hasbro lightsaber salvage/ reconfigure to 12 volts help

[Buryaman]

Good day/evening, fellows with the force.

I'll be straight to the point: having seen the diagrams in the 2010 hasbro economy sound card diagrams and the cheap-o setups that run single high power LEDs, I thought for a moment that maybe the TIP42 transistor and the 7805 regulator can be used in such a way that the board won't be fried and the LED blade would light up with the effects.

backstory: I rewired a hasbro mace windu saber (this one has blue leds, momentary switch, built in swing and clash sensor, and has the surprising - surprising at least for me - ability to run LEDs off of its speaker output straight up) with a *shudder* 317 regulator/s and a couple of 100 ohm resistors. I thought the regulator hooked up on the LED output ground would be isolated from the 12 volt circuit.

In short, I ran the card off of a 12 volt lithium polymer battery - not unlike those used for RC machines and airsoft blasters - and proceeded to summon the great big god of gray smoke. BLOODY BRILLIANT!

The LED strip I'm using is a commercially available 12 volt automotive strip light that is glued back to back and diffused with opaque wiring spiral and draws about 1 ampere on a li-po battery.

(don't worry, the lipo is secured inside a shell that fits inside the hilt that cushions hard blows, drops, and violent movements... it's the only power supply that brings out the darkness-smashing brightness of the automotive strip lights)

Now, having seen the diagrams,I have a few questions: would the TIP42C and the 7805 do the job?

I saw that the 7805 would have to dissipate the extra voltage as heat so I fully intend to heatsink the components (including the 42C)...

here's what I need the setup to do: isolate the card at 5 volts, allow full 12 volts to flow through the transistor and power the blade, and not self destruct in the process.

here are some piccies. wiring diagram 1.jpgwiring diagram 2.jpg

[Buryaman]

here is a picture of the "Dwarven Lightsaber" that runs on a lipo... and her sister, a Kagemitsu G4. GEDC8889.jpgGEDC8896.jpgGEDC8899.jpg

[Silver Serpent]

The wiring diagram appears correct to me. Assuming your TIP42C will support 12v (check the spec sheet, I honestly don't know), you should be able to do what you're suggesting.

[Buryaman]

did a little research:

the TIP42C (the one available in my country) is rated for 40 volts max at the emitter-collector end. so that checks out.... max collector DC current says 6 amperes so yeah...

the 7805 says it's 7-25 volts input; output 4.8 - 5.2 V average 5.0; max rated current 2.2 amperes - the board doesnt draw that much current, so yeah....

thanks to silver serpent for the heads up!

reference links: TIP42C/G data sheet http://www.digchip.com/datasheets/pa...343/TIP42G.php

LM7805 regulator https://www.sparkfun.com/datasheets/...nts/LM7805.pdf

[Obi1]

Hi Buryaman,
Good to see people doing their own electronics.

One remark (it occured to me last evening, for some reason the Force wanted me to remember your thread ) - the TIP42C is a PNP bipolar transistor. In my opinion if you apply the 12 V either to the Emitter or Collector, it will pull the Base to it -> the great god of Grey smoke will visit your humble home again. So before you apply the full 12V, try to use a PS to increase a voltage slightly above 5V (say 6V, with that the electronic will still survive) and observe with a multimeter the board voltage. I recall I tried it one with a Hasbro board and since that board also used bipolar transistors to drive the LED strings, when I raised the voltage above 5V, the voltage increased. Reason is that the bipolar ones can act as diodes (not isolated like MOS) and the voltage regulator can push up the voltage, but not down!
That is why I always prefer to use MOS (in this case a pMOS).

[Buryaman]

interesting... so that's what fried the on board amplifier....

current build as it stands, there's a big LM324 op-amp somewhere in the sled (i used a sled to house the 3 lithium cells for the led strip and along with the electronics - this eliminated the "cram fu" out of the equation by jamming the package in LOL) and a 1 watt 8 ohm speaker that surely sounds louder - but barely better- than the stock speaker.

there are also 2 voltage regulators: a 7805 and a 7809 to drop the voltage sequentially and spread the heat along the two chips. heh, linear regulators. what can i do with them? haha. buckpucks aren't found here and if they are found they are for 36-24-12 volt varieties... =(

i ditched the TIPs and went with a logic mosfet: the FQP3060L (or something) and had a reliable operation: i was able to control a led strip using another 3-volt sound card from a chinese lightsaber that made only 3 sounds whenever the momentary was pressed.

revision was to drop voltage down to just 7.4 because it was too hot and too long for a movie based hilt (tried fitting the sled to a vader hasbro, wouldn't fit lengthwise)

and i found cheap LED collimator lenses that didn't break the bank - 200 pesos / 4 USD, running very bright at 6V tops with a 12 ohm 5W resistor for the 1 watt led that sure likes to make a light show: that small thing is so bright it left a spot in my eye for a good 5 minutes. the shop lady was kind enough to let me have the whole setup and threw in some extra leds as well. (i'm going back to that shop for my future needs)

thanks for the heads up Obi1. wasn't able to survey the forums lately because exams are coming up. =)

[Obi1]

Glad I could help. So now you've built in a mosfet, did I read correctly?

[Buryaman]

yep, it has a mosfet, and the setup actually does work.

but for simplicity's sake (the whole thing doesn't fit in the hilt which is already 32mm wide) i decided to forgo a soundcard-driven setup and instead mounted a momentary switch on top of a latching switch using epoxy and good old fashioned cuss words. this enabled a fully electrically isolated led string from a 7805-regulated sound card sans the flickering effects.

also i can show how it was done =P

i will post in the "instructables" section of the forum later.