T&L Publications

Wow does this topic hit home. My seven year old son is struggling in second grade, as I'm finding most of his classmates are. They have touched on everything from basic addition/subtraction to multiplication, division, fractions, and geometry that half of my generation couldn't figure out in 7th gra...

The photocells all tested good, within an ohm or 2 in my test setup. For the cells I used one LED to test, for the LED's I used one cell. I still don't know why that was occuring with the end LED, I wouldn't have believed it either but myself and two other guys that were here saw it, it was a visibl...

OK, I tried an experiment with what I had. I set up a test rig that held 1 LED at a set distance above a photoresistor that is hooked to a meter. First I hooked the LED to 4 of the AG3's, just as it is in the flashlight. The 4 AG3's measure 6.1V. Figuring the LED spikes when first turned on, I let i...

I'm taking a guess based on the fact that I know they will have to be driven pretty high, which is why I tried these as they came from 6V (6.1 measured) penlights (even though I know there is some current limiting in the button cells, I figure the Vf has to be on the higher end). I have a temp gun h...

Well, I went a little different route and built a small filter/regulator using an LM317. I adjusted my 21V wall wart down to about 16 and threw in a 10 ohm resistor for good measure, all the little lights seem to be happy. Colors were visibly a little varied but they all were bright, using a test ph...

Thanks for the kind words! I tried that LED wizard, though I've used a few other online calcs I do like that one as it gives more info. If you consider that all the LED's are from the same brand/model dollar store penlight, I guess you could say they should all be the same. Of course, the reality is...

Wow...thanks for all the quick replies! Lots to think about. For a better idea of what I'm working with, below is a pic of the setup. This was taken shortly after the original build, as I said it worked flawlessly for quite some time. The CDS photoresistors (I should have made that clear at first) a...

This is probably simple, but it's driving me nuts... I built a light bar for a photocell-based timer setup for a slot car track. I used 4 white LED's from some pen-type flashlights, however after close to a year of very reliable use now one is getting too dim to drive it's photocell. Cheapo that I a...

Thank you Chris, sorry if I made you go into more than you wanted to.<p>This question was originally brought up in a discussion about the magnetic force of the current-carrying rails, specifically if it could be to an advantage to arrange the traction magnets (one north faced, one south faced) accor...

Hi Chris, thanks for the quick reply.<p>I see what you're saying, but to be sure we're on the same page I'll clarify in a couple ways. I'm speaking specifically about the physical direction of flow, not the polarity. For example, say we remove a 15" power tap section from the circuit and use th...

Hello all! Nice board you have here, very informative. I'm a slot car racer and play around with electrical/electronics quite a bit, I'm always glad to find a good information resource. Anyway, I figured this would be a good place to throw out this question:<p>We often build our tracks with multiple...