# DC Circuit Questions



## kneed2know (Apr 10, 2006)

We need some HELP!! For my daughter's birthday celebration my son and I are planning to build her a "back light shadow box". She had mentioned that it would be fun if she could display the X-Ray she received for a broken leg while playing hockey for the first time. This is more of a novelty thing but since she mentioned it to us we want to surprise her.

We have the design of the box all figured out but are not sure of the "electrical" design considerations.

Our plan is to use DC voltage using batteries, an ON/OFF switch and eight 2.3V flashlight bulbs. We've already purchased the shadow box, the 8 bulbs w/sockets. BUTTTTT we're not sure "how many batteries of which type" we would need for that many bulbs. Our plan is to wire them in parallel using 28AWG wire with the DPST switch on the "+" side of the battery source.

SO our questions are:
1.	Is this doable?
2.	If so what type and how many batteries would you recommend?
3.	What type of switch would you recommend?
4.	Is AWG 28 wire OK to use?

Her birthday is the 22nd of April so we have a little time, but need to squeeze this in among our normal activities.

ALL SUGGESTIONS WILL BE GREATLY APPRECIATED!!!

Don & Eric
E-Mail - poshsop[at]hotmail.com


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## Noyb (May 25, 2005)

(8) 2.3 volt bulbs in series will need 18.4 volts.
Standard flashlight batteries are 1.5 volts .. so 12 (1.5V) batteries in series will get you 18 volts.

Running all in series will use the least amount of current and the smaller wire might be OK.

It's not a good idea to put your Email address out in the open ... unless you like Spam.
May I suggest you remove it, if it's not too late ... edit you last post.

Why don't you scan the Xrays and use your monitor as a shadow box ... I'm lazy.
Our cat has bad hip joints ...


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## JohnWill (Oct 19, 2002)

I "obfuscated" your email address to minimize the amount of SPAM you get. 

I'd also use #22 or larger wire, #28 may be a bit small.


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## Noyb (May 25, 2005)

_#28 may be a bit small._ I was thinking it'd make a good fuse.

You could use this Serial/Parallel arrangement and cut the cost of the batteries in half ...
... If you use bigger wire.

Two can live as cheap as one ... Half as long.


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## n2gun (Mar 3, 2000)

You can get 2 and 4 cell battery holders at radio shack for about $2 ea. I like the setup Noyb has drawn. To save soldering batteries and make them easily replaceable I would use the battery holders.


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## Noyb (May 25, 2005)

This S/P arrangement doubled the Current, so I'd use "D" cells.
More AH for the buck this way.


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## kneed2know (Apr 10, 2006)

Thanks For Your Input You Guys Are Great!


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## JohnWill (Oct 19, 2002)

Noyb, you have a bug in your circuit!


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## kneed2know (Apr 10, 2006)

Please review attached diagram


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## Noyb (May 25, 2005)

Scanned, Analyzed .. And I'm happy to report ...
No Bugs Found


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## Noyb (May 25, 2005)

*BUT* ... Since you used 18volts worth of batteries ... I would have gone to a Series arrangement and used "D" cells...
or eliminated one 9volt pack .. in your series/parallel arrangement.

This will prevent any possibility of a stronger cell from trying to reverse charge a weaker cell in the other battery pack thu the bulbs.

Especially advantageous if you want to use Nicads.


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## JohnWill (Oct 19, 2002)

There's actually A BIG problem with the circuit!

You have the bulbs wired in parallel, so the voltage supplied to them should be 2.3V, and NOT 9.2 volts. You need to wire the bulbs in series for that to work.


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## kneed2know (Apr 10, 2006)

THANKS TO ALL for your help!!

I originally had all of the bulbs (8 2.3V) in series and when I tried by hooking up the batteries (12 1.5V) the first 2 bulbs in the string were illuminated partially, the next 2 even less and the last 4 not at all. The wire connection which we (my son) was holding for testing got very warm in a short period of time (approx 25 secs).

