Using a transistor as a switch/amplifier with a Force FX board

[Matt Thorn]

I hope the experts are rolling up there sleeves on this one!

As do I. I have a feeling it's the presence of the clash sensor on the positive lead that is gumming up my seemingly perfect diagram.

[Rhyen Skytracker]

You should be able to get that set up to work using a PNP transistor and use one of the 6 negative wires from the FX board to go to the base of the transistor and the batt + go to the emitter of the transistor and the collector of the transistor go to the BCD rotary switch and the - of the LEDs go to the battery -. I don't think it will work right (even using NPN) by using the VDD off of the board. Try this set up and it should work.

Also, if you want to get colors that you can tune to the color that you want try using a single pole 8 position switch and for the mixed colord use diodes to keep the voltage from backfeeding and messing up your other colors. I am working on a project like that now but haven't gotten to the diode part yet. I was able to get 6 colors by using a 2 pole 6 position switch. By doing it this way your colors can be what ever you want them to be and not predetermined like with a BCD rotary switch.

[Matt Thorn]

Thanks, Rhyen.

You should be able to get that set up to work using a PNP transistor and use one of the 6 negative wires from the FX board to go to the base of the transistor and the batt + go to the emitter of the transistor and the collector of the transistor go to the BCD rotary switch and the - of the LEDs go to the battery -. I don't think it will work right (even using NPN) by using the VDD off of the board. Try this set up and it should work.

When I started this, that's what I planned to do. I don't remember the details, but the reason I went with the NPN set-up had to do with the RGBA factor. I think I couldn't figure out how to get the RGBA, rotary switch, and Force FX board all working together with a PNP transistor. Next time I get a chance, I'll try the PNP set-up with a single-color LED.

Also, if you want to get colors that you can tune to the color that you want try using a single pole 8 position switch and for the mixed colord use diodes to keep the voltage from backfeeding and messing up your other colors. I am working on a project like that now but haven't gotten to the diode part yet. I was able to get 6 colors by using a 2 pole 6 position switch. By doing it this way your colors can be what ever you want them to be and not predetermined like with a BCD rotary switch.

I keep hearing this, but exactly what kind of diodes are we talking about? (After all, an LED is itself a diode.) I've done some studying on Zener diodes, and I don't see how these can be useful here. They are used to regulate voltage with low-current applications, but with a saber, where you use low voltage but need high current, you would need a Zener diode with a low voltage rating and extremely high wattage, and such creatures apparently do not exist. One person who suggested I use a "diode" offered as examples a Zener diode and a rectifier diode, but the latter is used to convert AC to DC. Are people using these in ways they weren't intended to be used? I would love it if someone would explain this to me (based on actual experience, rather than just assumptions). Actually, what I would really love is for members who are really experts on things electrical and electronic would do a series of tutorials on stuff that could be useful to sabersmiths.

[Rhyen Skytracker]

You shouldn't have any problems using the PNP with the rotary switch.

As far as the other way with the diodes I just got normal diodes, not zenner diodes. I just don't want it to allow the voltage to backfeed. Lets use purple for instance. With purple you need the red and blue (resistor the red on that position of the switch to get the shade of purple you want too) but when you turn the switch to go to just the red position with out the diodes the blue LED would still come on too. The diode would keep the voltage from backfeeding and give you a red when on the red switch (plus this way for the red only you can remove the extra resistance that you used to dial in the shade of purple you want and have a bright red instead)

I will be sure to make a video and take pictures when I do mine.

[vargose]

You can use diodes to increase the voltage drop on the red and amber lines. Which will keep them from hogging the current. You may need more than one per line to get the drop you want.

http://www.kpsec.freeuk.com/components/diode.htm

Forward Voltage Drop
Electricity uses up a little energy pushing its way through the diode, rather like a person pushing through a door with a spring. This means that there is a small voltage across a conducting diode, it is called the forward voltage drop and is about 0.7V for all normal diodes which are made from silicon. The forward voltage drop of a diode is almost constant whatever the current passing through the diode so they have a very steep characteristic (current-voltage graph).

[Matt Thorn]

As do I. I have a feeling it's the presence of the clash sensor on the positive lead that is gumming up my seemingly perfect diagram.

It just occurred to me (as I sit here at my desk at work) that if I have the positive side of the clash sensor attached to the positive lead from the regulator, instead of to the positive lead from the board to the transistor, the weird behavior I'm getting might be solved. In other words, the fact that there is a ground from the board between the positive from the board and the transistor is keeping the transistor from doing its job. Just a theory until I actually test it.

Oh, and the correlate is that the negative lead from the clash sensor should be bundled with the other negatives.

EDIT: Doh. The negative lead remains as is between the board and the sensor, and the positive lead gets connected to the positive from the regulator.

I think.