Alt-BEAM Archive

Message #00515



To: Justin jaf60@student.canterbury.ac.nz
From: Chiu-Yuan Fang chiumanfu@home.com
Date: Tue, 16 Feb 1999 20:31:18 -0800
Subject: [alt-beam] Re: 240-based 'reverser' query


Justin wrote:
> http://www.beam-online.com/Robots/Circuits/reverser.gif
> I've breadboarded the reverser circuit, and have the outputs connected
> to two LED's of opposed polarity (ie a low-current indicator of the
> polarity of the output). I have the circuit powered by 3 AA's in series,
> and the battery pack is also connected to the inputs.

"two LED's of opposed polarity" to ground??? You mean you connected two leds in
parallel, opposite polarity? The Led with it's anode to ground will never turn
on because the output of the reverser is always positive (or zero) and the LED
always reverse biased. Move that anode lead to positive. If I totally misread
the question and insulted your intelligence then...sorry.

Remeber to use series resistors too.

> One last question, the reverser circuit shows both sets of inputs on the
> left side of the 74hc240 and the outputs on the right, yet AFAICS, the
> output of the inverters is on the left side for the second set of
> inputs/outputs. Does it not make a difference which end you use, or is
> the circuit wrong, or have I missed something obvious?

The 74HC240 drivers alternate. I'm not going to attempt to explain...check your
data sheet.

http://www.geocities.com/SouthBeach/6897/extras.html

Here's a qeustion for Ian. Are the 47Kohm resistors for implex or some other
reason?

Also, try the 4016 reverser. You can get a whole tube of 25 4016 chips from
Electronic Goldmine for $4.00

--
Chiu-Yuan Fang
chiumanfu@home.com
ICQ=5614919
http://www.geocities.com/SouthBeach/6897/beam2.html

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