[Systems Engineering Teachers' Mailing List] Appliancecutawaydiagrams

[Raymond Smith]

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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