Searching \ for '[EE] Very low power khz IR detector' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/io/irs.htm?key=ir
Search entire site for: 'Very low power khz IR detector'.

Exact match. Not showing close matches.
PICList Thread
'[EE] Very low power khz IR detector'
2007\07\05@064913 by Forrest Christian

flavicon
face
I need to build a circuit which will detect the presence of "modulated"
IR... aka the type that comes out of almost any remote control.  The
output will wake a PIC10F to blink a led in a predetermined pattern.  I
don't need to decode the IR, but it does need to discriminate modulated
IR from DC IR (light) and ~60Hz IR (Fluorescent).  It is ok if this just
doesn't work when DC or 60Hz light is present as this device will
typically only be used in low light conditions.

The catch?  This needs to be battery powered, and small, and be able to
idle waiting for an IR signal for months at a time without battery
changes. I've been trying to figure out an option for this, but all of
the modules I see takes around 1-2ma, which doesn't equate to "months at
a time" on either 9V or 4AA's.

Any ideas?

-forrest




2007\07\05@072216 by Rich

picon face
If your intention is to detect AC but not DC then use capacitive coupling
from the transimpedance amp or FET, which ever you intend to use.  The AC
will pass through the capacitor (not literally of course) but the DC level
will not. You can also put a band pass filter in so that you select the
spectrum you choose.


{Original Message removed}

2007\07\05@083259 by Jinx

face picon face

> Any ideas?

Run away ?

I've tried to do something similar for a project and gave up. Went
with a non-light mechanical option, but I could do that

The problem, as you probably gather, is that the sensor needs to
be on all the time. And not only that, be discriminating. The only
thing I could suggest would be a BPW41 or some photo-diode
as the front end followed by a low power HP filter. Leaving the
PIC to react to the output of the filter and possibly examine the
input when it wakes to see if IR is there

You might be able to wake the PIC periodically to power the
sensor but you'll have to do the maths to see if that will save
power overall and whether that is actually going to see the IR

I've done a low power (10uA) PIR sensor, but the beauty of
the PIR sensors is that they are active only in the very low IR
spectrum, pretty much just heat, and do the filtering for you

2007\07\05@084920 by Russell McMahon

face
flavicon
face
>I need to build a circuit which will detect the presence of
>"modulated"
> IR... aka the type that comes out of almost any remote control.  The
> output will wake a PIC10F to blink a led in a predetermined pattern.

> The catch?  This needs to be battery powered, and small, and be able
> to
> idle waiting for an IR signal for months at a time without battery
> changes. I've been trying to figure out an option for this, but all
> of
> the modules I see takes around 1-2ma, which doesn't equate to
> "months at
> a time" on either 9V or 4AA's.

Last things first

> the modules I see takes around 1-2ma, which doesn't equate to
> "months at
> a time" on either 9V or 4AA's.

1 year ~= 8765 hours.
Modern alkaline AA's are good for 2000 mAH + at 1 mA or so.
So at 1 mA you get 2000+ hours ~= 3 months, so that's in the order of
right.

Next:
There are many IR detector circuits on the web and some could
certainly be persuaded to operate at < 1 mA. An alternative is to
strobe a detector on with a 10%  to 20% duty cycle. Whether this is
practical depends on the length of the IR bursts and how well and how
rapidly the detector wakes up.

The last circuit on this page would be a good starter circuit. Op amp
and component values need to be chosen appropriately.

       http://jap.hu/electronic/infrared.html

In this circuit the critical part is the reverse diode detector diode.
As it is reverse biased it draws extremely low currents. The AC signal
from this is then amplified and the amplifier can be as low power as
good design can make it. Using a discrete (transistor) AC amplifier or
a micropower opamp should allow all up currents of maybe 0.1 mA giving
several years operation on AA batteries.

