Wawa:
A 7-degree IR LED theoretically throws about 18x more light on the sensor than a 30-degree LED.
Disadvantage is that you have to line up the LED a bit more accurate.
Did you experiment with the transmit frequency.
38kHz might not be 38kHz on an ATtiny.
I use the transmit code below on an Uno/Nano.
Leo..
const byte IR_LEDpin = 11; // IR transmitter LED with 100ohm (minimum) CL resistor
void setup() {
pinMode (IR_LEDpin, OUTPUT);
TCCR2A = _BV (COM2A0) | _BV(WGM21);
TCCR2B = _BV (CS20);
OCR2A = 209; // ~209 = ~38kHz | ~219 = ~36kHz
}
void loop() {
}
I'm not sure about frequency, I'm just a 'basic developer' when we talk about arduino. Anyway, this is the code that I'm using (it's from easyracelaptimer project). I'm not sure if is right or not, but it works inside house and not at sun.
About IR Led, do you have any sugestions that I can buy from AliExpress or Ebay? I found one (that I don't know if works): TSTS7100. But I can't find in Ali and the only sellers that I found in Ebay doesn't send to Brazil 
Here I don't even need to say......we can't find anything! 
Tks for your tips/help Wawa.
/**
EasyRaceLapTimer - Copyright 2015-2016 by airbirds.de, a project of polyvision UG (haftungsbeschränkt)
Author: Alexander B. Bierbrauer
This file is part of EasyRaceLapTimer.
Vresion: 0.3.1
EasyRaceLapTimer is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
EasyRaceLapTimer is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with Foobar. If not, see http://www.gnu.org/licenses/.
**/
// use 8MHZ internal clock of the Attiny
// Timer code from http://forum.arduino.cc/index.php?topic=139729.0
#include <EEPROM.h>
#define BIT_SET(a,b) ((a) |= (1<<(b)))
#define BIT_CLEAR(a,b) ((a) &= ~(1<<(b)))
#define BIT_FLIP(a,b) ((a) ^= (1<<(b)))
#define BIT_CHECK(a,b) ((a) & (1<<(b)))
// CHANGE HERE THE ID OF TRANSPONDER
// possible values are 1 to 63
#define TRANSPONDER_ID 1
// DEFINITIONS FOR TRANSPONDERS WITH PUSH BUTTON CONFIGURATION
#define CLEAR_EEPROM
#define ENABLE_BUTTON_CONFIGURATION
#define BUTTON_PIN PB2
#define STATUS_LED_PIN PB0
#define BUTTON_INC_ID_PUSH_TIME 750
#define LED_BLINK_CONFIRM_TIME 750
#define ENABLE_PROGRAMMING_MODE_TIME 8000 // 8 seconds
// DO NOT CHANGE ANYTHING BELOW
#define NUM_BITS 9
#define ZERO 300
#define ONE 700
#define STARTB 150
unsigned int buffer[NUM_BITS];
unsigned int num_one_pulses = 0;
unsigned int transponder_id = TRANSPONDER_ID;
unsigned long buttonPushTime = 0;
int buttonState = 0;
unsigned long ledBlinkStartTime = 0;
void EEPROMWriteInt(int p_address, int p_value);
unsigned int EEPROMReadInt(int p_address);
void encodeIdToBuffer() {
num_one_pulses = 0;
buffer[0] = STARTB;
buffer[1] = STARTB;
buffer[2] = get_pulse_width_for_buffer(5);
buffer[3] = get_pulse_width_for_buffer(4);
buffer[4] = get_pulse_width_for_buffer(3);
buffer[5] = get_pulse_width_for_buffer(2);
buffer[6] = get_pulse_width_for_buffer(1);
buffer[7] = get_pulse_width_for_buffer(0);
buffer[8] = control_bit();
}
void readConfigButtonState() {
if (ledBlinkStartTime != 0) {
return;
}
int state = digitalRead(BUTTON_PIN);
if (state == LOW) {
if (state != buttonState) {
buttonState = state;
buttonPushTime = millis();
}
} else {
buttonPushTime = millis();
}
buttonState = state;
if (buttonPushTime + BUTTON_INC_ID_PUSH_TIME <= millis()) {
transponder_id++;
if (transponder_id >= 63) {
transponder_id = TRANSPONDER_ID;
}
EEPROMWriteInt(0, transponder_id);
ir_pulse_off();
cli();
buttonState = HIGH; // RESET
buttonPushTime = millis(); // RESET
