Re: [DIYbio] A simple and cheap >100V DIY electrophoresis power supply

On Fri, Jul 5, 2013 at 4:05 AM, Jonathan Cline <jcline@ieee.org> wrote:
> Current limiting is more for fire prevention than human safety in my
> suggestion. The power supply is basically boiling the buffer slowly.
> As it heats up the buffer, the resistance of the gel decreases as it
> melts, which increases the current, and so on - until the gel becomes
> solution again and resistance is so low that current overloads the
> bridge and the bridge starts to smoke. If the bridge burns into a short
> or etc, then things will get hot really fast. Then the duct tape will
> catch on fire and the case if any will melt. And so on.. This could
> all happen without the main's circuit breaker tripping (@ 15A or @
> 30A). Even GFCI would not be protection in this case.

Why would you install a 30A fuse? That's an assload of current, such
fuse is more appropriate for a small apartment.
For this application, a 0.5A fuse looks more appropriate. The
rectifier from the article is rated up to 1A, so just choose something
lower then that.

>
> ## Jonathan Cline
> ## jcline@ieee.org
> ## Mobile: +1-805-617-0223
> ########################
>
>
>
> On 7/4/13 5:36 PM, Alexey Zaytsev wrote:
>> 1) Fuses don't change anything here, they are to protect your wiring,
>> not yourself.
>> 2) Current limit makes no sense regarding safety here. The current
>> that runs through the gel is much higher than the current that would
>> ever run through a person who's grabbed the electrodes,
>
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