Trying to convert an IR Torch

This is [hopefully] the datasheet for the controller IC on that board:

If that's correct, the EN pin, Enable / on/off control, is probably the top left one that's presently linked to the lower end of the big "151" resistor.

However, as the whole drive circuit uses a switched-mode system, the LED is already getting high frequency current pulses rather than continuous power - it may not be possible to modulate it at the required speed (around 40KHz) without the the SMPSU frequency interfering with that.

Not only that but the output PSU filter will completely attenuate the IR carrier.

What exactly are you trying to do?, and why?.

Nigel Goodwin said:

What exactly are you trying to do?, and why?.

Click to expand...

Long range IR remote for our winter camp

How much time and money do you want to spend on re-inventing the $50 wheel?


If you already knew the carrier frequency of your remote, you could simplify a design for that channel instead of a universal carrier. Sharp/Vishay devices are low cost and just need a simple linear regulator for detecting your remote. Then IR LED's and constant current modulated with data and carrier clock would be easy to drive with a string of fixed IR narrow beamwidth LED's running in pulsed burst carrier mode to resemble your torch using up to 100 mA current limited pulses with say <=10 deg degree LED's.


Rx https://www.vishay.com/en/ir-receiver-modules/

Suggested LEDs https://www.vishay.com/docs/81009/tsal6100.pdf 10deg 5mm $1 /string

Tx needs a CMOS Astable clock AND / NOR /NAND Data something like a 38 kHz clock carrier then CC current limiter with 2 transistors. I modified mine to reduce the Vbe drop with NFB.

All of this will easily work on a "perf" board. with a good 5V supply. Each of the resistors affects the current limit. There are other methods too.

SIMULATION https://tinyurl.com/yo4wfako



Make sure the Vishay Rx Vcc has low noise across IC with RC filter if necessary.

johnbergman said:

Long range IR remote for our winter camp

Click to expand...

How long, and to do what? - a normal TV remote will easily reach in excess of 10m.

In addition to what Tony mentioned, you have to match both the IR transmitter and receiver’s wavelength.
There are two mainstream IR LED wavelengths, 850 and 940 nm. From what I have seen, most —although not all— IR receivers utilize 940 nm, therefore your best bet is to use this wavelength.

If the transmitter/receiver wavelength are not matched, the device will still work but with reduced sensitivity.