I broke down and bought a MEGA, it should be here any day now.
I'm working on a project to produce a Emergency Strobe bar for my Personal Fire Response vehicle.
Being some what crafty, I figured the use of open source technology would be a much more rewarding experience than spending $2000 on a pre-fab light bar and supporting companies that could care less about saving lives and more about profits.
So far I have ordered 250 LEDs, 50 1ohms Resistors, and the Mega.
I have been working on various ways to drive the leds, using some help from the wonderful world of google, I have found a simple solution is to run then linked to each other with a resistor at the end of each chain.
to better explain what I'm doing, I have created the worst graphic layout you will ever see in your life, but i hope it explains exactly what I hope to accomplish, not only for my own personal experience, but to save lives responding to fires more safely.
Please understand I am not wanting to address the external power supply at this point, I think it is more important to focus on correctly wiring everything first to avoid burning out the mega.
To be honest, the more I dig into this, the more I start to wonder just how much of an idiot I am for attempting such a huge project, perhaps not so huge for you guys/gals, but for me this is all new and exciting.
I want to thank EVERYONE who is taking the time to not only read this, but also offer any help.
SO, Thank you.
**Now here is the very large image that may or may not display correctly, if not, you can view it here.**http://www.knoxvilletechnology.com/strobe-layout-help.jpg
So far I have ordered 250 LEDs, 50 1ohms Resistors, and the Mega.
You need to tell us something about the LEDs. What voltage they operate at, the forward voltage drop, etc. The 1 ohm resistor may not be near large enough to limit the current to safe levels.
Are you expecting to be able to turn 25 LEDs on and off at once? Or, are you expecting to do more than of/off for the sets?
Please understand I am not wanting to address the external power supply at this point, I think it is more important to focus on correctly wiring everything first to avoid burning out the mega.
I think you have this backward. First, you need to figure out how to power and wire the LEDs, then figure out how the Mega can turn them on and off. That requires knowing how much voltage and current are involved, and whether simple on/off is enough, or if fading is required, too.
I can only go by the information provided.
I am only asking for your help to make this work, not TELLING you what I am going to do regardless of what you say.
It was my impression the community was supportive of new ideas, this is why i chose this direction, but if it is an issue i can simplu drop the whole thing now.
First of all, the whole reason 16 volt came around is the calculator would not make a 5x5 array without anything less.
So, maybe a 5 x 5 array is not possible. You could try a 4 x 6 array.
That link is next to useless. There are no technical details about the LEDs.
Voltage drop, current, etc. are important attributes to size the resistors and power supply.
It was my impression the community was supportive of new ideas, this is why i chose this direction, but if it is an issue i can simplu drop the whole thing now.
It's not that we are up-supportive, but you really can't just buy random stuff and expect to connect it together and have it magically work.
You need to start with what you have (12 Volts from the battery) and what you want to do, then choose components (LEDs with known voltage and current requirements) that fit within the constraints you have.
It's much safer to run a single resistor on each LED. Much more time consuming to make, but safer. Are you going to design a circuit board for this thing in something like Fritzing, or were you planning to build it on a perfboard? The thing about LED's and resistors is they don't lose brightness until you give them WAY too much resistance. So it's usually safest to just give them too much resistor rather than too little, especially if you want a long life out of them.
Another thing is that in a harsh automobile environment, they're going to put a lot of stress on their solder joints, simply because of the vibration and momentum, you might consider pouring some clear potting compound over them, after you've got it all confirmed working.
Personally, I'd use RGB LED's, especially with a Mega controlling them. Then you'd be able to do things like switch from blinking blue/red to blinking orange for caution, or blinking orange arrows, etc.
sorry I did not see your response, i'm only using white led's to cover with red lense, and to keep it simple, we are only allowed red unlike other states where blue is allowed.
i was thinking about trying my hand at etching copper, but but if i have to use a resistor for each led, omg the drilling.
my thought for allowing for filters would be for after I pass my EMT exam where green will be allowed, I have a bunch of code3 lightbar lenses, so its not a big deal to throw one in front of the leds
so am i correct on the 120 ohms resistor after every 3 led's?
i guess i need to order 80 of them.
damn thats a lot of soldering.
