Fitting a Relay to Trolley

[Marko067]

I have just fitted a 40amp relay to protect the microswitch in my pump pressure switch after burning out two in less than six months.

My question to those of you who are better aquainted with electrics than mhs is; is it better to use the normally closed micro switch (in the pressure switch) and connect the pump to the normally open side of the relay, or a normally open microswitch and connect the pump to the normally closed side of the relay?

 

[spruce]

I have just fitted a 40amp relay to protect the microswitch in my pump pressure switch after burning out two in less than six months.

My question to those of you who are better aquainted with electrics than mhs is; is it better to use the normally closed micro switch (in the pressure switch) and connect the pump to the normally open side of the relay, or a normally open microswitch and connect the pump to the normally closed side of the relay?

Its sounds as though you have purchased a 5 pin relay. If you have and you are trying to work out which to connect the motor current to. It will be terminal 87 (not 87a). Hopefully I've understood the question correctly.
 

So you are using the power from the microswitch to power the relay as apposed to the pump. The coil in the relay is powered from the microswitch, usually terminal 86. Terminal 85 goes back to negative on the battery.

30 is the power terminal from the + on the battery and 87 goes to the motor.

 

[Marko067]

That sounds about right spruce. My first thought was to connect the pump to 87a, at least that’s what seemed to make sense until it didn’t work. So I figured that out pretty quick. However, as I understand it wired like this the coil in the relay is powered on when you activate the pressure switch, so in effect the whole time you are walking or driving between jobs the battery is draining, all be it slowly.

Would it not be more efficient to use a normally open micro switch and connect the pump to 87a? Or would this not work at all?

I ask because I use a trolley with a battery that just gives me a solid days use at present and I’m wondering if it would drain an amount I would notice is all.

I suppose I shall find out on Monday   :1f603: :1f603:

 

[spruce]

That sounds about right spruce. My first thought was to connect the pump to 87a, at least that’s what seemed to make sense until it didn’t work. So I figured that out pretty quick. However, as I understand it wired like this the coil in the relay is powered on when you activate the pressure switch, so in effect the whole time you are walking or driving between jobs the battery is draining, all be it slowly.

Would it not be more efficient to use a normally open micro switch and connect the pump to 87a? Or would this not work at all?

I ask because I use a trolley with a battery that just gives me a solid days use at present and I’m wondering if it would drain an amount I would notice is all.

I suppose I shall find out on Monday   :1f603: :1f603:

But you would switch the pump off using the on/off switch if travelling between houses.

The normally on terminal 87a goes off when the coil is energised. So the coil will switch the circuit to the pump off. The 5 pin relay is a combination relay; it can be used as a normally off or normally on or both depending on what it is used for.

The way you wire it up for our application is as per the 4 pin relay.

Here is a lovely little youtube video

 

[Marko067]

Thanks for that spruce. I shall have a gander later when I have a little more time. I did watch one vid which was helpful and the relay I purchased had a diagram on top which was also helpful. 

 

[Marko067]

Yep! That was worth a watch. I had wired up 30 and 87 back to front. It was working but wasn’t technically correct. 

I have also taken the power for the relay coil from the output side of the controller which is probably not a good idea. Again it seems to work as I work on full flow virtually all the time. However, when I slow it down below 80% the relay buzzes due to the pulsing. 

I’ll have to see how it goes. 

 

[spruce]

Yep! That was worth a watch. I had wired up 30 and 87 back to front. It was working but wasn’t technically correct. 

I have also taken the power for the relay coil from the output side of the controller which is probably not a good idea. Again it seems to work as I work on full flow virtually all the time. However, when I slow it down below 80% the relay buzzes due to the pulsing. 

I’ll have to see how it goes. 

I didn't realise you had a controller. Controllers are usually PWM and so send pulses of current to the motor. Unfortunately that system with destroy the relay pretty quickly.

 

[Marko067]

I didn't realise you had a controller. Controllers are usually PWM and so send pulses of current to the motor. Unfortunately that system with destroy the relay pretty quickly.

I thought that might be the case. So I'm going to rewire the microswitch to draw power from the battery side of the controller. It just means I'll have to fit a switch before the controller otherwise the coil will always be live as long as the battery is connected.