Magura said:How can I make a solid state relay? Is there more to it than a big mosfet and an opto coupler?
Cheers
Magura
1mA or 100A? 1v or 1000V
from big mosfet i could assume...something
What do you want to do with your SSR?
Just want to do it by yourself or is there some reason not to use standard products from companies like cp-clare or phoenix?
And yes, thats about what is needed in real basic case. real-word working circuits may have plenty of other components also depending on application...
Re triacs
My experience with triacs is that they are not always as simple as they seem. This is especially the case where they are in-circuit with and iductive load, i.e. such as a transformer. If the tranformer is a big toroid the problems may get worse. Take a look at AN308 from ST Micro.
I spent 2 or 3 months of my spare time trying to build an acceptably quiet soft-start circiut using triacs. I tried a simple approach then tried the approach in AN308. I got it to work quite well as long as I didn't care about the noise. By noise I mean a audible buzz if you hold your ear close to the unit as well as noise that gets into the amplifier ans appears at the loudspeakers. From three feet away you wouldn't notice it but it annoyed me knowing it was there.
In the course of this I discovered a couple of other factors that I never though much about previously. First if there is another triac anywhere in the same house circuit, such as in a light dimmer, the "blips" it leaves in the AC even when fully in on-state may be enough to upset the timing of your triac. DC offset in the house AC can contribute to this as well. If this were not enough ubiquitious SMPSs in things like PC or televisions do really wierd stuff to the current (rather than just voltage) wave form of your AC and can also upset your triac. ( I read a short article, in EDN?, that commented that the presense of SMPSs even the surrounding houses and apartments can bugger up your AC.) Note the implication that some days you may experience little or no problems but on other days you may -- all depending on what appliances you and your neighbors are running.
In short, I beive that with more effort I could have eventually found a way to quiet down the triac. A noisy triac and sometimes induce hum from the transformers as well and because of ther proximity it can be difficult to tell which is the source. Nonetheless, it was becomming appearent that to accomplish this I would be adding complexity to the point that the original attraction of simplicity was lost. Finally, I just packed it in and used an R10 series relay.
Still, take a look at AN308 and give it a try. You may well be more ept than I was.
My experience with triacs is that they are not always as simple as they seem. This is especially the case where they are in-circuit with and iductive load, i.e. such as a transformer. If the tranformer is a big toroid the problems may get worse. Take a look at AN308 from ST Micro.
I spent 2 or 3 months of my spare time trying to build an acceptably quiet soft-start circiut using triacs. I tried a simple approach then tried the approach in AN308. I got it to work quite well as long as I didn't care about the noise. By noise I mean a audible buzz if you hold your ear close to the unit as well as noise that gets into the amplifier ans appears at the loudspeakers. From three feet away you wouldn't notice it but it annoyed me knowing it was there.
In the course of this I discovered a couple of other factors that I never though much about previously. First if there is another triac anywhere in the same house circuit, such as in a light dimmer, the "blips" it leaves in the AC even when fully in on-state may be enough to upset the timing of your triac. DC offset in the house AC can contribute to this as well. If this were not enough ubiquitious SMPSs in things like PC or televisions do really wierd stuff to the current (rather than just voltage) wave form of your AC and can also upset your triac. ( I read a short article, in EDN?, that commented that the presense of SMPSs even the surrounding houses and apartments can bugger up your AC.) Note the implication that some days you may experience little or no problems but on other days you may -- all depending on what appliances you and your neighbors are running.
In short, I beive that with more effort I could have eventually found a way to quiet down the triac. A noisy triac and sometimes induce hum from the transformers as well and because of ther proximity it can be difficult to tell which is the source. Nonetheless, it was becomming appearent that to accomplish this I would be adding complexity to the point that the original attraction of simplicity was lost. Finally, I just packed it in and used an R10 series relay.
Still, take a look at AN308 and give it a try. You may well be more ept than I was.
I would say a bit more than one or two per day. The one I use is rated for a minimum of 5,000,000 operations at 18,000 per day. That is less than a year at that rate but if I can restrain my enthusiam to only a meager 1,000 operations per day, it will need replacement after 13 years. I can live with that.
18,000 per day is once ~ every 5 seconds. I think that would be inconsistent with normal audio listening. Even in a protection circuit. Still I agree if that were what you need a SS relay makes more sense.
18,000 per day is once ~ every 5 seconds. I think that would be inconsistent with normal audio listening. Even in a protection circuit. Still I agree if that were what you need a SS relay makes more sense.
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