Introduction

The problem was this...at Redeeming Grace Church we are presently meeting in a public school. Each Sunday morning we bring in three large percolating coffee pots to brew regular, decaf, and hot water for the mid-service break time. Each pot draws 9 amps. Because the average 120VAC power receptacle "outlet" in the USA is protected by a 20-amp breaker, three coffee pots would total 27 amps and blow the breaker. Thus, I carried several long extension cords with me to church every Sunday to reach separate 20-amp outlets.

In our scenario, we fill the "regular" coffee pot with water, but the "decaf" and "hot water" pots are only half-filled. Thus, I decided that it might be acceptable to connect the full pot directly to 120VAC, and to connect the two half-full pots to 120VAC on an alternating basis. That is, one of those two pots would boil for three minutes after which the power would be transferred to the other pot. That would allow us to run all three pots on one 20-amp circut: one pot full time, and only one of the other two pots at any one time.

Click on photo to display full size version.

After trying it, I observed that the alternating power doesn't seem to affect the "decaf" percolating process or taste. The full pot comes to a boil before the two half-pots. This unit allows us to run all three coffee pots on one 20-amp outlet, and I no longer have to bring several long extension cords to church every Sunday morning!

Features

This program is simply simple. It'a relay that alternates power between two coffee pots on a three-minute interval. You could probably accomplish the same thing with an LM555 timer chip set for a very slow oscillation.

Operation

• Plug the unit into a 20-amp outlet.
• Plug the coffee pots into the unit.

Technical Reference

HARDWARE

• Why did I use the MCP130315DI voltage supervisor when the 16F628 also has brownout detect? I don't know...perhaps I just wanted to be absolutely sure the '628 would come up in a known state. I'm sure the internal brownout detect would have worked just as well.

SOFTWARE

• This is really bare-bones code.
• No attempt is made to be accurate about timing.
• Why did I select a three-minute period? It was just a guess and seems to work fine.

CORRECTIONS OR UPDATES

• v1.0 - first release