Hey there – I'm working on a project where I would like to flicker a piece of 15*20cm PDLC film on/off really quickly, varying between 50Hz and 160Hz. My plan is to strip off the plug from the PDLC and connect it to a Solid State Relay, which will be hooked up to a 220V → 48-65V switchable transformer connected to UK mains power. The SSR's DC control input terminals will then be connected to an Arduino, which will manipulate the PDLC film on/off quickly.
I think the most important factor is the SSR that I am using; I'm looking at either ordering the Schneider SSL1A12JDR Harmony SSR (280Vac/2A max load, 0.07 A minimum load, 3-12V control voltage, 24-280Vac load voltage) or Sensata / Crydom ASO242R SSR (280Vrms/2A max load, 0.06 A minimum load, 4-12V control voltage, 12-280Vrms load voltage).
Both are "Instantaneous" according to RS Electronics, but I'm not 100% confident as the Crydom SSR refers to "random turnon" and the Schneider site refers to "random voltage switching", which doesn't make total sense to me. Is it possible to be both random and instantaneous?
Link to the Schneider SSR: https://uk.rs-online.com/web/p/solid-state-relays/9221821
Link to the Crydom SSR: https://uk.rs-online.com/web/p/solid-state-relays/7385507
That said, I think either should fit the bill, but it's worth mentioning that I'm making an educating guess over the minimum load because I don't know what the PDLC actually draws. Annoyingly, all that I know about the PDLC is that it has a "Type A 200V plug", and the seller hasn't replied to my request for additional information. I expect it to be relatively low though, especially given how small the PDLC film sheet is.
Link to the PDLC: 15x20cm Smart Film Starter Electrochromic PDLC Switchable Glass ODM OEM Welcome! | eBay
I've never worked directly with mains power before, so keen to make sure I don't accidentally blow myself (or anybody else) up. Does anyone have any views/thoughts on whether this approach seems sensible. Thank you!
It should be safe as long as you insulate connections or enclose the relay so nobody can touch the line voltage.
Anything higher than 50V is considered "dangerous" by most regulating agencies so you should take care with the transformer output too.
That's what you want. It WILL turn-on instantly.
...There are SSRs that wait to AC zero-crossing to switch-on (to minimize electrical noise on the power line). But for the best "flicker" you probably want to switch "randomly" (uncorrelated to the AC frequency).
However there is another issue - Most AC SSRs are built-around TRIACs and a TRIAC won't switch OFF until current falls to zero (at the next zero crossing). If you switch-on just-after a zero crossing (which you won't know) the relay will remain on for the whole half-cycle (100ms at 50Hz).
And you are "flickering" AC so when you turn it on for part of a cycle you don't know what part of the cycle you are "catching" and you won't know the voltage. That could be good for "random flickering effect", but it's it's bad if you want a controlled strobe effect. A prefect-controlled strobe effect is going to be impossible when switching 50Hz AC.
Are you sure that's a transformer (AC output)?
A DC power supply probably wouldn't switch instantly off, and usually not instantly on either. If it's DC you can better control the DC than the AC.
If it's DC and you want to switch the DC, make sure you get an SSR rated to switch DC. (AC SSRs don't work with DC because the TRAIC latches-on.)
You could use a MOSFET driver/switch circuit but a pre-made SSR is more foolproof.
It would be "cleaner" to get an AC socket (I've used an electrical box like what's inside the wall) or you can cut-up an extension cord, using both ends with the relay & electronics in the middle.
