Discussion in 'Electronics Homework Help' started by ms.meow, Oct 15, 2012.

1. ms.meow

2
0
Oct 15, 2012
So my groupies and I made this schematic diagram from scratch which is supposed to be a voltage regulated power supply with output voltages of 0-50V with increment of 10v..

We have done the prototype but is not accepting load..
in other words, not really making an application work..

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Last edited: Oct 15, 2012
2. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,852
Jan 21, 2010
Perhaps you can show us a schematic.

What troubleshooting have you tried?

What exactly do you mean by "not accepting load"? Does the voltage drop? Does a fuse blow? Does smoke come out?

3. ms.meow

2
0
Oct 15, 2012
We haven't done anything else yet since we're afraid some components might blow if we try to put a transistor in the schem as what our other classmates suggested..

What I actually mean is when we try to connect an application. say an exhaust fan from a cooling pad.. it does not work..

4. Laplace

1,252
185
Apr 4, 2010
Can you explain what is the purpose of R1 and R6? I can see that you have made a power supply with an internal resistance of at least 20K ohms. Just how much current were you expecting the load to draw through the 20K?

5. CocaCola

3,635
5
Apr 7, 2012
That's... Umm... Quite an interesting design there...

Why are you not adjusting the output of the LM317 'internally' as described in the datasheet? Do that and you can skip all the 'toaster' elements you are directing the LM317 output towards in some attempt to alter the final output...

Look at the LM317 data sheet and focus on R4 and R5 in your circuit, scrap everything else on the output...

Last edited: Oct 15, 2012
6. davennModerator

13,991
2,018
Sep 5, 2009
get rid of R1,2,3,6 and 7 to 23

then as cocacola said go look at the LM317 datasheet

Dave

7. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,852
Jan 21, 2010
Also, read up on the maximum voltage rating for the LM317.

And R1, R2, R3, and R6 need to be removed, and R4 and R5 are at least an order of magnitude too large.

8. CocaCola

3,635
5
Apr 7, 2012
Hopefully reading the datasheet will drive that home as a 'common' (aka use this) value for what would be R5 in this circuit is generally given in the datasheet up front...

Although the question of if the datasheet was even consulted at all during this circuit design thus far...