Alt-BEAM Archive
Message #09111
To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@telus.net
Date: Wed, 12 Jan 2000 16:27:52 -0800
Subject: [alt-beam] Re: yet more motors
johannes urke wrote:
>
> hehe i know even less about solenoids,
> aint got a clue what it is so inform me a bit on this one
In it's most basic form:
A wire coil.
An iron rod passing through the middle of the coil, free to slide.
A spring which pushes the rod to one side.
Energise the coil. The resulting magnetic field causes the rod to centre
itself in the coil. Remove the current and the spring pushes the rod off
centre.
There are many, many variation on it.
Regards,
Bruce
9112 Wed, 12 Jan 2000 18:38:03 -0800 [alt-beam] Re: BEAM VIDEO was Solar Powered Camera's "'beam@sgiblab.sgi.com'" Wilf Rigter A little more food for thought.
One factor you have to consider when designing multiplexed LED matrix
displays is the "duty cycle" or ON/OFF ratio for the LEDs. With a 8x8
matrix of (64) LEDs, each LED is ON for about 1% of the time. High
efficiency LEDs will be usable at 1-2mA average current which at 1% duty
means a peak current of 200mA. 74AC240s can probably handle this but it is
close to the limit of what you can do with a multiplexed display. An
alternative design for larger LED matrix displays can use analog horizontal
line memories (2 Nu strings with tristate outputs) which are displayed a
line at a time. You need two because while displaying one line memory (input
disable and tristate output enabled), the second line memory is "loaded"
(input enabled and output tristated) and then they alternate.
Over the next couple of days I will have time to test and refine these ideas
and will report back soon.
wilf
Home