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Subject: Re: Electronics Newbie Needs Help With A Timer Delay Circuit...
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Date: Tue, 01 Oct 2002 07:58:22 GMT
NNTP-Posting-Date: Tue, 01 Oct 2002 09:58:22 MET DST
"Jake" schrieb im Newsbeitrag
> Hello out there in the world of USENET, this is my first foray into
> this public forum so here goes nothing...
> I am an average teenage male computer user who builds his machines,
> plays games, and stays up till 3 getting 9 extra 3dmarks out of his
> radeon...but when it comes to electronics and circuitry, I am lost.
That happens now even to CS-engineers.
I had an idea for an information podium with a
> simple button and a light bulb that would illuminate a transparency
> revealing a message. However, to drive home a point of "our" need (the
> societal 'our') for instant gratification, I wanted to introduce a
> delay into the button circuit.
First, and that is something you should know, make a flowchart of what you
want to happen.
Press any button
> lock the buttons until sequence is over
> start button delay
if wrong button > sequence over
if right button > trigger relais timer
on> activate relais >light message
off> sequence over
This is just an idea derived from your description. But you see, you will
need at least 2 timers.
The functional units can be explained later when you have worked out how you
want the logic to function.
>I was planning on using a regular ATX power supply
>to supply the circuit with 5V DC and running the light bulb, (or
>whatever), off of an AC line.
Use the +5V standby which is always present and keep the rest switched off
to avoid the fan noise.
Check the ratings of your relays, is it specified for mains AC?
Can it supply sufficient current for the bulb? For a 100W incandescent bulb
you will need at least a 6A rated relays.
What is the resistance of the coil? can a 555 supply enough current? always
use a diode(1N4148) across the coil with the stripe into the 5V direction.
Put a fuse(2A) into the mains line in case the bulb develops a short or
something goes wrong. Be sure there is a ground fault interrupter inside the
distribution box, ask the school electrician to check your setup. Do not put
the AC-voltage into your breadboard but mount the relays near the display
and have only the coil connections on the board.
good luck Ban
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