We stewed over this for awhile then we got the idea to just do 4 bulbs with six batteries hooked-up and WALLA!! the bulbs came on very bright and that's when we drew up the wiring diagram that I submitted this morning.

Based on your excellent comments and even quicker replies, - I'm still not sure what the final configuration should be......any chance of attaching a simple schematic showing us the correct hook-up?

We're closing in on my daughters birthday so we have to stick to our (solder) guns.

You Folks are great!!

Kneed2know aka Don:up:


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## Noyb (May 25, 2005)

John ... Thanks for double checking me ... It's sure embarrassing to overlook the Obvious.
The Schematic in post #6 (without the bug) is one way ... 
I'll see if I can whip up a Parallel schematic using 12 batteries ... be back.


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## Noyb (May 25, 2005)

If you want to use 12 batteries .. They'll last twice as long, but cost twice as much.
Here's how I'd wire the 12 battery circuit.


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## Noyb (May 25, 2005)

kneed2know said:


> I originally had all of the bulbs (8 2.3V) in series and when I tried by hooking up the batteries (12 1.5V) the first 2 bulbs in the string were illuminated partially, the next 2 even less and the last 4 not at all. The wire connection which we (my son) was holding for testing got very warm in a short period of time (approx 25 secs).


In your diagram ... The batteries were also not in Series.
I suspect this was the problem and source of heat.

--- [Red Black] ---- [Red Black] ---- [Red Black] ---


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## kneed2know (Apr 10, 2006)

The wiring diagram I sent today was my attempt at doing the bulbs & batteries in a in SERIES PARALLEL hook-up.

The original attempt we made when they were all in SERIES was not depicted in the diagram that I sent to TECHGUY.org

Looking forward to a schematic and/or a wiring diagram

THANKS!
Kneed2Know


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## Noyb (May 25, 2005)

I understand ... And saw the difference.
Your Series/Parallel in post #10 would have resulted in a lot of heat and maybe some burned out bulbs.
I should have looked closer the first time... Sorry.

Your all in series should have looked like ....


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## JohnWill (Oct 19, 2002)

I'm still confused about the blocks of batteries with no connections.  I assume that you are really trying to indicate all of the batteries are wired + to - totally in series?


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## Noyb (May 25, 2005)

John strikes again with yet another good observation/suggestion

I think he's referring to the radio shack battery holders ... That have Red & Blk wires.
Not shown in this link ...
http://www.radioshack.com/product/i...+holders&kw=battery+holders&parentPage=search

More specifically ... They should be wired like this ...


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## kneed2know (Apr 10, 2006)

Noyb & John Will,
YES John as Noyb has pointed the batteries are in a Radio Shack holder, in Series with just one BLK and One REDlead extended.

I'm going to rewire my project using the Nyob Series connection diagram. I'll re-post as to the success I have.

THANKS!! to you both and anyone else that responded to this original DC Circuit Question. I really like this site and have passed the URL off to many folks.

SEE YA!
Kneed2Know


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## Knotbored (Jun 5, 2004)

I think I will make a backlight box using clear Christmas tree lights mounted under a deep picture frame with a sheet of paper between double glass for the face. It won't be battery powered but---


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## JohnWill (Oct 19, 2002)

I give the updated circuit my stamp of approval.


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## kneed2know (Apr 10, 2006)

Hi,
Were still having trouble with the circuit containing the (8) 2.3V bulbs and the (12) 1.2V AA batteries. 

As was suggested in a prior posting No. 15 my son and I re-wired the circuit to match the Series Hook-up. When we hook up the circuit ends (effectively close the On/OFF switch) the lights kind of flash and we burn out one of the bulbs. 

Its a random burn-out and we have made a bulb tester to isolate the bad bulb. We had to hook up a separate C battery with a socket to test the individual bulbs to locate the burnt out one. Its never the same bulb in the circuit.

The problem with the series hook-up is that we must keep testing to see which bulb is burnt out after we apply poser. The bulbs are very small and its difficult to see the filament even with a magnify glass.

