9V battery for mods?

[Savager]

Newbie question here - why aren't square 9V batteries utilized for incandescent mods? Form factor? Low current?
Just curious. Thanks.

 

[charliek]

Not much current- they're great for LED lights, though....

http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Board=UBB14&Number=344908&Forum=UBB14&Words=9&Match=Entire%20Phrase&Searchpage=0&Limit=25&Old=allposts&Main=344908&Search=true#Post344908

 

[Cougar_Allen]

What a coincidence ... just before I logged on I got the idea of gutting a 2AA flashlight with a side-by-side battery configuration like the old Mallory, putting in two 9v batteries in parallel, and overdriving a KPR112 for an even smaller version of the Bargain of the Century mod (see http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Board=UBB14&Number=358982&page=1&view=collapsed&sb=5&o=&fpart=1 for details of that one).

First I tried connecting a single 9v battery to a KPR112 bulb -- and it just barely glows. Putting two in parallel is not going to help; there isn't enough current. Oh well ... I have some other ideas for that host, so I'm still going to go look for one today. Watch this forum.... /ubbthreads/images/graemlins/cool.gif

Using it to drive a led or leds seems like a better idea. Can you direct drive a single led without the smoke leaking out of it? Wire several leds in series?

If you want to make a real pocket flashlight you'll have to make a switch somehow. Occurs to me to make Halloween decorations or a free-standing cordless nightlight without even bothering with a switch -- just pull it off the battery to turn it off.

-Cougar :{)

 

[danielo_d]

Cougar
In regards to running LEDs off a 9V...
There are several ways to do it. You can use 1 LED with a 220 ohm resistor driven by the 9V. You can use 2 LEDs in series with a 100 ohm driven by 9V.
You can have several configurations as I'm learning, too. There are programs available to get the values needed.

This page has a calculator online w/diagrams here.
Another program you can download is located here.
The second one calculates much more, like runtime, current, Voltage, etc. It's written by CPF gurus [as I like to refer them].
Programmed by: John Trotto (jtice)
Concept by: John Trotto (jtice), Jim Koll (rothrandir)
Algorithm by: Wayne Yamaguchi (dat2zip)
Logo by: Dan Tran (logicnerd411)

These programs are great resources. I find them very useful. Hope you do too.

Danno

 

[Cougar_Allen]

Thanks!

-Cougar :{)

 

[unclearty]

I have been playing with this idea for the last few weeks. My latest project is simply 2 white 11,ooo mcd LEDs wired in series across a 9volt battery. It's amazingly bright. I've been playing with various ways to make a nice reflector to focus the beam. Simple, elegant...works very well.

 

[jtice]

Danno,

Glad to hear you like the program, and are getting some good use out of it. /ubbthreads/images/graemlins/smile.gif

The first, web based program you linked to, was actually one of the programs I used to check my programs accuracy.

 

[UK Owl]

[ QUOTE ]
unclearty said:
I have been playing with this idea for the last few weeks. My latest project is simply 2 white 11,ooo mcd LEDs wired in series across a 9 volt battery. It's amazingly bright. I've been playing with various ways to make a nice reflector to focus the beam. Simple, elegant...works very well.

[/ QUOTE ]

Rip up an old PP3 and salvage the batteries terminal.

Cut a piece of prototyping board the same size as this (the stuff that is pre-drilled and has copper circles around the holes on one side).

Build your circuit on this piece of circuit board.

Attach short flying leads to the salvaged battery terminal and glue together with a blob of quick set epoxy resin.

When epoxy is set, fill in the remaining gap between the PCB and Battery connection with some more Epoxy.

When epoxy is set file the edges smooth in line with the Battery Terminal.

You now have a cool homemade LED torch.

P.S. I have made several variations of this, the best probably being :

I have made the circuit using two white LED's running in parallel with separate constant current controllers (apply a fixed voltage to the base on an NPN bipolar transistor and couple the emitter to 0 volts line via a current control resistor. Connect LED between + volts and the transistor collector) and a power switch, all on a piece of PCB board this size.

I deliberately chose to use the LED's in parallel instead of series because efficiency was deemed to be not as important as constant light level, and with the two LED's in parallel a dimming would have been noticed much sooner with a dropoff on the battery voltage.

Also note, that as the circuit described is a constant current driver it will perform equally well from a stick of 4 cells (Alkaline of NiCd / NiMh), of from a standard PP3.

 

[unclearty]

UK OWL..could you possibly draw out what you just described..(see above). I'm very interested in this idea, and I'll have some "free" time Saturday. Thanks /ubbthreads/images/graemlins/confused.gif

 

[danielo_d]

[ QUOTE ]
unclearty said:
UK OWL..could you possibly draw out what you just described..(see above). I'm very interested in this idea, and I'll have some "free" time Saturday. Thanks /ubbthreads/images/graemlins/confused.gif

[/ QUOTE ]
Yes, I agree. Could you post a picture or schematic? I, too, may have some time. And I am very interested in your idea, too. /ubbthreads/images/graemlins/grin.gif

Thanks in advance.

Danno

 

[danielo_d]

Hey, thanks jtice!

