Solid State Rotating Emergency Light

[Mishael]

Well i have designed and built a simulated rotating emergency light. Two actually. BUT, the only thing they do is turn on. I need a help with a design that would make each row (8 LEDs) light immediately after the preceding row. There are 6 rows per setup. The LEDs run 3 VDC at ±40 mA. Is there an IC (or several) that can be used and then a plethera of resistors to make this work? Source voltage is 12-13.8 VDC, the rows of 8 are wired in series so i really only have 6 large loads in every light assembly. By the way, it would be nice to have a variable "rotation" speed, but i dont need any patterns. just a consistent interval between 'firings'.

Then i need help with making the actual circuit. I dont know how to use PCB boards or copper sheets. Help with that would be great too

 

[Diver300]

You can use and IC called a 4017. It has 10 outputs that turn on one after the other. If you connect the 7th output to the reset input, then it will cycle round after the 6th step.

You need something to time it. Electronoize Playshop: 4093 Oscillator shows a simple oscillator.

**broken link removed** shows the idea very well.

You need a transistor for each output of the 4017 as the outputs can't provide enough current unaided.

It would be a good idea to have just two or three LEDs in series. If you have two in series, that will have a maximum voltage of 6 V. You then need a resistor of (13.8 - 6) / 0.04 = 195 ohms in series with each pair. 220 ohms is a standard resistor value, so you could use that an just get a bit less current. You can have as many groups, each with two LEDs and a 220 ohm resistor in series, by wiring each group in parallel.

There is an online calculator **broken link removed** here. However, it doesn't take any account of the variation in LED voltages and power supply voltage. For a car, where the supply voltage varies, the total of the forward voltages of the LEDs shouldn't be more than about 8 V. That way the resistor voltage will change from about 12 - 8 = 4 V to 13.8 - 8 = 5.8 V. That means that the resistor current will change by a factor of 5.8 / 4 = 1.45 and the LED current is the same so changes by the same ratio. If you have more LEDs in series, so more voltage you get less voltage on the resistor so the current changes by a bigger factor.

For wiring, I suggest using stripboard. Stripboard - Wikipedia, the free encyclopedia

 

[MrDEB]

could insert a LDO voltage regulator so the voltage stays the same with no variation. then more LEDs in each series connection could be used.

 

[Mishael]

That is so perfect! Except for one problem: I already wired and glued the LEDs in sets of 8. I tested them all with two AA's and since they were in series and they all were just as bright as if i were only using one LED. Thats why it would be nice for a voltage regulator as MrDEB stated. I am aware of that site and personally i think it is amazing. I don't understand why i couldn't just take a voltage regulator, although I'm not sure of the cost effectiveness of one.

 

[MrDEB]

You need more voltage. 8 LEDs =about 20volts at 2v drop per LED.
don't know how you got the LEDs bright enough with 2 AA batteries = 3volts??
LEDs work better in series but 8 off of 3volts?? and bright enough? Surprised they even lit up.
what LED are you using etc. and are you sure you have them in series and not parallel

 

[Mishael]

Lets try this for the third time. Heres the LEDs LITE-ON

Heres what ive got**broken link removed**

Heres how theyre connected**broken link removed**

If you cant see those try their URLs **broken link removed** and **broken link removed**

 

[MrDEB]

those are not series wired they are parallel.
Now that explains why 3 volts will light them up.
not the best way to connect LEDs.

 

[MrDEB]

according to LED Resistor Calculator
you need a 2 ohm resistor then a 4017 circuit and a timer to generate clock pulses.

 

[MrDEB]

this should get you working

using the uln 2804 seems easier than a bunch of seperate transistors.
I show only one set of LEDs
I believe you mentioned for an automobile?
PLEASE don't breakl the law using this
you may have to adjust the resistor values to suit your needs.

 

[Mishael]

I am using it on a large private property for a camp. Why is it not the best way? I dont know how i would go about connecting in series then.

 

[MrDEB]

you have it wired already , just live with it.
Its not the best method as some import LEDs are not exactly the same spec so some of the LEDs will draw a different current amount and a different voltage drop.
just go with what you have and don't worry about it.

 

[Mishael]

Oh ok. some dont like to stay on and i see why thats a bad idea. Im planning on soldering. Now, what are all the components i would need for these rows to work? I get the different ICs, but what about resistors, capacitors, etc? Earlier you warned me about breaking the law, its actually for use on a golf cart any way. I dont think i will have any law problems. Each of these LEDs is about the same and i dont think will matter much, although i defininately know what youre talking about. I have some $0.001 each LEDs that are, unmentionable to say the least.

 

[Boncuk]

you may have to adjust the resistor values to suit your needs.

He will have to adjust the resistor values because the LM2937 is manufactured for 5, 8, 10, 12 and 15V output. (no 9V type)

Boncuk

 

[Mike odom]

I am using it on a large private property for a camp. Why is it not the best way? I dont know how i would go about connecting in series then.

rotate them 90° with one anode feeding the next cathode running up the strand.

 

[MrDEB]

oups I thought a 9volt was available.
well the resistor for the LEDs for 15ma is 68 ohms at 2watts

 

[Mishael]

I tried anode to cathode and it didnt work. Ive tried it several times with LEDs and i cant get it to work. I dont understand where 9V comes in cause its 12V to 3V unless youre talking about the volatage drop

 

[Mike odom]

oups I thought a 9volt was available.
well the resistor for the LEDs for 15ma is 68 ohms at 2watts

don't they make adjustable supplies anymore? I use the LM117 with two resistors to get 9.5V on my 80W supply

 

[MrDEB]

this is for an automotive application thus a LDO regulator is the perfered component of choice IMO as well as other members here in this form. Yes an LM317 would be a nice choice but not for an unstable input voltage supply.

 

[Mishael]

im only in high school, you all lost me a while ago

 

[MrDEB]

LDO is a low drop out regulator.
some voltage regulators require about 3 volts higher than the desired voltage (usually 3 volts)
A LDO as I understand it you only need 1 volt over the desired. I may be wrong in my explanation so if I am someone please correct me.
BUT I see that regulators as I posted are specifically made for the unstable automotive use.
I remember high school. The electronics class delt with tubes. Had to build a hetrodine 5 tube radio.
can't even spell it!!