# Eliminate multiple battery packs & wire for AC plug?



## spinachetr (Nov 9, 2009)

Hi, new here. My wife said something to me that she will eventually regret..."You can do whatever you want for Halloween next year." That being said, I'm buying up post Halloween sale items. I bought 7 sets of Gemmy skull string lights at Biglots ($2.50ea). They are battery operated and flash and play music. I wanted to wire them all in a row (series?) and have them on a plug and not 7 battery packs. Each string runs off 3 AA batteries...so from what I've seen on the forums i would need a 21volt adaptor. I really don't care for the music they play and will be getting rid of the speaker. I do like the way the skulls flash so I know I will have to keep the circuit boards in them. But then again as long as they light up I could live without the flashing. 

Any special tip/trick for wiring them in series and keeping the flashing? Or would the simplest thing to do would be to just cut out the circuit board altogether? Would a 20v laptop power plug work to power the string of 7 lights? Thanks in advance for any insight.


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## spinachetr (Nov 9, 2009)

sorry...I attended public school.....it would be 31.5 total volts. What, if any, power plug/adapter could I use. Thanks.


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## spinman1949 (Jun 29, 2009)

*Stop !!!*

No you do not need 20 volts.

You need 5 volts. Three batteries equals 4.5 volts. You will provide each set via parallel wiring with 5 volts.

You do not add voltage up to figure the amount of voltage you need. You do add up the required amperage though. Double AA batteries are likely rated around 1200 mah. That is they are capable of providing 1200 ma per hour. or .1.2 amps per hour. This is a general statement. AA batteries range from 600 to almost 3000 mah. Likely your strings pull much less. So lets say they pull 500 mah. Multiply 7 X 500 and you end up needing a wart that provides 5 volts with a 3.5 amp output. This will be a good place to start. Keep in mind though that non regulated warts can actually provide higher voltages when they are not subjected to their rated load. You may want to start low to be safe. Find a wart that only provides 2 amp output. Hook all 7 strings and see if the wart gets hot. If it stays relatively cold or slightly warm to the touch you are close. If the lights are dim or the wart gets hot quickly, then your wart is rated too low on amperage output. Hope this helps.


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## bradbaum (Jul 26, 2008)

I think you want to wire them in parallel -

you will need a (1.5x3=4.5) a 5 Volt DC power supply should be close enough.

If you have a multimeter set it to amps and measure the current each one draws and multiply by 7 (the number of lights) add some extra to this and that is the current you will need.

Since they are double A batteries, I would guess you will need about 500 milliamps per unit - so figure about (.5x7=3.5 amps).

This should do it:

http://www.allelectronics.com/make-a-store/item/PS-537/5VDC-3.7A-SWITCHING-POWER-SUPPLY/-/1.html

hope that helps.

Spinman beat me to it!


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## spinachetr (Nov 9, 2009)

Awesome! Thanks for the quick replies. Probably wouldn't be a good idea to fry TOTs on my first haunt attempt. thanks again.


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## spinman1949 (Jun 29, 2009)

*If you saw how slow I type !*



bradbaum said:


> I think you want to wire them in parallel -
> 
> you will need a (1.5x3=4.5) a 5 Volt DC power supply should be close enough.
> 
> ...


Glad we are on the same playbook re this. Likely beat you by a gnats eyebrow. Reminds me of agent 86. "Missed me by that much" LOl !!


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## HomeyDaClown (Oct 3, 2009)

bradbaum said:


> This should do it:
> 
> http://www.allelectronics.com/make-a-store/item/PS-537/5VDC-3.7A-SWITCHING-POWER-SUPPLY/-/1.html


I would not use that unit. I have one and the voltage is not well regulated when you draw more than one amp. Mine dropped to 2.7 volts! Many people have reported in reviews and on other forums that the voltage drops quickly after 1.5 amps with that supply.

A good source for a cheap higher amperage 5 volt supply is an old PC power supply.


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## bradbaum (Jul 26, 2008)

then this one should do it:

http://www.goldmine-elec-products.com/prodinfo.asp?number=G12705

you will need to put it in a box and wire a AC power cord to it.


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## fritz42_male (May 5, 2009)

I used several of these this year - cheap and good.

http://www.dealextreme.com/details.dx/sku.22383


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## asterix0 (Nov 5, 2008)

This one is cheap and has plenty of power:

http://www.allelectronics.com/make-a-store/item/PS-575/5VDC-11A-SWITCHING-POWER-SUPPLY/1.html

However, it too needs to be mounted.


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