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Forum Index : Microcontroller and PC projects : Another really old yank newbie.
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| Paul_L Guru  Joined: 03/03/2016 Location: United StatesPosts: 769 |
Last month I wrote to Geoff for his suggestions. He suggested I come here and bother you guys because he was imminently departing for Tasmania. I'm a 76 year old retired engineer / physicist. I studied at Cornell, MIT, and Columbia Universities, worked in broadcast engineering, then at Pan Am in avionics engineering for a third of a century, then I rebuilt tugboats in Galveston, Texas. Now I hang out watching television and dreaming up unusual things to do. I live in Fishkill Plains, NY, some 75 miles north of NYC and 5 miles from both the IBM microprocessor fab and the IBM mainframe plant. I've been down under, visited Sydney, Brisbane, Darwin, Perth, Melbourne, Hobart, Ayers Rock and Katja Tjuta, the first time in 1947. After working for Pan Am I've been everywhere except Antartica and Tierra Del Fuego. Four years ago, in response to the then ridiculous price of $4 per gallon for #2 heating oil, I decided to install a geothermal heat pump in my house. I dug a pit about 60 feet x 100 feet x 7 feet deep in which I buried 6000 feet of HDPE pipe. A water and antifreeze mixture circulates in this loop picking up heat from the ground and supplying it to a 72000 Btu/hour Freon heat pump which raises the temperature and distributes heat to the house. In the summer it reverses its operation and pumps heat from the house into the ground. My initial attempts to control this monster involved a Rube Goldberg collection of a lot of mechanical thermostats and relays which was largely unmanageable. I have recently been fooling around trying to use PICAXE processors and band gap temperature sensors to control the heat pump, but there are way too many variables for even the largest PICAXE processor. I also tried using a router running a Linux derivative and lua but it is just too complicated to interface it to html code in a browser. Additionally, an heuristic approach should be applied to this control problem, which requires building a database of observations and control responses and then scanning through the data to empirically determine the best operating protocol and this is way beyond the capabilities of either the PICAXE or the router. Last month I discovered Geoff's elegant basic interpreter and MAXIMITE board design. My first impression is that a MAXIMITE will be able to handle the user control interface, and a second MAXIMITE will handle the reading of 14 band gap I2C temperature sensors, the storage of the observed data, the empirical heuristic analysis of the data, and the control of the machinery through 10 or more relays. The two MAXIMITEs should communicate via an RF serial link, possibly Bluetooth. All of the observed data points should be stored in a file on a camera card and periodically copied to a PC for additional analysis. I would like to ask you guys to review my description of the operating requirements of the mechanical system and my initial proposed architecture of the control system and let me know if I'm heading in the wrong direction. It's a big system and it will take me awhile to post a description of it. I am a little concerned about purchasing the parts needed. I know nothing about importing stuff from down under to New York or about any suppliers of the pre-programmed MAXIMITE chip and boards. I don't really want to design my own boards but I suppose that I must since I will have to control at least 10 relays. I am also concerned about making the thing look like a finished product, not like one of my clobbered together ham radio rigs from 65 years ago. Has anyone succeeded in making a MAXIMITE look a little like a laptop or tablet? Paul |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 5913 |
Welcome to the forum Paul. We like to see decent sized projects and yours should keep us entertained for a long time. Not a lot of ground source heat pumps in Australia. I believe they are more common in Europe where the air gets too cold to use but there are a few very inventive forum members so you never know. The monitoring, data acquisition and storage is easy. The control side is also easy. The bit that needs some thought is the 'empirical heuristic analysis of the data'. Another option is to use micromites for acquisition and control and a Raspberry Pi for the storage and human interface. As far as making it all look pretty, I am definitely not the one to give advice. Strip board and duct tape is more my style. There are a couple of very good examples of well presented systems and I will let others tell you about them. Jim VK7JH MMedit  MMBasic Help |
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| 5bar Newbie  Joined: 10/07/2014 Location: AustraliaPosts: 16 |
Hi Paul for the maximite, you can't go past circuitgizmos, there in the US Preprogrammed and all SMDs soldered great product and service Cheers, Lin I can count to 31 on one hand |
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CircuitGizmos Guru Joined: 08/09/2011 Location: United StatesPosts: 1421 |
Thanks, Lin! The web site is CircuitGizmos.com Micromites and Maximites! - Beginning Maximite |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
