Hi Lindy,

> No!  No matter where I pointed the thing, the IR detector detected it.
> I even put aluminum foil around the IR detector, and still it wouldn't
> fail It is just a Gr=FCndig TV and remote.
>
> What am I doing or thinking wrong?

> I even put aluminum foil around the IR detector and still it wouldn't f=
ail.

Use something black. Tin foil is like placing tiny mirrors all around you=
r IR
detector. One small opening, crack, etc, and the IR signal will bounce ar=
ound
inside the foil striking the IR detector face. The TSOP brand are real se=
nsitive
and hard to block. Especially in a highly reflective environment.

Be sure to cover the sides, back, bottom, top, etc,, Small amounts of IR =
energy
can pass through the IR detector plastic case, so just blocking the front=
 may not
always do the trick. Black elctrical tape covering all sides with a small=
 hole just
over the IR module dome face works to make it very directional.

I assume you're just using the TV transmitter for testing your initial IR=
 detection
code? You can't really control the TV transmitters output unless you modi=
fy the
transmitter or partially cover/block the output window.

If you're goal is to have the PIC control the IRLED on your bot, you can =
place a
piece of black heat shrink over the IRLED to make the beam more direction=
al.

WIth the PIC driving your IRLED you can control the output power by adjus=
ting the
PWM duty cycle. A PIC with hardware PWM would be handy, but you can creat=
e
simple code to drive the IRLED at the band-pass frequency of your IR dete=
ctor
module something like this;

Variable "Cycles" contains the number 40kHz cycles the routine will gener=
ate.

; Note: Assumes 4MHz osc & you're using RA.7 to drive the IRLED.

Pulse                  ;//                                IRLED      680
   bsf porta, 7       ;// 1uS, LED=3Don  RA.7----|>|---------/\/\/\/\/---=
---- gnd
   goto $+1           ;// 3uS
   goto $+1           ;// 5uS
   goto $+1           ;// 7uS
   goto $+1           ;// 9uS
   goto $+1           ;// 11uS
   goto $+1           ;// 13uS
   bcf porta, 7       ;// 14uS, LED=3Doff
   goto $+1           ;// 16uS
   goto $+1           ;// 18uS
   goto $+1           ;// 20uS
   goto $+1           ;// 22uS
   decfsz Cycles,F   ;// 23uS
   goto _Pulse        ;// 25us =3D 40kHz

The IR detectors output will not return the the idle state for a brief pe=
riod, and the PIC
is plenty fast enough to sample the output before it settles. Just sample=
 the detector
output immediately on exit from the pulse routine.

Another approach could use two variables. One holds the high time, one ho=
lds the low time,
and you have control of the carrier duty cycle.

Here's one project I did using hardware PWM for IR distance measurement w=
ith CDS
light readings to adjust the IRLED output power. It's very simple, but it=
 does work, and
you can't beat the price..;o]

http://www.rentron.com/PicBasic/infrared_object_detection.htm

We have several robot projects online http://www.rentron.com/Micro-Bot/in=
dex.htm with IR
detection, sonar, etc,, you may find helpful. The code is in PicBasic Pro=
, but the theory is
still the same in .asm, C or BASIC.

I've done a few high-speed IR comm links, an IR BASIC Stamp programming s=
ystem, and a
few more gadgets, so if you get stuck on the IR thing let me know. Be gla=
d to offer any help
I can.

> I tried to move from IR to sonar, but I cannot understand how the elect=
ronic portion works
> for the receiver

Take a peek at this: http://www.robot-electronics.co.uk/htm/srf1.shtml Fu=
ll schematics &
source code for the http://www.robot-electronics.co.uk SRF04 sonar range =
finder.

You can buy the SRF04 sonar range finder pre-assembled too. I have code i=
n PicBasic Pro
& CCS C for the SRF04 if you would like copies.

Regards,

-Bruce
tech@rentron.com
http://www.rentron.com

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