Batteryless Power Functions

[Captainowie]

Hello all.

I have seen plenty of places on the Internet where people have hotwired their LEGO battery boxes and hooked them up to a laboratory power supply. I have also seen plenty of places where people have converted an old PC power supply into a cheap laboratory power supply.

However, I've not seen anywhere on the Internet where people have done both. So I did it myself.

Details here http://www.lugnet.com/~2801/PowerSupply

Questions, comments, queries or concerns?

[bord4kop]

Nice, must look into this myself someday..

Great article at lugnet

Edited March 16, 2014 by bord4kop

[Captainowie]

Hmm, I really thought this would have generated much more interest.

Is it the way I've presented it?

Is it the fact that the bulk of the information is on an external website, and the effort required to go there is just too much in today's time-poor society?

Is it that this is not interesting? Perhaps lots of people have done this and I just haven't heard about it.

Is it that most people build vehicles, which would make something like this less useful?

Could it even be that "This Captainowie chap has only made a handful posts, so he couldn't possibly have something worth saying"? (I'd like to think it's not this, but you never know...)

Or is it simply that it left the front page of posts so quickly that most people haven't had a chance to see it properly?

Owen.

[Cyclotron102]

I think it could work good with this http://www.eurobricks.com/forum/index.php?showtopic=91329

because in real life these giants working with the same principle

[Sariel]

Is it that most people build vehicles, which would make something like this less useful?

Sort of. I, for one, don't see the point in using something the size (and weight) of a brick, when the Lego rechargeable battery suits me fine.

Edited March 20, 2014 by Sariel

[kieran]

Lots of guys use the old 9V Train Transformer as well

[D3K]

I think this would be good for static models, like GBC modules, and maybe harbour crane models and such..

As to why you didn't get the responses you were hoping for, I think it might be just the fact that the majority of MOCs built are models that are meant to be moved around, so a wire going to a wall socket might not be ideal.

I like the idea, might make something like it to keep on my work table, to test mechanisms during the building process

[Captainowie]

Yes, it's primarily good for static models. I had GBC specifically in mind. This setup could easily power a dozen or more modules all day long, something that you can't do with a PF rechargable battery, or even a train regulator (I assume they're current limited? Happy to be corrected here).

But for sure not ideal if you mainly build vehicles.

I guess I assumed there were more non-vehicle builders here that this might appeal to. In hindsight, I don't know why I assumed that, given the vast number of vehicle-related topics!

I like the idea, might make something like it to keep on my work table, to test mechanisms during the building process

For that sort of purpose, you're probably better off just buying a 9V adaptor from your local electronics store and modifying a battery box to accept that, unless you want to power more than one battery box (not likely at a testing station, I'm guessing). The power supply can take up a lot of room on your table.

Owen.

[doug72]

In my Giant Block Setting Crane the battery box serves a dual use in providing the counter balance weight as well as powewring the PF componants.

Maybe if crane was static an external suppy might be OK but if crane is mobile on rails trailing cables won't work.

[Doc_Brown]

I recently started testing some gearboxes, and found that all my battery boxes were going flat, so something like this would be ideal!

[Moz]

A long time ago I modified one of those old battery boxes too. I added a 3.5mm audio socket near the buttons so if fitted in between the batteries. That way it was still usable with batteries in it. The socket I used has a built in switch that operates when something is plugged into it, so I ended up with quite a usable device.

Just be aware that they have quite a low current limit - 3A or so and the wiring will get quite hot.

[JM1971]

Controllers need far too many batteries, there should be connectors so when you attach more than one together they all run off one unit or a psu.

[dr_spock]

A long time ago I modified one of those old battery boxes too. I added a 3.5mm audio socket near the buttons so if fitted in between the batteries. That way it was still usable with batteries in it. The socket I used has a built in switch that operates when something is plugged into it, so I ended up with quite a usable device.

Just be aware that they have quite a low current limit - 3A or so and the wiring will get quite hot.

I did something similar since I had a bunch of 9V AC/DC adapters from old modems. Mine weren't that fancy but I could unscrew the audio socket from 8881 battery box and put in batteries in an emergency.

I haven't thought of using a PC power supply due to the fan and other openings where stuff can fall in.

[Moz]

I haven't thought of using a PC power supply due to the fan and other openings where stuff can fall in.

