Some Basic Advice Needed...

[GrayFox]

Well it has been about 45 years since I took an electronics course in college and it has all evaporated /ubbthreads/images/graemlins/help.gif

In an effort to get something going I have started reading Randy Slones book "Electricity and Electronics" and I have found a nice on line book Lessons In Electric Circuits . I was scanning AMAZON and Grob's book "Basic Electronics" ( I think...) seems to have a lot of good reviews but it is fairly expensive. Is it worth the money? Any other book references?

I have downloaded MacSpice and MI-Sugar to try to get some experience with simulations. It appears to me that Spice seems to want to consider current flow as emanating from the +, some of my books assert electrons flow from - to +. It is a bit confusing...

I think I will probably order a breadboard and wire kit from CircuitSpecialists tomorrow. CircuitSpecialists does not appear to have a grab bag of resistors. Does anyone know of an online source that sells an assortment of resistors. What power ratings should I look for?
(I plan on "messing" with leds for a while...).

Is is possible to get a nice power supply for under $100.00 that will allow the setting of voltage and current in the ranges that might be appropriate for led experimentation?

Thanks

Jerry

 

[JSWrightOC]

I can answer a couple of your questions.

The "conventional" current methodology says that current flows from positive to negative; I believe this is the most widely-accepted practice in electronics. Even a diode symbol in a schematic "points" to the more-negative cathode. "Electron" current theory says that electrons flow from the negative side to the positive side--which is probably the more accurate theory, but less widely accepted.

As for a source of electronic components and test equipment (such as power supplies) I would first try Jameco and then Digi-Key. Jameco has reasonable prices on equipment and parts. Their 1/4W resistor assortment is adequate for most needs (1/4W is plenty when working with 5mm LEDs, if you are working with Luxeons you'll want to use Ohm's Law to figure out how much power you'll be dissipating). Jameco also carries a good jumper assortment for protoboards.

Good luck on your project building!

 

[CNC Dan]

I have to recomend "getting started in electronics" available at radio shack. Gives a good introduction to all of the componants you will likly use and explains things well. lots of easy circuits too.

 

[MrAl]

Hello GrayFox,

Welcome to the world of electronics :-)

My advice about the conventions of current flow,
either (+) to (-) or, (-) to (+) is this:

Dont let it get to you! It's much easier then it
seems at first, i promise you. It's sort of like
what color to paint your house :-) It doesnt
matter THAT much.
The only thing that does matter is, once you decide
which convention you are going to use, you have to
use that convention throughout the entire circuit.
You can always switch conventions from circuit to
circuit, but you cant switch within the same circuit.

Sometimes the literature decides for us, so we have to be
able to understand both conventions of current flow if
we are going to read many books on the subject.
It's not all that difficult however, because it's only
a matter of changing the sign of the current from
plus to minus or vice versa. We either say (for example)
"minus 2 amps" or we say "plus 2 amps". It doesnt matter
as long as we always take the same convention within the
same circuit.

If we are building a circuit that has an LED and a resistor
and we decide we like 'plus to minus' current flow best,
we label all the parts plus and minus according to this
convention, and we make sure not to switch to the 'other'
convention while we are analysing this same circuit.
If we happen to switch to another circuit we may wish to
change our preference, but that is another circuit.

If we are reading a book on circuits and we want to follow
the examples and such we have to learn to adopt to the
standard the writer decided to use when authoring the
book--in this case it's not our decision.

In any case, one convention or another, it's just a matter
of sign, plus or minus. Once you take it as one way
or another you stick with it within the same circuit.
If you switch circuits, you then have the option of
again switching conventions.

Im sure you will find many people here willing to
assist you with your first circuits, LED's or other.

As a last note, i would advise you to become familiar
with ohms law and resistors. Once you understand most
of what there is to know about a single resistor in
a circuit with say a battery, you can move on to
resistor networks. Resistor networks are simply
circuits that have more then one resistor in them.
Once you understand resistor networks, you will be
surprised to find you can analyse all kinds of
circuits using the same basic principles.

Understanding ohms law is the first step to understanding
the LED and resistor circuit, which although so simple,
is one of the most reliable lighting circuits under the
sun :-)

Good luck with your future circuits,
Al

 

[IlluminatingBikr]

[ QUOTE ]
GrayFox said:
Is is possible to get a nice power supply for under $100.00 that will allow the setting of voltage and current in the ranges that might be appropriate for led experimentation?

[/ QUOTE ]

I know the perfect thing! Link! /ubbthreads/images/graemlins/grin.gif

 

[Ferrous]

Current flows from the raisin to the plum pudding.

Why not let the power supply be your first project? It'll fit the budget and you'll learn while you make it.

 

[GrayFox]

Ferrous: Are you trying to get me electrocuted....I have to learn to crawl before I try walking.

Aaron: Hey that is a nice site, I downloaded the catalog. It looks like the 30v/3a power supply might be a bit more versatile.

Al: Is it true that one has to do a dc sweep before you can get any info from spice?

CNC Dan: I will check out radio shack soon...

JSWrightOC: MPJA looks a bit less expensive.

Thanks Guys!

--Jerry

 

[eluminator]

I have the 30v/3a one. HY3003. It has coarse and fine adjustment knobs for current and voltage. I recommend it.

It's a minor thing, but I also prefer the LED displays. You never saw an LCD flashlight, did you?

elexp.com also sells the HY3003.

 

[JSWrightOC]

GrayFox:

Yeah, I forgot about MPJA. They sell a lot of surplus stuff, and so their deals will probably be better. Sorry I didn't point you in quite the right direction.

 

[MrAl]

Hello again,

>>>I know the perfect thing! Link!
That's a very nice power supply!

>>>Al: Is it true that one has to do a dc sweep before you
>>>can get any info from spice?
It probably depends which software you are using. With
the circuit analysis program i use most the only time
i come into direct contact with Spice is when i write up
a new model for a new part or have to adjust parameters
for an old model. In that case it's good to know the
syntax for at least the most common things.
BTW, I have models for the Nichia and 1 watt LS also :-)


Here's an example of a white LED model:

* Node assignments...
* pos: anode(longer lead)
* neg: cathode(body flat)
*
.SUBCKT LEDW03 pos neg
*
* zero ohm current sense:
VM pos 1 0

* current dependent voltage source:
BX 1 2 v = -i(VM)*i(VM)*29.98

* diode:
D1 2 neg DX

*
.MODEL DX D(IS=7.61384e-013 N=4.9954 RS=17.14)
.ENDS



Take care,
Al