Power Functions lights vs. different battery box voltage

[CoNSpiracy]

Hi All,

hoping that this is the right forum section, I have a question about PF lights (8870) and how they work with the different PF battery boxes.

It seems that the PF battery boxes deliver different outputs/voltages. The 88000 and 8881 battery boxes (each with 6x normal 1.5V AA batteries) deliver 9V, and with 6x rechargeable AA batteries they seem to deliver around 7.2V. The 8878 rechargeable battery box delivers 7.4V (I assume both with and without the 10VDC transformer (8887) plugged in?).

I assume the various PF motors would function differently depending on the voltage, but what about the PF lights? Would they be more dimmed / shine less with 7.2V/7.4V vs. 9V?

I don't own all of the various battery boxes, so I am not able to test it (and I am not very savvy in this area of physics!), so I hope some of you can answer this! Thanks in advance.

Edited February 25, 2020 by CoNSpiracy

[Void_S]

7 hours ago, CoNSpiracy said:

I assume the various PF motors would function differently depending on the voltage, but what about the PF lights? Would they be more dimmed / shine less with 7.2V/7.4V vs. 9V?

Yes, exactly!

I got 8 or 9 pairs of PF LEDs once (and used all of them together only in a single MOC but it's a different story) and I can fully say that yes, their "power" corelates with the battery voltage. I tested all of them with PF rechargeable box with the voltage control and they barely light at the lowest power to some kind of a normal work at the highest voltage for this battery 7.4V. Then, the full-size PF Technic Battery box - 9V, LEDs shine stronger. And the best result is with BuWizz's Ludicrous mode - it makes them shining a lot. Really, it was enough to drive the chassis in the dark room using only a single PF LEDs pair. Plus to that, I used them many hours in total and didn't observe any faulty.

Edited February 25, 2020 by Void_S

[CoNSpiracy]

Thanks for the reply. I see at the BuWizz homepage that the ludicrous mode runs at 11.2V.

I am currently doing a large city layout where I want to add PF lights to light up the interior of houses. I know that there are many third party lighting products that I could use, but I prefer the easy "brick-style" click system with the PF lights and PF extension cables instead of the often very small and somewhat fragile connectors used by for the third party products, as I will be making the layout as modules which will be separated and stored away from time to time.

Since I the lighting in houses is stationary, I do not need a battery function and would actually just prefer a steady power source plugged in the wall. So this is why I was considering the 8878 rechargeable battery box with the 10VDC transformer (8887) always plugged in, but if this only generates 7.4V and makes the PF lights shine less bright than with 9V, I need to do something else. Which could be modding the PF power supply to connect a PF connector directly to any 9V (or even up to 11V?) DC transformer, using a bit of wire cutting and soldering. I reckon I could do this as for example described in this article: https://www.instructables.com/id/Power-Functions-power-pack/. And since I would like a main switch (in Lego) to turn on/off the PF lights in the houses, I could even cut the wire and use the switch part from 8869 as suggested at the end of the article. Any thoughts on this (other than, yes, I know, this would mean modifying official Lego products which many of us don't like in the first place!)?

I wonder if the number of PF lights "daisy-chained" in the setup (with PF extension cables in between) will impact how bright the lights will shine? I reckon I will be adding around 20-30 pairs of PF lights altogether to the same circuit.

[Void_S]

I'm not into parts modifying, sorry, but as for 20-30 pairs of PF lights in a stack - it should have the minimal possible effect as their consumption is very small. Just one "con" here: such stack will be way huge.

Generally, I would recommend just some all-while Christmas tree LED lights. They are much more compact rather than monstrous construction, powered from the 220/110v socket (no batteries need to be regarded) and way cheaper.

[dr_spock]

You may have to be careful with using too high a voltage with the PF LEDs without changing the value of the built-in current limiting resistor.   Exceeding the LED max. current can be fatal to the LED.

I 3D printed some dummy AA batteries connect to a 9VDC wall adapter.  They could go into a 8881 AA PF battery box without modifications.  You can also make them from wood dowels, etc.

[CoNSpiracy]

3 hours ago, dr_spock said:

You may have to be careful with using too high a voltage with the PF LEDs without changing the value of the built-in current limiting resistor.   Exceeding the LED max. current can be fatal to the LED.

Ok, thanks for the heads up. Is the "built-in current limiting resistor" sitting in the PF light (the black brick, I assume then) or in the battery box? If it is in the PF light, then your setup with the 3D printed AA battery holders would also be vulnerable to a too high voltage, right?

