It is been awhile - and I finally got most parts from Amazon.
I tested the leds and saw that the red and orange are 1.8V and the blue are ~2.8V, little bit lower from the values published by the seller.

So If I will use 12V 2a power supply and will build it as recommended above - 25 strings of 4 leds (mix of red and orange), 1 string of 2 blue leds (for the eyes):
Would it be OK (and bright ) if I will use 240 ohm resistor for each red/orange string and 320 ohm resistor for the blue string?

And one last question - I have this PWM motor that I've used in different project. can I use it with this setup as dimmer?

https://www.ebay.com/itm/351491759896?ViewItem=&item=351491759896

Thanks for the explanation and guidance
Zohar

Personally, I'd stick with 270 ohms, or even step up to 330 ohms because of the lower Vf values. Human vision perceives brightness in a logarithmic way, which means you can reduce the current significantly with very little visible difference in perceived brightness. Running LEDs with lower current makes them last longer and fade slower... so in the long run you might actually have brighter LEDs by running lower current and fading less over time!

Your plan runs them right at their rated current of 20mA, which is ok, but seems unnecessary. Either way is fine, but if it were my project I'd go 270 or 330. Maybe you should make one string each with the three different resistance values and see for yourself how small the difference in brightness is.

 

@ebeowulf17 - I will do as you suggested. I will make 3 strings and will compare.
All that's left now is to make this thing

Glad I found this forum!

Thanks

 

@ebeowulf17 - I will do as you suggested. I will make 3 strings and will compare.
All that's left now is to make this thing

Glad I found this forum!

Thanks

Indeed! This forum can provide a whole lot of expertise and insight in many areas.

 

Well, almost six month since I started this thread and during the past week I found some time to finally work on this project.

Posting here the final result

I wanted to thank you for your help and advice!

--
Zohar

 

All I can say is that looks AWSOME!!!!
Not good but a Great job
Bet the kids are going Crazy over it.......Well done.

 

The most important thing for is to keep it safe since it is going to be in my kids room.

Safety is ALWAYS the most important thing regardless of where the circuit is to be used.

As for brightness: I recently stayed in a motel. The TV was connected to a cable box. The box had a single blue LED that was always on. At night it was as bright as hell and damned annoying. Since I didn't have any tape with me I took my deodorant dispenser and pulled the label off, then tore it into strips so I could apply layer after layer until the brightness didn't bother me. I wonder how other guests felt. I stayed there 9 months while on job assignment in Milwaukee Wisconsin.

I like the idea of powering it with a much lower current. Do you have any idea how much light 100 LED's will produce? Even at low currents around 5 mA, that's still a lot of light. Unless you want it to shine a batman symbol on the ceiling.

 

Safety is ALWAYS the most important thing regardless of where the circuit is to be used.

As for brightness: I recently stayed in a motel. The TV was connected to a cable box. The box had a single blue LED that was always on. At night it was as bright as hell and damned annoying. Since I didn't have any tape with me I took my deodorant dispenser and pulled the label off, then tore it into strips so I could apply layer after layer until the brightness didn't bother me. I wonder how other guests felt. I stayed there 9 months while on job assignment in Milwaukee Wisconsin.

I like the idea of powering it with a much lower current. Do you have any idea how much light 100 LED's will produce? Even at low currents around 5 mA, that's still a lot of light. Unless you want it to shine a batman symbol on the ceiling.

As a matter of fact, I am quite aware of how much light even lower powered LEDs produce. Presently I have a thread going about failed LED tube lights, and what I can tell you is that going from 3.0 forward volts to 3.3 forward volts doubles both the light output and the current, and cuts the LED life before total failure down to just a few months, from many years. LEDs are diodes and they are very non-linear.

 

Yes @MisterBill2, I'm aware of your thread. My point was being directed at zohara. A batman light with 100 LED's will be (probably) as bright as a regular lamp.

 

Yes @MisterBill2, I'm aware of your thread. My point was being directed at zohara. A batman light with 100 LED's will be (probably) as bright as a regular lamp.

Actually the light is very nice, I added dimming option so with when fully power it is really bright but when dimmed to the lowest level it looks nice and not that bright and they are using it as night lamb...

 

Actually the light is very nice, I added dimming option so with when fully power it is really bright but when dimmed to the lowest level it looks nice and not that bright and they are using it as night lamb...

I am wondering about the voltage and current at the much lower brightness level. Do you have that information available?