I have this soundbar in front of my TV, and I need to stretch my arm to operate it with the remote, so I decided to make a IR repeater as a starting analog-only (no programmable MCU) electronics project.

Schematic diagram exported from Falstad

Link to Falstad circuit

The input is a TL1838 IR receiver 3-pin package with active low.

If I put a white LED in, it works, the LED flashes; but if I swap the LED to an IR LED, it doesn't work. If I use my camera, I can see the remote, but not the IR LED on the board.

Any help, and comments on my first circuit appreciated.


1 Answer 1


It does not work because it is the wrong component for the circuit, or wrong circuit for the component.

The TL1838 is a IR receiver module that demodulates the 38 kHz carrier away and leaves you the signal without 38 kHz carrier.

So either re-encode the 38 kHz carrier before sending it to the IR LED, or get a module that does not demodulate the signal.

  • \$\begingroup\$ I didn't say the TV didn't turn on, I said the LED didn't flash, but thanks for skipping ahead, and I will let you know if the TV doesn't turn on... Meanwhile, however, any idea why the LED isn't flashing? The white LED does flash... What's different between the IR LED and the white LED? \$\endgroup\$ Jun 29, 2020 at 18:18
  • 1
    \$\begingroup\$ You have no current limiting resistor, is the IR LED even working anymore? It might already be broken. Also, is the IR LED connected the correct way around? Even if it did flash in the cell phone camera, it will lack modulation so the IR receiver module in the TV won't see the signal as it requires modulated signal, like the TL1838 does. Assume the TV has similar IR receiver. \$\endgroup\$
    – Justme
    Jun 29, 2020 at 18:33
  • \$\begingroup\$ Bad circuit. This is not a repeater, it's a demodulator. It'll show you the raw data, but it won't be able to transmit to the TV. \$\endgroup\$
    – Kyle B
    Jun 29, 2020 at 21:07
  • \$\begingroup\$ Justin: Why would I need a current limiting resistor? Transistors are current control devices, my current is limited by the transistors... Yes both LEDs are fine, and I can operate the IR LED on its own like a normal LED. \$\endgroup\$ Jun 29, 2020 at 21:10
  • \$\begingroup\$ Kyle B: It's an LED flasher. I want to know why the IR LED isn't flashing while the white one flashes. \$\endgroup\$ Jun 29, 2020 at 21:11

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