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MoominPapa

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Everything posted by MoominPapa

  1. I don't know. I just tried to find a cross-section diagram of one to see if they do have a stack of junctions and failed miserably. MP.
  2. Possibly, if I could have determined which contact was the problem. Given that the chassis is riveted aluminium there's dissimilar metal problems and corrosion to take into account too, adding a wire was the first thing I tried and it worked so I didn't explore other options. MP. I've not. If they're 20v open circuit there must be quite a stack on junctions in there, individual thermocouple junctions are in the mV/Celsius range. MP.
  3. We had similar problems with a Spinflo grill/oven combo, which is basically the same stuff and made by the same people. The problem turned out to be that the design relied of the cooker chassis to provide the return current path from the thermocouple to the gas valve. As the thing aged, the connections between the thermocouple and the chassis, the valve and the chassis, and the various bits of the chassis, increased in resistance. The voltage generated by the thermocouple is tiny, and it doesn't take much resistance to decrease the current below that needed to hold in the solenoid valve. The fix was to run a wire from the mounting nut of the thermocouple to a mounting screw of the valve, which worked instantly. Be careful to use either uninsulated wire or wire with high temperature insulation or be very sure that the wire in securely held away from any components which will get hot. You don't want a PVC insulation fire. After making this fix I happened to look at a new unit in the chandlers, and the same fix had been implemented in manufacture, so if your cooker is relatively recent, it may already have the earth return in place. In that case all you can do to be make sure the connections are clean and tight. MP.
  4. I moved to Three from EE a couple of years back, on cost grounds. I'm seriously considering moving back. It's clear that Three have way oversold their network capacity in many places, and though it's possible to get a decent signal, either the radio bandwidth or the backhaul capacity is congested and bandwidth and round-trip-times are not good. One trick I have used with success in quite a few places it to force the router to use 3G rather than 4G. Three has/had an excellent 3G network (the clue is in the name) - much better than EEs which was never much cop. It's clearly mostly still in place, and because most devices prefer a 4G connection when both are available, the 3G network is less loaded and often gives better transfer speeds. MP.
  5. Foxton is only steep because the builders made it so. The summit clings to the contour until the last minute when there's nowhere else to go and then drops steeply. There's a lovely gentle slope from the as built line for at least the last half mile where the canal could have descended more slowly. MP.
  6. Blowing an absolute hooley in Hurleston. MP.
  7. The Jericho VMs are full of ankle-breaking collapse holes. I've reported them before, and work has been done, but it never seems to last. MP.
  8. Check the link. Modified moving average doesn't require storing a fixed number of samples and the influence of old samples falls out of the result automatically at a rate determined by the n parameter and the number as samples per second being fed into the calculation. I sample as fast as possible and pick n so that it takes a second or so to slew to a new reading. Pick n as a power of two, as the algorithm divides by it, and be aware that the accumulator's maximum value is the maximum sample value multiplied by n, so you might need to worry about overflow. No server running permanently, the information ends up on my laptop. Each record has a 32-bit serial number, and the EEPROM in the Arduino can store the last 8192 records in EEPROM. The program on the laptop knows the serial number of the last record already in the file on disk, asks the Arduino what the serial number of the most recent record is, then requests all the records between those two serials and adds them to the end of the file. I log a record every five minutes, so as long as I plug the laptop in once a month, I have a complete copy of the log. For the first couple of years, I just plugged the USB from the Arduino into the laptop. Now I have a serial line from the Arduino connected to a serial port on my internet router, so the laptop can talk to the Arduino via the internet. The router still doesn't store the data, it's just a way for the laptop to talk the same protocol as it does via USB, but remotely. MP.
  9. The main problem to solve is finding where the log data starts and ends. The obvious solution is to keep that in a dedicated location in the EEPROM, but then that location gets written every time the log is updated, while all the other blocks are written every n updates, where n is the size of the EEPROM in log entries. I have designed a self-describing log format in the past, where you just write the new block at each log, and a scan through the whole thing at startup is enough to tell you where the valid data starts and ends. The current code uses a two-step approach. The metadata is stored in the 1k on-chip EEPROM and the logs in the i2c EEPROM. On chip EEPROM has a single location which points to the actual metatdata . The metadata includes an update count and when it has been updated 65356 times, the initial pointer is updated and the metadata moves along to new unworn locations in EEPROM. That extends the theoretical lifetime from months to decades. Getting the data out over the serial line is easier and less code than writing a filesystem on an SdCard, I think. MP.
  10. For oversampling, I used modified moving average, which is really easy to calculate. The article bellow has the details. https://www.baldengineer.com/measure-pwm-current.html I tend to make n a power of two to optimise the code. For logging I used an 8 pin i2c EEPROM which is arguably easier to wire up than an SD card, and certainly easier to read and write using an Ardunino. You do have to arrange your own wear-levelling though (don't have a single root block that gets written on every logging event and will wear out first.) The Ardunio MCU has 1k of EEPROM built in which is sufficient for quite a bit of logging if you optimise record size and logging frequency. MP.
  11. I know it's not what you are asking, but here are plenty of cases where the canal has had to accommodate "improvement" of existing roads at a later date, to the detriment of the canal. For example, the A51 road bridge between Barbridge and Calverley which adds a nasty blind bend to the canal that almost certainly wasn't there before. Ditto the road bridge just south of Saltersford tunnel. Newer roads are better: there seems to have been an era in the 50s and 60s where the bridge had to be built because closing the canal was too hard but nobody really believed that it would last, so the minimum possible to keep the canal navigable was built. MP.
