Electronic projects using LEDs

[burger2227]

Here is another power failure outlet box using two white LED's.

Since this one uses 3 LED's I ended up with a similar layout as the previous one I made with the transistors
on each end of the PC board. I used a smaller 10mm toroid coil, but it still required standing up to fit.



This time I used a AAA rechargeable battery, becauseI had a few of them laying around doing nothing
and they should last long enough for most blackouts. At 750 ma hours, drawing 32 ma, it should last 20 hours easily.

The battery holder is an A23 holder cut in half to make it longer. AAA batteries are the same diameter.
In this particular outlet box, the battery will fit perfectly between the 2 angle braces. Unfortunately I had
already cut one out so I used some insulation putty to help retain the proper length.

I put all of the AC trickle components at the bottom after I swapped the buses from top to bottom to
accommodate the new circuit wiring. It had that ugly orange night light circuit I messed with before.

Testing with AC power off:

The green LED run off of the AC trickle voltage is between the 2 white ones to indicate everything is OK.
I also got new 4 X 1/2 wood screws so I did not have to have a special bit to remove the back to change the
battery if it ever dies for some reason. The trickle charger should not harm them at 6ma tops.

I am going to start work on an LED tester by testing the orange LED and making sure it doesn't blow up.

[burger2227]

I finally tested that ugly orange night light LED in circuit without blowing it up:

It is pathetically not bright either, but it killed the green power LED on the tester while it was connected.
The power indicating LED is in parallel with the tested LED, so that may happen when the test LED uses
less voltage. The green LED is a bright one rated at 3 volts.

The LED tester I came up with works off of capacitive reactance and automatically limits the LED current
to 20 milliamps using 120 volts at 60 cycles per second:

I had a 3 outlet multiplier box so I built the circuit inside of it. It has two rows of female pin connectors in the slots where
the AC used to be to test and compare brightness of a few LED's at once.


Here is some QB code to calculate the current available with different AC voltages and high voltage capacitors:

Code: Select all

'Inductive Reactance = 2*pi*frequency*inductance
'Capacitive Reactance = 1/(2*pi*frequency*capacitance)

DO
  INPUT "Enter AC supply voltage: ", voltage& '= 120
LOOP UNTIL voltage& > 0

ACfreq = 60 ' 50 'in Europe and Asia?
DO
  INPUT "Capacitor farads(1uf = .000001) or microfarads >= .001:"; capacity '= .000000068
LOOP UNTIL capacity > 0

IF capacity >= .001 THEN capacity = capacity / 1000000

PRINT USING "Capacity = .############ farads"; capacity

Creact& = 1 / (8 * ATN(1) * ACfreq * capacity)

PRINT USING "Reactance = ########,.## ohms"; Creact&

current = voltage& / Creact&

PRINT USING "Supply Current = ##.###### amps"; current

Note that the calculation uses 60 Hz for American electric supplies. Europe and Asia use 50.
The capacitor value can be entered in Farad decimal point values or Micro Farads greater than .001.

The circuit I used, at top left, uses a .47 uf, 250 volt capacitor and 1K resistor to limit current:

I added a resettable fuse rated at 1.35 amps and a MOV both rated at 30 volts.

The narrower slot (top bus pictured below) should be the bus that the capacitor is soldered to.
To prevent reverse polarity problems connect the 1K resistor to the ground prong instead of the common bus!
If the tester does not have a proper ground it will not work. Safety first when working with high vltages!
I also added BNC connectors for testing LED's in circuit or for volt meter readings when needed.

Note: The capacitor must be rated for at least 200 volts! Also put a 1 Mega ohm resistor across it
to drain any left over voltage when disconnected.

Also, do not remove the round ground prong! It keeps the high voltage line in the right place on the capacitor!
That way the high voltage is best isolated from the user. Again, don't plug the circuit in with the back off of it!


This is the box I made it out of. The buses can be broken off by bending them back and forth with pliers:

I broke off the buses to the other 2 outlets so that only the center one would have power. To prevent accidents,
I taped over that center outlet too. I kept enough of the line buses to keep them stable or they might wobble too much.
The 5mm green LED slid right into the ground hole and rows of female pin header connector strips fit tightly in each prong slot.

After I cut the strips to fit each slot. I soldered a resistor wire to every connector so the pins would not fall out.
They will all be the same polarity anyhow. One slot took 4 and the other took 5 to fit tightly.

Since the green LED is in parallel with a tested LED, it may turn off if the voltage drop across the test
LED is less than 2 volts. Use a bright 3 volt or higher LED for the power indicator or other LED's may not light!

