how do I dyi blinking led's?

I've been using a Garrity 3aa headlamp on my bike helmet for a few months. It's great with the dual modes I can put the red led on battery pack and two front red led's on blink, and control the main spot high - mid - (low) - off, as needed.
But the time has come for me to make my own. And I realised I dunno how to do the blinky thing. What I'm thinking of is a separate system (power, switch, controller, 3mm or 5mm emitters recessed in the vents of the helmet) as I will most likely be revamping or swaping out different mains. Or do I just run a separate set of wires off the battery pack for the blinkies. Say two led's (any colour) in the front, two red led's in the back). At present my fall back idea is to gut a dx blinker and re-configure the peices to suit.

Any / all guidance / suggestions for a blinky system much appreciated.
L

What about using one of these?

Hrm, that's really interesting. Solves the whole driver problem. So I'd go powersource, some un-known resister, wiring to led's in series. Be interesting to see if they'll syncronize.

This CMOS 555 circuit for a bike light is what I have used for a rear tail light. It runs forever on 2AA cells, and is incredibly bright if you use quality red LEDs like these super bright red 5mm LEDs. I only used half of the circuit shown, and it is visible for a long distance.

I am going to build another using all SMT components, and will concentrate on making it super compact. For such a few components, it is a real winner. You could even add a potentiometer to vary the flash rate.

For simple blinking, using 555 timers would be the most straight forward and easiest way to go. If you plan to drive LEDs more than just a few regular LEDs, remember to calculate the total current and add proper driving transistors.

Depending on how fast they need to blink, you could experiment with PTC (positive thermal coefficient) fuses. This is basically how some blinking xmas tree lights work. No IC required. Just put the fuse in line with the lights.

The easiest way is to use a LM 3909 flasher IC. Only 4 parts including the battery. I can sell you one or you can buy them on Ebay. PM me if you have questions. http://datasheet.digchip.com/321/321-3-066575-LM3909N.pdf

Very glad you posted. That LM looks exactly as simple as I hoped this would be.
I may PM you.
Thank-you.

Feel free, a very versatile circuit, I've had one flashing off and on for probly 20 years.

MarNav1 said:

The easiest way is to use a LM 3909 flasher IC.

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How do you adjust the flashing frequency, and the duration of the "ON" status?

Capacitor size. The schematic calls for 300 which is an odd size. I use 330 or 470.

MarNav1 said:

Capacitor size

Click to expand...

This is only one parameter. I want to be able to adjust two parameters: the frequency, and the duration of the pulse. Unless the on/off ratio cannot be adjusted, and is preset to a certain value by the IC (e.g. on = off)?

You'll have to consult the spec sheet for that. I only cared about one parameter.

MarNav1 said:

You'll have to consult the spec sheet for that.

Click to expand...

I did so, but it says nothing about adjusting the frequency and the pulse length. There is one application example ("Variable flasher") which allows to adjust the flash rate (0 - 20Hz), and probably the pulse length by changing one of the many resistors required on the diagram. But this circuit requires even more component than the standard 555 setup, so I see no advantage in using the 3909 to achieve this.

Cemoi said:

I see no advantage in using the 3909 to achieve this.

Click to expand...

It runs off a single 1.5V cell, thats the advantage.

The main point of my post was ease of use with minimum parts. I didn't claim it was the only way, just one way. Cemoi, if you want to adjust different things for your flasher great. This may not be the circuit. But for simplicity sake and to try and help the OP, I offered a good one. I know it works great for it's intended purpose and is cheap and very easy to operate, and the circuit will flash an LED for a VERY long time on a cell. There probably are better circuits out there, I am not familiar with all of them.

MarNav1 said:

Cemoi, if you want to adjust different things for your flasher great. This may not be the circuit. But for simplicity sake and to try and help the OP, I offered a good one.

Click to expand...

Sorry MarNav if I may have sounded a bit critical. I was only trying to get additional information not found in the datasheet. And I will try to find a 3909 locally, at least to play with it.

No harm, no foul. They are fun to play with, if you figure out how it's done lemme know. I like LED flasher circuits. You won't find them (3909) locally though as they were discontinued probly at least 10 years ago. I have found a few sources for them. Have fun!

I used this style of circuit for a LED tail light with great effect. The flash speeds can be altered by changing the size of the capacitors or the 100kOhm bleed resistors.

By changing only one side of the circuit you can make one LED stay on longer (or off) than the othe. Also by removing one LED and replacing it with resistor the dissipates the equivalent you can have a single flashing light. To make this more energy efficient however it might be a good idea to use a much smaller cap and a higher value bleed resistor when doing this.

Multiple LED's of any sized can be used in series, just keep in mid the more you use, the bigger the cap will need to be to keep the same flash time. Even power LED's (XP-G, XR-E etc) could be used if the driver running them has a enable pin on the chip such as the AX2002.I have never tried this myself but.

Lastly, when dialling in the right flash speed it might be a good idea to replace one of the bleed resistors with a POT, turning it to get the desired speed and the measuring the resistance.

This is perhaps one of the more fiddly ways of making a light but it can be done without any IC's and with parts you may already have laying around the house. :candle:

I am also interested in this. I would like to make one that blinks alternately just like this one^

I plan to power some XR series LEDs. Blue and Red. Can you see what I'm going for? Also, I wonder if there is a way to make each one blink twice before alternating.

Can anyone help out here? I have never built a circuit with a capacitor before, so it's a little confusing to me. I have a good understanding of linear circuits, and a basic understanding of transistors and capacitors.