default

2013-12-19 Mechanically Rechargeable Lights

Flashlight Lighting Renewable Energy
on December 19th, 2013 by - 8 Comments

See Note at bottom.  Years ago I bought a shake flashlight and it was nearly worthless. I shook it for quite awhile, and as soon as I stopped, the LED went dim.  So how am I supposed to shake the light and try to aim it as something that needs light?  And if it wasn’t being shaken, it was dim?    No way!

Later I bought a crank flashlight and it used a motor that was identical to the ones in a DVD drive to open the drive door.  I believe it used a super capacitor about 1 Farad, but I’m not sure – it has been several years ago. In any case, the flashlight took too much effort and was difficult to charge and it didn’t put out very much light.

Last year I contributed to a “crowd funding” website for the Gravity Light, which uses a bag of sand, dirt or rocks to drive the LED for 20 minutes or so.  They have been going through the process of getting the manufacturing prototypes and testing for durability, and they should be shipping one to me sometime soon before February.  My thinking is that I can increase the time it will run by two or more times, by using a pulley on the weight and anchoring the rope to the ceiling.  The rope path will be changed from an upside down U to an N shape.  As the weight is lifted the rope will have to travel twice as far, but the weight will have to be twice as heavy.  But sand, dirt or rocks are free or “dirt cheap.”

The technology is somewhat the same but I’m hoping that the Gravity Light will be a lot more successful than the previous mechanically rechargeable lights I’ve had.

Note: I see two distinct kinds of mechanically operated flashlights, but I’m trying to name them appropriately so that the name indicates the type.  There is the mechanically operated flashlight, where the light is produced by mechanical motion.  This could be a light that operated by the squeezing of the hand, or it could have a spring that is wound up and slowly unwinds generating the light.  But the other type is different in that the mechanical action generates electricity that is stored in either a battery or a capacitor, and then this is used to make the light.  In other words, the energy is not held in mechanical device but is held in an electrical device.  Another part of this distinction is that the stored electric energy may be generated by other means such as a solar photovoltaic cell.

default

2013-12-18 10 Watt LEDs Have Finally Arrived

LED Lighting Optics and Light Power supplies
on December 19th, 2013 by - No Comments

Well, the LEDs I ordered more than a month ago have finally arrived.  They are 10 Watt(!) 900 lumens from Electronic Goldmine for $6 (USD) apiece (I checked their website and they seem to be sold out).  The reason why it took so long was mostly my fault.  They were shipped to my previous address, and of course they got sent back to the sender.  But I don’t accept total blame: they should make it more clearer where the items are being shipped to.  I didn’t see, or else it was so inconspicuous that I didn’t notice where the stuff was being shipped to.  I didn’t even remember that I had an account on their website.  When they asked to create an account, and I got ‘that account name is already taken” I realized that it was because I had already created an account several years ago, and all I had to do was log in.  But I didn’t notice anything with my address, old or new.

IMG_20131226_012245S3The window on the chip shows an array of 9 LEDs that is three by three.  This indicates that three sets of three LEDS in series are connected across the plus and minus terminals.  First I connected the LED to the power supply and turned up the voltage.  The LEDs started lighting at about 8V or so , so this seems to indicate that three of the LEDs are connected in series.  I noticed that two LEDs started to glow before any of the others did.  This seems to indicate that those two have a lower forward voltage than the rest.  It could mean that not all of the LEDs on the heatsink were properly matched.

Then I connected the power supply to a 100 ohm resistor to limit the current to the capacitor, and the 10 000 uF capacitor.  For the switch, I touched the LED’s clip lead to the capacitor.  I set the power supply to 10 volts to charge the cap.  When I touched the clip lead, the LED flashed a blinding bright white flash.  Wow, that’s bright.

I plan on using a power transistor to switch the current to the LED, and use the resistor and large capacitor to limit the amount of current it can draw.  The power transistor turns on and dumps the charge in the capacitor into the LED, and then the resistor recharges the cap.  So about once a second, the LED flashes brightly.

I need to come up with a circuit that has the high current necessary to get the brightest flash from the LED.

Continued in the 2013 Dec 26 blog.

 

default

2013-12-17 Coin Cell Prices – Vote With Your Feet!

