IR remote components

This is just a simple IR remote control unit. The PIC16F616 generates a 38MHz signal, the BAUD is 2400, and the IR LED is a model#TSAL5300 powered by a CR2025 3v lithium battery.

As you can see the two transistors (2N2222) create a AND gate which modulates the UART signal.

Considering this is a battery powered application, the goal is battery life. Is the choice of using two transistors a good one? Should I go with an actual AND gate such as https://www.electro-tech-online.com/custompdfs/2010/03/NL27WZ08-DPDF.pdf

Thanks.

No need for spurous AND gates, particularly as you're losing most of your already low supply voltage through them, you also don't have a current limiting resistor for the LED.

It's also a VERY, VERY poor idea to use a UART - it's not a suitable device for IR (or radio) - which is why no remote controls do it that way. It's absolutely trivial to create the 38KHz carrier, and the require modualtion, purely in software - there's no advantage in trying to use any specific hardware in the PIC, and plenty of disadvantages.

Check my PIC IR tutorial which explains how to do it simply any easily, using the Sony SIRC system.

Hi Nigel.

Yep, I am concerned about loosing precious voltage with both transistors.

I found the tutorial, and I liked how you modulated the pulse via software. I will attempt to implement a modulated software UART pulse stream, however, I don't have a scope of any sort so timing might give me some problem. Please state why UART is a poor choice. The reason why I am using UART @ 2400bps is that the PIC receiver is interrupted when they receive a packet and process the payload then compare the checksum before setting a new data flag. They are eight byte packets.

When if comes to the lack of the limit resistor I do have one on my test board. The LED's data sheet indicates it can handle 3v up to 1A at pulse of 100us. datasheet Now, the pulse width might be more than 100us, I just have not done the math yet.

Right now with my setup I am seeing ~36feet with a current limiting resistor and only an increase to ~40feet without it.

What kind of range should I be seeing, I would test another device myself, I don't have anything with a IR remote in the house, not even a TV. LOL

Propaganda said:

Hi Nigel.

Yep, I am concerned about loosing precious voltage with both transistors.

I found the tutorial, and I liked how you modulated the pulse via software.

Click to expand...

It's the normal way of doing it, I stole it from somewhere else

I will attempt to implement a modulated software UART pulse stream, however, I don't have a scope of any sort so timing might give me some problem. Please state why UART is a poor choice. The reason why I am using UART @ 2400bps is that the PIC receiver is interrupted when they receive a packet and process the payload then compare the checksum before setting a new data flag. They are eight byte packets.

Click to expand...

A number of reason, firstly UART's rely on accurate timing, IR (and wireless) doesn't maintain accurate timng, if you use a double beam scope (one beam on transmitter and one on receiver, you will see that the waveforms differ considerably, and differ according to distance.
Secondly you need a preamble to allow the link to stabilise, as I said various metods are used, none of them use anything like a UART though - the most popular is the Manchester coding based Philips RC5, I choose the Sony SIRC's because it's relatively easy to receiver, RC5 is FAR more difficult.

When if comes to the lack of the limit resistor I do have one on my test board. The LED's data sheet indicates it can handle 3v up to 1A at pulse of 100us. datasheet Now, the pulse width might be more than 100us, I just have not done the math yet.

Right now with my setup I am seeing ~36feet with a current limiting resistor and only an increase to ~40feet without it.

What kind of range should I be seeing, I would test another device myself, I don't have anything with a IR remote in the house, not even a TV. LOL

Click to expand...

Range of IR remote controls is usually said to be 10m or so, I've tested mine to 13m, which is the longest room at work