# How Much Current is Usually Used with IR Transmitting LEDs, in Remote Controls?

If you take various Remote Controls from your home,
such as for a TV, Audio System, TV Box, etc,
and measure the current that is supplied to the IR LED in the remote,
what would be common current values for it?

I am talking about the current in the peak of the square wave of course,
and not some average value that takes both "0" and "1" parts of the square wave into account.

• What is the size (value? like 10 or 22 ohms) in series with the LED and switching transistor? – analogsystemsrf Apr 13 at 18:34
• Assume that you simply get various remote controls, and you can measure the current. You do not know much about the circuit inside, altho naturally they all must be using a Switching Transistor, and a Series Resistor. The purpose is not to find what Resistor value to use.. I just want to know what are typical currents that are supplied to IR LEDs, in regular home remote controls. – spaceman Apr 13 at 18:37
• Depends if has 1 battery or 2 and 1 emitter or more & 3mm 5mm or SMD – Sunnyskyguy EE75 Apr 13 at 18:45
• The usual remote controls that I have are operated by 2xAA batteries, and have 1 LED (5mm).. – spaceman Apr 13 at 18:46
• Take one apart and find out. It is likely that no one here has designed such a product. – EinarA Apr 13 at 18:50

They typically have something like 10-50 ohms in series with one or two parallel LEDs and a driver transistor or MOSFET.

Assuming a 2.5-3V battery voltage (2 AA or AAA) and a 1.2V LED voltage that's maybe 20 to 200mA.

I had a remote that I extended the range on (for a bedroom remote where the IR light had to bounce to get to the set-top box at the back of the lift), and I did it by replacing the LED with a more efficient type rather than by jacking up the LED current.

• @SpheroPefhany regarding "and I did it by replacing the LED with a more efficient type rather than by jacking up the LED current" - can you please recommend where can I buy a more efficient IR Transmitting LED? Is it possible to buy such also from eBay instead of from Mouser/Digikey and such? (the latter stores are less accessible to hobbyists, due to their high shipping cost of 40\$ per purchase) – spaceman Apr 21 at 12:03
• I found a suitable product (in this case, via a distributor parametric search engine). That results in a manufacturer name and a part number (with a datasheet). Once you have a part number and manufacturer, you can find a supplier who will deal with you on terms you find acceptable. There may be suppliers who will ship via mail, for example if you're not in a hurry. With eBay, Ali, tmall etc. you have the additional wrinkle that the parts have a much higher likelihood of being counterfeit or fallouts. – Spehro Pefhany Apr 21 at 14:51
• @SpheroPefhany I see. OK. Can you please tell what is the mnfrr name and part number that you used, that is high efficiency? (assuming you worked with 940nm, like in home remote controls) – spaceman Apr 21 at 15:28
• @spaceman It was but I think it was earlier than my records 2016 so don't have that info at hand. I did take a look but no go. – Spehro Pefhany Apr 21 at 16:54

Difficult to know the exact values, but typically, at least few years ago when 5mm IR leds were commonly used in remote controllers, they usually were rated for 1A pulses (assuming a certain low duty cycle of course). Most likely they were not driven with such high currents in remotes.

A Narrow beam long range is best for bouncing off walls.

SFH 4550 OSRAM

1100mW/sr @ 100mA
1.5V typ 1.8V max @100mA using peak current.
rated for 1A < 100us Abs. Max
6deg 5mm lens

Consider 2 AAA batteries in series from 3 to 2V range.

100mA CC sink.

or a 1.5V/0.1A = 15 Ohm series resistor for 1.5V typ on LED

If your LED is 1.8V then 1.2V/0.1A= 12 Ohms

Efficiency here is the mW/sr /mA and is best found in narrow lens LEDs to amplify the beam at some lens loss. Because SMD LEDs cannot be molded with a narrow beam lens the same as TH LEDs, the wide beam means the intensity is far less.

A constant current source is best for current regulation using a high hFE output transistor preferably to achieve low Vce(sat) that is also rated for > 100mA.

simulate this circuit – Schematic created using CircuitLab