Adios
Hossimo asked for a circuit 3 months ago. Mitchekj at least posted a usful link, but where were the rest of you? No circuit in sight, and no wonder the poor guy never posted again. You lost a member there, and now two.
I remember when I first got interested in electronics back in the mid eighties. One of the first 'projects' I built used a 555 timer, a coutesy light delay for my old Ford Zephyr. I knew nothing of leakage currents or voltage spikes back then, but with the help of Walter Jungs's excellent 'IC timer Cookbook' I was able to put together a simple circuit to do the job. It was a library book, but I seem to still have it(!) and still refer to it on occasion. Anyway I digress, the point is that circuit was very similar to the one here, and though the delay was only 3 minutes, it used a old (scavenged) aluminium electrolytic timing capacitor, and no regulator or over voltage protection. That little circuit continued to function flawlessly until I sold the car a few years later.
Now having finally come out from hiding, you guys raise some valid and some not so valid points above, but at the same time you're missing the point. It's not a timebase for some precision instrument, it's to turn a fan on and off! But I have no wish to argue these points because this is not about electronics, it's about attitude. Read Steves original response again, can you really not see my point?
I am not being defensive, neither am I offended, and if you want to run that kind of forum where everyone is spoiling for an argument, then good luck to you, many people enjoy that, and there's nothing wrong with it, but really it's not for me.
I wish you all well.