PF Lights on 9V Motor

[Lazarus]

Hello All.

this has likly been asked before but if i could get an easy yay or nay :-P

All my PF trains have all been converted to 9v, i bought the locos of bricklink with out PF to save the cash. I prefer 9v for myself, the battrys just put me off. One day i might change over but for now i am happy.

First

i want to use 61930c01 Black Electric, Light Unit Power Functions with Black PF Connector Lead

Can this just be plugged onto the top of the 9v motor and away we go.

Is is not all just 9v.

Also can i do this. i may need to reiwre the PF terminal to make it the same as the 9v one.

Idea is to get the 9v power from the old 9v motor and make it run. This is just a cheaper idead to run more than one motor.

[Ashi Valkoinen]

It won't work, you need a conversion cable between the PF and 9V train motor (conversion cables have one PF-end, and one 9V/PF end), the 9V/PF-end have to be placed on the 9V motor, the other end connected to the PF-train motor.

For lights you need the conversion cable, too. See this video, lights working from 9V motor:

Edited November 13, 2012 by Ashi Valkoinen

[Lazarus]

would that cable work for a 2nd motor also. i know you can buy them.

[Duq]

That's a nice video of your trains but it doesn't show how the PF lights are connected to a 9V motor. For all we know your train may be running on PF.

The 9V system of course had it's own lights. Have a look for them on Bricklink.

[Lazarus]

i was looking at put light in my horizon express and looks like the old 9v might be a pain to get in, in saying that we wont have that till jan.

But i want to put in a 2nd motor into my red passenger train as it have 4 cars it does stugle with a single 9v, i could by more but there cost is alot at the moment so i am trying to cut cash

[zephyr1934]

I have powered PF lights from a 9v motor. The only problem I've had is that the LEDs flicker off at low speeds (and thus, low voltage). I haven't tried powering a PF motor from a 9v, but I believe many folks have. It will certainly require the conversion cable to take power off of the 9v motor, but on the PF end of it you could then attach both the lights and the PF motor. You may have to turn the PF motor backwards or use a polarity switch though.

[wondermonkey]

Yep. PF lights work great off the 9V motor with a conversion cable. The PF lights seem to be a little more blue than the old 9V light but you can't beat the price and you get 2 lights. I am happy with them on my 9V powered Emerald Night.

[WesternOutlaw]

This question(s) really belongs in our Question Topic but as there is a discussion, I've left it here in the forum.

[Lazarus]

"I haven't tried powering a PF motor from a 9v, but I believe many folks have"

this was what i was after also. Sweet time to buy up some bits. as the PF motor about under 50% cheaper than the 9v my 4 9v motors can now become 8 with out a heavy cost.

[*thomas*]

I know I'm reviving an old thread, but seems worthless to start a new one.

Yesterday I tried to power PF light from an RC battery box. I made my own wire using 9V on one end and PF on the other only using the 2 inner connections on the PF cable (C1 and C2 in the picture). The lights work, but only when the train goes in one direction (so when the receiver switches polarity, the lights turn off).

How can I make the lights stay on when the train goes both ways? Or do I need the specific LEGO cable? 

 

[Phil B]

Just a theory, but since the lights are LED lights, maybe the polarity switch that happens on C1/C2 when you change directions causes the LED to block? After all, it is a diode ... You might need to put a half or full H-bridge in between to always keep the same polarity.

[JWBDolphins]

I would agree with Phil B.  LEGO LEDs have a Bridge Rectifier built into the PF connector - basically a diamond of diodes that makes sure DC current only flows to their LEDs in the correct polarity regardless the polarity coming into it.  If you're using your own LEDs or removed the LEGO LED PF connector, it should be easy enough to add your own Bridge Rectifier so no matter the polarity of C1 and C2 the LED should light.

Edited February 18, 2024 by JWBDolphins
addition

[LEGO Train 12 Volts]

As @JWBDolphins says the diode bridge is the correct solution, easy and economical:

 

[*thomas*]

Thanks for the input, guys. I was afraid it wouldn't be as easy as choosing different connections.

The diode bridge is a good idea, but I'm building this train for my 5 year old son so it will add complexity and fragility (hence why I choose to use an old RC base/remote).

I think I will add a PF battery box and feed the LEDs with constant current. 

[zephyr1934]

Why not use the 9v light brick?

Or go crazy disco and add flashing in one direction

[Toastie]

5 hours ago, zephyr1934 said:

Why not use the 9v light brick?

Oh yes ... here is to TAE (no Nobel Prize for him, but he made it work for everyone, and that is much more important ). Any tiny tungsten wire will light up either way; that is the simplest and most efficient solution. I love it!

If you want to go LED - the bridge rectifier is your friend. Will drop the voltage by about 1.2V, but who cares at 9V supply voltage.

Best,
Thorsten

 

Edited February 18, 2024 by Toastie

[*thomas*]

The reason I'm not using a 9 volt light brick is because I can't make it fit into the front of the 7745 train... 

[ciphernaut]

Another option is to wire a red and a white led in opposite polarity.  So when the train is running in the other direction the other color should come on.

[zephyr1934]

On 2/21/2024 at 5:36 PM, *thomas* said:

The reason I'm not using a 9 volt light brick is because I can't make it fit into the front of the 7745 train... 

You could use the fiber optic cables to get the light where you need it.

They do make bi-color LED's that change color when the polarity is reversed (actually two LED's in one case, with opposite polarity), that would eliminate the need for the bridge and give you a color changing LED to boot.