IR transmitter

[shico90]

Hello
again with this topic, excuse me with these questions
now the IR receiver is working and i tested it with the tv remote and it works fine
and i made a transmitter circuit using one led to generate a frequency with 38 KHZ and i can see with my eye that the receiver is getting the signal, because the visible led in the receiver circuit is blinking at that frequency
the problem is the voltage generated at the receiver is very small and it is like 0.1 \v or something that i can see it by voltmeter or with a led and see the very small change in the led brightness that is opposite when i use the tv remote it actually generate 5 V or something and it is very clear
so now i need to improve the transmitter circuit because i want to use the logic one with a micro-controller
if anyone could help
thank you

 

[Boncuk]

Hi shico90,

what kind of LED are you using for transmitter?

What receiver circuit are you using? (e.g. TSOP17xx series?)

Vishay offers UV-LEDs with >100mW/sr.

Boncuk

 

[Gayan Soyza]

You can send a burst pulse followed by a gap time instead of sending a continuous 38Khz frequency.

 

[shico90]

Hi shico90,

what kind of LED are you using for transmitter?

What receiver circuit are you using? (e.g. TSOP17xx series?)

Vishay offers UV-LEDs with >100mW/sr.

Boncuk

actually i don't know what is the receiver or the transmitter type. no names or anything are written on it

 

[shico90]

You can send a burst pulse followed by a gap time instead of sending a continuous 38Khz frequency.

how can i do that?
will the receiver able to detect the infra though?

 

[Boncuk]

You can make a gated oscillator circuit using two NE555 (or one NE556).

Have the first one oscillate at 833.3Hz (timing 600µs) at 50% duty cycle, controlling the second one oscillating at 38KHz.

Use the output of the first one to control the RESET input of the second one.

Something like this:

The duty cycle of the circuit is 51.4%, but it should work with any IR-receiver between 36 and 40KHz.

 

[shico90]

You can make a gated oscillator circuit using two NE555 (or one NE556).

Have the first one oscillate at 833.3Hz (timing 600µs) at 50% duty cycle, controlling the second one oscillating at 38KHz.

Use the output of the first one to control the RESET input of the second one.

Something like this:

The duty cycle of the circuit is 51.4%, but it should work with any IR-receiver between 36 and 40KHz.

thank you very much
does this bursts thing increase ir range?

 

[ronv]

Yes, otherwise the receiver thinks the continuous signal is interference and drops the gain to try to filter it out. Might want to check a data sheet for any receiver. They have a few tricks.

 

[Boncuk]

In addition to ronv's post:

Using e.g. an LD274 it has 50mW/sr, while the TSAL6100 has 130mW/sr (max. 400mW/sr) which should increase range considerably.

Using two TSAL6100 the range should be 10 to 15m.

Boncuk