LED flasher

[Broz]

I have just obtained some high intensity LED's. I want to use two pairs of them and flash them alternately. I want one pair to flash 3 times in about 1/2 second, and then the other pair flash 3 times in about 1/2 second, and alternate back and forth like that for about 5 cycles. The actual timing is not critical as this is for visual effects. I have a couple ideas myself on how to do this, however I need a circuit that uses as few components as possible. I'm afraid my ideas might have too many components. I want to drive the LED's with about 500mA, as they are high intensity and can take that current. My goal is to use as few components, and consequently as little space as possible. Any suggestions would be appreciated. Thank you.

 

[Hero999]

Your best option would be a microcontroller.

You could do it using sequential and combinational logic ICs but it isn't worth the expence, soldering and space, unless you're just doing it for educational purposes.

 

[Broz]

I was worried, but not afraid you would say that. Microcontrollers are currently out of my league, though I have wanted to learn how to use them very much as I know I can use less components for my projects. I know what microcontrollers are, what they can do, I know analog and digital circuits, but I've yet been able to read what I need to learn how to program and use microcontrollers. I really want to learn how to use them, however, time is short and if I can get around that obstacle for now using another type of circuit for the time being I will. That said, if I must use a microcontroller for the ease of saving space, I will put my education on overdrive to learn how to use microcontrollers. Do I have any other options that will involve a minimal amount of components? I'm using SMD's for the first time to save space, and I'm willing to dedicate about 10 square cm for the flasher circuit. Thanks for the reply Hero.

 

[Broz]

Upon further contemplation, I think the microcontroller is the way to go. Still, because of time constraints, any other ideas are apprecaiated. I have about 700 dollars U.S. and about 60 hours in the next month to learn how to use microcontrollers. If I can avoid it, I will. However, I see I might just have to bite the bullet and learn about this, which I've wanted to do anyways. I'm your willing, and even better, financed, student. What do I need to make this work? Thanks again.

 

[Diver300]

My suggestion is a 74HC132, quad nand schmitt. You might two.

One gate of that will oscillate with a mark space ratio close to 50% with just a resistor from output to both inputs, and a capacitor to ground from the two inputs.

You can use one gate to oscillate at 6 Hz, while the other oscillates at about 1 Hz, and some of the gates can be used to combine the signals to give you what you want.

I would agree that a microcontroller is the way to go, but I also know that there is a lot to learn to get one to work.

The 74HC132 is far less capable, but it will oscillate with two passive components and no programming.

 

[HarveyH42]

60 hours is plenty of time to get the minimal amount of stuff together for programming a microcontroller. If your computer has a parallel port, you can but a very cheap programmer. Most tutorial site, start with simply flashing an LED. The program you want for the police-style flasher would literally take minutes to write for most of these experienced guys. An 8 pin device would work well for this, but you will need some external descreets, voltage regulator, capacitors, transistors to drive the LEDs, bias resistors, and current protection for the LEDs. Not sure how big 10 cm square, but doesn't seem like a lot of space for logic chips.

 

[Torben]

Does Broz have 10 cm square to work with? He said 10 square cm to start with.

10 cm square would be plenty, I'd think. (3.9" x 3.9")


Torben

 

[fingaz]

I think this may be what you're after. You may need to alter the values of the resistors / capacitors to get the timing cycle you want.

You can use just about any small NPN in place of the BC107

The output of the 2nd and 3rd 555's (pin3) will supply up to 200mA, use them to drive a suitable NPN transistor if you want higher current.

I built one of these a while ago on a 7cm X 3cm stripboard, so size shouldn't be a problem.

Edit: If I've made any mistakes in the schematic, I'm sure someone will notice and correct me.

 

[audioguru]

Pin 4 of the top 555 needs a pull-up resistor. 10k is fine.

 

[fingaz]

Pin 4 of the top 555 needs a pull-up resistor. 10k is fine.

Thanks. Knew I'd miss something.

 

[Broz]

Sorry, looks like there was a miscommunication. I have 10 square centimeters to work with. That's why I'm thinking even with the smallest surface mount stuff using 555's won't cut it. Using 555's was my first idea, but space is at a premium for this project. I might be able to go up to 16 square cm but that's pushing it. That's why I'm thinking I might have to finally learn microcontrollers to make this work in the space I have. I should see if I can actually fit three 555's and the other componenents onto such a small board. As it is my first time using surface mount stuff, going this small will be pushing my skills.

 

[Nigel Goodwin]

Yes, you need to learn micro-controllers, a 10F series SM PIC should be ideal for you, and keep it nice and small.

 

[Broz]

Thanks for all of the replies. Nigel I see you have a tutorial website on micro-controllers. I understand you may be biased, and that's ok, but do you think your tutorial is the quickest way for me to learn what I need, and then expand from there? I see in your tutorials you have an LED flasher, IR communication, and PWM projects. These are all the types of things I'm into. To learn what I need for this project, and also expand that knowledge to my other projects later, what do you estimate my costs to be? I'll probably start this week once I figure out what I need to order. For now I'll read through the tutorial to try to get a feel for what it's going to take. Thanks.

 

[Nigel Goodwin]

Programmer wise I would suggest getting the Inchworm or Inchworm+ kits, they are reasonably priced and well featured.

Everything else you need is in my tutorials, the parts required are only low cost.

As for 'biased', yes I am biased towards making things cheaper, smaller, and better

Your triple 555 circuit would be just a single PIC, and hardly any other components.

 

[Hero999]

Incidentally, you can buy quad 555 ICs (LM558) which you could use if you wanted the 555 timer option but you're better off with a PIC.

 

[martjo]

Hello, to everybody. At first I want to excuse me for bad english
From a long time a go I want to find a electronic circuit like "Safety car - F1" flashers. Is anybody can help me to find circuit of this kinde?
In advance, thank you!

 

[Gordz]

You should be able to create the unit within your 33mm x 33mm area if you use SMD parts. If you are driving the LED's with 500ma each then you will need a 1.2 Amp (min) switching regulator and some FET's to drive them. How high can the solution be ?

 

[Hero999]

500mA?

You need some pretty chunky LEDs, 350mA units might do if you only want short bright flashes.