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View Full Version : New sabersmith asking some (probably) basic questions



EliHaser
06-18-2018, 11:36 AM
Wellp, hello there!

This will be my first build, so I have some questions:

I'll be using:
-A basic 3.7V Li-ion battery with PBC (3,6V-4,2V, Capacity 3400Mah, Output: 4,2V 600mA, Input: 110-240V, Over Charging: 4,2V, Max charge: 1.5C) or a 7.4V Battery Pack (with a 5V (7805 type 1.5A) regulator).
-A 12W Red Quad Led (LED Type:4pcs X-Lamp XP-E Chips, Voltage: 3V, LM:1200LM Max, Current: 1000mA-3.8A(3V), Red 3V voltage infact is 3.2-3.4V).
-A cheap soundboard (As far as I know, highest power most economy boards run off is 4.2v max) and it's speaker (which I'll later change for higher quality ones).
-A non-illuminated switch.
-A recharge port (and charger, duh) like this one from TCCS (http://www.thecustomsabershop.com/37V-Li-ion-smart-charger-with-21mm-plug-P890.aspx and http://www.thecustomsabershop.com/Switchcraft-21mm-Power-Jack-P822.aspx).

So now the questions are:
-Would a tip42c pnp transistor be fine for this build? I can only find examples using 7.4V instead of 3.7V single batteries.
-What if I used a 7.4V Battery Pack with a 5V Regulator (7805 type 1.5A)? Would I need Another resistor from the battery to the soundboard? Same Ohm's Law? I think I should, to make it at least around 4V while I'm using the cheapo soundboard, right?

-Now about the resistors for the LED. Using Ohm's Law it gives me this:
VfBattery => 3.7V ~> 4V
Max Current => 1000mA = 1A
VfLed => 3.2V-3.4V ~> 3.4V

R = 0.6V ~> 0.5 Ohm? 1 Ohm?
P = 0.6 * (1)^2 => 0.6W ~> 1W? 0.5W?

Or:
VfBattery => 7.4V ~> 8V
+ Voltage Regulator => 5V

R = 1.6V ~> 1.5 Ohm? 2 Ohm?
P = 1.6 * (1)^2 => 1.6W ~> 2W? 1.5W?

Is this Ok for every led? And if it's right, which resistor should I choose? It doesn't seem to matter which + or - I solder, and there's only 3 of each, so it's not like every led has it's own +-. Any + and - combination lights up all 4 leds in the star.

Also, I think these LEDs might actually run at 700mA and 2.3V (2.1-2.5V), as seen in their chart (http://www.cree.com/led-components/media/documents/XLampXPE-25A.pdf) or it's page in LED-Supply (https://www.ledsupply.com/leds/cree-xlamp-xpe-high-power-led-star), which looks pretty much the same as the XP-E2 Red from TCCS (http://www.thecustomsabershop.com/Red-Cree-XP-E2-CopperNova-P1001.aspx), so I don't even know anymore.

Forgetful Jedi Knight
06-18-2018, 01:31 PM
Welcome to the Forums. You do realize that this forum is attached to a store that sells saber parts, correct?

EliHaser
06-18-2018, 03:21 PM
Yup, removed the links and references to other shops. Didn't mean to be disrespectful, and of course some of this build's pieces are from here, such as the body, blade and switch. Still, even if I can easily find some items in TCCS such as this charger:
http://www.thecustomsabershop.com/37V-Li-ion-smart-charger-with-21mm-plug-P890.aspx
Or this Recharge port:
http://www.thecustomsabershop.com/Switchcraft-21mm-Power-Jack-P822.aspx
I don't really know if they're compatible with this build's electronics, or how to make them compatible. Wiring isn't an issue though.

Forgetful Jedi Knight
06-18-2018, 03:33 PM
From what you’ve posted, those should work fine.

EliHaser
06-20-2018, 12:09 PM
Updated the post. I still don't know which resistors and PnP transistor I should use, nor if my calculations are right. Thanks for the answers.