The biggest headache was the BNC connectors as the back of the box is tapered in. Took a lot of effort to fit.

[burger2227]

AC projects can also use adapter plugs to add AC to a box directly or through a cord:

This adapter does not require the wires to be stripped at all. Just spread the wires apart and rout in channel.
Use the screw to pull the sides together and complete the connections.

Slots could be cut into a project box if the box is to be plugged directly into the wall.


This box will be made into a flashlight that only comes on if the AC power is lost or it is unplugged.
It will not require a switch and will stay charged up until needed using the AC power failure circuit.
It will also have a test button and a power indicating night light.

Once the wires have been crimped, the adapter can be cut down to fit inside of the box.

Keep the box retaining the wiring together while trimming it to fit in a project box.
If it is inside a box, it should not need much to restrain the wires unless you are brute...

If it has to be cut down below the screw, use good tape or glue to hold it together.
Only cut it down to fit inside the box or it will need to be glued in to prevent it from moving inside
of the box when it is plugged in. Make sure that it cannot pull out of the box either! Slots will prevent
that too.

[burger2227]

I tried to use the following circuit as a power failure LED driver:

(The Light Dependent Resistor required about 33K to ground instead of 100K and no 100 pf capacitor).
Instead of using the LDR, I sent the AC trickle voltage directly to the lower transistor with varying resistances.
The AC trickle power is not enough to drive the shutoff transistor. I had to use a 2N2907 PNP transistor
as a switch to cut off power to the LED driver just like the other flyback driver.

The nice thing about this circuit is that you can use coils without having to wind them or find forms.
Convert .470 mh to 470 uh. The BC338 transistor can also be used, but it draws more current.

The 2N2907 or 2N5401 shutoff transistor requires a 100 uf capacitor on the rectified AC base trickle voltage.

The PNP transistor replaces the bottom transistor used to shutoff the solar light oscillator by grounding it's base.
The PNP transistor cuts off all current when voltage is on the base so this circuit can use regular batteries too.
If non-rechargeable batteries are used, do not try to trickle charge them as they may overheat!

This outlet box had a partial back so the circuit is visible. All of the high voltage is wired in the center with the LED's.

The red wire comes from the plus battery, green is the trickle current, blue is plus to LED's and white is common.
Using solid wires holds the circuit in place so it does not move around in the box and cannot fall out.

This was an older box I had already used for a while. The AAA rechargeable battery is in the bottom open area for easy access.
The battery holder is held permanently in place with clear silicone calking on each end. It takes a few hours to solidify.

There is a green LED in the center as a power indicator.It can be wired right after the .068 uf capacitor's
330 ohm resistor in the box center.


I used a 30 volt resettable fuse and MOV for safety also. If a regular fuse is used, place it ahead of the
capacitor rated for the incoming AC voltage and 800 ma or less. Jumper the high voltage capacitor with
a 1 mega ohm resistor to discharge it when the unit is unplugged and prevent getting shocked.

Once the back plate is replaced, it should never have to be removed again.
Make sure that the back cannot come off when the box is unplugged!

The circuit board does not take much space so it could also be used for an emergency flash light too.

2N5401 transistors are cheaper PNP transistors than the 2N2907 at 50 cents apiece.

[burger2227]

I found the problem with the 2 coil white LED driver circuit:

The trickle voltage to the cutoff transistor requires a larger capacitor than what I had used.
A 10 uf capacitor is large enough. Larger capacities will delay the triggering of the light.

Note that the Green LED is also required to rectify the reverse AC cycles. Use another 1N4007 diode if
the indicator LED is not desired. Otherwise the white LED driver will stay lit.
This circuit will use more battery current than one using a PNP transistor to shut off the supply voltage.

Interestingly the same base set up can also be turned on and off with a solar cell. The 9 volt solar cell I
use is slightly more sensitive to light and turns the LED circuit on a bit sooner with this setup. The BC547
transistors are a lot cheaper than the 2N2907 PNP ones.

Thanks to Richard Cappels for all of his assistance on these projects.

[seaBiscuit$]

Woo! Awesome stuff! Fellow EE here.

Looks like a nifty weekend project. i'll try it out sometime. Looks like i've missed a lot. i've been gone too long.

[burger2227]

Good to see you SeaBiscuit$! Where's your horse?

Here is my next power failure project, a 3 outlet adapter box with another sick looking night light using a tiny neon bulb:

After slotting out the box area in the lower corner, I was able to insert a .068 uf, 200 volt Mylar capacitor into it.

