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Completed prototype circuit

Well, I banged out 95% nthe complete pump skid circuit tonight… this includes reading two temperature sensors (LM34s), controling two pump SSRs based on both level switches and the manual override “ON” switches (although I did not bother hooking the SSRs and pumps to the darlington driver IC). It also calculates the elapsed time between the low level switch dropping (signaling the grant pump turning off) and when the high level switch raises using the DS1307 data. After yesterday’s problems, I am relieved that this piece works well. Once I experimentally determine the liquid volume between these two events, I’ve got a good way to calculate a number of different (and useful) parameters, such as sparge runoff rate and estimated total sparge time.

The circuit itself is a nightmare rats nest of jumper wires. This picture certainly underscores the need for me to work on getting some PCBs made. Best would be two sided, but I’m not sure I can bite off making 2-sided PCBs right out of the gate. The exact pin specifications of the inputs and outputs are also up in the air – I have found that changing those around is essential to getting an optimized PCB design generated in Diptrace. Although I suppose I could try running the traces myself manually, I honestly doubt that I could do much better than the program’s autorouter. Best to try to orient things so the autorouter comes up with some clean lines, and then if I need to tweak it here or there I can.

The output of the circuit is also up in the air right now. I’m not sure exactly what I’m going to do with the data I’m generating since I won’t be hooking it up to a PC or main sculpture circuit anytime soon. I thought about using my 4×20 LCD screen and displaying the data on there, but it seems a little crazy to use a $50 component on something like a low-tech grant. Maybe even gratuitous…. There will certainly be room on the control panel, since it will have just two switches and a handful of LEDs – The LCD could fit very nicely above that. This screenshot simply shows the elapsed time calculation and the raw temperature reading. To calculate degF some additional manipulation is required (namely multiplying by .488), but I was planning on doing that in code instead of inside the PICAXE code. That would also allow me to do some calibration, whereas PICAXE calculations would require new program downloads to make changes.

On another (more annoying) note – I broke my 3rd Autosiphon tonight trying to disconnect the racking tubing from the plunger. I had finished moving my Octoberfest to a keg, and was cleaning it in the sink. It always f’n breaks in the same place. Looks like another $13 bucks down the tubes. These things, regardless of how careful you are, just seem to wear out after about a year of heavy use. That sucks. 😦

Categories: Tech geeks
  1. June 5, 2008 at 5:57 pm

    I think I’ve broken 3 or 4 Autosiphons too. Always at the bend of the cane is where it’ll break for me. Actually, the tip of the cane may break once or sometime twice first, but the final blow is at the bend. I actually complained to Northern Brewer (where I buy mine) and they basically just said be more careful.

    Don’t forget, I have that 1/2″ Autosiphon that you can have if you’d like to try it with your demijohns. I just didn’t think there was enough beer in a 5 gallon carboy to make it useful.

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