Power Supply
I have been looking for a power supply for my electrophoresis other than batteries. I have been using an old train transformer, but it is very slow or 3 to 5 9 volt batteries, but is very costly. While searching the internet I found this:
www.science-projects.com/PowerSupply.htm
Now any time you play with a 120 volts you should be very careful. Here is a file for Basic Electrical Safety:
www.labtrain.noaa.gov/osha600/refer/menu12a.pdf
I will be building this power supply and trying it out. I will talk about this in a later post. If you build be very careful.
2 comments:
A couple serious errors in the schematic you should be aware of:
2) The plug polarity in the schematic is wrong. The black wire (hot side) should go to the narrow spade of the plug, not the wide. If you build the circuit as shown it could short and/or shock you without blowing the fuse, possibly even while turned off. (Unlikely, but possible.)
2) Please, please, please, make sure the rectifier (technically a "bridge rectifier") is rated for GREATER than 200V, not less than. Peak voltage of 120V line is actually 170V, and you need a safety factor on top of that.
I'd also recommend using a grounded electrical cord and enclosing the circuit in a metal case. Attach the green ground wire from the cord and the dimmer to the case and make sure everything else is well insulated - this will give you a little more protection should the circuit go wrong somehow.
Some of the other descriptions of electrical theory and projects on www.science-projects.com are overly simplified or incorrect. (The explanation of how the "wave cutter" dimmer works), so double check it against other sources.
Thank you. I will look into this further. If you have a schematic for a good power supply let me know and I will post it here.
Lawrence
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