BUT even more importantly we can never get the bulbs to stay on for any length of time.

Weve used a C battery and a jumper across each socket and get the individual good bulbs to light. We thought we might have a cold solder joint, but all eight sockets with good bulbs light individually.

Were open to any more suggestions my daughters birthday is tomorrow, so its most likely this will be a belated gift. 

Weve also thought of going back to the original Parallel circuit that I showed in posting No. 9 but thought it would be best to hear your suggestions about our present problems.

THANKS IN ADVANCE,
 Kneed2know


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## Noyb (May 25, 2005)

Sounds like the parameters for the Lamps are not consistent ... 
So - One (or more) Lamps gets over powered.

How bright are the Lamps when powered with one Cell ???


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## kneed2know (Apr 10, 2006)

Noyb,
They seem to be quite bright, I would guesstimate about the same as if it were in a flashlight.

Kneeed2know


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## Noyb (May 25, 2005)

Maybe you don't have the correct lamp specs.
Try only 8 Cells ... for the 8 lamps.


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## kneed2know (Apr 10, 2006)

NOYB,
WOW !! I'm surprised and thankful for your quick reply to my posting. I'm in San Jose CA and it's just 5:25am here so I didn't expect a reply until later today.

Since the battery holders are in series and I remove 4 batteries (making that holder empty) do I need to jumper around or unwire that particular holder?

THANKS AGAIN!!

Kneed2know


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## JohnWill (Oct 19, 2002)

I'm guessing you're way off on the lamp specifications if they burn out immediately. Why not try one lamp on one battery and see how bright they get? Are you sure these are not 1.5V bulbs?


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## n2gun (Mar 3, 2000)

sounds like 1.5 volt bulbs to me too. try with just 8 batteries take one battery holder right out of the circuit


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## Noyb (May 25, 2005)

I should have asked earlier ... When running one Lamp on one battery ...
Does it look bright enough to do the Job ???
And is the Light White or does it have a hint of Orange ???

If you run 8 lamps from 8 batteries .... Are they all about the same brightness ???


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## JohnWill (Oct 19, 2002)

The exact part number of the lamps would be useful here.


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## kneed2know (Apr 10, 2006)

Hi Noyb, N2gun & John Will,
I haven't had a chance to try the 8 battery step.....yesterday was a fun filled day for ny daughter's birthday. We went to the Oakland CA zoo, had a great time and I got away before they could get me in any enclosure.

The lamps are from radio Shack and they are #243 (222) 2.33V, 270Ma and it states on the package that the lamp is for a 2 cell AA battery.

As far as hooking up one batttery for a single lamp, we did this and they seem to glow quite White/Bright. The only any seem to have a dull orange glow is just before we lose the circuit because a lamp burns out.

I'm thinking of hooking them up like I presented in my series/parallel diagram in Posting #9running 4 lamps with 6 batteries. Unless you guys have a different scheme, I may try that type of hook-up later today.

THANKS IN ADVANCE,
Kneed2know (aka Don)


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## Noyb (May 25, 2005)

Incandescent Lamps do not work like resistors ... They are more of a constant current load.
If their specs are not reasonably consistant ... Then there may be a problem when wiring them in series.

If you still have a problem with the 8 battery/4 lamp series connection ....
Then you may have to run all the lamps in a Parallel arrangement ... 
From one .. (or maybe two batteries)

This is why I asked how they looked .. With one lamp on one battery.


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## JohnWill (Oct 19, 2002)

I know of no reason why those lamps wouldn't work in the circuit previously presented. I would expect the same brand and part number lamp to be consistent enough to run in series, I've never seen them that won't.


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## Soundy (Feb 17, 2006)

Just another idea: use a bunch of white LEDs for the backlighting. It'll cost a bit more initially, but they won't burn out, you'll need a lot fewer batteries, and the batteries will last a lot longer.

Another option would be flourescent backlighting - find one of those little two- or three-tube battery-powered camping lanterns and scavenge it for parts. 

Both options will also result in a lot less heat.


