Re: [DIYbio] electrophoresis supply + gel cartridge + illuminator project?

6:56 PM |



On Friday, April 6, 2012 12:00:06 AM UTC-7, Cathal wrote:

A friend of mine simply uses rectified wall outlet voltage. He doesn't even bother with a capacitor to smooth it, so it's really variable. Apparently it works fine..


Rectifying the wall AC works fine, until you kill yourself.  That's about as safe as using a hairdryer while sitting next to a full bathtub -- think about it.  The wall outlet can source 30 amps before some breaker trips.  Quite enough to turn organs into cooked hot dogs.  Sure, your friend might say that all wires are protected, has fuses, etc, etc, it's still not a great idea without a real current limiting circuit internal to the equip.  Perhaps he's using a big isolation transformer, that might be OK depending on placement of fuses in the circuit, but the supply is likely pretty large & heavy compared to a solid state version.

So: Don't do electrophoresis with wall AC directly.

There are several papers which study the effect of ripple on electrophoresis, they all reach the same conclusion:  ripple doesn't matter (it just slows down the run, slightly, to the same as that of the equivalent voltage).

As for comparing wall AC to CCFL HVPS output, the voltage of the wall is 220V max (in EU), whereas CCFL HVPS may be much higher (depends on the supply), I got a couple in 400-600V range (depends on load).


## Jonathan Cline
## jcline@ieee.org
## Mobile: +1-805-617-0223
########################


 

Jonathan Cline <jncline@gmail.com> wrote:

>
>
>On Thursday, March 22, 2012 7:01:28 AM UTC-7, Nathan McCorkle wrote:
>>
>> At $10/gel the pre-cast option still sucks.
>> http://products.invitrogen.com/ivgn/product/G521801
>>
>> I really just want a solid HV power supply... Voltage and current
>> control with banana plugs.
>>
>
>At those dimensions, I believe a high voltage power supply designed for
>a
>CCFL laptop backlight would do.  (For previous generation of laptops,
>anyway.)   They are cheap from second sources, $20-$40 range.  Make
>sure to
>get one with clear pinouts though.
>
>Most high voltage power supplies designed for scientific use are low
>ripple, designed to be stable for traditional lab use.   However DNA
>doesn't care if the voltage is rippling +/- 10%, the gel runs fine
>anyway.
>
>
>## Jonathan Cline
>## jcline@ieee.org
>## Mobile: +1-805-617-0223
>########################
>
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