Best way to wire a bushel of LEDs? - Page 2 - Electronic Circuits Projects Diagrams Free

justDIY · 13th January 2008, 08:44 PM

Peter, if you can wire your leds as a big matrix then you can spell out the letters you need in the matrix, as well as change them down the road. you can then use the maxim matrix driver chip.

but if you're wanting to wire up discrete letter modules, the matrix driver chip will get expensive, you'll need one for each letter, unless you want wires running between the two.

Hero999 · 13th January 2008, 09:48 PM

Quote:

Originally Posted by atferrari

The 7219 is a good chip!

I've never heard of it and I've done a quick Google and couldn't fine it.

Could you please post a datasheet or a link to a place where you can buy them?

futz · 14th January 2008, 12:16 AM

Quote:

Originally Posted by Hero999

I've never heard of it and I've done a quick Google and couldn't fine it.

Could you please post a datasheet or a link to a place where you can buy them?

Maxim-IC makes them (and sells them).
Digikey sells them. For sure lots of other suppliers sell them too.

Hero999 · 14th January 2008, 09:45 PM

I see, you mean the MAX7219, I wish people would privide propper part numbers, 7219 doesn't mean anything to me.

weegee · 14th January 2008, 09:55 PM

Quote:

Originally Posted by weegee

...and my favorite weapon of choice just now is a couple of Max7219 chips, which can be found really cheap, the chip...

i included the full chip name in my earlier post.

as a side note, (and not one i'd reccomend), but if you use these chips and leave the data in, and load lines, and clock floating, they tend to drift into test mode, which is ALL leds on full brightness.

Peter_wadley · 16th January 2008, 12:52 AM

Ok,

Ive wired the letters up.. included are some pictures of the project (i'm modifying a terminator poster)

The brightness of each letter is very close .. i chose to vary the resistance for each batch of LEDs .. keeping current of each around 22ma...

Now I would like to implement the PIC to control the letters..

I am having trouble wiring this..

I was going to have the PIC to control NPN transistors which would supply 24 volts to the each letter..

The LEDs are wired in series.. so to turn on a letter I must supply positive voltage, which goes through the resistor, then through the batch of LEDs... which then goes to a common GROUND connection which is located on the back of the poster.. (each letter shares a common ground)

The problem is.. how do i wire the transistor to supply 24 volts to the one red wire coming out of each letter?

I understand the load for transistors should be in series .. from the +V to the collector pin..

I am very confused about what to do.

Thanks for any help

ronjodu · 16th January 2008, 02:44 AM

Very cool project. You could add some really cool effects with a MAX chip like weegee suggested. My favorite is the MAX6957 (SPI version).
I have 3 cascaded together driving 4-7segments with DP and 2-10 segment bargraphs. Only 3 pins from the pic micro are used. Looking forward to updates on your progress...

Peter_wadley · 17th January 2008, 01:10 AM

Hey,

Not trying to nag..

but im still trying to figure out how I can wire this ...

I would use the PIC to directly source the LEDs.. but 24v through a PIC = smokey!

Can someone just let me know if its possible to use a transistor without wiring in series.

The project is kind of at a stand still now.. taking up my workbench..

thanks for any help!

weegee · 17th January 2008, 01:35 AM

sorry, but im now lost. if your just lighting the leds, and not doing anything fancy - why do you need the pic? it's just consuming board space and using un-neccisary parts.

anyway - suppy + to the annode of your led string via suitable resistor, and connect the common cathode to the collector of your transistor. connect the emmitter to gnd, and the base to your pic pin(via current limiting resistor). i think thats right

justDIY · 17th January 2008, 01:38 AM

you want an NPN transistor if you're switching the low side (-) of your led array, or a PNP transistor if you'd rather switch the high side (+)

it doesn't matter how you have the leds wired, as long as you can break the circuit somewhere to stick in your transistor.

http://www.kpsec.freeuk.com/trancirc.htm

weegee · 17th January 2008, 01:57 AM

oops, forgot that - my description was for an NPN transistor - sorry.

Peter_wadley · 17th January 2008, 04:20 AM

Ok

Yeah i thought i would need to go in series like your saying.

Its just that I have wired all the cathode commonly on one wires ...

I guess for each letter I will need a positive wire and a ground wire.. then put it in series with the transistor..

thanks

blueroomelectronics · 17th January 2008, 07:18 AM

Something like this

justDIY · 17th January 2008, 01:32 PM

Quote:

Originally Posted by Peter_wadley

Its just that I have wired all the cathode commonly on one wires ...

if all your leds are wired in parallel, I hope you're not still using the 24v supply... you'll be wasting almost all of power in the resistors ... you'll have a heater that also happens to be a light up sign.

Peter_wadley · 17th January 2008, 11:38 PM

I have it wired like this.

Would this be considered parallel?

Each letter has its own, different set of resistors.

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13th January 2008, 08:44 PM	(permalink)
justDIY	Peter, if you can wire your leds as a big matrix then you can spell out the letters you need in the matrix, as well as change them down the road. you can then use the maxim matrix driver chip. but if you're wanting to wire up discrete letter modules, the matrix driver chip will get expensive, you'll need one for each letter, unless you want wires running between the two. __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

14th January 2008, 09:45 PM	(permalink)
Hero999	I see, you mean the MAX7219, I wish people would privide propper part numbers, 7219 doesn't mean anything to me. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez

16th January 2008, 02:44 AM	(permalink)
ronjodu	Very cool. Very cool project. You could add some really cool effects with a MAX chip like weegee suggested. My favorite is the MAX6957 (SPI version). I have 3 cascaded together driving 4-7segments with DP and 2-10 segment bargraphs. Only 3 pins from the pic micro are used. Looking forward to updates on your progress...

17th January 2008, 01:10 AM	(permalink)
Peter_wadley	Hey, Not trying to nag.. but im still trying to figure out how I can wire this ... I would use the PIC to directly source the LEDs.. but 24v through a PIC = smokey! Can someone just let me know if its possible to use a transistor without wiring in series. The project is kind of at a stand still now.. taking up my workbench.. thanks for any help! __________________ "Stick around" - Arnold Schwarzenegger in The Predator after impaling a soldier to a wood post 9vDC Guitar Pedal PSU PIC16F84a Game Module

17th January 2008, 01:35 AM	(permalink)
weegee	sorry, but im now lost. if your just lighting the leds, and not doing anything fancy - why do you need the pic? it's just consuming board space and using un-neccisary parts. anyway - suppy + to the annode of your led string via suitable resistor, and connect the common cathode to the collector of your transistor. connect the emmitter to gnd, and the base to your pic pin(via current limiting resistor). i think thats right

17th January 2008, 01:38 AM	(permalink)
justDIY	you want an NPN transistor if you're switching the low side (-) of your led array, or a PNP transistor if you'd rather switch the high side (+) it doesn't matter how you have the leds wired, as long as you can break the circuit somewhere to stick in your transistor. http://www.kpsec.freeuk.com/trancirc.htm __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

17th January 2008, 01:57 AM	(permalink)
weegee	oops, forgot that - my description was for an NPN transistor - sorry.

17th January 2008, 04:20 AM	(permalink)
Peter_wadley	Ok Yeah i thought i would need to go in series like your saying. Its just that I have wired all the cathode commonly on one wires ... I guess for each letter I will need a positive wire and a ground wire.. then put it in series with the transistor.. thanks __________________ "Stick around" - Arnold Schwarzenegger in The Predator after impaling a soldier to a wood post 9vDC Guitar Pedal PSU PIC16F84a Game Module

17th January 2008, 07:18 AM	(permalink)
blueroomelectronics	Something like this __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com