SSR relay question

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pcmofo
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SSR relay question

Post by pcmofo » Sat Aug 07, 2010 11:01 pm

So I built a simple PCB that uses 4 AC Solid State Relays so I can turn on and off AC devices with a 5v signal from a MCU. It is a basic circuit but the SSR's I have dont seem to be working. I have some that do work though... I bought a few off of ebay new and they all seem to stay on on problem but no matter what I do they wont turn off!

The connections are really simple.... +, - 5v to trigger the relay, and an input and output... So I tried connecting just the SSR to a power supply thinking maybe my circuit was bad... This one was brand new out of the box. Connected Hot in to the SSR, then my multi meter to the out on the SSR and to the Neutral for my AC power. The multi meter shows the right AC voltage, but even when I disconnect both the 5v power and ground the power stays on. I tried every combination of Neutral/Hot, in/Out on several of the SSR's

Here is the part I have...

http://www.jameco.com/webapp/wcs/stores ... tId=176698

Any ideas if I am doing something wrong or if I just happen to have a bad lot of relays?
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pcmofo
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Re: SSR relay question

Post by pcmofo » Sat Aug 07, 2010 11:07 pm

So I was looking at the data sheet here...

http://download.siliconexpert.com/pdfs/ ... l/kb20.pdf

it has a "must turn off voltage" listed as "Max 1.0vdc" does this mean that if the voltage drops below 1v dc it should turn off? in this case... disconnecting the power should turn the ssr off...

also, input impedance is listed as 1.5k... is that the resistance of the SSR on the 5v I put into it or is that the resistance I should be using on the 5v signal going to the SSR??
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60amp_relay
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Re: SSR relay question

Post by 60amp_relay » Sun Aug 08, 2010 7:23 pm

I use the Sharp brand of the same thing. You'll need to have an actual AC load on the relay with a zero-crossing in order to measure the output. A multimeter alone won't do it - you need a 60W wall lamp or something similar that's actually drawing some power. Make sure to have a resistor on the control line - I'm not sure from your post if you already did that.

The complete circuit would be:

+5v Logic Input --> 220 Ohm resistor --> (+) Relay Input
Logic Gnd --> (-) Relay Input

120VAC Line ---> Relay Load Line #1
Relay Load Line #2 --> Wall Lamp Plug
120VAC Neutral --> Wall Lamp Plug

Then you can stick your multimeter between Relay Load Line #1 and 120VAC Neutral.

pcmofo
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Re: SSR relay question

Post by pcmofo » Mon Aug 09, 2010 8:19 am

I did not connect a load to it as I wanted to test everything first... Using another relay I am using currently on an AC chest freezer I get the expected functionality of the relay. I will try again with the load connected tonight.
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pcmofo
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Re: SSR relay question

Post by pcmofo » Wed Aug 11, 2010 8:12 am

I am happy to report you were correct. These relays do not meter unless their is a load on them, unlike the more expensive ones I was testing with. Thanks again for your help!
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