I managed to fit the 30 volt MOV and resettable fuse with resistor into the adjacent slot above the capacitor for the trickle circuit:

After I soldered everything together, I slid it into place. It took a bit of effort to align everything right.
I pulled the insulation off of the heavy duty common wire to thin it down and added a fiberglass insulator.
The ground bus is held in place with clear silicone calking as it kept falling out.

It will be using the premade coil circuit from above run with a rechargeable Varta V15H 1.2V 15mAh NiMH
button battery. The LED driver circuit only uses about 12 ma, so it should last for about an hour if the power fails.
It will also serve as an LED night light that will be a lot brighter than the old light, though it will stay on.

Varta Data sheet charging specifications:

The .068 uf capacitor delivers 3 milliamps of trickle current which is considered accelerated above
The trickle charge rate would require just a .01 uf, 200 volt capacitor on 120 volts AC.
Trickle charging the battery would allow the battery to last 6 years but the cap could not run the
green LED or turn the PNP power failure transistor off.
A 200 K resistor on the trickle charge voltage will limit the charging current to the battery to .45 milliamps.

Typical button battery loads will be 15 ma or less. Maximum loads are 30 ma so the flyback torroid coil circuit
could not be used as it draws more than 30 ma with 1 or 2 LED's.

I plan to have the two power failure LED's in the 2 lens inserts and the night light LED above them. I may wire
the green wire to that LED from above and have the 2 diodes go directly down to the board and battery from there.
If I have enough space, the circuit could also include an LDR run cutoff transistor so it doesn't light during power
failures during the day.

This is the circuit with a light dependent resistor(photocell) to shut it off during the day if power fails:

Tests of the circuit show a 1 ma current draw when it is daylight and 10 ma when the LED's come on.
The 2N5401 or 2N2907 PNP transistor completely cuts off battery power when there is not a power failure.

It is sensitive to any light source including the LED's so the LDR needs to be mounted away from the clear lens!
It will require its own mounting hole in the front to access the room light.

[burger2227]

I decided to put the button battery down near the ground bus because there was room there:

I had to grind out one of the plastic brackets the hold the ground bus in place and make a hole up to the next level for a wire.
The ground bracket will still slide onto place underneath it and be securely held in place by the back cover when re-assembled.

The V15H battery holder is actually a holder for a slightly larger CR1220 battery so I had to bend the outside bracket in a little.
The + area is on the outside and the negative pole is in the center face down. I soldered on the red wire and fished it through a hole
up to the circuit board area. Since the battery wanted to pop out, I then held it upward and soldered the negative side to
the common AC bus above it. The bottom tab of the holder shown above is the negative battery lug.

Next comes the LED circuit board. This will be interesting to make...

I marked the circuit board where the 3 LED's will be placed and located the ground legs for all 3 in the center:

The power indicator LED is in the center with the long anode leg to common. The other leg can go directly to the green trickle
charging wire. This LED rectifies the reverse AC current and is vital to the operation of the power failure switch transistor.

The final LED positions are adjusted after soldering the ground legs together. The red wire connects the two power failure LED's positive leads:

The green wire can later be soldered to the middle LED leg and to a diode going to the board for the PNP switch transistor base voltage.
I will also wire the diode and 150K resistor to the red wire above the circuit board for trickle charging the battery. Saves space on the board.

The final board has the PNP switch transistor on the left, LED transistor under the middle LED and darkness switch transistor on the right.

The red wire going across is the battery voltage to the PNP emitter. The blue wire supplies voltage to the photocell when necessary.
The capacitor on the PNP transistor base is only 10 uf because of limited space, but it should be OK. I tested the LED and LDR circuit
with a single AA battery beforehand as the button battery is not charged up high enough to run it on its own. It will need charged.
The trickle voltage from the green wire will go to the left of the battery diode. The red battery wire will go to the right of the 150K resistor.
The hardest part of assembly is lining up the photocell(LDR) in the front hole on the right side while sliding it into place.

[burger2227]

Here is the final schematic for the V15H button cell battery. Trickle charging is limited to .57 milliamps for battery longevity:

Again, the 100 uf capacitor can be changed to 10 uf if space is limited and the PNP transistor will still work OK.

The battery will take a long time to become fully charged. Something like 5 days for one half hour of LED operation, but it also
serves as a low power LED night light because I used a bright LED for the power indicator.

The small hole for the LDR (photocell) can be seen on the right of the LED lens as the wall outlet is wired upside down.
I really needed some extra outlets there as Verizon hogged the other one with permanent equipment I cannot move or remove.

