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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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14th Jan 2021, 3:37 pm | #1 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,737
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Lm317 and similar regs
Question , has anyone had this type of reg fail giving full output ,or are they fail safe, as I have built quite a few power supplies using this reg . Mick.
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14th Jan 2021, 3:40 pm | #2 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,731
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Re: Lm317 and similar regs
I have used these a lot over the years. Had a couple fail short circuit to ground, but never to output.
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14th Jan 2021, 3:43 pm | #3 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,737
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Re: Lm317 and similar regs
Ah that's good to hear, so a fuse on the input would be a good idea, Mick.
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14th Jan 2021, 4:47 pm | #4 | |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
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Re: Lm317 and similar regs
Quote:
If the thing failed short from output to reference, the rest of the IC would pull the output really high, to re-establish the internal reference level. And that wouldn't do our load any good... |
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14th Jan 2021, 4:54 pm | #5 |
Hexode
Join Date: Jan 2018
Location: Portsmouth, Hampshire, UK.
Posts: 421
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Re: Lm317 and similar regs
Similar regulator but more current capability (with suitable heatsink) is the LT1085CT (3A), LT1084CT (5A) & LT1083CT (7.5A).
We use these a lot where I work for providing local power supplies in our ROV's. Hardly ever get a failure, very rugged devices.
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14th Jan 2021, 7:10 pm | #6 | ||
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,737
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Re: Lm317 and similar regs
Quote:
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14th Jan 2021, 7:18 pm | #7 | ||
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,731
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Re: Lm317 and similar regs
Quote:
I think I would use a fusible resistor on the input for safety. |
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14th Jan 2021, 7:49 pm | #8 |
Nonode
Join Date: Jan 2009
Location: Bristol, UK.
Posts: 2,059
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Re: Lm317 and similar regs
I've seen them fail short circuit.
Certainly not indestructible on thermal overload, especially if you forget the bolt that holds them onto the heatsink! dc |
15th Jan 2021, 7:35 am | #9 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,637
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Re: Lm317 and similar regs
If your powering valves a 317 can do odd stuff like going into protection due to the high current surge. A crowbar circuit would be better than a zener for protection.
Andy.
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15th Jan 2021, 10:05 am | #10 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,737
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Re: Lm317 and similar regs
Just to clarify there is a fuse before the zener 5.1 volt 1 watt. it's only running a 250ma max .it is working fine , Mick.
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