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  1. dave9

    How long does it take to charge a 500mAh battery with 5V 80mA?

    ^ Except you forgot the losses boosting the 3.7V battery to 5V for USB input to the phone, then the losses charging the phone battery.
  2. dave9

    Dyson V8 bypass sensors and alternative power supply

    Dyson V8's run at nominal 21V (6 cell battery) and 2800mAh, 40 min on standard mode w/o brush tool, but roughly 11 min on turbo mode. Certainly there are losses but before them that's 320W... and it's still too weak. I'd think about getting a 40V or higher, brushless leaf blower for the...
  3. dave9

    Fire alarm using a PTC as a sensor.

    There's nothing ideal about being knocked unconscious from lack of oxygen from the smoke, long before it got hot enough to set off a heat detector. Having the extra time to evacuate can be crucial. I'm sure there are some special circumstances where the opposite is true but try it for...
  4. dave9

    Fire alarm using a PTC as a sensor.

    High temperature sensing is terrible indicator of a fire, unless it's just the wax slug in a sprinkler head, activating it to save property. Smoke preceeding the temp rise will suffocate inhabitants, and the smoke is (usually) detectable using existing tech, far in advance of the temperature...
  5. dave9

    How long does it take to charge a 500mAh battery with 5V 80mA?

    There is no simple equation, because (presuming your 3.7V is Li-Ion) you're starting with a solar cell rated for max output, which you will not achieve in sequential hours over the amount of time it would take, then needing a charge controller to not damage the Li-Ion 500mAh battery through...
  6. dave9

    power supply Pace Sky Digibox 2600

    Something is not working with the image attachment view counter. I click/viewed all three images but the counter still shows "Views: 0"... after refreshing the page too.
  7. dave9

    power supply Pace Sky Digibox 2600

    What is the evidence of no longer receiving power? You'd pick a spot and trace backwards along the power path, identify faulty component, identify the type of component (suitable replacement candidates) and swap it in. Parts may be available at electronics suppliers, which ones depending on...
  8. dave9

    USB Charger and Buck converter

    You are working with a quite low, 1.7V max vDrop from your regulation circuit. I would try to find a PWM buck, current regulating driver instead of what looks like you are just setting a voltage regulated driver to "about" what the LED would need for a target current. I used to get such things...
  9. dave9

    Can this ceiling fan remote be fixed?

    ^ I think it's more likely something like a pairing code that the DIP switches set, and no the dip switches can't change the saw threshold which is just shunting to ground, but I wouldn't put too much work into this when (if you're in the US or another market with amazon or ebay available) they...
  10. dave9

    Can this ceiling fan remote be fixed?

    ^ It reads: H P303A (or maybe R303A) See this page, states 303.9MHz and you can see how this is situated in the casing: https://www.amazon.com/Ceiling-Replacement-L3HFAN35T1-FAN-35T1-L3HFAN35T/dp/B0922K9NJD The FCC pic has one that's 303.875...
  11. dave9

    Can this ceiling fan remote be fixed?

    ^ BINGO! This is an RF remote, not IR. Besides, an IR LED can't cycle anywhere near as high as ~300MHz where these operate and was stated plus the orientation of the LED, that it's just a visual indicator that a button was pressed. Stupid question but, did you check the battery voltage? Is...
  12. dave9

    Issues with replacing Dead Laptop Motherboard...

    I'd assume the new board is DOA and seek a refund.
  13. dave9

    What optical mouse product works on a smooth surface?

    Also, it helps if the surface isn't especially shiny. I prefer a mouse pad, easier on the hands and wrists.
  14. dave9

    USB Power Supply Contacts

    Yeah a tip that wets well is very useful, but it doesn't necessarily need to be a tiny one. The tip might've needed cleaned, or oxidized metal removed at which point it has a very short lifespan before you'd need to do that again as it means the plating is shot. This is one of the big...
  15. dave9

    USB Power Supply Contacts

    Glad it works! Be careful with heat guns around connectors with plastic inside, can melt them so it is handy to have a sheet of mica to put between, shield and keep the heat away. I would just avoid using a heat gun with the plastic so close. The main thing I would do differently, is I would...
  16. dave9

    Remington Shaver HC6550 not to full Power

    I agree it could be a protection circuit, trace the power route between battery and motor and you should find some tiny IC, maybe instead a transistor it operates too, in series in this path. However it could be a blown chip due to heat, or could really be that the motor is shorting out or...
  17. dave9

    Maximum solar panel wattage for 200ah gel battery

    Your charge controller is selected based on the capabilities of the solar panels connected, type of battery and acceptable charge rate. If you have the right charge controller, it will not over-charge the battery no matter how many solar panels worth of excess capacity you have. The remaining...
  18. dave9

    Remington Shaver HC6550 not to full Power

    Can you measure battery voltage at the charging contacts (if it has any that are accessible)? If so then compare full charge voltage to the voltage at the point of shutdown. It might just be a dying battery. How old is it? If you have no external measurement points then you have to open it...
  19. dave9

    Please help a lay person with some repair questions

    Also I know nothing of how advanced the circuitry is in any particular massage chair, but it seems like on better designed models, if there is no travel limiter sensor/switch (if there is, then check those), then there might be fusible circuits for each motor so check fuses... thinking maybe...
  20. dave9

    Please help a lay person with some repair questions

    Basic diagnosis might involve checking for resistance across the switch contacts when pressed, examining the PCB for stress cracks, measuring for where in the circuit the power stops. Once you determine the fault, then determine whether a discrete component can be replaced, or a motor (might...
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