How can I create a battery powered LED that flashes 8 times per minute?

[brian04]

Hey team i need some simple electrical engineering advice. I am a surgery resident and I need battery powered LED that flashes at 8 times a minute. Research funding is about as easy to find as health insurance so I am trying it on my own. I thought about just taking apart a flashing light that I use when i ride my bike to work but I am not sure conceptually the mechanism for changing the timing of the flash.
Project requirements:
- small (about the size of the old school plastic rings out of the 25 cent machines)
- battery powered
- 8 flashes per minute
- duration of flashing 2 hours max

I am thinking that I'll just build the circuit on a hinge so that when the attachment site is expanded to a hemisphere it completes the circuit and the light begins to flash. Any thoughts would be great. Especially on the timing mechanism.

 

[mheslep]

Hey team i need some simple electrical engineering advice. I am a surgery resident and I need battery powered LED that flashes at 8 times a minute. Research funding is about as easy to find as health insurance so I am trying it on my own. I thought about just taking apart a flashing light that I use when i ride my bike to work but I am not sure conceptually the mechanism for changing the timing of the flash.

Good idea if you want something quick and ready to go. I haven't inspected a bike flasher either, but it may very well be a simple resistor - capacitor pair that is used to establish the existing timing. If so, and you can find and identify the resistor, then removing and replacing the existing resistor w/ something larger will likely work. That is, if the current flash rate is T=0.5s and you want T=~7s, then replace with an R ~14X larger from your local electronic supply. Soldering etc required for a permanent fix.

 

[p1ayaone1]

555 timer! It is quite flexible in terms of specifying Ton and Toff, and pretty simple to implement, but the results won't be perfect. (i.e. you shouldn't use it to time IV drips or life-support equipment!)

http://www.kpsec.freeuk.com/555timer.htm#astable