This is version 2, which was originally designed as the target of my development. This became version 1.īut the 8-pin chip has 6 I/O-pins, therefore also 3 timers can be implemented in this small chip. For stability a crystal can be used, but for a lot of application (as for the coffee machine) the internal oscillator is good enough. Later the real NE555 replacement was added: an 8-pin microcontroller with 1 timer. This prototype timer went into the source as version 3.

To create a more universal timer now 3 outputs for the timers plus 1 for the LED are available and the timers became independent. Also the timers were locked against each other. Originally there were only 2 outputs: a flahing LED to signalize setup and the water-valve. For the coffee-machine 3 push-buttons were needed and a button to initialize the setup routine. I first started with a PIC16F84A, the type of microcontroller I used most often at that moment. This was a very time-consuming job as the filling of a pot lasted a few minutes and the proces had to be repeated a couple of times.

repaeat the procedure until you are satisfied.

if the coffee-level is not OK: turn the potmeter a bit.

The calibration procedure of the NE555 timer was as follows: The main reason to replace the NE555 timers were incovenient calibration and because of electrolytics in the circuit the long-time stability was not so good. Now, a couple of years later, I think the idea may be usefull for other hobbyists.

But the timer never came into production.

Original designed for a coffee-machine containing 3 NE555 timers for 3 different keys: cup, half pot, full pot. Not exactly a drop-in replacement for the good old NE555, but usefull for many timing jobs where a delay of seconds until hours is needed. Simple digital timer as NE555 killer in many application were accurate timing is required from seconds until hours.

How to program pic12f629