Problems with the LM317T regulator

[audioguru]

You will be very sorry when you program a microcontroller or use a bunch of other Cmos ICs then destroy them when your LM317 with LM117 resistor values cause their supply voltage to rise too high.
What good is a regulator that does not regulate?
Every single circuit in the datasheet for the LM117/LM317 shows 240 ohms for R1 and a more expensive LM117. The notes in the datasheet talks about the value for R1.

 

[MikeMl]

So lets see what happens to the output of the 317 as a function of R1 and the load current.

I make R2 = 3*R1 so as to try to make the 317 put out a nominal 5V.

There are two traces, the Red one is the voltage out with a 100mA load, and the Blue one is with no (1GigaΩ) load, both plotted as a function of R1. Note that for values of R1 above 1.2K, the voltage rises if the load is switched off.

So Scrooge, for values of R1 around 200Ω, do you really think it matters if R1 = 200Ω, 220Ω, or 240Ω??? Especially, if R2 is a pot that you are going to tweak to get the exact voltage you want out.

 

[KeepItSimpleStupid]

I do believe D2 is in the wrong place. I believe, it should be across the output.

The regulator will get hot if high currents are drawn with Vadj shorted. e.g. regulator set at 1.2V.

 

[SODA]

There is no 220 ohm resistor, it is wrong at 240 ohms.
If R1 is 220 ohms then it dissipates only 0.007W so a tiny 0.1W resistor is fine and a big 1/2W resistor is not needed.

The only reason for me talking about a 220R resistor is because it's the closest to a 240R . Unless you can tell me where you can get hold of a 240R resistor.
On the other hand , i wasn't aware of the LM117, so i'm going to check this out on the data sheet . So, thanks of putting me on the track about the LM117

 

[SODA]

I do believe D2 is in the wrong place. I believe, it should be across the output.

The regulator will get hot if high currents are drawn with Vadj shorted. e.g. regulator set at 1.2V.

Here is the data sheet for you to look at**broken link removed**

 

[audioguru]

I do believe D2 is in the wrong place. I believe, it should be across the output.

No.
Look at the datasheet for the LM317. It shows the two protection diodes.

The regulator will get hot if high currents are drawn with Vadj shorted. e.g. regulator set at 1.2V.

No.
With the ADJ pin connected to ground then the output voltage is +1.25V and the output current is drawn by the load, not by the regulator.
The regulator heats normally by the output current times the input-output voltage.

 

[audioguru]

The only reason for me talking about a 220R resistor is because it's the closest to a 240R . Unless you can tell me where you can get hold of a 240R resistor.

A 240 ohm resistor is a normal 5% value. Are you using old 10% or 20% resistor values?

 

[janagyjr]

Tayda Electronics has a great selection of resistors, IIRC they have 240Ω resistors for sale.

 

[SODA]

A 240 ohm resistor is a normal 5% value. Are you using old 10% or 20% resistor values?

I was waiting for your reply, uncle Scrooge. I realize my mistake this afternoon when i bought some new stuff. So sorry for that