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Inside the WowWee Rovio TrueTrack Beacon

For those curious about what is inside of the Rovio TrueTrack beacon, and for those who are having problems, here's the inside scoop.

How To Hack Open The Rovio TrueTrack Beacon

Removing the beacon 'eyeball' from a dock or a room beacon is pretty simple- all you need is a medium phillips head screwdriver, and a 1.5 mm hex key to open the eyeball. 

  • Remove the mast- squeeze the plastic tabs on the bottom together to unlock, and wiggle the mast out.
  • Remove the 6 screws from the underside of the base. Set them aside with the baseplate so they won't get mixed up with the others to come. 
  • Remove 2 screws from heat-sink and 3 screws from the circuit board.
  • Remove 3 screws holding the beacon base to the dock.
  • Remove 3 screws on the beacon retaining ring.
  • Now you can use the hex wrench to remove the one screw holding the eyeball halves together, on the side where the power wires come out.

This is the inside works of a 50 Hz room beacon. You can see the 4 small screws that hold the lens assembly on. At the bottom, R42 is present next to J3 marked "50 Hz": you can convert this beacon to a 60 Hz simply by removing R42. The labeled thru-holes on the right (CEB, GND, SDA etc) are not present on all versions of the beacon. At the top, to either side of the largish capacitors, are the three pins of the output transistors that drive the IR LEDs. Jump down to see the other side!

This is the LED side, that is normally covered by the lens assembly. At the top are two transistors, marked 'C2328A' on this particular beacon. This matches the part number for a 1W  NPN power transistor in a TO-92L package. From this view, the pins (left to right) are Emitter, Collector, Base. The IR LED is connected between the collector +5V, so the transistor is sinking the current to ground.

Repairing the Rovio TrueTrack Beacon

If your Rovio starts reporting 'Low Nav Signal' even when docked or under the beacon spots, it's time to check the IR LEDs. If you have a digital camera, try aiming it directly into the beacon lens- you should be able to see two bright spots if everything is OK. If you only see one, or no bright spots at all, it's time to open your beacon. [Caution: it is easy to damage other components on the beacon when probing - 


There are several reasons why your IR LED may not be working. Before buying anything, check the following to determine the cause. Then proceed to the appropriate repair section below for further instructions.

  1. The LED itself may be burned out. Use a voltmeter to check the voltage across the LED. A good LED will show about a 1.5V. If the LED is dead, you'll see about 4V, because no current can get through the LED.
  2. If the LED is good, feel the transistors: if one (or both) are very hot (too hot to touch)- unplug the beacon! Your problem may be in the tiny surface mount package marked 'Q1' on the other side of the board. Q1 is a dual-NPN transistor package, and if defective, can be replaced with a pair of any small-signal NPN transistor such as 2N2222A. 
  3. If the transistor is cold, it may possibly be burned out. Examine it closely for damage and give it the sniff-test.

1. Replace LED

Acquire replacement IR LED(s). Look for 940 nm output wavelength, narrow angle LEDs with ~1.5V forward voltage. Radio Shack 276-143 will work; in the UK, RoboCommunity member Hubba found that Maplins code number YH70M also worked. To prevent burn-out of your new IR LEDs, also acquire some 10 ohm 1/4W resistors (recommended for 100mA LEDs). [since the beacon is flashing at 50% duty cycle, current of up to 200mA should be safe. The voltage drop from the LED to ground is about 2.5V and there is already 1.8 ohms resistance, so 2.5V/(10 + 1.8 ohms) ~= 212 mA]

You may need to adjust for a different beacon board layout, but in all cases the center terminal of the output transistor is connected to the (-) side of the LED (commonly the short lead), and the (+) side of the LED is connected to VCC. Bend the leads of your resistor and LED as indicated below, trimming the lengths to match your board layout. Solder the leads to the terminals as shown here.

Here's my board after attaching the new LED. I should have trimmed the side of the new LED a bit so as not to obscure the red LED, but it still works! My nav signal (using http://X.X.X.X/rev.cg?Cmd=nav&action=1 where X.X.X.X is replaced by Rovio's IP address) is now around 11,000 when under the beacon spots.

