[Sugar-devel] Pulse Sensor: an Open Source Heart-rate Sensor that Rocks by Yury Gitman ? Kickstarter

James Cameron quozl at laptop.org
Wed Jul 20 00:50:00 EDT 2011

On Wed, Jul 20, 2011 at 12:22:23AM -0400, Kevin Mark wrote:
> On Wed, Jul 20, 2011 at 01:25:31PM +1000, James Cameron wrote:
> > On Tue, Jul 19, 2011 at 08:07:40PM -0700, Sameer Verma wrote:
> > > http://www.kickstarter.com/projects/1342192419/pulse-sensor-an-open-source-heart-rate-sensor-that
> > > 
> > > Minus the Arduino, can this plug into the audio/mic port?
> > 
> > That would be a question for the designers.  I could not figure it out
> > from the context.
> > 
> > I can tell you, based on the Arduino board that is used, and my
> > knowledge of the pinout, that the sensor uses 5V from the board, and a
> > ground, and the signal from the sensor enters one of the Arduino analog
> > inputs.  However, the analog inputs can be used for digital data as well
> > as analog data, so this is inconclusive.
> > 
> > For the XO, the sensor would require 5V power, perhaps from the USB
> > port.
> > 
> > I can't tell if the sensor output is compatible with the microphone
> > input.
> > 
> Do you know what kind of voltage that mic input can handle? 
> +/5 VDC?

I can't tell if the sensor output is compatible with the microphone
input, because I don't know if the sensor output is digital or analog.
Sorry for not making that obvious enough.

But to answer your question literally, the microphone input can handle
from -0.5V to +5.0V DC, beyond which damage will occur unless current is
limited.  The useful range is 0.4V to 1.85V for XO-1.

> this seems like it would be related:
> http://wiki.laptop.org/go/Making_XO_sensors/How_to_connect_sensors

Not really.  That page only describes how to connect sensors, not
whether sensors are suitable, nor whether they will cause damage.

I think
is far more relevant.

But still, without knowledge of the sensor output, we can but speculate.

James Cameron

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