[burger2227]

UPDATE: Not sure how good those V15H batteries are that I received. Best run time is only 20 minutes. I also decided to cut the 150K trickle charger resistance in half because it took forever to charge it up for 5 minutes, let alone 20. I may have to go up to a V40H (40mah) battery as it is the only other kind with that same diameter. It is a bit thicker, but that should not matter. There is plenty of height room for that.

[iamdenteddisk]

that is great, i was hoping i hadn't totally missed this thread as I have been away a while. good to see you kept pushing toward the goal TED. I don't get much leisure time but when i do I come here to check in.

the battery your using the 40mah I don't recall common cells having such low mah ratings. I think I would still use a 800 or 100 mah if possible or paralell enough to reach that. as it will require maybe a week to charge but still once it had a charge would last longer.

"emergency light"-we loose power maybe once a month with a random storm and power outages last on average about 2-4 hrs before crews get it going again but on extreme cases could take as long 4 days "normally". though a low mah rating will charge quicker 20 min of emergency light might get you to the pot for business but you'll never find the paper in the dark-right?

with emergency lights even taking a month to full charge is reasonable if you get an hour or two of light from it.. there is no real need for quick recharging "in most cases". it would be different if it was a battery backup for a heart monitor..

for the most part imo, your still on track and your project looks "commercially acceptable" or as good quality as you get from the store..kuddos!

[burger2227]

When the power is turned off, it is bright enough:





It lasts about 10 or 15 minutes instead of an hour so I blame it on the battery I got.

[iamdenteddisk]

I have a new LED project to share I though I had brought the right thumbdrive to post pictures but didn't anyhow.. I made a (beer-can battery) if you never seen one you missed little but here it goes.

to make the required cell you will need (9 clean empty cans),(9*8inch strips of 10-12 gauge copper wire),(some self tapping screws).

to build
1)wiggle/break the open tab off the cans and force the lid part flat open.

2) strip 3/4 inch insulation off a strip of wire make a loop.use this loop as a screw hole and bend the wire in an "L"shape so one end attaches to a can by screw and the other end of the wire reaches through the drink hole in the can beside it. strip the end of the wire the reaches into the next can this is an electrode plate.

wrap all the cans in newspaper to insulate them from each other.

put all 9 wrapped cans in a shoe box and screw in the electrode "wire" .

once you have the battery built add 3ounces of vinegar and 7 ounces of water to each cell. your battery should make 4.5vdc. though it will drive a LED directly "kinda-dim",we won't use it for that but to charge another battery.

now I suggest a L-ion 3.7-4.2v @ 800-1000 mah rating. from old cellphones.
also to complete the project you will need 2- 4.5v solar cells I got mine from broken garden lights.

so here is the project idea and concept. a (thermo nuclear aluminum depletion reactor).
it depletes aluminum so if you plan to use it long you will want to replace the insulator material with say a plastic cup to catch the (pickle juice) for re-use.

I ran this circuit I made for the last month 12hrs a day, still super bright no noticeable depletion of either cans or copper wire but the alum is expected to deplete.

in short the solar cell do little to charge the battery so does the can battery but though we get all the sun has to harvest, it continues to charge at night from the can battery.

now I am using 3 (9can) cells in parallel at 4.5 volt. now and have all i need to use this light 12 hrs a night and still very bright after a month..

[iamdenteddisk]

ok so the connection is simple the solar cell connects one leg to the phone battery the other to a cds cell then to the other leg of the battery.

this isolates the solar charging circuit. the can battery circuit connects the same way with a rectifier diode in series. this makes sure current only moves one way.

"the can battery never needs charging", it charges itself as the aluminum depletes. never charge it as it will deplete copper and create a toxic gas "so just use a diode in series" with anything you power.

so you have solar circuit in parallel with the can circuit in parallel with the li-on battery.

the l-ion is only a storage tank.

"now you can build a low current LED circuit to be powered with a real nuclear reactor in your home!" imagine that..

[burger2227]

I use this to light up my wall clock for over a month on 2 AA batteries:

It is very sensitive to room lighting too so it saves battery power.

[burger2227]

Found a Stanley surge suppressor that looked promising, but disappointed inside. Here is circuit folded down:

Protection is done with 3 small fused MOV's (750 J) next to a night light bulb with photocell sensor. Red LED indicates fuse is not blown.

Upon closer inspection of the board, I decided it was a waste of space if I could move the MOV's somewhere else:

I salvaged the photocell and LED which will still be used in the MOV circuit, just not on the board.

I found a good spot for the MOV PC board under the upper ground bus. I had to grind a space out between ground holes:

I also had to cut off the right side of the PC board a bit, but left the LED resistor and LED anode (+) wiring hole intact.

