LED tester and LED flashlights using one battery

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burger2227
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LED tester and LED flashlights using one battery

Postby burger2227 » Sat May 04, 2013 1:51 pm

Simple one battery LED tester circuit using a 20 turn, center tapped coil and one transistor:
Image
Coils can also be made without ferrite cores, but ferrite cores are more efficient and take less windings.
Battery voltage only goes to the center tap. The core diameter used is 10 mm and may be available on Ebay.

The circuit fits inside of half of a 2 AA battery holder with switch:
Image
A dual pin header is used to test new LED's and compare similar brightness levels for projects.

Every LED is lit pretty brightly as this test of 5 shows. This allows the comparison of LED brightness:
Image
The switch sends power to the coil's center tap. This circuit could also be used for flashlights to save battery usage.


With 2 extra testing wires, it can also test external LED's in a dead circuit:
Image
When a lower voltage LED is tested, bright ones will go dimmer as current takes the path of least resistance.
This low voltage LED pulled 15 or 20 milliamps, which is safe. Not sure which meter is correct...

The circuit can replace the battery closest to the LED like this AAA battery box I was using 2 batteries in until today.
Image
It uses a tact switch to complete the circuit to ground. The coil center tap goes to the positive end of the
rear end battery through the spring. Ground goes to the cathode leg of the LED which will be grounded by
the switch in the LED flashlight above. Running the ground from the circuit board directly to the battery
(as shown) will drain it prematurely. I found 200 microamps being drained so I changed it.

To use the circuit in a flashlight, it must have a wire from the transistor collector to the LED. It also
requires the positive voltage to the center tap and a common wire to the emitter and cathode of the LED.
Switches should isolate the battery from the circuit board, plus or minus. Most flashlights switch the common.
Last edited by burger2227 on Thu May 16, 2013 11:29 am, edited 2 times in total.
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Postby burger2227 » Mon May 06, 2013 1:06 pm

Converting a D cell flashlight to LED involves soldering a 10 mm LED into an old flashlight bulb base:
Image
Carefully break the old bulb and dig out the socket insulation enough to get to the bottom of it. Unsolder the
existing wire so that a small hole can be seen through the bottom. Insert the long LED leg through the hole
while bending the cathode leg toward the notch in the side. Some larger LED leads may not bend, but the
cathode leg may be wide enough to slip into the side slot. I had to cut the notch out a bit for some leads.

Flashlights normally have a switch to connect the bulb to the negative battery:
Image
The reflector back is connected to the switch through a copper bus that runs down to the spring
end of the flashlight. It is important to connect the circuit common to the top side of the switch and
connect the negative AA battery end to the lower part of the switch or the spring used by D cells.

I used a 2 AA battery holder to keep the circuit protected and soldered the coil center tap to the spring of the leading battery.
This will give the positive 1.5 volts from the second battery in the holder as the circuit is in the first battery's holding place.
Image
The battery minus wire goes to the bottom spring. Use extra wire to allow the wire to be twisted when the end is screwed back on.

The black circuit ground wire goes to the LED side of the grounding switch. In this case it was the long bus
coming from the switch to the reflector. The reflector back may be used as common too, but is hard to solder.
In this case I just wrapped the solid black wire around the bus and slid it down until it was spring held to the
side of the flashlight switch. The bus does not move with the switch. If it did, I would have had to solder it.
Image
Instead of using the red wire from the holder (I cut it short) , I ran a red wire from the circuit to
the LED bulb base tab directly as shown at the bottom of the picture above.

Final product with a bright bluish white LED.
Image

My next project will make a rechargeable flashlight that comes on when the electric power goes off.
It will incorporate the trickle charging AC circuit I used with the power failure outlet boxes.
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Sharabi
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Postby Sharabi » Sun May 19, 2013 12:03 pm

burger2227 wrote:Converting a D cell flashlight to LED involves soldering a 10 mm LED into an old flashlight bulb base:

Carefully break the old bulb and dig out the socket insulation enough to get to the bottom of it. Unsolder the
existing wire so that a small hole can be seen through the bottom. Insert the long LED leg through the hole
while bending the cathode leg toward the notch in the side. Some larger LED leads may not bend, but the
cathode leg may be wide enough to slip into the side slot. I had to cut the notch out a bit for some leads.