Battery or Cell Electronic Components Other Off Topic
on December 17th, 2013 by - No Comments

The coin cells are insanely priced.  I get five of them on a card from the dollar store for a dollar or $1.50, I forget which.  Then I walk into Radio Shaft and I see them for something like $4 apiece!  I hardly ever go into Radio Shack any more.  About the only thing I buy there are battery holders, but now that I use two magnets to hold the wires to the batteries, I don’t need battery holders very often.  Except the last package of AA cells I got from Harbor Freight had non-magnetic contacts (brass?), so I had no choice.  A year or two ago I ordered a dozen single AA cell holders online and I’ve used most of them, so maybe I’ll have to go back to Radio Shaft again soon.

Several years ago I went into a Radio Shack and took a few items to the checkout counter, and stood behind some other guy who had a few items in his hand.  After about ten minutes, we were still watching the salesdroids on the phone, trying to register customers’ cell phones.  Blah-blah-blah…  The guy in front of me just lost his patience, gave up and threw all the items on the counter and walked out.  I walked back to the shelf and put the items back, and walked out.  I have only been to that store maybe once or twice, and only if I couldn’t get what I needed at another store, preferably not Radio Shaft.

We consumers have to vote with our feet, and that’s what I’ve done with Radio Shaft.

default

2013-12-12 Battery Capacity And How A Joule Thief Uses It

Battery or Cell Joule Thief SMPS DC-DC
on December 12th, 2013 by - No Comments

In late 2000 I bought a digital camera which was demanding of the AA cells, and it  used quite a few.  I decided to convert to NiMH rechargeable cells.  That saved me a good bit of money, but at that time I hadn’t begun experimenting with Joule Thief circuits.  This means that I really never had a device that used a lot of non-rechargeable AA cells.  I have a few flashlights that use AA cells, but not in large quantities like my digital camera.  A co-worker gave me a shopping bag full of about 5 pounds (2.3 kG) of AA cells that were ‘dead’, but of that, probably more than half were physically dead, with either no output or with electrolyte leaking out of them.  Over a few months last year I put most of them on Joule Thiefs using germanium transistors, and I ran them down to almost zero, getting a few days’ light from each.  They’re almost all gone now.

This means that I really never thought of a Joule Thief as a scavenger of used AA cells.  My intent was to use the JT as a light source that runs off a single new, fresh AA cell and if it so happens to run down the AA cell more than a normal flashlight, that was just a side benefit.

My Joule Thief designs reflect this: they operate best when the supply voltage is 1.5V, or sometimes 1.25V for rechargeable cells.  I read somewhere that when the voltage of AA cells start to drop, most of their capacity is used up, and only about 10 percent is left.  The Joule Thief can use this remaining 10%, but how much can it use before the voltage drops to less than needed to keep the JT running?  It has to be less than 10%.  In other words, the JT gets the cell with 10% and then the cell voltage drops until the JT quits and there is still 4%, for example, left, and the JT quits.  So the JT has used about 6%.

Let’s assume that we want to use the JT for a light.  If I use a single fresh AA cell, it will last about 16 times as long as if I use a depleted cell, and I will have to keep 16 depleted cells with the JT and change them 16 times more often.

I need to design a circuit that uses the same LED to make an A-B comparison of the brightness a JT and a LED using just a current limiting resistor. This will eliminate having to measure the LED lighting current and calculate the power. No lux meter is needed if the eye can’t detect any difference in brightness. A CdS photocell or solar cell can be used in place of the eye to detect when the A and B LED brightnesses are the same.

default

2013-12-11 3V To 9V Converter From Talking Electronics

Battery or Cell Joule Thief SMPS DC-DC
on December 11th, 2013 by - 6 Comments

I think I wrote about this circuit in my late Watsonseblog.  This circuit is essentially a Joule Thief with an added transistor to regulate the output – somewhat.  It doesn’t have very good regulation because the 6.8k is a resistor (see Note).  If this resistor is changed to a Zener diode then it regulates much better and doesn’t go as high as 10.4 V.  The Zener can be replaced by the emitter to base junction of a NPN transistor.

The emitter to base junction of many NPN transistors is typically rated at 5V, but can withstand 8 to 10 volts before it breaks down.  When it breaks down it acts much like a Zener diode.  But the voltage varies from transistor to transistor so it may require selecting one from a few transistors.

