diy thermometer sensitivity

Yes! I tried it and just got a slush, unable to separate out any flammable liquids. Maybe my freezer was too cold... dunno.

Ooh! Yeah, this mentions solder (tin, lead) forms a eutectic system!

Yes, it's fun =)

Michael

ICBW, but from what I've heard they have no problems with poisonous legal moonshine in New Zealand. Legalizing it means people can freely buy safe equipment with good instructions, instead of improvising.

IMO, the safety argument against letting people make it themselves is bunk. Obviously, some people would still do stupid dangerous things, but that's true with electricity (for example).

I agree with your argument and believe that the US federal gov't was obviously protecting a substantial revenue source and attempting to disingenuously justify that protection using this as an excuse.

Jon

Oddly, though, the situation in New Zealand arose because (AIUI) the customs officers asked the government to legalize private distillation because they (in customs) thought it was a waste of their time & money to try to enforce the ban!

out why it works. Is it something like this?

the

Wow.

I'm trying to remember if bit shifts work on negative numbers (for example, if IN - OUT is negative.) Should work, since the sign is the most significant bit, right? It's been too long since I took the assembly language class...

Thanks again.

Michael

...

"Farmers who used their leftover grain and corn in the form of whiskey..." oh that's pretty smart!

Thanks,

Michael

out why it works. Is it something like this?

the

IN - OUT is negative.) Should work, since the sign is the most significant bit, right? It's been too long since I took the assembly language class...

An ASR is equivalent to a signed divide. You have to make sure you have enough empty bits on the right that you don't throw away data when you do the right-shift. That usually involves always left-shifting the ADC data before you start, so there's room for the right shifts.

It may be easier, faster, and more accurate to just total 64 10 bit readings to get a 16 bit integer, and then use integer math to compare that reading to integer high/low setpoints.

Paul

Yes you have a point. Probably need to use long ints (32 bits) though because worst case, 2^10 = 1024, 1024 x 64 = 65536 which is > 32737.

Eventually I'll want something more sophisticated than simple on-off.

Y'all are familiar with this kind of stuff, right? Process Control drove me nuts in college. Maybe because our professor didn't explain it very well... ("Why not simply use a thermostat?" lol)

Thanks,

Michael

Did you say you are using Arduino? In which case you are programing in C and the language will take care of the division and sign for you

...

Yes, I am, and I know.

I just wanted to clarify if I did do a bit shift to divide by 128, would the sign be preserved if the delta happened to be negative. Apparently the answer is no...

Thanks!

Michael

sign be preserved if the delta happened to be negative. Apparently the answer is no...

Like most logical bit operations, the sign bit is just another bit.. shift that to the right, and it's gone.

Unless you use some carry operation, the upper bit should be cleared.

P.S. if you are doing multiple machine words for large values, then you need to use the carry flag to include that in the shift for the next machine word.

Jamie

that's pretty smart!

Recycling is a good thing.

...

Ah, the subtleties of AVR arithmetic shifts are a bit beyond me, I think. Thanks though.

Partial C code snapshot:

void loop() { f_reading = f_reading + 0.01 * ( analogRead( THERM_PIN ) - f_reading ); if( (++i % 2500 ) == 0 ){ Serial.print( "Average: " ); Serial.print( f_reading ); Serial.print( " Instantaneous: " ); Serial.print( analogRead( THERM_PIN ) ); Serial.print( "\n" ); ... }

Output: Average: 559.29 Instantaneous: 558 Average: 561.61 Instantaneous: 564 Average: 564.04 Instantaneous: 563 Average: 567.14 Instantaneous: 569 Average: 567.03 Instantaneous: 569 Average: 570.22 Instantaneous: 571 Average: 572.63 Instantaneous: 577 Average: 574.74 Instantaneous: 576 Average: 577.94 Instantaneous: 578 Average: 580.52 Instantaneous: 576

Outputs are very nicely averaged by 2500 iterations. Arduino can do about 5000 iterations per second, and this gives me about two data points per second.

Thanks again,

Michael

In assembler you use the ASR op-code * In "C" the result is implementation defined, check your compiler documentation.

I'd expect "avr-gcc" to get the answer right. which by reading the assember output it appears to do (inefficiently)

(* actually in assmber for a divide by 128 you stash the low bit (high bit of the low byte) move everything right by one byte, shift the low bit back in and ripple up threough the intermediate bytes (if any) and then restore the high byte using ADC and then CMP )

ethanol)

at around 78 degrees (seems like the exact number depends on which source you read 78.2? 78.3? 78.5? I give up)

First time I did mashed potatoes up here in Truckee, they came out raw. It takes a full hour. At higher altitudes, it might not be possible without a pressure cooker.

Just speculating, but if you just slowly add heat to a water-alcohol mix, won't the alcohol boil off first? It's sort of self-regulating. I don't know how pure the distillate would be.

...

After fermenting mixes of sugar, yeast and water, I noticed the liquid woul dn't start to boil until about 95 degrees C, and sometimes the collected di stillate would catch fire, but not usually. If it did catch fire, there wa s a large puddle of water remaining in my saucer. That told me there was s till a lot of water in the distillate.

In a commercial distillation column, they shove a fraction of the distillat e back into the column (the fraction is called the Reflux Ratio) to get pur er alcohol out. This also lowers the temperature inside the column.