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Topic: Solid State Relay (Read 744 times) previous topic - next topic

kajmaya

I need to replace a switch something like a relay, opto-coupler, or SSR.

Basically here is what I have:



I would like to use an SSR if at all possible. If so what SSR would I need?  I would rather not use a relay because of its Mechanical life. I also don't know if an opto-coupler would work in this situation, nor do I know how to set it up for AC.

Any help would be appreciated.

Thanks

Keven

fungus

Most SSRs won't do 8V AC. They're designed for mains voltage, 8V is too low.

There's two diodes in your diagram so are you sure it's AC?

If the current is only going one way you can use a MOSFET.
Advanced Arduino

DVDdoug

Since you have the diodes, you can use a DC solid state relay.  If you are running off the Arduino, get one that can be controlled by 5V (that's very common for SSRs).    Do you know what the wattage or amperage rating for the lamp?  The output-voltage shouldn't be an issue.  Most SSRs will be rated for 50V or more. 

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I would rather not use a relay because of its Mechanical life.
Yes, solid state relays essentially last forever if you don't electrically overload them.   

But, mechanical relays can last a long-long time.   And they tend to be more "electrically rugged", so they don't always die the first time you put excessive voltage or current through them.  Cars usually have lots of relays, but the only time I've had a failure is horn relay that failed on an older car several years ago.   Many years ago, I added a relay to my home furnace so that I could switch-on the whole-house fan without turning-on the heat.   It still works and I don't even think about the relay.   Where I work, we build a device with 16 relays and I don't remember the last time a customer returned one for repair (where a relay was the cause of the failure.)

kajmaya

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fungus... There's two diodes in your diagram so are you sure it's AC?


Yes it is AC half wave. This is a snippet of the larger schematic a weather vane. The switches are reed (worked by a magnet) There is a wire that comes off the anode side of the diode (not shown). The lamp only lights on one side of the waveform (plus side) when the switch is closed. It has a matching circuit (duplicate this one) with the diodes flipped the other way. If the switch was closed on the matching circuit its lamp would light on the opposite waveform (minus side).  If both switches are closed both lamps are on. The setup from the 8vac to the wire at anode side of the diode is duped 3 more times in parallel. The diodes at ground just make sure all 4 circuits are in sink. (basically 4 wires operate 8 lamp)

I would just like to avoid the relay approach as it would be opening an closing many times per hour. (I want to simulate the wind direction using the Arduino)

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DVDdoug... Do you know what the wattage or amperage rating for the lamp


I don't know. I believe the lights might be around 6v could be 3 (ill have to stick a meter on them). I can't remember the resistor rating. But hay 8 volt source two diodes and a lamp.
I just found this relay:
http://www.alliedelec.com/images/products/datasheets/bm/NTE_ELECTRONICS/70011947.pdf
Im glad to know there is an SSR on there somewhere.

fungus


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fungus... There's two diodes in your diagram so are you sure it's AC?



Yes it is AC half wave.
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Also known as DC (there's no negative voltage).

Just use a "logic level" MOSFET (look for one with an 'L' in the name) between the circuit and GND.
Advanced Arduino

kajmaya


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