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

Ok, I've actually looked at the original article.
Don't ever build anything this way. The comment "You can step this
down using a voltage divider in the output of your circuit" is just
stupid, you can't, sorry, Europe. But add a switch and a fuse, build
it a lot less flimsy, put it in a plastic case, and it's not all that
much unsafer then a commercial power supply.

On Fri, Jul 5, 2013 at 2:10 AM, Alexey Zaytsev <alexey.zaytsev@gmail.com> wrote:
> Guys, sorry to intervene, but just 2 cents from someone who's studies
> at a university that's got "Electrotechnical" in its name.
>
> This whole discussion reminds me of the argument from the anti-GMO
> crowd. They take the theoretical worst case scenario and run it as
> something that's sure to happen.
> Just don't grab the damn wires. Isolating the output from the input is
> a good idea and allows you to grab individual wires while being
> grounded, but it's not a hard requirement. You should just know that
> the device you've built is not fool-proof, and handle it with care.
> And while it's not absolutely impossible, you are very, very unlikely
> to die even from 380v ac, let alone 100-something volts dc.
>
> Btw, the current limiting resistor is a terrible idea. From a quick
> google search, it seems that the electrophoresis requires currents in
> the range of tens of milliamps, hundreds for bigger gels. So it's just
> not going to work. Even if we assume that it would require, say, 5ma,
> and you limit the current to 10ma with a resistor, it means that 2/3
> of the voltage will drop on the resistor, and you would need a circuit
> that can output 300+ volts, which does not look like it's making it
> any safer.
>
>
> On Wed, Jul 3, 2013 at 7:58 PM, Josiah Zayner <josiah.zayner@gmail.com> wrote:
>> Using a bridge rectifier($0.30) one can basically use AC mains voltage to
>> run your gel electrophoresis. You can buy all the components for under $5.
>> I tested it out and it works great. Can run a really good looking gel in
>> around 30 minutes.
>>
>> I made a blog post here about it:
>> http://doitourselfscience.blogspot.com/2013/07/a-cheap-simple-diy-electrophoresis.html
>>
>>
>> Any questions let me know.
>>
>>
>> Josiah Zayner
>>
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