Technic Power Box Mod to use 9v Power Supply

[TechnicBrickPower]

Hi Everyone,

This is probably not a new idea but I have modified my Lego Technic power box to connect directly to a 9V power supply to save on batteries and to generate more power by being able to increase the voltage. I have uploaded the video to my YouTube channel I started 4 weeks ago. I like building heavy lifting cranes and needed more consistent power and also with the power supply I have I can measure the current too. Let me know if you found this useful.

Rob

 

 

[suffocation]

Maybe not a new idea but by far the clearest, most comprehensive tutorial I've ever seen - thank you!

Have you got a link for the power supply you used? I wouldn't know which one to choose from among the thousands out there.

[sirslayer]

You can even use a PC computer power supply!!!    Red color lines on the pc power supply are 5 volts and the yellow color lines are 12 volts.. only thing you need to do is use a jumper wire on the power supply to keep it on!!!!  Any power brick rated 9 volts should do , but buying a Lab/table power supply is kind of over kill!!! 

[Permo]

I don't get it...

Just cut a Lego extensioncord and hook it up to the powersupply or any other battery.

Hook up to a pair of V2 receivers and you'll be surprised.

[TechnicBrickPower]

Hi Permo, yes that's maybe a better idea! You know sometimes an idea comes to you and you just go with that without thinking about other options. That's what's great about this community - sharing new and other ideas. Thanks for your comment.

If anyone is interested in the power supply I used you can get it on aliexpress https://www.aliexpress.com/item/33008811576.html?spm=2114.12010612.8148356.6.c5fc1d9a2sBN85

There are many others to choose from. What I like about this supply is that it shows you the current as well as voltage and also the voltage is variable.

1 hour ago, suffocation said:

Maybe not a new idea but by far the clearest, most comprehensive tutorial I've ever seen - thank you!

Have you got a link for the power supply you used? I wouldn't know which one to choose from among the thousands out there.

Thanks for your feedback much appreciated. The supply I used is https://www.aliexpress.com/item/33008811576.html?spm=2114.12010612.8148356.6.c5fc1d9a2sBN85

[Mechbuilds]

Wouldn't it be better to modify a lipo battery inside that box instead? 

[BrianGT]

I tend to just not put batteries in my battery boxes and then put an extension cable from a 9v train controller to the battery box output terminal to power the model.

[dr_spock]

Nice to see extra battery boxes are still being converted and the why still comes up.     That lab power supply do look useful for other electronic projects that doesn't involve lugging it around to LUG events.

I don't have any 9V train controllers, so I converted my battery boxes as an el cheapo solution. Somehow I managed to blow a new 9V wall power adapter at the last show.  That's kind of weird since I didn't remove the 800mA resetable polyfuse in the battery box and that 9V adapter is rated for 2.2A. Previously I used the older bigger transformer wall warts which weren't that energy effecient.  But at least they never failed me.

 

[Philo]

10 minutes ago, dr_spock said:

That's kind of weird since I didn't remove the 800mA resetable polyfuse in the battery box and that 9V adapter is rated for 2.2A.

This happens with that kind of switching power supply. Aluminium capacitors used often have a poor life time, shortening even more as temperature raises (divided by two for a 10° temperature increase!). Their electric losses raise, and finally they explode...

Edited November 23, 2019 by Philo

[TechnicBrickPower]

Hey everyone... received a few messages about putting on a disclaimer...so here it is:

 

BE CAREFUL - I can't be held responsible if you destroy your battery box. If you are not confident doing this mod then don't do it - that said it is pretty straight forward...lol. Also don't plug it into the mains! 9V DC only.

 

Also there are other solutions to this problem. I don't know how high a voltage you can put on there before you blow stuff up. Maybe someone else can share their experience?

Anyway good luck and have fun.

 

[Philo]

3 hours ago, TechnicBrickPower said:

I don't know how high a voltage you can put on there before you blow stuff up. Maybe someone else can share their experience?

Theoretical value is pretty low: the motor driver inside the IR receiver (LB1836M) has a 9V rating, with a 10.5V AMR (absolute maximum rating). So if you want to be on the safe side, you should never ever exceed that 10.5V limit.

[TechnicBrickPower]

Thanks for that answer!  I cranked it up to 10v the other day, lucky I didn't go any higher, lol. It did start behaving funny even at that voltage - the current suddenly dropped to almost 0. What about the motor itself without an IR receiver?

[Philo]

1 hour ago, TechnicBrickPower said:

It did start behaving funny even at that voltage - the current suddenly dropped to almost 0

I wouldn't expect weird behaviour. IR receiver "idle" power consumption should be very low anyway (about 17mA, see http://philohome.com/pfrec/pfrec.htm ).

1 hour ago, TechnicBrickPower said:

What about the motor itself without an IR receiver?

Motors themselves are much more tolerant and have no intrinsic voltage limitation. The main problem is overall power dissipation for a heavily loaded motor (dissipated power raises as the square of voltage...). My motor tests are done up to 12V (http://philohome.com/motors/motorcomp.htm).

[dr_spock]

On 11/23/2019 at 1:49 PM, Philo said:

This happens with that kind of switching power supply. Aluminium capacitors used often have a poor life time, shortening even more as temperature raises (divided by two for a 10° temperature increase!). Their electric losses raise, and finally they explode...

Thanks for the info.  I should find some time to cut open the blown 9V adapter and see what happened inside.  

 

[TechnicBrickPower]

Did you end up finding out

On 11/26/2019 at 9:38 PM, Philo said:

I wouldn't expect weird behaviour. IR receiver "idle" power consumption should be very low anyway (about 17mA, see http://philohome.com/pfrec/pfrec.htm ).

Motors themselves are much more tolerant and have no intrinsic voltage limitation. The main problem is overall power dissipation for a heavily loaded motor (dissipated power raises as the square of voltage...). My motor tests are done up to 12V (http://philohome.com/motors/motorcomp.htm).

Thanks for the information in the link - you have a lot of very interesting set of graphs there. Thanks for taking the time to make all those measurements - I think I will be referring to them often in the future :)

[2GodBDGlory]

I did a similar thing a while back, where I just took an old transformer (originally used for charging something or other), cut off the end, and attached the positive and negative ends to the positive and negative plates of a spare AA battery box. I now have it screwed onto the bottom of my desk, as a constant, switchable PF power supply!