I am performing a science experiment where I need to generate 25 volts, 45 volts, and 65 volts. I need to attach the power source to electrodes by alligator leads into electrophoresis gel. What would be the most efficient and cost-effective way to generate these voltages.

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    \$\begingroup\$ Are there any current requirements? \$\endgroup\$ Nov 17 '16 at 20:27
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    \$\begingroup\$ Another thing to mention, for the literal love of life, is that 65 V can already be relatively dangerous (45 V, too, and 25 V, too, but for those you'd basically have to touch contacts with wet hands to likely suffer a dangerous electrocution). \$\endgroup\$ Nov 17 '16 at 20:37
  • \$\begingroup\$ a couple of batterys? \$\endgroup\$
    – dalearn
    Nov 18 '16 at 15:20

Buy power supplies. No, really. These things are produced in large quantities and sold into a competitive market. Leave the safety design and regulatory approvals to someone else. Anyone that has to ask here won't be able to design a "efficient and cost-effective" power supply compared to commercial offerings. Even if they could, it would cost way more than just buying them unless the volumes are 100k or more.

Jameco is one place to look around since they have a very wide selection of power supplies, and they target hobbyists and other non-professionals.

  • \$\begingroup\$ yep. "most cost- and power-efficient" will obviously be buying a system from someone who knows their ways around power supplies. \$\endgroup\$ Nov 17 '16 at 20:33
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    \$\begingroup\$ I think, however, this answer would benefit from noting that to buy something that is optimal in one or two dimensions (in this case, efficiency and cost), it's necessary to exactly define the operating boundaries in the other dimensions – in this case, current sourcing capabilities, stability and noise requirements. \$\endgroup\$ Nov 17 '16 at 20:35
  • \$\begingroup\$ @MarcusMüller there's another variable in an educational setting -- the teaching benefits of doing it in house. \$\endgroup\$
    – Chris H
    Nov 18 '16 at 9:41
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    \$\begingroup\$ @ChrisH but OP specifically asked for cost- and energy-effectiveness. And that is kind of contradictional to "let's build something basic, understandable". Truth is,these days,everything around you is highly engineered with more than 100 years of experience in electrical and mechanical and structural engineering.Even in high-class universities,you'll have a hard time learning how something is actually done at a cost-efficiency that's state of the art,because these kind of questions are of little educational use,but very important to companies(so it's their R&D departments' job to solve). \$\endgroup\$ Nov 18 '16 at 9:47
  • \$\begingroup\$ Are we sure this is "allowed" for the OP? I read OP's question as implying OP needs to build something that can generate that voltage, not buy something... since it's a science fair project. Like the classic hand crank that lights a light bulb. \$\endgroup\$
    – SnakeDoc
    Nov 18 '16 at 22:35

I believe your current requirements will be modest for electrophoresis.

Consider a string of 9V batteries, which will be inexpensive ($7 at the dollar store for Panasonic batteries) and relatively safe. If you can add a 100K resistor to the taps they will be even safer, but avoid contact with the batteries.

It's possible to regulate the output of the batteries and do other fancy stuff, but if you just want roughly those voltages you can tap them all off of one string of 7 batteries (eg. 27V/45V/63V).

There is also an instructable specifically to make an electrophoresis supply that appears to be above par for the genre, and the PCB is open source so you could easily duplicate it on a similar PCB or on perf board. The voltage is regulated and is adjusted with a pot. Assembling a dozen or so parts is not exactly a Herculean task if you have wielded a soldering iron before. It's based on the MAX1771 chip (available in easy-to-use 8-pin DIP form) in a standard 'boost' configuration. You can power it with a 12V/1A wall wart adapter.

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I would feel more comfortable if you are using a power supply (such as the above suggestions) with little output current capability and with limited output voltage. I have a 400VDC 2A programmable power supply kicking around here, but interns/juniors don't use it without a lot of safety instruction and preferably not working alone.

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    \$\begingroup\$ You can use a few diodes to drop the voltage if you want to make it more exact without needing any complex regulation. \$\endgroup\$ Nov 18 '16 at 17:31
  • \$\begingroup\$ @DavidSchwartz This isn't very accurate. Even though it is generally accepted that diodes drop around 0.7V, what actually happens is that diodes have voltage drop curves. And that's why if one just puts a diode to drop the voltage, it will only actually drop if there is some load. Also, if the load varies, the drop will also vary. \$\endgroup\$ Nov 19 '16 at 18:03

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