SSR Brands



  • I'm planning to replace my el-cheapo DA-SSR with something proper. I was looking at either a Crydom D2425 (€33.05) or a Kudom KSI240 D60 LM (€22.31). I know these are far from the same load current rating but it's what the place I get my stuff from carries. Both 25A or 60A at 240V will more than suffice to burn my place down anyway 🙂 .

    Since the Crydom is a 3rd more expensive while being quite a bit lower rated? Am I getting a better quality component with the Crydom or are they just not competitively priced?



  • The crydom D2425 is more expensive because it is not based on triacs and is instant switching.
    The "normal" ssr´s are zero crossing ssr´s which means that they can only be turned on/off when the AC voltage switches sides and crosses zero. This means that you cannot switch it at more than 50 Hz, preferably much less. For the Duet, i think 10Hz is standard.
    The instant switching are more expensive, but can be switched at something like 25.000 Hz. This reduces the power factor (i think).
    Both are more than good enough current wise since you probably won´t get more than 12A out of your fuse anyway. (depending on your fuse obviously)



  • @nitrofreak said in SSR Brands:

    The crydom D2425 is more expensive because it is not based on triacs and is instant switching.
    The "normal" ssr´s are zero crossing ssr´s which means that they can only be turned on/off when the AC voltage switches sides and crosses zero. This means that you cannot switch it at more than 50 Hz, preferably much less. For the Duet, i think 10Hz is standard.
    The instant switching are more expensive, but can be switched at something like 25.000 Hz. This reduces the power factor (i think).
    Both are more than good enough current wise since you probably won´t get more than 12A out of your fuse anyway. (depending on your fuse obviously)

    Looking a the datasheet I read that the missing suffix -10 indicates a zerocrossing SSR for the Crydom. The Crydom indeed is SCR based, but so is the 60A Kudom. I would link the datasheets, but spam filter doesn't allow them for some reason.



  • Zero cross switching is desirable because it helps prevent your lights from flickering when the heater switches on. It also helps minimize inrush current when switching non resistive loads like switching power supplies.

    You don't need to run the PWM for the bed heater at a high frequency because the bed plate is massive and takes a while to respond to power input. A few Hz is fast enough.





  • @mrehorstdmd said in SSR Brands:

    Zero cross switching is desirable because it helps prevent your lights from flickering when the heater switches on. It also helps minimize inrush current when switching non resistive loads like switching power supplies.

    You don't need to run the PWM for the bed heater at a high frequency because the bed plate is massive and takes a while to respond to power input. A few Hz is fast enough.

    I agree with you, yet both SSR's are zero cross switching so it does not really help me decide 🙃


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  • @nitrofreak said in SSR Brands:

    The "normal" ssr´s are zero crossing ssr´s which means that they can only be turned on/off when the AC voltage switches sides and crosses zero.

    True that normal triac based SSRs only switch off at zero crossing but a "zero crossing SSR" means one that also only turns on at zero crossing, so you only ever get a complete half cycle or nothing. A plain triac SSR can be turned on at any time during the cycle and therefore can give finer control but a lot more noise.

    @nitrofreak said in SSR Brands:

    This means that you cannot switch it at more than 50 Hz

    Actually 100Hz because you can control each half cycle.



  • @dc42 said in SSR Brands:

    I like the spec and price of this one https://uk.rs-online.com/web/p/products/9224996/ and this one https://uk.farnell.com/multicomp/mcksi240d25-lm-070/solid-state-relay-4vdc-32vdc-panel/dp/2770605.

    Anything you like about those two in particular? Especially above the ones I posted (which are the one listed on the wiki.


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    @nxt-1 said in SSR Brands:

    @dc42 said in SSR Brands:

    I like the spec and price of this one https://uk.rs-online.com/web/p/products/9224996/ and this one https://uk.farnell.com/multicomp/mcksi240d25-lm-070/solid-state-relay-4vdc-32vdc-panel/dp/2770605.

    Anything you like about those two in particular? Especially above the ones I posted (which are the one listed on the wiki.

    Only that they cost less, and as they are from major distributors the quality should be ok.



  • @nophead said in SSR Brands:

    True that normal triac based SSRs only switch off at zero crossing but a "zero crossing SSR" means one that also only turns on at zero crossing, so you only ever get a complete half cycle or nothing. A plain triac SSR can be turned on at any time during the cycle and therefore can give finer control but a lot more noise.
    Actually 100Hz because you can control each half cycle.

    Yes you´re right, forgive me i forgot the exact details.
    But you can´t control it at 100Hz because then the SSR would turn on every cycle effectively giving you 100% duty cycle or ontime regardless of the asked duty cycle / ontime.
    If you control it at 10Hz then you would have 10 periods to have either switched on (or off), effectively giving you 10% resolution, so you would either have 10,20,30% ontime but not in between.
    If you were to switch it at 1hz, then you would have 1% resolution.
    I hope i explained that correctly? or better, i hope i am correct.



  • @nitrofreak Yes what I mean by "you can control it at 100Hz" is that you can decide if it is to be on or off 100 times a second. In my own firmware that I wrote about 11 years ago I do exactly that and have 1 Hz PWM with 1% resolution for my heated bed.



  • As an fyi, I ended up ordering the Kudom because it was cheaper, yet seemed a reputable brand.