I am working on reception of IR signal from Air conditioner's remote. To achieve this I have selected IR receiver and sensor respectively - TSOP34438 and TSMP58000. The circuit diagram is shown below and the output of both sensors are fed to ESP-12E module's GPIO pins specifically GPIO14, GPIO12.

schematic diagram

The issue with the circuitry is I am receiving an unstable performance i.e. not receiving stable output throughout a day without a change in circuit elements. I make sure the current supply for respective IR module is with the range specified in their datasheet. (Current supply: for TSOP34438 is 0.33mA and for TSMP58000 is 0.6mA).

The other concern is, without transmitting any IR signal, it is receiving environmental noise as an IR signal.

Can anyone help me resolve this issue?

I would appreciate your help. Thank you.

  • 1
    \$\begingroup\$ Looking at the datasheet of the TSOP34438 I notice that it shows an application diagram where the decoupling capacitor is connected directly across the GND and VS pins of the IR sensor. In your schematic there's a 330 ohm resistor in between. As a test try shorting the 330 ohm resistor or adding a 10 uF capacitor directly across the supply pins. \$\endgroup\$ Sep 25, 2018 at 9:25
  • \$\begingroup\$ Thanks for your suggestion. I tested the performance with Shorting 330ohm, but could not observe any change in the behavior. Receiving continuous junk IR data as earlier. \$\endgroup\$
    – Dimpal S.
    Sep 25, 2018 at 10:54

1 Answer 1

  1. Supply current isn't something you can (or even need) to guarantee. You supply the device with a supply voltage with in the allowed range (up to 6V for the TSOP34438.) It will then draw as much current as it needs to operate. The datasheet says 0.35mA when operating on 3.3V.

  2. You can use a simple filter to improve performance. To stay with the example of the TSOP34438, C1 needs to be connected directly to pin 3 and ground. R1 then goes from 3.3V to pin 3. R1 probably also needs to be much smaller. The datasheet doesn't give an example for the TSOP34438, but the TSMP58000 datasheet says 100 ohms and 4.7uF. Those values ought to work well enough for both sensors.

  3. The TSOP34438 is designed to detect 38kHz pulses - your IR transmitter MUST use that frequency, or else the TSOP34438 won't detect it properly. It has a built in filter, and rejects anything too far away from 38kHz.

  4. The TSMP58000 accepts signals from 20kHz to 60kHz. It isn't as picky about the transmitter, but won't reject environmental IR as well. You would need to find the proper frequency (what your transmitter sends) and build your own filter to go with the TSMP58000.

So, you probably have a few things to look at:

  1. Correct powersupply. Fix (or leave out) the filter on the power supply. Do it right or leave it out.

  2. Correct frequency - make sure your transmitter transmits at 38kHz for the TSOP34438.

  3. Correct filter - build and use an appropriate filter for the TSMP58000. Make to match the transmit frequency of the transmitter.

I would suggest you verify the transmit frequency of the transmitter, then use a variant of the TSOP34438 intended for that frequency. The TSOP34438 datasheet gives part numbers for equivalent devices for different transmit frequencies.

When the transmitter is off, the receivers will pick up some junk. You will have detect proper signals yourself.

  • \$\begingroup\$ Thanks for your suggestions. I appreciate your time. Will work on your suggestions and update you. \$\endgroup\$
    – Dimpal S.
    Sep 25, 2018 at 13:42

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.