My condensation management setup worked!

[dewbane]

I hooked it all back up and took it for a spin. Ambient is 64 F, dew point is 64 F, humidity is 99%. The heaters came on, and stayed on, and stayed on, and stayed on. Hmmm. I happen to have bought a FLIR One, so I went out there to see what was going on.

The heaters get up a little above 200 F.



After soaking for a few minutes, every surface of concern was warm enough to stave off condensation with a dew point of 64 F.


As far as I could tell, the heaters were never going to turn off, so I removed six Phillips screws and two zip screws and brought the whole shebang back in here for round three. I obviously need to get a lot more sophisticated to make this work well, which is a fact I'm balancing against how obvious it is that I need to get this back out there ASAP to get it doing its intended job.

So I kept the crude delay, but I changed it to 5 sec if none of the heaters are on, and 60 sec if either machine is heating. I reduced the target from 2.5 C above the dew point to 1.5 C above the dew point, since the old target of 1.0 C wasn't ever getting the temperature there for either machine under conditions like these. Not sure why the behavior is so different hovering around 70 F as opposed to down toward freezing. I seriously underestimated how much and how often the heaters would come into play on days like this. Nothing is actually sweating right now, but conditions are right on the razor edge, and they apparently stay there a significant proportion of the year.

Long term, I need to find that wifi board and rig this up to talk to the outside world. I can log what's going on day by day, and perhaps set it up so that I can adjust parameters like these from remote.

Longer term, I really need to put my big boy pants on and write altogether more sophisticated code. I need to find my other parts and work that out on the unit I'm building to keep my measuring tools from rusting, then port the code over to this unit once I've worked it all out. The problem is I don't really feel like fooling with any of this. I CAN code, but once the initial coolness of being able to accomplish a project like this wore off, it just became tedious work I'd rather avoid. Humbug.

Still, I better get after it. I'm going to reinstall the unit and then start thinking about something a lot more flexible than this simple delay loop. It isn't getting it done in the real world. Not this time of year anyway.

 

[AGCB97]

I'm really glad to see there's a few people that like/use microcontrollers. I see your program is written in C language. For most people older than college age learning C is a big challenge in itself. As I was trying to do so (about 6 years ago) I ran into Parallax (Propeller) microcontrollers and found that learning the programming was 10+ times easier. Not only that but a Propeller is actually 8 processors in one so up to 8 things can be happening simultaneously. I've built many gadgets and experimented with dozens of sensors. It is a great way (other than machining) to spend long winters.
Aaron

 

[dewbane]

I'm really glad to see there's a few people that like/use microcontrollers. I see your program is written in C language.

It's written in the Arduino language, which is "a set of C/C++ functions that can be called from your code."[1] I think in C++, and I basically wrote this as though it were C++.

I think C++ is a big obstacle for a lot of people, college age included. I just happened to know the language from my involvement with Rosegarden. I never heard of the Propeller platform before. I will file that information away for the next time I'm considering some microcontroller project.

 

[Boswell]

Not only that but a Propeller is actually 8 processors in one so up to 8 things can be happening simultaneously.

+1 for the Parallax Propeller. I have been using it now many years. Easy to program and FAST. Perfect for one-off embedded systems type work.

Michael, you might consider using a PID algorithm? here is the first of several lectures on it.

 

[Latinrascalrg1]

I havent read the entire thread sp if this has already been discussed please excuse my repeat.......

Has Anyone ever tried to use one of those low voltage roof and gutter deicing heat cables to keep the condensation off the machine's? They are not that expensive and can cover a large area. I just dont know if they will heat to a warm enough temperature to do the job its being asked to do.

 

[dewbane]

Michael, you might consider using a PID algorithm?

It came up back in March. The guy who was telling me about why I probably want a PID algorithm warned me that I probably need to change to solid state relays, because the PID algorithm will cycle the relays a lot. I decided not to mess with any of the hardware in this original unit, but I have solid state relays in a box with my other project bits and bobs that I lost track of in the divorce shuffle. That box is going to be to heat my measuring drawer so my mics and squares and such stop flash rusting, and I'm going to play with a PID algorithm there.

I have a wi-fi board in that pile of stuff, and I want to experiment with remote monitoring, and maybe even set it up so I can monitor and change parameters from an Android app. Not sure if I want to get into all that nonsense or not, but it should be doable. It really depends on how slow business is this winter, and how many games I end up playing. Since the wife left, I decided to buy a gigantic TV and a Playstation and a box of really good cigars.

After messing around with Dewbane all day, I feel like the FLIR One took a lot of guesswork out of the game. I tuned the algorithm to aim for 1.25 C above the dew point instead of my original 2.5 C, which was just higher than the heaters could ever achieve. I also relocated both temperature probes. I'm going to do a lot more monitoring with the FLIR camera to see under what conditions the headstock, mill spindle, etc. get above the dew point at what cost, etc. This whole thing is going to take a lot more fine tuning than I expected, but the fundamental operational concept is sound.

