wiring help needed (Ultimate FX sabre sound board)

[boshuda21]

Hi all

I'm updating and moving this thread here as I later realized it probably didn't fit well in the parts forum (sorry about that).

OK, so I am trying to wire up an ultimate fx sabre board to drive a green Rebel LED, using a 4x AA battery pack. See scheme. I have wired up the on/off/test switch because I couldn't get a bypass to work. I may make a slot for it on the sabre or just leave it in the hilt switched to on.

Aidan wiring 2.jpg

I still have unknowns

1) Is it necessary to bridge the LED holes on the board or can I just wire a single one? I don't have the switch so I can conveniently check the current/voltage running through a single LED pad at this point. I have seen/read it done both ways, but no comment was made as to whether one way is better than the other.

2) Do I need a resistor? My calculations say I need a 1.8 ohm resistor, 1.8W, but I have heard some say that these boards can tolerate power from 3-4X AA batteries. Any comment on this? If I do put a resistor in there, should it go just upstream of the LED or between the battery pack and the pwr+ pad on the board?

3) Does the clash sensor have polarity or can I wire it to A and B in either direction?

4) The stock speaker on this board is 0.25W. Now, if I put a 2-3W bass speaker in there, it shouldn't affect power output from the board provided the resistance of the speakers are the same, right? the 2W is just the max output of the speaker, right? The impedance on both speakers is the same.



thanks

[boshuda21]

I was really hoping I could get some advice on this. Did I do something unknowingly wrong or does nobody have any knowledge regarding this?

Well, in the event someone can help, I'll provide an update.

So I have wired up everything except the clash sensor (more on that later) and I have the LED working, though I don't have a resistor so I only fired it up for a second or two. Sound is amazingly loud so that is great.

However, I have some additional questions regarding resistors and the clash sensor.


1) Regarding resistors: I have measured an output voltage from 5.08V to 5.2V (4x AAA batteries) to my LED. Now if I want to drive my green rebel 3.4V LED at 1amp, I need (5.2-3.4/1 = 1.8ohm (1.8W) resistor.



2) Now here is where I am confused. I measured the current out (red to + and black to gnd) with my multimeter and I get a negative value of -2.22A. So I am wondering two things.

i) should I have a negative value for current here? Does it matter? My voltage across the same point is positive. Everything is wired as red for + and black for -.

**edit. I have been reading that some boards have the gnd and LED+ polarities reversed. I can easily switch the two wires in the plug if that is all is causing this.**


ii) Do I need to recalculate my resistor given the actual reading is higher than expected? Like this? *note that I use the negative value for current to get a positive value for resistance.

5.2/-2.22 - 3.4/1 = 2.4 ohm , 5 W resistor (5.2-3.4 * 2.4 = 4.32W)

or am I overthinking this? I don't want to under or overdrive the LED to the point where it is dim or fries, respectively.


3) Again, my question with the clash sensor. Is the sensor bi-directional or do I need to wire the 'thick' wire and 'thin' wire to specific terminals?Aidan 3.jpg

[boshuda21]

Ok, sorry I slipped out of this, but a connector I had wired to my battery pack was faulty and shorted out my pack, nearly causing a disaster.

I am back to figuring out this bloody board now that I had time to replace the battery holder.

So to recap, I was measuring about 2200mA going into the LED, driven by 4X AA batteries putting out about 5.1V. I wanted to drive the LED at the recommended 1000mA and calculated 1.8 ohm, 2W resistor should be used. This was independently verified by another on this thread. I wired it in series with what I thought was the positive terminal for the LED (based on my multimeter measurements), which is the VSS terminal on the board (I don't know it seems the current is coming out of the ground, but...). Just to get a sense if the resistor is working like I anticipated, I measured the current coming off the board on either side of the resistor and the drop was not what I was expecting. It only dropped about 100mA and is still running at 2000mA according to my measurements. I was kind of expecting to lower it to ~1000mA.

So at this point I am really confused. Am I thinking of this the wrong way?



I've seen econo board wiring suggest using a transistor, but they all have more elaborate wiring set ups with recharge ports and higher potential battery packs.

Any advice?

**edit** When I tried to 'correct' the polarity issue I had (see neg. current reading above) my LED would not light up, so the VSS is the negative (or ground). I still don't understand the negative reading, but at least it seems labeled properly on the board and works as I originally thought it should. This effectively changes the placement of the resistor. When I moved it to the other 'side' I get no current across the LED, but the LED lights up and I do have a potential of 3.6V. I think this is about right based on the calculation.

This leaves the issue of 'to bridge or not to bridge'

I also found a thread on this and am curious about the bridging the LED terminals. It seems that bridging multiple terminals is throwing out less current. Does this make sense? The video was by Wade Henry (not sure if he posts any more) but he said with a bridge over all 5 LED terminals he was getting 600mA, 1100mA with 3 terminals and I am getting about 2200 with a single terminal.

[Eaglebiker]

Your project is pretty much what I'm working on right now. After my son thoroughly bashed apart the LED strip I want to replace the blade, Swap to a single LED and switch the speaker. Did you finish your project? Did you bridge all of the LED's or just use one? Any problems just hooking up the new speaker?