[Systems Engineering Teachers' Mailing List]Appliancecutawaydiagrams

[Alex Roujnikov]

Thank you Ray,
 
You are the only who replied so far. Project is OK to activate the relay except it remains activated instead of dropping off.
1. Yes, I tried 9V, 12 V battaries, a proper variable power supplies and  nothing helped.
2. I phoned  DS and technician admitted that it may be a problem with dropping off after 1 or 5 min and adviced me to activate relay by opening and then close contacts again. It did not work either. 
I will try to use  CMOS LM555 instead of TTL NE555 timers but I reckon it is not the solution.
 
Tank you, Alex

________________________________

From: syseng-bounces at edulists.com.au on behalf of Raymond Smith
Sent: Fri 6/27/2008 10:01 PM
To: Systems and Engineering Teachers' Mailing List
Subject: Re: [Systems Engineering Teachers' Mailing List]Appliancecutawaydiagrams



Gee Alex,

You are going back many years.  I can remember that project and it was
always ok.

Really don't think your 555 has anything to do with it, especially as it
came with a kit.

How are you applying power?  Are you using a true DC source, or a power
pack.  Many power packs, especially from the Science Department, are not
properly filtered.  I've fixed a lot of them!

Try a true 12 DC power source.

Ray S.
----- Original Message -----
From: "Alex Roujnikov" <aroujnik at penola.melb.catholic.edu.au>
To: "Systems and Engineering Teachers' Mailing List"
<syseng at edulists.com.au>; "Systems and Engineering Teachers' Mailing List"
<syseng at edulists.com.au>
Sent: Monday, June 23, 2008 9:23 AM
Subject: RE: [Systems Engineering Teachers' Mailing List]
Appliancecutawaydiagrams


> Hi SE and Electronics teachers.
>
> This year I bought "Home and Car Burglar Alarm Module " kits for year 9 .
> This is DS, Volume 2, project 15.
>
> All modules have the same fault: they are easily activated by N/O or N/C
> contacts but do not "drop off " voltage from the output, pin 3 afterwards.
> Capacitor charges up to 2/3 of Vcc  but Schmitt trigger at the input 2
> does not flip. I spent some time valuating and contact DS staf.
>
> DS staff was not very supportive, they adviced me "to check the circuit
> diagram".
>
> Are you familiar with this particular kit? Shall I try LM 555 instead of
> TT logic NE or ?? Please advice.
>
>
> Thank you,
> Alex Roujnikov,
> Penola Catholic College
>
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