Firefighter needs help with LED strobes

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deeredude88

New Member
I am a 17 year old high school student that is also a volunteer firefighter. I am trying to build a lightbar for the rear window of my truck to warn traffic. I need to use blue and white LED's and I want them to strobe, or have some sort of pattern. I am trying to use the most amount of LED's possible (around 60). My plan is to make "blocks" of 6 leds, and then stagger the colors in a row on the bar. (ex. blue block, white block, blue block and so on...).

I am extremely good with vehicle wiring (12v) but I am only beginning with Picaxe type wiring, so try to keep it simple for me.

I also have a shop teacher that is extremely smart with anything electrical, so if you use a term that I don't understand, I will ask him.
Thank you so much,
Scott Erickson
Altona Fire and Rescue
 
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Marcwolf

Senior Member
Firetruck strobes

Hi there.
I have done a similar things to our trucks - although not quite as elaborate.

I used Mosfets to power the lights from the PicAxe. It also meant that I could do things like hook the headlights into the circuit for the flash.

Take care
Dave
 
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Andrew Cowan

Senior Member
Have you got your eye on any particular LEDs? I don't know how bright you want them, or how dark it will be when you want them to be seen (and by who), but this could be expensive.

Blue and white are generally the most pricey colours.

Andrew
 
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alband

Senior Member
Just to start you off, do a search of the 7806 voltage regulator. That will get 12V down the 5v a PICAXE needs.
I assume size isn't much of an issue so I'd recomend using so high power relays. A PICAXE itself can give large output voltages so you can wire up your LED's with relays so your PICAXE controls them but the fire engine (I don't know much on the subject but I pretty sure you'll some kind of power on that thing) will provide the power.
This is a useful sheet: http://www.economatics-education.co.uk/images/additional/Download Files/picl manual.pdf
It is actual a manual from a piece of software you wont need (costs more money than the free one from Rev-ed and you cant do as much with it) but it is very useful as an intro to PICAXE's.
Page 48 covers 7805's
and near the bottom are wiring diagrams for most things.
Again, what LED's they'll need to be pretty big to be of an notice compared to the standard ones.
Can I ask why you want these light?
Good luck! :)
 
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LizzieB

Senior Member
I think you mean 7805 for 5 volts.

His post says he's a volunteer fire fighter, in some states they are allowed to use blue lights.
 
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deeredude88

New Member
clearing things up

Thank you all so much for your help!!!

and just to clear some things up, I am an EMT in Illinois, so we can have blue lights

these lights are going in my personal response vehicle, (a 1993 ford f150)

and, i am thinking about downsizing a little, your thoughts?

also, does anyone know how to make them strobe?
thanks again so much!!!
 
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BITMOVER

Member
HI,

Since you appear to be new to programing, I sugggest you get a starter kit for the PicAxe and get some hands-on experience, or, have someone do the progrqmming for you. It would be possible to have many different flashing patterns, and speeds, all user selected, and done with simple programming .

Here's a typical snip of code that could be used...

Do
high 0
pause 200
low 0
pause 200

high 1
pause 200
low 1
Pause 200

high 2
pause 200
low 2
pause 200

loop

This would cause each of three lights, to flash in sequence for .2sec each for as long as the circuiy is powered. Ther are many ways to write the code but this is just to illustrate the point.

The PicAxe cannot operate any large load so it needs additional interfacing to make it work in your application. I can offer my assistance if you need it! Feel free to post questions or email me through this forum.

Len
 
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BrendanP

Senior Member
Contact Mouser in Texas and ask them for their hardcopy catalogue, you will be able to source most if not all the parts for this pro*ect from them. (one of the keys on my notebook has *ust died hence the missing letter).

By using the pwm command you can make the LEDs pulse at varying levels of brightness.
 
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alband

Senior Member
How do you mean strobe? Do you want something like on an emergency vehicle with the light spinning round or do you just want them to flash.
What type of LED's are you going to use?
 
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Michael 2727

Senior Member
Just remember that 60 LEDs running at 20mA each will suck 1.2Amps.
I suspect you will want to use high brightness LEDs if you want something
that is daylight visible, in that case you may need a supply that is capable
of driving 2 x to 3 x that rating. Most TO-220 package MOSFETs will handle
4 Amps upwards.
Something like a Logic Level (switching) MOSFET may be the easiest option.
A simple sequence of Hi/Lo from a picaxe output/s will get you going ;)
And use a FUSE.
Good luck.

EDIT:
Usually posting anything "Automotive" will get you a barrage of WARNINGS about
the use of Microcontrollers/PICAXEs in a potentially hostile electronic environment.

A Recent Thread- (there are many others)-
http://www.picaxeforum.co.uk/showthread.php?t=10661

Some App Notes from Maxim on the subject-
http://www.maxim-ic.com/appnotes.cfm/an_pk/4240
 
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papaof2

Senior Member
Look at this page for some relatively inexpensive high intensity LEDs:
http://www.ledshoppe.com/led10mm.htm (Thier typical shipping to the US is about 2 weeks.)

Note that the blue LEDs are less than than 1/2 the intensity of the white LEDs (8000mcd versus 18000mcd). This means that you would need more than twice as many blue LEDs in a strobe unit to match the brightness of the white LEDs.

If you are mounting the LED strips at the inside top of the front window (a common mounting) then remember that only the people immediately ahead of you can see the bright part os the lights - LEDs have a narrow code of light output. For maximum visibility, nothing beats roof-mounted halogen lights. If you want to be noticed during the day, a halogen powered light is probably what you need. The police light bars that use halogen bulbs do not flash/strobe the bulbs - the bulbs don't respond fast enough. Instead they use a combination of fixed and rotating mirrors to generate a constant low level of light plus a bright "flash" when a mirror is pointed directly at you.

If this is a learning project, by all means go ahead - you'll find lots of other applications for the PICAXE line.

If you want a light immediately, check Ebay - this offer is for a set of two light assemblies with 22 blue LEDs each and a controller for $13US plus $13US shipping - there's even a video of how it looks:
http://cgi.ebay.com/ebaymotors/2-Blue-LED-Strobe-Flashing-Light-Panel-Grill-Emergency_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1205Q7c66Q3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318QQ_trksidZp3286Q2ec0Q2em14QQhashZitem160290735187QQitemZ160290735187
Check this vendor's other listings - they also offer the lights in white.

If you have deep pockets, the commercial public safety LED bars are $156US from this vendor: http://www.oviedosafetylights.com/shopping.idc?ProductID=51&ProductCategory=

Good luck - and we appreciate the volunteers who provide emergency services to so many communities!

John
 
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nyyankeehater

New Member
this is exactly what I am currently working on . Thanks to all of the helpful ppl here I have finally created 8 flash patterns. Check out this thread :http://www.picaxeforum.co.uk/showthread.php?t=10792 they helped me out a lot. Here is one of the flash patterns i came up with: (nothing special just a wig wag pattern with double strobe effect)

Code: 
let dirs = %00010111
main:
let pins = %00010100
let pins = %00000000
let pins = %00010100
let pins = %00000011
let pins = %00000000
let pins = %00000011
goto main
________
ONE TREE HILL ADVICE
 
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