R2 LED question. Front Logic displays & pic LED flasher

Sulla · Dec 29, 2008

Please excuse the naiveté, but I am none-too-skilled in electronics. I can wire up a single or maybe two LEDs in serial with a battery and switch; however, I am confident I can do the logic displays.

I am using this pic LED flasher kit for my front and rear logic displays.
http://www.electronickits.com/kit/co...igh/ck1007.htm

I plan on using 3mm blue and white LEDs for the front logics.

2 questions:

1. Should I go with frosted LEDs like in Mike's tutorial or should I use ultrabrights, or something else entirely?
2. Will any 3mm LEDs work? Do I have to worry about resistor values in the pic kit?

Thanks again.

Jack Knight1979 · Dec 29, 2008

You seem to be fine. No need for resistors. with the pic kit.
Do NOT use Ultrabrights. you'll regret the power consumtion and the LED's are too bright.

exoray · Dec 29, 2008

Jack Knight1979 said:
You seem to be fine. No need for resistors. with the pic kit.

There is still a need for the resistors they are just balanced for that kit and already installed based on the way they wired the LEDs...

Now sticking to regular standard red/green/yellow LEDs and wiring them the same as the kit, should allow the same resistor value to be used... But if you start changing up the series/parallel bundles of LEDs or using say, blue or white LEDs then there is a good chance you will need to change up the resistor values used on the board...

Sulla · Dec 30, 2008

Thanks Jack Knight1979, and Exoray.

Here's the link to the tutorial I am getting this al from:
http://www.mbiasi.com/R2-D2/frontlogic-small.html

Here's the technical specs of the pic flasher:
http://www.electronickits.com/kit/complete/ligh/ck1007.pdf

Looks like they use a current limiting resistor of 470R for 16 super bright leds (8 red/8 green).
I will be using 90 total LEDS in the front logic display from one pic flasher. About half white, half blue.

That said, if I use say these:
http://cgi.ebay.com/100p-3mm-SUPER-BRIGHT-BLUE-LED-13-000mcd-FREE-RESISTOR_W0QQitemZ370137647910QQcmdZViewItemQQptZBI_Electronic_Components?hash=item370137647910&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A0%7C293%3A1%7C294%3A50
http://cgi.ebay.com/100p-3mm-SUPER-...5|66:2|65:12|39:1|240:1318|301:0|293:1|294:50And these:
http://cgi.ebay.com/Lot-of-100-X-3mm-White-LED-13000mcd-Free-Resistors_W0QQitemZ220336642881QQcmdZViewItemQQptZBI_Electronic_Components?hash=item220336642881&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50
Would they work with this pic flasher kit and would I have to switch out the kit's resistors for the resistors that come with the LEDs? How do I figure the math? I am bound and determined to learn this.

Sulla · Dec 30, 2008

I just pulled those off a quick ebay search for '3mm Blue LED' They are 5.0 volt... Should I go with a 1.5v LED instead? All I can seem to find on ebay are 5mm 1.5v Blue LEDs. I really wanted 3mm.

I guess I could troll Fry's or some place and pay more...

Sulla · Dec 30, 2008

How about these specs? They are a lower voltage.

Emitted Colour : Blue
Size: 3mm
Lens Color : Water Clear
Forward Voltage (V) : 3.0~3.6
Forward Current (mA):20
View Angle: About 25 degree.
Static Sense:Yes
Luminous Intensity: 15000mcd
Life Rating : 100,000 Hours
Free Resistors:
Supplied with free resistors for DC 12V

Emitted Colour : White
Size: 3mm
Lens Color : Water Clear
Forward Voltage (V) : 3.0~3.6
Forward Current (mA):20
View Angle: About 25 degree.
Static Sense:Yes
Luminous Intensity: 15000mcd
Life Rating : 100,000 Hours
Free Resistors:
Supplied with free resistors for DC 12V

Sulla · Dec 31, 2008

OK, so I figure if I use these LEDs and folow Mike's tutorial (http://www.mbiasi.com/R2-D2/frontlogic-small.html) i.e. 8 strands of 13 or 14 LEDs in series (using 3V per led with 20mA forward current), and use the maximum power that they mention in the datasheet for the pic flasher (45V), then I would need 150 ohm resistors for the 14 led strands and 300 ohm resistors for the 13 led strands.