I use your program to refamiliarize myself with Ohms law. I have long since forgotten it. A few other calculations, too.

Then again, with your program, I don't need to remember it... /ubbthreads/images/graemlins/blush.gif
Thanks again for the great utility you and your cohorts provide.

Danno

 

[unclearty]

Any chance of a diagram??

 

[Steelwolf]

[ QUOTE ]
UK Owl said:
(apply a fixed voltage to the base on an NPN bipolar transistor and couple the emitter to 0 volts line via a current control resistor. Connect LED between + volts and the transistor collector) and a power switch, all on a piece of PCB board this size.


[/ QUOTE ]

I can picture the circuit you described except for the part about the fixed voltage to the base.

Correct me if I'm wrong:
Battery terminal V+ >> LED+ >> LED- >> NPN collector >> NPN emitter >> Current control resistor (~150R) >> Battery terminal V-


How do you hook up the base of the transistor? Where does the fixed voltage come from?

 

[unclearty]

<<<bump>>>>

 

[Doug Owen]

[ QUOTE ]
Steelwolf said:
How do you hook up the base of the transistor? Where does the fixed voltage come from?



[/ QUOTE ]

Typically from a 'stiff' voltage. A voltage divider will work, but has some problem with fall off with battery voltage drop. A zener or other reference can correct this.

The formula is Vb=.7+(150 X Iled). That is the current through the LED and transistor also goes through the resistor (150 ohms in the example) causes a voltage drop, when this voltage plus the .7 Volts for the Vbe drop equal the base voltage, it's in regulation. Excess voltage (and therefore power) is dropped in the transistor. For instance, 10 mA causes 1.5 Volts drop, plus .7 means 2.3 on the base. Make that 2.8 instead and we have 2.8 minus .7, 2.1 volts across 150 ohms, we now have 2.1/150, 14 mA.

Doug Owen

 

[Steelwolf]

[ QUOTE ]
Doug Owen said:
Typically from a 'stiff' voltage. A voltage divider will work, but has some problem with fall off with battery voltage drop. A zener or other reference can correct this.

Doug Owen

[/ QUOTE ]

I apologise for being a bit slow on the uptake. I can't picture the wiring sequence for this part. Can somebody help?

 

[UK Owl]

Note : the Emitter resistior will typically be 20 - 30 ohms.

To get a fixed voltage you can use an lm317, but you will need to add a resistor between the output of the regulator and the base of the transistor as a base current limiter.

Another method is to put two diodes in series with a resistor, assuming 0.6 volts per diode you will thus have 1.2 volts. (Connect as follows, and use the junction betwwen the resistor and the 1st diode as your voltage reference : +Battery -> Resistor -> Diode -> Diode -> 0V Battery)

An alternative of this is to use a Red 3mm LED instead of the Diodes. (Select resistors such that 2 or 3 mAmps flow through it)

Note : The LED as a voltage reference is the least linear, but if you select the emitter resistor for 30mA through the LED at 9 volts (New PP3), you should get about 27mA when the voltage drops to about 5 volts. Not perfect, but pretty damn linear for such a simple circuit!

 

[UK Owl]

Here are the Pix that were requested :

Note : Item #2 & #3 have the LED's filed flat to give dispersed light.

Note : #2 shows 3 resistors, this is because at the time I did not have the correct resistor so two were used in series.

No # 3 & 4 use the same circuit, but this relies on the hfe of the transistor, so is not a true constant current source.

No # 1 & 2 both use a constant current source, but for 2 only one output LED is driven. Note : for # 1 the current control components are buried in the epoxy on the rear of the board. (Note : I have the description for #1 and #2 mixed up on the cct diagram. #1 uses the two LED's and no switch. #2 uses 1 LED and has a switch.)

No # 5 is a different animal altogether. This one will come on once the push button is pressed, and after about 10 seconds begins to dim. After about 20 seconds the LED is fully out. This circuit uses a ST72A FET transistor. (I bought a bag of 50 of these for £1 & £1 P&P of ebay)

Hope this helps you all.

 

[Doug Owen]

[ QUOTE ]
Steelwolf said:
[ QUOTE ]
Doug Owen said:
Typically from a 'stiff' voltage. A voltage divider will work, but has some problem with fall off with battery voltage drop. A zener or other reference can correct this.

Doug Owen

[/ QUOTE ]

I apologise for being a bit slow on the uptake. I can't picture the wiring sequence for this part. Can somebody help?

[/ QUOTE ]

Sure, sorry to be vague. Take 'UKOwl's #1 circuit and swap the diode in the center for a variable resistance.

A more traditional way is to use a 'pot' (potentiometer, a shaft variable resistor). Set it up so the bases are hooked to the 'wiper' and the two free ends hooked to the plus and minus supply. It needs to be 'stiff' that is not change much when the base current is drawn. For the circuit at hand, a one thousand ohm unit is probably a good start. Fully developed circuits might include fixed resistors in series with each end to control the range of control.

Doug Owen

 

[Steelwolf]

Thank you so much UK Owl. A picture truly is worth a thousand words.