Validating Infrared Beacon Frequency with an Oscilloscope

  • Thread starter Thread starter Rob K
  • Start date Start date
  • Tags Tags
    Infrared
Click For Summary

Discussion Overview

The discussion revolves around testing the frequency output of an InfraRed beacon circuit built using a 555 timer. Participants explore methods to validate that the circuit is pulsing at the required frequency of 38kHz, addressing both oscilloscope setup and circuit configuration issues.

Discussion Character

  • Technical explanation
  • Experimental/applied
  • Debate/contested

Main Points Raised

  • Rob describes his attempt to test the frequency of his InfraRed beacon using an oscilloscope but encounters difficulties in obtaining a frequency reading.
  • One participant suggests connecting the oscilloscope to both sides of the LED to measure the signal more effectively.
  • Rob reports that even after trying this, he only sees voltage readings without frequency information.
  • Another participant infers that if the oscilloscope trace is DC, it indicates that the 555 timer may not be oscillating.
  • A suggestion is made to adjust the oscilloscope scale to observe multiple pulses, which could help measure the time between them to confirm oscillation.
  • Rob acknowledges a misconfiguration in his circuit setup that was preventing oscillation and notes he is now able to achieve oscillation but needs to adjust the frequency from 173 kHz to 38 kHz.
  • Another participant recommends measuring the IR signal at a distance with an IR receiver to validate that the pulses are being transmitted effectively.

Areas of Agreement / Disagreement

Participants express differing views on the best methods for validating the frequency output and the effectiveness of the current circuit setup. There is no consensus on a single approach, and the discussion includes troubleshooting and suggestions for further testing.

Contextual Notes

Rob's circuit configuration and oscilloscope settings are noted as potential sources of error, but specific assumptions about the circuit's behavior and the oscilloscope's functionality remain unresolved.

Rob K
Messages
33
Reaction score
0
Hi there,

I have built an InfraRed beacon using a 555 timer using a 10K pot to tune the circuit.

How can I test that it is pulsing at the required 38kHz frequency that I need. I have tried using an oscilloscope, by connecting up the Earth and probing one of the legs of the IR LED, but I am not having any success.

Any help in this matter would be greatly appreciated.

Kind Regards

Rob
 
Engineering news on Phys.org
Connect the oscilloscope to both sides of the LED?
 
Tried that, I only get the voltage, no frequency
 
? You mean the scope trace is DC?
That means the 555 is not oscillating, I think.
 
If you adjust the scale to see more than one pulse, you can measure the time between pulses. If you don't have any pulses, the setup (or the oscilloscope settings) is wrong.
 
Thank you Sorphiecentaur, I checked it and that is indeed the case. I was using the standard circuit as shown on the datasheet for a 555, and where there is the voltage divider, I have a 22 Kohm resistor and a 10 Kohm pot and a What I didn't know was that in this circuit, to the pot there should be power and pin 6, this I had, but the floating end I had put to ground. Now it is also pointing to the wiper (pin 6), the little blighter is oscillating. now I have to get it from173 kHz to 38 kHz.
 
Rob K, If you measure the signal at the IRLED you only can know if that it is present at that point. May I suggest that you go one step further, and determine if the IR pulses are really being transmitted? This would mean an IR receiver at some distance from the transmitter. Now, this may seem obvious, but it is true: If you measure the received pulses you validate that your system is really functioning.
 

Similar threads

Replies
10
Views
2K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
Replies
16
Views
3K
  • · Replies 7 ·
Replies
7
Views
3K
Replies
24
Views
6K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 49 ·
2
Replies
49
Views
5K
  • · Replies 2 ·
Replies
2
Views
5K