Low signal 5vdc relay non pcb

leeomurchu · 22-02-2013 6:41pm #1

Hey lads as the title suggests I'm looking for a 5V dc relay.

It has to be a standalone version as it won't be mounted on a board.

Something similar to this (flat type)but it needs to have a low switching current something around 40mA these have a min of 100mA.

Anybody got any ideas.

Thanks

Bruthal · 22-02-2013 7:58pm

leeomurchu wrote: »

Hey lads as the title suggests I'm looking for a 5V dc relay.

It has to be a standalone version as it won't be mounted on a board.

Something similar to this (flat type)but it needs to have a low switching current something around 40mA these have a min of 100mA.

Anybody got any ideas.

Thanks

What are you using it for?

Switching current? Are you talking about the current the 5v coil takes? If so, why is that a problem? If the device switching the relay cant switch the required current, a transistor switched from it, can easily be used to switch the relay.

22-02-2013 7:59pm

leeomurchu wrote: »

Hey lads as the title suggests I'm looking for a 5V dc relay.

Do you mean that the control voltage (the voltage applied across the coil) is 5V?
Is the control voltage AC or DC?
What voltage do you want to switch, 5VDC at 100mA?

It has to be a standalone version as it won't be mounted on a board.

If the control voltage is 5VDC you could use one of these and solder wires to the pins.

Out of interest why can you not use a PCB?
This can switch up to 15VDC.

leeomurchu · 22-02-2013 8:02pm

Bruthal wrote: »

What are you using it for?

Switching current? Are you talking about the current the 5v coil takes? If so, why is that a problem? If the device switching the relay cant switch the required current, a transistor switched from it, can easily be used to switch the relay.

Hi,

I'm using the relay to switch a 20A nc contactor but I'm having issues with the contactor not switching sometimes as the load is not high enough for the relay to energise the coil on the contactor.

leeomurchu · 22-02-2013 8:05pm

I'm using a pcb with a switchable 5vdc supply so I'll be using this to energise the coil on the relay but I want to energise a coil on a 20a contactor from the relay.

I forgot to mention what I'll be switching with the relay. oops.

I probably could use a single channel pcb relay but I may not have room so I was looking for one that I could mount elsewhere if needed.

Bruthal · 22-02-2013 8:05pm

leeomurchu wrote: »

Hi,

I'm using the relay to switch a 20A nc contactor but I'm having issues with the contactor not switching sometimes as the load is not high enough for the relay to energise the coil on the contactor.

Some sort of interlock setup similar to a shower priority setup?

leeomurchu · 22-02-2013 8:09pm

Bruthal wrote: »

Some sort of interlock setup similar to a shower priority setup?

It would be something like that not neccesarily a shower the contactor load may not be 20A sometimes only a few amps.

So I'm having an issue with the relay not energising the contactor coil.

It works fine when there's a high load on the contactor.

Bruthal · 22-02-2013 8:09pm

leeomurchu wrote: »

I'm using a pcb with a switchable 5vdc supply so I'll be using this to energise the coil on the relay but I want to energise a coil on a 20a contactor from the relay.

I forgot to mention what I'll be switching with the relay. oops.

I probably could use a single channel pcb relay but I may not have room so I was looking for one that I could mount elsewhere if needed.

Ok so the contactor is energised by the relay. What is controlling the 5v relay, as in what conditions cause it to become energised?

Bruthal · 22-02-2013 8:10pm

leeomurchu wrote: »

It would be something like that not neccesarily a shower the contactor load may not be 20A sometimes only a few amps.

So I'm having an issue with the relay not energising the contactor coil.

It works fine when there's a high load on the contactor.

So the 5v relay is controlled by a current sensing coil?

leeomurchu · 22-02-2013 8:32pm

Bruthal wrote: »

Ok so the contactor is energised by the relay. What is controlling the 5v relay, as in what conditions cause it to become energised?

The Relay would be controlled via a pcb board with a switchable 5vdc output.

It is switched remotely.

Bruthal · 22-02-2013 8:35pm

leeomurchu wrote: »

It would be something like that not neccesarily a shower the contactor load may not be 20A sometimes only a few amps.

So I'm having an issue with the relay not energising the contactor coil.

It works fine when there's a high load on the contactor.

A high load on which contactor though? A 2 contactor setup, so when one is loaded, it energises the relay to energise the other contactor, opening its contacts to switch off its load?

Its probably just me, but im not very clear what you are trying to do.

DublinDilbert · 22-02-2013 8:35pm

What voltage is the contactor coil you are trying to energise?

If the contactor is coil is running off 12 or 24V DC, I would just use a "low-side" N Channel mosfet to turn it on. The gate of the FET would easily turn on with 5V and will easily be able to sink the current required to pull in the contactor.

22-02-2013 8:37pm

It may be best to post a diagram.

22-02-2013 8:39pm

DublinDilbert wrote: »

What voltage is the contactor coil you are trying to energise?

If the contactor is coil is running off 12 or 24V DC, I would just use a "low-side" N Channel mosfet to turn it on. The gate of the FET would easily turn on with 5V and will easily be able to sink the current required to pull in the contactor.

Yes, I have heard that mosfets are now being used for switching heat tracing circuits (230VAC at 25A).

leeomurchu · 22-02-2013 8:39pm

DublinDilbert wrote: »

What voltage is the contactor coil you are trying to energise?

If the contactor is coil is running off 12 or 24V DC, I would just use a "low-side" N Channel mosfet to turn it on. The gate of the FET would easily turn on with 5V and will easily be able to sink the current required to pull in the contactor.

