IR Interface for an Ethernet SBC

In a previous blog, we looked at a range of ethernet based SBCs. We have also been looking at various IR Remote Control signals. The next step is to bring the two together - to build a circuit to send and receive IR signals using an ethernet based SBC. This blog describes a small bit of hardware added to the SBC to do this.

Component choices

The ethernet SBC of choice is the Olimex PIC-WEB.

The IR LED is a Vishay TSUS4300. It is an IR LED in a 3mm LED package.

The IR Receiver is a Vishay TSOP4P38. It filters out the carrier signal and provides a clean signal. It may not have been the best choice as it is more of a proximity sensor. I may replace this in future with a Vishay TSOP38338 which is more suited to this application.

Circuit Design

The add-on circuit is shown below.

The IR receiver TSOP4P38 outputs the signal to the PIC RC2 input directly. The IR emitter TSUS4300 is driven by a BC547 transistor in turn driven by PIC RD2 output. The emitter has a Red LED in parallel so that you get an indication when the LED is on. Additional yellow and white LEDs are driven off PIC outputs RB1 and RD1. Currently, the yellow LED is used to indicate that the circuit is in the process of reading an incoming IR signal and the white LED indicates the IR signal received.

Construction

The expansion circuit uses the 34 pin connector on the board. I used a piece of general purpose PCB and mounted a 34 pin connector on it. The part no. is 3M 8534-4500PL and goes for around five bucks - the most expensive part on the PCB.

I had to switch the inputs around after assembling the circuit when I realised I need to take advantage of the CCP. The PCB looked more and more battered with each change.

All LEDs and receivers line up so that they all point in the same direction towards the user. From left to right are: white LED indicating IR signal being received, yellow LED indicating unit is in receive mode, IR receiver, Red LED indicating IR signal being sent, IR Transmitter.

The connector can be easily plugged and unplugged. As I have mentioned before, this allows the SBC to be reused on other projects. It also allows me to unplug the circuit and throw it into my junkbox. At any time, I can retrieve it, plug it in and I have a working circuit. This is much better than using a proto-board section on the SBC. Right now, this is what the complete unit looks like.

If you don't want to pay a $40 courier charge to get stuff shipped from abroad to Australia, the usual choices are element14 (nee Farnell) and RS Components. Most of the parts were sourced from element14. The Olimex SBC was sourced from Dontronics.

Ref	Part No.	Cost AU$	Supplier Part No.
-	Olimex PIC-WEB	46.00	Dontronics
U1	TSOP38338	1.20	element14 1869471
Q1	BC547	0.15	-
D1	3mm Yellow LED	0.30	-
D2	3mm White LED	0.30	-
D3	TSUS4300	0.55	element14 1045518
D4	3mm Red LED	0.30	-
R1	120E	0.10	-
R2	120E	0.10	-
R3	1K	0.10	-
R4	10K	0.10	-
R5	56E	0.10	-
R6	680E	0.10	-
C1	2.2uF/16V Tant.	0.30	-
J1	34 pin PCB Socket	6.00	3M 8534-4500PL element14 9138668
Total		55.70	-