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  • There are pros and cons to connecting solar panels in series vs parallel. If they act like a current source, than parallel connection may be best to get full use of the output of each panel. If they generate voltage, then series connection may be best. However, they are like a variable impedance voltage source, and maximum power extraction involves impedance matching, which usually involves MPPT or microinverters. For a simple series connection, it may help to connect a power diode across each panel, so that they will still conduct current from other panels even if one is heavily shaded or develops an open (or high impedance) condition. And I think parallel connected panels sometimes use series diodes to avoid having higher voltage panels loaded down through those with lower voltage. Some links:

    https://understandsolar.com/solar-pa...s-vs-parallel/

    https://www.electricaltechnology.org...batteries.html

    https://www.renogy.com/learn-series-and-parallel/

    https://www.mpptsolar.com/en/solar-p...-parallel.html

    https://cleversolarpower.com/shading-solar-panels/


    http://pauleschoen.com/pix/PM08_P76_P54.png
    Paul , P S Technology, Inc. and MrTibbs
    USA Maryland 21030

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    • I got around to making a chuck spider for the lathe. $40 of EBay aluminum to make 3 of them for my 6” chuck. Next I’ll figure out how to rotate pics when I upload them from my phone!.
      You may only view thumbnails in this gallery. This gallery has 3 photos.

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      • Originally posted by PStechPaul View Post
        There are pros and cons to connecting solar panels in series vs parallel. If they act like a current source, than parallel connection may be best to get full use of the output of each panel. If they generate voltage, then series connection may be best. ..........
        Hmmm, well solar panels are neither current sources nor voltage sources. They are current limited voltage sources. They will not produce more voltage than they are set up for due to number of cslls, and their current output is dependent on the light input (once leakage currents are satisfied).

        The references listed are almost but not quite useless. The information given is quite incomplete, but not actually wrong.

        If you connect a "12V" solar panel to a partially discharged 12V flooded cell battery, here is what happens: The solar panel will provide charging current, but only at the voltage the battery has at that charge rate.

        Typical battery voltage at 40% discharge (60% remaining) point might be 12.24V (2x Trojan T105 or T105RE). The voltage at the output of the solar panel will be held to some point higher than but somewhere near that voltage, depending on the exact charging current.

        But a solar panel typically puts out 17.5 to 18.5 V at full illumination and rated current. Since it is current limited, if it is rated for 5A @ 17.5V, it will put out the 5A, but will be limited to the battery voltage (approximately) and so you will be charging at 5A and, say, 13V.

        That is a rate of 5A-h per hour, or alternately, 65W. The panel is capable of producing not 65W, but actually 5A x 17.5V, or 87.5W. You are getting only 75% of the power you paid for. The rest is simply lost as heat.

        Chargers that allow higher voltages, which use SMPS type technology, but not all of which are MPPT, will hold the panel voltage to the set voltage, and preserve the power (changing high voltage and lower current to lower voltage and higher current), so the charging current would not be 5A, but somewhere closer to 6A. That is a significant increase, and gets more of the 87.5 watt capability (the rest is losses).

        Starting with a low voltage like 17.5V, the losses eat up more of the power than starting at a higher voltage, so there is an advantage to series connection vs parallel with a charger that can handle it.

        The MPPT type add a feature that searches for the most power. They will keep varying the set panel voltage and checking if the calculated power is larger or smaller under the changed condition. They adjust in the direction of larger power. So they tend to have some advantage over a straight SMPS type.

        That is not always a huge advantage.... remember the solar panel is a voltage limited current source, so it will hold voltage if the current is not exceeded, and holds current if the voltage is drawn down. So at ANY light condition that is even over the panels, there will be a certain voltage that does not vary much with current up to the rated max. So setting that voltage is quite acceptable. The MPPT type charger will extract a few percent more under conditions that are "near the edge", but not necessarily have a huge advantage ofer a set voltage type, nothing near the advantage of either one vs direct connection..

        The various references paid NO attention to the power gain in series mode, and implied that only MPPT type chargers did anything like that. Not so.

        1601 2137 5683 1002 1437

        Keep eye on ball.
        Hashim Khan

        If you look closely at a digital signal, you find out it is really analog......

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        • Finally got my birthday present installed! A three-axis DRO from China for my old Rong Fu 25 mill/drill. It does indeed reek of putting lipstick on a pig, but when you work in metric on a table with imperial lead-screws, there is a good case to be made for making life easier.

          The basic accuracy of this model of DRO is claimed to be 5 microns. The basic accuracy of this elderly machine (not to mention this elderly machinist!) is at least an order of magnitude worse than that, so the DRO should do all that I will ever need it to. The table is not Rong Fu's original, and the base which it and the column are bolted to is a heavy and very rigid welded steel box.


          Click image for larger version  Name:	DSCF0636.JPG Views:	0 Size:	2.28 MB ID:	1899842Click image for larger version  Name:	DSCF0632.JPG Views:	0 Size:	1.09 MB ID:	1899843Click image for larger version  Name:	DSCF0634.JPG Views:	0 Size:	1.21 MB ID:	1899844
          L-R: General view: Z-axis: Y-axis on brackets off left side of Y-slide. I will make a cover for the exposed side—hence the long screws with nyloc nuts.