I can see that the original Lego power adapter (8887) is 10V DC 700mA 3W. I am thinking about using a 9V DC 1000mA 12W power adapter, as I am not able to find one that exactly matches the original Lego one. Would this work?  

[Toastie]

1 hour ago, CoNSpiracy said:

I can see that the original Lego power adapter (8887) is 10V DC 700mA 3W. I am thinking about using a 9V DC 1000mA 12W power adapter, as I am not able to find one that exactly matches the original Lego one. Would this work?  

It will work. LEGO is the only company in the world who sells 10V DC power supplies - at ridiculously high prices.

9V works beautifully well - as 12 V does (running for years on my layout). Just make sure that when you get a (cheap) wall wart, as @dr_spock has suggested that the output is really 9/12 V. The cheaper they get the more "unregulated" they are - some of them do provide their nominal voltage only under nominal full load. The LEDs draw only very little current - and thus the applied wall wart output voltage may be way higher.

I'd invest a few bucks more for a regulated power supply.

Best
Thorsten 

[Void_S]

9 hours ago, Toastie said:

It will work. LEGO is the only company in the world who sells 10V DC power supplies - at ridiculously high prices.

I use a more cheaper universal supply with variable voltage settings (from 7 to 12v if I remember it properly) and it also works perfectly. Just mind the required voltage and current.

[Toastie]

18 minutes ago, Void_S said:

I use a more cheaper universal supply with variable voltage settings

Absolutely! The dial usually goes from 3.0V to 12V: 3 / 4.5 / 5 / 6 / 7.5 / 9 / 12V ... since these are voltages, devices presently use on Earth. The 10V LEGO wall wart is for devices >not< from Earth - >in addition< to LEGO devices, which run perfectly fine on either 9V or 12V

You can get a regulated 3 - 12V wall wart with a rating of about 0.5A for less than 10 bucks.

All the best
Thorsten 

[JaBaCaDaBra]

11 hours ago, Toastie said:

LEGO is the only company in the world who sells 10V DC power supplies

Ali sells them too.

[Toastie]

45 minutes ago, JaBaCaDaBra said:

Ali sells them too.

Is there anything that Ali does not sell?

Best
Thorsten

P.S.: Does anyone have a 10V wall wart from either LEGO or Ali? If so, is there a chance to measure the open-circuit voltage?

[CoNSpiracy]

4 hours ago, Toastie said:

You can get a regulated 3 - 12V wall wart with a rating of about 0.5A for less than 10 bucks.

I can see that the official Lego adapter (8887) is 700mA. Wouldn't it be a problem to go lower than that?

[Toastie]

9 minutes ago, CoNSpiracy said:

Wouldn't it be a problem to go lower than that?

Not as long as you are do lighting with LEDs; it would take quite a huge amount of LEDs to go that far up. When you want to power other things like motors and the like, then it depends. In that case you can go to all the amperage you want/need - just make sure the voltage is right, e.g., a notebook power supply 9V / 1.7 A ($20)

Best
Thorsten 

[JaBaCaDaBra]

3 hours ago, Toastie said:

Is there anything that Ali does not sell?

Best
Thorsten

P.S.: Does anyone have a 10V wall wart from either LEGO or Ali? If so, is there a chance to measure the open-circuit voltage?

I have one but I strongly recommend NEVER to let the thing alone.
it was recently in the news here too, Ali junk is dangerous and in no way compliant to any safety rule.
That in combination with the Lithium cell it's loading is actually quite dangerous.
Just a minor glitch can result in fire and explosion.

About the voltage: I will ask Mr. Fluke what he thinks about it tonight.
Maybe a good idea to ask Mr. Tektronics if he wants to sniff on the signalform too.

Edited February 27, 2020 by JaBaCaDaBra

[pleegwat]

6 hours ago, Toastie said:

Is there anything that Ali does not sell?

Best
Thorsten

P.S.: Does anyone have a 10V wall wart from either LEGO or Ali? If so, is there a chance to measure the open-circuit voltage?

I have an official lego one, and what do you know - 11.8V. Alternating.

 

EDIT: Did a further check, since this is an original control centre II from the 90s, I'm betting the wall wart is a simple coil transformer and nothing else - they probably put all the electronics including the regulator inside the device. Motor output is 9.3 volts without a motor connected, and a good 9.0 with one motor.

Edited February 27, 2020 by pleegwat

[Toastie]

3 minutes ago, pleegwat said:

I have an official lego one, and what do you know - 11.8V. Alternating.

