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  1. dave9

    Black and Decker 20V DC Lithium Sweeper Circuit Board Repair - Help.

    I doubt they'd put a resistor (above 0 ohms) in series with the load. If it was a resistor, I'd get a 0 ohm of the right footprint, not take strands out of a piece of wire to guesstimate the gauge and current. Besides the wire would be unlikely to blow like a fuse, would instead melt the...
  2. dave9

    Black and Decker 20V DC Lithium Sweeper Circuit Board Repair - Help.

    You need a new camera far more than a leaf blower. :p It's probably (was) a diode, with the anode end of it on the right solder pad as pictured, or an inductor, but I could easily be wrong. Is there a letter and number next to that spot, like D3, or L2, et cetera? A better focused, top-down...
  3. dave9

    SuperCap Charging and Delivery System using Solar Panels

    It might help if we knew more about your project, for example why the need for supercapacitors and why you settled on using 3 of them and 3x 5V, 250mA solar panels, and what you seek to do with the microcontroller and voltage monitor. Regardless, the solar panels are not a constant 5V...
  4. dave9

    Power supply help

    Depends on the laptop PSU, can you link to this make/model? On some, the 3rd wire is to signal to the laptop that it has the genuine PSU plugged in instead of a some random aftermarket/etc, causing the laptop to run at reduced speed or not charge the battery if it does not get this signal, but...
  5. dave9

    Hook double horn to separate or single relay

    If the horns are unreliable, subject to shorting out, then you could run two fuses, fast blow and lower current than the one right after the battery, to each of the horns between it and the single relay, so the failure of one horn does not blow a single fuse to both. Note that in this case fuse...
  6. dave9

    How would a twisted pair effect a signal

    False. Computer control was just the beginning of more fuel efficiency. They not only did not run too lean, there were many events in which they could have run leaner, these events being refined and compensated for further over the next couple decades in firmware along with mechanical changes...
  7. dave9

    How would a twisted pair effect a signal

    The result using twisted pair wires is just coincidence. The system is set up to not have susceptibility to noise introduced from the environment, for example mainly the ignition, and can run straight non-twisted, non-shielded wire. Any noise rejection that wasn't needed, is anecdotal. That's...
  8. dave9

    Conservation CD and DVD optical medias

    Encase them in amber, then pile a mountain of silica gel on top, then put in an air-conditioned vault, underground. Fill in the access tunnel with soil and plant a tree over that. Build a tree house in the tree in a few decades. Put a machine gun turret in the tree house. Get the property...
  9. dave9

    Please advise a good substitute potentiometer

    So if you wanted alternate ideas, it seems you did not need that specific controller, either did not have that make/model originally or did and you found no place to purchase it? There are other ready made proportional brake controllers out there, which would make setting this up as safe as it...
  10. dave9

    Wrong wiring??

    ^ $12 will get you a major brand, trustworthy GFCI outlet in the US: https://www.amazon.com/Leviton-Self-Test-SmartlockPro-Non-Tamper-Resistant-Receptacle/dp/B013OVCJ3M
  11. dave9

    Wrong wiring??

    ^ Look at the pics, you can see it clearly is a metal handle right where the wire junction is! Not double insulated. It would also be good to use it on a ground fault outlet considering water or whatever liquid is involved. I've no idea what they cost in SA but in the US they can be had for...
  12. dave9

    Size and type 12 volt DC source to power 12 volt dc 5 watt pneumatic solenoid

    I see this solenoid on various other sides with multiple conflicting specs. Your best bet is to set up a test, use a regulated bench supply good for well over 500mA (@12vdc) and measure the current. However, among all the conflicting specs, 4W seems to be the highest one so you could factor...
  13. dave9

    Wrong wiring??

    Often with switches, it matters a lot to get a quality brand (and new stock, not new/old stock) if you're subjecting them to much current or on/off cycles. A generic can claim 10A (or whatever) and do that initially, but not last long. At least it's AC instead of DC. Unfortunately I know...
  14. dave9

    Wrong wiring??

    I know nothing of textile cleaning guns or mineral specimens, but... - Live should be switched to minimize risks of having the rest of the circuit and chassis life relative to earth ground, but it would work either way electrically, and given a metal case it ought to be earth grounded, not a...
  15. dave9

    Woo-Woo What is slowing my generator down?

    This could be one of those crazy free energy topics, but I'll restate the optimistic guess interpretation I have of the post. GeneratorMaker (GM) has made a crude generator. GM is spinning it with a ready made motor, giving that motor 6V to test the generator. GM gives the ready made motor 6V...
  16. dave9

    Solar charge controller question

    You'll have to look at the charge controller specs to see what it is capable of, for example the current. You may need to have its output to the heater, open a normally closed relay to disconnect the regular 48V supply to it. You may find it takes a terribly long time to heat the water with...
  17. dave9

    Is it safe to switch between NiMH and alkaline batteries?

    No bad experiences. IMO, devices designed to take AA format are made with the assumption that people will potentially be putting 1.5V alkalines in them. What I would do is buy some LSD (low self discharge) NiMH, at least one backup set, then they're ready when you need them and have a while to...
  18. dave9

    lcd 22' gone off no 5 volts

    You titled this "no 5 volts", does this mean you have the set open and have been tracing the circuit? My primary suspect would be burst capacitor(s) on the PSU board, domed on top, possibly leaking crusty residue. Your PSU board might look like the following and the cap(s) mostly likely to...
  19. dave9

    HV Rat Killer

    It would be my loss if I assisted you in electrocuting yourself or a 3rd (non-rat :eek:) party. More yours than mine but I would feel remorse. As an engineer for 40 years you should know that many things aren't worth the time to build from scratch unless you can make it significantly better...
  20. dave9

    HV Rat Killer

    There is a difference between reusing an old transformer for a hobby project and creating a 500VA electrocution device when you don't know where to start. If you really want to electrocute them, I recommend buying a ~$50 battery powered unit. By the time you create a safe enclosure, devise a...
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