Hi Jim, I see you're from Tasmania. Is Geoff planning on visiting you while he's there? I like the looks of your editor and I will definitely give it a try. Is there a specific reason why you suggested the Raspberry Pi for the storage and human interface jobs? How good is MMBasic at formatting screens? The bit about the 'empirical heuristic analysis of the data' is a fancy way of saying that no one can make a good estimate of how much heat can be extracted from a specific piece of land on a specific day. You have to statistically analyze a lot of past performance data to even come close to a good estimate. Most geothermal heating systems need a more conventional backup system which usually involves lighting a fire somehow. The trick is to be able to anticipate when you will need to burn something well in advance of the time you actually need to light the fire. You're trying to control the temperature of a significant mass, the total mass of the water, Freon, furnishings, air, and the house itself. The time constants involved are very long, the rate of change in temperature is usually 2 or 3 degrees F per hour. The ability to anticipate environmental temperature changes and the resultant changes in heat flow out of the house is the key to controlling the system. Paul |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
Circuit Gizmos, I have been looking your website over. I will probably be using your incarnation of the color maximite. Have you got any suggestions for ways of packaging it in one box with a monitor. You know, something like the Radio Shack Model III. I told you guys I was old. Paul |
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MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
Great project! The one thing that i would do is have the microcontrollers communicate over RS-485. Much more reliable in many cases then RF or bluetooth. a uMite with an LCD would make a great GUI. You can size an LCD between 2.4" and 7" so that should offer some choices. Also keeping the programming to one style makes it a lot easier and experience can be build up quickly. Microblocks. Build with logic. |
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| CircuitGizmos Guru Joined: 08/09/2011 Location: United StatesPosts: 1421 |
Well you could gut a Model III and stuff it with Maximite + all of your other circuitry. Perhaps you could find an old unworking one. I looked on Ebay and working Model III still go for $150-$300. Makes me sad that I tossed mine 20 years ago. I also tossed a Lear dumb terminal in great condition and working that ebay has for $500. Vintage. Micromites and Maximites! - Beginning Maximite |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 8592 |
No. but they have the Micromite+ Unless you need the VGA output, can I suggest you look at the Micromite+ rather than the Maximite. The CPU is faster with more memory and more I/O. The version of Basic is more powerful with 64-bit integer as well as floating point. It has the same SD card handling as the Maximite. It directly supports 7" SSD1963 800x480 TFT displays with touch screen input which could be ideal for your application. Others may disagree but I think the MM+ completely supersedes the Colour Maximite unless you want VGA. |
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| 5bar Newbie Joined: 10/07/2014 Location: AustraliaPosts: 16 |
Gday again Paul just another idea to throw in the pot I also havr a TFT maximite with 5" touch screen tho I can't speak from experience, I have yet to assemble it quality and service are excellent a german site, but within.minutes of my email enquiry, I received a reply in excellent English My thought, have TFTMM in small tablet case for your HI wired or wireless comms to CGMM concealed somewhere advantages, TFTMM also accepts PS2 kbd, VGA and SD card and you are writing same MMbasic code Link via Geoff's site Sorry, I cant seem to post the link forum seems to have trouble with my phone browser Cheers, Lin I can count to 31 on one hand |
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jman Guru Joined: 12/06/2011 Location: New ZealandPosts: 711 |
NO DONT DO THAT rather restore it 
Jman |
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| bigfix Senior Member  Joined: 20/02/2014 Location: AustriaPosts: 124 |
The "German" TFT Maximite" uses a special HW which was originally designed by the german Magazine CT -distributed by Segor (an excellent shop in Berlin) It was soon abandoned by the german author - no useful updates... The HW to drive the display is somewhat marginal, even in the 2nd iteration There seem to be issues with blocking while waiting for touch Input No official code to fix this was ever released ? So you better go with matherp's recommendation for using the current 64Pin uMite+ with 7" SSD1963 based displays instead of sticking with a rather rare deadend version BTW I also use a groundwater based heatpump since 30+ years in Austria I also planned sophisticated control - but found it works perfectly with the most simple heating controller, only based on calculating the heating water temperature with the measured outdoor temperature - no inside sensor at all But this is a high latency massive house - it takes many hours to change anything... |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
Up in the attic I have three Model III's with 2 double sided floppies in each for a massive 1.5MB of disk storage! I also have a Model II with a separate drive bay for 4 each 8" floppies with an astounding 4MB of disk storage! The last time I checked they still worked! Paul |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
