Teensy Saber Electronics
Got Pike?
DIY Teensy based lightsaber

This is version 1 of the teensy saber electronics. It can be made entirely from parts you can easily buy, and uses big FETs which can control a LOT of current. However, it is fairly bulky compared to other lightsaber solutions. You might want to take a look at version 2 which is much smaller, but harder to make. (But maybe you can just buy one.)

What you will need:

Circuit diagram

A few notes on the circuit diagram:
  • The battery looks like a flat li-poly battery, this is just for illustration. In reality you almost certainly want an 18650 li-ion cell.
  • The voltage booster shows a model from Adafruit, but it it is too big for most hilts. I use this one instead.
  • The SD card holder shows 6 wires, but the white, yellow and gray wires are actually pins, holding the SD card pcb in place.
  • The WS2811 LEDs are shown as having a green PCB, while in reality you'll have through-hole LEDs or strips.
  • The circuit diagram shows two buttons and one touch button. Three regular buttons also work, or some of the buttons can be skipped.
  • Three FETs are shown, but each FET is powerful enough to drive a full PL9823 string, so if you don't plan to build any of the blades that requires three high-power channels, you can skip some of the FETs. If you only have one FET, connect it to at least 2 pins in the aviation connector as they are rated for 5 amps per pin.
  • There are a lot of choices FETs. If you want to get different ones, make sure that the gate threshold is below 3 volts, or the teensy is not going to be able to control it properly.
  • The battery-to-teensy resistor is used to read the battery voltage. I used a 23kOhm resistor, but anything from a 10kOhm to a few hundred kOhm will work. If your resistor is not 23kOhm, you'll need to find the line that says float pullup = 23000; in the code and change it to the correct value.

Putting it together

Important! Make sure you cut the lead between VIN and VUSB on the teensy before you solder it to the prop shield. Cutting it afterwards is not nearly as fun. (But possible with a dremel and small engraving bit.) Once VIN/VUSB is cut, you'll need to provide external power to use and program the teensy. Also, DO NOT connect the 3.3v pads on the sd card adapter. It's easier to just feed it 5 volts.

Now place pin headers on the prop shield in the following locations:

place pins in slots marked with red

Then put the teensy 3.2 on top of the prop shield and turn it over. Now, carefully push the pins with a metal tool until they are flush with the bottom of the prop shield. If we don't do this, the pins will not be long enough to attach the sdcard adapter. (Thus, if you're not using the sdcard adapter, feel free to skip this step.)

Solder all the pins into place, both on the bottom of the prop shield and on the top of the teensy. Now we need to cut "pin 2" because we don't want it to connect to the SD card adapter.

pin 2

Next, cut three short wires, strip the ends and solder them to the MISO, MOSI and CLK on the sd card shield. Put the sdcard shield in place (but don't solder it yet). These wires are going to connect to pin 12, 11 and 13 on the teensy AND the prop shield, so cut and strip them to length, make sure that you strip enough that the cable can go through the teensy and down to the prop shield, then solder the wires in place, both on the bottom of the prop shield and on top of the teensy. Now, solder the sdcard into place.

I later replaced the wires with thinner 30-gauge wires, which works better.

I recommend bending the pin at the "A14 / DAC / Audio In", this will keep it from poking into the battery, while still protecting the reset switch from getting pressed accidentially. The other pins will probably need to be cut down a bit to fit. But again, it's probably better to not cut them too short, as that makes it more likely that the reset switch will be pressed accidentially. The FETs can be arranged any way you want, I cut a small 2x13-hole proto board to hold the FETs. I used the spaces in between the FETs as power bus connectors, one for the positive side and one for the negative side.

The sparkfun lipower power booster is the smallest I could find, still it was too big before I removed the battery connector and soldered in wires instead. Once I did that, it fit snugly to the side of the teensy/prop shield/sd card sandwich, which made the whole thing fit better. I also found that the capacitor hooked up to the under-voltage lockout pin causes problems if the voltage suddenly drops by as little as 160mV, which happens all the time when you turn the saber on. To fix this problem, remove the capacitor shown here:

The rest is all done with wires, I recommend thin 28/30-gauge wires for all the cables that connect to the teensy and it's power booster. The wires that carry power to and from the FETs should probably be a little beefier, about 24-guage or so, anything too big is going to take up too much space.

When it's all hooked up, it should look something like this:

This was before I removed the connector from the booster.

A note about batteries
At first, i tried using a 3200mAh protected battery that supports 10A. It's a good solid battery, but if it wasn't fully charged, the protection circuit would kick in when I turned on all the LEDs at the same time in the PL9823 blade. I am now using an unprotected battery that can provide 20A continuous and 100A peak. Such a battery should be respected as it can make any wire glow white hot if short-circuited. If you want to use protected batteries for the extra safety, make sure you have some head-room, because WS2811 and PL9823 can draw more than it says on the data sheet when you turn them on. Also, batteries that are rated for high current will have lower internal resistance, which means that the voltage will drop less when you put load on them. This is an important consideration for this electronics, since it does not have buck-boost driving circuits, and the brightness of the LEDs will drop if the voltage goes too low.

Other options
The SD card is optional. You can use he serialflash chip on the prop shield to store the sounds instead. It's not very big, so you'll probably only have space for one or two fonts. (In fact, some sound fonts are bigger than 8Mb, and would not fit at all.) Another option is to use the Wiz820+SD adapter. It is bigger, and the SD slot points the wrong direction, but requires no wires. Finally, there are a bunch of teensy add-ons on Tindie that could be used, some of which are much smaller than the parts I've used, but I have not found one that includes an amplifier, so you would need to do that with a separate board. If there is enough interest, I'm probably going to try to design my own board, which would make the whole thing much smaller.

If you're having problems, check out the troubleshooting page.

Problems? Questions? Suggestions? Check out the fx-sabers online forum.

This page has been accessed 1,525 times since July 25th, 2016.
Last modified: March 11th, 2017 - Design by Monica & Fredrik Hübinette