Re: [DIYbio] Current and voltage reqs for electrophoresis power supply

Actually, I believe that depends on the gel. In a vertical gel, resistance can increase over time, as the more conductive ions get electrophoresed out of the gel. But in a horizontal gel, the gel resistance typically *drops* as it heats up. So if you run at constant voltage, when the gel heats up, the current will increase, creating more heating, etc. - a thermal runaway effect!

To be safe, you can run at constant wattage, which should guarantee constant heating.

On Sunday, December 9, 2012 2:09:12 PM UTC-8, Nathan McCorkle wrote:

From what I've read constant current means constant migration speed, but as electrolysis occurs the resistance goes up and more heat is generated. Constant voltage means as resistance goes up due to electrolysis, current goes down and so does migration speed, but heat stays low.

On Dec 9, 2012 11:51 AM, "Jeswin" <phill...@gmail.com> wrote:

On Sat, Dec 8, 2012 at 9:47 PM, Nathan McCorkle <nmz...@gmail.com> wrote:
> On Sat, Dec 8, 2012 at 5:27 PM, Jeswin <phill...@gmail.com> wrote:
>>
>> I run at fixed current, 75V for 20-25 minutes (fresh, and larger gels)
>> and 50V for 35-45 minutes(older gels that were stored in 4C before
>> using).
>
>
> you mention fixed current, but then quote voltage specs. That would mean you
> control for gel resistance everytime you make a gel.
>
Ack. I meant voltage fixed at 75 or 50 and let the current vary. My
gelbox is a simple affair. It's lets you choose 6 or 7 different
voltages to run at and lets you program the timer.

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