On a side note, let me just say I spent the day fabricating some spacers and a bracket to do some mods on my son's truck, and the more time I spend with my little "benchtop" machine shop in my bag of tricks, the more glad I am I allowed the wild hare to violate my most private inner sanctum and bought these things. Grizzly G0602 and Grizzly G0704, this Bud's for you.

 

[dewbane]

Has Anyone ever tried to use one of those low voltage roof and gutter deicing heat cables to keep the condensation off the machine's?

I haven't tried them, but if I think about it, it would be interesting to get one, plug one in, and look around with the FLIR camera to see what it's doing. They might put out enough heat, and they might not.

 

[Reddinr]

Great project! Something like this has been on my very long "do it someday" list for quite a while.

The humidity / temperature sensor has a set of accuracy ratings and a drift over time. Since you went to all the trouble, you may want to be sure your set-points have decent margin in them. Maybe 6% margin for the humidity and 1% margin for the temperature would work for that dual sensor. (I had a very brief look at the specs.) If you multiply the humidity reading by 1.06 and temperature by 1.01 before doing the dew point calculation, that will likely give you good margin. The frame temperature sensors may also want a compensation, maybe subtract 0.5C to 1.0C from the temperature readings. (I think those are the proper directions to compensate all those.)

Regarding Bob's suggestion of figuring out how much power you are using, assuming you are running all the resistors at 100W, your arduino could track and display a close enough estimate by calculating: KW-H = NumberOfResistors * 100W * SecondsOn / 3600. You would need to have the arduino track on-time. If you take KW-H and multiply that by your electric rate, you can get the cost. This works unless you lose power on your arduino. (I edited the KW-H calc. due to brain fart before).

This one may not matter in Virginia, but the code will crash with a humidity of 0% because log(0) = infinity. Easy to fix. Something like this: if humidity < 0.1 then humidity = 0.1. (Not proper syntax).

 

[Reddinr]

A couple of other thoughts. Be sure that the resistors you use are conducting the heat into the frame efficiently. Smooth surfaces are a good start. No paint or gaps between the resistors and frame would be good. If you have not done it already, you might think of getting some thermal grease or thermal pads to increase the heat flow from the resistors, otherwise you might be putting more heat than needed into the air, not the frame. If you can, take advantage of convection and put the resistors underneath vs. on top of what you are heating. Some of that residual heat will flow up past the frame and at least some of it will transfer to the frame. Steel/cast iron are not the best thermal conductor so more, smaller resistors would likely work better than a couple of big ones. I know that could be a mess of wires and in the way, but it might work even better.

AGCB97 - I use c/c++ most often for work but sometimes when I want to just bang something out quickly I use Bascom (a basic compiler/IDE). It works well with Arduino compatible hardware that seems to be everywhere for cheap. You can get a limited free version to try out.

One last safety thing. I assume you are switching the hot leg of the AC, not the Neutral? Safer to do that. A GFI feeding your heater power and a well grounded frame would be a good idea too.

Again, Great project!

 

[dewbane]

Since you went to all the trouble, you may want to be sure your set-points have decent margin in them. Maybe 6% margin for the humidity and 1% margin for the temperature would work for that dual sensor.

That's a really excellent point, and something I failed to consider.

This one may not matter in Virginia, but the code will crash with a humidity of 0% because log(0) = infinity. Easy to fix.

That's hilarious. I'll fix that gigantic gaffe next time I install new code, but I don't need to be in any hurry, because the humidity is never 0% in Virginia; not even when it's -20 F outside.

A couple of other thoughts. Be sure that the resistors you use are conducting the heat into the frame efficiently. Smooth surfaces are a good start. No paint or gaps between the resistors and frame would be good. If you have not done it already, you might think of getting some thermal grease or thermal pads to increase the heat flow from the resistors, otherwise you might be putting more heat than needed into the air, not the frame.

A good thought.

If you can, take advantage of convection and put the resistors underneath vs. on top of what you are heating.

That's the hell of it with the tables on the mill. It would be much more efficient to put the pads underneath, but there isn't anywhere sane to mount them. There isn't anywhere sane to mount them up top either, which is why they're stuck to 1/4" steel plates that merely rest on the top of the tables.

One last safety thing. I assume you are switching the hot leg of the AC, not the Neutral? Safer to do that. A GFI feeding your heater power and a well grounded frame would be a good idea too.

I haven't looked at the schematic for the black boxes I'm using. The circuit is on a GFCI breaker, for what that's worth to you.

Thanks for chiming in. Sorry I took so long to respond. Work, sleep, work, sleep, work, sleep, work, sleep, work, sleep, get drunk, sleep, work. I occasionally manage to find shop time in here. I'm definitely not dating. Being single at 46 is embarrassingly pointless. I try to overcome the sadness by spending as much time as possible solving problems with my metal eating machines. Life is really pretty good. Chick with horrendous personal hygiene issues vs. 1,000 pounds of motorized Chinese cast iron. It's a no-brainer, really.