DIY Split-flap display driving circuit
by Markus on Jan.01, 2011, under Electronics
A while ago I got my hands on some old split-flap displays from a train station. Yesterday I finished driver circuits for 8 of the segments. It was only just in time to also quickly implement a clock algorithm for an extraordinary clock to display the turn of the year. Don’t miss the movie at the end of this posting.
The original driver circuits consisted of a Zilog processor, an EEPROM, an optocouppler for driving the 42V synchronous motor, transistors, two reflective IR-sensors for segment position and a few passive components. Since I do not have any information about the original interface and protocol, I decided to implement my own driver circuit and directly connect to the sensors and motor.
So each segment has its own driver circuit, built around a PIC12F683. Cheap optocouplers MOC3023/MOC3063/IL410 are used for switching the motor. The controller has to switch the IR sensor LEDs individually, because there is only one signal output for the two sensors. There are also two status LEDs and a button for debug features and for configuring the segment address. The driver boards are connected to a simple one wire bus, where they listen for commands and write status response to.
One of the greatest problem was to connect all the devices to only six I/O-pins of the PIC. I got it done by only using one pin for the two status LEDs, using the high impedance state and multiplexing for driving both of them via one port pin. Also the motor output signal to the optocoupler is formed by the two sensor LED outputs or-ed together using two diodes. Since the sensors are only needed when the motor is on, this saved me another port pin.
The clock application is quite funny, but far too loud to make a good project. So I am looking for a better way to use the displays. Maybe some kind of build status display for our continuous integration server at work.
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hackaholicballa - Driving an 8-digit split flap display
January 4th, 2011 on 05:32[...] got his hands on a split-flap display and built a controller for it. These sometimes can be found on really old alarm clocks, but [Markus] was a lucky-duck and managed [...]
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Driving an 8-digit split flap display « Black Hat Security
January 4th, 2011 on 12:26[...] got his hands on a split-flap display and built a controller for it. These sometimes can be found on really old alarm clocks, but [Markus] was a lucky-duck and managed [...]
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LilBoonjis » Blog Archive » DIY split-flap display controller
January 5th, 2011 on 14:03[...] He not only got a hold of a hardly any segments of an actual split-flap exhibit, however also managed to get them working with PIC microcontrollers driving each of the segments. The result is a perfectly whirring exhibit, [...]
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DIY split-flap display controller | Products & Tech News
January 5th, 2011 on 14:19[...] of Markus. He not only got a hold of a few segments of an actual split-flap display, but also managed to get them working with PIC microcontrollers driving each of the segments. The result is a beautifully whirring [...]
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DIY split-flap display controller - machine quotidienne
January 6th, 2011 on 01:31[...] of Markus. He not only got a hold of a few segments of an actual split-flap display, but also managed to get them working with PIC microcontrollers driving each of the segments. The result is a beautifully whirring [...]
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DIY split-flap display controller
January 6th, 2011 on 04:39[...] of Markus. He not only got a hold of a few segments of an actual split-flap display, but also managed to get them working with PIC microcontrollers driving each of the segments. The result is a beautifully whirring [...]
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links for 2011-01-05 « Donghai Ma
January 6th, 2011 on 06:03[...] DIY Split-flap display driving circuit – Markus’ Blog (tags: cool diy electronics) [...]
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DIY split-flap display controller | anythinganyhow2
January 7th, 2011 on 15:09[...] of Markus. He not only got a hold of a few segments of an actual split-flap display, but also managed to get them working with PIC microcontrollers driving each of the segments. The result is a beautifully whirring [...]
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DIY split-flap display controller | My Blog
January 9th, 2011 on 10:35[...] of Markus. He not only got a hold of a few segments of an actual split-flap display, but also managed to get them working with PIC microcontrollers driving each of the segments. The result is a beautifully whirring [...]
January 4th, 2011 on 05:06
Seeing your video made me want a split-flap display. It looks like they are hard to find used ones but if i ever come across it, i know not to hesitate and grab it.
Awesome project.