Electronics > Beginners
Lm317 vs LM338
Mr. Scram:
--- Quote from: exe on August 26, 2019, 04:32:15 pm ---That's why I tend to buy a lot of stuff that I don't use in the end to save on shipping and waiting.
I used to be upset about it, now I just call it "price for education". Unless you are really short of money, I don't see $50 as a big expense. I myself can save much more just by stop buying junk food, alcohol, etc.
Anyway, I'm yet to finish a project without a need to order missing parts last minute. I just accept that I'll have to do an additional order or two. My annual budget for this hobby is $2000 (it's ok to spend less, it's the amount I allow myself without hesitation). It's big money, and people tell I'm crazy, but I think it's fine to pay so much for own education. Who said it should be for free? Last year I didn't spend much because most of the time I already have parts and equipment I need. I spend my money, but when I was a child my parents just gave pocket money so I could buy spare parts from the flea market because they thought that would facilitate development of my tech skills that would make me more competitive on the job market.
So, I suggest optimize for speed of learning and development, and not put unnecessary budget constraints that limits you. Save on beer, but not on parts.
--- End quote ---
I don’t think “just spend $2000 a year” is useful advice.
floobydust:
IF a LM317/LM338/LM350 fails short, it burns up the potentiometer.
So replacing the IC may not seem to work, the output stays at top voltage. You have to check the potentiometer with an ohmmeter that it can still dial down to zero.
A very long time ago, my lovely 10-turn pot up in smoke. So I added a tiny fuse in series with it.
exe:
--- Quote from: Mr. Scram on August 26, 2019, 05:09:20 pm ---I don’t think “just spend $2000 a year” is useful advice.
--- End quote ---
That is not what I advised. It's not about spending a specific amount. It's about not going too cheap when it doesn't make sense. I'll remove the amount as other people can also trigger on it.
Mr. Scram:
--- Quote from: exe on August 26, 2019, 05:33:12 pm ---That is not what I advised. It's not about spending a specific amount. It's about not going too cheap when it doesn't make sense. I'll remove the amount as other people can also trigger on it.
--- End quote ---
It's not about the amount or "triggering". It's about advising people to spend what could easily be an order of magnitude more on parts where the cheap alternative is not only functional but for a lot of people even the only real option. Your junk food and beer budget may well exceed the disposable income of others. Fakes are an issue but not hugely so. I'm not saying you'll get original parts but most are functionally equivalent enough as not to make a difference for learning purposes.
exe:
--- Quote from: Mr. Scram on August 26, 2019, 06:02:01 pm ---I'm not saying you'll get original parts but most are functionally equivalent enough as not to make a difference for learning purposes.
--- End quote ---
As I said before, I believe this is a wrong approach doing more harm than good. I advise buy new and original parts, esp. when it comes to jelly-bean components. Why gambling and guessing why it doesn't work? How do you know if it's "functionally equivalent" and not going to break any moment in the future? If one wants to save on delivery, buy, e.g., from lcsc.com.
You can't have original parts, fast delivery and cheap price.
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