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FrozenGate by Avery

Lm317 driver still best cheap option?

Rifter

Rifter

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Is the Lm317 still the best choice for a cheap diy driver or do we have better ic now I should be looking at?
 





Pi R Squared said:
If you don't need more than 1.5A then yes its the one.

Alan
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I would say less than 1 amp, I've used them in the past they get very hot running near max power, but yes I was talking sub 1 amp power levels, thanks!
 
Pretty much the cheapest thing out there. Just a voltage regulator and a couple of resistors.
 
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If you're talking less than 1A, definitely the cheapest... but you can safely get 1.5A from an LM317 if you cool it properly. If you wanted more than 1.5A you can use an LM338 which can put out 5A (costs less than $2.00 USD usually). Very cost effective :yh:
 
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There's also always the LM1117 for low power options, which is more efficient than the LM317, and then there are the LM1083-LM1085 for higher power, more efficient options. Be these are slightly more expensive.
 
Wolfman29 said:
There's also always the LM1117 for low power options, which is more efficient than the LM317, and then there are the LM1083-LM1085 for higher power, more efficient options. Be these are slightly more expensive.
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Thanks for the info! +rep
 
Whats a good size(uf, volt rating) for a cap to wire across the diode for protection? is a 1-10uf 20-50V enough?
 
4.7uF or 10uF, whatever is handy really. Anything above 6.3V should be fine, unless your diode has a really high forward voltage.

Remember to short the cap (when unpowered) before hooking up the diode.
 
Wolfman29 said:
There's also always the LM1117 for low power options, which is more efficient than the LM317, and then there are the LM1083-LM1085 for higher power, more efficient options. Be these are slightly more expensive.
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This ^

There is absolutely no reason to ever use a 317, 338, or 1117.

A 1084 is like 50 cents. I don't know how much 317s are, but even if they cost zero dollars, that's only a difference of 50 cents ;)
 
rhd said:
This ^

There is absolutely no reason to ever use a 317, 338, or 1117.
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What if they're already in the parts bin and you're fresh out of 1084s? What if you only need 50mA? What if your supply voltage is fixed at 12V? There are still reasons to still use a lm317 or lm1117.

Besides, LDOs are only "more efficient" if you have good control over your input voltage. Otherwise they are exactly as efficient as a standard 317.
 
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rhd said:
This ^

There is absolutely no reason to ever use a 317, 338, or 1117.

A 1084 is like 50 cents. I don't know how much 317s are, but even if they cost zero dollars, that's only a difference of 50 cents ;)
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Thanks man, I'll check out the data sheet. This will be will be for driving a 405nm 1 Watt lab setup for anyone wondering. I want to burn things and decided to start with this and see what I can do with it.
 
Cyparagon said:
What if they're already in the parts bin and you're fresh out of 1084s?
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The OP asked about new ICs, so I presume he is considering the purchase of... new ICs ;)

Cyparagon said:
What if you only need 50mA? What if your supply voltage is fixed at 12V? There are still reasons to still use a lm317 or lm1117.
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At best, these are scenarios in which a 317/1117 could be "no worse than" a 108X.

Cyparagon said:
Besides, LDOs are only "more efficient" if you have good control over your input voltage. Otherwise they are exactly as efficient as a standard 317.
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That's not true.

You could have "poor control" over your input voltage because your input is two series lithium ions that fluctuate from 8.4V to 6.0V as they discharge and as they change temperature. Despite having "poor control" over your input voltage, a 108X will still be more efficient than a 317/1117 at supplying constant current to a load that drops 5.5V.
 
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