Receiver here is also a candidate
Because the detector is a forward biased phototransistor the current
is liable to be higher.

       http://www.aaroncake.net/circuits/irremote.asp

Here's a patent that may (or may not) help

       http://www.freepatentsonline.com/5654813.html


This circuit claims 2 uA standby while waiting for IR :-)

       www.planetanalog.com/showArticle.jhtml?articleID=193200324
      http://i.cmpnet.com/planetanalog/2006/10/C0129-Figure1.gif


       Russell

2007\07\05@091538 by Mike Harrison

flavicon
face
On Fri, 06 Jul 2007 00:32:30 +1200, you wrote:

>
>> Any ideas?
>
>Run away ?
>
>I've tried to do something similar for a project and gave up. Went
>with a non-light mechanical option, but I could do that
>
>The problem, as you probably gather, is that the sensor needs to
>be on all the time. And not only that, be discriminating.

There is a lot of scope to be clever in reducing power, but it does depend entirely on the
characteristics of the signal - i.e. how long is it going to be there for, and what is the
worst-case response time.

If the signal is long enough you can save a lot of power by only looking for it periodically, but
issues like startup settling time of the detector need to be kept well under control.
Another approach is to split the discrimination task - wake up when you see something 'plausible'
then stay awake a little longer while you validate it.  

I recently used a vishay IR remote sensor in an app that had to run on about 10uA - fortunately I
could arrange that the transmitted signal lasted for about half a second, and this allowed a
sufficienlty low duty cycle on the receiver to get the current low enough.


2007\07\07@182501 by Debbie

flavicon
face

--- Jinx <spam_OUTjoecolquittTakeThisOuTspamclear.net.nz> wrote:


> You might be able to wake the PIC periodically to power the
> sensor but you'll have to do the maths to see if that will save
> power overall and whether that is actually going to see the IR
>
> I've done a low power (10uA) PIR sensor, but the beauty of
> the PIR sensors is that they are active only in the very low IR
> spectrum, pretty much just heat, and do the filtering for you

That's an idea. Why not use one of those ultra-low Iq IR sensors we talked
about a while back, Jinx? Matsushita --> Napion sensor? Standby drain is
~5-10uA? You'd give the sensor 2 bursts from your Tx: the first one to wake up
the u-controller, wait a moment for the PIC to configure the system, then give
it a 2nd burst with the data. If you had an Rx/Tx on each side, you could
probly get it to handshake. Just my 20c worth.
Debbie


     ____________________________________________________________________________________ Yahoo!7 Mail has just got even bigger and better with unlimited storage on all webmail accounts.
http://au.docs.yahoo.com/mail/unlimitedstorage.html



2007\07\08@215402 by Robert Rolf

picon face

Debbie wrote:
> --- Jinx <.....joecolquittKILLspamspam@spam@clear.net.nz> wrote:
>
>>You might be able to wake the PIC periodically to power the
>>sensor but you'll have to do the maths to see if that will save
>>power overall and whether that is actually going to see the IR
>>
>>I've done a low power (10uA) PIR sensor, but the beauty of
>>the PIR sensors is that they are active only in the very low IR
>>spectrum, pretty much just heat, and do the filtering for you
>
>
> That's an idea. Why not use one of those ultra-low Iq IR sensors we talked
> about a while back, Jinx? Matsushita --> Napion sensor? Standby drain is
> ~5-10uA? You'd give the sensor 2 bursts from your Tx: the first one to wake up
> the u-controller, wait a moment for the PIC to configure the system, then give
> it a 2nd burst with the data. If you had an Rx/Tx on each side, you could
> probly get it to handshake. Just my 20c worth.
> Debbie

Or like the Sony protocol, have a very long initial 'bit' for "AGC" as they
called it. Essentially a long space (IR carrier), then modulation after the IR
receiver stabilizes and the PIC wakes up. Or do you have to conserve power on
the emitter side as well?

R

More... (looser matching)
- Last day of these posts
- In 2007 , 2008 only
- Today
- New search...