I am modifying the sparkfun bigtime watch to include tv b gone functionality. I have the code from Nathan Seidle uploaded to the watch. I cannot figure out how/where to physically attach the IR LED. Can someone provide a visual to me? Do i connect directly to the atmega pins on the pad where the atmega is attached to the pcb? Or do i need to run some wires and a resistor off of the legs of the atmega? I am inexperienced with this and need a specific visual of where to attach.
Only info provided in code is this: “This project allows BigTime to turn off TVs by soldering an IR LED to Arduino pin 3 and GND.”
Also are there updated design files to fit the led in the enclosure?
KIT-11734
Arduino pin 3 would be the same as IC pin 5 and that’s the pin between the “u” and “n” on the sparkfun logo on the board.
That code is a hack so you’d need to hack the case to fit a LED and resistor in. This is a bit of an advanced modification especially if you’re a beginner. If you’re uncomfortable making the modifications you might see if you can find someone a bit more experienced in soldering to help. Also, 200 ohms is the lowest you probably want to go for a resistor, a 220 or 330 ohm should be about right.
I have the right pins. So I need to solder a wire from pin 3 (ic 5) to a resistor then to the led anode? Then attach the cathode via wire to ic pin 8 (gnd).
Is this correct?
Also do you usually solder beneath the board to the leg of the ATmega or on top before it goes through the hole?
Thank you!
Yep, you got it.
Top or bottom doesn’t matter but there’s less risk of overheating the IC pin from the bottom than the top.
So I did exactly that. I used a 270 ohm resistor and soldered everything together. The code is flashing and everything looks good with software, however, the LED is not lighting up. I used a camera to look and no IR is being emitted. I even checked my real tv b gone and i can see that IR LED flashing. Any ideas?
This is the LED I used: https://www.sparkfun.com/products/9349
I attached pictures. I know it isn’t pretty, but it definitely is connected correctly.
Oddly enough, I attached a regular 5mm led and it is blinking along with the code. It’s so odd that I can get a regular led to light with the code, but I have tried a couple IR LEDs and they won’t light. It just doesn’t make sense…
The AM/PM indicator LED on the display connected to the same pin as your IR LED and it probably has a lower forward voltage than the IR LED. What’s likely happening is when you send pulses to the IR LED pin, the AM/PM indicator it turning on and that’s clamping the IR LED pin to a lower voltage than the IR LED can operate. Since a regular LED has roughly the same forward voltage as the indicator on the display, it lights up but because the IR LED needs a bit more voltage, it won’t.
Easiest way to fix this would be to disconnect the AM/PM LED on the display. Rather than trying to disconnect just one pin on the display, it would be easier to cut a trace on the back of the board disconnecting the AM/PM indicator. To cut the trace, get a sharp hobby knife like an Xacto knife and carefully sever the trace on the back of the board that has the blue line across it. (see photo below)