Holy guacamoly. Are you sure about the AC?

Best
Thorsten

 

[pleegwat]

I am, and on closer inspection even the label on the wall wart indicates it's AC. See my edit.

[Toastie]

1 hour ago, pleegwat said:

I am, and on closer inspection even the label on the wall wart indicates it's AC. See my edit.

Ahh, wait wait!

The RCX as well as the CCI + II came indeed with very simple AC/AC transformers. I do have them as well.

I was talking about the new 10 V/DC power supply #45517.

Here's the German LEGO Store picture: https://www.lego.com/de-de/product/transformer-10v-dc-45517

(Don't worry about the "wrong" plugs - they are American, but they don't care at LEGO at all - for years now. I guess simply nobody took a picture for an EU type device OR they can't even tell the difference, as the Chinese put these plugs on - regardless of the electronics inside, which works from 110 V AC to 240 V AC) 

TLG call this device the "Mindstorms power supply" - it is supposed to be good for recharging the #8878 LiPo (not available anymore) as well as the LiPos for the NXT and EV3 PBricks and the WeDo 45302 LiPo. All these devices "need" to be charged with 10 V DC - which is not true, see here:

It needs to be that way, otherwise people could sue the hell out of TLG because the charging sockets are very generic types - fitting almost every wall wart output. I believe it is hard to swallow such a wall wart, but you can certainly use a similarly looking one and plug it in.

So I am more interested in learning about the output voltage of that #45517 thingy.

All the best
Thorsten

 

Edited February 27, 2020 by Toastie

[CoNSpiracy]

So 8887 is not the same product as 45517, then?

[Toastie]

1 hour ago, CoNSpiracy said:

So 8887 is not the same product as 45517

I bet it is - renumbered for whatever purpose - maybe to polish it up a bit. 8887 is old. TLG makes only new stuff

Honestly, they should be the same.

Best
Thorsten

[CoNSpiracy]

I ended up with the following easy-to-do solution which does not involve soldering (only wire-stripping):

For 10½ Euros I bought a universal wall wart power adapter which outputs 3-12V (3 / 4.5 / 5 / 6 / 7.5 / 9 / 12 V), stabilised, 1.0A. It came with a bunch of different interchangeable DC male plugs, including 5.5 x 2.1 mm: https://www.av-connection.com/?PNo=NNA-1165

For 1½ Euros I also bought a DC 5.50 x 2.10 female to 2-pin terminal block: https://www.av-connection.com/?PGr=10964, which connects with the above-mentioned DC male plug. I then cut a LEGO Power Functions 8886 Extension Wire in two halfs and carefully separated the four cables at the cut end so that I could strip the wire of the two middle cables (C1 and C2) and connect them in the female terminal block. The two outer cables (GND and 9V), which has no use in this setup, I left untouched except that I protected with two pieces of isolation tape.

This works like a charm. I plan on adding a control switch (8869) right after this modified extension wire to allow for easy turning on and off. I noticed that without such control switch, if I turn off the power by just unplugging the wall wart power adapter, there is some residual / leftover power in the circuit which keeps the motor going / LED shining a few more moments.

So now I just need to decide going forward if I want to keep the voltage output setting on the adapter at 9V or 12V. The PF motors run faster and the LED lights shine brighter at 12V, instead of 9V which, however, is closer to the output of the original Lego PF battery boxes.

Edited March 11, 2020 by CoNSpiracy

[JaBaCaDaBra]

Maybe if you put an UA7810 voltage stabiliser in the circuit you get what you want.
These can dissipate 1 amps if correct cooled.

[Toastie]

15 minutes ago, CoNSpiracy said:

instead of 9V which, however, is closer to the output of the original Lego PF battery boxes

 

8 minutes ago, JaBaCaDaBra said:

Maybe if you put an UA7810 voltage stabiliser in the circuit you get what you want.

The 10V power supply is for >charging< the LiPo Versions of the various rechargeable batteries, TLG is/was offering for the PF/Mindstorms devices. These LiPos have all 7.2V >output< voltage. This is very different from powering something directly. You can use up to 18V >input< voltage to charge these LiPos as they have some "sophisticated" electronics on-board. 

The 10V powers supply is/was not intended to power the devices directly.

All PF/PuP/Mindstorms devices operated by (alkaline) batteries use mostly 6 x 1.5V = 9V operating voltage.

So your best bet is to use the 9V output of the power supply.

Best
Thorsten