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LED flasher does not work need help.

alec_t

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Most Helpful Member
#21
I tend to believe that the TINA simulator is somewhat less than ideal, at least in this case.
Perhaps. It simulates fine in LTspice.
 

unclejed613

Well-Known Member
#22
The schematic is somewhat uniquely drawn, particularly the rectangular transistors - note the arrowheads outside the rectangle indicating the emitter.
yeah, that's an odd schematic symbol. did they invent that symbol or are they looking at some ancient textbook from before transistor symbols being standardized? it's similar to the "alloy junction" transistors from the mid 1950's
 

alec_t

Well-Known Member
Most Helpful Member
#26
Going from 1Hz to 2Hz is speeding things up!
You need to reduce the duty cycle, rather than the frequency, to increase battery life.
 

JonSea

Well-Known Member
#27
The LEDs flash back and forth, yes? One of them is always on in this circuit. Changing the flash rate won't change the load current. Nor will changing the duty cycle when one LED or the other will be on.
 

gary350

Well-Known Member
Thread starter #28
What I should have said, change circuit form 1 blink per second to 1 blink every 2 seconds.

YES your right 1 LED will always be ON no matter what flash rate is.
 

gophert

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Most Helpful Member
#31
Gary, I feel your frustration...

This particular circuit has had me flummoxed for years (yes, YEARS!)!! :banghead::banghead::banghead::arghh::arghh::arghh::woot::woot::woot:.

IT HAS NEVER WORKED! Either as a sim (both LEDs ON, no flash). 0r as a real ckt on a bread board.
View attachment 116103 (Texas Instruments "TINA")
That very same circuit here.

What am I missing (if anything)?

And, yes, I have changed component values just to make sure that my math skills haven't gone kaflooey...

Anybody else care to comment?
When you click on the component in Tina, to adjust parameters, I think you can set an initial value. Try setting the initial voltage of one cap to 1/2Vdd (3v for a 6v power supply).
 

cowboybob

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#32
Thanks a ton, gophert!!

That did the trick. So did making one of the 10k resistors 5k. But that, of course, created an asymmetrical timing situation.
 

audioguru

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#33
200 flashing LEDs for $2.00 is one penny each. They are so cheeep that I wonder if ANY of them will work.

Will a flashing LED blow up if you do not limit its current with a series resistor?
What is its recommended and absolute maximum voltage?
Please post a link to its datasheet for us to see or post a video of it blowing up.
 

gary350

Well-Known Member
Thread starter #34
200 flashing LEDs for $2.00 is one penny each. They are so cheeep that I wonder if ANY of them will work.

Will a flashing LED blow up if you do not limit its current with a series resistor?
What is its recommended and absolute maximum voltage?
Please post a link to its datasheet for us to see or post a video of it blowing up.

Here are the LEDs I ordered. I made a mistake on the price they are $1.83 per 100. I ordered 200. OH poop.... I just noticed $1.99 postage. OH WELL no big deal. Multi color I only want about 30 RED, there is probably 1/3 of each color.

I covered an RC model airplane with Red LEDs once so I could fly it after dark. I was only able to fly it before it was totally dark. After total darkness the airplane was very hard to see most of the light is on the tip end. It would have worked better with bright white lights.

https://www.ebay.com/itm/100-200pcs-3mm-RGB-Slow-Flashing-Flash-Blink-Red-Green-Blue-LED-Leds-Light-New/253950100171?ssPageName=STRK:MEBIDX:IT&var=553270063607&_trksid=p2057872.m2749.l2649
 
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JonSea

Well-Known Member
#35
LOL. The LEDs you've ordered aren't a collection of red, green and blue LEDs where you can sort the red ones from the batch.

They are RGB LEDs, where there are red, green and blue LED elements inside each LED. These are controlled by a chip inside the LED to flash various colors - red, green and blue obviously, but also purple (red and blue elements both on) and other colors resulting from the various combinations.
 

JonSea

Well-Known Member
#36
Will a flashing LED blow up if you do not limit its current with a series resistor?
People have had good success connecting LEDs directly across coin cells like 2032 cells without current limiting resistors - the cell's internal resistance limits current to a safe level.

Not sure how long the LED will be illuminated in this case.
 

audioguru

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Most Helpful Member
#39
Most of my solar garden lights use an RGB LED that changes its colors. The circuit that powers them steps up the 1.2V from an AAA Ni-MH rechargeable cell and limits the current. I never tried blowing one up by connecting directly to a battery.

Since the maximum allowed voltage of the Chinese LEDs is only 3.6V then they probably need a series current-limiting resistor and will not light up with a 3V battery that drops to 2V.
 

audioguru

Well-Known Member
Most Helpful Member
#40
The RGB colors changing LED on a solar garden light a minute ago measures 2.1V for red and 2.4V for green and blue when the battery is weak. It measures 2.4V for red and 3.1V for green and blue when the battery is charged. The red might burn out if you power it directly from a 3V battery.

A CR2032 battery is rated for 0.19mA but might be able to provide 20mA for a few minutes with its voltage dropped to 2.7V. Soon its voltage will drop to 2.3V when overloaded with 10mA.
 

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