How to create a delayed clock pulse, then return to regular clock cycles

Question

I am attempting to configure an LCD with just IC chips and I've been having problems. I've worked out that the main problem I am having is in the initialization of the lcd. It needs a goodly amount of time to initialise, and then in needs a couple of more configuration instructions.

I would like to give the lcd time to initialise at startup, and then change to a regular clock pulse after 3 delays. So rather than the regular clock pulse (shown in red) 3 long pulses, then back to the regular 555 spacing (shown in blue).

Is there anyway to do this using a combination of IC chips? The delay on the bottom of the clock cycle could be the same long delay, the off time isn't really relevant.

Answer 1

The blue trace is one output pulse every 2.5 input pulses, not one every three. This would take a lot of gating to decode.

For 1-out-of-3, consider the CD4017 Johnson counter. If you OR gate or diode-OR together outputs 1, 4, and 7, that is the blue trace. Output 8 inhibits counting and addresses a mux that switches from the output of the OR gate to the red signal (the 4017 clock input). Not elegant, but functional.

Answer 2

You can use a sequencial timer like in 9.2.4 of ne555 datasheet (Texas instruments) to control two MOSFET (like 2n7000) who switch between two circuit R es Capa and Diodes as input of your ne555 Clock. Or just change the voltage of the Ctrl (ie: 8/10 of VCC) pin of your clock to increase the duty cycle and lower the frequency.