Generating Pulses

Hello guys! I need your advice with a little problem that is puzzling me.

Let's suppose we have two pulse generators.

The first generator (called pulse 1) throws 3 pulses, each one have 1/2 second of duration.

Half second later, the second generator (pulse 2) throws 4 pulses, 1/2 second each one.

Both generators wait a period (15 seconds) before the cycle repeats.

The attached drawing is much easier to understand than the written explanation.

I'm not sure how to do this, because pulse 1 and pulse 2 should be somehow cascaded or synchronized between them. By that very reason my 555 IC knowledge proved to be insufficient. Even worse, I have no experience with micro-controllers.

Thank you in advance for your help!

A 4 bit binary counter driven with a clock which has a 1/2 sec period. Decoded that to 16 outputs using 1 of 16 decoder or two 1 of 8 decoders. OR together states 0, 2, 4, 6 for Pulse 1, and OR together 8, 10, 12, and 14 for Pulse 2. Use state 15 to stop the process until the next trigger starts it again.

Brilliant Mike! Thank you. I suspected that I needed some kind of counter, I will need to learn about logic gates then.

You could also use CD4017 or CD4022 cascaded Johnson counters which have the decoded decimal outputs and use the OR gates to select the desired outputs as Mike Ml suggested.

Long time no see Crutschow!

The 4017 means good news for me, I have some laying around. Will any OR gate do, or would you recommend a specific model?

How do you cascade two 4017s to get 16 sequential states? Set up the first to count to 0-7, and then the second to count 0,1?

I see your point Mike, but the 15 second lapse is just an approximation. Could be a little more or less. The circuit will be used to dial the last number on a cellphone, wait for 2 or 3 rings, and hang up the line before the voice mail machine kicks in.