The small LCD displays won't work for me. There are too many operating parameters to display. I suspect that I would wind up with two Color MaxiMites talking to each other through some sort of Wi-Fi or Bluetooth RF link. One MM would be buried in the wall of a laundry room directly above the heat pump in the basement. It might be connected to a wall mounted VGA display permanently to display what it is doing, but it probably would not have a keyboard permanently attached. It would be reading 14 band gap temperature sensors and controlling the operation of the 84000 Btu/Hour Freon compressor, the two pumps for the outside loop, the one pump to the heat storage tank, and the seven pumps and one forced air blower on the distribution side, in a continuous loop. The Freon compressor and heat exchangers can get into trouble very quickly if maximum Freon pressures are exceeded or if the water freezes in the plate type heat exchangers. The second MM would possibly be attached to the back of a VGA monitor which would be able to roam around the house. It would talk to the stationery MM by receiving and sending concatenated strings of about 40 operational variables and settings back and forth using some sort of RF link. It would continuously display what it is doing, accept user input to change the settings variables, and it would build a data file of historical minute by minute data which would either be downloadable to a PC or would be on a removable camera card which could be removed and copied to a PC quickly. The user input of changes to the settings variables would only need a numeric keypad. It would be nice if I could use a small battery powered LCD screen but there just wouldn't be enough screen real estate to display what I would like. I'm afraid that the roaming unit will have to be supplied with AC power. Battery operation of the monitors is not critical. If the utility power fails the water pumps and Freon compressor won't be running anyway. Extreme portability is not needed. I have been trying to implement this thing using a picaxe to collect the data from the temperature sensors, a router running OpenWRT Linux and a Lua program retrieving the data from the picaxe via i2c, doing all the calculations, building an html web page, and sending the web page via a local RF network to a browser running on a laptop. I have run into the problem of continuously rebuilding the web page in the router and then getting the browser to repeatedly reload the webpage from the router. The result has been a lagging display of operating data which is not what I want. I can't adjust the limit settings effectively enough because I can't see the temperature and pressure changes quickly enough. The interpreted MMBasic running on a pic chip will be a lot slower than the Lua program running under Linux in the router, but there is not a lot of computational load involved and MMBasic should be quick enough to do the job. I am reluctant to use derivative forks of the MaxiMite which have not been continuously developed in the past. I think that the Color MM is the only device which I can safely use. I am not sure how I can implement the RF communication links. Updating data to the roaming unit doesn't have to be very frequent. One data burst per second would be sufficient. Transferring changes in the limit settings from the roaming MM to the stationary MM would only happen when the operator makes manual changes on screen. Does anyone have any suggestions about the RF transmitter/receivers and the protocols that could be used??? More details will follow soon. Paul |
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| isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689 |
I think Kon's module would be a good (and stylish) platform for this - http://www.thebackshed.com/forum/forum_posts.asp?TID=8160&PN=4&TPN=2 |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2290 |
search for "HC-12" on the forums. a pair of these modules should provde suitable range for your application, with a transparent serial link presented between your two maximites. here is a copy of the datasheet: 2016-01-14_122335_HC-12_v2.3B.pdf have you got your band gap temperature sensors already installed? what temperature ranges need to be measured? i'd be quite interested in seeing photos of the whole installation. cheers, rob :-) |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
Guenter, Thanks for your recommendations. I'm not surprised to hear that you are using a groundwater heat pump, there are a lot of such installations in Austria because the government supports them and because of the difficulty obtaining sufficient fuel oil and natural gas in Europe in general. I'm very familiar with your part of the world because I worked for Pan Am for a third of a century. What is the altitude where you live? My wife grew up south west of Klagenfurt on the slopes of Triglav in Slovenia. Using your simpler approach of controlling the heating water temperature based on the outside air temperature won't work for me. The Freon compressor I'm using is rather large for a residential installation. It draws 12000 watts running on a 240 volt line voltage with a running current of about 50 amperes and a locked rotor starting current of about 150 amperes. It is capable of pumping about 75000 Btu or 22 Kw of heat under good conditions. Under less than optimum conditions it can, in a few seconds, develop either a low suction pressure or a high discharge pressure which will cause a protection circuit internal to the compressor to shut it down before it damages itself. After this shutdown you have to manually remove mains power from the system for five minutes to allow the Freon pressures