Logic Powered Ssr Rims/herms

[mfeighan]

I currenty have a herms system with an electric hlt and an electric heat exchanger. With this setup i have to use 2 separate circuits so i dont overload the power. I dont like running power cables everywhere and am planning on moving house shortly so reworking my mains supply isnt an option.

I was thinking about upgrading my temp controllers to a couple of PIDs from auberins and just running both outputs through a logic circuit as shown:



which in theory should power off the HLT if the heat exchanger is on so only drawing 10a off one mains socket

my main worry is the output current from something like
http://australia.rs-online.com/web/search/...t&R=5190013

is only 4.2mA, is this enough to swith the SSR or will i need to have a separate psu and something like a darlington transistor array to power it.

http://australia.rs-online.com/web/search/...t&R=0858203


i was also thinking of using 3 relays 2 normaly open and one normally closed but i reckon a small circuit should be a better option. Im sure im not the only person to have done something like this before so i am open to suggestions


Mike

 

[Andyd]

I currenty have a herms system with an electric hlt and an electric heat exchanger. With this setup i have to use 2 separate circuits so i dont overload the power. I dont like running power cables everywhere and am planning on moving house shortly so reworking my mains supply isnt an option.

I was thinking about upgrading my temp controllers to a couple of PIDs from auberins and just running both outputs through a logic circuit as shown:

View attachment 47658

which in theory should power off the HLT if the heat exchanger is on so only drawing 10a off one mains socket

my main worry is the output current from something like
http://australia.rs-online.com/web/search/...t&R=5190013

is only 4.2mA, is this enough to swith the SSR or will i need to have a separate psu and something like a darlington transistor array to power it.

http://australia.rs-online.com/web/search/...t&R=0858203


i was also thinking of using 3 relays 2 normaly open and one normally closed but i reckon a small circuit should be a better option. Im sure im not the only person to have done something like this before so i am open to suggestions


Mike

G'day Mike,

Almost all SSRs you can get these days will activate on a TTL signal, so you shouldn't have a problem. Personally I use a buffer to drive the SSRs in my system, just to give me more isolation from the data signals being generated by the micro I'm using, but the logic gates you're using should provide you with sufficient load buffering to do without this.

Cheers!

Andy

 

[mfeighan]

cheers, i shall give it a whirl