CoNSpiracy

PF lights and "switch direction"

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Per default, if I connect PF lights to a Lego PF battery box, the lights will shine no matter which "direction" is selected on the battery box (forward or backwards). The same applies if I insert a PF control switch (8869) in between the PF ligths and the battery box and change the "direction" using the control switch.

Is there a way to make the PF lights work only with one of the directions?

Forgive my ignorance and lack of electric knowledge, but would it work to cut one of the two middle wires (C1 or C2) in the PF lights cable (between the PF connector and the black brick)? Or would it just result in the PF lights not working at all?

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Posted (edited)

If you’re only using the battery box to power the lights you could use a 87513 AAA box as it’s switch is simply on and off.

Edited by grum64

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8 minutes ago, grum64 said:

If you’re only using the battery box to power the lights you could use a 87513 AAA box as it’s switch is simply on and off.

Yes, but I want to make it so that if the "direction" on the battery box (or control switch 8869) is set to forward then the lights are turned on when the power is turned on, and when the direction is set to backwards then the lights are not turned on when the power is turned on.

 

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1 hour ago, CoNSpiracy said:

Forgive my ignorance and lack of electric knowledge, but would it work to cut one of the two middle wires (C1 or C2) in the PF lights cable (between the PF connector and the black brick)? Or would it just result in the PF lights not working at all?

The LEDS are powered from C1/C2 through a rectifier bridge located in the middle brick. This rectifier causes the LEDs shine regardless of polarity. Cutting c1/c2 woud result in lights not working at all. For more details, see https://philohome.com/pf/pflights.htm

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Just now, Philo said:

The LEDS are powered from C1/C2 through a rectifier bridge located in the middle brick. This rectifier causes the LEDs shine regardless of polarity. Cutting c1/c2 woud result in lights not working at all. For more details, see https://philohome.com/pf/pflights.htm

Thanks. So that would be the "D1 Diode Bridge" shown in the picture of the print board inside the middle brick (as per the homepage you linked to)? Could I achieve the functionality I am looking for by simply removing one of the connections on the print board?

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25 minutes ago, CoNSpiracy said:

Could I achieve the functionality I am looking for by simply removing one of the connections on the print board?

Removing is not enough, you have to do some soldering. This should achieve what you want:
pf8870dia2.gif

And this could be interesting too (one LED shining in one direction, the other in reverse polarity:

pf8870dia1.gif

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1 hour ago, CoNSpiracy said:

Yes, but I want to make it so that if the "direction" on the battery box (or control switch 8869) is set to forward then the lights are turned on when the power is turned on, and when the direction is set to backwards then the lights are not turned on when the power is turned on.

 

Oh...

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7 hours ago, CoNSpiracy said:

Yes, but I want to make it so that if the "direction" on the battery box (or control switch 8869) is set to forward then the lights are turned on when the power is turned on, and when the direction is set to backwards then the lights are not turned on when the power is turned on.

Sounds like a great possibility for some 3-rd party parts with PF sockets on the both sides (like 2*2*1 brick) with some "logic" inside:

  • the brick with a "positive" diode: it opens the "power" only when the "control" (control switch, battery block, etc.) is in "enabled-positive" position;
  • the brick with a "negative" diode: the same but fully opposite;
  • the brick that swaps the power and control channels; Can't say what could be achieved with that right now but may be very promising

So, we won't have to cut or tin the PF wires or LEDs but got some nice functions and a kind of "electricity bricks" building again. Imagine the stack of "positive" and "flashing" blocks? Your vehicle is blinking with flashing warning lamps when backing up. Or indicates the turning direction... That would be fantastic. 

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16 hours ago, Philo said:

Removing is not enough, you have to do some soldering.

Thanks for explaining and taking the time to make the diagram. I am afraid it is beyond my limited electrical and soldering skills so I will not dare to move further down that avenue :blush:

 

9 hours ago, Void_S said:

Sounds like a great possibility for some 3-rd party parts with PF sockets on the both sides (like 2*2*1 brick) with some "logic" inside:

  • the brick with a "positive" diode: it opens the "power" only when the "control" (control switch, battery block, etc.) is in "enabled-positive" position;
  • the brick with a "negative" diode: the same but fully opposite;
  • the brick that swaps the power and control channels; Can't say what could be achieved with that right now but may be very promising

So, we won't have to cut or tin the PF wires or LEDs but got some nice functions and a kind of "electricity bricks" building again. Imagine the stack of "positive" and "flashing" blocks? Your vehicle is blinking with flashing warning lamps when backing up. Or indicates the turning direction... That would be fantastic. 

Yes it would! Another other example of great use of such PF "logic" brick you describe would be when motorizing locomotives, which are designed to run both ways (e.g. the one from set 7939). Here it would be great to have front lights turned on only in the direction the locomotive is running.

With 3D printing having become mainstream in recent years I am wondering why there are not more (or any?) third party products which link together with PF using the PF sockets. I am of course aware of the larger control units such as SBrick, but I am thinking about more simple products such as the one you describe. However, since Lego is now replacing PF with Powered Up, I guess third party companies won't have much focus on developing add-on stuff for PF in the future, either.

