Cheap SSR
Bean
Posts: 8,129
If anyone is looking for a cheap SSR to control AC stuff I just happen to find this one on digikey. It's rated at 8A @ 125VAC and it's only $4.13 ! I assume the price is so low because it is NOT RoHS compliant and doesn't have a zero-crossing detector.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=425-1223-5-ND
Bean.
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http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=425-1223-5-ND
Bean.
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I know what I know, don't confuse me with the facts...
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www.hittconsulting.com
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Comments
Right now I am seeking 20A but I will keep this one in mind for possible inclusion in future projects.
- Sparks
It is rated @· 25 amp· 24 to· 280 Volts AC
This maybe what you are looking for here is the link
·http://web2.automationdirect.com/adc/Shopping/Catalog/Relays_-z-_Timers/Solid-State_Relays/AD-SSR225-AC
This has a built in heat sink
Sparks
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··Thanks for any·
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Sam
Post Edited (sam_sam_sam) : 9/21/2007 8:56:20 PM GMT
I read the Datasheet and it says it does have a zero-cross detector. Part : S108T01
Can I ask you some questions :-
1. If a SSR does not have zero-cross detector, will it cause more EMI emissions during switching?
Will this EMI cause the SX Microcontroller to restart?
2. How much inductive load can such SSRs handle? Fluorescent lights with coil ballasts? 100% inductive loads?
3. Can such SSRs handle near 100% capacitive loads? Will the high initial surge current caused by the capacitor kill the SSR?
I am also looking for lower cost SSRs but for 240v AC.
Keep looking.
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What you posted is closer to what I probably need. The price of the SSR Bean posted is much closer to what I would rather pay!
Thanks for the link. It looks like it can handle the task.
- Sparks
Yes without a zero-cross detector the SSR can turn ON at any time during the AC cycle. When they have a zero-cross detector they can only turn ON at the zero crossing. SSRs that have triac output can only turn OFF at the zero crossing (this is almost all of them). So if the SSR happens to turn on at the peak of the AC voltage, BIG FAST SPIKE of energy. Sometimes you can use an external zero cross detector and have the controller turn them on at the proper time.
2 and 3 I guess would depends on what SSR you choose. I really have no idea.
Bean.
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www.hittconsulting.com
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I have seen a lot of triac dimmer circuits where the signal to the gate is triggered from MT2 ( Main Terminal 2) through a resistor.
On Off triac circuits that use a optocoupled triac driver will also source its trigger from MT2 to power the gate.
In this kind circuit, problems can occur in highly inductive loads like a classic fluorescent lamp with coil ballasts.
This is b'cos the current that lags behind the voltage caused by the inductive load can make the triac switch off when it's not supposed to.
My question now is, can SSRs like the Crydom D2W203F handle highly inductive or capacitive loads.
If yes, how does it do it?
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www.fd.com.my
www.mercedes.com.my
My experience with triacs and SSRs is limited. So I do not know the direct answer to your question. I do know that snubber circuits are often included for the very reasons you state when triacs are used to switch inductive loads. The Crydom D2W203F data sheet indicates that it has a built in snubber. To know if it is enough you would need to determine if your load is likely to exceed the Min. Off-State dv/dt rating of the SSR.
Hopefully someone else will provide a more informative answer.
- Sparks