darkith

Just because I think a lot of people don't realize that there's more to these battle systems than the frequency of the IR signal....for those who are curious. Everyone else can just tune me out.

Here's a primer for (in)compatibility:
>There's the "color" of the infrared light. The IR LEDs have a peak at around 940nanometers, with a bell curve on either side. If the color isn't about right, the light from the LED won't trigger the sensor, or will only work at very close range. Close works, but not perfectly, and could result in some systems having different ranges with each other.

>Then there's the frequency of the IR carrier signal, in our case, it's 38 khz. An analogy of this would be the frequency of a radio station (e.g. 99.5 mhz)

>There's the signal format. In most cases, we think of the signal as pure binary: "light on" == 1, "light off" == 0. But in some systems, you might use something like Manchester encoding, where you use the edge of the transition "light off, then light on" == 1, and "light on, then light off" == 0. An analogy of this would be AM radio versus FM radio.

>There's also the signalling rate, or how often the signal can change. Think of this as the speed at which a person is talking on the radio.

>Then there's the actual signal pattern...the code that's encoded into the signal format, then onto the carrier frequency. The pattern can be an arbitrary length of bits, something like "100010100001011100". The signal pattern represented by 0s and 1s can then converted into "lights on" and "lights off" (although as mentioned above, it may not be trivial). An analogy of this would be the language on the radio...it's using the same sounds, but you can only interpret the language you already know.

So...there's a lot more than just "matching the frequency". In our case, the TBU, DBU, and (apparently) HBU all use the same carrier frequency (38khz) for receiving (and therefore the same carrier frequency for sending). They all probably use the same "color" of IR (940 nm) or are close enough (though we need to verify and range test the HBU and HL IR LED). So, it's not surprising that the HBU, DBU, and TBU can be swapped around (I specifically designed the DBU to be TBU compatible of course).

The *rest* of the details (the signal format, bitrate, and signal pattern) are all determined and processed by the computers in the Tamiya MF, DBC, and HL RX-18 units. This is where the real magic happens, and it *all* has to match for things to work. Popping a TBU or DBU on top of an RX-18 would make the infrared light reception work, but the signal processing remains the same, so it doesn't recognize the signal.

So, when it comes to making the HL RX-18 unit battle with Tamiya MF and DBC units, that would either require Heng Long to recode the HL RX-18 unit, or for an inline converter to convert the inbound and outbound signals. And that's assuming that the HL IR LED and HBU are using 38khz and 940nm.
If the sensor was using 40khz and/or the LED was 890nm, even if they recoded the RX-18, it would only work at short range against other brands.
If the sensor and LED are using 38khz and 940nm, it shouldn't be too hard to recode the RX-18, but they:
A: may not want to make the already released Stug incompatible with newer tanks (tho if they were really smart they'd have it fire both signals and recognize both signals, but it still might be hard to distinguish the old from the new)
B: may already have produced a crapload of chips programmed with the incompatible code, and not want to throw those away (if they didn't use easily re programmable processors, they probably wanted to make a large run to lower the individual chip cost)
C: may not care about the hobby-grade market (versus the high volume toy market)

Hope that helps a few people who might have been curious about the reasons for (in)compatibility. It really is a shame HL didn't do more research... perhaps they don't really care about the hardcore battling tankers, and prefer to target the RTF toy market like they have in the past. Then, they naturally want you to buy two of their tanks and not somebody else's.

Cheers,
David

Dugster

Thank you very much David, that was very informative!

YHR

Thanks for the detailed information David.

I imagine when you get yours you will be able to determine exactly what the staus of the HL system is, and the rest of us will hear from you???. Good news is that your DBC will interface with the RX 18 so hobby grade guys can use the new HL released on the battlefield if they buy the DBC, and the backyard battlers, will have nice low cost entry tanks, IR battle ready.

The thing that is really interesting that you brought up is the wavelength portion of this. Seems to me really serious tank battlers should be looking harder at the emitters, and trying to match range more with tank type.Ie a German Tiger, should have a greater range then a Sherman. From what you have told us here, a person could actually make that happen in the IR battlefield by specifiying what wavelength an emitter must be. IE a Tiger 940nm and a Sherman 890nm. This would give the tiger a longer range then the Sherman(Assuming that the detectors are all 940nm)

darkith

I'm just glad somebody was able to read it without falling asleep.