I connect the transistor and a 1k resistor in series and to a variable power supply that can supply at least 12VDC.  The transistor’s base goes to negative and the emitter goes to the resistor, and then to positive.  I cut off the collector lead because after this breakdown, the transistor’s characteristics, especially the current gain, can be permanently damaged.  Then I turn up the power supply until I measure about 1 volt across the resistor, which is equal to 1 milliamp flowing through the resistor.  Then I measure the voltage across the emitter to base.  This is the Zener voltage, and for this converter circuit, we need about 8.5V.  But I’ll explain later how to use other voltages.

The 8.5V Zener or transistor should give about 9.1V open circuit and somewhat lower than that when current is drawn from this circuit.  The regulation will be improved.  The 390 ohm resistor can be increased to 1k to  reduce the amount of wasted current.

If  the Zener voltage is below 8.5V, the voltage can be increased some by putting a diode in series with the transistor or zener diode.  The diode should increase the voltage by about 0.6V.  More than one diode may be used.  Most 9V devices can run at 7 to 8V without too much decrease in performance.  Some devices use a 5V regulator chip so 7V is okay as long as it doesn’t fall below 7V.

The circuit in TE can only put out 30 mA, which may not be enough for some devices such as a transistor radio.  The BC338 can be replaced by a higher current transistor for more output current.  Or a second BC338 could be connected in parallel with the existing one, and it should help, but not as much as doubling the output current.  I would also replace the 1N4148 with a Schottky diode such as the 1N5819 for lower loss and higher current.  Also the 100 uF capacitor on the output should be increased to 470 uF or more.  This helps reduce the interference that this circuit can generate.  I have used this kind of circuit on AM/FM radios and the AM band is barely usable because of the interference,  but the FM band is okay.  It may require more filtering to get the AM band to be usable.

The coil TE uses is a small cylindrical bar only 7 mm long.  It’s probably difficult to wind 55 turns of wire onto this, especially if the wire is thick enough to be good for 200 milliamps supply current.  I think it would be much better to use a 3/8 inch or 9 mm toroid instead, with at least 28 AWG (0.5 mm) enameled wire for both primary and feedback windings.  Using a high Mu toroid, the windings can probably be reduced to 10 and 18 turns respectively.

Two other things to consider.

One may want to change the two AA cells to NiMH rechargeable cells.  They put out only about 2.5 volts, so some changes may have to be made to get the circuit to work well.  A typical JT draws about 80 mA supply current from 1.5V, and puts out about 18 mA to the LED.  That’s 66 milliwatts to the LED.  For the TE circuit, it’s 9V times 0.03 A or 270 mW.  That’s FOUR times as much power as a JT, so it takes a lot more current from the battery.  If you use 1.5V, the AA cell gets used up quickly.  Therefore it’s much better to use two AA cells in series for 3V.

This circuit can work okay for powering lower power devices such as a DMM.  I wrote a blog about that one, too.  Mainly, the circuit is put on a diet to reduce the current with no load and with an output a load of about 7 to 10 mA.  For this low power a single 1.5V cell can be used for the supply.

Note:  With two resistors, the output voltage is divided by the ratio of the two resistors and applied to the base of the BC547.  When the voltage gets up to about 0.5 to 0.6V, the transistor conducts and reduces the output of the JT.  So the Zener effect is done by the transistor.  Problem is that transistor is a very poor substitute for the sharp turn on point of a Zener.  Using a Zener considerably improves the regulation.

Here is a link to one I made for my DMMs.

default

2013-12-10 Controlling The Light Output Of A Joule Thief

Joule Thief SMPS DC-DC Lighting
on December 10th, 2013 by - 2 Comments

In a comment, Metis asked:

How can I reliably measure and/or control the output voltage of the JT? I’m currently trying to build a small power supply to recharge a Li-ion battery and I’d prefer to be able to keep the output voltage at (or rather below) a known level rather than invest in a buck converter to regulate it.

I don’t have an oscilloscope at the moment, trying to find one that’s affordable, but until then I won’t be able to measure it directly.

[When I wrote this, I didn’t read the above close enough.  Voltage was what he was talking about.  Skip to update for more.] You can control the JT power output by changing the resistor to a pot or variable resistor.  The 1k resistor can be increased to 3.3k or much more, depending on the amount of light you want.  I would try a 50k pot, with audio taper so it gives finer adjustment at low levels.  But it will be maximum light at the lowest setting, which is at the counter-clockwise end.  I have 100k audio pots with an on/off switch, which makes it convenient.

