If you have the right letters in your name, it's fairly easy to design a cool looking (although very geeky) solar powered name tag!

This project uses a simple clock or calculator LCD. It must have one pin for each line segment on the LCD. Some complex LCD modules require ASCII data input and may require the use of a controller chip. They are not suitable for this particular project.

I bought an inexpensive ($0.99US) 6-digit display panel from BGMicro. Here is the data sheet that came with it:

Vikay 6 Digit LCD panel (BGMicro part # ACS1077)

Each pin number is shown along with the segment that it connects to. Pin #1 is connected to the backplane of the LCD.

To light up a segment, just apply either a high (+) or low (-) signal to the backplane pin and the opposite signal to the segment pin. To make the segment stay lit, you have to rapidly swap the polarity between the backplane and segment pins. From a BEAM Robotics standpoint, this is yet another use for a Suspended Bicore!

Suspended Bicore from Beam Online with minor modifications

The outputs of the Bicore maintain opposite polarities, and will flip flop between high and low at a rate determined by resistor R1 and the two .22uf capacitors. You may need to play around with the resistor value to find a cycle length that generates a solid display without blinking.

I made my first name tag using the Suspend Bicore, based on a design I saw at Ian's Beam Online site. One Bicore output line is connected to the backplane pin and the other is connected to all of the lit segment pins. I just snipped off the unused pins of the LCD.

As you can see in the photo, the Bicore was free-formed and glued to the back of the LCD. All of the lit segment pins are jumpered together. This name tag was built as a gift for my step grandson Alec.

The little solar cell is from a dual power calculator that I picked up for $4.99US. It generates over 3V in direct light from a 50 watt halogen lamp, and over 2V from overhead room lighting! Not a bad deal considering that it comes with a free calculator! :-) This name tag works very well using just the overhead lighting in Alec's room.

I built my second name tag using an ingenious circuit designed by Wilf Rigter. It is capable of displaying two different words, alternating between them about once per second.

This circuit still uses a single 74HC240 chip, but it provides four possible states for the LCD segments!

• ON all the time
• OFF all the time
• ON' for the first word only
• OFF' for the first word, but on for the second word

The backplane pin is connected to the OFF output line. The segment pins are connected to one of the other three outputs (ON, ON', or OFF') depending on when they should light up. I just snipped the pins of unused segments, rather than connecting them to the OFF line.

I initially tried running this name tag off of a small solar cell like I used for the ALEC name tag. It worked, but the smaller cell didn't generate enough current to support the display except under a very strong light source. I switched to a 24x22 Sunceram cell from Solarbotics and the name tag now works very well (even under a 40W incandescent bulb on my desk at work).

Other than the LCD panel and your choice of Solar Cell, the parts for this project are fairly common and can be purchased at a number of electronic stores on and off line.

Updated: 30 December 1999

Back to top