SMT LED

[B2]

Hi Chewy,

Thanks. The U-tube video was informative to one who has never worried about these issues before. Looks like the LED equipment is already available, but in a format I would not choose if I did not want light coming out of the instrument (flute) at all. Key to seeing a small amount of light is that there be no other light in the room.

The power dissipated in and LED is just the product of I*V where I is the current through the diode and V is the voltage drop across the diode. The I-V curve for any diode is non-linear, but roughly for modern LEDs when not driven too hard is ~2.5-2.9 volts (depending upon the semiconductor technology). As an upper bound we could say it was going to be 3Volts. So 0.3Amp (DC) * 3 volts(DC) = .9 watts (DC) per diode. So over all then the power is simply 0.9W * the number of LEDs. The Wattage does not matter if they are wired in series or in parallel, however the current and the over all voltage does. If you want them all on at the same time then connect all 6(?) of them in series and turn the voltage up until the current gets to 0.3 Amp. The Amazon power supply units you propose to purchase have a maximum output current of 3Amps (DC) and a maximum output voltage of 30V (DC) so plenty for your 6 LEDs in series. Now, the supply too must dissipate some energy and will get warm if not hot. However, the it will not get as hot if the LEDs are wired in series (less current and more voltage). The TI data sheet does not tell us what the max power it can provide, but does say that the device itself is both current limited and thermally protected. So it should not burn up, but just shut down.

From the Amazon add we have no idea how the Amazon PCB circuit is configured ... so no idea how the chip is wired up. However, the TI data sheet says that the device has a pin, #5, to delay turn on and that it can also be used to shut the output voltage off and on. (See Table 6-1. Pin Functions and 8.2 Functional Block Diagram ). More importantly see Figure 8-2. (Undervoltage Lockout for Buck Regulator). This show the Q1= 2N3904 transistor shorting the pin 5 to ground to keep the output voltage high and turned off to turn the supply output off. It is discussed as using this to delay the device turn on, but it must also work to turn it off after it is on. If so then you maybe able to use this pin to blink the LEDs to make the light more visible.

By the way, here is another source for this board: https://www.aliexpress.com/store/1101761289/search?origin=y&SortType=bestmatch_sort&SearchText=2596 I went their site to see if I could find a data sheet about what is on the board, https://www.aliexpress.us/item/3256...7370!sh&gatewayAdapt=glo2usa&_randl_shipto=US

A circuit diagram was shown, and the pin 5 is shown as hard wired to ground to keep the supply on. I am pretty sure this is the same module you are looking at on Amazon.

If you wanted to, you could simply un-solder this pin and re-connect it to another circuit to cause the LEDs to blink.

By the way, I have purchased a lot of parts from AliExpress and for the most part have been happy with the results. However it typically takes a month (slow) to arrive from China if you use their free shipping. Some of the things you can get on their site you cannot get anywhere else!

By the way it looks like some one at AliExpress also sells something like a "Leak Light" for flutes. Sort of like you are designing. I do not know about the diameter.

https://www.aliexpress.us/item/2252799820376635.html?spm=a2g0o.productlist.0.0.7c7d25455HbWpt&algo_pvid=8fe4b545-5c74-436a-831b-9d5e9ace661a&algo_exp_id=8fe4b545-5c74-436a-831b-9d5e9ace661a-11&pdp_ext_f=%7B%22sku_id%22%3A%221000091279344%22%7D&pdp_npi=2%40dis%21USD%2124.27%2121.36%21%21%21%21%21%40210318d116648981109765525e8a7e%211000091279344%21sea&curPageLogUid=qu8j0H4NsfmG

Good luck.

Dave L.

 

[RJSakowski]

White light from an incandescent source has a fairly uniformly decreasing intensity of wavelength from infrared to ultraviolet. A typical white LED used for area lighting is essentially a fluorescent lamp with the excitation source being a blue LED rather than a mercury discharge. As a result the white color is derived from the excitation of various phosphors to create colors that, when combined, produce the illusion of white light. Whether it is "warm" or "cool" depends of the mixture of phosphors used. There are relatively dark areas across the spectrum and a measure of the uniformity of the spectrum is given by the CRI.

I went all LED when we remodeled our kitchen in 2006. I used Lumiled LED's for the canopy lighting and they have been used for approximately six hours a day for the past sixteen years. I haven't done a comparison to a fresh LED to check for a decrease in lumen output. Certainly there has been some but it isn't noticeable. I recall that Lumiled did publish aging specs for theirs.

Sixteen years ago, LED area lighting was in its infancy and efficiency was around 40 lumens/watt. Current efficiencies are around 140 lumens/watt, resulting in less heat generated. Heat is the biggest cause of a drop in efficiency over time.

I used a module called a BuckPuck for driving my LED's. The BuckPuck was available in various maximum output currents of .35 amps, .70 amps, and 1.00 amps. My design current for the LED's was .350 amps. I used the DC source version although they have an AC source version. I drove them with a 30 volt DC constant voltage switching supply. I arranged the LED's in series/parallel. I wired up to 7 LED's in series and up to 5 strings in parallel. The exact configuration depended upon the physical requirements.