I am currently making a big city layout including a train track, where I want to light up the houses in the city. As I am making the city in modules which are meant to be dismantled quite often and transported/stored separately, I need to make sure that the wires for the lights can be easily disconnected and connected again. For this purpose, I find all the third party lighting products much too vulnerable with their small connections. I have broken quite a few of them when testing the concepts. So I have ended up with using Lego PF lights and PF extension wires, in order to have the easy click connections with the PF sockets. However, this is quite costly as I want to light up quite a few houses. Also, because I don't like the bright white colour of the PF lights I have had to cut off the LEDs (and transclear plastic housings) and soldered warm white LEDs onto the wires instead... So a lot of hassle just because no third party products have a sufficiently robust (in my view) connection system.

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I use Dupont connectors and barrel plugs.  I can't bring myself to cut a perfectly good PF cable.   I've 3D printed PF connectors found on Thingiverse.com.  it took a few tries to get the size perfect. It's a bit of work to wire them too.

 

 

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You can achieve what you want (lights on when in forward direction, off when in reverse) by mechanically connecting a motor with a clutch or other slipping mechanism to the switch that controls the lights, and physically blocking the travel of the switch in one direction. The switch that controls the motor is then the switch that you use to control the lights.

But I don't quite see why that is needed for static lighting of houses in a city scene?? Could you not just use a separate circuit and restrict yourself to using only forward/off for the lights?

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11 hours ago, Captainowie said:

You can achieve what you want (lights on when in forward direction, off when in reverse) by mechanically connecting a motor with a clutch or other slipping mechanism to the switch that controls the lights, and physically blocking the travel of the switch in one direction. The switch that controls the motor is then the switch that you use to control the lights.

Thanks, I will give this idea some further thought. It would be quite heavy on PF components, though, since I need one set of PF lights to turn on in forward direction and another set of lights turn on in reverse.

 

11 hours ago, Captainowie said:

But I don't quite see why that is needed for static lighting of houses in a city scene?? Could you not just use a separate circuit and restrict yourself to using only forward/off for the lights?

Thís particular feature is not for the houses. It is for a signal system for the train tracks in the layout, where I want to have a PF motor controlling a track switch and in connection therewith have green and right red lights changing whenever the track switch direction is changed by the motor.

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@Captainowie I have been thinking more about the solution you suggested.

I could start off with controlling the track switch with a PF motor, like in this video: HOWTO LEGO Train Motorized Points Switch. I would then need to have the drive / technic axle coming out the motor to continue on to two different PF control switches (8869). I guess I could achieve this by putting a gear on the technic axle coming from the motor, in order to connect with two new gears, each with a technic axle going into a respective PF control switch.

But how to physically block the travel of the two switches in one direction each (as you suggested) in a way where the motor is not put under too much constraint and where the other “leg” of the mechanism would still rotate / make a change on the relevant switch?

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I have done exactly what you have described, for a trafficator. For one of my projects, I used mechanical turn signals, and I used a 2 switch assembly that sounds like what you need. You can see it in this .lxf file:https://bricksafe.com/files/Saberwing007/ideas/trafficator.lxf

 

This has more to it, but it should be fairly easy to see what I did. I'd use a clutch gear to allow this to not impede the switching track.

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2 hours ago, Saberwing40k said:

I have done exactly what you have described, for a trafficator. For one of my projects, I used mechanical turn signals, and I used a 2 switch assembly that sounds like what you need. You can see it in this .lxf file:https://bricksafe.com/files/Saberwing007/ideas/trafficator.lxf

 

This has more to it, but it should be fairly easy to see what I did. I'd use a clutch gear to allow this to not impede the switching track.

Thanks for sharing this.

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There is a whole section on how to use PF switches for various functions  in Sariel's Technic Builders Guide.

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32 minutes ago, Doug72 said:

There is a whole section on how to use PF switches for various functions  in Sariel's Technic Builders Guide.

Excellent, thanks! I have the book at home and will go check it out.

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4 minutes ago, CoNSpiracy said:

Excellent, thanks! I have the book at home and will go check it out.

Second Edition pages:- 32 /104 / 106 to 109

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On 3/10/2020 at 3:40 AM, CoNSpiracy said:

But how to physically block the travel of the two switches in one direction each (as you suggested) in a way where the motor is not put under too much constraint and where the other “leg” of the mechanism would still rotate / make a change on the relevant switch?

 

On 3/10/2020 at 11:30 PM, CoNSpiracy said:

Excellent, thanks! I have the book at home and will go check it out.

Yes, that's the resource you'll want. The best part is, when you have two switches like you're suggesting, you can hard-link them together such that they can only travel off/forward to reverse/off. Then all you need to do is have the right amount of slippage on the motor, whether that's from a white clutch gear, or a regular gear on a friction pin, or rubber belts, or whatever!

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1 hour ago, Captainowie said:

Yes, that's the resource you'll want. The best part is, when you have two switches like you're suggesting, you can hard-link them together such that they can only travel off/forward to reverse/off. Then all you need to do is have the right amount of slippage on the motor, whether that's from a white clutch gear, or a regular gear on a friction pin, or rubber belts, or whatever!

Yes, indeed, the Technic Builders Guide 2nd ed. turned out to have an example which is pretty much spot on to what I want to do. With figures 9-23, 9-29 and 9-30 in the book, I am sure I can make it work like I want.

Thanks again to all of you for your support. Much appreciated and exactly what I was wishing for!

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