Power Functions trouble

[simonwillems]

Hello there,

As we all know Lego brought the Power Functions, as used in the big 8275 bulldozer, on the market as servicepacks on Shop at Home, so now you can buy all components separately (they also increased the price shortly after, but that's a different story...).

All the components used in the buldozer are there, but also an extension wire to connect the old 9 volt system to the new power functions system.

Recently I bought some power functions: motor, receivers, remote and extension wires. I already had the old system which uses this kind of battery box and I thought that with the new extension wires one could use this (to save space inside the MOC) to power the system. Consequently I did not buy a new batterybox.

Here's the problem: the motor works fine with the extensionwire leading directly to the old battery box without using the receivers, but the receivers do not work when powered by the old batterybox!. I thought it was a production msitake and called Lego, but they confirmed that when you want to use the receivers you'll need to buy a new power functions batterybox. It was a design flaw they only recently discovered when playing around with the new system in the factory.

So those of you preparing to buy the new power functions system, be sure to include a batterybox, or you'll end up like me.... placing an extra order to get one afterwards. :-/

Any questions or comments are welcome, of course.

[Siegfried]

Thanks for posting this, but I must admit that I'm not too surprised. The recievers work the same regardless of the polarity switch position so I figured they were wired differently. You were not to know however.

(As for the price change, what can I say but >:-( . I did a S@H order while they were at the better price and I am kicking myself now.)

[Lasse D]

Ouch. That is one of the design flaws that I feared. It also means that you cannot power an IR-receiver using an old 9V power supply like control center II or the widely used train pult!

I hope LEGO will issue a recall or at least change the IR-receiver so that it works as it should. And when they are at it, they might as well make use of that extra bit in the protocol for 8 channels instead of 4.

[simonwillems]

Ouch. That is one of the design flaws that I feared. It also means that you cannot power an IR-receiver using an old 9V power supply like control center II or the widely used train pult!

That's right, I tried them all, train transformer, technic-6-batterybox. Well, I don't have the control center but it won't work either...

It could have been nice, hiding the small 9 volt holder somewhere in a small car. :-(

[Siegfried]

And when they are at it, they might as well make use of that extra bit in the protocol for 8 channels instead of 4.

I don't think they will. From what I have heard there is too much interference as it is. I read somewhere (I can look if you want) of some people who tried to do robot soccer with four players but found only two worked well. :-/

[Holodoc]

Ouch. That is one of the design flaws that I feared. It also means that you cannot power an IR-receiver using an old 9V power supply like control center II or the widely used train pult!

???

Please help me: I don

[simonwillems]

???

Please help me: I don

[Captain Green Hair]

Thanks for pointing that out Simon, i'm planning on some of those for the switches too *sweet*

[Lasse D]

I have an idea. Instead of short circuiting certain pins in order to avoid this problem, what about adding an empty PF-battery box to the circuit?

Old 9V -> PF-cable -> Empty PF battery box (turned on) -> PF IR-receiver.

I have forgotten my own PF-cables, so can anyone try this out?

[simonwillems]

Old 9V -> PF-cable -> Empty PF battery box (turned on) -> PF IR-receiver.

I have forgotten my own PF-cables, so can anyone try this out?

That might work, but it goes past the idea of saving space while using the old 9 volt battery box, because now there are two battery boxes... In that case it's better to just use the new one.

What I forgot to mention is that is is possible to make the system work with the old battery box when you connect the batterybox with one of the outputs of the receiver instead of using the cable attached to it. This only leaves you with one output left to control remotely instead of two. Not really that handy, but if you only want to control one function it might be sufficient.

[Lasse D]

I see the space problem, but I'm more interested in using power from outlets instead of batteries. My plan is to introduce user interaction with the PF system to layouts, such as GBC, but also in ordinary train layouts.

To let the audience control small (and secured) parts of a GBC-layout might make them even more interesting.

I still have to work on the "how to give the audience PF-controllers" and "have all in on the idea"-parts :-)

[EyesOnly]

That sounds like i great idea. I haven't gotten any converters yet so i can't test it.

[Brickthus]

The lead mod required to power a PF IR receiver from a 9V source is the bottom left one in this diagram.

A good way to do it is to use single 12V plugs on the cut wires, so you can swap the connections at will.

Mark

[Parax]

I think Lego ougt to have released a 2x2 converter block wihout a wire...

PF on top and old 9v on the bottom and just done normal cables...

they could have done:

a red block 9v -> PF 9v&0v lines (power into PF system)

a blue block 9v -> PF C1&C2 lines (motor convertor block)

P.

Edited February 8, 2008 by Parax

[Lasse D]

That sounds like i great idea. I haven't gotten any converters yet so i can't test it.

I have finally been able to test it and the results are...

It works! *y*

You have to turn the battery box n to the "right" side and voil

[Lasse D]

LeJos has finally added support for the IRLink in the latest SVN, so I guess it will come in the next beta (or RC?) release.

I have added support for the single output PWN mode, so you can control the speed of each motor individually as well - (without timeouts!)

Since so few people have seen the power regulation of PF, I have made a small video of a test.

The IR-receiver is powered using the battery box trick mentioned above and the NXT simple outputs the 16 PWN-modes in sequence:

Float, forward 1-7, stop, backward 7-1.

[Freddie]

Float, forward 1-7, stop, backward 7-1.

Sorry for my n00biness, but exactly what does "Float" mean here? The other three are obvious, but "float" tells me nothing - I'm curious because the new trains are going to use these sequences when they're released next year, and I want to know what sort of effect "float" will have on the movement of the train.

Edit: Also, in the video, I'm hearing a beep-like sound whenever the motor slow down to a halt or when it starts. I know the current RC-trains makes this noise as well, so I'm guessing this noise is the motor starting/stopping?

Edited June 14, 2008 by Freddie

[Lasse D]

N00biness? Not really. It is because of the designs of the motors (4 pins of input) where you can set the power in a special way so they block/brake. If they are stopped, but not blocked, they "float" - just like a motor without power. This is most noticeable on the XL- or NXT-motors because they get extremely hard to turn.

Old motors with only two lines of input can't block, but you can "change the polarity" to get a similar braking force.

The beeping sound is there because the power is very low (notice it's only 2 on the regulator). You can avoid this by applying more power

I am only using official LEGO pieces, so the PF trains will definitely be speed regulated - they already are if you use the current PF-parts!