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'[EE]: Infrared Communications -- (variable freq 55'
2002\09\12@154839 by Robert E. Griffith

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>> 3) 555 timer.  Not sure how I would control the frequency, though.
>http://www.reconnsworld.com/ir_ultrasonic_555timer40khzir.html

Thanks, but I should have been more clear.  I know how to make a 555 osc,
but I don't know how to control the frequency of the osc from the uP.  I
want to be able to select 32,38,or 40 khz.

--BobG
{Original Message removed}

2002\09\12@155844 by Smith,Steven W

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Maybe you could use a digital potentiometer controlled by the PIC to set
the frequency of the 555.  Digikey has about 500 different flavors.
Steve Smith
Electrical Engineer
University of Akron
Departmen of Chemistry


{Original Message removed}

2002\09\12@171021 by Robert E. Griffith

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Oh, of course.  Thanks.  I was thinking of all sorts of round-a-bout ways of
doing it.

--BobG

-----Original Message-----
From: pic microcontroller discussion list [spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU]On
Behalf Of Smith,Steven W
Sent: Thursday, September 12, 2002 3:58 PM
To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
Subject: Re: [EE]: Infrared Communications -- (variable freq 555 osc)

Maybe you could use a digital potentiometer controlled by the PIC to set
the frequency of the 555.  Digikey has about 500 different flavors.

Steve Smith
Electrical Engineer
University of Akron
Departmen of Chemistry


-----Original Message-----
From: Robert E. Griffith [bobspamKILLspamJUNGA.COM]
Sent: Thursday, September 12, 2002 3:47 PM
To: .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
Subject: Re: [EE]: Infrared Communications -- (variable freq 555 osc)

>> 3) 555 timer.  Not sure how I would control the frequency, though.
>http://www.reconnsworld.com/ir_ultrasonic_555timer40khzir.html

Thanks, but I should have been more clear.  I know how to make a 555
osc,
but I don't know how to control the frequency of the osc from the uP.  I
want to be able to select 32,38,or 40 khz.

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2002\09\16@095153 by Roman Black

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Smith,Steven W wrote:
>
> Maybe you could use a digital potentiometer controlled by the PIC to set
> the frequency of the 555.  Digikey has about 500 different flavors.


The 555 uses resistors to +ve to give the charge
time, with one resistor to its open collector pin
to give discharge time. To control its freq with a
PIC (in one or two freq steps) only requires a resistor
and diode to the PIC pin which will change the charge
time and hence freq. :o)
-Roman

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2002\09\16@095708 by Scott M. Thomas

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Would you need a diode if you made the PIC pin an input when not in use?

Thanks

Scott


-----Original Message-----
From: Roman Black [@spam@fastvidKILLspamspamEZY.NET.AU]
Sent: Monday, September 16, 2002 9:45 AM
To: KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU
Subject: Re: [EE]: Infrared Communications -- (variable freq 555 osc)


Smith,Steven W wrote:
>
> Maybe you could use a digital potentiometer controlled by the PIC to set
> the frequency of the 555.  Digikey has about 500 different flavors.


The 555 uses resistors to +ve to give the charge
time, with one resistor to its open collector pin
to give discharge time. To control its freq with a
PIC (in one or two freq steps) only requires a resistor
and diode to the PIC pin which will change the charge
time and hence freq. :o)
-Roman

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2002\09\16@103212 by Roman Black

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Correct! :o)

The voltage at the "discharge" pin of the 555
will rise as a ramp (as the cap charges) which is
not really a good idea for a PIC input.

And diodes like 1N4148 cost only 1 cent!
-Roman


Scott M. Thomas wrote:
{Quote hidden}

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2002\09\16@104827 by Scott Thomas

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Agreed.

But what harm does a ramp do to a PIC input? Excess power dissepation?

Scott



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

From: Roman Black [RemoveMEfastvidTakeThisOuTspamEZY.NET.AU]

Sent: Monday, September 16, 2002 10:28 AM

To: spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU

Subject: Re: [EE]: Infrared Communications -- (variable freq 555 osc)



Correct! :o)

The voltage at the "discharge" pin of the 555

will rise as a ramp (as the cap charges) which is

not really a good idea for a PIC input.

