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  1. dave9

    Reduce LED Brightness

    ^ It is a 24VDC supply, which I would not have chosen, along with not choosing 24V LED modules, but zoom38 already has them, they have integrated resistors (don't know if they can be opened and swapped with a different value resistor), and are fairly expensive for what they are. If it were...
  2. dave9

    How long lifepo4 battery power tv

    OOPS! I'm wrong. LiFePO4 nominal is 3.3V not 3.7V... so take Harald's calculation and * 3.3/3.7 = ~8hrs runtime, although with 3.3V cells, I wonder of they just put them in parallel series of 4 cells for 13.2V and called it 12V to save on the BOM by omitting a boost converter, then it gets 20%...
  3. dave9

    How long lifepo4 battery power tv

    If you mean that you have one of those (consumer rather than industrial grade) battery power packs sold as an already integrated unit and its rating is 100Ah and 12V, then it is most likely that it is not 100Ah AT 12V but rather, 100Ah at 3.7V. Mathematical shenanigans.
  4. dave9

    Identify brand of switch

    You need better humidity control in the vehicle. While they are apart, after cleaned I would tin the contacts with silver solder, if I couldn't find suitable replacements, and put some dielectric grease in it. Brand may not mean much. If this is not a somewhat standard switch, it might have...
  5. dave9

    Reduce LED Brightness

    I would use a series resistor. The question is how much (%) brightness do you want? If you want 50% of the current brightness, then as Martaine2005 mentioned, it is probably about 1.5K resistor internal so add a 1.5K 1/2W in series. Another way to reduce brightness is just put a thin coat of...
  6. dave9

    Class D SMPs Combi

    Even with 300K pic size limit, you could do a lot better than that including other sides of it. Is it modularized with the left board just a PSU function and the right, connected by wires, the amp board? If so, unplug the amp. Try PSU without amp, and try amp with a different PSU. Ideally a...
  7. dave9

    how to connect laptop power cable to a PSU?

    Find a ground point on the laptop mainboard to determine which contact in the socket is ground, through resistance measurement with a multimeter. It's probably the outer contact on the plug, then the contact on the inner sleeve is positive, then the pin on the middle is a data line to ID the...
  8. dave9

    Have all the UPS makers switched to no consumer battery replacement?

    If you're using them often enough to wear them out in 3 years, it seems like it would be worth getting one that's overkill just for long term cost savings from being able to replace the battery. I mean you can get the BE550G for around $60 on sale or $75 otherwise, then just a standard 7Ah to...
  9. dave9

    Have all the UPS makers switched to no consumer battery replacement?

    I was not aware of this, so went on APC's site to look at a modern equivalent of one I bought a long time ago, and they sell a replacement battery for it so I must conclude it is serviceable. Their linked manual also shows the battery hatch on the back...
  10. dave9

    e scooter power switch oddity

    I think we need a schematic and you need a fire extinguisher.
  11. dave9

    MP3 Player project

    I recommend finding some older, near-worthless smartphone, perhaps new enough that replacement batteries exist, then weed through existing audio apps to find the one you like the best. There were old smartphones, and java capable predecessors that are quite small if you dislike the large...
  12. dave9

    Tape deck power issue

    Did you remember to plug it back into the wall outlet? ;)
  13. dave9

    Regulated 12v supply

    There are some real engineers here that can calculate amount of capacitance needed for amount of ripple at current, but you didn't mention the current your circuit needs to be capable of. However with 7812, some would use a generic rule like 1000uF between transformer and that regulator for...
  14. dave9

    Regulated 12v supply

    More info needed. All info needed. Schematic wouldn't hurt either.
  15. dave9

    Replacing a battery charger transformer with a audio transformer can I do it?

    You could use a lower amp transformer assuming it's their unregulated, non-SMPS type charger, just won't charge as fast, and buying it may cost about as much as an entire ready made charger. Backing up a bit, did you measure the output of the transformer to know it's bad? If not, might be the...
  16. dave9

    Replacing a battery charger transformer with a audio transformer can I do it?

    No, the transformer for the charger is higher current and lower voltage than the receiver, not even close.
  17. dave9

    Replacing a battery charger transformer with a audio transformer can I do it?

    Seriously, you didn't even mention what kind of battery (charger) ! Probably not. The battery charger transformer for a typical automotive 12V battery is likely to be around 14VAC, possibly also a 7VAC center tap for 6V batteries while the typical transformer in a receiver/amp (assume you do...
  18. dave9

    Install Bluetooth to treadmill

    So all you need is the pinout for HC05? I found it by searching for, (of all things) "HC05". https://components101.com/wireless/hc-05-bluetooth-module As for the connections on the board, a "good" (posted elsewhere in high resolution with good lighting) picture might help, or you can trace...
  19. dave9

    Install Bluetooth to treadmill

    Don't buy into the nonsense that is promoted by marketing agencies that you need high tech involved with exercise. You don't need bluetooth on a treadmill. Heart rate monitor perhaps, but bluetooth, no.
  20. dave9

    Malibu Landscape Lighting Parasitic Draw

    Replacement relay came in the mail today, soldered it in and reinstalled it outside powering the lights, seems to work fine again. I cut open the old relay with a rotary tool but did not observe any carbon or other material that would have caused a short. It looked clean inside, besides a few...
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