Using the Red Lion quadrature counter module to display incremental encoder outputs Red Lion Controls manufactures a neat little prepackaged LCD display module that can be used to read and display the output of incremental linear and rotary encoders. below are some application notes that might be of some use. A GIF file accompanies this text file with a simple diagram of a typical setup. The counter module is available from Digi-Key Corp. It's the Red Lion Sub Cub D quadrature counter (digi-key p/n RLC05-ND $29.00). You'll need the Bezel kit that includes the PC board and cable (digi-key p/n RLC10-ND $24.00). Two 47k resistors and a push button switch are needed to enable the reset function of the module. You may need a couple of 100k resistors to pull up the outputs if your encoder has open collectors (most do). If the outputs of the encoder are line driven, it wouldn't hurt anything to pull them up anyway. It might even eliminate any noise problems encountered in your wiring. Encoders that can be used with the Red lion should be 5vdc TTL square wave output, although 12vdc encoders can be used if you are willing to jump though some hoops. Single ended or differential output encoders are fine. We just ignore the complement outputs of a differential encoder. The module is about an inch tall and 2 inches wide. The digits are .350 high. On the back of the module there are elastomeric contact fingers that connect to the circuit board when the two are snapped together. A short ribbon cable connects to the circuit board. You can simply twist together the appropriate wires of the ribbon cable to get the jumpering needed for the functions you want. There are limitations to the Red Lion's capabilities. The counter can only read base ten inputs. IOW, it won't round out to half units. It's all or nothing. Additionally, the unit has no floating point math capability and is limited to base ten and base two multipliers. This makes metric conversions out of the question. I can tell by the look in your monitors that you're having trouble trying to grasp what I'm saying here. Let me try again. The readout will count quadrature pulses and display them by ones only, no rounding to five. What all this means is you need a encoder that sends pulses in relation to the system that you want to use, SI or English, and the last digit can't be rounded, only dropped. Rotary encoders are specified by their resolution in two different ways. Some manufacturers specify so many lines per revolution and some so many quadrature counts per revolution. The the number of quad counts equals 4 times the number of lines. Linear encoders are specified by either lines per unit of measure or quad counts per unit of measure. The module can multiply the quad counts by 2, and 4. It can divide by 10 and 100. Combined, this lets us read counts as follows. times 1 times 2 times 4 divided by 2.5 divided by 5 divided by 25 divided by 50 divided by 100 The decimal point can be placed in three positions or not used, ie; xxxxx.x, xxxx.xx, xxx.xxx, or xxxxxx. Leading zeros can be suppressed. An example in English units; Let's say we were to use an encoder driven directly from the screw of a Bridgeport and we wanted an English output. A 125 line encoder would give 500 pulses per screw revolution or 2500 counts per inch. We would set the Red Lion up to multiply the encoder counts by 4 and display them as xxx.xxx resulting in a 1/1000" resolution. If the encoder was a 250 line unit giving 5000 counts per inch, we could multiply by 2 and get 1/10000" resolution. We'd have to turn off the decimal point and paint one on the face of the LCD since it can only be placed at 3 significant digits. The accompanying GIF file REDLION.GIF shows how one would hook up the module to display a .001 resolution from an encoder that outputs 2500 counts per unit of distance. The decimal point is set to .xxx and leading zeros are suppressed. Obviously, other resolutions would have different connections. The data sheet supplied with the module contains tables that show the proper connections for various configurations. Digi-Key can be contacted at: 1-800-344-4539 www.digikey.com ----------------------------------------------------- 1996 Bob Simon