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273 posts

Ultimate Geek
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# 210326 22-Mar-2017 16:15
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I thought I would post this here for others to think about building.

 

I needed a 12 volt trigger relay to get power linked to two processors.

 

Neither processor had 12v trigger inputs.

 

So after reading elsewhere about simply solid state relay (SSR) devices I built my own.

 

If you look at the picture, it is housed in a box about the size of a kid's shoe box.

 

The power lead (from wall power socket) comes in from the left and the red HOT line is cut in two. It then connects to pin 1 of the relay and the other side is connected to pin 2 which then goes to the outlet side (female plug).

 

If you see the pic the 12 volt trigger is connected and LED is lit showing the power is on meaning anything plugged into the power socket is now supplied with power.

 

Turn off the 12v supply and everything is turned off.

 

I have connected this to my 12v trigger on my receiver and it works perfectly turning on/off my processors when the receiver turns on/off.

 

The relay cost $10 and the box I had lying around along with the power cord. 

 

If you need a 12 volt replay triggers to get other devices working on/off it's a simple build. The SSR relay is a Fotek SSR 25DA.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


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3344 posts

Uber Geek
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Vocus

  # 1745930 22-Mar-2017 16:20
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Is that a metal chassis?  Are you using a grommet where the cable comes in?  Where's the extra insulation in case the hot wire comes loose/breaks?  Why isn't the chassis earthed?

 

I see this will work just fine, but it doesn't seem terribly safe :/




273 posts

Ultimate Geek
+1 received by user: 74


  # 1745931 22-Mar-2017 16:23
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Yes it is. The entire cable run does not touch the chassis at any point. It is lifted off the chassis by the red/blue plastic pieces and grommets at entry/exit.

 

You can see another build here using the same approach, but a far tidier version than mine here:

 

http://forums.stevehoffman.tv/threads/diy-12v-trigger-outlet-to-automatically-power-on-off-devices.313534/

 

 


 
 
 
 


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Vocus

  # 1745952 22-Mar-2017 16:41
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oh, that box doesn't get a lid?




273 posts

Ultimate Geek
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  # 1745954 22-Mar-2017 16:45
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Yes fully enclosed.

 

The box serves as a heat sink. I have yet to try this with large current as it won't be used in my system for that. So one concern may be location.

 

But that is over to the end user. One thing I do like is with this SSR there are no clips on plugs everything is screwed tight.

 

I urge anyone interested to read the Steve Hoffman Forum construction thread. It is where mine started.

 

 

 

 

 

 

 

 


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Vocus

  # 1745956 22-Mar-2017 16:55
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There are a couple of features with the build you referenced which make it, IMO, a lot safer.

 

1. Crimped/insulated connectors vs screw terminal - little chance of the live AC cord fraying, coming loose at the connection point

 

2. Earthed chassis vs not - the chassis is earthed by virtue of the socket assembly, this means if something DOES short out internally, it should blow a fuse and not kill someone

 

IMO your build is potentially dangerous.  If that live wire comes loose from the relay and livens up the case, you are in for a world of hurt.




273 posts

Ultimate Geek
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  # 1745959 22-Mar-2017 16:58
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Thanks. I'll take seriously your tips and see what I need to do!

 

 

 

 




273 posts

Ultimate Geek
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  # 1745991 22-Mar-2017 18:25
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Ubergeeks - can you please confirm this is the correct and recommended way you would earth this relay?

 

 

 


 
 
 
 


838 posts

Ultimate Geek
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  # 1746036 22-Mar-2017 20:08
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NO:

 

The earth MUST NOT be on a mounting screw. It Must be on its own post.

 

John





I know enough to be dangerous




273 posts

Ultimate Geek
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  # 1746255 23-Mar-2017 09:26
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Thanks for the guidance here.

 

Attached is a modified graphic showing my install with a proposed earth lead connected to the chassis BOLTED and then going out to the device connecting plug.

 

If this is safe and correct can you confirm, with thanks.

 


588 posts

Ultimate Geek
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  # 1746256 23-Mar-2017 09:29
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Thought that SSR looked familiar. I remember BigClive did a teardown of these (and the results weren't great): https://youtu.be/DxEhxjvifyY

 

 




273 posts

Ultimate Geek
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  # 1746260 23-Mar-2017 09:35
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Yes I did some checking too and there are some fakes out there.

 

But given the low amp draw of my units attached I think these will work OK.

 

If only my new amp had included a power output as the previous one did, all this would not have bee needed!

 

 

 

 

 

 


588 posts

Ultimate Geek
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  # 1746280 23-Mar-2017 10:02
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You should still assume this thing will spontaneously combust at some point and/or spew AC240V across your 12v leads.

 

Take some precautions:

 

     

  1. Only ever connect to a RCDBO protected outlet.
  2. Add a fused power inlet to the box: https://www.pbtech.co.nz/product/ADPGEN4004/Generic-PP4004-IEC-Male-Chassis-Power-Plug-with-Fu
  3. Use approved fuses (1+1 spare): https://www.pbtech.co.nz/product/CARLTF7785/Littelfuse-00012512-Cartridge-Fuse-T-63A-5-x-20mm
  4. Add a 3-pin wall outlet or C13 outlet: https://www.jaycar.co.nz/single-240v-gpo/p/PS4040
  5. Ground the inlet directly to the chassis & outlet (or a proper busbar): https://www.pbtech.co.nz/product/CHSGEN9014665/Brass-Bus-Bar-Terminal-Block-24-Way
  6. Keep the SSR centred in the enclosure clear of cabling and apply thermal compound between the SSR and chassis. 
  7. Might as well add a DC or stereo jack for the trigger input: https://www.jaycar.co.nz/3-5mm-enclosed-socket/p/PS0122

 

*Adding the inlet / outlets gives you additional accessible means of safe disconnection; avoids the need for grommets etc and reduces the amount of combustible material (double insulated cable) inside your enclosure.




273 posts

Ultimate Geek
+1 received by user: 74


  # 1746282 23-Mar-2017 10:05
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Thanks assuming there is a safer mechanical relay out there - which are recommended?


588 posts

Ultimate Geek
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  # 1746288 23-Mar-2017 10:12
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Maxcat:

 

Thanks assuming there is a safer mechanical relay out there - which are recommended?

 

 

Any approved (CE, VDE..) AC240V+ component from a reputable source i.e. http://nz.rs-online.com/web/

 

All of the above would still apply.


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Uber Geek
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  # 1747358 25-Mar-2017 01:30

Jaycar SY4040 relay. Rated at 30A 240V so no need to bother with fuses as you will only be using it with a 10A supply. You would still need to earth the metal box. But if building again from scratch, you could then use a plastic box. So no need to earth anything, as no exposed metal.






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