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I often get frustrated by how poor some
infrared remotes in many new electronic devices operate. I used to be able
to turn on the TV from 30 feet away. Now, it seems that I have to get within
15 feet. To address this issue, I designed the circuit shown below.
The circuit taps into the TV remote’s existing infrared LED and drives 8 more
efficient devices. The result is a communications range some 4 to 5 times
longer.
The circuit is
housed in a low profile plastic box. A Serpac H-65AA (Digikey part number
SRH65-11B) has a nice battery compartment for two AA cells. The circuit is
powered by two standard AA cells. I suggest including a 1.5 farad supercapacitor
in parallel with the battery to help supply the peak current needed by the 8 LEDs.
A Nesscap EMHSR-0001C5-005R4 has a very low internal resistance and a higher 5.4v
voltage rating. Other supercapacitors might also work. Just make sure they have
a voltage rating higher than 3v. The recommended infrared LEDs are made by Vishay,
their part number TSAL6100. These are available from Mouser, Mouser part number
782-TSAL6100. These devices emit infrared light in the longer 950nm wavelength,
which most infrared remote receivers expect.
When the VCR
remote’s LED turns on, there is a voltage drop of about 1.5v. This voltage is
sufficient to turn on the PNP transistor Q1. When Q1 is switched on, 3v is
routed to the gate of Q2, which switches it on hard. It routes current to all 8
of the Vishay LEDS. With a 22 ohm resistor wired in series with each LED, the
peak current is set at about 60ma. This is about 4 times higher than most LEDs
are driven in a typical remote. By wiring 8 more LEDs to form a cluster, the
range of the remote should increase by a factor of least 5. So, instead of 15
feet, with the added light, the distance should be closer to 75 feet.
Click on Drawing Below to view PDF version of Schematic