And diodes like 1N4148 cost only 1 cent!

-Roman

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2002\09\16@110754 by Jim

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"what harm does a ramp do to a PIC input? Excess power
 dissepation?"

This would be a nice, quick test to perform:

1. monitor Vcc (Vdd?) supply to PIC with
  a) millimammeter (perhaps no more than a 1 Ohm R and a DVM) and
  b) a scope
2. using a function gen apply either a saw-tooth or sine
  wave to an unused PIC-input pin
3. Observe test instruments for any observable indications.

RF Jim



----- Original Message -----
From: "Scott Thomas" <TakeThisOuTscottEraseMEspamspam_OUTDBT.NET>
To: <RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU>
Sent: Monday, September 16, 2002 9:47 AM
Subject: Re: [EE]: Infrared Communications -- (variable freq 555 osc)


Agreed.

But what harm does a ramp do to a PIC input? Excess power dissepation?

Scott



{Original Message removed}

2002\09\16@111145 by JISAK

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Please what is the marterial ( film or card ) we can see Infrared ?

Thanks all

JK

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2002\09\16@112308 by Robert E. Griffith

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Thanks.  If I end up using the 555 I will try this.  If I understand
correctly, you add a second resistor (and diode in series) in parallel with
the one connected between the 555's discharge pin and the +Vcc, but instead
of connecting it to +Vcc you connect it to a PIC output.  When the output is
high, it's like the resistor is connected to the first one in parallel thus
reducing the net resistance.  When output is low, the diode prevents current
flowing the other way, so its like the resistor is no longer there and the
net resistance is only that of the fist, fixed, resistor.

So, if I want 4 frequencies, I could use two PIC outputs and choose the
three resistors (fixed, output1, and output2) so that there various parallel
combinations result in the effective resistances required for the desired
frequencies.

--BobG

{Original Message removed}

2002\09\16@113320 by Alan B. Pearce

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>Please what is the marterial ( film or card ) we can see Infrared ?

I take it you want to see infra-red light, or its presence?

The best possibility is something like a webcam or "eyeball" type security
camera with the IR filter removed from over the CCD (if it has one)

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2002\09\16@113744 by Jochen Feldhaar

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Hi,

I just took my cards out of the case and I will try to describe them.
Manufacturer is (was) Dr. Manfred Bromba in Munich, Germany.

Type 1: Strontium sulphide, doped with Europium and Samarium. Must be
"charged" with daylight previously to use. Manufacturer of film: Quantex
Also: Zinc sulphide, doped with Copper and Lead.

Type 2: Continuously converting. Needs more IR power.
Yttrium-Ytterbium-Erbium compound.


CONRAD in Germany sells (sold) them, not cheap but very useful for me.

Greets Jochen
JISAKEraseMEspam.....NETCOURRIER.COM schrieb:
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2002\09\16@114148 by Bond, Peter

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> >Please what is the marterial ( film or card ) we can see Infrared ?
>
> I take it you want to see infra-red light, or its presence?
>
> The best possibility is something like a webcam or "eyeball"
> type security
> camera with the IR filter removed from over the CCD (if it has one)

Or not removed, as the case may be.  My digital camera sees IR LEDs quite
clearly out of the box; very insensitive to white LEDs, however.

http://www.conrad.com do an IR detector card - you shine the remote at the
sensitive patch on the card, and it emits a small faint flash in response.
Can't find the stock number at the moment, sorry.

Peter

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2002\09\17@053314 by JISAK

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It's exactly what i need.

Conrad france don't sale it.

Do you have ref. to order in germany.

Thank you

Jean Karl Vinay

Jochen Feldhaar a icrit :

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2002\09\17@063816 by Jochen Feldhaar

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Hello Jean Karl,

in my Conrad (Business 2002) it is the ordering numbers 184896-94,
184926-94, and 184977-94, prices between 7 and 10 EUR. Try http://www.conrad.de
looking for "infrarot-indikatoren".

Greets Jochen

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