  12. This post cannot be displayed because it is in a forum which requires at least 10 posts to view.
  13. That sounds similar to my first (failed) attempt at hardware, and would definitely have been better if I'd been able to make it work. My point is that the simple-minded solution with Arduino analog inputs works well enough and is simple to do, as long as you understand a few gotchas. MP
  14. On subject of Arduino cell voltage monitoring, my system uses the simple and obvious method of measuring the voltage WRT ground at each cell junction using potential dividers. I divide the voltage by 6 and use the built-in 2.56v band-gap analog reference in the microcontroller. That gives a range of 0 to 15.36 volts and a resolution of 15mV at the least-significant bit for the 10 bit ADCs in the Arduino. By oversampling I get values which are accurate (or at least consistent) to within about 25mV in practise. Individual cell voltages are obtained by subtraction, in the obvious way. This all works fine, but I'd say the resolution is only just good enough. If I was starting again I'd use a microcontroller with a 12-bit ADC. Beware of the specs on the microcontroller for the maximum voltage at an input pin. This is normally given as Vcc plus a small margin. Since I'm dividing the voltage by six, and using 5v Vcc, all is fine as long as the Arduino is powered up. If it's off and Vcc is zero the input pins are still connected to the voltage dividers and the maximum voltage above Vcc spec is wildly violated. You can probably rely on the chip's built-in protection diodes if the potential divider resistors are high enough (and you want them to be high to avoid parasitic discharge) but to be sure I added discrete 1N4148s from each cell voltage input pin to Vcc. They are normally reverse biased, so have no effect, but when the Arduino is off and Vcc is low they conduct and limit the pin voltage to Vcc+0.6, which is safe. I bought 0.1% resistors for the voltage dividers, but they still need calibration factors to be added in software to get readings which agree with my multimeter. (The multimeter ain't necessarily that accurate, but it can be assumed to have consistent errors, so I trimmed the calibration so the cell voltage read by the Arduino agreed with the multimeter for each cell.) MP.
  15. Please could you define what "wokeness" is, in your opinion. MP.
  16. Mine certainly doesn't say Lucas anywhere on it. MP.
  17. I've just fitted an A127 marked 75A that I bought as a spare/standby from Ebay about five years ago. It does indeed produce 75A (actually 80A when cold). MP.
  18. I'm not the oven user on this boat, so I can't give a definitive answer, but it does certainly make bread OK, and had cooked a complete Christmas dinner (slowly) on more than one occasion. The main problem we've had in the past with the oven is that the burner is very close to flame-lift. Even a marginally over-pressure regulator is enough to hit the problem as we discovered when the thing was installed. An new reg fixed it, but anything even very slightly over 37 mbar and half the burner blows itself out. This may cause you problems in your attempts in increase gas flow. MP.
  19. If I'd done that, and admitted it here, people would be predicting my imminent, fiery, death. I'll bear it in mind for future enhancement, but given how flimsy the thing is, I think I'd be wary of increasing the heat output too much. MP.
  20. We have a spinflo midi prima gas grill and oven on board. These are fairly cheap and nasty things, built down to a price (and weight) for the caravan market, but it's done OK as our main cooker for a decade or so. Slowly enough that we didn't notice it for a long time, the performance of the grill has been getting worse, and it finally got to a point where something had to be done. I expected that the problem was partial blockage, either of the jet,or the mixing tube, or both. The reality was different. Having got access to the back of the device, I removed the jet and supply pipe. This is mounted on a bracket and shoots the jet of gas into the end of the long tube that runs up the middle of the grill and has holes to form the individual flames of the grill. The jet was clear, as was the tube. Then I noticed that the end of the tube was not in-line with the jet: it appeared to have dropped, so the jet was significantly closer to the top of the tube than it's centre. The tube and the expanded metal which is heated and glows red and a stainless heat shield are all mounted on two fittings which are attached to the underside of the top plate of the grill cavity. This top plate (in fact all of the cavity) is made of thin gauge aluminium and over the years it had distorted, I guess though the effects of heat and differential expansion of the steel gubbins mounted underneath it. Bending the plate to re-align the flame tube with the jet wasn't difficult; I used a pair of vice-grips on the rear fitting and just pulled. I sighted through the bracket for the jet to make sure I had the tube and jet co-axial again. Result: complete cure! Just putting this here, in case anyone has the same problem and wants the solution. Beware that this requires breaking gas joints, so only attempt it if you're competent to do that safely and test them again afterwards. MP.
  21. If it would help, I have a brand new A127 regulator marked 14V going spare in the Nantwich area. (I've just installed a new alternator which came with this regulator and I replaced it with a "tractor" voltage adjustable one.) Free to a good home. MP.
  22. I think the new pedestals refuse to return keys until everything is closed up. MP.
  23. There are at least a couple of leaks of similar volume to that on the South Stratford, not to mention the ones that flow over the towpath when the pound it high. Come to mention it, there are some of those on the South Oxford too. MP
  24. When we had an encounter with a fallen tree that demolished a front cabin window, the good people at Northwich boatyard made us temporarily weathertight pending repairs using a sticky plastic sheet that came on large rolls. It's sold for protecting carpets during decorating, apparently. Presumably like this: https://www.screwfix.com/p/no-nonsense-carpet-protection-roll-25m-x-500mm/72304 MP.
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