But won’t I also need something to produce the 45V DC current that I am basing this off of? So I will either need a battery pack that can produce this or a rectifier that can. So like 5ea. 9volts or something?

Can I use less voltage (less batteries) and just change the value of the resistors?

ShackMan · Dec 31, 2008

Never heard of a 5V LED (unless you mean an LED with a resistor already atached to drop the extra voltage. The ones you gave specs for are typical (roughly 3V forward drop).

As for voltage, keep this in mind: The lower the voltage you use to drive them, the higher the current you'll need.

Let's say you have 4 LEDs rated at 3V each. You could use a 9V battery to drive them, but would need 2 series strings, each running at about 20mA (for a total of 40mA from the battery). If you ran those same LEDs from a 12V source, you could put them in one series string drawing only 20mA. Of course, I'd still put a small current limiting resistor in the 12V line (don't assume the LEDs will be OK because they total 12V).

Hope that made sense,

ATM
ShackMan

exoray · Dec 31, 2008

You have 8 channels on that kit, and you want to run 90 leds, that means each channel has to source 11-12 leds

So if you wire it as shown in on the site, you will need a 36+ volt supply to power it... Probably not the best option...

Better option..

You need to get more creative with the led series/parallel arrays to make it work with a lower voltage... The arrangement and wiring of the leds will be very different then what is pictured...

Tell me your intended power supply and I can continue from there...

BTW a 9 volt battery is not a good choice here with 90 leds you will be drawing a minimum of 600mA that is more then the 9 volt is intended for, your run time will be measured in minutes and the battery will get pretty damn warm...

Got Maul · Dec 31, 2008

exoray said:
You have 8 channels on that kit, and you want to run 90 leds, that means each channel has to source 11-12 leds

So if you wire it as shown in on the site, you will need a 36+ volt supply to power it... Probably not the best option...

Better option..

You need to get more creative with the led series/parallel arrays to make it work with a lower voltage... The arrangement and wiring of the leds will be very different then what is pictured...

Tell me your intended power supply and I can continue from there...

BTW a 9 volt battery is not a good choice here with 90 leds you will be drawing a minimum of 600mA that is more then the 9 volt is intended for, your run time will be measured in minutes and the battery will get pretty damn warm...

To your point :

"[SIZE=-1]I've ordered a 12 volt DC to 36VDC converter from MPJA for when I switch everything over to being run off a battery. I plan on using a small voltage regulating circuit to drop that down to the 30 volts I've been running things at"

Taken from the site.
[/SIZE]

exoray · Dec 31, 2008

Got Maul said:
To your point :

"[SIZE=-1]I've ordered a 12 volt DC to 36VDC converter from MPJA for when I switch everything over to being run off a battery. I plan on using a small voltage regulating circuit to drop that down to the 30 volts I've been running things at"

Taken from the site.
[/SIZE]

Yeah but there are better options, every time you convert voltage up or down you lose something it's inefficient...

In the above example there is no need to step it up to 36 volts just use the existing 12 volt battery, it can be run off a decent 12 volt gel cell battery, or even C or D cells... It's just a matter of wiring the LEDs differently...

Here is the kit running off 12 volts and 96 leds...

If you require 90 LEDs then the last LED bundle should look like this...

And there it is running 90 (3.0 volt @ 20 mA) LEDs off a 12 volts system no need to step it up to 36 volts...

Also you shouldn't mix and match LED colors in the stands, the slight differences in their specs could cause an imbalance and cause failure... You can mix and match them in the bundle but each group of 4 LEDs should be alike...

