DIY TiVo IR Blaster

DIY TiVo IR Blaster

Recently I discovered that our local cable provider will soon be discontinuing analog cable service for most channels.   Because of this they are forcing encouraging customers to get new cable boxes and upgrade to digital cable.

I hate cable boxes.  More than just another piece of equipment to find a place for near the television, cable boxes waste power, always seem to take forever to change channels, contribute to the ball of wires behind the entertainment center, and add another remote control to the coffee table.

Most importantly, a cable box prevents our old Series 2 TiVo from being able to change channels directly, since it now has to negotiate with the digital cable box to receive TV signals.

TiVo provides a workaround for this – the infamous IR blaster.

I would love to meet the engineer who came up with the IR blaster.  Instead of pushing for a universal protocol to electrically connect cable boxes to things that may want to control them, some engineer came up with the incredibly stupid great idea to stick an IR LED in front of the IR receiver of the cable box and use it to simulate a handheld IR remote control.  The cable box thinks that the user is punching away at the remote (with lightning speed) while in reality a microprocessor is generating the remote codes and sending them to the LED.  It’s both ingenious, and at the same horrific in so many ways.  It grates against my engineering sensibility.  What manager approved this?

Back to the TiVo.  The IR blaster that came with our TiVo was lost long ago, in a time when no unnecessary electrical-optical-electrical sillyness was required for it to function.  Rather than spend $3 on eBay and wait a week to get a replacement, I decided to make one out of spare parts in my junk bin:

  • an infrared (IR) LED
  • a 1k resistor (not sure if this is necessary, safety first)
  • a 1/8″ mono headphone plug with a couple feet of cable attached
  • some heatshrink tubing
  • duct tape

I don’t know if the resistor is required – the TiVo may already have an internal resistor.  I used 1k, if I see any problems with the cable box getting an intermittent signal I’ll try lowering the resistor to 330 ohms.

The tip of the 1/8″ mono plug is positive.  I connected the tip wire to the side of the LED with the longer lead (the side opposite the flat side of the LED).

DIY TiVo IR Blaster

I tested the circuit by applying 3-5V to the 1/8″ plug (tip is positive) and used my digital camera to check if the LED is working.  My camera has a decent IR blocking filter so I had to use nightshot mode to see it:

DIY TiVo IR Blaster

Finally, I put heatshrink over the LED connections and the resistor to avoid short circuits:

DIY TiVo IR Blaster

Back in the living room I plugged the DIY IR blaster into the jack marked ‘IR’ on the back of my TiVo.   A strip of duct tape to secures the wires to the bottom of the cable box.  I bent the LED up to point at the cable box’s IR receiver (the purple dot shown in the really bad photo below, sorry).

DIY TiVo IR Blaster

All that was left was to configure the TiVo using the cable box setup guide.  Within a few minutes I had my TiVo controlling the cable box.  The DIY IR blaster works perfectly!

Not bad for $0 in parts (all stuff from my junk bin) and a few minutes of soldering.

Update November 2016: In the vast majority of applications, the series resistor is not required. The majority of IR blaster circuits built into A/V equipment (and video game consoles such as the Xbox) include built-in current limiting circuitry that makes the resistor unnecessary.

20 thoughts on “DIY TiVo IR Blaster”

  1. What if I want to use the cable remote sometimes for OnDemand? I recently moved an older setup from MA to NH and had to get a newer Cable box that would not accept the serial input. Thinking of some kind of clip arrangement for the blaster. Any thoughts? All I really wanted was an old cable box. Sniff.

  2. Thanks for the details on the polarity etc. saved me a bit of time on building this. Total cost: $2.50 (one set of junky earbuds from Wal-mart to use for the plug+cord). 420 ohms resistor found in parts bin, same for IR LED – bought as a 20-pack about 10 years ago, never got around to using them anywhere. Also from parts bin: solder, flux paste and a bit of Kapton tape to hold it together.

    TiVo up and running with the new (now required) cable box.


  3. i made this yesterday and it worked immediately. I had the mono-plug laying around and walked to a radio shack to pick up the IR LED and 330 Ohm resistors for a total of $3. I also used speaker wire for the go-between. thanks!

  4. Thanks for the quick solution. Just built one this afternoon with a Radio Shack IR LED (940nm, Catalog #: 276-143, $1.99) and a 1/8th” mono phone plug (Radio Shack Cat. #:274-286, $2.99 for two).

