how to create a 38KHz signal pulsed at 10Hz. ?

Projects Programming
1

I want to create a square wave of 38 KHz pulsed at 10hz to be fed to an IR led so a receiver can read it's value and figure it out the distance from 0 to 255.

I tried making a pin high and low for 13 microseconds but it doesn't seem to work.

Is there a way by using a timer or something else to achieve this purpose ?

Thanks

2

The easiest way might be to feed 38khz into the anode of a diode (1N914), cathode to a series 220R resistor to the base/gate of a NPN/NchannelMOSFET transistor, emitter/source to GND.

The feed 10hz to the anode of a 2nd diode, the cathodes of both diodes are connected.

Anode of IR diode to +5v cathode to a 50 Ω resistor then to the collector/drain of the transistor.

If using MOSFET, cathodes of the two drive diodes to a 10k resistor to GND.

3

Does your project require the 38 kHz signal to be phase coherent with the on-off signal? In other words, can the 38 kHz signal be chopped short or long?

Paul

4

the 38kHz signal needs to be synced with the 10hz

here is an image of what i'm trying to do

5

“ the 38kHz signal needs to be synced with the 10hz”

Why?

If this is for detection, you just need on/off at 10hz controlling 38khz.

6

I think 38khz might be the typical IR remote control frequency, so you might look for some remote control modules to make the project easier.

7

You can't get exactly 38 kHz with a 16 MHz Arduino timer since 16000000 / 38000 = 210.5263 clock ticks per half cycle. Would 37914.7 Hz be close enough?

8

37914.7 Hz would be fine i guess

9

You may be missing understanding the keying of the 38khz signal.

For 38khz, use the tone function:

const byte thirty8khzPin = 8;
const byte tenHertzPin = 9;
. . .
tone(thirty8khzPin, 38000);

For the 10hz, a simple timer using millis() BWD will work, toggle the tenHertzPin.

Note: to stop the keying, stop toggling the tenHertzPin, then digitalWrite(tenHertzPin, HIGH);