HLT Temp Control, with PICs

[FlippinMental]

Hi there.

Thought the group may be interested in my take on using a PID to control the HLT.

I set it out like this cos i don't know any better. Here's what the various bits do.
two lines in, two lines out.
top outer switch each line out between constant or PID control.
top inner switch signal from PID to ssr's on/off.
bottom left rocker selects what side pid is powered, center is off.
fuze protects PID.
bottom right is the pt100 connection.
bottom outer are the two eurosockets that the elements plug in to.
the two led's indicate power in.

i think this setup provides a little bit of flexibility allowing each side to be individually controlled. what d'ya think, am i going to blow myself up hope not.

regards, FM

[edit1now]

Looks good. Have you got any ventilation in your box? I can see the big heatsinks on the SSRs - will it all get a bit warm in there?

[Hogarth]

Nice neat job, FM.

[FlippinMental]

Looks good. Have you got any ventilation in your box? I can see the big heatsinks on the SSRs - will it all get a bit warm in there?

Good point, I was contemplating cutting in some vents if things got too hot, but when testing the setup to my surprise there was no increased heat on the box at all? the ssr's are 25 amp each (kettle elements pull 10 amps), so not having to work too hard, but nonetheless I was still expecting a little warmth, but the box felt cool to the touch

one question regarding the PID that i'm hoping someone can help with, is it necessary to calibrate when using a pt100 probe? and if so how is this achieve?. a comparison between an electronic thermometer and the PID had them reading reasonably within a degree C of each other. using iced water gave confusing results, the pid wouldn't present a minus temp even with ice sat on the probe.

[edit1now]

As long as the PID reads the same as your favourite thermometer at some sensible temperature, like mashing at 67C, then I wouldn't worry about freezing because you don't need it. If it differs from your favourite thermometer, then you need to go in to the system settings (SET 0089 on mine), find the temperature display adjustment (PsB on mine) and take it down or up by the difference between your thermometer and the PID.

[stu-le-brew]

very impressive piece of work, wonder where did you get the case for the project ?

[FlippinMental]

As long as the PID reads the same as your favourite thermometer at some sensible temperature, like mashing at 67C, then I wouldn't worry about freezing because you don't need it. If it differs from your favourite thermometer, then you need to go in to the system settings (SET 0089 on mine), find the temperature display adjustment (PsB on mine) and take it down or up by the difference between your thermometer and the PID.

Thanks for that edit1. Mine has a config setting SET 0089, and PSb, equating to Input off-set, but no associated note in the blurb. So it simply i.e. reading 1 degree high, notch down the reading -1, or am I being the simple one... again?

very impressive piece of work, wonder where did you get the case for the project ?

That would be from maplins, stu.

FM

[mysterio]

Very nice work! Wish I knew how to do wiring like that.

[FlippinMental]

Thanks mystrerio, the wiring just looks complicated. if it were I'd not have been able to do it.

FM

[adm]

Looks great! Much nicer wiring than mine which I did in solid 2.5mm copper, all hard soldered for everything as it was all I had in at the time.....looks like something out of a first world war battleship inside. It was a right cnut to solder though as the copper just wicked the heat away. Yours is much more elegant!

You'll be going for a timer next, I can almost predict it......(nice cheap mechanical ones on eBay from Baxi boilers BTW...). That way you can just set it up the night before and stroll down to perfectly hot liquor whenever you're ready.

[FlippinMental]

You'll be going for a timer next, I can almost predict it......(nice cheap mechanical ones on eBay from Baxi boilers BTW...). That way you can just set it up the night before and stroll down to perfectly hot liquor whenever you're ready.

Brilliant idea! as luck would have it adm, the missus gets me draping xmas lights all over the house that are controlled by mechanical timers. hlt control would be a much more dignified use for them

[WishboneBrewery]

the missus gets me draping xmas lights all over the house that are controlled by mechanical timers

Poor you!! Thats my second worst nightmare this week, the other being a US tour of country singer places like the other halfs parents just came back from!

[FlippinMental]

Looks good. Have you got any ventilation in your box? I can see the big heatsinks on the SSRs - will it all get a bit warm in there?

a quick follow up note on heat generation... when on for a hour the unit did get warm when constantly powering the elements. just warm enough to convince me to cut vents in both side panels and above each heat sink. don't think at this time that forced ventilation is required. if it becomes an issue I'll post another quick dit.

FM

[edit1now]

So it simply i.e. reading 1 degree high, notch down the reading -1, or am I being the simple one... again?

No, you're not being simple, just try it, and adjust as necessary.

[mentaldental]

a quick follow up note on heat generation... when on for a hour the unit did get warm when constantly powering the elements. just warm enough to convince me to cut vents in both side panels and above each heat sink. don't think at this time that forced ventilation is required. if it becomes an issue I'll post another quick dit.

FM

I use a PID to control my HLT as well. The SSR is mounted on an aluminium box without heatsink (although the box itself does some work in that respect). The box gets quite warm (but not hot) when the HLT is initially heating the liquor up to temperature but once it is near strike temp the box stays cool. I will probably add a heatsink just to be sure but heat generation from the SSR is not such a problem as you might expect. My SSRs are somewhat overrated for the loading they actually experience, and I guess this might have something to do with it.

By the way, where did you get those heatsinks?