Use ordinary D batteries to power a small DTV converter box connected to a portable DVD player or handheld TV.
Last September, Hurricane Ike swept through town and just about everyone was without power for days, unable to get news or weather updates. Being a computer programmer, I have two backup UPS (Universal Power Supply) battery backups that I charged up in advance so I'd have *some* emergency power during the inevitable blackout.
When the storm hit, I was able to power my portable TV for a mere 3 minutes before my UPS was drained. My sister took shelter at a friends' home, who happened to own one of those tiny 2.5" battery-powered handheld TV's. My sister noted how helpful it was (and would be) to have one for emergencies, but I reminded her that after February 17, (now June 12) 2009, that handheld TV would be nothing more than a paperweight, as TV stations went all Digital.
I then started looking online for a portable digital TV, which I discovered all cost between $150-$350. Ouch. That's when I started thinking about just plugging a small DTV tuner into a handheld TV. It wouldn't be as "portable", but I didn't care about "portability", just something to provide TV reception during a blackout. If the TV was powered by batteries, I only needed to power the tuner, preferably using cheap off-the-shelf batteries that I can stock up on the next time a storm hits. And once the Digital switch-over takes place, those old handheld TV's are going to become super-cheap as people find they can no longer use them.
To save even more money, I ordered two government $40 DTV coupons online and (after much research) used one to purchase a "MicroGEM MG2000" Digital Converter Box (the smallest unit made) for the most compact package. The power requirements of the MG2000 is only 6.5v. Hoping I could power it with only 6v (four 1.5v batteries), I also purchased a 4-D cell plastic battery holder (only to discover later it just wasn't enough power).
Mostly, this "Instructable" is just about building a battery pack for the DTV tuner. Everything else is done for you. If you find/have a DTV receiver whose power requirement is an *exact* multiple of "1.5v" (6v, 7.5v, 9v, 12v), you can do all this without "building" anything!
I apologize for not having taken any photos *during* construction, but I didn't think of turning this into a how-to until after I was done.
Step 1: Materials:
1. Low-power Digital TV Converter Box. If you don't already have a Digital TV Converter Box, I recommend the "MicroGEM MG2000", the smallest unit on the market at 4.5" square. It's also one of the top rated units out there. If you can still order one of the free government $40 "coupons", do so asap. The MG2000 is apx. $55 (before coupon).
2. Portable video player, such as a handheld TV. I purchased a used 8" portable DVD player on eBay just for this project for $40. Your device MUST have external "Video In/Out" and "Audio In/Out" jacks. If you already have a portable DVD player or old portable TV, use that and save yourself some money. I chose to use a DVD Player because most have a "widescreen" display (perfect for DTV) and a 3-hour battery pack.
3. ONE 4 D-cell battery holder with "snap terminal" (aka: 9volt style) connector, and ONE single D-cell battery holder with wires. I found the 4-cell holder on eBay for $6 (after s/h) and the 1-cell holder at Radio Shack for 99cents - or try this. (This is what I needed to power the 6.5v MG2000. If you have/buy a different receiver, be sure to buy the correct number of holders for enough batteries to power your receiver.) Be sure to use D-cell holders for maximum battery life.)
4. One 2.1x5.5mm (tubular power connection) to "9v clip" for conecting the "snap-terminals" of the battery holder to the DTV receiver (+ center, - sleave). I found this at a local electronics supply for $3. ("Electronic Parts Outlet [EPO]" part#: RC-9v-2155).
5. Five D-cell batteries.
6. A small piece of wood to mount the battery holders, 7"x3" (1/4" thin is best).
7. Silicone glue for mounting holders to board.
8. Two small machine screws cut down to apx. 1/4" long, with nuts.
9. One thin metal "plate", 1/2" square, with a hole in the middle for the screw.
10. Depending on your video display device, RCA cables to connect the audio/video output of your Converter box to your display. I used a single RCA-to-2.5mm for video and a dual RCA-to-2.5" cable for audio (both found at Radio Shack). The audio cable is easy to find just about anywhere. The single RCA-to-2.5mm cable can be a bit harder to find (Radio Shack part#: 42-2444A - "Audio and Digital-Camera Cable").
