Transistor Museum Oral History Ralph Greenburg "Peltier Gives Hogan the Cold Shoulder" Page 2

EARLY TRANSISTOR HISTORY AT MOTOROLA

“PELTIER GIVES HOGAN THE COLD SHOULDER”

by Ralph Greenburg

The lack of plumbing caused a couple of problems-- no water pipe to ground the Screen Room and no drinking fountain. Grounding was accomplished with a couple of copper rods driven into the ground and drinking water was provided by a bottled water Cooler. The Cooler contained a refrigerated compartment with two small ice trays, which are critical to this story.

Now for some historical background. A French watchmaker discovered thermoelectric cooling back in the 19th century. Thermoelectric cooling is accomplished using dissimilar semiconductor materials. The watchmaker was named Peltier and to this day this type of cooling is called the Peltier Effect. When the materials are sandwiched together and a D.C. current is passed through them, heat transfer is enabled with one side of the sandwich heating and the other side cooling. What this French watchmaker was doing messing around with stuff better left to Bell Labs, I don’t know. Perhaps he was trying to invent a digital watch or maybe he wanted to simultaneously heat his Brandy along with cooling his white wine. Which is what Westinghouse Corp. did around 1960 when they made Peltier Effect assemblies and used them in a buffet tray which had both a cool surface and a warm surface.

One of the duties of Application Engineering was to purchase and evaluate devices made by competitors. One day we obtained a Peltier Effect assembly from Westinghouse. The device consisted of a bunch of Bismuth Telluride N/P diodes clamped between two aluminum plates. We set up a demonstration by attaching a Heat Sink to the hot side and a container of water on the cold side. We could then track temperature change against the level of D.C. current.

The cooling was quite pronounced and undoubtedly Dr. Hogan would like to look at this evaluation. Hogan arrived and was very impressed with the Peltier Effect. Leo Lehner, the Application manager, decided to add a little something extra to the demonstration and placed one of the ice cube trays full of water on the assembly and told Dr. Hogan there were some R.F. experiments he would like to show him in the Screen Room and then they would come back and check the water temperature. They returned in about 15 minutes and were amazed to see that the water had frozen to solid ice. Dr. Hogan said, “I’ll be G__ Damned, I’ll be G__ Damned”. Then he paused and said, “You dirty so and so’s” and began to laugh. You see as soon as Hogan went into the Screen Room the tray of water was switched with one with ice cubes from the tiny refrigerated compartment in the water Cooler. Well we fooled him for about 30 seconds. Motorola never developed Peltier devices despite the glowing evaluation report that was submitted to management. One would have thought that a device, which, with a little help, could freeze water instantly, would have been a best seller.

To learn more about the Peltier Effect go to www.thermoelectric.com and www.electracool.com.

A Transistor Museum™ History of Transistors Publication

PAGE 2