to equalize, then reapply mains power and wait for 4 minutes until a time delay circuit restarts the compressor. This safety shutdown does not trigger an alarm to let you know it has occurred, and it occurs most often in the early morning hours of very cold nights. After a few hours without pumping heat my Saint Bernard dog Brunhilda wakes me up because she is cold, so I get out of my warm bed, put on my slippers, walk 70 feet to the stairs, go down into the garage, pop the main breaker, stand there shivering for a few minutes, switch the breaker back on, stand there shivering for a few more minutes until the compressor starts, wait for it to stabilize with reasonable operating temperatures and pressures, go back to bed, spend a few minutes convincing Brunhilda to get off my bed and then try to go back to sleep. That's why I can't use the simpler control methodology which works for you. I intend to use band gap sensors to monitor the temperatures at these points: 1. the water being pumped to the ground heat exchanger, 2. the water returning from the ground heat exchanger, 3. the low pressure Freon entering the compressor, 4. the high pressure Freon leaving the compressor, 5. the water being pumped to the 120 gallon insulated heat storage tank, 6. the water returning from the storage tank. The processor will perform the following steps in a loop: 1. read all the temperature sensors, 2. decide if a compressor shut down due to low or high Freon pressure is imminent, 3. decide if ice is about to form in the input and output plate type heat exchangers, 4. shut down the Freon compressor if necessary. This shutdown will occur before the internal compressor shut down occurs. The program will then loop back and do it all again. It will restart the compressor as soon as the abnormal condition clears. It is unfair to Brunhilda to keep waking her up in the middle of the night. This processor will also handle other chores in its code loop including: 5. read inside air temperatures in 6 zones of the house, 6. control 6 distribution pumps, 7. calculate the optimum temperature of the storage tank based on outside air temperature, 8. cyle the Freon compressor and loop pumps to achieve the desired temperature, 9. calculate when to supplement the heat pump by burning natural gas under very cold conditions, 10. calculate when to switch from heating the house to cooling the house by reversing the Freon flow, 11. prepare a data file of all readings and operations for downloading to a PC for analysis and for transmission to a second processor which will handle data display and user input, 12. accept user input received from a second processor. This house probably does not have as much mass as yours. It is a typical stick build American ranch house with good insulation. It does not have poured concrete or tile walls and roof. It therefore reacts much more quickly to heat flows than your house does. That's why I included the 120 gallon (450 liter, 960 pounds, 435 Kg) insulated heat storage tank. It averages out the temperature fluctuations produced by the cycling of the Freon heat pump. A second processor will display close to real time temperature readings and the operating status of the Freon compressor, reversing valve, the water pumps, the air handler blower, and the gas boiler. One final question, since you live in Austria do you have a Saint Bernard dog? Why not? They're more fun than microprocessors! |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
Hi rob, The HC-12 looks like it will do the job. I have been using thermistor sensors and Dwyer temperature switches to control this mess for about 4 years. The sensors are tie wrapped to the outside of the pipes and then covered by insulation. I haven't purchased the band gap sensors yet, but I don't anticipate any problem in getting them to respond quickly enough. The required sensing range is from -20°F to 120°F for the air sensors, 25°F to 160°F for the water sensors, and 15°F to 200°F for the Freon sensors. All the sensors will be used in the 12 bit mode thus delivering a resolution of 0.1°C or 0.18°F. I would like to be able to measure the Freon pressures directly but I have not been able to find sensors that would be easy to apply and have the required pressure range. I would be glad to provide photos of the installation but the web site doesn't seem to want me to. When I press the image upload button above it uploads the photo file which then seems to drop into the bit bucket. Paul |
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| MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
When i read that i am glad i moved to Thailand. No more shivering. :) However now it is the opposite, sometimes it can be very warm. Sometimes when there is a disturbance in the force (i mean electricity) the aircon is forcefully stopped and does not turn on after the power comes back. So waking up sweating, then grumbling some and reach for the remote and press start. Luxury live is not easy. :) Microblocks. Build with logic. |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1328 |
We need somewhere like Goldilock's porridge - not too hot and not too cold - all the time. After the last three months of the occasional 40oC plus days here in Melbourne we're suddenly back to firing up the central heating at night again - sheesh! 
BTW Jean, where did your 300km move take you to? MicroChip and all those other very handy places close by won't be so close now. Are you still going to run your 'Maker' school? Greg |
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