11. Rabbit-ears or other small UHF antenna (or Google DIY HDTV antenna).
I already had most of these items, so my total cost was about $65, the most expensive items being the used DVD Player and new HDTV tuner. If you find a tuner for less than $40, it'll be free with the government coupon. And many people already have an old portable TV that would otherwise become worthless after the national switch to DTV in February, taking your total cost down to just a few bucks for batteries and cables.
Step 2: Pre-testing:
(If you don't need to construct the battery pack because you can get a holder for *exactly* the right voltage for your tuner, this is your only step.)
If your portable DVD player (or other portable video device) has a switch for video In/Out, be sure to switch it to the "In" position. Plug the single RCA-to-2.5mm cable between the yellow "Composite" jack on the tuner and the Video In jack on your video player. Do the same with the Red & White audio cable and the audio jack on your Player.
(I tried this with a different portable DVD player that input both audio & video through the same port. Despite this, every 3RCA-to-2.5mm cable I tried failed to produce video. I solved this by using the *2RCA* stereo audio cable for both video and sound, plugging the Red plug into the yellow video port on the tuner and connecting the white plug as normal. You won't get stereo, but at least you'll get both picture and sound.)
Connect your Rabbit-ears antenna to the tuner. You may need a 300ohm ("horseshoe contacts") connector to 75ohm (cable) adapter to connect the rabbit ears to the "video-in" on your receiver. These are common and found most everywhere. If you're like me, you probably have two or three just laying around the house. They're tiny boxes with a round male cable jack above two screw wire contacts). You can collapse the antenna rods since DTV only uses the UHF loop.
Plug in your DVD player and DTV tuner using the supplied power cords (we just want to make sure everything works first). Turn on the tuner and the DVD player. If all is well, you should see *something* on your player, either TV or the tuner's menu. If this is the first time you've used your receiver, you may need to scan for channels before you can watch TV. Make sure you are getting both picture and sound before proceeding.
Digital TV on your DVD Player. Cool.
Step 3: Procedure for Building Your Battery Pack:
Take the 4-D cell battery holder. At the bottom, there will be a wire (or some other connection) bridging the bottom two contacts. You will need to snip this so the batteries are no longer in contact with each other. The positive terminal will stay in place, but the negative spring contact will need to be held in place with a piece of metal and a screw. When batteries are inserted, there should be roughly a 3/8" gap where the spring compresses, just enough room for a short screw. There should be holes in the bottom of the battery holder where the contacts are. Insert a screw through the hole. Hold the spring in place with the metal plate. Fasten the spring in place with the nut on the inside and the screw head on the outside of the holder. Insert a screw through the positive side next to it as well, head on the outside.
(sorry for the blurry pic. Close ups tend to be fuzzy, but you can see the metal plate and the screw inside holding the spring in place.)
Step 4: Attach Holder for Fifth Battery:
Strip the tips of the single D cell holder wires just enough to wrap them around the two screw contacts you just inserted on the 4-cell holder. Be sure to connect the negative wire to the positive screw contact and vice versa so the power runs through the fifth battery (this gives you a total of 7.5v of power, 1v more than the MG2000 needs, but enough to power the receiver without harming it. 6v isn't enough power w/o the signal cutting in & out, and there is no combination of off-the-shelf 1.5v batteries to give you exactly 6.5v of power.)
Step 5: Test:
Now that your holders are wired together, you can test your battery pack before mounting it to the board. Insert the batteries and snap the "9v to 5.5mm sleeve" power connector to the snap terminals atop your battery pack. Plug the battery pack into the DTV tuner and turn the tuner on (the MG2000 goes on the moment you plug it in). Turn on your DVD Player. You should be getting TV. If not, try changing channels on the converter box and moving your antenna until you do.
Step 6: Mount and Done!
If everything is working, turn off the DVD Player and unplug the battery holder from your tuner. Apply a few dabs of silicone glue to the board and affix the battery holders to it. Glue should dry in about an hour. You might want to wrap the holders down with masking tape while you wait for it to dry.
That's it! Now, the next time the power goes out, you'll still be able to watch Digital TV. Especially useful in a storm when you need weather updates. By using D-cell batteries, the unit should stay powered for several hours. And if they go dead, you can easily replace them. The biggest drawback of my particular setup is the rechargeable battery pack on the DVD Player. But if you use an old handheld or portable TV that can run on disposable batteries as well, as long as you have batteries, you've got TV... even after the DTV switchover in February.
Enjoy your new battery powered HDTV!