OT: Help with 12v solid state relay

[Steve_M]

Figured I'd ask here since there seems to be a decent knowledge base.

I picked up this 12v SSR board via eBay to control my projector screen. It's supposed to be triggered from the 12v output jack on my projector. I think it may be DOA, but I'm not sure how to fully test for that.

I've got a 12v power adapter hooked up to the DC+ and DC- connectors, which lights up the green PWR led at the top right.
I then take the 12v trigger signal from the projector and attach the negative to DC- and the positive to IN

When I power on the projector, nothing happens on the relay.

I figured I'd bypass the projector signal and test it out by jumpering DC+ to IN.

When I do this, the red LED1 in the middle right of the board flickers for a split second, but does not stay on and the relay still doesn't activate. The test is being done with the projector screen motor load attached to the relay.

Is there anything I'm missing here, or is this $5 relay from China just a bum unit?

Here's the pic from ebay:

Here's an actual picture of mine:

Higher res image: http://i.imgur.com/nNOY2H4.jpg

Higher res image: http://i.imgur.com/PlORlGu.jpg

 

[RJ Riememsnider]

Hmmm, that looks like a standard relay, not SSR.

 

[D Peart]

For a relay to stay triggered you have to maintain the IN at 12V. When you tested by hand did you do this?

How are you hooking it up to the screen? Is there a signal that controls the up/down or are you toggling power?

dave

 

[Steve_M]

Yep, I was maintaining 12v power.

The screen has a motor with up, down, hot and neutral wires. The relay switches the up and down wires across the hot. The relay is just replacing the SPDT switch that was in place.

I just ran another 12v test going straight to the relay with 12v and it triggers, so there's something up with the components getting the signal from the IN terminal to the relay.

And yes, it does appear to be a standard relay, not SSR as I can hear it working!

 

[Jarom Bodell]

If you are using the projector to trigger the relay directly, a lot of times the projector just outputs a few milliamps that's not enough current to flip and maintain the relay. Have you tried to activate the relay with a 12v battery or something like that?

 

[Brandon N]

Jarom could be correct on the input current but it sounds like you already tried to bypass that with 12v directly. What is the minimum voltage input on the relay?

http://www.hometheatershack.com/for...99-relay-120v-input-amps-use-12v-trigger.html

I know the soft starts sold here are designed for 12v trigger inputs (The guy sells parts for DIY amps).
http://connexelectronic.com/product_info.php/cPath/43/products_id/49

 

[Steve_M]

If you are using the projector to trigger the relay directly, a lot of times the projector just outputs a few milliamps that's not enough current to flip and maintain the relay. Have you tried to activate the relay with a 12v battery or something like that?

I was under the impression that with the dedicated 12v power supply going to DC+ and DC-, that the low current signal from the projector could drive the IN terminal and the dedicated 12v power supply would be activating the coil.

 

[John Jakubowski]

Your projector might not be providing enough current to actuate the relay. A SSR would require less current. What's the model of the projector?

 

[Steve_M]

It's a Sony vpl-hs50

 

[Brandon N]

Here is a DIY relay project.

http://www.avsforum.com/t/1303723/a...pro-amps-via-relay-guide-w-pics#post_19756962

 

[Brandon N]

It's a Sony vpl-hs50

http://www.avforums.com/threads/hs50-vutec-lectric-screen-via-12v-trigger-help-please.198119/

It sounds like your sony has a very week 12v trigger. From the link above "It would seem the HS50 has a very low current of 2.58ma which means the 12v drops to next to nothing"

 

[Brandon N]

http://www.electro-tech-online.com/threads/25ma-to-100ma-12v-trigger.23853/
This looks like what you need.

 

[Steve_M]

Thanks!

Looks like I'm off to the electronics store to pickup a couple of parts.

 

[Brandon N]

Thanks!

Looks like I'm off to the electronics store to pickup a couple of parts.

From some other looking I wonder if you can just use a Mosfet. I know they need to be offset voltages (vin vs gate voltage) but it seems like a cheaper ans simpler solution. You are going to need to provide 12v external power in either case.

 

[Jarom Bodell]

Typically the 12v outputs on projectors and a/v equipment only outputs like 20mA's, Sony's are among the lowest . Don't quote me, but for a small relay like you have you'll need like 200mA's. What you need is something like this: http://www.elkproducts.com/product-catalog/elk-924-sensitive-relay It triggers on 1mA.

 

[Steve_M]

From some other looking I wonder if you can just use a Mosfet. I know they need to be offset voltages (vin vs gate voltage) but it seems like a cheaper ans simpler solution. You are going to need to provide 12v external power in either case.

Interesting. Got an example of how that would work?

 

[Steve_M]

Typically the 12v outputs on projectors and a/v equipment only outputs like 20mA's, Sony's are among the lowest . Don't quote me, but for a small relay like you have you'll need like 200mA's. What you need is something like this: http://www.elkproducts.com/product-catalog/elk-924-sensitive-relay It triggers on 1mA.

That's a $20 relay. I can spend another $3 on parts and use my $5 relay.

 

[Brandon N]

That's a $20 relay. I can spend another $3 on parts and use my $5 relay.

I only know enough to be dangerous, but here is a paper about the two types of mosfets.

http://www.allaboutcircuits.com/vol_3/chpt_4/1.html

Here is more or less a blog on how to implement it. http://bildr.org/2012/03/rfp30n06le-arduino/

I don't know how you would choose the mosfet and resistors though, would have to do a lot of digging and fixing to head out for the weekend.

 

[Steve_M]

Looks you do the following:

Connect the Gnd from both the projector and external 12v supply to the Source leg of the FET
Connect the 12v+ from the projector to the Gate leg of the FET
Connect the Drain leg of the FET to the DC- on the relay
Connect the 12v+ from the external 12v supply to the DC+/Signal on the relay

If time permits, I'll pickup a FQP30N06L MOSFET tomorrow and give it a whirl.

 

[Brandon N]

Looks you do the following:

Connect the Gnd from both the projector and external 12v supply to the Source leg of the FET
Connect the 12v+ from the projector to the Gate leg of the FET
Connect the Drain leg of the FET to the DC- on the relay
Connect the 12v+ from the external 12v supply to the DC+/Signal on the relay

If time permits, I'll pickup a FQP30N06L MOSFET tomorrow and give it a whirl.

In theory you wouldn't even need the relay and could run the 12 drain directly to the 12 trigger for the motor. I'm under the assumption that it's not a direct 12v feed but a trigger.

Now I know the mosfet requires a voltage differential and I know you can use resistors as a basic voltage divider. There is also P and N type mosfets. I believe you need an N type. That said my guess is your voltage drops enough on the trigger out that it would likely work.