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          L-R: X-axis on the back of the table: Nice big green figures on the readout, which swings back to the wall when not in use.

          The X and Y axes have the scale moving with transducer being fixed. The Z axis has the reverse—the transducer moves against a fixed scale.

          The box on the wall is the single-to-three-phase inverter VFD for the motor. And the ridiculous collection of white trunking on the wall is to keep the excess cabling out of mischief. The three transducers each come with three metres (10') of armoured cable, and even with over half a century of electronics in my wake I do not shorten armoured cables.

          Here's the URL for the vendor: https://www.aliexpress.com/item/1524...2ec44c4dol4qd3

          Cost was reasonable, delivery only a couple of weeks, user manual actually makes sense, but there was no information whatsoever on installation. I think that anyone with enough nous to drive a mill would be able to figure most of it out.




          Last edited by Mike Burch; 09-17-2020, 05:54 AM.

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          • Mike, looks good. I'm thinking about getting a similar setup for my recently acquired RF-40 clone. Not clear to me how you specify the required scale lengths to the seller - just "Contact" etc before hitting the 'buy it' button and tell them what you want? Some of the sellers of similar DROs on eBay give you a list from which to select. Your Z axis looks larger than need be, but maybe that's an illusion because the actual scale has to be longer than the usable part of it.
            "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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            • Cobbled together coolant feed for a non thru-coolant boring bar, jammed some 6MM nylon tubing into the end of a Loc-Line nozzle and taped it to the bar, works a charm.
              3" dia, bores 7" deep. I am turning 3 1/4" X 1/4" wall 304 tubing into 1/8" wall tubing.

              The boss ordered the wrong material then the saw operator cut it without looking closely at the worksheet (-:

              Nine 13 1/2" long parts bored from each end, this is very slow as you can imagine. Without sufficient coolant the chip will not break.

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              • Originally posted by Bented View Post
                ...
                The boss ordered the wrong material then the saw operator cut it without looking closely at the worksheet (-:

                Nine 13 1/2" long parts bored from each end, this is very slow as you can imagine. ...
                I wouldn't think that's a close call as to which is more expensive: 10' of 3-1/4" x 1/8 wall 304 or you time to make it from 1/4" wall. I think the boss was covering his ass - the additional purchase would be more obvious than your time.

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                • Originally posted by Bob Engelhardt View Post

                  I wouldn't think that's a close call as to which is more expensive: 10' of 3-1/4" x 1/8 wall 304 or you time to make it from 1/4" wall. I think the boss was covering his ass - the additional purchase would be more obvious than your time.
                  Correct, but he is the Co. owner as well, he is only covering his ass from himself (-:
                  It will take me 10 hours or so to do this part of the job. The customer specifies an ID of no less then 3.010" after machining, welding and assembly, I am boring them 3.015"+ because they meet in the center. These parts are for the food manufacturing industry, the typical order of operations is to rough machine the individual components, weld them then finish machine after welding, then electro polish to a near mirror finish.

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                  • Originally posted by mickeyf View Post
                    Mike, looks good. I'm thinking about getting a similar setup for my recently acquired RF-40 clone. Not clear to me how you specify the required scale lengths to the seller - just "Contact" etc before hitting the 'buy it' button and tell them what you want? Some of the sellers of similar DROs on eBay give you a list from which to select. Your Z axis looks larger than need be, but maybe that's an illusion because the actual scale has to be longer than the usable part of it.
                    Mickey, thanks for the kind comment.

                    I am not familiar with ebay's routine, but IIRC on Ali Express you buy first, then contact the vendor (via the website) and let him know the extent of the travel of each axis. The scale does indeed have to be considerably longer than the travel of whatever it's attached to, but that's not a problem, since the table is obviously longer than the distance it travels.

                    You should not have to choose from a list of pre-cut scales. There are plenty of vendors who will cut the scales to the exact length for you. The Z-axis scale does indeed look rather too long, but as you rightly say, that's inevitable. The quill travel on my mill is 95mm, but the scale is 235mm long, and its supplied cover with its end-caps brings that up to 260mm over all. So you need to tell the vendor the travel of each axis, and leave it up to him to cut the scales to the correct length. Just be aware that what you finally install will be a lot longer than the travel length you have specified.

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                    • Deleted - brain fart

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                      • I had to make this. Wooden nickel to the first to say why Click image for larger version

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                        • You going to blow up some fire ant mounds?
                          “I know lots of people who are educated far beyond their intelligence”

                          Lewis Grizzard

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                          • Originally posted by Dave C View Post
                            You going to blow up some fire ant mounds?
                            Close but no ceegar!

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                            • I think you saw a spider on the wall. "Purify with fire!" is the common treatment.
                              At the end of the project, there is a profound difference between spare parts and left over parts.

                              Location: SF East Bay.

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                              • To get rid of nasal hair?

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