Sorry I'm not being very clear about this it's a 20A nc 230v coil contactor.

basically I need a 5dc relay that'll switch a 230V load (which will be the coil of the contactor)

the issue I'm having is that if the 230V contactor is switching a high load the relaay I have works fine 100mA but if the contactor load is low say 5-10A the relay will not switch.

leeomurchu · 22-02-2013 8:40pm

DublinDilbert wrote: »

What voltage is the contactor coil you are trying to energise?

If the contactor is coil is running off 12 or 24V DC, I would just use a "low-side" N Channel mosfet to turn it on. The gate of the FET would easily turn on with 5V and will easily be able to sink the current required to pull in the contactor.

any links to one of these. Is it a pcb mounted relay?

leeomurchu · 22-02-2013 8:42pm

2011 wrote: »

It may be best to post a diagram.

I'll try post one later. Drawing wouldn't be my strength

Bruthal · 22-02-2013 8:42pm

2011 wrote: »

Yes, I have heard that mosfets are now being used for switching heat tracing circuits (230VAC at 25A).

Are they not triac`s they are using?

22-02-2013 8:43pm

leeomurchu wrote: »

basically I need a 5dc relay that'll switch a 230V load (which will be the coil of the contactor)

As Dilbert said, a mosfet will do this. Apply 5V to the gate and switch 230VAC through the mosfet.

Bruthal · 22-02-2013 8:43pm

leeomurchu wrote: »

any links to one of these. Is it a pcb mounted relay?

He was taking about using a mosfet (type of transistor) to switch the relay, a logic level one will fully switch from 5 v. But its not suitable for an AC contactor.

22-02-2013 8:47pm

Bruthal wrote: »

He was taking about using a mosfet (type of transistor) to switch the relay, a logic level one will fully switch from 5 v. But its not suitable for an AC contactor.

Sorry, I was thinking of an IGBT.

Bruthal · 22-02-2013 8:48pm

2011 wrote: »

As Dilbert said, a mosfet will do this. Apply 5V to the gate and switch 230VAC through the mosfet.

Id imagine 2 mosfets would be needed to do that.

If the problem is very low switching current available to switch the 5v relay, then a transistor to switch the relay would be the method.

But im still lost as to the actual exact question.

leeomurchu · 22-02-2013 8:49pm

I'm thinking a little more heavy duty something along the lines of these. Flat type.

http://pewa.panasonic.com/assets/pcsd/catalog/jm-catalog.pdf

Bruthal · 22-02-2013 8:50pm

leeomurchu wrote: »

I'll try post one later. Drawing wouldn't be my strength

ms paint is actually good for that type of thing

DublinDilbert · 22-02-2013 8:52pm

leeomurchu wrote: »

any links to one of these. Is it a pcb mounted relay?

They are some times called a "solid state relay", which use opto couplers & mosfets to basically form a simple relay. Many soild state relays are designed to switch AC loads only, but ones are made to switch DC.

I had to do something similar, i needed to control a 24V contactor from a national instruments digital output (eg 5V out). I got a din rail mount solid state relay from RS.

Something like this would probably be the job for you:-
http://radionics.rs-online.com/web/p/solid-state-relays/7401321/

But RS literally have 100's of them

22-02-2013 8:52pm

Bruthal wrote: »

Id imagine 2 mosfets would be needed to do that.

If the problem is very low switching current available to switch the 5v relay, then a transistor to switch the relay would be the method.

But im still lost as to the actual exact question.

I was getting me terminology mixed up, I meant to say IGBT (which contain mosfets). Good article here:

http://www.ixys.com/Documents/AppNotes/IXYS_IGBT_Basic_I.pdf

Bruthal · 22-02-2013 8:53pm

leeomurchu wrote: »

Sorry I'm not being very clear about this it's a 20A nc 230v coil contactor.

basically I need a 5dc relay that'll switch a 230V load (which will be the coil of the contactor)

the issue I'm having is that if the 230V contactor is switching a high load the relaay I have works fine 100mA but if the contactor load is low say 5-10A the relay will not switch.

The load being switched by the contactor wont have any bearing on the current its coil takes to switch it on.

So where is the contactor load level coming into it?

DublinDilbert · 22-02-2013 8:56pm

Here's one that looks good too

http://radionics.rs-online.com/web/p/solid-state-relays/7360873/

Also make sure you have a suppressed contactor coil, or fit a reversed biased diode across the coil contacts...

Bruthal · 22-02-2013 9:00pm

Its a 230v ac contactor being switched though.

The problem is the 5v relay is not switching the contactor with the contactor is at certain loads.

So the problem is finding out what is the setup exactly.

I think finding out exactly what is switching the 5v relay coil itself is the main question.

The contactor coil current will be the same no matter what load the contactor is switching through its contacts, therefor the 5v relay contacts will have the same loading on them.

DublinDilbert · 22-02-2013 9:06pm

Bruthal wrote: »

Its a 230v ac contactor being switched though.

I don't know the full set up, but if its a 230V contactor, I'd just use an AC SSR to control it from 5Vdc control signal.

Bruthal · 22-02-2013 9:09pm

DublinDilbert wrote: »

They are some times called a "solid state relay", which use opto couplers & mosfets to basically form a simple relay. Many soild state relays are designed to switch AC loads only, but ones are made to switch DC.

I had to do something similar, i needed to control a 24V contactor from a national instruments digital output (eg 5V out). I got a din rail mount solid state relay from RS.

Something like this would probably be the job for you:-
http://radionics.rs-online.com/web/p/solid-state-relays/7401321/

But RS literally have 100's of them

Doing a bit of transistor-relay switching stuff myself lately. Another tractor project before christmas there, all microcontroller setup this time, switching the car relays via transistors to drive it.

Low signal 5vdc relay non pcb

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