LED Resistor Selector Dial

[inobu]

Getting the LED portion of the project in order and found this to be interesting. I think I'm going to make one as it looks handy to have away from the PC. 

 

 

Here is the link to the build

 

http://adf.ly/HGcRY

 

Inobu

Edited August 18, 2016 by inobu

[inobu]

I would really recommend making one of these as it brings up a revealing anomaly based on technology. It was a time where I had memory space in my head for phone numbers. I knew all of my friends and relatives numbers, other national and regional locations (28) from work and a slew of others. That memory space is virtually unused today. That space has been replaced by my cell phone and I think its just unused memory space now.

 

This device is pretty much a slide rule but I noticed that it stimulated thought. Using both sides of the wheel you are forced to reason out the given value. Although simple these extra steps invoked thought. When I tested the wheel against the online calculator I found myself punching in numbers and waiting for the banana verses using the wheel. 

 

I encourage you to take time and make one of these as its really causes one to ponder the effects of technology.

 

Inobu

Edited August 18, 2016 by inobu

[cteno4]

I just do the math, usually very easy. Just subtract the LED voltage fro your source voltage and the multiply by 50 (or devide by 0.02 as most all LEDs we use are 20mw). I usually round down a bit on the LED voltage to not run it at 100%as rarely do you want them full blast in model lighting and it just makes sure the LED lasts. I actually find most of the time LEDs in most model lighting situations need to be cut back and it's one of those things you need to fiddle with in place. Hence, I tend to just wire a limiting resistor (to not fry it) and a variable resistor in series and then just add restance to get the LED to the level needed.

 

Like you said modern life tends to get us to not think thru the calculations usually with an app for that. Basic electronic calls like this I find though keep me on top of how it all works. P = I x E and V = I x R are my friends and keep me sharp. Simple math and understanding coming with the calculation.

 

It was funny the other week I got jury duty and was on a trial and in deliberations we needed to calculate some stuff and had no electronics (they take them all away) and I had to do a bunch of long division and larger multiplications. Most of the time with that stuff I get away with fast in my head estimation that is almost always w.in 5% and did this here for our discussions but when it came time to write down the final verdict two of us had to do all the paper math to be sure, and it took a second to get going but at least we agreed on the exact numbers and the estimates were right on!

 

Jeff

[inobu]

I made one and its pretty neat. Its back to the days of slide rules which makes one think.

 

 

I encourage all to make one.

 

Inobu

Edited August 18, 2016 by inobu