Although the LM317 or LM350 is best known as a constant voltage regulator, it also makes an effective constant current regulator To use as a constant current regulator, connect a resistor between the output and the load and connect the output of the resistor to the Adjust terminal. The 317 maintains a 1.25 volt difference between the adjust terminal and the output terminal. A 1.25 ohm resistor will drop the 1.25 volts with an output current of 1 amp. Were I wiring up an inspection lamp, I would wire as many as practical in series, perhaps 8 to 10 and drive with a 317 in constant current mode. If I needed additional LED's, I would run suitable parallel strings. It is possible to run parallel strings from the same source voltage but at the low cost of the 317, I would just run one for each string.

If the OP doesn't wish the bother of roll your own, I purchased a densely packed COB strip some years back which is mounted on a aluminum backing. While that particular item is no longer available, here is a similar item. https://www.dfrobot.com/product-2498.html

 

[B2]

Hi Chewy,

I was cleaning up a bit today and came across a pocket flash light that the batteries had ruined. So I took it apart to get at the LED string. See photo. This thing is extremely bright. Attached is a photo of the parts. The Al circuit board which contains 16 LEDs buried in the strip of phosphor.. running on 3 AAA batteries (4.5volts) so is just about what you want/need? The circuit board with LED and current driver has a width of 7mm so easily fits inside a flue and you can see the length in the photo (couple of inches . After cutting it out, I hooked it up to a power supply at 4.5 volts and I found it still worked and was pulling about 0.3 Amps. If you look closely at the circuit board you can see the current driver IC that is inline with the batteries and the LED strip. It is at at the right end of the circuit board. I have taken a number of cheap Chinese lasers apart and they have the same or similar current driver IC configuration. My son originally gave me the light and I am pretty sure he got it from either Harbor Freight or a near by automotive store, but this product name is is all over the web. It has a switch at the light end and magnetic base cap at the other end, which unscrews to access the batteries. There is a pocket clip on the side. https://ezred.com/product/pocket-cob-led-light-stick/ This site says it puts out 175 Lumin. The light output is pretty much white and is bright enough that it is painful to view it.
Here is, an orange colored case, one on amazon which is probably the same light, but they list the output at 150 lumin. $9.00 on sale plus shipping ....a buy. The other colors are more $. Mine was red. Zorro seemed to also have one for $11, but the add did not show enough detail to say that it was the same flashlight.

https://www.amazon.com/Z-Red-Orange-Flashlight-Magnetic/dp/B0186NCV5Y/ref=sr_1_8?gclid=Cj0KCQjw-fmZBhDtARIsAH6H8qif2v7Ov7mBmeBRJEaHUx5yBD8VUAcBk689uBvJor5B93eZsu7iE0gaAiwcEALw_wcB&hvadid=580948228705&hvdev=c&hvlocphy=9005929&hvnetw=g&hvqmt=e&hvrand=1717240088160990520&hvtargid=kwd-297175175469&hydadcr=1393_9901984&keywords=ez%2Bred%2Bflashlight&qid=1665091820&qu=eyJxc2MiOiIzLjA0IiwicXNhIjoiMi43NyIsInFzcCI6IjIuMjAifQ%3D%3D&s=hi&sr=1-8&th=1

EZRed® Pcob - 175 lm Red COB LED Pocket Light

175 lm Red COB LED Pocket Light - Part Number Pcob by EZRed. Available in Work Lights Department at www.toolsid.com

www.toolsid.com

Anyway, my guess is that it is all that you would need and could be powered from batteries if you wanted to do so. You could just stick it in a clear plastic tube for insulation from the instrument.

I was not hard to get apart, but was glued together. Just cut a little and then insert a sharp screw driver near the base end and start breaking. The unbroken light at the top of the photo is a different brand, but is similar in shape. Its LEDs are individually package but is also bright. However, I doubt that the LEDs/circuit board would be as small.

I used this to stick to my lathe bed via the magnetic base and point the light right at the point of cutting. Of course it got all oily and dirty, but worked great. I just forgot to take the batteries out..... all too common an event.

Think I will order a replacement!

Dave L.

PS, The reason I took the lasers apart was to remove the IC. I then built my own current driver so that I could control the current accurately at various current levels. This was needed for the optical experiments I was doing.

 

[Mark Lossner]

Purchase a switching power supply from some hobby supplier like Marlin P. Jones: 15V 20amp. There are smaller ones as well.

 

[Chewy]

Update! Thought I would share this with you. This is the smoke generator. It is used to find pinhole leaks in musical instruments. My thanks to B2 about the model trains! The light bulb went on and I went to my local model train shop and got a 6 ohm heating element for the train. After building it used baby oil for smoke. Don't ever do that!!!! That stuff makes you gag and the stink lives on forever. Another trip back to the train shop bought oderless smoke. On the test Clarinet, my wife had spent a couple of hours trying to figure out what was wrong on a repad. Just didn't sound right or blow easily. One shot with the smoke generator and she found 3 pinhole leaks in the pads. 10 seconds. She was sold! Couldn't fix them so she replaced them a second time around. The clarinet in the movie has a pinhole leak in the bottom trill key, all the way at the bottom left. Too small to show, so I took the plug out and you can see the smoke blowing across the glove. I did use the LM2956 Buck blocks for regulation. At $2 each, too cheap to do a circuit.

Led's are sitting on bench. Bench motor is in progress, plenty of discussion in another post and the Magnehelic tester is next.