Here's the red beacon pattern now:

 If you have discrete LEDs on your beacon board, carefully unsolder the defective LED and lift it off (as demonstrated by Nocturnal below). Bend the leads of your LED to match the pads, keeping them short so the LED will sit low to the board.

You should now test the beacon with Rovio and confirm that both IR LEDs are working and that Rovio is detecting a good Nav signal now. You can also use your camera to verify that both IR LEDs are now lit.

Nocturnal graciously photographed the output of his repaired beacon, verifying that these LEDs can cast a usable beacon signal!

2. Replace Q1

This will be the focus of a future article.

3. Replace the output transistor

This will be the focus of a future article if warranted (I haven't found any to be burned out or in need of replacement yet!)

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Discussion:    Add a Comment | Comments 1-15 of 31 | Latest Comment | 1 2 3 Next »

March 10, 2009 10:43 PM

Any idea where to get a beacon though? No one seems to have them in stock.

March 10, 2009 10:43 PM

Any idea where to get a TrueTrack beacon? No one seems to stock them anymore?

March 19, 2009 12:29 PM

A note regarding wonky beacons;

For anyone who has had their beacon apart and it is now only showing up as "beacon 0" in the Rovio UI it is possible (likely?) that the little "fingers" of the channel-changing ring have bent and are no longer touching their contacts (seen in photo 2 above). Stretch them back open just a bit (using a small flat screwdriver, or even a fingernail), very carefully so as not to break them, and they should make contact again.

For those who have not yet opened their beacon, when you do decide to open it be careful not to toss the ring contact-fingers-down on the desk ;)

Watch out, don't step in the anthropomorphization.

April 19, 2010 9:04 PM


This is a great guide/tutorial.

Works as advertised.

I needed to replace both IR LEDs and the guide helped alot!

Here is shot of night vision with two replaced LEDs:

May 25, 2010 2:44 PM

Hello moderater Rudolph,

I am curious about this statement

"For anyone who has had their beacon apart and it is now only showing up as "beacon 0" in the Rovio UI it is possible (likely?) that the little "fingers" of the channel-changing ring have bent and are no longer touching their contacts (seen in photo 2 above). "

I am trying to go the other way by making a beacon 0 show as a 1 thru 9.

The switching contacts on the board seem logical but when I short the contacts to simulate switching the IR code is still always read as "0".

But logic tells me that if a 1 thru 9 can be read as a 0 then a 0 can be read as a 1 thru 9.

I have an extra base beacon board (photo above) that I have wired to battery power for use in a a hallway with no outlets, but a redundant "0" signal just confuses the robot.

Anybody have any thoughts?


May 25, 2010 6:18 PM

I would have imagined that shorting the contacts as you described should have done it. I don't remember much about the internals of the beacons, it's been quite a while since I last had mine open.

I guess it's conceivable that the dock beacon may have different programming that does not make use of the channel-changer. Seems semi-unlikely though.

It may take me a bit to get to it, but I'll try to dig out one of my beacons and see if the adjuster ring is anything more than just a shorting jumper (like maybe a resistor or something).

Watch out, don't step in the anthropomorphization.

May 25, 2010 11:19 PM


This is a fun project.

"I guess it's conceivable that the dock beacon may have different programming that does not make use of the channel-changer. Seems semi-unlikely though."

I agree. intuition tells me the difference is physical, thru switching.

A visual camparison of the two boards (your beacon 1-9 and my beacon 0) shows the absence of R39 and R40 on your board whereas on my board the resistors are in place.

See photo below:

I think those two resistors are producing a permanent "0" regardless of shorting switch contacts.


May 25, 2010 11:45 PM

Just to clarify, original post was by milw, with photos by both milw and Nocturnal.

If you've got the facilities to re-solder those tiny resistors it may be worth trying removing them to see what happens. It might be sufficient to desolder just one side of each resistor and lift it a hair to see if the channel changer starts working.

Is that a snap circuits power brick you're using?

Watch out, don't step in the anthropomorphization.

