Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Laser Pointer Store

Am I crazy or...

Joined
Jan 20, 2008
Messages
1,734
Likes
48
Points
0
I was scrounging around my junk bin looking for some kind of regulator I could use to build some sort of driver... most of the regulators I've found are for regulating 36v down to 18v or similar... anyways I found a tiny SO-223 package LVDO regulator called a APL1117 I was figuring maybe I could use...

So I look up a datasheet and find this example circuit... I'm about 90% of the way through building it when I realize, if I'm not mistaken, that V[sub]in[/sub] shorts directly to GND (through an optional filter capacitor C1)... Am I crazy or will this not work?
 

Attachments


Joined
Jan 20, 2008
Messages
1,734
Likes
48
Points
0
yeah so I finished it and sure enough it has only TWO wires coming off it... V[sub]in[/sub]/GND and V[sub]out[/sub]..

I'm not sure how this is supposed to work... invisible diodes? sorcery?
 

Attachments

chido

New member
Joined
Dec 4, 2007
Messages
1,918
Likes
0
Points
0
I'm just as confused as you are????? :-?

EDIT: Could you post a link to the datasheet?
 

woop

New member
Joined
Nov 9, 2007
Messages
342
Likes
1
Points
0
WHAT?
um whats the problem?
it looks pretty standard to me
the input capacitor is to smooth any ripples from the power supply, it only conducts when there is a change in voltage, for DC, it will not short the input
 
Joined
Jan 20, 2008
Messages
1,734
Likes
48
Points
0
woop said:
WHAT?
um whats the problem?
it looks pretty standard to me
the input capacitor is to smooth any ripples from the power supply, it only conducts when there is a change in voltage, for DC, it will not short the input
right, but it says the capacitor is optional... if you remove the capacitor it soon becomes clear you're simply connecting the + wire to the - wire before it gets to the regulator. In electronics this is called a short circuit, which rarely produces anything but smoke.
 

woop

New member
Joined
Nov 9, 2007
Messages
342
Likes
1
Points
0
sorry but i don't see the short.
if you remove the capacitor, you would remove the wires to the cap as well, not just short them together
 
Joined
Jan 20, 2008
Messages
1,734
Likes
48
Points
0
woop said:
sorry but i don't see the short.
if you remove the capacitor, you would remove the wires to the cap as well, not just short them together
Hmm... you're probably right...

I really do need to stop building circuits when I'm hungover... thanks for putting it in perspective.
 

woop

New member
Joined
Nov 9, 2007
Messages
342
Likes
1
Points
0
thats ok. everyone has mental blanks every now and then. especially after a big night ;D
 

chido

New member
Joined
Dec 4, 2007
Messages
1,918
Likes
0
Points
0
woop said:
sorry but i don't see the short.
if you remove the capacitor, you would remove the wires to the cap as well, not just short them together
I see what you mean, I can't believe I didn't notice that either.
 
Joined
Jan 20, 2008
Messages
1,734
Likes
48
Points
0
Ohhhkay.. So I removed the short and put it together... sure enough it works now...

here it is regulating 12v down to 1.2v... fully adjustable, though I think I need a different pot.. this one's 10k so the adjustment is pretty touchy.

Anyways, thanks guys... remember, never underestimate the power or prevalence of human error.
 

Attachments





Top