For those times when you need a numerical display but it isn’t driven by a clock or a counter, we developed this little ditty. It is, of course, multiplexed (only one digit on at a time, but the eye perceives they are all on all the time). There are a lot of examples on the Internet for a multiplexed numerical display drivers, but most of them can only operate at 5.0vdc or less. If you want to display larger digits than 5/8ths of an inch, especially in the 1.5 to 4.0-inch tall range, you will need to operate at a higher dc voltage. This is true whenever each segment has more than one LED which results in a larger forward voltage across the LEDs and thus a higher head-in voltage. Our driver can handle voltages at least up to 24vdc.
The driver pictured above receives TTL RS232 signals (not true RS232 levels). This means it can take serial signals directly from micro-controllers (5.0 or 3.3 vdc). We have provided boards that take a true RS232 signal, if that is required.
Need more than 6 digits? Use two drivers to get up to twelve. Adding extra drivers does not require additional serial ports. Just bus the serial port transmit signal to all the boards. The strings are easy ASCII numerals with a carriage control and new line feed termination. You can also select where you want the decimal point (if any) in the string command.
We recommend a grey or colored filter over the 7-segment displays to improve their contrast in bright ambient light. The pictures below show a 6-digit, 5/8ths-inch tall display with a filter and a 3-digit, 1.5-inch display with a filter. The larger display is not limited to three digits. It can display three more digits just as brightly as the ones shown. We didn’t have a display of this size in a six digits, but we had this display left over from a recent project and used it just to show the difference. This driver will handle six digits of 7-segment displays up to at least 4.0 inch tall numerals. Regarding color, the most likely colors are red, green, blue, amber and white. In the end, the main limitation for the color of the numerals is those economically available at the time of purchase.
We anticipated that someone might want to access a 7-segment display from a Windows PC. So we developed a version using USB technology that looks like a comm port on the PC. It uses exactly the same string protocol as our TTL serial version. Pictured below.
The driver board is a fixed price, but needs to be optimized for the particular 7-segment displays. See price below. For a custom design for the digital display, please call use to discuss your requirements.
- 6-Digit, 7-Segment Display Driver – $245.00