Recent content by carlisle_bob

If you dig into all of the math, it turns out that you need a several KW (yes kilowatts) of semiconductors in a stack (yes multiple layers) to get this sort of job done. You also need a heatsink on the other side of the stack that will get down to about a 10C rise at a KW or so of power. They...

Hi If you stick with the DIP package parts PIC's (starting from the 18F series) have a lot of similarity in their pinouts. There are a couple of power pins that show up on the later parts that aren't on the early ones. If you go with the 28 pin DIP package, it exists in a *lot* of PIC...

Hi The "cost is no object" approach would be to use multiple external PID's and select which one is active with the PIC. Sort of the 1960's approach. You could set each one to it's control point ahead of time and just let the PIC run a schedule. No, I'm not going to send you my credit...

Hi Yes indeed, this is a bit picky. Feel free to ignore the input. I'd set your boil point sensor to something like 208 F to start the timer. It's "close enough", and takes care of things like slop in the calibration. Bob

Hi Sounds good! Now you need to figure out what you are going to use for connectors. D-Sub's are popular, but you need strange cutouts for them. They also aren't great on current rating. CPC from TE / used to be AMP are a relatively cheap alternative. They get you up to some major current...

Hi I realize that for some reason you have a need to attack any post I make anywhere on the Forum, no matter what the topic. Why - who knows. I've bought millions of thermistors and used them in temperature control applications. They do indeed vary far more than you believe. An RTD or a...

Hi Oddly enough, I've actually been in the sort of places that "knock off" this sort of stuff. The way they do it is pretty simple. They all get a specific batch of parts from a single source. Each of them build up the parts and sell them. That way they don't have to worry about complicated...

Hi The gotcha is figuring out *exactly* which part is indeed the replacement. There are literally dozens of "OEM replacements" on eBay. Unless you get lucky, the beta is going to be wrong. Even buying them with the same beta number is a bit of a guess. Different manufacturers come up with...

Hi That's what many power supplies do when they are running into to big a load. Either your blower is pulling more than 5 amps or the power supply is putting out less than it's rated for. Bob

Hi Last time we had this conversation, you came on pretty strongly that "calibration is nonsense" .... Some more of the story: Beta is an exponent in the fit equation. A small change tolerance wise in the beta results in a fairly large change in the resistance versus temperature slope...

Hi The dsPIC33's from Microchip are a pretty good intermediate between the Arduino's and full blown ARM. You are up to a 140 MHz clock, even at low voltage. That helps get stuff done. You also have at least two I2C's and a pair of UARTS on almost all of the chips. Of course the main...

Hi Ok, here goes again on the probes: 1) You need one that's 10K ohms nominal resistance at 25C. That's pretty easy, just be sure you don't get ones that are 10K at 20C. 2) You need one that's an NTC (negative temperature coefficient) not PTC (positive temperature coefficient). Again...

Hi 23" without anything connected to them. Figure another half inch to allow hoses to get in and out easily. There is some variation between manufacturers, so it's best to measure the actual kegs you have if you are really trying to squeeze things in. Bob

Hi It's the normal floor standing burner setup minus the legs that hold it up off the floor. Sorry - no picture. Bob

Hi Setting up a gun for each gauge is the right way to go. That way you aren't fiddling with stuff all the time. It's a *lot* easier to see the "30 GA" marking sticker on a gun than that little print on the bits... My Raspbery Pi came in to day and I'm wondering how best to use it. Yes...