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| DIY power supply |
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| MarkF:
--- Quote from: Wolfgang on September 01, 2018, 05:16:43 pm ---... why not just add a pass transistor and keep the LM317 cool ? Its not one of the xtra stable or noise free regulators on earth anyway ? And if you want to be really nice you can add a current limit plus an overtemp protection plus a crowbar at the output to avoid surprises ... --- End quote --- You still have to dissipate all that power if you want a variable supply (say 32VDC input and 0-20V @ 1A output). The power will have to go to the regulator or the bypass transistor. I proposed the preregulator to split the load (granted not evenly to get a 20V output). I thought it the easier approach. LET'S SEE A CIRCUIT FOR ALL YOU PROPOSE. |
| MarkF:
--- Quote from: Pirateguy on September 01, 2018, 04:58:06 pm ---well i'm pretty sure i can pick up an ATX from a thrift store around here if need be. in fact i saw one the last time i was there. i ordered the dps3012 for my variable supply, along with a case for it. so now i just want to make the fixed output one. for that i intend to use the large heatsink from my disassembled AT, continue using the AT housing (it's all i got atm) and for the time i do stick to 3.3v, 5v and 12v outputs. leaving the negative unconnected for now. --- End quote --- That was your original approach and from what you've said and your knowledge at this point, that is probably you best course. Don't discount the negative voltage. Especially since it's available. If you end up doing any analog projects you will probably need it. |
| Wolfgang:
Well, I would say that a pass transistor is about as easy as another LM317. The advantage of a pass transistor is that it could be user with a much higher dissipation than even two LM317s. A proper cooler and a fan could easily do 100W, a TO220 LM317 can only do roundabout 25W. On top of that, a regulator that does not run hot is definitely more stable. |
| Pirateguy:
quick note: i just got some lm338 regulators. negative voltage is available? do you mean to say i should go with an ATX? |
| JS:
There's no negative version of LM338, if you need dual supplies using it you need them floating and then connect them in series at the output. JS |
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