[Diy_efi] Time delay relay?

[Derek]

When you say coil, do you mean the coils of the relay?

Basically, here's what I'd like to do as simply as possible:

I have a input on my ECU which runs through a NC switch, to ground. When the
switch opens, I'd like the input on the ECU to continue to see ground for about
300-400ms after the switch opens.

However best way to do that, you tell me. I was just thinking a relay would be
best, but if there is something I can connect along that wire that can do the
same, all the better.

----- Original Message -----
From: "Mike" <erazmus at iinet.net.au>
To: <diy_efi at diy-efi.org>
Sent: Tuesday, December 24, 2002 12:13 PM
Subject: Re: [Diy_efi] Time delay relay?


> Here I go commenting on my own posts,
>
> <cough> Whats the duty cycle of your relat and whats it meant
> to drive ?
>
> rgds
>
> mike
>
>
>
> At 11:54 AM 24/12/2002, you wrote:
> >What the heck, I just realised you only want a few milliseconds,
> >then thats not a problem unless your coil has very low resitance,
> >but if its for driving something in an auot then its prob at least
> >a few hundred ohms,
> >
> >Here's my go at ascii art <sigh>
> >
> >     ----------------------------
> >     |                          |
> >+ve--+---->|------+----->|------+---- coil +ve
> >                  |
> >                  |+
> >                 --- electrolyic
> >                 --- cap
> >                  |-
> >                  |
> >                  +------------------ coil -ve
> >                  |
> >                  |
> >                  |
> >             To device which normally pulls relay on
> >
> >
> >Where -->|-- is a diode say a 1N4004 (1Amp) or if you
> >need something a bit meatier go for a 1N5404 (3A)
> >
> >and your electrolytic cap should be 2200uF 25V if your
> >coil resistance is about 270 Ohms, the 2200 is a preferred
> >value, you can go up a bit at a time, 3300, 4700 etc or have
> >a couple if parallel to trim the delay to what you want,
> >I'm guessing on your coil resistance though, higher coil
> >resistance wont need such a large capacitor.
> >
> >Overall shouldnt cost more than $AUD 3. (since you already
> >have the coil)
> >
> >rgds
> >
> >mike
> >
> >
> >
> >
> >
> >
> >
> >
> >At 11:41 AM 24/12/2002, you wrote:
> >>One very basic method is a big fat capacitor across coil with
> >>a pair of diodes to isolate the cap from the coil when off...
> >>
> >>Discharge time is approx t=1.1xRxC
> >>
> >>where R= reistance of coil, and C is the cap value in Farads,
> >>this way you can get a few seconds with practical caps and
> >>a K or so or coil resistance,
> >>
> >>But to get 100s best to put a schmitt trigger and caps on the
> >>drive to the coil transistor, others prob already have a circuit,
> >>its fairly straightforward,
> >>
> >>rgds
> >>
> >>mike
> >>
> >>
> >>
> >>At 02:48 PM 23/12/2002 -0800, you wrote:
> >>>Where can I find some relays with time delay? I have seen plenty of
> >>adjustable
> >>>.1-100s relays, up in the $50-$70 range. I need something simpler. A
> instant
> >>>ON/fixed delay OFF relay with a delay of about 250-500ms.
> >>>
> >>>
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