555 help needed by a novice

[Spanky]

Hi Everybody,

I hope someone in here can help me out, my electronics knowlege is very
limited.

I need a circuit (I think it's called a monostable multivibrator) which when
powered up closes a relay for 1.5 seconds then opens it back up
indefinently. When power is removed from the circuit the relay should
remain open.

The requirements are-

The whole thing needs to operate on 12-15 VDC (in a car)
The pulse timing needs to be fairly consistent (within 500ms)
The only trigger the circuit will have is the 12 VDC that powers it.

Can anyone point me in the right direction? If someone can give me a
scematic that would be fantastic!


TIA.

 

[The real Andy]

Hi Everybody,

I hope someone in here can help me out, my electronics knowlege is very
limited.

I need a circuit (I think it's called a monostable multivibrator) which when
powered up closes a relay for 1.5 seconds then opens it back up
indefinently. When power is removed from the circuit the relay should
remain open.

The requirements are-

The whole thing needs to operate on 12-15 VDC (in a car)
The pulse timing needs to be fairly consistent (within 500ms)
The only trigger the circuit will have is the 12 VDC that powers it.

Can anyone point me in the right direction? If someone can give me a
scematic that would be fantastic!

I remember designing a thing like this when I was a wee little first year
apprentice. It was designed to extend interior light delay without chomping
through wires and shit. The fuckwit teaching at tech didn't believed that I
designed it so I told him to get fucked and went off down the pub for a
beer. I got in the shit of course. The dickhead told me I would go nowhere
in life, he was probably right but gee he was pissed off when I aced his
exam.

Anyway, I am guessing you want it for lights or some shit like that. I would
try and do an ascii schematic right now but I am too pissed so you will have
to wait. IF you want the circuit for a valet light in the car, then do a
google search for "valet light schematic" if you want for some other shit,
then do a search on monostable multivibrator.

PS, too many of them 555's will kill of your braincells. Try only to use
them on weekends.

 

[[email protected]]

Hi Everybody,

I hope someone in here can help me out, my electronics knowlege is very
limited.

I need a circuit (I think it's called a monostable multivibrator) which when
powered up closes a relay for 1.5 seconds then opens it back up
indefinently. When power is removed from the circuit the relay should
remain open.

The requirements are-

The whole thing needs to operate on 12-15 VDC (in a car)
The pulse timing needs to be fairly consistent (within 500ms)
The only trigger the circuit will have is the 12 VDC that powers it.

Can anyone point me in the right direction? If someone can give me a
scematic that would be fantastic!

TIA.

http://www.national.com/pf/LM/LM555.html
--

Regards
David

=================================
Reply to

dmmilne at ozemail dot com dot au

 

[The real Andy]

Gawd, what type of encoding do you use? Outhouse express shows your messages
in some kind of fucked-up font. Are you posting in plain text or some user
defined character set??

I think I need to buy the latest agent software. Outhouse really shits me
off.

 

[[email protected]]

Gawd, what type of encoding do you use? Outhouse express shows your messages
in some kind of fucked-up font. Are you posting in plain text or some user
defined character set??

Plain ascii, the font is user defined.

I think I need to buy the latest agent software. Outhouse really shits me
off.

You can d/load the patches for Outlook 6 from the ms site.

--

Regards
David

=================================
Reply to

dmmilne at ozemail dot com dot au

 

[Spanky]

Thanks Andy,

It'll be used to switch a laptop on when the car ignition is switched on -
tha laptop requires a momentary contact (ie. the laptop does not switch on
until the button has been pressed AND released). A quick digram or
description would be great. I only JUST passed my year 12 electronics exams
so please be gentle.

 

[Spanky]

Thanks David,

The key word here is 'novice', see my reply to Andy. Could you possibly
explain the circuit to me like I was a 12 year old?

 

[Russ]

Hi Everybody,

I hope someone in here can help me out, my electronics knowlege is very
limited.

I need a circuit (I think it's called a monostable multivibrator) which when
powered up closes a relay for 1.5 seconds then opens it back up
indefinently. When power is removed from the circuit the relay should
remain open.

The requirements are-

The whole thing needs to operate on 12-15 VDC (in a car)
The pulse timing needs to be fairly consistent (within 500ms)
The only trigger the circuit will have is the 12 VDC that powers it.

Can anyone point me in the right direction? If someone can give me a
scematic that would be fantastic!

Depending on the application, you could do this with a capacitor and
resistor - and maybe a transistor, depending on the relay. I did this in my
car years ago on the amp-power line from my stereo to delay the power-on
thump of the crappy power amplifier I had on my rear speakers.

Russ.

 

[Spanky]

I don't think you quite understand what I need-

1. Power on
2. immeadiately close relay
3. Wait preset amount of time then open relay contacts
4. Do nothing for an indefinente period
5. Power off
6. Repeat

 

[John Crighton]

Hi Everybody,

I hope someone in here can help me out, my electronics knowlege is very
limited.

I need a circuit (I think it's called a monostable multivibrator) which when
powered up closes a relay for 1.5 seconds then opens it back up
indefinently. When power is removed from the circuit the relay should
remain open.

