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Forum Index : Microcontroller and PC projects : MM/DM Caravan Power Monitor
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panky Guru  Joined: 02/10/2012 Location: AustraliaPosts: 1101 |
Hi all, I have been working for some time on a hardware/software package to provide a Caravan Power Monitoring system. I have included my work to date below and am happy if Hugh would like to add it into the library. It is a work in progress and I'm happy to take any questions/suggestions. Regards, Doug. 2012-10-12_123415_CVanBM.zip ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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| shoebuckle Senior Member  Joined: 21/01/2012 Location: AustraliaPosts: 189 |
Doug, It will be in the next MMLib update. Cheers & thanks, Hugh |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6098 |
An interesting project. I am in the early stages of something similar. Instead of shunts, I am using hall effect devices - ASC758 I went for these modules on ebay: "50A/100A/150A/200A Bi/Uni AC/DC Current Sensor Module (arduino compatible)" Being isolated makes them easier to connect to the Maximite. I also use LM324 op amps so I can run a single supply rather than split. Inputs at this stage are: DC amps X 2 AC amps Indoor, outdoor and fridge temperature (LM335Z) Electric brake monitor - DC amps on each axle and if they are not the same - panic. (I went down Macquarie Pass south of Sydney with one axle not working and it was not nice!) I might also have a GPS so I can align the satellite dish. I want to use the AC current to control load shedding - turn the hot water of when the BOSS starts the hair dryer. Jim VK7JH MMedit MMBasic Help |
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| panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1101 |
For anyone interested, I have ordered a 9" VGA LCD display so when I get home in a couple of weeks, I will start work on a pixel level graph of voltages and currents. I had a look at the single supply op-amps but came to the conclusion (just me, not necessarily fact) that because I wanted to work down to to the millivolt level for low currents, I needed the ability to zero the offset and calibrate so I could read voltages within a few millivolts above zero. I also had a problem of how to read both input current and load current independently and where to reference both readings hence I took (for me) the easy way out and used the battery neg as the reference zero thus with a shunt on the input current negative path and a shunt on the output negative path, I could read a negative millivolt value for input current and a positive millivolt reading for the output current. As well as amplifying the millivolt levels to voltage levels, I scaled the input to be within the 3.3V levels of the MM ( in fact, 50A thru the shunt gave 50Mv and after amplifying, 2.5V at the MM input pin. Battery charge or discharge then became the difference between the two. I haven't looked at hall effect devices for this project - how are they for reading down to 1 Amp DC currents? Interesting thought about the AC monitoring - might have a go at integrating that as well. As I'm getting toward memory limits, I am going to see how Jim's short strings go - my only concern is timing in the interrupt routines. Regards, Doug. ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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graynomad Senior Member Joined: 21/07/2010 Location: AustraliaPosts: 122 |
The ASC712 has a 5A version, presumably it works OK down around the 1A level. Rob Gray, AKA the Graynomad, www.robgray.com |
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| panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1101 |
Thanks Rob, I might try to have a play with Hall Effect when I get a chance. What I needed when I started was to read currents from 0 to 50 amps with a resolution to .1A and an accuracy of around +- half an amp. So for me, the simple solution was the current shunt and dc amp config - not saying it's the best but easiest for me (I also liked the challenge of playing with the op amps for dc amplification ;-) ) Cheers, Doug. ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6098 |
Doug, I have the 50A bidirectional ACS758 which outputs 40mV per amp. zero amps is at 50% supply voltage. Regarding saving program memory, Rather than go to the overhead of my "short string" routines, you could fit 5 minutes of readings into one string. That would make the LogFileArray$ a lot smaller without too much work. You can save a few more string variables by reusing (without making the code unreadable) The 3 string variables debug_mode$, getdate$, and gettime$ appear to get used once and the result saved as a numeric variable. You could use one string variable for the answer and reuse it. This code: MinTurnover$="59" Do While MinTurnover$ <> "00" MinTurnover$=Mid$(Time$,7,2) Loop could be changed to: MinTurnover=0 Do While MinTurnover <> 0 MinTurnover=val(Mid$(Time$,7,2)) Loop to save another string. The next release of MMEdit will have a command to strip out comments which means you can develop code with comments and deploy to the Maximite with the leaner code. The next release also has a working VT100 screen which I have been testing with your code (amongst others). Jim VK7JH MMedit MMBasic Help |
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| panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1101 |
Jim, That's really helpfull - much appreciated. You are certainly right in that I have not optimised my variable usage and I should be able to prune a lot of rubbish and/or redundancy. My initial work was just getting the sucker to work!!! I was particularly interested in the elegance of your short strings idea so couldn't help myself in wanting to have a play with that ;-) I like the idea of the REM strip function - I was thinking of some way of creating a program to strip REM's from a program myself so I look forward to the new version of MMEdit, a really, REALLY neat program. Within my limited coding capabilities or as a tester, anything I can do to assist with MMEdit development - just ask. Cheers, Doug. ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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James_From_Canb Senior Member Joined: 19/06/2011 Location: AustraliaPosts: 265 |
There should be a StripComments program written in MMBasic in the library. I wrote one while I was developing the LCD.LIB and ran out of memory. I can't confirm the name because I'm out of town for a couple of days. James My mind is aglow with whirling, transient nodes of thought careening through a cosmic vapor of invention. Hedley Lamarr, Blazing Saddles (1974) |
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| shoebuckle Senior Member Joined: 21/01/2012 Location: AustraliaPosts: 189 |
James, I can't see your StripComments programs in mmlib and I don't remember having ever come across it. Why not send it to mmlib@geoffg.net and I will add it. Cheers, Hugh |
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| panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1101 |
Hi All, Have finally gone live with the VGA version of my Caravan Battery Monitor program. Seems to go OK so I have taken the liberty of a 1.00 version. Any/all comments appreciated. Hugh, feel free to put up in the library and delete previous. For all interested, please note the comments/caveats in the readme file. Regards, Doug. 2013-01-10_013139_CVBM10.zip ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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