Relay Amperage

[AHarris]

I am in the process of designing my control system, comprising of 6 DPDT relays and some spring loaded flip switches.

The motors which I am using are expected to draw about 10 Amps underwater, does that mean I need relays which are rated for more than 10A or are the motors draw not going through them?

I'm rather confused about relay wiring so I'm hoping one of you would be able to help me.

Thanks

[scubersteve]

The purpose of a relay is to allow a low current carrying device (your switch) to control a higher load device (the motor) by means of the relay.
Therefore, no, you do not need a switch rated for the full load of the motor.

[AHarris]

Thanks for clearing that up Scubersteve, saved me about £7 ($11) per relay!

[martinw]

In your post you asked about the current in the relays, not in the switches, am I correct?

If so the current rating of the relay needs to be that of your motor plus a bit of headroom. It also has to be DC, (direct current) rated at that current too.

Your flip switches will have to be able to provide enough current to activate the coil of the relay but the full motor current will travel through the contacts of the relay.

http://www.robmeyerproductions.com/bows.html

Hope this helps.

Martin

[AHarris]

Thanks for the reply,

So does this mean if I am going to draw about 10 Amps per motor I need a 12 Amp relay? Can this relay be rated for a higher voltage, for example: http://www.rapidonline.com/Electronic-C ... Ac-60-1675 which are 10 Amp 24V DC?

And for the switches, is it fine for them to be 12V rated at 2Amps?

Thanks!

[scubersteve]

I don't think you want those relays. You have to make sure that the relays you get can operate on the voltage you want to use. I doubt the coils on a 24v relay will operate on 12v. The same is true for the 110v AC relays.
I would go with the common automotive relays. They are 12v and can easily carry the current required.

The 2 amp switches should be fine.

[AHarris]

Even if it says:

Min. switching load: 1V DC, 10mA

I'm struggling to find some otherwise, at a reasonable price including shipping that is.

[scubersteve]

I believe that is referring to the load being controlled i.e. the motor.
In the description it mentions 110vdc coil voltage. That is referring what is required to operate the relay.
I don't remember where you are located, but there must be an automobile parts store nearby.
You should be able to go buy relays off the shelf.

[AHarris]

Thanks for the continued help scubersteve,

I shall look and see if I can find some, although nightmares of the last ROVs are coming into mind at the moment. This, finding PVC pipe online (no store shall stock anything suitable on the island I live on), and the budget where the main issues.

[thegadgetguy]

I clicked on "View full product range" on the website you posted, and found the 12 Volt version of the relay you posted. Here's a link:

http://www.rapidonline.com/Electronic-C ... Dc-60-1672

Unfortunately, it would appear you must order more than 100 relays at a time. However, I saw a few other relays that might work on that website:

http://www.rapidonline.com/Electronic-C ... es-60-4172
http://www.rapidonline.com/Electronic-C ... 82-60-4384
http://www.rapidonline.com/Electronic-C ... 22-60-4380

The second two are basically the same relay, as far as I can tell. They appear just to have different types of contacts on the bottom. They all look decent to me. What do you think scubersteve?