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S.O.S. LED Flasher Schematic Diagram Answered

'Hello everyone,
I looking to find an electronic schematic of a small LED flasher circuit that
flashes an S.O.S. light code. 3 short flashes, 3 long flashes, and 3 short flashes, than a 5 or so second delay, than repeats.
Hoping to us a 555 timer IC.
This is for a science project for my 14 year old.
HELP! Thanks.




9 years ago

Hallo dudes.....these days i built the same project with a high brightness LED that flashes according to SOS code. I have some critical limitations.... 1 first of all the whole pack is an orange floated torch light according to Navy ordinant for safe regulation for boats and small vessels. 2.In this small space i will place 1 flashing LED in SOS code, 2 button Cells , a solar panel to recharge the batteries, ALL THESE must fit in about 200cm3 3 Now we have around the same space and little more left to put some survival stuff. Like a small knife, small bottle with water, fishing line and 3 hooks, some rope, candle and matches. The torch lite in out side has an O ring so i put an whistler and a bigger jack knife. I decided to built this special lifesaver torch light because my wife she affraids the sea (she had experienced a bad shipping sunk some years ago) I think if can can i place a small GPS signal also... Once i designed a circuit of SOS code with 3 chrono reset circuit based in 3 indipended identical circuits using three 555 and 3 corresponded relays and one forth for the output of the whole circuit The basic problem is that tis circuit is very big so is not affordable for my available small place


9 years ago

That's not a very realistic project without a lot more constraints and/or a lot more time. What have they been learning about? Are their tools/components at school, or that they're supposed to use? The sorts of things you'd be looking for aren't easily pulled form old electronics (except the spinning disk idea. That's not bad...) Here are some thoughts:
1) Use a microcontroller. An arduino or Basic Stamp will do this pretty easily; I think you can even get the basic stamp at Radio Shack. About $50, IIRC. With better tools, you can use an under $1 microcontroller. A cheap arduino clone is about $12, but mail order might not get it to you in time.
2) I think you can do it with several 555 timers, or two timers and some logic chips. The first set gets cascaded to create output signals "slow" and "off" that drive an additional 555 that is blinking. Arrange the timings so that it blinks three times, then is slowed down for three blinks, blinks three more time, and then repeats that pattern while the "off" signal is on so that you get the delay. This is similar (identical?) to guyfrom7up's method. One signal to control on/off, one to do fast/slow, and one for the blink itself (modulated by the second.) i suppose not all the timing has to be 555 based.
3) You can use a 555 to drive several (looks like at least 3) cd4017 style decade counter/decoders. These chips with consecutively drive 10 outputs. Use "wired or" logic to drive the LEDs like:
0000000000 1111111111 2222222222   (count upper digit)0123456789 0123456789 0123456789   (count lower digit)0101010110 0110011001 0101000000   (1 outputs tied to LEDs.)-short- ---long--- -short- pause-

how would you switch between caps? what i was thinking of was an external rc network that, when it fires, energizes the base of a npn transistor and that in turn adds an extra cap from pin 2 to ground. the problem- i have trouble with caps.

WTH, i replied to your post and it says you posted after me.

lol, I have a kit (from my tech-ed teacher) of a circuit that switches between 2 leds, all it consists of is 2 transistors, 4 leds (2 go on at the same time), 4 resistors, and 2 capacitors. I'm having a real tough time converting the pcb into a schematic because for some reason it's not all lining up.

lol. but doesnt one type of led need to be on longer than another?

wait, the capacitors control the timing, so it should still work. we need an edit button. also, we have negative post times again!

here's the schematic for the blinky, to control long and short you just control the 2 capacitors... ahh crap. This alternates between long and short then.... well, below is the schematic if you ever want alternating leds... well, you could have 5 independent 555. you could use a main 555 to decide wheather the leds can or cannot be on (whenever I say they can be on, i mean they can, but they don't have to be on). That 555 determines the delay. When that 555 is on it turns on another 555 that essentially does what the previously descibed 555 does, just faster (half the time it turns on, the other half it's off). Branching off of that 555 is another 555. when power is supplied to the 3rd 555. it turns on for half the time, and it's off for half the time. When the second 555 is off it.... I'm sorry, that paragraph is getting terriably complicated. basically you could achieve the sos thing by having 5x 555 IC's cascading off of eachother. It would be terriably complicated. Here's a step walkthrough of what I'm saying: 1) 555 timer A is on for half the time, off for half the time, giving the 5 second delay effect. 2) when 555 timer A is on it supplies power to 555 timer B 3) when 555 timer B is on it supplies to power to 555 timer C 4) when 555 timer C is on it produces 3 short pulses to LEDs 5) when 555 timer B is off it runs 555 timer D 6) when 555 timer D is on it produces 3 long flashes to led. 7) 555 timer A turns off and the whole thing resets. I think I may be missing a step or something

hi guyfrom7up, can you post me a link with this schematic ?? much appreciate for your time

scratch that, you could use 4 555 timers, not 5, my step through is still valid for i only use 4 555's

no way, my way only uses like 20 different components intricatley hooked together, it's so simple! lol

when your done gripping about my better circuit, do you mind helping me with the r/c network to switch in the other capacitor?

i don't think the person needs help anymore, considering it's over the deadline...

in his latest post, he says that the deadline was extended by about 1 week.

I think you could use the quad 555 IC for this, if you use the trigger pin, but I've never done that so i dunno. If you use 4 independent ones then you use the power supply pin to turn on and off. You need to throw in some diodes or something.

WELL, I have Good news and Bad news: The Bad news: The teacher is out sick until further notice. The Good news, all the students have been given another week.

I think I might be able to come up with something. Here's the plan: You run a 555 in astable mode, controlling when the led can be on and when it cannot (the led can be on during the flashes and the spaces, but it can't be during the 5 second pause). When the led is able to turn on you can use a circuit using (i think) 2 resistors, 2 capacitors (of different values for short and long pauses), and 1 led for the output. I'll draw up a schematic soon

Cannot use a switch to switch from DOT circuit to DASH circuit.
Once power is initially applied, LED's should light----Dot Dot Dot Dash Dash Dash Dot Dot Dot---off and than repeat.

then it becomes even more complex. youd need a second rc network or something similar to add in and extra cap on the 555 then remove it later. ill get guys help and we will try to figure something out.

he only has till monday; no time to get a microcontroller. lets see now...................... 555 in astable................ how to chnage pulse lengh?............. duh, rc timer ................ okay, heres the theory. the 555 in ashtable sends regular pulses based on an EXTERNAL resistor/capacitor network. so by sending three pulses, then changing the network, you could make dashes. are you allowed to use a switch to change from dots to dashes?


10 years ago

I could imagine how to build this from two 555s and some logic gates, but a microcontroller would be far easier - and far more versatile!

I'm sure someone who knows more about microcontrollers will be by soon.

Paging Mr. westfw... paging Mr. westfw...

Thanks, I'm hoping that someone very knowledgeable in electronics. My son only has till Monday.

Does he *have* to make an SOS flasher? Or can he still pick a different topic?

Doing this by Monday - including learning about microcontrollers, getting all the components etc. - would be very ambitious.

A far simpler solution would be to rotate a little cardstock disc in from of a lit LED, with holes punched out of the cardstock disc to create the SOS pattern. That, you could probably rig up in an hour, from materials you already have at hand...

Yes, the requirement is that you use 4 LED's that flash the S.O.S. The electronic components are no problem, I have a lot of old non working pieces of equipment to pull the parts from even if I have to stay up all night to do it, plus there is a Radio Shack across the street from me for the parts I don't have.