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## JohnWill (Oct 19, 2002)

Good ideas, I use white LED's here, can't believe I didn't think of that.


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## kneed2know (Apr 10, 2006)

Noyb, John Will, N2gun & Soundy,
THANKS for the suggestions about the LED's and the miniature fluorescent lights BUT, the lamp sockets are already mounted in place as are the battery holders. It's presently wired in SERIES and I still haven't tried the 8 battery test. (the unit is at my son's house and with his work and my teaching schedule we haven't made contact yet (pun intended))

Nothing has been tried since my last posting and it looks like Wednesday evening is our next attempt to make this thing work. I'll keep every one posted. THANKS again for hanging around and continuing with your suggestions.

FYI .......I scanned in the actual drawing I had made showing the Backlight box design (both Front and Back) saving them as separate "jpeg" files. When I tried to attach it to a reply, I received a message that the the files exceeded the file size limitation. I'll try to cut out some of the detail so the scans fall within the file size parameters and try again to attach them.

THANKS TO ALL
Kneed2know


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## Soundy (Feb 17, 2006)

Try reducing the quality setting (or increasing the compression setting, depending on your software) in the JPEG options. That will produce a smaller file size without needing to shrink the physical size of the image.


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## Noyb (May 25, 2005)

Needed to resize them to about 800 x 600 ... with about a 90% jpeg quality compression.


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## Soundy (Feb 17, 2006)

You know, when my son broke his leg, the hospital gave us a CD with copies of his X-rays... my wife set one for the wallpaper on her cel phone. It was cool, but kinda creeped most people out...


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## kneed2know (Apr 10, 2006)

Noyb,
Thanks for doing the jpeg compression, the box drawings that I made in MS PowerPoint came through just fine.

I just wanted to get them posted so the folks that have been replying to my circuit problems could see what the end product will look like.

Later today I'm off to my son's house to try the 8 battery suggestion and hopefully we'll be able to throw the switch and say "Let there be light!!"

I'll post the results.........THANKS AGAIN TO ALL!!

Kneed2Know (aka Don)


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## Soundy (Feb 17, 2006)

Just one other concern: those bulbs will generate a fair bit of heat, especially with that many of them... you'll really want to include at the very least some venting in the back panel. Probably won't need a fan, just some slots or holes at the top and bottom, and allow convection flow to do its thing.

Just looked at the x-ray pic, that looks like about the same place my kid broke his leg a couple years ago


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## kneed2know (Apr 10, 2006)

WALLA!!
We tried the 8 battery suggestion staying with the series hook-up and still no light!!

SO, we jury rigged one half of the circuit into the parallel hook-up like we had shown in Post #9 (i.e. 4 lamps in parallel, one side (+) to the 6 batteries and the (-) side to one terminal of the switch with the battery (-) to the other switch terminal) A flick of the switch and we had light, also we did the bad lamp test , taking one out of the circuit and the other 3 kept on glowing.

For our next trick.we rewired both sets of 4 lamps with 6 batteries and we were as happy as a pig in mud. BUTwhile sitting there at the work bench, we heard a sizzling sound and looking closely, noticed that the batteries in the 2 battery holder were actually getting quite warm and there was some liquid coming out the sealed end. We very quickly took them out and the lights kept on glowing.

We then took one battery out of the 4 battery holder, just to check if it was also leaking, and that set of lamps went out.

In looking at Post #12 John Will had stated:
You have the bulbs wired in parallel, so the voltage supplied to them should be 2.3V, and NOT 9.2 volts. You need to wire the bulbs in series for that to work.


So were very confused as to how this is working and wonder if Edison had this much fun working on that first lamp. Looking forward to any feedback on this present hook-up.

Kneed2know 

P.S.
Thanks for the ventilation suggestion, we'll make some slots. Also, FYI the foot shown in the PowerPoint drawing is not her actual X-Ray, it's a simulated break.


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## Soundy (Feb 17, 2006)

My guess would be that you've somehow got it wired so that the two-battery holder is shorted and not actually in the circuit... double-check all your wiring!

