solid state relay

Hi all,

Thanks in advance for any help with the following:

I purchased some SSR's, R23MA to be precise. I'm trying to hook them up with an arduino. I tried with an AC load, that worked. Now with a DC load, somehow it turns on (a test LED), but not off after turning off the arduino voltage. I read something about zero crossings as well, but I'm no electronics guru, so I can't really tell whether that's of any importance.

Thanks again for any advice on this.

Best,

l.

zoodio: Hi all,

Thanks in advance for any help with the following:

I purchased some SSR's, R23MA to be precise. I'm trying to hook them up with an arduino. I tried with an AC load, that worked. Now with a DC load, somehow it turns on (a test LED), but not off after turning off the arduino voltage. I read something about zero crossings as well, but I'm no electronics guru, so I can't really tell whether that's of any importance.

Thanks again for any advice on this.

Best,

l.

Yes most standard SSRs work only for switching AC voltages on and off. Those SSRs that are based on thyristor (SCRs or Triacs) type switching devices can only turn off a voltage when the current passes through zero like with a AC current when it passed through a zero crossing of it's waveform, so if used in a DC circuit they may turn on but would never be able to turn the circuit off unless the conduction path was externally opened up.

There are so called DC SSRs that work (I think only on DC circuits) but them using the term SSR often creates confusion on their proper use and application. Always research a device's datasheet to see what you are actually working with and it's capabilities.

Lefty

thanks so much for your swift reply.

i see, it's about what i expected, but like i said, i'm not a super electronics guru, so i thought i'd wanna double check. so theoretically, switching audio signals (line or speaker level) should work, no?

again: thanks!

l.

zoodio: thanks so much for your swift reply.

i see, it's about what i expected, but like i said, i'm not a super electronics guru, so i thought i'd wanna double check. so theoretically, switching audio signals (line or speaker level) should work, no?

again: thanks!

l.

You know I really don't know if that is possible. In theory audio is AC voltage but it can be so such low voltage/current levels and a typical audio signal source is rarely just a pure sinewave so who knows if it would work for you or not. You can certainly try and see as there is no chance for damage to anything. However to be clear standard SSRs are designed to switch only 50/60 Hz AC power circuits on and off.

Lefty

SSRs will not switch audio signals at line level at all, and if you try to switch audio with them at speaker level, there will be a lot of distortion.

To switch audio at line level, use small signal mosfets, or CD4066 CMOS switches, or reed relays. To switch at speaker level, use a mechanical relay.

thank you guru :-)

ok, so i'll use them for the ac power supply stuff we gotta switch, and the leftover mechanical ones for speakers etc... hope we have enough to match all.

thanks both for your insights, learning faster.

basically a SSR latches on when you switch it - it only switches off when the mains cycle passes zero

this means it can only be switched on once every mains cycle

so the switching speed is limited by the mains frequency

i suggest you use a mosfet if you want to switch DC

or switch ac and convert it to DC

how much current do you need to switch ? and how fast ?

hi, thanks for your replies.

in the datasheet i see the following under ‘absolute maximum ratings’ and ‘output’:

RMS ON-state current: IT(rms) 150 mA
peak one cycle surge current: Isurge 1.2 A

does this mean that the load current has to be between these values? i sometimes have a hard time interpreting the numbers in datasheets right…

because of the $$$$ we decided to try SSR’s instead of all-purpose mechanical relays, we need to switch speaker level audio, dc current and ac current. it seems to have problems even if we try to switch ac current after a transformer, probably because the load is so little that it doesn’t switch (?)… anyhow, will just let them switch the 230V power and use the mechanical ones we still have for other switching and see if we manage.

thanks again!

can you explain what your project is doing ?

you really wanna know? haha... we have large number of opened cassette decks and other obsolete technology hanging in the space, with loops going between them. every pair of decks has one recorder and one player, mics in the space pick up the sound for some 'interactivity', if you will. and feedback of course. some decks can be turned on and off by just powering it on and off, since the tape head will stay on the tape when it's a purely mechanic mechanism. so we will switch whole pairs then. some stand-alone decks, as we call them, have just the control switches hacked, so a single tape will record, play, stop, rewind and fast forward. here we have to switch the functions with single relays. can be done better probably, but we also like the sound of switching relays...

to not have electrocuted visitors, we hang the transformers out of reach and extend the low voltage ac coming from them to the decks at eye level and lower, to show them the beauty of circuitry.

does that answer your question? :-)

so you have a vintage recording studio ?

can you record to hard drive instead ;)

there are some dc - dc ssrs here

http://www.power-io.com/products/hdd.htm

4.25 v 10ma will switch on 1 v will switch off

i dont know if these devices latch on or not - ie you have to switch it off

you may be able to rig up something simple so 5v pwm is set to 1v when off ( not sure how to do this )