Adding Remote Control To A TV

For an off season electrical project, I wanted to add remote control to an old t.v. I have found a good IR sensor to use, but I am not sure how to integrate it in with the tv so that I can control power, volume and channel.

Does anyone have any suggestions?

No advice for you on how to do this, but with the digital transition next year why bother (or even without it… guess its a good practice project though)?

Not as easy as it sounds.

The hard part will be learning exactly how to control power, sound and channel. There probably are switches for these functions, what you’ll have to do is open up the TV and get access to those switches, the actual wires or PC Board spots where they contact closures are happening. Run wires from the switches you need to conrtol to a connector (this will make things easier, trust me), and then build a circuit that creates contact closures in parallel with the switches, controlled by IR.

That can be as simple as a microcontroller closing a relay when “signal xxx” is received by IR.

A word of caution: There are dangerous (as in FATAL) voltages present inside a TV, for weeks after the TV was last connected to power. The TV Tube runs at several kilovolts, and is essentially a big capacitor, storing that voltage for a long time. STAY AWAY from the picture tube, the rubber 'suction cup" that insulates the HV wire to the tube, and everything that the HV wire connects to (gegerally a HV transformer called the “flyback transformer” on the circuit board).

ALSO, a TV metal chassis is NOT GROUNDED, but it is HOT, as in it carries LINE VOLTAGE even with the TV set switched off. UNPLUG the TV before touching it. Never power it up unless ALL covers and screws are in place. Ever.

There are other lethal surprises inside a TV, so just be real careful. ALWAYS work with one hand in your pocket - really - as this helps protect against stopping your heart if you do manage to touch something.

Sorry, an old TV engineer here, and have seen guys get very nasty surprises. I once got an HV jolt from a 19" TV that was unplugged for almost a year (!), it knocked me across the room, onto the floor, and my arm was numb for a whole day. Truth.

Don

MEGA everything Don said.

Old TV’s are lethal. Just to give you an example of what Don is talking about you can estimate the anode voltage of the picture screen at about 1,000 Volts per diagonal inch size.

So for a 27" console TV, you are talking 27,000 volts on that bugger and it will stay there for a year and longer.

This is one area where you want an old hand in the room to show you how to work on this thing.

It’s a miracle I’m alive after all the stuff I did with TVs and Radios when I was your age. If you survive it, electricity hurts really bad.

How is the TV controlled now? Does it have a row of pushbuttons, or an old-style pair of rotary switches?

I ask because I think it would be very cool to have a system that operates the original controls internally, like a player piano. It would probably be easier to do with a rotary switch TV, since you could just use servos (albeit very powerful servos) to control them.

About CRTs…

One way to make this project less dangerous would be to properly discharge the CRT before messing around. However, doing this would be more dangerous if not done correctly, so definitely find someone who knows what they’re doing if you do decide to attempt it.

While this is a cool idea, don’t forget that once you can read an IR signal, you can do anything you want with the output.

We use PIC 16f627a chips programmed with PIC Basic Pro (www.melabs.com) to read the Sony IR Control System (SIRCS) codes. In PIC BASIC Pro this can be done in about four lines of code if you are using an IR receiver such as the PNA4602m.

Then we use the PICs to control an L293d motor driver and run mini-sumo robots around. The PIC also has a nice serial interface, so you could build an IR receiver that you could hook up to your PC.

In the reverse direction you could use the PIC to control an IR LED and send out randomly timed signals to turn the TV on, off, or change the channel. Hook it up to a battery, cut out the middle of an old textbook, and sit it on a friend’s bookshelf across from their TV.

Check back later to see if you still have a friend!

There are many, many fun things to do with IR remote control that don’t involve sticking pointy conductive things into high voltage boxes. On the other hand, if you MUST control an old TV… consider using a servo to turn the volume knob manually, and a geared down motor to change the channel. That way you have a mechanical challenge as well as a software one, and don’t risk learning the hard way that capacitance is a really, really amazing thing.

Jason

P.S. You can believe Don… really… TV’s are nasty little buggers.

ha, ha,

If you didn’t have any friends then everyone would say “sure, go ahead”.

regards,

Thank you for all of your comments. Judging from the dangers hidden in the tv I decided to not add anything internal. Now I am thinking of making an ir controlled power on switch that would be placed between the power plug and the wall outlet. This seems like a safer route to take.