I used a 2 AA battery holder to keep the circuit protected and soldered the coil center tap to the spring of the leading battery.
This will give the positive 1.5 volts from the second battery in the holder as the circuit is in the first battery's holding place.

The battery minus wire goes to the bottom spring. Use extra wire to allow the wire to be twisted when the end is screwed back on.

The black circuit ground wire goes to the LED side of the grounding switch. In this case it was the long bus
coming from the switch to the reflector. The reflector back may be used as common too, but is hard to solder.
In this case I just wrapped the solid black wire around the bus and slid it down until it was spring held to the
side of the flashlight switch. The bus does not move with the switch. If it did, I would have had to solder it.
Instead of using the red wire from the holder (I cut it short) , I ran a red wire from the circuit to
the LED bulb base tab directly as shown at the bottom of the picture above.


My next project will make a rechargeable flashlight that comes on when the electric power goes off.
It will incorporate the trickle charging AC circuit I used with the power failure outlet boxes.

Yes, You are my inspiration for learning more about led flashlights.

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Postby burger2227 » Sat Jun 15, 2013 10:18 pm

The LED tester eliminates the need to worry about the voltages over 1.5 and the current is limited
to about 30 milliamps even with multiple LED's in parallel.

There are three main categories of miniature single die LEDs:
Low-current: typically rated for 2 mA at around 2 V (approximately 4 mW consumption).

Standard: 20 mA LEDs (ranging from approximately 40 mW to 90 mW) at around:
1.9 to 2.1 V for red, orange and yellow,
3.0 to 3.4 V for green and blue,
2.9 to 4.2 V for violet, pink, purple and white.

Ultra-high-output: 20 mA at approximately 2 V or 4?5 V, designed for viewing in direct sunlight.

Image
The chart indicates that current draw goes up very quickly at certain forward voltages(Vf) for different colors.
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Postby burger2227 » Tue Jun 18, 2013 10:02 pm

Here is a circuit that could be used in an existing LED flashlight by using it instead of one battery:
Image
http://cappels.org/dproj/vboostLED/vboostLED.html

The only problem would be that the existing LED is probably wired the other direction when 2 batteries were used.

The LED must be reversed in existing flashlights so that the anode goes to the negative battery terminal through the switch.
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Re: LED tester and LED flashlights using one battery

Postby burger2227 » Sat Dec 14, 2013 1:27 pm

I purchased an Indoor/outdoor Thermometer that has a button on top to light the backlight: Image
It is lit from both sides for a few seconds so it is hard to get a picture of.

This is the circuit board with the humidity sensor near the bottom left corner and the black indoor temp sensor above it:
Image
There are two lights for back lighting on each side with the red and black wires.

The lights are called LED's on the board, but they only use 1.5 volts at best as the whole unit runs on one AAA battery:
Image
I was able to remove one bulb from the side because the tape had pulled out already. It looks more like a light bulb than an LED!

I am going to try to use the flashlight LED circuit with a PNP transistor that will shut it off during the day:
Image
First I will try to use one of my solar panels to switch on and charge an external LED circuit using one AA battery.
The bright LED will be the only thing mounted inside of the thermometer. The battery holder circuit will be behind it.

One LED appears to light it up enough so far. I can just tape it to one side near the existing bulb and there should
be enough light. A single battery with daylight switching should last a week.
Image
I tested how it would look with a blueish while bright LED in my LED tester in this thread.

If the solar panel does not work out I can always change the circuit to a 3 volt photocell activated circuit that will last a month.
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Re: LED tester and LED flashlights using one battery

Postby burger2227 » Tue Feb 04, 2014 5:26 pm

Recently got an Energizer power failure light for $12 with a nite light that can be turned off, but not automatically:
Image
Night light has no room light sensor. The red LED in the slot indicates charging. It does not block other receptacles.

Here is the flashlight that has 2 brightness levels and comes on when the power fails when plugged in or removed from wall outlet:
Image
The flashlight can be turned on, bright or off with one button positioned in the center of the black area. It can
also turn off the night light which only comes on when the unit is plugged into the wall. Wish it went off to room light.

I was able to get to the CP300H battery with one screw. The battery is rated at 300 mah or about 15 hours at 20 ma:
Image
The raised area of the battery compartment may allow a larger battery type, but there is a large high voltage capacitor
located under the fuse between the PCB and the battery area that may present a problem if I want to expand the battery
area covering the capacitor for a AAA battery. We shall see...

