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MoominPapa

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MoominPapa last won the day on January 23 2017

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About MoominPapa

  • Birthday 12/11/1964

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  • Gender
    Male
  • Location
    CCer.

Previous Fields

  • Occupation
    Computers
  • Boat Name
    Melaleuca

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    http://

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  1. Looks great. No need for LA batteries. (I assume the Combi can function in powerpack mode without a battery in circuit, should the relay open.) How are you driving the balancing MOSFETs? I used opto-isolators to do the level translation to the gates of each MOSFET. MP.
  2. I have a computer to do it for me. MP
  3. About 13.2 after the first night, 13.05 after the second consecutive night with no charging, and about 12.9 after the third night with no charging. Ah, LiFePO4, how do I love you? Let me count the ways! MP.
  4. The fail safe mode rather depends on the problem, I feel. In the end the ability to raise an alarm and the ability of the organisation to respond to that in a timely manner is probably the best protection. When I talked to the EA control room about the Stamp End girations, they had no idea it was even happening. As for automatic protections, on the level sensing side, multiple sensors and voting would work. It's pretty easy to spatially distribute them, and even provide a fall back layer of lower precision sensors. If the control loses all knowledge of water level, the best response is probably "don't move anything and ring the alarm". Control room systems that can monitor levels and raise alarms on unusual situations would be good. A rather sticky problem on most sluices is that they use bi-directional motors: a single failure in the contactors can end up with the motor running the opposite way to what the control system commands, which is an an obvious hard-open or hard-close situation. That seems to be what happened on the Weaver last month. Redesigning hardware with two motors might help here, or at least separate and redundant position sensors so the control can stop an action if it's not what it commanded and raise an alarm. Self-test and alarms and redundancy. If it can keep an Airbus flying, it can fix this. MP.
  5. If the grass is short enough and you look along the bank, it's obvious that there are slips in the face of the bank there. The top of the dam is reinforced with steel piling above them. My guess is that the posts are for monitoring of any further movement. MP.
  6. The automatic control systems for sluice gates don't seem to be designed like the critical systems they are, with redundancy of sensors, voting, monitoring, and so on. Something similar happened on the Weaver a few weeks ago when the sluices at Vale Royal opened wide and emptied the top end of the river, stranding boats and causing excess water problems downstream. MP.
  7. In this application, that's a relevant factor. To avoid catch-22 at start up, the circuit has to be directly supplied from the batteries, (so 12-14.x volts) and the standby current matters. With a PIC you need a regulator (so parts-count win goes back to the CMOS solution) and you have the standing current of the regulator. My CMOS latching relay driver, which is rather more complex that the circuit above, pulls 10s of microamps when not actually energising the relay coils. The power supply is a simple RC filter from the battery supply.
  8. Which begs a question I've sometimes wondered. How was the toll paid? Was it strictly cash only? Most of the passing boats would belong to companies and be handled by their employees. Giving boat crews cash to pay tolls is a bit of an accounting nightmare and an invitation to have it stolen, spent on wine, women and song, or otherwise leaked. Did regular trades therefore pass on credit, with ledgers totalised at the end of the week or month and a bill sent to the company owning the boats? MP.
  9. It's amazing to me that modern microcontrollers now need no external components, except an in-circuit programming header, of course. And, stretching the definition, a programmer, and a computer to compile the program, and a program. MP.
  10. Some are, but I'm not sure it's an increasing number, from observation. MP.
  11. Yes, in theory, but there are actually two coils, one to open and one to close, so you need two RC-schmitt trigger differentators, one to make a pulse on the low-to-high transition for one coil and the other on the high-to-low transition for the other one, so it's actually simpler than that. I used R1=680Kohm and C1=0.1uF and it works fine. MP.
  12. I'm amazed that they didn't notice each other. We met a boat coming the other way in Saltersford tunnel (We were in the right: we entered right at the end of the time window, but the boats going our way before us had told the boats waiting the other way that "there's no one behind" and they'd set off early. Sadly there were three of them and one of me, so I ended up reversing out). There was no way we'd have got close enough to collide without being well aware of what was going on. MP.
  13. between 15ms and 100ms, into a 4.7 ohm coil, for the 190A unit that most people here are using. MP.
  14. 12AH per day is 10% of our typical on board power use, I'd be looking at ways to save that if I could. MP.
  15. On a 24v system, those two are an order of magnitude out. If it's 50mA then it's 1.2W but if it's 12W then it's 500mA. I'd guess the later: 50mA is the holding current for a typical 5-10A relay, not a 200A monster. MP.
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