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My Next Flux Capacitor

Flux Capacitor - Part II

I've decided to start my second Flux Capacitor replica. I learned plenty building my first (which went to my nephew Ben). I plan on updating my web site with newer, more detailed pictures of construction details I may have glossed over the first time. I've have also had requests to supply some parts and while I don't really want to spend all my spare time making parts for others, I may offer a few, starting first with the solenoid bases, since I made a mold of my replicas. Let me know if you are interested.

Flux Capacitor - Part II

RF Remote Switcheroo

In the process of planning my second Flux Capacitor build, I became aware that the Sparkfun RF Remote I used for my first FC was no longer available. Sparkfun did not seem to have a descent replacement so I took to the net looking for another option. While searching, I remembered a few of the issues (hassles) that I had with the first RF Remote. While in the end, it worked out, it was not without some struggle.

RF Remote for Flux CapacitorRF Remote for Flux CapacitorFirst, the RF IC used in the remote (nRF24L01+) is primarily intended for data communication. Typically you would use a pair of nRF24L01+ boards each connected to a different Arduino micro-controller. You could then send data back and forth between the two. In my case, I only needed signals sent one-way from the RF Remote to the RF receiver board. Additionally, the data being sent was a simple button press and not more complex streaming data. The RF remote is dumbed-down to just transmit the limited data needed to indicate which button was pushed. Unfortunately, at the receiving end you still need to program the Arduino to receive that data and then be able to interpret it to be able to use it.

The complexity between receiving push button data and more complex data was basically the same. It required that two different libraries be loaded and streaming type data parameters be setup and handled. All this to know if button #1 was pushed or not. Additionally, the remote did not handle button bounce very well. This is when you push the button once and get two pushes. My FC would run the same light pattern twice in a row if this happened.

RF Remote for Flux CapacitorSo, I finally settled on an RF Remote and RF receiver offered by Adafruit.com. They were cheap and the receiver came in three different versions. Toggle, Selector and Monentary. Check them out here.

The Toggle version is straight forward. Each time you press one of the bottons, the corresponding data pin on the RF Reciever toggles On or Off. The Latching Selector version worked like the old car radios. Only one putton could be on at a time and when you pressed another button, it turned off the first button. The momentary version was similar to my first remote. Pressing a button sent an On signal, and it turned Off when you lifted you finger off the button. This worried me a little because of the bounce issue I had in the previous version. De-bouncing can be handled in software but add more complexity.RF Receiver for Flux Capacitor I knew I didn't want the Toggle version because it allowed more than one button to be On at a time. That was not something I needed. Since the RF Receiver boards were very cheap, I go one of the Selector boards and one of the Momentary boards.

The (LED) Matrix

The different light patterns I created for my first Flux Capacitor were neat, but they lacked something. The way I designed the circuitry, I was limited to lighting the same LED's on each segment of the "Y". each time. So that greatly limited the patterns I could display. Looking into a better way of controlling the LED, I first thought of adding another set of transistors so I could control each LED individually. That got me thinking that there has to be a better way. It turns out that there is.

Maxim MAX7219 Display DriverThe hobby industry has latched on to these LED matrix IC chips, made by Maxim called the MAX7219. It is a "Serially Interfaced, 8-Digit LED Display Driver" that can handle up to 64 individual LEDs at a time. They decode digital data to drive 8-segment LEDs to create Alphanumeric characters. That's 8 x 8-Digit displays for a total of 64 LEDs.
Now, I've use 7 segment LED displays in the past so I didn't exactly know what an 8-Segment display was. It turns out the "8th" segment is the decimal point (or period). The best part about this IC is that from a design and implememntaitoin aspect, you don't need any transistors. Additionally, you only need a single drop resistor, insteady of a drop resistor for each LED.


Matrix MAX7219 Maxim MAX7219 8-Digit, LED Display Driver When paired with the inexpensive 64 LED matrix modules coming out of China, the MAX7219 can created quite an impressive show. These LED Matrix modules can be strung together creating a scrolling LED sign, sort of like a stock ticker display or scrolling marque. The amazing thing is that only one LED is actually lit at at time, but they are multiplexed so fast that the LED's you want on, all appear to be lit at the same time.

Now you're probably wondering how I'll be able to make use of the Maxim MAX7219 IC in my next Flux Capacitor. You see there is a Arduino driver library that allows you to address each individual LED. So I can map the lights in the Flux Capacitor to individual lights as if they were in a matrix and run all kinds of patterns. I dont have to worry about drop resistors or extra transistors and the wiring of the light mounting plate will be 10 times less complicated then before. While I won't be using the 64 LED matrix module in my Flux Capacitor, I was able to experament with different patterns in a small space, tweaking the patterns as I needed getting them ready for when I design the final circuit.