First a quick recap of today’s brew. In a word – textbook. It went very well, perhaps even flawless, with only two small problems which weren’t brewing related at all.
The first issue was I couldn’t cool to 70 degrees F, which is my typical target… the groundwater temperature here is still too warm, and I didn’t have any ice (or ambition) to use my recirculating pump / ice bath method. Fortunately it is a belgian style using WLP540, so I cooled it to 80 deg with the tap water, pitched my yeast, and immediately put it in the basement and threw some thin wet towels around the demijohn. The evaporation is bringing the temperature down – I’m down to 75 degrees after just 3 hours. If fermentation kicks in a little warm, at least this is a belgian beer and the yeast can most likely handle running a few degrees higher… I just can’t use the “let it ride” methodology I typically do when I pitch at 65-70 degrees and may need to intervene if the fermentation heat drives the temp to high.
The second thing occured before the infusion water was even in the kettle warming up… namely an unfortunately collision between an Xacto blade and the pointer finger on my left hand. OK… basically I tried cutting some tubing before the crust was out of my eyes and the first sips of coffee were surging thru my veins, and I sliced open my finger. Its pretty nasty, I won’t lie – but I don’t think stiches are required and it stopped bleeding after about 10 minutes. Occasionally I’ll do something too strenuous with that finger and it’ll split open again and bleed a bit or throb telling me to knock it off – but I think I’ll be OK in a day or two.
OK… on to the stir plate. I did some tests while brewing today with the circuit using both the TIP31 transistor and the 2N4401. The 2N4401 works great, and probably would even for extended amounts of time, but at low stirplate speeds it gets pretty hot – like 110-115 deg F range. Now this is just with ambient convection currents to cool the transistor, so chances are good that when it is shoved in a box with a ridiculously oversized fan, the forced convection will cool it to tolerable levels. The other aspect is that it only is really hot at low speeds – at medium to high speeds, it is <95 degrees. The TIP31 works just fine as well, and I could slap a TO-220 heat sink on it if I wanted to, but it seems unncessary and it appears to drop the speed of the fan down a bit too. I think for my initial build I’ll stick with the 2N4401 since I’ve got a drawer full of them if the component fails.
The PCB circuit is going to be pretty small – under 2″ x 2″, if I use the draft design I worked up. I included an extra ground pad down near component Q1 (the 2N4401) that’ll allow me to put the TIP31 in there if need be – and it’ll also orient the transistor package such that the heat sink will stick off the board and allow for better cooling. I’m going to sit on it for a few days and see if anything strikes me before I actually expose and etch the traces.
On another note, the hops I grew this year are all for sale at Freshops.com – Zeus, Magnum and Nugget. Donna and I did a little math based on our yield this year, and we basically grew $120 worth of hops based on the Freshops prices. This of course assumes that the ones I grew are of the same quality as the Freshops ones (which remains to be seen), but still – go me for nabbing some Zeus rhizomes! Looks like they may be the “Columbus” replacement variety of choice in the short term…