ledBlinkStartTime = millis(); // Enable confirmation LED
digitalWrite(STATUS_LED_PIN, HIGH);
encodeIdToBuffer();
sei();
delay(200);
flashTransponderId();
}
}
void updateConfirmationLed() {
if (ledBlinkStartTime != 0 && ledBlinkStartTime + LED_BLINK_CONFIRM_TIME <= millis()) {
digitalWrite(STATUS_LED_PIN, LOW);
ledBlinkStartTime = 0;
}
}
unsigned int get_pulse_width_for_buffer(int bit) {
if (BIT_CHECK(transponder_id, bit)) {
num_one_pulses++;
return ONE;
}
return ZERO;
}
unsigned int control_bit() {
if (num_one_pulses % 2 >= 1) {
return ONE;
} else {
return ZERO;
}
}
void setup()
{
PORTB = 0;
#ifdef CLEAR_EEPROM
for (int i = 0 ; i < EEPROM.length() ; i++) {
EEPROM.write(i, 0);
}
#endif
#ifdef ENABLE_BUTTON_CONFIGURATION
transponder_id = EEPROMReadInt(0);
if (transponder_id == 0) {
transponder_id = 1;
EEPROMWriteInt(0, transponder_id);
}
// put your setup code here, to run once:
pinMode(STATUS_LED_PIN, OUTPUT);
// initialize the pushbutton pin as an input:
pinMode(BUTTON_PIN, INPUT_PULLUP);
PORTB |= (1 << BUTTON_PIN); // enable pull-up resistor
flashTransponderId();
#endif
pinMode(PB1, OUTPUT);
//DDRB = 0b00000010; // set PB1 (= OCR1A) to be an output
setFrequency(38000); // 38 kHz
encodeIdToBuffer();
}
// Set the frequency that we will get on pin OCR1A but don't turn it on
void setFrequency(uint16_t freq)
{
uint32_t requiredDivisor = (F_CPU / 2) / (uint32_t)freq;
uint16_t prescalerVal = 1;
uint8_t prescalerBits = 1;
while ((requiredDivisor + prescalerVal / 2) / prescalerVal > 256)
{
++prescalerBits;
prescalerVal <<= 1;
}
uint8_t top = ((requiredDivisor + (prescalerVal / 2)) / prescalerVal) - 1;
TCCR1 = (1 << CTC1) | prescalerBits;
GTCCR = 0;
OCR1C = top;
}
// Turn the frequency on
void ir_pulse_on()
{
TCNT1 = 0;
TCCR1 |= (1 << COM1A0);
}
// Turn the frequency off and turn off the IR LED.
// We let the counter continue running, we just turn off the OCR1A pin.
void ir_pulse_off()
{
TCCR1 &= ~(1 << COM1A0);
}
void loop() {
for (int i = 0; i < 3; i++) {
for (int b = 0; b < NUM_BITS; b++) {
switch (b) {
case 0:
ir_pulse_on();
delayMicroseconds(buffer[b]);
break;
case 1:
ir_pulse_off();
delayMicroseconds(buffer[b]);
break;
case 2:
ir_pulse_on();
delayMicroseconds(buffer[b]);
break;
case 3:
ir_pulse_off();
delayMicroseconds(buffer[b]);
break;
case 4:
ir_pulse_on();
delayMicroseconds(buffer[b]);
break;
case 5:
ir_pulse_off();
delayMicroseconds(buffer[b]);
break;
case 6:
ir_pulse_on();
delayMicroseconds(buffer[b]);
break;
case 7:
ir_pulse_off();
delayMicroseconds(buffer[b]);
break;
case 8:
ir_pulse_on();
delayMicroseconds(buffer[b]);
break;
}
ir_pulse_off();
} // going through the buffer
delay(20 + random(0, 5));
} // 3 times
// Temporary
//flashTransponderId();
#ifdef ENABLE_BUTTON_CONFIGURATION
readConfigButtonState();
updateConfirmationLed();
#endif
} // end of main loop
void flashTransponderId() {
int fn = abs(transponder_id); //better way to find first digit of trasnponder_id
while (fn >= 10)
fn /= 10;
//Display Transponder ID in two sets of LED Flashes
for (int i = 0; i < fn; i++) { //Display MSB
digitalWrite(STATUS_LED_PIN, HIGH);
delay(400);
digitalWrite(STATUS_LED_PIN, LOW);
delay(400);
}
if (transponder_id > 9) {
//Display a single LED Flash to seperate the bits (helps distinguish ID 1 and ID 10)
delay(1000);
//digitalWrite(STATUS_LED_PIN, HIGH);
//delay(50);
//digitalWrite(STATUS_LED_PIN, LOW);
delay(1000);
for (int i = 0; i < transponder_id % 10; i++) { //Display LSB
digitalWrite(STATUS_LED_PIN, HIGH);
delay(400);
digitalWrite(STATUS_LED_PIN, LOW);
delay(400);
}
}
}