what the hell is going on with my IR LED? - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: March 27, 2021, 06:41:06 am
content: I can't figure out why my IR LED barely and rarely gets pickup up by the IR sensor, meanwhile any TV remote or anything like that works like 20 meters away... I tried changing the LED, I checked with a phone camera and it glows fine.why doesn't it get picked up by the IR sensor then?if you want to know the circuit I'm using it's this:[ Attachment Invalid Or Does Not Exist ]

author: Ian.M
author_rank: Super Contributor
timestamp: March 27, 2021, 06:47:02 am
content: Sensor part number?

author: Jwillis
author_rank: Super Contributor
timestamp: March 27, 2021, 07:06:45 am
content: You may have destroyed it with 8V . Most I've use are 5V max some only 3V

author: Jwillis
author_rank: Super Contributor
timestamp: March 27, 2021, 07:12:42 am
content: Dis you measure the sensor voltage in the remote? I've not seem any TV remote that uses more than 6V on older ones and 3V on new ones.

author: ogden
author_rank: Super Contributor
timestamp: March 27, 2021, 07:20:18 am
content: IR led's in regular TV remotes are driven using high current (100-200mA) pulses. Hint: for IR led you don't look at nominal current specs but it's power rating.

author: gabiz_ro
author_rank: Regular Contributor
timestamp: March 27, 2021, 07:21:21 am
content: Is tot clear but I suppose that IR led is the one through 470R to 8V.Receiver used have some circuit inside.IR signal from remote is pulsing based on some codeYour IR led is only on or off but receiver ignore this.Try to make it blink on some frequency and test.As for frequency look at some IR remote standards to choose that.

author: ogden
author_rank: Super Contributor
timestamp: March 27, 2021, 07:24:41 am
content: Quote from: gabiz_ro on March 27, 2021, 07:21:21 amRight. To use TV remote IR receiver, signal MUST be modulated at specific frequency (36/38/40 KHz). Otherwise it will ignore your signal as it ignores sun rays and orher IR sources.https://www.ti.com/lit/an/slaa644b/slaa644b.pdf

author: rstofer
author_rank: Super Contributor
timestamp: March 27, 2021, 07:26:30 am
content: Every IR sensor I have ever used has expected a 38 kHz carrier that is modulated on and off. They do this to prevent unintended operation.https://youtu.be/O8iYPg5DSXwIR remote control projects are all over Google.

author: Ian.M
author_rank: Super Contributor
timestamp: March 27, 2021, 07:31:52 am
content: Most IR sensors found in consumer AV equipment are *NOT* simple phototransistors. They require a modulated carrier IR signal to give an output, typically a 38KHz squarewave, though other carrier frequency variants are occasionally used. Here's the datasheet forVishay TSOP34138which is a fairly typical example.However its not as simple as providing a 38KHz IR signal and getting a continuous logic 1 output. It also has an anti-interference circuit that reduces the gain if it receives a continuous carrier within its passband. The details of what it *WILL* respond to are in the table on page 5 of the datasheet. Basically a TSOP34138 will 'see' a 38KHz burst of between 6 and 70 cycles with a min. 10 cycle time gap before it will see the next burst.Those parameters vary for different makes and part numbers, so some experimentation may be required to find out what your module responds to.There are two easyish approaches to making an IR burst generator - either program a MCU, and drive the IR LED via a transistor(e.g. this Arduiono example:https://learn.adafruit.com/using-an-infrared-library/sending-ir-codes)or to use two 555 timers, one for the 38KHz carrier, and the other to gate it for the burst length.P.S. *PLEASE* feed your sensor a regulated 5V supply before you blow it! If you don't have an existing 5V rail, a 1K dropper resistor from your 8V rail, with a 4.7V or 5.1V Zener diode as a shunt regulator would be good enough. It also should have decoupling - e.g. a 100nF ceramic capacitor across its supply and ground pins.

author: ogden
author_rank: Super Contributor
timestamp: March 27, 2021, 07:43:26 am
content: At your level of expertise (no offense) it will be incredibly hard to reinvent The Wheel. Better idea would be to copy existing MCU-based IR remote project, search term: Arduino IR remote. Start with receiver.

author: Jwillis
author_rank: Super Contributor
timestamp: March 27, 2021, 08:06:31 am
content: Quote from: ogden on March 27, 2021, 07:20:18 amSorry for the confusion but I trying to say that 8V for the sensor seems to high since most operate at a maximum of 3V to 5V , The IR LED can operate at any voltage as you say as long as the maximum power rating isn't exceeded .

author: Ian.M
author_rank: Super Contributor
timestamp: March 27, 2021, 08:26:05 am
content: If you aren't an enthusiastic Arduino user, use a 555 timer for the oscillator - its the easiest to get working. Here one way of producing the 38KHz carrier:As it doesn't have a burst length control, you'll see a brief (<2ms) 'blip' from the receiver every time you press the button. You could use that to toggle a flip-flop to control your load, or you could add another 555 to break the carrier up into bursts by driving the Reset pin of the 38KHz one driving the LED.LTspicesim attached.Edit: I've also attached the 2x 555 burst modulated version as a LTspice sim. Its well worth installing LTspice and starting to learn to use it. Apart from being a freeware, very powerful SPICE circuit simulator, its also popular here and on other electronics fora for sharing circuit ideas.The burst modulated version should give repeated pulses from most consumer remote IR receivers for as long as you hold its button down, which you could RC low pass filter before driving the base of the NPN driving your MOSFET, for a continuous output.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 28, 2021, 03:07:59 pm
content: Quote from: ELS122 on March 27, 2021, 07:37:18 amOr... you could use a plain 2-wire IR phototransistor in place of the IR receiver ...

author: radiolistener
author_rank: Super Contributor
timestamp: March 29, 2021, 08:33:29 am
content: Quote from: ELS122 on March 27, 2021, 06:41:06 amBecause TV remote using it at AC frequency and listen for a limited frequency bandwidth. When you use it at DC, you're get a lot of noise from environment IR emission and you cannot see the difference between DC on and DC off, because that difference is too small and environment noise is too high.TV remote works the same as radio receiver. You cannot charge battery from another battery located at 20 meters away with no wire connection. But you can listen radio waves with a radio receiver from transmitter located at 20 meter away.