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Author Topic: Question for those with Electronics knowledge (adapting 12V power adapter)  (Read 2792 times)

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JDFan

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OK a bit of background first - ( IF this is the wrong place to post this let me know and I'll ask a mod to move it but seems this sub forum deals with the electronics a bit more than other sub forums) I'll be building a small bartop with one of the NAMCO pac man plug and play units and a Slave monitor from a dual car DVD player and had a question that someone might be able to provide some answer for.

Currently I have 2 power adapters - one 6V 250ma that I use to run the Pac man unit ( soldered to the power connectors to bypass the battery compartment ) which runs on 3 AA batteries and a second 12V 1.3A adapter that runs the DVD screen which requires 9-12V .8A supply (according to the specs). Using the 2 adapters everything works fine but it seems a waste to use the second adapter if both could be run using the single 12V 1.3A adapter.

So the question is there an easy method to adapt a 12V 1.3A power adapter to supply both 12V 0.8A and 6V 250ma power so that both units could be run from a single power adapter. (from my little knowledge of electronics it seems it should be since the power draw wattage will be substantially less than the requirements but not sure if things would be stable if trying to place resistors or similar in line to drop the output from 12V to 6V while also running the 12V monitor.

Any one with any insight would be appreciated ( If it is a tough thing to do then using both adapters will suffice but as usual am wanting to experiment if it can be done fairly easily.)
« Last Edit: April 17, 2014, 10:20:55 am by JDFan »

DaOld Man

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You could use a 6 volt regulator mounted in the battery compartment of the Namco unit.
This regulator would drop the voltage from the 12 volt adapter to 6 volt.
It is a chip that has three leads, throw in a couple of capacitors and solder it in the battery compartment and you are good to go.
Here is a link to the chip (might be able to get one at radio shack, if you have one near):

http://www.jameco.com/1/3/voltage-regulator-6-volt

Note: if the Namco unit only uses 3 batteries, you might be better off to use a 5 volt regulator. 3 batteries = 1.5 volts X 3= 4.5 volts. (Unless the Namco unit takes a special battery that is more than 1.5 volts.)
Jameco should have the 5 volt regulators too, if you decide that's what you want to use.
« Last Edit: April 17, 2014, 09:58:50 pm by DaOld Man »

JDFan

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You could use a 6 volt regulator mounted in the battery compartment of the Namco unit.
This regulator would drop the voltage from the 12 volt adapter to 6 volt.
It is a chip that has three leads, throw in a couple of capacitors and solder it in the battery compartment and you are good to go.
Here is a link to the chip (might be able to get one at radio shack, if you have one near):

http://www.jameco.com/1/3/voltage-regulator-6-volt

Note: if the Namco unit only uses 3 batteries, you might be better off to use a 5 volt regulator. 3 batteries = 1.5 volts X 3= 4.5 volts. (Unless the Namco unit takes a special battery that is more than 1.5 volts.)
Jameco should have the 5 volt regulators too, if you decide that's what you want to use.

Thanks for the info -- It's 4 batteries (mistyped and hit 3) -- but it will run on as low as 4 - 4.5 volts since they allow for rechargeable batteries at 1.2V rather than 1.5V also.

Looks like something like this diagram should work and be fairly easy to put together ! (sure is easier to find info when you know what part name to Google !)

EDIT:  One follow up question - I have several small Heatsinks from old Video card memory chips, would it be best to put one of them on the Voltage regulator to dissipate the heat or will there not be much heat build up going from 12V to 5V ?

« Last Edit: April 17, 2014, 11:33:29 pm by JDFan »

JDFan

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How do the Chinese do it ?? Was looking around a bit more and came across the LM2596 DC - DC Buck converter which seems to be another alternative LINKIE -  ( http://www.ebay.com/itm/DC-DC-Buck-Converter-Step-Down-Module-LM2596HVS-Power-Supply-Output-3V-35V-/321356691196?pt=LH_DefaultDomain_0&hash=item4ad259f6fc )

Don't know how you can go wrong at $0.99 shipped for the entire circuit and their welding is much more accurate than mine ! (only drawback is the 10+ days it takes to get here )


DaOld Man

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Im not sure how the Chinese make their stuff so cheap (unless it is slave labor with no environmental or worker safety regulations).
That would probably work, but as simple as the regulator circuit would be, and for no more than what you need it for, I would go with the regulator, but its entirely up to you.
Also, you probably wont need a heat sink but it sure wouldn't hurt to use one if you have one laying around. be sure to put a drop of heatsink grease on the two mating surfaces or you are probably wasting your time.
If you do go with the voltage regulator, I would use the 6 volt one, since the Namco wants 6 volts.

JDFan

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Im not sure how the Chinese make their stuff so cheap (unless it is slave labor with no environmental or worker safety regulations).
That would probably work, but as simple as the regulator circuit would be, and for no more than what you need it for, I would go with the regulator, but its entirely up to you.
Also, you probably wont need a heat sink but it sure wouldn't hurt to use one if you have one laying around. be sure to put a drop of heatsink grease on the two mating surfaces or you are probably wasting your time.
If you do go with the voltage regulator, I would use the 6 volt one, since the Namco wants 6 volts.

Think you're right -- besides the main reason for doing this was to experiment with building it and even though the Chinese part is a bit cheaper it doesn't provide much build practice. (though I did go ahead and order a couple to play with for some other projects) Hopefully the local Radio Shack will have the parts in stock as nowadays they seem to be more focused toward mobile phone purchases than electronics parts ( Guess it's hard to run a business based on selling electronic parts when competing with the Chinese.)

Thanks again for the Info. and will update after building it. As for the heatsink will definitely be using some Thermal paste since the heat transfer needs a good surface to surface connection to work properly.

JDFan

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Went to Radio Shack and got a 7805 (they don't stock the 7806) and a couple Tantalum caps (total was about $6 - They sure do add a premium over the internet sites ( Caps online $0.59 +\- Radio Shack $1.99 )  Can see why nobody shops there any more.

Got home and put things together using an old Molex connector and though the soldering job isn't that great it all works as expected (nice stable 5V output from the 12V adapter ! )



 

DaOld Man

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Yeah Radio Shack definitely bloats the price of their parts, but I think they are trying to get away from that part of the service anyway, they don't have nearly as many parts as they once carried. I only buy from radio shack when I must have it right away and cant wait for snail mail.

JDFan

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Yeah Radio Shack definitely bloats the price of their parts, but I think they are trying to get away from that part of the service anyway, they don't have nearly as many parts as they once carried. I only buy from radio shack when I must have it right away and cant wait for snail mail.

It is pretty sad, they want so much for the parts and then the store just throws them in a little metal drawer display that never gets organized so you don't really know if they have it till you search the entire thing and asking someone that works there is a total waste as none of them have ever even build a project.

Slippyblade

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I know, necro thread...

Having worked at Radio Shack I do have to defend them a little bit.  If you've ever worked retail you would realize how literally impossible it is to keep small product organized.  The average modern American is a thumbless oaf.  They will paw through the bins/shelves/pegs, knock stuff around, damage goods, and then act like it's no big deal...

Working retail destroyed what little faith I had in humanity.

However, you are correct about part of it.  Most employees there have never built anything.  They are hired to sell cell phones.

  
 

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