The basic digital circuits are Flip Flop and Counter, both are here. This circuit can be cascaded to make even a 6 digit event counter, even a simple frequency counter can be made.
Digital Timers, Counters and Clocks
These are best done with microcontrollers today. Then what if you have to design your own microcontroller on a FPGA, so the basics have to be sound, hence you have to know what gates, flip flops and counters are.
CD4538 is a dual Monostable Multivibrator. When you trigger the chip the output sends off one single pulse or one high-low event.
Mixed Circuits Analog with Digital
The T+ pin 4 of U1a is the positive edge trigger or raising edge trigger input, the T- pin 5 is falling edge or negative edge trigger input. Now see the image of the single pulse above which shows both the edges, If this is the input pulse at pin 5 then the falling edge turns the output pin 6 from low to high, this output remains high for time T = R2 * C1 and then goes low again, The output Q at pin 6 also looks like the image of pulse above.
When i had put the near Obsolete digital circuits online in the late nineties. One person who works in a public institution in the usa, wanted a modification of one of my existing circuits. He had those parts the CD40 Series Logic Chips. He wanted to use only those that he had in his Stock.
Digital Circuits 2 from delabs
I made some modifications and sent it to him, that helped him with his task. These things can be done very easily using an embedded microcontroller. One could make a programmable Timer/Counter with a matching Configuring Software without coding, for such people. Easy and Affordable. You could also make a pure digital chip by using a CPLD or FPGA, if that is affordable.
This circuit is alternative approach to same solution show in earlier post. Here i have put the complete circuit in PNG format. 8038 is a marvelous chip, a custom monolithic analog computation unit, a device popular around the 80s, it was far ahead of its times indeed.
Now its availability and application are much reduced. Intersil made Popular Analog ASICs, the word ASIC itself came much later. They were also early in making low power cmos, this was at a period when microprocessor system consumed a lot of power and microcontrollers had just started coming in.
Tacho Counter for Speed and Quantity Measurement
This was a small circuit made for driving an Impact counter. The heart being ICL8038. It must have been a Motor driving a Conveyor, the motor has a feedback attachment called Tachogenerator.
This was a attempt to make a Sequential Timer with ICM7217 of Intersil, even though it worked well, it was not developed beyond the prototype stage or first iteration. Only when a product is made in some numbers, the documentation and designs become clear, streamlined and seasoned.
Multiplexed Presettable Timer with ICM7217
The PCB and Circuit are not complete. It may give ideas. During this time, as far as i can remember, these were the only large CMOS devices. 8080-85 and Z80 devices consumed lot of power and needed big boards and supplies.