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Basic circuit with relay

Former Member

Hi.

First of all: I hope this is the place to post.

 

I am gonna make an easy circuit with a relay to control a pump.(see attachment)

I understand the principal, but I wonder if there is anything more I gotto think of, like resistors or something?

 

It is not to be used in a car.

 

I am thinking of using an car relay: 12V, Max 30 amp.

The pump use 12V and 4 amp.

The fuse need to be 4 amp?

 

Can the switch for example be wired directly to pluss and minus on the car battery or do I need a  resistor there?

Thanks!

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    Alas, I am at home in the city and my shop is in the 'burbs, drawing program is out there.  Shunt means 'in parallel' or across.  Backward means that the diode is supposed to be in blocking mode during the normal operation of your circuit.  The diode across the load only 'comes on' after your relay turns off.  The little implicit arrow of the diode should be opposed to the current flow when your load is energized.

     

    Actually, 'snubbing' more properly refers to reactors used for this function, although the term 'snubber diode' is in common parlance.  It is probably just as well to call this diode a clamp.  What throws so many beginners is that their first encounter with this problem is in the context of unipolar stepper motors, where the diode in one transistor, due to the way the motor is wound, snubbs (see, I do it too) the load of its neighbor.  This throws them on the voltage signum.  Just remember that a coil or inductor opposes changes in current through it by sourcing/sinking potentials which appear on the switch attempting to do the changing.

     

    As for your fuse, go with around six Ampere.  You need some operational headroom.  The fuse protects against gross flaw.

     

    Ever seen a 'Jacob's ladder?'  That's arcing.  The potential from the spike is so high it breaks down the air and causes a spark.  A circuit that intentionally relies on the magnetic decay of an energized coil is called a 'flyback.'

     

    I think you should be fine hooking up directly to the battery.  I use sealed AGM (adsorbed glass mat) batteries for this purpose.

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  • 0

    Alas, I am at home in the city and my shop is in the 'burbs, drawing program is out there.  Shunt means 'in parallel' or across.  Backward means that the diode is supposed to be in blocking mode during the normal operation of your circuit.  The diode across the load only 'comes on' after your relay turns off.  The little implicit arrow of the diode should be opposed to the current flow when your load is energized.

     

    Actually, 'snubbing' more properly refers to reactors used for this function, although the term 'snubber diode' is in common parlance.  It is probably just as well to call this diode a clamp.  What throws so many beginners is that their first encounter with this problem is in the context of unipolar stepper motors, where the diode in one transistor, due to the way the motor is wound, snubbs (see, I do it too) the load of its neighbor.  This throws them on the voltage signum.  Just remember that a coil or inductor opposes changes in current through it by sourcing/sinking potentials which appear on the switch attempting to do the changing.

     

    As for your fuse, go with around six Ampere.  You need some operational headroom.  The fuse protects against gross flaw.

     

    Ever seen a 'Jacob's ladder?'  That's arcing.  The potential from the spike is so high it breaks down the air and causes a spark.  A circuit that intentionally relies on the magnetic decay of an energized coil is called a 'flyback.'

     

    I think you should be fine hooking up directly to the battery.  I use sealed AGM (adsorbed glass mat) batteries for this purpose.

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