TIP127 current calculation....

[4pyros]

its not scrolling just flashing...

So you can still use multiplexing and run off one pic. Its not just for scrolling displays.

 

[audioguru]

I have some Lumileds Luxeon Superflux LEDs that have 4 pins to send the heat to the copper on a pcb. Their maximum allowed current is 70mA and they are very bright over a wide angle.
Here is a photo.
Please post the datasheet or part number of your 150mA LEDs.

 

[large_ghostman]

I still dont get why you dont, just put a resistor on each string, give yourself plenty of head room, you dont need max brightness. You can afford to drop the current a fair bit before you really notice much change in there brightness, then once you have set maximum brightness, just use pwm on say all the cathodes at same time to adjust the brightness down.
I assume this is for one of your products that you sell? Personally I wouldn't mess about, I would use as many resistors as needed and go for reliability, yours is a new business, dont take risks with getting a name for poor quality and reliability. Space shouldn't be an issue if you use resistor arrays or even smd resistors, cost is minimal and worth the price to make the product reliable, also factor in the cost of development time , you have probably spent way over the cost of using resistors already, if you factor that in.
No offense OP, but you give the impression that you are approaching a commercial product with a hobbyist approach. But as always I dont always fully understand what you intend so i might have got it all wrong, not your fault, I just struggle sometimes interpreting what you say, others here seem way better at it

 

[large_ghostman]

I have some Lumileds Luxeon Superflux LEDs that have 4 pins to send the heat to the copper on a pcb. Their maximum allowed current is 70mA and they are very bright over a wide angle.
Here is a photo.
Please post the datasheet or part number of your 150mA LEDs.View attachment 83159

And I bet each one costs more than his entire project I had some and they are ace but pricey

 

[audioguru]

And I bet each one costs more than his entire project I had some and they are ace but pricey

I got mine for free. A package of 100 Lumileds Luxeon SuperFlux red LEDs arrived at my home with a note that said, "Thanks for helping me". I helped him with his project on a website forum.

 

[MrAl]

Hi,

I used one of those LED's in a uC refrigerator monitor circuit that monitors the temperature and shows the temperature differential in 'blinks' corresponding to the temperature differential between the actual inside temperature and some fixed temperature like 40 degrees F. Mine is a multi colored LED however, blue green red, which allows mixing for some interesting effects. The colors dont mix that well but they make a really nice indicator as each color is used for something else. For example, green blinks means the temperature is below the fixed level, and red blinks means the temperature is above the fixed level. If the temperature is exactly at the fixed level then it blinks white once only. This happens about every 10 minutes which makes the battery last for 2 years.

The LED colors can be pretty bright, although i run mine at fairly low current relative to the max for the device for long long life.

 

[audioguru]

I soldered 36 red SuperFlux LEDs on stripboard with 9 current-limiting resistors. The LEDs used 53mA each. I mounted them in the plastic case of a compact cassette tape (remember them?).
It was a night-light that was way too bright. The heat from the LEDs crazed and yellowed the clear plastic of the case even though I had many cooling holes top and bottom and tall feet.

I bought some cheap Chinese flashlights as Christmas gifts. They have 24 white LEDs on one side and 3 white LEDs on one end. They came powered by 3 Super Heavy Duty AAA cells (they are not super and are not heavy duty). The flashlights cost 4 bucks so I paid for the batteries and got the flashlights for free. They are very bright and my flashlight has been used for many hours and is still bright.
I wonder if the LEDs will burn out soon if I use name-brand alkaline battery cells?

 

[large_ghostman]

If it does AG and you need help fixing it give me a shout

 

[MrAl]

I soldered 36 red SuperFlux LEDs on stripboard with 9 current-limiting resistors. The LEDs used 53mA each. I mounted them in the plastic case of a compact cassette tape (remember them?).
It was a night-light that was way too bright. The heat from the LEDs crazed and yellowed the clear plastic of the case even though I had many cooling holes top and bottom and tall feet.

I bought some cheap Chinese flashlights as Christmas gifts. They have 24 white LEDs on one side and 3 white LEDs on one end. They came powered by 3 Super Heavy Duty AAA cells (they are not super and are not heavy duty). The flashlights cost 4 bucks so I paid for the batteries and got the flashlights for free. They are very bright and my flashlight has been used for many hours and is still bright.
I wonder if the LEDs will burn out soon if I use name-brand alkaline battery cells?

Hi audioguru,

Wow cassette tapes, i thought i was the only one left on the planet that still had some ha ha.

I had quite a few Chinese knock off flashlights go on me, the LED's would start to burn out one by one. Even worse, the LED's would first start to blink on an off and that would be very annoying when trying to see something important.

One was a name brand flashlight so i was surprised this would happen. It was the only one i cared enough to look into and i found that they were driving the LED's at 50ma. These were the small 20ma white LED's that we all know and love, and they were using 50ma through each LED so they could get the brightness. Of course that is way too much current for prolonged use, so it the light was left on for a while one LED would start to blink on and off and if left on longer more would follow. I ended up breaking the LED's off with a large pliers to leave only the good ones, but eventually they start to go too so i replaced the whole bunch of them with a Luxeon Star high power LED with appropriate limiting resistor. It's been working ever since of course, but what a pain.

So the moral of the story is if it looks cheap and it's bright, then check the current level. If it is more than 30ma expect problems (20ma LED that is). They can take abuse, but not 50ma of abuse for a 20ma LED.

They might be using those heavy duty batteries so that there is more voltage drop as you already thought of, so when going to alkalines there will be less voltage drop and thus more current. The difference can be quite a bit too, so what i would recommend is if you really like these lights then load in some alkies and then turn it on and check the current with a good low series ohm meter or shunt. If it is more than 30ma per LED then it could end up blowing the LED's over time. It may take a while of run time though, one of my lights did not blow right away it took a few uses of prolonged use to start seeing the blinking.

