Electrical engineers and electricians assemble! brew controller question

[The-Engineer-That-Brews]

Good to know. That heatsink I'm using is a bridge so has a long run of fins below the SSR and shorter runs either side of it so has plenty of surface area to dissipate heat. I'm thinking that when I mount it next time I'll use some adhesive mounting material that I've used in the past to mount it.

I know the type you mean. Note that if you’re not using a fan they are designed to be mounted vertically so as to get a natural convection effect (and always with thermal grease or a mounting pad between the SSR and the heat sink):

https://www.slideserve.com/vanya/heatsink-design-a-practical-approach

 

[JockyBrewer]

Ah yes the controller does have a 'manual'mode where you set the output as a percentage, so could set to 100% upto close to the boil then either remain in manual mode and ramp back the power or switch to PID mode. But I didn't bother because I thought the SSR will be fully on until the temp approaches target temp anyway and it is not that convenient to adjust the percentage power output in the PID as you have to navigate through a menu system so just let the PID take the strain. Could give it a go next brew and see what's what.

Manual mode doesn't mean that.

Normally a PID in this application will pulse an element on and off over a set period of time, and it uses an algorithm to decide how much 'on' time is in the pulse.

e.g. if your control period is 4 seconds and the PID algorithm decides it needs 75% power then it'll turn the element on for 3 seconds (75%) and then off for the remaining 1 second.

Manual mode just bypasses the algorithm so you set the on/off percentage manually.

 

[MashBag]

Manual mode just bypasses the algorithm so you set the on/off percentage manually.

That's what I suspected. It is bypassing the algorithm, but not the SSR.

 

[hoppyscotty]

Manual mode doesn't mean that.

Normally a PID in this application will pulse an element on and off over a set period of time, and it uses an algorithm to decide how much 'on' time is in the pulse.

e.g. if your control period is 4 seconds and the PID algorithm decides it needs 75% power then it'll turn the element on for 3 seconds (75%) and then off for the remaining 1 second.

Manual mode just bypasses the algorithm so you set the on/off percentage manually.

Thanks I appreciate that...think I was getting confused about what a bypass was and thought the manual mode was what people were suggesting but didn't necessarily make sense to me because I know that it still operates the SSR just manually operated and not using the PID algorithm...thought a bypass was something more fancy and not literally just a bypass. I could easily install a switch in line to divert power either directly to the element or to the SSR.

On heat sinks...I think I much prefer the idea of forced convection. Not only is it far more efficient so enables much smaller and lighter and easier to package heat sinks, but pretty simple to set up. In my planning for v2 of my controller I was going to have the smaller rail mounted heat sinks, like I'm using now (although within an enclosed box which is a bit naughty knowing what I know now), partitioned off to create a kind of duct, with a push/pull arrangement of pc cooling fans moving air across the fins. To be honest I'm amazed my cheap Chinese SSR's have lasted so long given I've broken every rule in the 'how to install SSR' guide book. I'm not brewing for a few weeks on this system so plenty of time to make some mods.

 

[JockyBrewer]

This thread has reminded me to check what relay is in my current controllers and how warm they get. The relay is directly mounted to the metal case that acts as a heat sink, but that's it. I also use the controllers in hysteresis mode rather than PID control, so perhaps not the best if there's an SSR in there.

 

[MashBag]

I like your thinking, v2 massively overrated SSR & fannage. Much easier if it works... And you still have v3 up your sleeve for later.

Unless the cabinet is huge you only need a push fan.

Consider "always on" not temp controlled. Fans maintain temp well, they don't reduce it so well.

Ambient does change, so allow for less efficient cooling in the summer.

Just done thoughts.

Ps. what's your typical, total element full on time?

 

[hoppyscotty]

Unless the cabinet is huge you only need a push fan.

Only consider "always on " not temp controlled. Fans maintain temp well, they don't reduce it so well.

Ambient does change, so allow for less efficient cooling in the summer.

You're right I'm sure, but I love me a bit of over engineering! The components are cheap enough and often come in packets of multiple items so may as well use them and provides a bit of redundancy. Noted on temp controlled fans. Was just going to fit to the master switch via a 12v supply so they're on all the time once power is on.

I am regretting choosing a metal box for this build though...yes it's earthed to within an inch of its life, but it's so hard to make modifications to. Think I'll use this opportunity to switch out to a plastic enclosure, especially if I have better SSR cooling so no risk of overheating SSR's melting the enclosure.

 

[MashBag]

I know what you mean about metal cases. I like plastic, with a cone drill and round components