Alas, it's note quite that simple. The light of an IR LED is designed to peak at a specific wavelength, but the distribution on either side (generally bell-curve like) can vary in intensity and spread. So, one 890nm may have 10% power applied to 940nm, another may have 0, another 40%. Similarly, the IR sensors have band of varying sensitivity, which is different between models and manufacturers.

So, two different 890nm LEDs may have different results against the same 940nm sensor. Or, two different 940nm sensors would respond differently to the same 890nm LED.
And when I'm talking short range for a LED and sensor on different wavelengths, it could be as low as inches, if at all.
Off the cuff, I don't expect it would be reliable to be useful, especially if the audience was really serious tank battlers.

A while back, somebody experimented with using shields with very small holes to vary sensitivity, and they had some promising results. But I suspect the serious tankers might run into disagreements over hole measurements. Doing a little metalworking, I've realized that a drill bit doesn't drill the exact size hole you expect it will (they're not even technically round!), and when you're talking about holes <1-2mm, it's hard to measure accurately. Same thing would apply to transparent filters and density.
I think the only way to implement more advanced multi-class battling would be to redesign the signaling protocol to embed the class of tank (or gun type) that's firing into the signal as well as use different sensors for at least the front (glacis) and the other three sides (or use a unique sensor for each side). Naturally, you'd need a compatibility mode for battling with the standard protocol.
I think Elmod's CSI uses some of these ideas in their advanced mode. I've been tempted to see if some other battle system vendors want to collaborate (actually talked about it with Zardoz who created the Tankzone EGS, nothing happened tho), but I'd be concerned that getting too fancy would complicated the DBC/DBU too much for it's market point as a low-cost/bang-for-the-buck option. (Adding more code separate hit zones would require more PIC memory, IO pins, and a bigger PCB = more bucks). Simple seems to be working well.

D.

Ex_Pat_Tanker

If you were to account for the performance of the main gun, then not only is the emitter signal going to get horribly complicated (based on what is available today from Tamiya / HL / WSN plus the various 3rd party kits for them, I count over 15 different diameter/length combinations!) but you would also end up with people exclusively fielding King Tigers - nothing else would stand a chance!

YHR

Except 15 Shermans!!!!!!, But I agree, even simple causes problems for some club rules. I can only imagine what complicated would bring!!!!!!!

Ex_Pat_Tanker

Thats the problem - you'd have 2 guys playing "turkey shoot" with the KT's, 2 guys playing "Assasin" with Fireflies, and 8 guys playing "scarificial lamb" in 75mm M4A1's!!

bowlman

Hay Bill ive ordered the rx-18 and the HBU from rc command do the HBU come with cable to hook up to it and the rx-18 box plus connectors for the rx-18 box for upgrading another tank that had a rx-13 or rx-14 in it just asking and if not do you no were can get want to put in the HL Tiger 1 tank I have thats been gutted of all running gear and electonics .Also do you have the gun flash and the ir led also .

Thanks
Jimmy

blitzkrieg65

Read it wrong[:-]

darkith

So, I received my Stug from RCcommand on Thursday, and I'm quite impressed by it. Good detail, parts that aren't glued on, spare track pieces, etc. Not perfect, as the elevation on my tank gets stuck at the top and needs an ever-so-slight touch to get over the hump and cycle back down...probably an interfering wire of piece or molding flash somewhere.

Haven't had a lot of time to play with it yet, as my 1 year old daughter starts crying when I even pickup the tank when she's around. Have to work on that...maybe she prefers allied armor?
But I did record the IR signal into a learning remote so that I could experience the hit wiggle and death waggle for myself. Heh.
I also played back the IR signal to my oscilloscope and confirmed that Heng Long's signal is quite different from the Tamiya/DBC signal. The bit rate is way slower, the bit pattern is different, and there's a gap between repeats whereas the Tamiya signal is back-to-back for the full second.

Couple of other interesting observations:
The tank fires the IR signal even without the HBU plugged in.
The high pitch PWM noise from the ESC seems more noticable to me.
The flash and recoil are somewhat out of sync.
The tank seems a little zippier and quicker to super-spin, perhaps due to the FETs passing higher volts.

Hope to tear into it and take a poke around the RX18 board this weekend, maybe post instructions and pics on hooking up the DBC to this board.

Cheers,
David

blitzkrieg65

Excellent David, was wondering what you have found! Look forward to the rest of analysis, and you have an oscilloscope at home that is awesome!


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