when properly tuned.
Mine will detect my breathing at about 1-2 meters reliably.