Adding motors, lights and sensors to a single hub

[Desvejk]

I have a question about running additional powered up items such as lights, sensors and motors from a hub.

The small hub has two ports which is quite limited.

Would it be possible to splice two motors together by joining of “piggybacking” the wires together? Could the same be done with lights and sensors, or lights and motors?

[Lok24]

yes, wth the train motor and the old lights that should be possible.

[Desvejk]

Thanks for your answer. When you say old lights, do you mean using PF lights spliced to the correct wire on a Powered Up Cable?

[Lok24]

No, I meant 88005, but the PF work as well.

[Desvejk]

Thanks again. Could you join two motors together this way?

[JopieK]

It should be possible, but be careful to not draw too much current per channel from the driver IC I would say.

[dr_spock]

Running two PF train motors off a single port on PU hub seems to be ok so far...  Note: do so at your own risk.

[Desvejk]

1 hour ago, dr_spock said:

Running two PF train motors off a single port on PU hub seems to be ok so far...  Note: do so at your own risk.

Thanks so much. This is a real possibility. How did you make the PU plug for the hub?

[Johnny1360]

Sure you can but I think the gains would be negligible as the same amount of theoretical power is now going to two motors rather than one. It would however help with traction, if that is an issue.

[Desvejk]

1 hour ago, Johnny1360 said:

Sure you can but I think the gains would be negligible as the same amount of theoretical power is now going to two motors rather than one. It would however help with traction, if that is an issue.

I think you are probably correct with the motors. 

I’m very interested in doing this with a PF lighting kit and joining it to a PU motor on the same port. The other port is used with a sensor. 

Could this work?

[XG BC]

7 hours ago, Johnny1360 said:

Sure you can but I think the gains would be negligible as the same amount of theoretical power is now going to two motors rather than one. It would however help with traction, if that is an issue.

not if one motor only uses like half the hubs capabilitys on the given port. if you use two you are then going to use more of it giving you more output power.

[dr_spock]

15 hours ago, Desvejk said:

Thanks so much. This is a real possibility. How did you make the PU plug for the hub?

I had to teach myself some basic CAD and 3D printing.  There are compatible plugs on places like AliExpress.

6 hours ago, Desvejk said:

I think you are probably correct with the motors. 

I’m very interested in doing this with a PF lighting kit and joining it to a PU motor on the same port. The other port is used with a sensor. 

Could this work?

It would be like stacking PF plugs in the PF system.  The LEDs would be subjected to the same PWM output as the motor.  The LED brightness would be affected by that.

[Toastie]

10 hours ago, Johnny1360 said:

as the same amount of theoretical power is now going to two motors rather than one

As @XG BC said, DC motors suck-up juice as they see fit (depending on load exerted and rpm you want) - Philos motor page is a wonderful reference for that:

https://www.philohome.com/motors/motorcomp.htm . PUp train motor is listed as well and someone here knows what the PUp output driver can deliver, I can't remember where that information is hiding ...

2 hours ago, dr_spock said:

The LED brightness would be affected

That is true. I had the impression though that even at low PWM settings, the LEDs almost reach "full" brightness - which is in stark contrast to the 9V incandescent lights - they pretty much give a close light intensity vs PWM setting response (well, of course they do).

Best
Thorsten

[Johnny1360]

37 minutes ago, Toastie said:

As @XG BC said, DC motors suck-up juice as they see fit (depending on load exerted and rpm you want) - Philos motor page is a wonderful reference for that:

https://www.philohome.com/motors/motorcomp.htm . PUp train motor is listed as well and someone here knows what the PUp output driver can deliver, I can't remember where that information is hiding ...

That is true. I had the impression though that even at low PWM settings, the LEDs almost reach "full" brightness - which is in stark contrast to the 9V incandescent lights - they pretty much give a close light intensity vs PWM setting response (well, of course they do).

Best
Thorsten

I guess what I am trying to say is, if you run two motors on the same amount of current as one motor was getting, you gain little as you only get out what you put in, the same amount of power is just going to two motors instead of one. Now if you increase the current you will get a noticable performance gain.

[Toastie]

16 minutes ago, Johnny1360 said:

Now if you increase the current you will get a noticable performance gain.

That is true!

But: The motors will >draw< current (you can't >increase< the current by choice, in contrast to voltage, you just can >limit< the current) depending on their demand. Lowest current drawn is when they run without load (other than their own demand to spin the rotor). When you increase their load = adding mechanical resistance to their free spinning resistance, they'll draw more current. When the supply is capable of supplying more current, that a "fully loaded" motor draws (which is simply the resistive limit of all current going through the coil and dissipates as heat, as no magnetic field is altered anymore and all the beautiful Maxwell equations are also not useful anymore ;)), the motor usually simply burns out after some time.

When the two motors are not stalled, but run with some "decent" load, and the power source is capable of delivering that current, the you really gain performance or tractive power. As one example: The PF receiver, particularly the V2 type, can easily burn out 2 PF train motors, as the current that thing can drive is more than a stalled motor draws.

And all that is limited by the maximum current delivered by the battery/power supply. I run my trains on a primary 15V 10A power supply, which is regulated to 9V, 1A max on each train, which is feeding the PUp/PF/RCX controllers residing on each train. And they drive the motors. Train motor are not that demanding, so I run 2 of these off from one PF receiver output. 

I don't recall the (max.) current limitation on the PUp >outputs<, but as said, somebody wrote in this forum what type of drivers, presumable H-bridge types, the PUp hubs use.

[Lok24]

It's an LB1836, same as in PF V1

PF V2 had a DRV8833

13 hours ago, Toastie said:

And all that is limited by the maximum current delivered by the battery/power supply.

No, at least the technic hub has a current limiting software, as fas as I know.

[Desvejk]

Thanks for all the comments. I'll have to digest all of this and come back with a more specific question.

[Toastie]

9 hours ago, Lok24 said:

It's an LB1836, same as in PF V1

PF V2 had a DRV8833

@Lok24 Thank you very much, Werner, highly appreciated! Need to write that down somewhere.

Also thank you for that software limiter, had no clue. Good to know. Do you happen to know when that kicks in?

Best,
Thorsten