But all it takes is a little more resistance in series with the battery as im sure you already know, so the only challenge is to find a home for the new resistor and make sure it can stay cool enough to last a long time.
For my 'good' light, i mounted the new resistor in the head and left the clear bezel off so that it gets good cooling from air just outside of the head. Seems to work pretty well as it has been in use now for some two years or so without a problem. Dropping is another issue though, so the resistor has to be solidly mounted too.

Good luck with it.

I bought some cheap $1 lights a while back and they work great for a little while until the LED's start to blink, but i find that if i dont use them for prolonged periods (like only a few minutes at a time) the LED's stay working ok. It's only when they run for a longer time that the LED's heat up too much and start to burn out with the tell tale blinking...which is worse than if they just burnt out entirely with no light output at all.

 

[large_ghostman]

We had a large expensive torch that was rechargeable, it ran at 18V and was really heavy. I think it cost nearly £80, we had it 8 weeks then one day while on charge it caught fire! this was in the old outside wooden shed we had, near a hay barn. The shed caught fire but not too bad. Mum wont let rechargeable torches in the house now.

 

[audioguru]

You talk funny over there. (I can't find smilies here anymore)
A TORCH is a fire, isn't it? Over here we use an electric flashlight.

 

[MrAl]

Hi,

The word 'torch' among flashlight aficionados simply means 'flashlight'. I never adopted it myself but i accept the fact that there are many people out there that for some reason really like calling flashlights torches.

Before i ever heard of that which now is maybe some 10 years ago i called something that produces a controlled flame a torch. That's something that usually has a propane or other fuel tank and produces a fairly hot flame, so it was never a flashlight. But now we have to be aware that when some people say 'torch' they are really saying 'flashlight'.

If this behavior keeps up eventually every word in the English language will mean exactly the same thing <chuckle>. Reminds me of a South Park episode where some space aliens that landed called everybody and everything a "Marklar" which was funny.

 

[JimB]

You talk funny over there. (I can't find smilies here anymore)
A TORCH is a fire, isn't it? Over here we use an electric flashlight.

These fine fellows in the picture have torches, burning brightly so that they can see where they are going.

(Picture copied from the Shetland News website.)

So I guess that if you consider the function of the item, that device with an incandescant lamp or an LED which one uses to find ones way in the dark, could also be referred to as a torch.

JimB

 

[audioguru]

The Olympics is an International sporting event and it is begun with an athlete carrying "an electric flashlight"? I don't think so. The athlete carries a burning torch.

EDIT: How did I know that Ritesh would not come back?

 

[koolguy]

Hi again,

Ok so your LED strings draw 150ma maximum, and how many strings do you plan to use?

Also, so you only want to flash the LED's right, not adjust their brightness once the circuit is set up?

there will be at least 15 i.e. 15x150mA= ~2.5Anot controlling brightness..

here is oval led..
https://img.diytrade.com/cdimg/974467/9957134/0/1249291141/5_2_x_3_8mm_Oval_LED_Lamp_Series.jpg

https://www.google.co.in/search?q=o...board&rls=org.mozilla:en-US:official&tbm=isch

 

[audioguru]

Good, you came back.
You did not post the datasheet for your oval LEDs saying that they will survive 150mA continuously. If you flash them fast enough then their average current is 75mA.

 

[rumpfy]

Hi AG,
you guys talk funny too;
You put gas into the gas tank and we put gas into the gas tank and petrol into the petrol tank; then we drive off with our petrol tank full and the gas tank full.
Post 55 is a good enough spec, nes par/
Doesn't have too many confusing numbers

 

[audioguru]

Barbeques and taxi cabs here burn a cheap gas called Propane. Most cars here use gasoline which we call "gas". Gasoline is refined "petroleum".
In some countries gasoline is taxed too much so their vehicles burn stinking and smoking diesel unrefined pertroleum. They also drive on the WRONG side of the road. (smilie)

 

[MrAl]

These fine fellows in the picture have torches, burning brightly so that they can see where they are going.
View attachment 83191
(Picture copied from the Shetland News website.)

So I guess that if you consider the function of the item, that device with an incandescant lamp or an LED which one uses to find ones way in the dark, could also be referred to as a torch.

JimB

Hi,

Thanks for the pic <chuckle> that clearly illustrates them using torches to see with.

At night you can see with a flashlight and you can see with a torch. That does not make them the same thing, and i am not saying that you are saying that im just pointing this out. Otherwise i just said, "At night you can see with a flashlight and you can see with a flashlight" which would be kinda silly.

So basically we have to derive the meaning not from the word anymore but from the context as well. If you ask me that makes it a little more difficult to understand when before we started using the word 'torch' to mean flashlight we didnt have this extra language translation step.

For example, in the following sentence:
"I wanted to go on the cave diving expedition, but the batteries in my torch went dead so i had to stay behind"

Now what exactly is this guy saying Is is saying that the batteries in his flashlight went dead so he had to stay behind, or was he saying that the batteries in his electric start flame torch went dead so he is not able to light his torch when needed so he had to stay behind?

So this is what happens when we start using the same words for things that were not originally called that.

Granted though this is an extreme case as usually it is easier to tell, as in a flashlight forum where people are talking about their 'torches', we assume they mean flashlights. So i am not rejecting it entirely just pointing out the differences. Also though, when i hear the word 'torch' i first think of something HOT as well as being able to produce light. Most flashlights get a little hot yes, but nothing near as hot as how hot a real flame torch gets.

 

[koolguy]

Here is similar oval led **broken link removed**