Four more screws got me into the circuit board. The LED's and other end of the PC board will be harder to get to:
Image
The LED end is clear plastic and clipped together somehow so it might crack if I try to pry it.

Note that there are coils for each bright LED function to boost the battery voltage from 1.5 volts.

I also bought an $8 Sylvania power failure LED light, but it does not look friendly to outlet space or to taking apart:
Image
From Amazon comments it has 3 100 mah button batteries stacked horizontally in a pack that will eventually break apart.

I suppose that happens from heat when charging the batteries for months at a time.
The batteries do not appear to be connected together in any way, like they were stacked and wrapped:
Image
This light took the easy way out and put in more batteries than Joule thieves... I fear it is doomed.
2 AAA batteries with a 5252F chip may be all it needs if I can get it apart without destroying it!

The night light is very bright and very sensitive to room light. It kept going off when my camera sensor flashed:
Image
It only stays on while the unit is plugged in on Auto. On mode turns the flashlight on. The red light is always on
when the unit is plugged in. That also may spell doom...

The flashlight comes on when unplugged or there is a power failure in Auto mode:
Image


I will be evaluating both to see how they last and will update when necessary.
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Re: LED tester and LED flashlights using one battery

Postby burger2227 » Sat Feb 28, 2015 11:27 am

Exactly one year later, the Energizer emergency light quit working. The problem was the CP300H 1.2 volt battery!
Image
The batteries cost at least $6 each. I found one 5 layer battery pack for about $17 that could be taken apart...
Supposedly the battery should last up to 5 years on trickle charge of only 8.5 ma. Amazon sold out.

Before: I knew that there was a large power capacitor under the board, next to the CP300H battery so I decided to
sand off the covering with my Sonicrafter reciprocating tool to see if I had enough room to add a AAA battery holder.
Image

After: The reciprocating sander worked well and limited damage to components. Note the sanding marks on bottom of capacitor.
Image
Instead of a AAA holder, I used a 23AE 12 volt battery holder and cut it on half to connect a AAA battery in between.
I had to cut all of the casing below the battery so that it would sit below the cover plate properly and hot glued in place.

By moving the 205K capacitor a tiny bit I was also able to preserve the battery holder for the CP300H.
I wrapped cut resistor leads around the + and common contact springs and soldered the wires to them as solder
would not stay on the metal contacts directly.

Two AAA rechargeable batteries wore out in 2 days so I decided to check the charging voltage:
Image
.340 volts is hardly going to charge anything, but the charging circuit is most likely regulated as the red LED indicates.

Both AAA batteries could be recharged after removing them from the unit. The side white LED would go dim too.
I decided its power backup days were over and inserted a AAA alkaline battery and taped the 110 volt prongs shut.

The Sylvania Power Failure Night Light is still working fine!
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Re: LED tester and LED flashlights using one battery

Postby burger2227 » Tue May 17, 2016 6:17 pm

Radio Shack has sent me 2 email coupons for $5 off in the last 2 weeks:
Image
Today I used one for a $1.99 AAA battery holder and some slip on probes for my meters. Cost me 50 cents...

The store clerks seem to have problems scanning it on my phone, but I have gotten both discounts.

I plan to make another one battery flash light that I lost when a valet lost my keys:
Image
First I removed a plate holding the wires by heating 2 pins with a soldering iron to remove it on left.
Then I completely removed the red positive wire and plate by pulling it up with needle nose pliers.

I also removed the spring plate from the opposite end that contacted both batteries and slid the red plate in:
Image
Now the right side will hold one AAA battery and the left will hold the 5252 F solar chip circuit and LED.

I will try a 3mm white LED to power the light through the hole where both power wires were originally:
Image
It will also use a small push button tact switch to connect the common wire to the chip circuit to turn it on.

Remember that the 5252 F chip common would drain the battery more if it were always connected to it!
Image
BAT is pin 2, GND is pin 3 and LX is pin 4. I will use the configuration on the left as it only needs one battery.

The same common switch configuration is used on most older flashlights too so keep the chip common
above the switch on them too. Some newer LED lights use the wrong configuration unfortunately.
Please acknowledge and thank members who answer your questions!
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