TVO? What's TVO?

Wouldn't it have been easier to take the antenna switch apart and wire it up to a relay or something....

But where would be the fun in that?

The rube goldberg device is just so elegant.

TVOntario is abbreviated as "TVO" here in... Ontario. I'm not sure why Mark would wire up such a fancy little contraption for a single channel though.

Okay, why does it need a separate input for the one channel? Does Mark have cable and it's only broadcast? Does he need an antenna pointing in a different direction than for the other channels?

Bingo!

We refuse to pay monthly fees for television signals when they are free over the air here (including some HD channels). So we have a small tower with three antennas on it:

• one home-made dipole, aligned to receive nearly all local analog channels, as well as the CBC-HD channels.
• one very large/fancy array pointed at the nearest distant PBS station, soon to be rotated towards a PBS-HD signal instead.
• one UHF antenna pointed specifically at the nearest transmitter for TV-Ontario (TVO).

Our Myth PVR has two HD tuners, and two NTSC (analog) tuners. The latter are normally wired to a combo feed from the first two antennas. The third antenna is not normally connected, because it degrades the other signals when combined with them.

So, we've been using a manual switch box to select antennas for the second NTSC tuner in the Myth box. But we don't always remember to flip the switch in advance of the next recordings.

I've been wanting to automate this for some time now, and so began the effort with a simple relay kit that I found in Toronto for about $15.

At first, I tried wiring the RF coax directly into the relay, but this resulted in more noise and ghosting, and was deemed unacceptable (our reception is normally near crystal clear on all channels, better than some digital cable feeds..).

To keep the signal quality high, we had to stick with a high quality (low loss) sealed-unit RF switch. But how to actuate it? A pair of electromagnets came to mind, but the switch can be somewhat sticky at times.

On Saturday, I stumbled across this geared 5V motor in a local shop, for $7. They also had a nicely mating rubber tyred wheel to fit, for another $5.

And thus the contraption pictured at the top of this thread.

The center contacts of the relays are wired to the two motor poles. The two signal contacts of each relay are wired to GND (normally closed) and +5VDC (normally open). So if both relays are off, the motor is grounded, and nothing happens. If both relays are on, the motor gets +5VDC on both poles, and nothing happens there either. But if a single relay is "on", the motor spins one way or the other, depending upon which relay is "on".

The two relay control inputs are wired to a couple of data lines from the Myth box's parallel port, and the same box's PSU gives +12VDC (for the relay coils), and +5VDC (for the motor) in series with a diode to prevent backflow.

To complete the package, I added an "external channel change script" to Myth for that NTSC tuner. The script just pokes values to the parallel port to turn on one relay, wait 200msec, and turn it off again.

Whirrs like a charm!

Awesome.

On a related note..

I've been looking for some time for a nice, simple, USB-to-GPIO interface solution to control projects like this one, since parallel ports are soon to be extinct.

One of the links from the motor suppliers led me to this USB to serial / bitbang device.

It looks like it could be quite useful, and there may be other suppliers with pricing better than the $33/unit from there.

Cheers

How about this?

pca

It's a good board that one, although you should buy it as a kit for added fun. The linux drivers work well too.

Very cool setup. At my folks house, before they got locals over satellite, they got them all over antenna. The problem was that the major networks were all located in or around DC, while the local PBS station was dozens of miles south of the city. My folks are about 8 miles west southwest of the city, so their antenna wouldn't pick up any of the PBS channels. The only option our satellite installer (not DirecTV-provided - a local guy) gave us was to install a motor that would turn the antenna, but we decided not to go with that due to the equipment being very expensive.

I like your solution a lot, but I'm glad I can get all my local channels over fiber. Thank goodness for FIOS!

Ahh.. that's all good to know, thanks guys.

I did notice one in kit form at our local shop, but there was
too little tech info for me to decide whether or not it would
be easily usable on Linux.

It is perhaps a tad expensive and large for one-of uses,
but fun to play with otherwise.

Along the same vein, here is an electronic replacement
for the relay board I used.

And here is a nice, cheap real-world relay interface kit
that works over serial (or USB if one adds a USB-serial converter).

EDIT: And, ooooh.. remote control of stuff via the telephone,
and reasonably priced, too. I can't think of how many times
I've wanted something like this, to reset or power-on a box
while I've been far far away..

I had a friend here, who installed a largish antenna + rotor on a tall tower for television reception. In his location, half the channels where one way, and the other half were about 90 degrees rotation from there.

His rotor master box used a hand-held IR remote control to directly dial in degree settings.. so we wired up an IR blaster (IR LED connected to a serial port) on his Myth box so that Myth could automatically rotate the antenna as needed.

Very cool.

How about using an Arduino to control it? The newest ones have a USB to Serial interface on the board, and they are easy to program.

http://www.arduino.cc/

(I've been playing with these for a bit, and like how easy they are to work with)

Ahh.. good. Another brand/source for this kind of stuff. These ones look a little less turn-key than some of the others, but in the same ballpark for price.

Thanks!

Ahh! Now we'er talking: $15 USB to serial/GPIO board!!

Woo-hoo! Gotta order me a dozen of these!

Cheers

Well, okay, two of them anyway. Plus a motor controller!
And it's in Canada (cheap shipping!) and in Canadian currency!!

Woo-hoo!!

Thanks for the pointers!

The Arduino is all open hardware/open source, so of course it'll be a little rough around the edges There are a lot of people using them for little projects just because it is so easy to work with.

Also since you're looking at just a USB->Serial with some GPIO pins, take a look at this http://www.gridconnect.com/xportdirect.html
It is a Ethernet to Serial interface also with some GPIO pins.

I'm using one of those hooked into the Arduino I've got so it can talk to the network directly without needing a computer.

That's not rough, but, rather, more flexible!


Mmm.. only two GPIO pins, and a surprising lack of information about the product -- not even a pin-out description. How not to sell something on the web.

But it could be useful in combination with the Serial Relay control box..

Thanks!

You need to go the manufacturer's site to actually get the info. Gridconnect is just a reseller. I've used a few of their smaller XPort modules before and they work well if a little lacking in GPIO.

Yes, I only pointed you to a reseller of it, Tman's link is to the people who make the thing, and they have all the documentation there.

And yes, the Arduino is very flexable

http://blog.makezine.com/archive/arduino/

I'd hardly say it was rough round the edges. Compared to commercial products like Picaxe it runs rings round them.

I haven't worked with too many other development systems, so I don't have a good baseline to work with. I will say that working with the Arduino is getting easier with all the new info coming out every day.

Didn't you mean to link to this .

No, the other one I did link to was only about 2/3 of the price of that one, and has a mini-USB-B connector instead of the more bulky full-size B connector. It also seems to have quite versatile I/O capabilities.

But there are several appealing alternatives there, including the one you linked to.

Cheers

I guess I was confused by the lack of GPIO being mentioned in the linked item.

Yeah, it's all described in the full datasheet for the chip.

Cheers

So getting back to the original post.

I dub thee Frankenswitch.

But, is it really difficult to build a composite antenna. Ok call it a Frankentenna. Where several directional antenna are combined and present via a single feed.

Now, there's a good USB Device string I could use for the next version of it!

I've got my new solid state motor controller PCB (just a chip, really), and the USB-to-Serial-and-GPIO converters.

I'm going to combine one USB converter with the motor controller and motor, into a simpler bus-powered Frankenswitch device. This takes 3 GPIO pins: one for "clockwise", one for "anti-clockwise", and another for "idle" mode.

That still leaves many more pins, and a full serial interface unused.. mmmm...

Cheers