After grinding the board narrower and rewiring the common(white), I slid it in and replaced the ground bus:

Now the top window is open, waiting for the new 5252F power failure, nite lite circuit.

Putty holds the photocell and LED in the openings so that I don't lose them...

The left side of the old PC board can be used to hold the high voltage capacitor, 30 volt MOV and resettable fuse.

Ready for the new circuit board and high voltage parts:

The common white is wired to the black battery wire and the yellow wire goes from the MOV board to the LED.

[burger2227]

Since the 5252F chip is the central figure in the circuit, I decided to use a stripboard with parallel copper channels:

The only extra channel needed was for the small green AC wire to rectifier and green LED supplying 1 volt DC to Pin 1 on the bottom.
I never had to cut a channel, but then again, using a board of any kind is overkill. Just needed something to hold the LED's...

Here is the final test before I button it up for the AC test. The small green wire supplies the trickle AC to the LED driver chip:

I had to chip out a bit of plastic for the capacitor I used as it was kinda big. You can get smaller ones rated at 600 volts.
The blue wire runs from the large green ground wire to the red protection status LED so that it will not light unless there is a ground.
Stanley totally ignored the ground as I have seen other surge suppressors that at least check for a good ground. SHOCKING!



I am seriously considering using ground instead of neutral for the AC common so that no ground results in no green light.

Another thing nice about this driver chip is that the AC will run the failure lights if the battery is completely dead or disconnected.
So if all three LED's come on you know that the rechargeable battery is causing the problem.
ALWAYS use rechargeable batteries! Regular batteries cannot be charged and could burn or melt

Contact me if you are interested in purchasing some LED driver chips.

[burger2227]

Another pathetic orange night light.

It actually dims too, but not very well. The light is a small bulb, not an LED. We can't have that!


My first one I made with the 2 coil transistor circuit used a V15H battery which only lasts about 20 minutes:

A V80H should last about 4 hours. It fits nicely into the battery slot I cut out. The ground bus is taped so it doesn't short
to the plus side of the battery which is + face down. The .068 charging capacitor is on the left ready for the fuse and MOV.

This time I'm keeping the wires to ease soldering. I have also ground out channels on each side to hold the green trickle and
red battery wires. I'm using a clear LED diffusion lens holder to hold the photocell off to the left side of the window.

Here is the strip board with color coding for each leg of the chip except Pin 1:

The top green row is for the trickle voltage connections of the green LED and anode of the diode to Pin 1.
The red row is for plus battery, black is negative battery and blue is for chip output to the LED anodes.


I decided to try a larger blue .1 uF capacitor that fit a bit tighter. It will give almost 2 ma charging current to the V80H battery:

There are 2 mounting openings in the window for the power failure LED's, but the charging LED is on its own.
Remember that the charging LED has the long positive anode lead going to common instead of the cathode like the other 2.

I used a copper trace board with 5 copper rows. The 5252F chip and coil are mounted on the right end.
The battery common wire had to be soldered to a black wire and then soldered to the common AC bus using the old
white wire left over from the old nite lite circuit.

The charging circuits:
The .068 uF capacitor delivers about 1.2 ma for charging and sends 1.40 volts on Pin 1 of the 5252F chip to keep it off.
The .1 uF capacitor delivers about 1.9 ma for charging and sends 1.46 volts to Pin 1 of the chip.


The power failure LED's may blink if the photocell gets ambient light from the LED's internally or externally.


The first time I tested the board, the photocell went into the hole wrong and the LED's blinked pretty fast.
That's why it is advisable to mount the sensor as far as possible from the light window.unless you like that effect...


Note: This particular 3 outlet box has part of the AC bus that protrudes up into the center of the circuit board area!
I isolated and sealed the circuit area with clear latex calking and allowed it to cure before installing the low voltage board.

[burger2227]

The $7.01 six outlet Stanley surge suppressor protection LED went out already so I investigated:

The red LED tested good with my Joule thief LED tester, but it would only flicker with 120 VAC.

I checked the thermal fuse between the MOV's and found continuity from the Line voltage to the LED resistor.
That made me replace the LED as a last resort. I also added a diode in series with it in the same direction to
eliminate reverse voltage from the 110 volts AC. That may have contributed to the LED's early demise or it was defective.

Well I paid $6 at Walmart for other 6 outlet boxes without any surge suppression so... the price went up to $7.51

[burger2227]

The 5252 Joule thief chips are now available here for $14 per hundred including shipping: http://www.ebay.com/itm/291052254553" target="_blank