Schematic review

[Rayataz]

Hey guys,

After several days of study of basic circuitry and the internal designs of various sabers, I've decided to take a crack at a internal saber schematic of my own. This is the very first time I'm building a saber from the TCSS and I'm incredibly excited to do so! (In fact, my soldering kit just came in the mail today) However, I want to minimize the number of costly mistakes as much as possible and I would truly appreciate it if others who are far more experienced at this than I am could take a quick gander at the plan I've drawn up and let me know if there are any fatal errors/mistakes that I am simply not seeing.

The setup involves the use of the Nano Biscotte as the sound board and includes FoC functionality as well as two minor LEDs. I understand that paralleling the minor LED circuits will cause the current to go from 20mA to 10mA but I can't seem to tell if that would be a significant draw of power from the LEDs as I don't quite know how they will look yet. In any case, I am truly stoked about taking my first step into the world of saber construction so thank you in advance for any advice or criticisms of my setup. :)

12065

[Greenie]

That looks correct to me. I see your LEDs are sharing a resistor, that's how I wired mine (per Madcow's tutorial) but most will tell you to put a resistor on each. I've since learned why and in hindsight it would be safer. That being said, it works fine and I'm not gonna strip it down unless/until I blow my LEDs :p

[Rayataz]

Thanks Greenie! :)

If you don't mind me asking, why is it preferable to place a resistor on each LED as opposed to sharing one?

[Greenie]

I'm using GGW in the same set up. Although the individual diodes have the same spec they may not be exactly the same with regards to forward voltage. Wired in parallel, they share the current but if one draws more it may blow leaving the the other to draw all the current so it also blows

I'm sure there are experts out there who can give you a better, more eloquent explaination (I believe Bark posted a link to a proper answer) but hopefully you get the idea :p

But as I said to myself at the time ' if it works for Madcow, it works for me'. They are, of course, tutorials for us noobs

[Silver Serpent]

Greenie has the correct reasoning. Here at saberbuilding college, we try to teach our padawans the safest method for building their sabers. Safest for them, safest for their saber. The masters do things that the rest of us don't, in the name of building some truly outstanding sabers (with even more impressive cram-fu). Sometimes, a single resistor can be the difference between a saber that closes, and one that doesn't.

[Greenie]

You're so right there SS. I had to employ the cram- fu to fit four resistors in a 2" double F between a heatsink and a chassis disc with a 12mm AV sitting in the middle :eek:

[Rayataz]

That's interesting. Well, I did order extra resistors so it may be in my best interest to parallel the resistors as well. Are there any tips you can give me for testing out my circuits before soldering them together? I'm a little apprehensive about soldering right away incase I made a mistake. I would preferably want to test out my circuit before doing anything semi-permanent.

[Silver Serpent]

Alligator clips. Watch Madcow's video on custom color mixing for details: http://forums.thecustomsabershop.com/showthread.php?18443-Video-Custom-Colors-Made-Simple

[Rayataz]

Thanks for the link, SS! I noticed that Madcow used 0.5 ohm/3 W resistors for his LEDs. Would that resistor work fine for my purposes as well? It would seem it would make the light brighter, no?

Here's my thinking:

Resistance = (3.7 v - 3.47 v) / 1.0 A = 0.23 ohms
So a 0.5 resistor seems to be okay too. The only concern I have is if you calculate wattage:
Power = 3.7 v * 1 A = 3.7 W, which is a bit higher than the 0.5 ohm /3 W resistor. Would this be a problem?

[Silver Serpent]

Your formula for wattage is off. Wattage = R * I^2

So a 0.5 ohm resistor would need a 0.5 * 1^2 = 0.5 watt resistor. Both of these would work:

http://www.thecustomsabershop.com/47ohm-5w-resistor-P947.aspx
http://www.thecustomsabershop.com/5ohm-3w-resistor-P1050.aspx

[MikeC13]

Rayataz - nice use of MS Paint! I've drawn many a schematic for my job in the exact same way, it's cool to see someone else do it...

http://stinglproducts.com/techinfo/techinfo.htm

[Rayataz]

Your formula for wattage is off. Wattage = R * I^2

So a 0.5 ohm resistor would need a 0.5 * 1^2 = 0.5 watt resistor. Both of these would work:

http://www.thecustomsabershop.com/47ohm-5w-resistor-P947.aspx
http://www.thecustomsabershop.com/5ohm-3w-resistor-P1050.aspx

Ah great! Thank you!

[Rayataz]

Rayataz - nice use of MS Paint! I've drawn many a schematic for my job in the exact same way, it's cool to see someone else do it...

http://stinglproducts.com/techinfo/techinfo.htm

Thanks MikeC13!

I tried making clarity the most important thing in such diagrams. But it doesn't look anywhere as good as the ones you've done. lol. In any case, I hope my schematic will help others who are seeking to make their own sabers for the first time as well.