Here’s the back of a 1959 RCA b/w portable TV with remote…the little chassis on the lower left corner is the electronics for it, and you’ll see the motor at the top left that turns the tuner control around. One position of the tuner is “off”. The only control is for channel, as far as I can tell. I don’t have the remote for it, but I think it’s ultrasonic.





I say make a Rude Goldberg style switcher with an some kind of external controller to interpret the IR signal (any small programmable microcontroller will work) and maybe a bunch of servos that manually push the buttons on command. Use your imagination, don’t give up on it

Although making a switch for it would be much more fun, Radioshack sells something simmilar that uses RF.

http://www.radioshack.com/product/index.jsp?productId=2856857&cp=&sr=1&origkw=remote+switch&kw=remote+switch&parentPage=search

Kevin,
There are so many different designs for TV it is hard to give a rule of thumb on anything. How old is the set? Who made it? It is possible that the manufacturer made several models using the same circuit board and chassis. You may only need to poplulate the parts on the board for it all to work.
The picture above is a TV using a “turret” tuner. Those were easy to remote with a motor driving the tuner and a series of relays stepping through an attenuator for sound. The remote control shown in the picture above was available in some sets as an after market option your TV shop could install. FM stereo decoders were also available this way in the early days of FM radio. TVs in the past 20 years have used electronically selected tuners of various types. Some were digital and some analog and all of them hard to interface to in the set.

As Don and Ed have stated, TVs can be hazardous. You can pretty much expect a color picture tube to have 25,000 volts or more in operation. B/W at least 9000 or more. The high voltage design uses the low leakage glass of the picture tube as part of a power supply filter capacitor. The low leakage allows the set to hold that charge for years under certain conditions. Manufacturers also found that line operated power supplies (those without transformers) could significantly reduce not only the manufacturing costs but shipping as well, by removing the transformer. These sets are known as “hot chassis” since one side of the power line wiring is connected directly to the chassis or circuit board ground. That places 120 VAC (RMS) on exposed metal with the covers removed. The primary power used in these sets is then the full wave rectified power line voltage or about 165 volts. It is best to get some experienced help to show how to work with these hazards before attempting it yourself.

I like the idea of using small motors to turn the knobs on the set. Would it be possible to use the power from the pulses from the IR receiver ex(a tauntek device) to directly operate the motors? My idea is to use that power to make a small motor run in small jumps to change volume or channel.

Thank you for mentioning that you are using a Tauntek IR receiver. The more information you provide, the better we can answer your questions. In this case it would have been very helpful if you could have provided the exact Tauntek model you are using and a link to their website embedded in your question. Sure we can Google it ourselves, but if you provide direct links we can spend more time answering your question and less time looking up what parts you might be using. Telling us more about what motors you have available… servos, VEX motors, stepper motors from old hard drives, etc. can also help us make useful responses.

Looking at a schematic for one of the Tauntek IR recivers (http://www.tauntek.com/TinyIR-four-channel-schematic.pdf) it appears that the outputs come directly off a PIC microcontroller.

PICs are typicaly able to source/sink about 25mA per pin. Although that is enough to drive an LED, you would have a hard time running any motor off of that! You have a number of methods available to do this, including simply hooking up a transistor to amplify your signal from the PIC. If you want a small DC motor to go both forwards and backwards, you will need an H-bridge circuit, like this one http://library.solarbotics.net/circuits/driver_tilden.html or an H-bridge chip like the L293DNE. If you are using a stepper or servo motor you may need to build a custom interface, as both those devices expect a modulated signal.

So in a word… NO… don’t hook a motor up directly to the Tauntek. At best nothing will happen, at worst, you’ll fry your PIC chip. But DO experiment with some of the circuits here, take some time to google “H-Bridge” and “motor speed control”, and other related topics and feel free to ask more questions here.

Jason

At the risk of being redundant …

1> If you do not know EXACTLY what you are doing in the back of a television set, find someone who does know or do not open the back.

and 2> if you do open the back up, if the set ever leaves your sight (even if it’s just for 5 minutes), assume the flyback is charged. Take this advice from me, as I was kicked from the flyback of an Emerson 25" color TV I had properly discharged 5 minutes prior and was called away, only to have someone else plug in the TV, turn it on, realize it was still not working, shut it off and unplug it :eek:

Needless to say, I was lucky to come away with a very painful lesson.