Need help please to work out relay

Thread Starter

Hurdy

Joined Feb 27, 2006
137
Hi everyone,

firstly thank you for taking the time to read this.
I need to replace a relay in a locomotive battery charger.
The only problem is, is that the relay has no ratings written on it at all. The relay is just blank.

It's a plug in relay that has 8 pins in a circle that mount into a holder.

How can I find out what the rating of the relay is? or is it a case that I have to work back the electronics that plug into it?

Thank you again for your time,

Rob
 

thingmaker3

Joined May 16, 2005
5,083
If there are no markings, and no documentation is available, the only remaining option is to analyze the circuit it came from. Be sure to choose a replacement with at least 120% of the rating needed.
 

Thread Starter

Hurdy

Joined Feb 27, 2006
137
Hi,

Thanks for your reply. I've attached a diagram of the relay setup along with the TRIAC PDF that hooks up to the relay.
Does anyone know what rating relay would suit this?

Thank you,

Rob
 

Attachments

SgtWookie

Joined Jul 17, 2007
22,230
See the attached for a typical internal wiring diagram for an octal relay.
That's what they're generally called here in the USA, but seeing as the UK and the USA are separated by a common language, there's no telling what you blokes over there might call 'em. ;)
 

Attachments

SgtWookie

Joined Jul 17, 2007
22,230
Rob, there certainly are a lot of pieces missing from that schematic you posted, like which terminal of the TRIAC is which, the correct numbering of the pins on the relay, where the other relay connections go to, etc.
 

Thread Starter

Hurdy

Joined Feb 27, 2006
137
Hi guys thanks for your reply.
The relay has no other connections to it. That's it just 3 of them. As for the TRIAC it's not clearly labelled what their pins are on the component but I'll try and work it out and get back to you on it very shortly.

Thank you for your input so far, it's very much appreciated.
 

beenthere

Joined Apr 20, 2004
15,819
I question the nature of the device. A relay needs two leads to the coil, and two more for contacts. Even if it's set up to be self-latching, it's still four connections.
 

Thread Starter

Hurdy

Joined Feb 27, 2006
137
ok guys I've updated the diagram with the TRIAC pin numbers and attached it to this post.

The application is for a railway locomotive battery charger. My father is part of a railway enthusiasts group and he asked me to try and replace the relay.

PLEASE IGNORE THE RELAY PINS ON THIS DIAGRAM I'VE GOT PINS 1 & 2 THE WRONG WAY AROUND.
A NEW DIAGRAM IS POSTED AGAIAN IN THIS THREAD.
 

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Thread Starter

Hurdy

Joined Feb 27, 2006
137
The POT is used to limit the current as not to over charge the battery.
I guess it's some kind of trip off device setup if the current being pulled is too high.

I don't really understand the operation of a TRIC well enough to understand what is going on with this setup. I've tried googling for a guide but no luck as of yet.

Also are all pins labelled 1-8 standard throughout all plug-in relays? if so then from that we should be able to work out what the coil raiting is and what the contact raiting is. Like you said I always assumed a relay needed 4 connections, 2 for the coil 2 for the contact. Maybe the relay acts as a switch that when the relay magnetizes enough i.e. the current being pulled is to great it just creates an open contact and protect the rest of the equipment.
 
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thingmaker3

Joined May 16, 2005
5,083
Upon reflection, I don't think the 8-pin package contains a relay at all. I suspect it contains a diac and a capacitor...

choochootrain.jpg

I suggest attempting to open the "relay" package to see what is actually inside it.
 

Thread Starter

Hurdy

Joined Feb 27, 2006
137
oh you might be right. I've never seen a capacitor package like that before.
I'll open it up and see what it is. Thank you.

As for the battery it plugs in later on in the circuit which I haven't drawn once the AC has been rectified to DC.

Thank you for your suggestions it's much appreciated.
 

Thread Starter

Hurdy

Joined Feb 27, 2006
137
Well you're right it's not a relay. I finally had a reply from the guys who made the charger and they said it's not a relay it's a control module. They're going to send me a new one.

Learn something every day don't you.

Thank you very much for your help that goes to everyone. I really appreciate it.
 
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