May 26, 2010 12:45 PM updated: May 26, 2010 2:44 PM

Ooops, i thought the pic was yours.

I am reading the original threads closer. I see one pic from milw showing a beacon board with a dipswitch installed.

Very interesting.

Schematics would be nice. It is tricky tracing micro-circuitry. Macro-photography helps.

I think you may be right about removing resistors.

Here is my logic:

Looking at the boards I see 8 switching contacts yet the beacon has 9 settings.

So on a beacon board w/out R39 and R41 the default/open switch setting is Nav 1 while the 8 switch contacts produce Nav 2 thru 9.

On a board w/ R39 and R41 the default/open setting is Nav 0 and the circuitry of R39 and R41 prevent any of the switching contacts from functioning.

Yes, snap circuit power brick.

Thanks for input.



Further inspection shows my board lacks R42 whereas the comparison board had R42.

Jumpers J1,J2,J3, and J4 would seem to correspond w/ R39 thru r42.

I think some delicate probing can crack this nut.

August 6, 2010 8:21 PM

Anyone know where to purchase some TrueTrack Beacons in the US? If not, I'm wondering if there's a way to make some. Seems fairly simple enough, 2 IR LEDs, and an oscillating circuit to match whatever beacon number you want. It'd probably be simpler to make a non-switching circuit; one beacon per channel...

Or does anyone know if the Rovio is being discontinued? There doesn't seem to be much support from WowWee. My battery was crap right out of the box and I've still not gotten a response from them.

October 20, 2010 11:55 AM updated: October 20, 2010 12:10 PM

earlier today I was trying to replace the charging base TrueTrack beacon unit with one from an auxiliary beacon, found the "0" and "1" problem, and reached exactly the same conclusions as robopizza.

Now, my question is: has anyone tried to short-circuit J1 and J4? I can't really understand if the 100-ohm resistor is used just because it is less expensive than a jumper, or if there is a reason for current limiting.

And, are both needed to get the beacon to emit the "0" signal? I can't quite understand the logic of the whole matter. The three jumpers are marked "D0", "D1" and "D2" as if they would represent a binary number, but I can't find a relationship with the number read by the Rovio.

Any ideas most warmly welcome...

December 16, 2010 11:39 PM

Hey guys, the Rovio I purchased used yesterday doesn't see any NAV. It looks like the IR LEDs are not turning on. Are they always supposed to be on when the Dock is powered or only under certain conditions?

December 20, 2010 6:25 PM

Not sure if anyone reads this thread anymore but I just wanted to say thanks to the original authors of this article... I replaced both IR Diodes this weekend and revived the Rovio dock!

My only follow-up question has to do with about 1/3 of the time Rovio tries to drive on the dock left of where he should and does not get over the charging points. Usually Rovio goes forward, right, and than back again for a successful dock, but once in a while it's a no-go. Any tips on what could be making Rovio come in too much from the left? Is it possible that the IR beams are shining too far to the left of the dock? I would think that at that point he'd be using the Diode that's on the arch.

Again, many thanks to the thread authors and follow-up posts.

December 4, 2011 1:24 PM

Dear milw

I'm a new member of this ROBO community and I have read your very interesting arcicle
"Inside the WowWee Rovio TrueTrack Beacon".

I have a 50 Hz rovio and two 60 Hz TrueTrack Room Beacon. This two frequencies doesn't match so I can't use it together.

In your article, you have given the advise to simply remove resistor R42 to change the
50 Hz version to the 60 Hz version.

In my case, it is a little bit more complicated, because I need to switch from 60 Hz to
50 Hz, which means, to succed in this case, I must know the value of the resistor R42 first before I can buy an adequate SMD-resistor to insert it on the print.

May I ask you if you know the value of this resistor R42 to get a 50 Hz version?

Many thanks for your feedback and best regards


December 4, 2011 2:06 PM

hm I'll have to look back on my converstions with Nocturnal, he had a 50 Hz system and took better photos so it was possible to read the label on his resistors. I'll see what I can dig up and post here the results...

Discussion:    Add a Comment | Back to Top | Comments 1-15 of 31 | Latest Comment | 1 2 3 Next »

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