You also might want to consider using a module that’s made for this exact purpose.  DealExtreme.com sells this type of module.  It’s a PC board that’s the diameter of the cell that goes into a flashlight (torch).  These come in various voltages and currents.  The different power levels are controlled by quickly switching it off and on.  Some of them are rated for connecting to a single 2.6V Li Ion cell, such as the 16450, or else two RCR123 rechargeable cells in series.  This makes it convenient to use any of several voltages.  you could also add it to a bike light that uses three AA cells in series.  They are typically very efficient, much better than a Joule Thief.  They use surface mount components and their cost is very inexpensive.

You also might consider getting the whole flashlight preassembled so all you have to do is mount it on the bike.  Some have adjustable beams, which can give you enough beam width to cover the road.  I bought one with the reflector that is bumpy, which spreads out the beam somewhat, and gives a bright spot in the middle.  Mine is an Ultrafire, and uses a 16450 rechargeable cell.

Update Jan 3 – Upo closer reading, I see what the issue is.  I have built and blogged a few DC to DC converters that regulate the output voltage.  Here is one.  Here is another.

default

2013-12-09 Triple Win With New TV

rechargeable
on December 9th, 2013 by - No Comments

I won three ways on  cyber Monday when I went to Costco and bought a new 39 inch Samsung TV.  It’s a lot lighter than the old 32 inch I have.

First, I already have a 32 inch Samsung, so it’s much the same as this TV.The remote buttons are not the same, but similar.

Second, all of my universal remotes work the same with both TVs; I didn’t have to reprogram them for a different TV.  Every button seems to be the same.

Also, the old original 32 inch TV remote works with the 39 inch, and the 39 inch works with the 32 inch.  What this means is that as long as the TVs are in different rooms, I can use a single remote to do whatever I want with both TVs.  IF they’re near each other, then I have a conflict because one remote will change both TVs.

Third, I went to our monthly computer club meeting and there was a box of miscellaneous items on the consignment table.  I bought several items, such as power adapters for various devices and a wireless G router.   Also in the box was a Samsung remote.  I bought it too for two bucks, and when I got it home and put batteries in it, it worked just all the other remotes.  Cool!

So now I have three original Samsung remotes that work on both TVs, and several of the five dollar universal remotes that also are programmed to work on both, too.  Talk about a couch potato!  Problem is I don’t have a couch.  I’ll have to work on that.

That is, if I don’t spend too much time watching the new TV.  It’s bigger, of course, and the picture is clearer, but the old one was adequate since I don’t have cable.  The only problem I had when setting the new one up was that when it got done autosensing all the available channels, I wanted to delete a lot of them.  But when I went into the menus, I couldn’t find the way to delete the channels.  I had to read the single sheet instruction sheet to find out that each channel has to be selected, then one or more channels can be deleted.  So I found that the menu software is not user friendly.  And if I lose the single sheet of instructions, I may not be able to ever delete channels if I forget how.  This is definitely not the way it should be.

 

default

2013-12-08 Blue Blinky Used As A Remote Control Finder

Flashers and attention getters Joule Thief SMPS DC-DC
on December 8th, 2013 by - No Comments

I got a frigid greetings by email from Kirk, where it’s a bone-chilling -20 deg. F in Winnepeg, CA.   He’s building a similar device to find a misplaced object.  I have a few other Ideas I’d like to go over.

The Blue Blinky uses a Joule Thief circuit, which works with any color LED because it can overcome the 3 or more volts that white or blue LEDs require.  However if you can use some color other than blue or white, there are other circuits that might work well.

The Blue Blinky consists of two parts: a Joule Thief and a flasher which turns the JT on very briefly.  This flasher is capable of flashing a LED by itself if the supply voltage is greater than the LED’s forward voltage.  So if the supply voltage is two 1.5V cells in series or a single 3V coin cell, the flasher circuit alone should run most colors other than blue and white.  Some green LEDs require up to 3V, so they may have to be tested beforehand.

The TE Flasher

Now, the above flasher uses a supply voltage of 3V, and works okay with most lower voltage LEDs.  But say I want to use a lower voltage LED with 1.5V cell.  How do I increase the voltage up to 2 or more volts to light the LED?  The Joule Thief is an easy way to do this.  But there is another way, without a coil or transformer.  This is by charging a capacitor across the 1.5V cell,  then connecting it in series with the 1.5V cell to give 3V.  This is what I did with the TE flasher.  The schematic shows the 100 uF capacitor.  When the BC327 turns on, it puts this capacitor in series with the 1.5V, so up to 3V is across the LED.

