NerdKits - electronics education for a digital generation

You are not logged in. [log in]

NEW: Learning electronics? Ask your questions on the new Electronics Questions & Answers site hosted by CircuitLab.

Project Help and Ideas » TV remote prank project

March 18, 2010
by Solorbob
Solorbob's Avatar

I'm thinking for April fools, I should fix up a special TV remote for the ones I love. I was thinking about adding the nerd kit and a switch, so when the prankster is turned on, it will do random things like: for ever one channel you go up, it goes back two. If you turn the volume up, it will mute the TV. Then sometimes just pick a channel to turn the TV to.

What does everyone think? I'm feeling pretty evil!


March 18, 2010
by mongo
mongo's Avatar

I like your thinking...

It would not be easy. You would have to know the signal coding for each function and be able to program them into the circuit. It can probably be done but it sounds like quite a task as there are hundreds of different command sets. Just about every manufacturer has their own set and they are again different between the devices. TV control codes don't operate DVD player codes, etc.

I have an old programmable universal remote that I can assign different codes to individual buttons and could do the same thing. My big problem with that is I would probably be my worst victim.

March 18, 2010
by Solorbob
Solorbob's Avatar

I'm a workshop maker slash hardware hacker, so I was thinking along the lines of trying to hook up connections to only certain keys. Here is the trial and error part comes in. I'll set a pin on the nerdkit to see if I can get a reading when the up channel is pressed, if so, just use the MCU to make the connection to the down channel button two times.

I don't really have the background to do the code sets as you were talking about.

I was just going to do this type of button hijacking to 7 or 8 buttons. I was thinking channel up, channel down, 3-4 numbers, and mute.

Would it work... I don't know, but I will buy a $5 universal remote to hack up and see. But I'm open to ideas.

March 19, 2010
by BenFL
BenFL's Avatar

It might be possible to get an IR sensor and hook it to the nerdkit. Then you could point the remote control at it and press the buttons and have it record the signal then you can get an IR emitter and project that signal back out. Also I have found that my cell phone camera and some digital cameras pick up the IR light from remote controls. Maybe you could try using something like that or a video camera with a night mode that uses IR light.

March 19, 2010
by johnh
johnh's Avatar

Interesting project.

I like the idea of wiring it to the remote itself, but I am not sure how well that would work with the internal electrical signals (for one thing, the voltages are most likely different).

IR is an interesting protocol, and contains certain optimizations to allow for low transmission power and likelihood of delivery.

The majority of IR signals are transmitted at 38 khz. This allows the receiver to look for signals in that range while ignoring extraneous transmissions form other sources. The transmitter than pulses this 38 khz signal to control transmission.

I think you have two options if you want to go the IR route:

  1. Get a darkened room and set up a normal IR led and an IR receiver (this is probably available at RadioShack). You run into a problem that the receiver has no internal amplification circuitry, and so you will want to hold the remote close. Write code so that when you press the button it will store the signal to internal memory or print to zero. I would advise sampling once per clock cycle and storing each one as a logical 1 or 0 to memory. Then simply use that string to flash the IR LED. that should work, but I've never used this method (simple IR receiver), so I don't know how well that would work.

  2. Your second option is to find a IR receiver/ amp / demodulator. This device will demodulate the 38 khz signal, internally boost it, and output a logical 1 or 0 to a pin on the MCU. Use a similar technique as above to record the signal to the MCU or serial out. The advantage here is that you don't have to deal with the sensitivities of the above method, and stand a stronger chance of success. Use an internal clock and PWM to flash the IR LED at 38 khz, and then write it logical high or low based on the string you generated.

In both of these scenarios, I would write a piece of code for a device that will sit (physically) in front of the TV's IR receiver. When the MCU's IR receiver gets the appropriate code, it will instead transit the replacement code. try to write it so that it will directly retransmit most codes without modification.

(If you are familiar with the concept, think of this as a Man-In-The-Middle attack)

Good luck. On a side note, if you have an ocilloscope, try hooking it to the remote's IR leads and seeing what you get.

You can try using the IR receiver here: AllElectronics

It may not get there in time though.

March 19, 2010
by Solorbob
Solorbob's Avatar

Thanks all. I do have some leftover IR LEDs and receiver in my toolbox. I'm starting to think that this might be out of my skill set for needing this done in say, 12 days. I'm off work all next week, so I may take a crack at it. Well see.

June 09, 2010
by Herover
Herover's Avatar

I remember I found a article about defcon 16 badges killing TVs.

There is some tutorials about making these, but it's not easy!

Post a Reply

Please log in to post a reply.

Did you know that multiple microcontrollers can communicate with each other? Learn more...