PCB mountable SSR with at least 4A/250V AC - Page 1
Forum section: electronics / projects

author: davorin
author_rank: Unknown
timestamp: February 26, 2025, 01:42:52 pm
content: Good afternoonLong time ago Sharp did those nice SSRs even with zero-cross detection.....but nowadays it is hard to find PCB solderable SSRs who can handle 4A@250V AC...only found this one from IXYS:Problem is that I have six quartz heating tubes where three of those require 650W@230V AC....so this model is with 3A close to the edge with around 2.7A.So size is the biggest concern here...

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: February 26, 2025, 01:46:25 pm
content: Does it have to be a SSR? I usually use a triac with opto-isolator to trigger it. And optos with zero cross are common.

author: davorin
author_rank: Unknown
timestamp: February 26, 2025, 01:53:45 pm
content: Well that might be the other solution....as the original design uses MOC3022 and BTA308X.....I'm just lazy (o;The MOC3043M might be a good choice with 0-crossing....guess a heatsink is in order as well as in the original design here:Hmm..what is better for quartz heater tubes as load? 3 or 4 quadrant Triacs?I assume 3-quadrant as no snubber circuit is required....so I vote for the ST T1235T-8I

author: PCB.Wiz
author_rank: Super Contributor
timestamp: February 27, 2025, 12:01:31 am
content: Quote from: davorin on February 26, 2025, 01:42:52 pmDigikey show quite a few 5-50A through hole AC SSR, the higher current ones bolt-onto heatsinks.Of course, the prices are premium. Maybe the CPC1998J ?An opto triac + Triac may be cheaper.Keep in mind if you have 6 of these on, they will heat each other, so size may not be as small as you would like.

author: langwadt
author_rank: Super Contributor
timestamp: February 27, 2025, 12:24:45 am
content: https://www.mouser.dk/c/?marcom=186910001not cheap though

author: floobydust
author_rank: Super Contributor
timestamp: February 27, 2025, 12:40:48 am
content: OP you're looking for a magical unicorn part.Triac SSR ballpark heat generation is 1W per amp. So you need 4W dissipation which is not realistic in a small SIP plastic package unless you are comfy with it at 80°C per the Crydom datasheet. Sure it's rated 5A but way hot...4A is more in the league of a TO-220 with heatsink, if you want it low cost. Also depends on your ambient temps.

author: Sniper1
author_rank: Regular Contributor
timestamp: February 28, 2025, 08:47:07 pm
content: Quote from: floobydust on February 27, 2025, 12:40:48 amWell theoretically you could make one with discrete back to back MOSFET and some drive circuitry. BUT as a module i am not sure if something like this even exists .

author: floobydust
author_rank: Super Contributor
timestamp: February 28, 2025, 10:15:29 pm
content: At high voltages power mosfets have high RDS(on)and I think their heat and gate-drive hassles makes them unattractive. Triacs are cheap and tough.

author: Sniper1
author_rank: Regular Contributor
timestamp: March 01, 2025, 10:20:58 am
content: Quote from: floobydust on February 28, 2025, 10:15:29 pmYea that is why i said theoretically , then again in some cases where it is truly needed it could be done with discrete parts.Tho very few cases pop in mind, like having slightly better efficiency , if you need just a little more in order to meet a target or some case where u have no way of cooling stuff