Heated Stir Plate Build and STC1000 mod. Pic Heavy.

[Buster]

Having built a stir plate a while back I decided to go down the road of yeast propagation to save on buying Vials and Smack Packs of yeast instead of just using my Stir Plate for starters. Seeing as it took up space in my brew fridge I decided to modify my Stir Plate by adding a heat source to it so it could be left out of it. I started by sourcing a12v /10watt heat pad for around £5.00 from FleaBay seeing as my Stir Plate was 12v powered. The next problem was the Temp Controller that I had which was a 240v STC 1000 Elitech Model. I decided to convert it to 12v so it would run along with everything else in the Stir Plate. Below is a few pics of the Mods and Build along with some pics showing how it held temperature at 22c with an air temp of 15c, the Temp Controller Probe is held on the back of the Flask underneath some bubblewrap and the other Temp Probe is in the Liquid just to show the Temp in Comparison. I hope its all usefull to anyone. Please note that if you are unfamiliar with electronics involving soldering and 240v this may not be for you, be carefull.

Inside the STC 1000

Desoldered Transformer

Bridging Wire

Adding the 12v Heat Pad

Working Unit Showing Temps

[ManseMasher]

Cracking job! My stir plate is a cigar box....yours puts it to shame!

[Buster]

Cracking job! My stir plate is a cigar box....yours puts it to shame!

Thank you for the comment . Its quite handy if you dont have a Brew Fridge or a room in your house that stays around 20c day and night as some yeast make take a good 72 hrs to get a good yield.

[ManseMasher]

I'm a big fan of 'diy brewing'. I'm in the middle of trying to drill a hole through a pressure cooker to convert it to a hop back. Broken 3 drill bits so far, lost a bit of claret in the process! I'm sure it will be worth it in the end.....

[Rad]

So all it takes to convert stc to 12 volts is to take the "big cube" out . Once my brewpi is assembled and integrated with the fridge, I'll have a spare stc to play with

Any idea how much load can that transformer take? I wonder if it could be reused to power stc and the heat plate.

[Buster]

So all it takes to convert stc to 12 volts is to take the "big cube" out . Once my brewpi is assembled and integrated with the fridge, I'll have a spare stc to play with

Any idea how much load can that transformer take? I wonder if it could be reused to power stc and the heat plate.

Its a 10vac 1.35amp so it would need a bridge rectifier after it to give you DC voltage for the Heat Pad. Also it depends on what wattage your Heat Pad was, I run the whole thing with a 12v 2amp DC external Power Supply.

[Buster]

Here is a simple 12v DC Regulated circuit for you.

This is not my design.

12V-regulated-power-supply-circuit-diagram.png (9.46 KiB) Viewed 3320 times

[weetabixface]

that looks like an asetek fan controller you have there, how low does it go in terms of output ?

I have a zalman lying around doing nothing but the 5V lowest output on the zalman is still a very vigorous stirring, if the asetek is lower then that might be the answer, or knocking up something with an LM317

W

[Kev888]

Its useful to see the STC's 240v to 12v conversion for anyone who had a 240v version and wanted to convert it. FWIW though, there is a transformer-less version of the STC-1000 available that is natively 12v (the ones I had were labelled AC but work on DC too, I guess they just leave the rectifier there).

[Buster]

that looks like an asetek fan controller you have there, how low does it go in terms of output ?

I have a zalman lying around doing nothing but the 5V lowest output on the zalman is still a very vigorous stirring, if the asetek is lower then that might be the answer, or knocking up something with an LM317

W

I have since took that controller out as it was useless and have now replaced it with my own build similar to the one I posted above. It now works from 0v to flat out 12v with a very linear response. I would recommend the build tbh. If I have time later this evening I will build another one to show how I made it .

[weetabixface]

thanks, I will knock something up with an LM317 then

W

[jayjt29]

Very nice indeed! I've just built a stir plate yesterday and now want to upgrade it!

Jay

[Buster]

I have just finished knocking up a quick and dirty speed controller using the LM317 and took pics on the way, I will post them all tomorrow.

[weetabixface]

ah, me too

played around with a bench top power supply to get a feeling for the voltage range that would spin the fan without the stirrer bar going daft, 3.3-3.8V worked well, to get the fan to spin need to hit 3.5V but can then turn down the wick and it is happy at lower voltage resulting in a very gentle stir

then using this calculator to sort out a voltage divider for the LM317 to get that range

W