Frankly, I don't know why you wouldn't just wire all the bulbs in parallel - a single pair of batteries in series would supply the proper voltage, and adding more pairs would simply increase the "run time". There'd be NO concern about varying bulb specs causing unexpected voltage drops, no need for complex calculations of "this many batteries for that many volts across those many bulbs," and one bulb burning out wouldn't cause them all to go off.

KISS principle!


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## Noyb (May 25, 2005)

The battery holders should have the proper polarity indicated  for the installation of the batteries.

I suspect your problem has been youre not installing the batteries properly.
The polarity (+/-) Must be observed.

The diagram in post 9  should have blown all the Lamps and several batteries.

You may also have several bad batteries now.

Wire this . And observe the battery polarity.


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## Soundy (Feb 17, 2006)

That's all it takes. Again, if you need more CONSTANT run-time, just parallel more pairs of batteries. They'll last as long in total no matter how many you add, though, so unless you need the thing on for hours and hours at at time, it's easier to just use a pair and change them out when they die.


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## JohnWill (Oct 19, 2002)

Paralleling batteries isn't the best solution, which is why I prefer the series solution. One battery with a lower voltage will tend to discharge the other batteries. You have to ask yourself, why don't I ever see batteries paralleled in any consumer equipment?


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## Soundy (Feb 17, 2006)

I do... every little "cordless travel shaver" I've ever seen parallels two or three AAs. I think a bigger reason is that most of the electronics they power are designed to run at 5V or more. When you need four batteries in series just to provide the necessary voltage for the components, you don't need as much current, or have the room for as many batteries.

Anyway, doesn't change my circuit above... a pair of Ds in series will run the bulbs in parallel quite nicely. As I said, there's really no need to parallel batteries anyway, unless you need the thing to stay on for prolonged periods - one pair at a time, changed out twice when they die, will last approximately as long as three pairs at once.

Ultimately, the energy usage of the bulbs will be about the same no matter how they're wired, so any given number of batteries will give the same operative time no matter how they're wired. It's not a question then of battery life, only of complexity... or lack thereof.


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## Noyb (May 25, 2005)

kneed2know has mentioned a couple of times about things getting hot while Paralleling batteries....
And/or the lamps not responding as we would expect.

I'm thinking *ALL* these problems have been caused by not observing the polarity of the Batteries in each series string ... (of the parallel arrangement)
This will result in the output Voltage not being what is expected ...
And the reverse charging of the "reversed" Battery(s) ... causing High current and excessive heat.

In a single series string ... 
The improper voltage from a reversed battery (or two) would give the false indication that it wasn't wired right....
or the voltage wasn't what what was needed (expected) to run the Lamps.

*kneed2know* .. You got a Camera ??? ..... Pictures will help.


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## JohnWill (Oct 19, 2002)

Soundy said:


> I do... every little "cordless travel shaver" I've ever seen parallels two or three AAs.


I have two of these little travel shavers, and both of them have the batteries in series. Next observation please.


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## kneed2know (Apr 10, 2006)

HI To All You Postites!!
The design is complete, there is sufficient back lighting and my daughter will receive this belated birthday gift today.

In addition, we made a handbook that has the drawings we made (that were shown on Post #40 Thanks to Nyob) and a copy of all of the Posts (#1 thru #51) so she'll be able to see the dialog that took place during this design cycle.

THANKS AGAIN TO ALL WHO PROVIDED INPUT TO US!!!

I'll be back again when confronted with a design concern or curious about the gadgets that are in our life.

Kneed2know.


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## Soundy (Feb 17, 2006)

kneed2know said:


> In addition, we made a handbook that has the drawings we made (that were shown on Post #40 Thanks to Nyob) and a copy of all of the Posts (#1 thru #51) so she'll be able to see the dialog that took place during this design cycle.


HAHAHAHAH, now THAT is original thinking! She'll never forget how much grief and confusion the old man went through for her  Nicely done!


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