This is an exercise in using 6 Siemens/Osram # DLG 2416 4-character green LED displays with storage, selection, dimming, and decoding. Shift registers are used to interface to reduce pin count.
It is basically a multi-timer alarm clock, with limited message display capabilities. The timer outputs may be set either for message display, sounds, a controlled line output or an RF transmission.
The design also a photocell for auto-dimming. It is controlled via an 80-key PC keyboard, which transmits via IR to its supplied receiver. Additional significant items are a LM34 to sense temperature and a real-time clock module using a Dallas DS-1307 IC, crystal and battery.
It has eight display modes. There are one for time and temperature, one to adjust time and date, One to set the 8 timers, four for messages stored in EEPROM and one for a messages stored in the DS-1307. The messages can be changed using the keyboard.
There are two Picaxe processors. A 14M2 Control Processor handles the keyboard. An 18M2 Display Processor does the rest. Data is transferred between them by the Control Processor writing to the additional RAM in the DS-1307 RTC. The Display Processor reads this data.
The temperature sensor has an amplifier adjusted for accurate readout. It is located outside the box and thermally insulated.
The real-time clock was originally set with an ad-hoc program. Since its battery is supposed to be good for seven years, adjustment was provided only to increment or decrement by minutes to correct for drift, and by hours for daylight-saving time.
The original design in 2007 used an IR remote control module for control via a TV remote control. It was the blocking nature of the Picaxe IRIN command that required the separate 14M2 control processor.
In 2013 the RF transmitter module was installed and the timer action options augmented to transmit date/time and control messages.
In 2015 software was added to transmit a data message every minute which contains the current time and date.
These are keyboard instructions
These are photographs of the LED Display:
Here are the circuit diagrams
|Here is the 14M2 code
|Here is the 18M2 code