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Tools Calculators.

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ericgibbs

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hi,
The following links are to Calculators recently added to the Tools Section.

The calculators are mainly to show the function of the devices to students and show the effect of changing the component values.

I would appreciate any 'positive' feed back on the operation of the tools, also any suggestions for new tools.

Eric

https://www.electro-tech-online.com/tools/LM317V2.php





https://www.electro-tech-online.com/tools/IC555VM1.php

https://www.electro-tech-online.com/tools/LM3914V3.php

https://www.electro-tech-online.com/tools/LM3915V4.php
 
In the LM3914 and LM3915 calcs, what is the 6th box (to the right of 'Watts') displaying?
 
In the LM3914 and LM3915 calcs, what is the 6th box (to the right of 'Watts') displaying?

hi alec,
Thats a redundant debug box used in development, I will remove it, thanks...;)
E.

Removed.
 
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The LM317 ckt shows 220Ω for setting Iadj current to 1.2/220 or ~ 5.5ma. That's cool for an LM117 but the 317 needs 10ma. so R = 1.2/.01 = 120Ω

Other'n that, you made a great site even greater:D
 
The LM317 ckt shows 220Ω for setting Iadj current to 1.2/220 or ~ 5.5ma. That's cool for an LM117 but the 317 needs 10ma. so R = 1.2/.01 = 120Ω

Other'n that, you made a great site even greater:D

hi,
The LM117/317 datasheet recommends a 240R, I chose a 220R as its more readily available.

If required I could offer the user the choice of 120 or 240R.??

Thanks for the response.:)
E
 
hi,
Agreed with 'audioguru' that R1 resistor should be a 120R, rather than a 220R, would be a safer value, just in case the user was powering CMOS circuits with a too low current demand on the LM317 which could result in over voltage output from the LM317.

Value changed.
E.
 
hi,
Agreed with 'audioguru' that R1 resistor should be a 120R, rather than a 220R, would be a safer value, just in case the user was powering CMOS circuits with a too low current demand on the LM317 which could result in over voltage output from the LM317.

Value changed.
E.

Audioguru? Was that not JaguarJoe?

It's a nice list, I have no doubt it will come in very handy at some point.

Cheers,
Matt
 
Audioguru? Was that not JaguarJoe?

It's a nice list, I have no doubt it will come in very handy at some point.

Cheers,
Matt

hi D8,
No, it was based on PM's with 'agu'.;)

It will work OK with a 240R, but if the LM317 is lightly loaded it may under certain conditions allow the regulated output to rise.

The d/s for the LM117/317 clearly states 240R.

Personally I wouldn't use an LM317 for a circuit requiring less than 10mA

E.
 
hi D8,
No, it was based on PM's with 'agu'.;)

It will work OK with a 240R, but if the LM317 is lightly loaded it may under certain conditions allow the regulated output to rise.

The d/s for the LM117/317 clearly states 240R.

Personally I wouldn't use an LM317 for a circuit requiring less than 10mA

E.

Ah, that makes sense. Sorry for the sidetrack.

Cheers
 
Sigh,

Looking at the original National Semi data sheet for for the LMx17, page 2 gives the specs for the LM117 ONLY. It specifies (clearly) 5ma min load or ~240Ω.

Looking at the same data sheet, page 3 gives the specs for the LM317/LM317A. This time it sez 10ma min load which will be ~120Ω.
 
It's brand dependent, some datasheets show 120 ohms some 240 ohms. Most modern spec LM317 have better performing internals than the 40 year old design original NS parts which required 10mA minimum.

On a challenge from anohter forum I tested real parts and showed two different brands of modern LM317 would regulate fine even at a current of 1.25mA. (and could be used as a constant current LED driver at 1.25mA regulated).

However that does not mean they would regulate correctly for all possible currents/voltages/temperatures.

Personally I think modern LM317 are much closer to that 5mA minimum than the traditional 10mA minimum, and newer datasheets usually have the 5mA value. I've seen in commercial devices using a 220 ohm resistor too with a LM317. As for the calculator, maybe you could give an option?
 
Sigh,

Looking at the original National Semi data sheet for for the LMx17, page 2 gives the specs for the LM117 ONLY. It specifies (clearly) 5ma min load or ~240Ω.

Looking at the same data sheet, page 3 gives the specs for the LM317/LM317A. This time it sez 10ma min load which will be ~120Ω.

hi Jaguarjoe,

We have agreed that 120R is a more practical value and should cover all the LMxxx types.

Again, thanks for your input.:)

hi Roman
As for the calculator, maybe you could give an option?

Its possible to offer the user a choice, 120R 220 or 240R.
Anyone else got any opinions on those values.?

Eric
 
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hi Roman.
Added the option for user to choose, 120R 220 or 240R., default is 120R.

E
 
Hello

I have found 180R to be a great companion for the 317. And, it's standard too. Just seems to work so well with this legend of a Regulator. The best of all worlds. Stability being the most important though.

No worries from Manufacturer to Manufacturer.

A friend of mine knows stuff. He said I should check ETO out. Because they never guess.

That's all I can say...

Jacky
 
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Hello there Eric,


Interesting calculators there.

One thing i found was with the LM317 calculator. It allows a power dissipation of 2 watts without a heat sink. That's OK for the TO-3 package but not OK for the TO-220 really. A better limit for the TO-220 is 1 watt. That's because the TO-3 package has a thermal resistance of about 35 deg C per watt, while the TO-220 package is about twice that, even a little more like 80 deg C per watt. A temperature rise of 80 degrees C is quite a bit for a device even though it might be able to take it because considering ambient that means the package will be at the same temperature as the boiling point of water and that's with only 1 watt, so imagine what 2 watts would do :)

Also, a minor point, it's a little unclear that the power dissipation being shown is for the load resistance or for the package itself.
 
hi Al,
Changes made in line with your observations.;)

E.
 
Hello there Eric,


Interesting calculators there.

One thing i found was with the LM317 calculator. It allows a power dissipation of 2 watts without a heat sink. That's OK for the TO-3 package but not OK for the TO-220 really. A better limit for the TO-220 is 1 watt. That's because the TO-3 package has a thermal resistance of about 35 deg C per watt, while the TO-220 package is about twice that, even a little more like 80 deg C per watt. A temperature rise of 80 degrees C is quite a bit for a device even though it might be able to take it because considering ambient that means the package will be at the same temperature as the boiling point of water and that's with only 1 watt, so imagine what 2 watts would do :)

Also, a minor point, it's a little unclear that the power dissipation being shown is for the load resistance or for the package itself.

Hi Mr Al

Your calculations are bang on. With around Three years of continuous testing the TO-220 317T....I can confirm all you said in your post above.

With a Maximum constant dissipation of around 0.75W in a sealed enclosure...the TO-220 317T is bulletproof. No heatsinks needed. Or required.

It runs hot yes. But never a failure from any one from various Manufacturers.

Very robust regulator as we all know. That is why it is still around after 43 years. See here for the fun of it: https://en.wikipedia.org/wiki/LM317

Invented 1970. Astounding. And still going strong 2013. Nothing beats good design.

Regards,
tvtech
 
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hi Al,
Changes made in line with your observations.;)

E.

Hi again,

Eric:
Oh that's great. But any reason why the current is now limited to 0.75 amps? Before it was 1.5 amps.

tvtech:
It's nice to know you tested these that much. I ran one hot a few years ago but never measured the case temperature. It always worked well though. I used it for simply regulating and adjusting the fan speed of a small DC fan.
Interesting article too, and they even mention Bob Pease and the LM337.
 
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