I have also built a few of the Blinky Boost flasher that uses two capacitors, so it can put out over 4V to the LED.  This is even more complex than a Joule Thief, but it seems to use less power and the battery seems to last longer.  However every Joule Thief can be modified to use less current, but no one has explored this method in depth, so Blue Blinky type flashers that use a JT having low current are not often found.  One point has to be remembered: a Joule Thief has a typical efficiency of 50%, which means you get less light for a given supply current, or you need more supply current to get the same amount of light.

A couple things about the Blue Blinky

I used two 680k resistors because they were easier to find than a single 1.3 Meg resistor.  Also I figured that I might like to put a 1 meg resistor in one place on the circuit board, and a 470k trimpot in the other location.  That way, I could adjust the flash rate somewhat.

Also, the 68k resistor determines the flash length.  The smaller its value, the shorter the flash duration. A longer flash uses more current.  The .01 uF capacitor could be any value down to .001 uF and it shouldn’t make much difference.

Capt. Hook’s Ticking Sound

Another thing I’d like to go over is the use of sound to locate the remote control.  If I connect a receiver out of a telephone handset between the  LED and negative, it gives a clicking noise.  The high voltage that could be generated by the inductance of the receiver’s coil can be damped by putting a resistor across the receiver.  This also lets me control the volume, so that the remote doesn’t become an annoyance when it’s near.  The receiver could be too big, so another possible ‘speaker’ that could be connected in series with the LED is an ear bud.  They are small, but they are typically low impedance, around 16 to 32 ohms.  I haven’t tried this yet, so it’s something I’ll have to experiment with later.

default

2013-12-04 Joule Thief As A Final Project For Class

Joule Thief SMPS DC-DC Lighting
on December 4th, 2013 by - No Comments

I answered a Yahoo question:

is joule thief fine as grade 12 physics final project?

Additional Details

Is the joule thief circuit appropriate as 12th class final physics project?
I have made a joule thief circuit (http://www.youtube.com/watch?v=gTAqGKt64… as 12th class’s final project. Should my high school add this in my transcript for the Universities? Will this look good?

My reply was:

I built a Joule Thief and connected three LEDs in series across the transistor instead of one.  The three LEDs were red, green and blue.  I aimed them at the same spot, and when mixed together, they gave sort of a whitish color, but it depends on how bright the LEDs are.  The idea is to get them at various distances so the color is close to white.  This illustrated that the three primary colors mix together to make white.  Also, I could put a pencil in the beam of light, and it would block each of the colors.  But since the LEDs are separated apart, there were three shadows.  Each of the shadows is made up of the remaining two colors.  This showed that green and blue mixed together gives Cyan, red and blue mixed together gives magenta, and the remaining color is red and green to make yellow.  This would make a great Physics project, and just requires two more LEDs added to the Joule Thief.  Hopefully you can aim them at a screen in a dark room and get enough light to let more than a few people see it at once.  Get good ultrabright LEDs for the maximum amount of light.

default

2013-12-02 Photoflash DC – DC Inverter Looks Like Joule Thief

Joule Thief SMPS DC-DC
on December 2nd, 2013 by - No Comments
IMG_20131202_063740BW

Click on it more than once to enlarge

I got this schematic out of an old book, old enough to still use Germanium transistors.  It uses some overvoltage protection diodes on the base.  The 9V Zener and capacitor also look like some form of overvoltage protection. This would have to be modified for a silicon transistor.

The battery says 5V, so I assume that it’s four 1.25V NiCd rechargeable cells.  Makes sense since the current draw is heavy when this thing is running.  The emitter winding is 18 AWG heavy gauge wire and that gives you another indication of how high the current is.  I will have  to try to find the Arnold core online.  I’m guessing that it’s not a toroid, probably because it would be difficult to wind the 860 turn secondary onto a toroid.

Also, notice that there are dots next to the starting end of the windings.  This means that each winding should be connected as shown, and if it is not, the circuit won’t work.  With the two windings on the left side, this is true.  With the 860 turn winding, if it is connected backwards, the output may not be as high a voltage or current, but it may put out some power.  In this case, it would be best to try it both ways and find out which puts out the most power.

One thing that I would add to this circuit is a large bypass capacitor across the battery.  I would use a 470 or 1000 uF electrolytic capacitor.

© RustyBolt.Info/wordpress
CyberChimps