John Waters wrote:

> Hi All,
>
> I saw a kind of 12v dc to 110v ac inverters selling in electrical 
> stores that allow people to drive their laptops in a car. I want to 
> use it to drive a small device that uses 110v and consumes power less 
> than 3 Watts. But instead of using the car battery, I want to use 8 
> pieces of D cells as the dc source. The reason is, the 110v ac 
> generated this way would be very safe even when someone accidentally 
> touches it? It is hard to imagine 8 D cells could kill someone, right? 
> Could anybody give some comments to my argument?
>
> Thanks in advance!
>
> John
>
>
The very first item I designed as a young engineer was a custom 
detonator for oil exploration (sesmic) explosions in the Guatemalan 
jungle. It converted 6 D cells (9V) to 110V DC in order to set off 
downhole explosions using  a transistor-driven oscillator, a 
transformer, an SCR , a heavy cap, and an early optoisolator. While 
blasting caps are "guaranteed"  to explode at 6V, we wired two in 
parallel and applied 110 VDC because we'd had failures at 12V (normal 
blasting voltages) due to heavy moisture.

Even though we used a charge bleeder (a heavy resistor to bleed off the 
charge) , the 110VDC was easily capable of killing anyone touching it.

--Bob


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