Topic: Cheap Lpc Question (Read 202 times)

animex2 · « **Reply #31 on:** February 14, 2004, 09:30:00 AM »

the closest numbers i could find at radio shack for the numbers you want are -

220 ohm 1/4W 5% Carbon Film (240 you wanted, 20 to low)

and

330 ohm 1/4W 5% Carbon Film (400 you wanted, 70 to low)

or

470 ohm 1/4W 5% Carbon Film (400 you wanted, 70 to high)

=/

networkBoy · « **Reply #32 on:** February 14, 2004, 09:37:00 AM »

use the 220 ohm, that's fine, but buy their 5 pack of 10 resistors and place 4 in series with the 330 ohm (thus making it 370 ohm)
That will get you 3.35 volts out which should be fine.
-nB

animex2 · « **Reply #33 on:** February 14, 2004, 09:50:00 AM »

5 pack of 10 ohm resistors?

::EDIT::

if thats so, i know i have at least 4 100 Ohm resistors.... I could link them up in a series making it 400 ohms...

and this may be pushing it... but i should have at least 6 100 ohm resistors....

2x 100 == 200 ohm for R1 (40 to low... if this is too low i can just get the 220s)
4x 100 == 400 ohm for R2

animex2 · « **Reply #34 on:** February 14, 2004, 10:07:00 AM »

networkBoy · « **Reply #35 on:** February 14, 2004, 12:39:00 PM »

400 and 220 ohm would work out to 3.52 volts, which is too high.
200 ohms would be enven higher
-nB

animex2 · « **Reply #36 on:** February 14, 2004, 01:37:00 PM »

so i want 400 (4x100) and 240 on the dot... (1x 220 + 2x 10)

that would work out good, right?

::EDIT::

user posted image

Is that right?

networkBoy · « **Reply #37 on:** February 14, 2004, 09:45:00 PM »

greengiant · « **Reply #38 on:** February 15, 2004, 12:18:00 AM »

The 3.3v regulators are as common as the lm317, actually more because they are more used.

I forget who is actually building this circuit now, but your only complicating yourself.

There are variouse companies that make the voltage regulators, ZR is a common one, but there are others.
ZR - http://www.zetex.com/3.0/pdf/zr78l.pdf

Simple search on yahoo,
http://search.yahoo....n=20&fl=0&x=wrt

Reveals parts from NS, TPS LT, and MANY other companies. Digikey has some 12 to choose from for example.

Saves you the hassle of the wiring up the extra resisotrs for the Lm317, as well it saves you the trouble of finding the exact values.
With the SST you cannot provide more than the specs (you can upto 3.5 even 3.7 at low current) or else you kill the chip, if you go lower than 3.2 the chipp will give you erraditc responses.

animex2 · « **Reply #39 on:** February 15, 2004, 03:36:00 AM »

networkBoy · « **Reply #40 on:** February 15, 2004, 08:31:00 AM »

yup
-nB

animex2 · « **Reply #41 on:** February 15, 2004, 10:23:00 AM »

alright, thanks for your help NB and Green Giant and everyone else =)

Ill be building this Tuesday and hope it works, Lmao...

animex2 · « **Reply #42 on:** February 15, 2004, 10:30:00 AM »

er, one last quesiton, how do i know what is pin 1 and 3 on the LM317T? (obviously the middle is 2) should I be looking at the metal part at the top or the plastic part?

greengiant · « **Reply #43 on:** March 14, 2004, 02:43:00 AM »

Well, the very first 5 units I made I used the LM317 cause I didnt know better.
I made a diagram, long time ago, which I was trying to find for you. Found it, So here it is.

user posted image

Also, for the pins. Its standard, usually.

You will need to check the datasheet. I have encountered 2 types of LM317 where 1 has Vin GND Vout, and the other is Vout gnd Vin. When looking at the flat side.

Heres some VERY useful links for the LM317.
http://www.qsl.net/ok1duo/lm317.htm <- Schematic + Resistor value calculator for it.

http://casemods.poin...rn.org/vregtut/ - A tut on how to build a Vreg for fans, using the LM317

http://members.aol.c...aysaver/p3.html - For some playstation hacking thingy, but they use the LM317. Middle of the page has some 5 pictures of the variouse chips, and the pin outs. (Theres the LM317LZ, LM317T) LZ is the more common, lower voltage version.

Well have fun with your project.

thedustycelt · « **Reply #44 on:** April 05, 2004, 09:40:00 AM »

I was reading thtough this post because I am building the same thing, and I have a Question...
Why do we need to use the voltage regulator and capacitors?
Can't we just use a voltage divider circuit?
user posted image

two resistors, and bam! We are done. (a lot cheaper than the voltage regulator) Using a 10ohm and 20 ohm resistor would bring the 5 volts down to 3.3.
Is there a reason why this shouldn't work?

Info and calculator borrowed from:
http://hyperphysics..../voldiv.html#c1

Author Topic: Cheap Lpc Question (Read 202 times)