# Thread: Need mentor for electrical projects

1. Join Date
Nov 2003
Location
North Alabama, SW Kentucky
Posts
1,913
I've a very limited experience in electricity (I can wire a house, repair a lamp, and do continuity testing... very basic, I know). I've been post-poning some projects hoping to find someone who'll coach me in them. Nothing that would fry myself or burn a house down, I'm just trying to get some LED's to run off a car battery for example.

Waya

2. Join Date
Jan 2001
Location
New York City
Posts
3,397
You want to search Amazon and ABE books for the
various "cookbooks" written by the Blacksburg

Here's a "catalog" of sorts:
http://www.bugbookcomputermuseum.com...ok-Titles.html

The 555 Timer, Phase-Locked Loop, and OpAmp books
are classics, and contain all sorts of handy
little circuits that you can copy, adapt, and
find useful. They date from the 1970s, but
I still have my copies, and find them useful.

3. Join Date
Sep 2006
Location
Laurel, MS
Posts
1,026
I have a number of years work experience in Electronics/Electrical, as a technician. Your LED example is a very simple application.

Wire a resistor (700-750 ohm range) in series with LED. This limits current to the 15-20 mA range for a 12 Volt source. Which is what most LED's need to operate.

4. Join Date
Jan 2005
Location
S.E. Oklahoma
Posts
335
nsmith,
Would that be one resitor per LED or could you run a string of them?

5. Join Date
Sep 2006
Location
Laurel, MS
Posts
1,026
You could run a string of them (series), by reducing the value of the resistor. Each LED will take about .7 volt to bias it, which reduces the current as each LED is added to the string (dimming all).

If you parrallel the LED's with one resistor, the LED's will split the total current between them and get dimmer. Also, each LED will bias at a slightly different voltage and will cause the current to split unequal.

For ease of setup and operation, as long as space was not an issue, I would just use 1 resistor for each LED. Resistors are cheap.

 If you are using a LOT of LED's that are on at the same time. From a power usage standpoint you would string them together in series and use the appropriate size resistor to limit the current to the 15-20 mA range.

[size="1"][ January 06, 2007, 03:41 PM: Message edited by: nsmith1957 ][/size]

6. Join Date
Jan 2001
Location
New York City
Posts
3,397
There are LEDs with built-in resistors that can
be directly attached to common voltages (5 VDC,
12 VDC, 15 VDC, perhaps others).

Check out Digi-Key and the other online electronic
supply houses.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•