Powering PF from AC; any advice?

[fred67]

So I know that, in this forum, most of you are concerned with mobile models that require a battery to use, but I also figured this would be the best forum to ask these questions as the people here seem more likely to know about stuff like this.

In order to not have to build around a battery box, I've been using 9v batteries and one of these:

And it occurred to me that, for my table top PF builds (in this case a track switcher for trains, or an elevator in a building), I could have an AC power adapter wired to a PF connector.  So I'd buy a PF extension, cut it in half, and connect it to these:

https://smile.amazon.com/gp/product/B01GPQZ4EE/ (female adapter cables) and

https://smile.amazon.com/gp/product/B012VQ5A7S/ (9v DC Adapter, 1000mA with 5 male plugs)

I could instead get a 500mA adapter, but I figure AAA are 1000mA, and have been using the AAA battery box).

 

[Wolf_Zipp]

I use also an 1,5 A Power-supply and an Extension , I made it special for my large MOC with my selfmade controlbox.

IMG_20180211_195406 by Wolf Zipp, auf Flickr

[fred67]

So I'm on the right track, then?  I have those amazon items in my cart, I just want to make sure I'm on the right track.

[Wolf_Zipp]

Hi Fred

You have to contact left > - < and right > + < with power in.

The 2 contact inside are to the Motor power out.

IMG_20180211_235027 by Wolf Zipp, auf Flickr

You can connect an Switch or IR on that to use the PF motor

[trekman]

Why don't you just buy a Lego 9V Speed Regulator Train Controller 2868b - the one with the yellow dial.  We use this for bench testing.  Use in conjuction with the power functions adapter cable and you are sorted.  Forward and reverse with speed control, if you need it.

[mocbuild101]

8 hours ago, fred67 said:

but I figure AAA are 1000mA

Well, to put it simply, no.

Battery captivity is measured in mAh - 1000mAh would mean that they would last for an hour with a 1A draw, or 4 hours with a 0.25A draw - so if they were powering 2 XL-motors, they would last for just under an hour. (see "Loaded Characteristics" on @Philo's website:  http://www.philohome.com/motors/motorcomp.htm)

Adapter current is measured in mA - 1000mA would mean that the maximum current that can be drawn is 1A - so 2 XL-motors is the maximum number motors it could fully power.

 

3 hours ago, Wolf_Zipp said:

You have to contact left > - < and right > + < with power in.

The 2 contact inside are to the Motor power out.

...or more specifically, the outer wires power the IR receivers - which can only be -/+, and the inner wires control the motors - which can be -/+ or +/-

 

1 hour ago, trekman said:

Why don't you just buy a Lego 9V Speed Regulator Train Controller 2868b - the one with the yellow dial.  We use this for bench testing.  Use in conjuction with the power functions adapter cable and you are sorted.  Forward and reverse with speed control, if you need it.

That can not power IR receivers, due to the PF extension/adapter cable only connecting the inner wires.

[fred67]

And speed regulators cost twice as much as a 9V DC wall adapter.  Also, things continue to get cheaper when you use non-LEGO cords for extension, to reach the far areas of my city, for example.

[dr_spock]

Years ago, I adapted extra AA battery boxes to use extra 9V DC adapters I had lying around.  It's probably as cheap as I can get.

 

[fred67]

That's cool; I'd thought about "dummy" batteries hooked up to an adapter for this game my son had (I can't remember the name).  The thing burned through 6AAs in less than an hour, and it wasn't even mechanical.  Must have been the absolute least efficient way to use the current.

I think it's great to alleviate the need for batteries, in any event, but also want to go small - although I suspect I could have something like this mounted under the table for the layout, which is how I was planning on running wires anyway.

[Captainowie]

I'd also recommend powering a battery box, rather than powering a PF cable directly. This is so that you can still use other features of the PF system (e.g. IR remote control). It is possible to modify a AA battery box in such a way that you can still use it with batteries.

If the AA battery box is too large, I expect it's possible (if a little fiddlier) to also modify the AAA battery box in the same way.

Let us know how you get on.

Owen.

[RohanBeckett]

https://bricksafe.com/pages/rbeckett/batteryboxmod

 

Although I've since modified it to use the standard 2.1mm power plug, rather than the cheap audio sockets I used initially :)

[fred67]

21 hours ago, Captainowie said:

I'd also recommend powering a battery box, rather than powering a PF cable directly. This is so that you can still use other features of the PF system (e.g. IR remote control). It is possible to modify a AA battery box in such a way that you can still use it with batteries.

If the AA battery box is too large, I expect it's possible (if a little fiddlier) to also modify the AAA battery box in the same way.

Let us know how you get on.

Owen.

I'd like to understand this a little bit better.  Does the IR receiver require more than the two outer power lines to function?  That is getting power to the receiver, obviously the control lines are used on the connections to motors.  Because my 9v battery adapter doesn't seem to have a problem being used this way.

[mocbuild101]

35 minutes ago, fred67 said:

Does the IR receiver require more than the two outer power lines to function?

No, just make sure you have the + and - the right way round. (I once fried a receiver by attaching them incorrectly)

[Captainowie]

18 hours ago, RohanBeckett said:

https://bricksafe.com/pages/rbeckett/batteryboxmod

 

Although I've since modified it to use the standard 2.1mm power plug, rather than the cheap audio sockets I used initially :)

Nah, cheap audio sockets are where it's at! :-)

1 hour ago, fred67 said:

I'd like to understand this a little bit better.  Does the IR receiver require more than the two outer power lines to function?  That is getting power to the receiver, obviously the control lines are used on the connections to motors.  Because my 9v battery adapter doesn't seem to have a problem being used this way.

Actually, I guess if you connect your power to both the outer wires and the inner wires together, you could use it to either power a motor directly or via an IR receiver. I hadn't considered doing that before.

[Wolf_Zipp]

12 hours ago, Captainowie said:

Actually, I guess if you connect your power to both the outer wires and the inner wires together, you could use it to either power a motor directly or via an IR receiver. I hadn't considered doing that before.

I connect the both left and both right wires from the cutted PF Extension to get a stronger mechanical connection to the plug.

When I connect a Motor to it , the Motor runs in one direction without stopping.

For the IR is it no problem, because from a Lego batt box ist also the inner wires under voltage.

Only the Servo motor needs all 4 wires to get in center position 

[knotian]

I just got lazy and left my rechargeable battery box plugged in.