    I, too, used a 1k Ohm resistor (since I had some sitting around), but 330 ohm would have been fine…maybe better/brighter. Anyway, it works fine with a Series1 TiVo and the Motorola DCH70 cable box from Comcast (remote code “00093-Fast” in the TiVo setup).

  5. I used this exact article to make a replacement IR Blaster for my Hauppauge HVR-1250. I purchased from Radio Shack a 6 ft. 1/8″ Mono Audio Cable, the 1K resistor and a single IR Emitter LED. Total cost out the door was $5.97. Thanks

  6. That’s awesome. I came across your posting looking for an ir blaster to purchase because my cats destroyed mine. I do not have the skills or tools to build such a thing but I like the fact that there are people out there that can and do.

  7. Thanks for posting this! The IR LED seemed pretty dim with a 1k limiter when usedd with a Panasonic Replay (compared to the remotes led’s), & I’d feel safe starting out using something around half that value, but I really dont want to take it apart! Thanks again!

  8. You all sound like you’ve got this stuff figured out so I thought I’d ask what may be a dumb question. We have a series 2 single tuner Tivo and get out local channels through an OTA antenna. We also have Dish satellite (not HD). Our TV is HDTV so we now can view OTA in HD (really great). My question is whether or not it’s possible to hook up both a digital converter box and satellite box to the Tivo and have it record from either source. I have 2 sets of Tivo IR emitters and have seen a coupler (outrageously priced at $20) but don’t want to buy the coupler if it won’t allow you to record from both sources. Also, would a simple headphone splitter work as a coupler? Thanks so much.

  9. I wouldn’t call it a dumb interface. Someone had to come up with something that worked with existing technology from many vendors, so even though it’s not ideal, I think it’s a pretty good idea. I like how simple your solution is. I’ve seen plans on building them before and I thought they were more complicated.

    I use a MythTV box and it connects to my digital cable box (motorola) through a serial port on the back (like Tom mentioned). It’s much faster than using the IR blaster too.

    Another cool trick is that some cable providers still send the analog channels over the wire even if you have digital cable, so if you have a MythTV box with two tuners, or I think some TiVos have dual tuners, you can connect one directly to the cable and one to the cable box. This means you can record two shows at the same time if at least one of them is on one of the analog channels.

  10. I agree IR Blasters are dumb. But what choice does TiVo have?

    I used to have DirectTV. TiVo has a serial port adapter you could use instead of the IR Blaster. It worked great until DirecTV upgraded the firmware. The IR Blaster continued to work.

    I have FiOS now and that can only do IR.

    All the cable boxes are designed to be used by a human with a remote. So are TVs, DVDs, Stereos, VHS. Someday, there will be a universal wired protocol & adapter to connect them, probably on ethernet. Each vendor will come up with thier own values for each device they make, just like remotes are today.

    It’s a kludge, but it’s good enough.

  11. “Not bad for $0 in parts (all stuff from my junk bin) and a few minutes of soldering.”

    That’s what you get for having that huge junk electronics pile stashed away somewhere in your house =) Love it.

  12. Tom – Thanks for reading the blog. I wish I could post more often but work is keeping me tied up these days. That and getting ready for the Maker Faire. I’m hoping that within the next few years I can cancel cable and go 100% internet viewing. It’s coming…

    Matt – The TiVo is pretty fast. However, there is still that 1/2 – 1 second delay changing channels due to the cable box itself which annoys the heck out of me!

  13. I like your replacement solution :-). Back in high school, we used to have a building-wide AV network that was controlled in a similar manner. Each classroom had a regular TV hung from a wall, with a control signal coming from some central location, that could turn the TVs on remotely and tune them to the school ‘news’ at a certain time. It was interesting the first few times, but watching the system slowly send out each digit of the channel got boring after a while. I hope the Tivo version is faster!

  14. New commenter… read your blog as often as you post 🙂
    I agree wholeheartedly. Dumb dumb dumb interface. Yes, it works without necessitating that Cable Box manufacturers add another way to interface, but simply is too problematic. We spend time adding IR modulation, demodulation, and optical transmissions. Either the blaster IR moves away from the sweet spot and fails to change the channel, or some fluke occurs on the Cable Box, and presto, instantly missed recording my favorite show.
    It is a problem with Windows MCE as well.
    Thankfully I can find most shows on-line for post air viewing… but is that really the point?

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