Delaying a relay

[pyromatt]

Hi,
Ive been told that a capacitor can do this job. All I need to do is delay a relay from triggering for a fraction of a second (to ensure a second relay triggers first.) There only small relays (for 10A) so I was wondering what size capacitor to go for and should it be wired in series or parrellel with the relay coil?

Many Thanks,
Matt.

[kane]

A capacitor is not ideal as it will cause the voltage to rise slower than just a straight switch to (12v). Ideally, you want a small timer circuit to delay the switch on.

The best way to overcome this is to wire your second relays coil onto the switch side of the first. That way the only way it will fire is if the first one has fired.

[pyromatt]

The problem is the relays are not always both activated at the same time. Sometimes, just the first will need to be triggered, sometimes just the second. I just wanted to make sure that if both relays are triggered together, that one of them definatly contacts first.

[kane]

How critical is it that relay 2 activates after relay 1 when they are both fired?

E.g. What are they doing?

[pyromatt]

its to ensure that current is directed the right way. Basically, i have two inputs and two outputs
Input1 = on, Input2 = off, Output to number 1.
Input1 = on, Input2 = on, Output to number 2.
Input1 = off, Input2 = on, No Output.
Input1 = off, Input2 = off, No Output.

[woody]

Strange request ...... 2 SEPERATE inputs ?!

Quick sketch on my profile showing a possible solution with 2 change over relays and one input.

It gives the required switching ......
Edit ...BOTH relays are OFF in the sketch.

Relay1= on, Relay2 = off, Output to number 1.
Relay1 = on, Relay2 = on, Output to number 2.
Relay1= off, Relay2 = on, No Output.
Relay1= off, Relay2 = off, No Output.

Give the Forum more idea of WHAT and WHY your doing this...

(Message edited by woody on December 06, 2005)

[killercarrot]

is it some kind of weapon that fires a different way if the beasty is upside down?
mercury switch on the relay 2? fire button on 1?

[jim]

Matt, it is practically impossible for both inputs to switch on simultaneously. Regardless of what you use to control them, there will always be some delay between one input becoming on and the other one, even if it is a few nanoseconds. Maybe you need to specify a time interval which you want to treat as simultaneous for the purposes of your application.