Flip the pixelmap for the message board to be readable at the top or bottom (there is a #define constant already in code to select). The FSK modulator circuit shown above will function fine with RS232 either in the standard signaling format (-3 to -15V low, +3V to +15V high) or TTL levels (0V low, +3.3V to +5V high). The diode at the base of the transistor clamps the base of the transistor to ground to prevent negative signal voltages from causing damage to the transistor. I used the Schmitt buffer oscillator instead of a 555 timer because I anticipated a possible need to switch the transformer coil at > 500KHz, which is beyond the capabilities of the 555 timer. Also cheaper 555 timers actually tend to be 100KHz versions. For the POV display, I decided to modernize a little and use an ATMega328 with the Arduino Uno bootloader and program it using Arduino code. Writing Arduino code in C code style is way easier than writing, deciphering, and debugging PIC assembly! Granted, I did not write most of the PIC assembly code for the first 3 versions, but they were not necessarily easy to understand and modify. Furthermore, the Arduino supports an UART so I was very interested in the idea of transmitting RS232 to the Arduino on the spinning POV board for all types of purposes including a live message board or possibly a pixel graphics display controlled by a PC or setting/resetting the time over RS232. Several POV display examples I have seen used an IR remote for changing display modes. To transmit messages, a radio like the Zigbee is typically used. I was more interested in something more basic and inexpensive so I looked into rolling my own RF transmitter/receiver since RS232 is very simple and only needs to be transmitted from the stationary base to a spinning board with an antenna at most a few inches away. While looking into the radio design details, I was worried about trying to detect a weak RF signal in the presence of a large interferer caused by the switching frequency of the air-core spinning transformer. I had my eureka moment when I realized that all I really care about is transmitting RS232 in one direction. That pesky transformer switching frequency noise could be made meaningful to send RS232 bits by shifting the frequency around! I designed a basic Frequency Shift Keying (FSK) design where a logic 0 or 1 is represented by 2 different transformer switching frequencies as shown in the diagram below. Note that the inverters are Schmitt buffers, which is required for oscillation due to the hysteresis on the input switching thresholds. The obvious solution to the DC motor problem is to use a brushless DC (BLDC) motor for quiet long-lasting operation. BLDC motors are commonplace in the quintessential PC fan that are everywhere and inexpensive. Unfortunately, trying to source a simple brushless DC motor by itself without any attachment to something else like fan blades, disk or CD drive turns out to not be as easy as I thought. I even considered the BLDC motors used in quadcopters, but those are designed for very high RPMs and require a separate motor controller that typically expects PWM. Furthermore, I did buy and play around with a quadcopter BLDC motor. It turns out that running a quadcopter BLDC motor at low RPM produces a high pitched whine, which is clearly unacceptable for a display that is not supposed to annoy everyone near it. In the end, I decided to use a 60x60mm PC fan as the motor and designed a base PCB around it.

Cut a piece of wire and strip both ends (small strip lengths). The wire should be long enough to connect the solder from step 3 to the top transistor solder/strand. Mechanical assembly plays a main role in proper functioning of this project. The display is displays the time by rotating the whole assembly in a circular path. Here a major challenge that we faced is the connecting +5V supply to the rotating circuit. We tried the various methods to do that. But finally we choose a method, as shown in the above figure.Choose one end of the Pcb board to work with. On this side, you will place the first LED in the 7th hole of the first column (see photo). Place the rest of the LED's as shown. When placing LED's in the holes, the positive end (the longer metal leg) should go in first. See the picture for reference. Connect the programmer to the debug header on the POV Display board just like shown in the first video for the Scrolling LED Message board. Be sure power is turned off on the base PCB and also obviously the motor. The programming header on the PCB actually ties the 5V pin directly to the power rail of the POV board rather than into the regulator. This is because the design originally used 5V for everything, but 3.3V is used now on the POV board for better regulation. 5V can still be applied without damage for programming only. If you have 3.3V programmers or Arduino boards with RX/TX that you'd like to use then you can apply power to the base PCB so the POV Arduino is powered and tie GND/RX/TX to the programmer. tape, which no longer serve any purpose. You will now be able to hold the inner layer in place with a few spots of glue. Display pixel graphics transmitted from the PC. Instead of translating a RS232 character as an ASCII bitmap, the RS232 character could potentially represent pixel values in a column. A PC running software (C code, Python or your favorite script, LabVIEW, etc.) could translate images into RS232 messages that this display could show. All types of motors used to convert electrical energy into mechanical energy. Motors can be found in VCR’s, CD players, toys, robots, fans, etc. The motor performance is very important in circuit design. This is because the electrics motors directly affect its speed and pushing capability.

According to above calculations, it can be interpret the radius is proportional to the rotation speed of LED s. Interrupts This devise displays only the time. Therefore we can modify this devise for display date besides time. delayMicroseconds(100); // for LED pixel width (change the value according to motor speed. Increase for low speed, decrease for high speed motor)Before cutting any strands, make sure the LED's are all straight. if a few seem crooked, just apply heat to the solders you made to straighten them out. Careful not to burn your fingers!