dollhouse power supply?

[baastrup]

Hey I bought  this 8 X AA battery pack for wich I hope to use for my doughters dollhouse.

My plan is to add an on/off switch, and maybe a fuse?
Please let me know if you have any ideas or security concerns,

[jpanhalt]

Father of three girls here.  They are all grown with families now.  Their doll house got a lot of use.   I would consider a timer to turn it off should they accidentally forget to do that, or NiMH rechargeable batteries.

John

[Gyro]

I suppose, with decent alkaline batteries (or indeed NiMH) there is easily enough energy to start a fire in a nice flamable dollhouse. This might be the perfect application for a small PTC thermistor.

[baastrup]

How do I make sure the small lamps and such dont get to many amps?
Im planning to use NiMH rechargeable batteries.

and would it be dangerous for my kids with 8 X AA at 12v?

[james_s]

If you supply the correct voltage, the lamps will draw the current that they need and no more, according to Ohms law and the resistance of the filament at operating temperature. NiMH cells will be about 1.45V each fresh off the charger and settle to around 1.2V, alkaline will be around 1.5V or a tad more fresh and then gradually decline.

NiCd and NiMH cells can deliver huge current into a short circuit so a fuse or PTC as close to the battery holder as possible is a good idea.

[Gyro]

If I were you, I would follow the domestic trend and go for LED lighting. This will give you many more options for minature lighting (LEDs are smaller than bulbs), and greatly reduce your power supply needs.

[baastrup]

What PTC/Fuse would you recommend? what model etc.

Any ideas for LEDs are welcome as well :-)

[Andreas]

Hmm,

arent the lamps usually with 3.5-3.8V?
Using a 3 cell flat battery?

https://www.conrad.de/de/flach-batterie-zink-kohle-varta-superlife-3lr12-2700-mah-45-v-1-st-614386.html

with best regards

Andreas

[james_s]

I would think a 1A fuse ought to be adequate, that will be sufficient to protect the wires and should be more current capacity than the lamps you use will draw. For a PTC something with around a 1A trip current ought to be close enough, have a look at the parametric search on Digikey. It really isn't that critical.

[tpowell1830]

You could use an inline fuse, like this one:

http://www.mscdirect.com/browse/tnpla/74680638?cid=ppc-google-New+-+Lighting+%26+Electrical+-+PLA_sh6ctsdk3___164124449210_c_S&mkwid=sh6ctsdk3|dc&pcrid=164124449210&gclid=CPfFrpCl7dECFU5tfgodZGgB-g

I would make the fuse at least 2 amps. Your wire is rated higher than that, so it should do nicely.

PEACE===>T

[james_s]

It really depends on the load. While the fuse only really has to blow if the current exceeds what the wire can tolerate, there's no reason to use a fuse substantially larger than the largest load you intend to have.

[Gyro]

What PTC/Fuse would you recommend? what model etc.

Any ideas for LEDs are welcome as well :-)

It depends - if you stay with bulbs then they might pull 40-50mA each at 12V. With modern white LEDs then you might find that each LED might be as little as 1mA. You can probably drop to 6V supply too. Each LED will need a series current limiting resistor, probably around 750R to 1.5k (experimentation needed).

If using LEDs then probably the smallest current PTC you can find, say, 50mA would provide maximum protection for the (thin) wiring and batteries.

As far as LEDs, ebay is your playground. I don't know what your fine skills with tweezers and soldering are like but you could probably use 1206 size smd LEDs glued to the ceilings and soldered with fine wire (the resistors could probably be smd too). If you are less good, then wire ended 3mm through-hole parts (wide angle). SMD would be neat though. Maybe you can do uplighters / table lamps too.

You are the first generation who can realistically implement LED lighting in a dollhouse for your children - let your imagination go wild! 

[ed_reardon]

What PTC/Fuse would you recommend? what model etc.

Any ideas for LEDs are welcome as well :-)

You are the first generation who can realistically implement LED lighting in a dollhouse for your children - let your imagination go wild! 

There is something quite humbling about that! 

[Gyro]

There is isn't there!

It looks as if imagination has already been at work...

http://www.ebay.co.uk/sch/i.html?_odkw=hakko&_osacat=0&_from=R40&_trksid=p2045573.m570.l1311.R1.TR2.TRC0.A0.H1.Xled+doll.TRS0&_nkw=led+dolls+house+lights&_sacat=0

EDIT: Although I'd use them as idea sources as they mostly seem to be self powered, individual batteries could get expensive!

EDIT 1: The button cells used in those standalone lights can be very dangerous if swallowed (there have been several reported cases recently) if you buy them then re-wire to use your 'central' power supply.

[tpowell1830]

How do I make sure the small lamps and such dont get to many amps?
Im planning to use NiMH rechargeable batteries.

and would it be dangerous for my kids with 8 X AA at 12v?

I know this is a basic, fundamental question, but, I have to ask: Do you know the voltage/current ratings of your current lamps?  If the voltage rating of the lamps is lower than 12 volts, you will possibly exceed the current rating and blow the bulbs using a 12 volt battery pack.  If you replace your lamps with LEDs, then you will place a current limiting resistor inline with them, based on the LEDs current rating that you chose.

PEACE===>T

[Zero999]

As mentioned above, a fuse or PTC resistor (often called a poly fuse) will do.

If you go with LEDs. They normally have a forward voltage between 3V and 3.8V and you need a resistor to limit the current and there would be no point in using more than four AA cells in series. If you must go with 8 AA cells, then you could connect three LEDs in series, which wastes less power in the resistor.

[jeroen79]

What size of wire are you using?
This would be the limiting factor for current and you should fuse the circuit just below the wires' current rating.

Look up AWG or american wire gauge.
That should get you a table of gauges and current ratings.

[baastrup]

Im not sure what the aquarium at the picture can handle but it seems to have a resistens of 9.2ohms according to my DMM.

[james_s]

Surely there's a standard voltage used for this stuff? Does it say on the package? Have you searched online for dollhouse light voltage? Failing that, I would suggest using a variable power supply and dialing it up until the brightness looks reasonable. It's likely some multiple of 1.5V since I suspect it would typically run off carbon zinc or alkaline cells.