To me they're wildly overpowered for the job, so they lose a lot of power when they're pumping out the 9W or so that a Lego motor uses. They usually have a 5W or more fan, for starters. If I want that I have a 3A lab power supply on my desk already. Only if I was powering a display at a show where I had 10 or more motors running would I look at a PC power supply. And I'd try to gimmick the 12V rail to give me 9V directly, rather than using a linear regulator.

[Captainowie]

To me they're wildly overpowered for the job, so they lose a lot of power when they're pumping out the 9W or so that a Lego motor uses. They usually have a 5W or more fan, for starters. If I want that I have a 3A lab power supply on my desk already. Only if I was powering a display at a show where I had 10 or more motors running would I look at a PC power supply. And I'd try to gimmick the 12V rail to give me 9V directly, rather than using a linear regulator.

I agree that, used in this way, they're running very inefficiently. "Wildly overpowererd" is probably an understatement. However, they're a heck of a lot cheaper than a lab power supply, and nearly as reliable.

Could you explain what you mean by "gimmicking" the 12V rail? How else would you get 9V from the power supply?

Owen.

[Boxerlego]

I think it is a great idea to have a power supply to powertest the motors. However I've just recently pick up a Three phase motor on the Lego scale. What kind of modification for the Powersupply will be require to power a Three Phase motor.

[DrJB]

Lots of guys use the old 9V Train Transformer as well

That's exactly what I use ... got 3 of them and enough to power several GBC modules.

Not sure anyone would go through the trouble of designing something 'iffy' when the train transformer can be had for around $25.00

[Captainowie]

I think it is a great idea to have a power supply to powertest the motors. However I've just recently pick up a Three phase motor on the Lego scale. What kind of modification for the Powersupply will be require to power a Three Phase motor.

The power supply converts high-voltage AC into low-voltage DC. You'll want something that converts high-voltage AC into low-voltage AC, which suggests that starting from a PC power supply is not going to work very well for you.

Edited March 22, 2014 by Captainowie

[DrJB]

I think it is a great idea to have a power supply to powertest the motors. However I've just recently pick up a Three phase motor on the Lego scale. What kind of modification for the Powersupply will be require to power a Three Phase motor.

a three-phase motor should run on AC only ... and all three need to have their phases 'locked' by 120 degrees relative to one another ...

Wait ... are you serious?

The power supply converts high-voltage AC into low-voltage DC. You'll want something that converts high-voltage AC into low-voltage AC, which suggests that starting from a PC power supply is not going to work very well for you.

Not quite ... there is an easier way though. The Lego train and control transformers do output low voltage AC (not DC). This of course, assuming you have a mechanism (circuit) to re-create the 3 phases ... Did you say Y or Delta?

[Boxerlego]

The power supply converts high-voltage AC into low-voltage DC. You'll want something that converts high-voltage AC into low-voltage AC, which suggests that starting from a PC power supply is not going to work very well for you.

I've been reading about using transistors to drive the three phase motor. Tho I'm not quite sure yet on how to time the transistors properly to simulate the ac wave form.

a three-phase motor should run on AC only ... and all three need to have their phases 'locked' by 120 degrees relative to one another ...

Wait ... are you serious?

Yes I'm serious. I've just made the Gear Adapter to mesh with the pinion gear on the three phase AC motor.

[Moz]

Could you explain what you mean by "gimmicking" the 12V rail? How else would you get 9V from the power supply?

Most PC PSUs are switch mode and it's at least theoretically possible to change the output reference to get a different voltage. So my first thought would be to see whether it's possible to get 9V directly out of the "12V" rail, rather than using a linear regulator. But that's when I went "no, waste of time, you're already losing so much power than an extra 3W here and there isn't really going to matter. On the other hand, if you're using a PSU anyway it would be worth looking at if only because changing a couple of resistors is likely cheaper than buying a linear regulator. Something like this

Edited March 22, 2014 by Moz

[Captainowie]

Most PC PSUs are switch mode and it's at least theoretically possible to change the output reference to get a different voltage. So my first thought would be to see whether it's possible to get 9V directly out of the "12V" rail, rather than using a linear regulator. But that's when I went "no, waste of time, you're already losing so much power than an extra 3W here and there isn't really going to matter. On the other hand, if you're using a PSU anyway it would be worth looking at if only because changing a couple of resistors is likely cheaper than buying a linear regulator. Something like this

I see. That's certainly a viable option, but requires a level of knowing-what-you're-doing far in excess of what I possess!