Powering up LEDS

If I wanted to power up maybe 50 to 100 LED. How much power do I need and how would they be wired up. One switch would turn them all on. Also would like to add a dimmer.

Thanks

Anything from 50 to 100mA up to 17.5 to 35A, depending on LED type and brightness. Assume 2V per LED, that's from 100mW to 70W, roughly. Probably slightly higher.

how about resistors or anything else… Im a noob to this kind of stuff. I can read electrical diagrams no problem since im in hvac controls field.

Would someone be able to write up a quick small diagram. Also how many leds do you think will need to light up a small 8 feet by 9 room.

Kind of depends on the color type of the LEDs. Standard red LEDs have a nominal forward voltage drop of 1.5vdc and are normally run at 20ma of current. So 50 or 100 would require 1.5 or 3 watts of power respectively, not accounting for needed current limiting resistors dissipation.

How best to wire them up depends on what external power source you have available, it's voltage and max current ratings. You will also have to make sure you have proper LED current limiting by use of resistor(s). The switching part would be performed by an external transistor and dimming them would only involve using a Arduino PWM output pin and the correct sketch programming.

Lefty

What would be the best way to supply the 3 watts.

Would love to eventually maybe add a small solar panel that can product that power and a battery to charge.

But for now I will supply the power I only have power source right now 24Volts, 12dc 5dc and 3dc

Well using the highest avalible voltage would result in the fewest needed current limiting resistors. So if your +24vdc power supply is rated to at least 200ma max, you could wire strings of 10 series connected LEDs with one 450 ohm resistors. Then make either 5 or 10 such strings for your 50 or 100 total LEDS. One end of all the strings (the anode ends) would wire to the +24vdc supply. All the cathode ends would wire together and then wire to the collector end on a NPN switching transistor rated for one amp or better. The emitter of the transistor would wire to the 24vdc ground. The base terminal of the transistor would wire to a series 1k resistor and the other end of the resistor would wire to one of the Arduinos PWM output pins. Last you would add a ground wire from an Arduino ground pin to the emitter of the transistor.

Lefty

Could someone sketch up a diagram for me. Just for fun Il pay $5 paypal lol. Its just much easier if I have a diagram to use.

Also would it be possible to take a usb cam I have for my pc and make it wireless?

Right now I cut the usb cable in half and took out the cam chip and mounted it in living room and have cable going to my office. Whats the easiest way to make it wireless and small range. Or is it cheaper just to buy a wireless cam.

Thanks for all your help. Just started getting into electronics so Im playing with a lot of stuff lol.

Took a $5 remote control car and used the two motors to open up my shades was going to try to set it up so it can someone detect and what angle most sun is coming to open shades auto.

I learned a lot from this site already great forum.

Also I have a 24volt transformer rated at KVA: 100 . Is that enough I also have multiple transformers.

Also I have a 24volt transformer rated at KVA: 100 . Is that enough I also have multiple transformers.

100 KVA is 100 watts so it is certainly large enough for 3 watts worth of LEDs :wink:

More importantanly that gets you 24vac not dc. You need a rectificer circuit and power filter caps at a minimum and you then end up with around 33 volts on unregulated DC voltage. This would require increasing the resistors sizes to around 1k ohms.

Lefty

Would you be able to write me a quick schematic on how to wire it and also a material list. If there is anything I can do in return let me know

Sorry, I have no drawing software available to me, nor the desire to learn to use one.

If you can draw something up, I would be happy to comment on it, or possibly someone here can create such a drawing for you, or perhaps link to an existing schematic drawing?

Lefty

Honestly you’re best to have a stab at the schematic yourself and others here will comment. If you blindly follow someone elses diagram, you don’t really learn. I’m thinking about something similar for a bathroom. I’m considering using shiftbrites. Check them out - they might add a lot to you your costs though.

lol i suck at diagrams. Do I need a resistor for every led light? Also with a 100Kva 24volt transformer how many leds can i add on it.

Im thinking to do something with my hallway. Its about 4 feet by 20.. Make like a landing strip lol..

Do I need a resistor for every led light?

That depends on how you wire them up. In my description above you need one resistor for every series string of 10 LEDs,

so +24vdc- R- L- L -L -L -L -L -L -L- L -L-transistor collector.

All the Ls (LEDs) face the same way with the anodes pointing towards the R (resistor) Make 5 or 10 of those LED strings. All 5 or 10 strings wire to +24vdc and to the one transistor collector.

That make sense?

Lefty

Yea now it makes sense. Also where do I get a transistor collector?

"All the Ls (LEDs) face the same way with the anodes pointing towards the R (resistor)"

Also what do you mean by that?

Thanks for your help.

My Arduino just came in so also going to start playing with it.

Is there a way to calculate how many leds you would need to light up a room.? I was thinking my bathroom and kitchen both small. Maybe 5ft by 7 and a 8x9 room.

My goal was at end to someone have it powered by the sun. Go Green ;D and save money.

Yea now it makes sense. Also where do I get a transistor collector?

"All the Ls (LEDs) face the same way with the anodes pointing towards the R (resistor)"

Also what do you mean by that?

Thanks for your help.

My Arduino just came in so also going to start playing with it.

Is there a way to calculate how many leds you would need to light up a room.? I was thinking my bathroom and kitchen both small. Maybe 5ft by 7 and a 8x9 room.

My goal was at end to someone have it powered by the sun. Go Green and save money.

LEDs have two wires coming off them, one is called the anode and the other the cathode. You will have to determine which is the anode and which is the cathode. Normally the anode wire is a little longer then the cathode wire, but I like to measure with a meter to make sure. The series LEDs are wired anode of one to cathode of the next. End LED's cathode wire connects to the transistor, the other end LED's anode wires to a resistor, other end of resistor goes to +24vdc.

A transistor is a 3 wire device and the wires are called emitter, base, collector. You will need access to a data sheet for the specific wiring terminals for the actual transistor you use. Example: http://www.datasheetcatalog.org/datasheet/PowerInnovations/mXvttzs.pdf Drawing shows E,B,and C leads for emitter, base, and collector leads.

All the strings of LEDs (cathode ends) wire to the collector terminal of a single NPN transistor, the emitter wires to ground on both the 24vdc supply and the Arduino ground pin, and the base terminal wires through a 1k ohm resistor to an Arduino PWM output pin.

And lastly I don't have a clue to tell you how many LED is takes to light up a room. President Lincoln when asked how long should a man's legs be, said "long enough to reach the ground". ;)

PS: Keep in mind all my string info (number of leds per string and resistor size) was based on standard red LEDs, other colors will have different resistor size and possibly fewer LEDS per string.

Lefty

Also instead of using that 100 KVA 24vac transformer you have (much overkill in size and weight) you would probably be better using a 24vdc wall transformer/supply. Here is a great buy, just cut off the connector and solder the power wires to your circuitry. http://www.goldmine-elec-products.com/prodinfo.asp?number=G17256

Lefty