The requirements are-

The whole thing needs to operate on 12-15 VDC (in a car)
The pulse timing needs to be fairly consistent (within 500ms)
The only trigger the circuit will have is the 12 VDC that powers it.

Can anyone point me in the right direction? If someone can give me a
scematic that would be fantastic!


TIA.

Hello ?
have a browse through the circuits on this web site
http://dspace.dial.pipex.com/terrypin/indexpersonal.html

I think this is what you are looking for
http://dspace.dial.pipex.com/terrypin/Images/555Mono+Driver.gif

Regards,
John Crighton
Hornsby

 

[Ken Taylor]

You could do a search on '555 monostable' but in case you can't, look at:
http://www.doctronics.co.uk/555.htm
for just one site. If they don't show the calculations there's a tonne (in
metric) of other sites which do. Just add a relay (via a transistor if
required) to do your function.

Ken

 

[Steve]

1; get a data sheet for the LM555 by typing "LM555.pdf" into google.
You will find that it runs happily on up to 15V.

2; if it's similar to the one I have, near the end of the document
will be several design examples. Find the one for the Monostable.

3; use the graph provided to ascertain the correct values for the
capacitor & resistor. Will require some experimentation, but it looks
to around 1M resistor and maybe a 2.2uF cap or so for a pulse of 1 and
a bit seconds.

4; build the circuit exactly as shown, placing the predetermined
values in their place.

5; add a delay circuit to the trigger pin to trigger the timer. I
used a 360R and 47uF because that's what I had lying around. In the
real circuit you'll want to check to make sure the power and voltage
ratings aren't exceeded.

Perhaps a current limiting resistor from the supply would be a good
idea too. I haven't bothered with this in my quick and nasty trial.

So here's what happens; the power goes to the chip via pin 8, pin 2
is held low for a short while by the delay circuit, thus triggering
the timer. Pin 3 (output) goes high. The cap across pin 6 charges up
after about a second, triggers the 555 and the output turns off.

Now it's just a matter of connecting pin 3 to a transistor and relay
arrangement to do the actual switching. I threw in a diode from
emitter to ground as the 555 output doesn't quite make it to 0V hence
it won't switch off the transistor. Also, I found the output was
creeping back up and switching the relay on again. (perhaps due to
the transistor I used not handling the current it's passing) I gave up
at this point, after all, I can't do it all for you!

here's what I ended up with, it works, but I've done NO CALCULATIONS,
just threw some junk box parts together. Double check power in the
resistors and transistor dissipation before trusting the circuit!



1Mohm 2.2uF
___ Timing circuit ||
VCC-|___|---------------||---------------
| | || | |
time (sec) = 1.1R x C | | --- 0.01uF ===
| | --- GND
| | |
VCC | | -----
| | | |
o_o_o_o
| | VCC
| _555_ | |
1 o o o o C|
| | | | C|relay coil
GND | | VCC C|
___ | | |
VCC-|___|- --- | |
| | |/
Power on delay circuit--- -------|
--- |>
time (sec) = R x C | |
| |
| V
| -
| |
---------------
|
===
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de


nifty

 

[Spanky]

Thanks everyone, with your help I've managed to get an operational circuit.
The end result is the same as this one-
http://dspace.dial.pipex.com/terrypin/Images/555Mono+Driver.gif

 

[John Robertson]

Hi Spanky,

You want to check with your local public library to see if you can get
a copy of Lancasters book "The 555 Cookbook" A great resource!
Explains everything down to a high school level student and will give
you the answers you need plus a lot of the theory in clear text so you
can modify his circuits to do what you want.

Don Lancaster also has a web site (google it) and might have chapters
etc there of the book.

Another project book you might want to consider is titled "The Voice
of The Crystal" (How to build working radio receiver components
entirely from scratch) - He really means building a radio from scratch
- he uses junk wire, old tin cans, bit os this and that and comes up
with wonderful AM radios - even shows you how to make simple
headphones out of curbside materials. A great project as it is almost
like magic how sound comes out of this contraption that is entirely
handmade. I found that book at www.sas.org Show you electronics
teacher the web site and info on the book, I think it is potentially
great material for students thinking of a life in electronics or
electronic engineering...

John :-#)#

Thanks Andy,

It'll be used to switch a laptop on when the car ignition is switched on -
tha laptop requires a momentary contact (ie. the laptop does not switch on
until the button has been pressed AND released). A quick digram or
description would be great. I only JUST passed my year 12 electronics exams
so please be gentle.

(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Spanky]

Thanks for the tip John, I would tell my electronics teacher but I haven't
seen him since I left school 10 years ago......

 

[John Robertson]

Heh, I misread your email - when you said to explain it as to a grade
12 student...

John ;-#)#

Thanks for the tip John, I would tell my electronics teacher but I haven't
seen him since I left school 10 years ago......

(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[The real Andy]

BTW: Bosch do a really nice relay that has delay like that. When opend up it
reveals a shiny little black critter with the words 555 laser engraved into
its back!!

Try your local car recycler and grab the EFI relay from a Fuel injected
holden or ford from around the 1985 era.

 

[The real Andy]

Oh yeah, check this out too.
http://www.eet.com/special/special_issues/millennium/milestones/camenzind.ht
ml