Electronic control of 2000W 240V AC heater

On a sunny day (Thu, 30 Jul 2009 01:46:51 -0700 (PDT)) it happened Mike wrote in :

Variable? Chewing gum in switch?

If turning a knob instead of pushing a button is ok, you can buy the device needed.

30 minutes is a long time to make with a 555. The CD4060 is better for making times that long. You could use a power MOSFET to turn on a relay.

Actually, I was thinking of an ice cube behind a spring loaded switch level near the heater!

On a sunny day (Thu, 30 Jul 2009 11:26:03 -0400) it happened Jamie wrote in :

I'v heard US WW2 detonators used a piece of plastic with acetone. Took a while to dissolve the plastic.

Circuit no, but I use a bathroom fan timer which you could use to switch a relay.

Intermatic # EI200W

greg

WW-II ? Plastic? Acetone? Such an expensive and valuable materials couldn't be wasted. They used a piece of tar loaded by the spring.

A piece of sugar inside a safety switch was the standard solution for the delayed activation of the underwater mines. Salt is less suitable for that purpose.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

On a sunny day (Thu, 30 Jul 2009 10:49:41 -0500) it happened Vladimir Vassilevsky wrote in :

scroll down for acetone time delay fuses.

Mechanical twist timer. Cheap, reliable, great human interface.

We use the half-hour versions on our Metcal soldering irons for auto-shutoff.

John

Coffee timer?

The knob and switch from a very old microwave oven?

Good Luck! Rich

Hey, I resemble that remark! No, not the old part. I have three microwave ovens, all three have knob timers on them. Just checked the old one was manufactured in 1983, 26 yrs ago. Works fine, (Frigidaire). Mike

Until a couple years ago the cheapest microwave at Walmart had the simple twist timer. Now they are all digital. Too bad. I much prefer the twist timer. Also people who avoid idle power loads. My microwave uses zero power when off.

A CMOS 555 can go to 30 minutes with a low leakage cap.