Alt-BEAM Archive
Message #05265
To: SG Sparkyg@seark.net, BEAM beam@sgiblab.sgi.com
From: Richard Piotter richfile@rconnect.com
Date: Mon, 12 Jul 1999 13:38:08 -0500
Subject: [alt-beam] Advice needed!
SG wrote:
>
> ok, attach ONE resistor to each lead of the LED. THEN to the motor
> connects... got it.
>
> I have the green Forest Mimms book, but honestly skipped about LEDS
> assuming they didn't draw much current and by the looks of other
> applications just assumed builders attached them to projects directly.
> thought it was self explanitory, but guess not!
> and yup! cats outta the bag now! im a novice!
> -Sparky
ONE resistor per LED: TOTAL!!!
(A) If you connect LEDs to individual sources and the other end to a
power rail
-----/\/\/\/------|>|------
Resistor LED
(B) If you attach the LED across two outputs of a driver (if it can
handle both LEDs and Motors)
-----/\/\/\/---o--|>|--o---
Resistor | LEDs |
'--|<|--"
The LED should NOT be BETWEEN the motor and the driver!!! That'll all
but STOP the motor from turning!
As for connectiong them, if your motors are efficient and your driver is
strong, you could attach the LEDs to the driver, but most people choose
to add them stright to the microcore. - polarity to the output of the
microcore's inverter and + polarity to the + power supply. use no lower
than 470 Ohms or so and I guess, use the highest resistor possible
before the LED dims too much. Also, Low current LEDs are great for this
purpose. I found some TINY rectangular ones but I forgot where tha were
from. even plain 3 mm leds should work. again, stay away from super
brights unless you run them from a driver. Make sure the resistor is
high enough as to not interfere with the microcore's opperation or short
the motors, or block their current.
[PNC]
|
_|______________
[___Micro_Core___] [+]
| | | | |
| | | | |
o---+---+---+---A---o
| | | | |
| o---+---+---A---o
| | | | |
| | o---+---A---o
| | | | |
| | | o---A---o
__|___|___|___|__
[__Motor_Drivers__]
| | | |
| | | |
| | | |
| \ / |
| X |
| / \ |
| | | |
| | | |
o-B-o o-B-o
| | | |
|___| |___|
[Motor] [Motor]
This setup shows how to hook up the (A) and (B) style LED arrangements.
If the microcore goes into saturation, the (B) type LED setup will NOT
light! Just as the motors WON'T turn. The (A) type LED setup will flash
EXACTLY as the Microcore is opperating, even showing it if it goes into
saturation. Type (A) is typicaly the setup used. It's possible to use
the type (B) on the microcore, but it's touchy if you draw too much power.
First though, READ the book. that's my best recomendation. NEVER assume
you know what to do, cause quite frankly, you're bound to screw
something up if you don't know all the details.
You can't just decide to build something. you must know what your doing
first. That has to be learned. Go back to that green book and read each
and every word about LEDs till you understand WHY it works this way.
There are two ways of building electronics:
Build by knowledge and expirience, or build by guide and memorization.
You build by guide and memorization, and you can't cope with problems
when they occur cause you don't understand them. They go beyond you, and
you cry out for help from others cause you have no expirience to rely on.
You build by knowledge, and you can understand WHY a circuit works and
not just how to assemble it. if you have a problem, you at leas have a
chance of trying to understand and repair the problem. if you can't fix
it yourself, you at least know you tried.
Read that book, and maybe play with some electronics kits if you can
afford it and get one cheap. I know it sounds dumb, and some expiriments
seem like a school class on electronics, but that's WHAT IT IS! you
might be tempted to build the roulette lights or the radio transmitter,
but then you're just building by guide and memorization. you still don't
understand what it's actualy made from and why it works. start from the
beginning and work through it. My old 200 in 1 kit was great. it covered
numerous areas of electronics, and I highly recomend that beginners with
cash trying out such a kit. It's not the most ideal trainer, but it
works, and is reasonably priced. the Forest Mimms book though is a must
to all beginners. I have it, my friends have it, WE'RE IN COLEGE!!! I
still find it useful!!! that alone should show you ther's more to that
book than it looks.
Read it!!! it's a great book!!!
--
Richard Piotter
richfile@rconnect.com
The Richfiles Robotics & TI web page:
http://richfiles.calc.org
For the BEAM Robotics list:
BEAM Robotics Tek FAQ
http://people.ne.mediaone.net/bushbo/beam/FAQ.html
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