Got Maul · Dec 31, 2008

awesome ! That's the plan I am going with then !

ColeHorton · Dec 31, 2008

hmmm...I'm feeling like a slacker. I still don't have lights in my dome. :unsure

Its hard to tell, but that front logic is just an image I photoshopped and printed on my home printer. Backed it up with some styrene so that the kids don't push it in (they try their hardest). I could finish my lights, or just tell myself its one less thing for the public to destroy. :lol

Sulla · Jan 1, 2009

Thanks!, very cool. So a 1ohm 1/4 watt resistor would do the trick for the bundles, and perhaps a 1/4 watt 330ohm resistor for the short bundle?

exoray said:
Yeah but there are better options, every time you convert voltage up or down you lose something it's inefficient...

In the above example there is no need to step it up to 36 volts just use the existing 12 volt battery, it can be run off a decent 12 volt gel cell battery, or even C or D cells... It's just a matter of wiring the LEDs differently...

Here is the kit running off 12 volts and 96 leds...

If you require 90 LEDs then the last LED bundle should look like this...

And there it is running 90 (3.0 volt @ 20 mA) LEDs off a 12 volts system no need to step it up to 36 volts...

Also you shouldn't mix and match LED colors in the stands, the slight differences in their specs could cause an imbalance and cause failure... You can mix and match them in the bundle but each group of 4 LEDs should be alike...

exoray · Jan 1, 2009

Sulla said:
Thanks!, very cool. So a 1ohm 1/4 watt resistor would do the trick for the bundles, and perhaps a 1/4 watt 330ohm resistor for the short bundle?

Yeah 1/4 watt or 1/2 watt sometimes the 1/2 watts are easier to source... You can also use 1/8 watt for the 1 ohm ones, but not for the 330 ohm one it needs to be 1/4 or bigger...

Going bigger won't hurt, so when it doubt get the bigger ones...

Got Maul · Jan 1, 2009

So just to be sure :

I bought :

1. 100 blue leds, 100 white leds (specs above)
2. The kit

I still have to buy 1 ohm resistors for each strand still right ? 36 1 ohm resistors all together ?

exoray · Jan 1, 2009

Got Maul said:
So just to be sure :

I bought :

1. 100 blue leds, 100 white leds (specs above)
2. The kit

I still have to buy 1 ohm resistors for each strand still right ? 36 1 ohm resistors all together ?

24 @ 1 ohm by my math

or 22 @ 1 ohm and 1 @ 330 ohm...

If you purchase then anywhere besides Radio Shack they will almost certainly sell you them by the 100 count for about $1... Radio Shack is 5 for $1

Sulla · Jan 1, 2009

Got Maul said:
So just to be sure :

I bought :

1. 100 blue leds, 100 white leds (specs above)
2. The kit

I still have to buy 1 ohm resistors for each strand still right ? 36 1 ohm resistors all together ?

I bought the LEDs in lots of 100 each color because that's the way they were sold. Can't hurt to have a few laying around for other projects or repairs. The front logic displays use 90 total LED's, about half of each color.

Resistors are inexpensive depending on where you get them.

Got Maul · Jan 1, 2009

cool ! I will order these next.

Sulla, do you have a source for the actual perforated metal sheet ? I have the housings, but just not the punched walls with the 3mm holes.

Sulla · Jan 1, 2009

Got Maul said:
cool ! I will order these next.

Sulla, do you have a source for the actual perforated metal sheet ? I have the housings, but just not the punched walls with the 3mm holes.

No. I was just going to try my hand at making my own from black acrylic. If that fails, I'll start casting around for some.

R2 LED question. Front Logic displays & pic LED flasher

Sr Member

Well-Known Member

Master Member

Sr Member

Sr Member

Sr Member

Sr Member

Sr Member

Master Member

Official Licensee

Master Member

Official Licensee

Well-Known Member

Sr Member

Master Member

Official Licensee

Master Member

Sr Member

Official Licensee

Sr Member

Similar threads