kyak changed the topic of #qi-hardware to: Copyleft hardware - http://qi-hardware.com | hardware hackers join here to discuss Ben NanoNote, atben/atusb 802.15.4 wireless, anelok and other community driven hw projects | public logging at http://en.qi-hardware.com/irclogs and http://irclog.whitequark.org/qi-hardware
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<whitequark> opbolt: current indication for phones?
<whitequark> if you mean the thing that tells a smartphone to draw 1A or 2A instead of 500mA permitted by the spec, short D+ and D-
<whitequark> that's it
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<opbolt> whitequark, yes
<opbolt> so that tell them its all they can eat? well then thats easier that i thought. i thought i needed special ic to handle off the differences like in fancy 5v usb power supplys.
<opbolt> off=all
<opbolt> thx
<whitequark> opbolt: correction: by the spec, a device can draw 1.5A from a dedicated charging port
<whitequark> the one with D+/D- shorted
<opbolt> arr ok. so not 2a but 1.5v is enough
<opbolt> 1.5a isolated dc-dc supplys will be cheaper than 2a ones anyway :)
<opbolt> thanks muchly
<whitequark> opbolt: take a look at https://pdfserv.maximintegrated.com/en/an/TUT5801.pdf too
<whitequark> it's a bit more complicated than that in practice because vendors implement proprietary extensions
<opbolt> arr thank much just what i needed
<opbolt> typical of them
<DocScrutinizer05> there are like 4 different specs how chargers signal max-current to charging-peripheral. shorting D+/D- is the simplest one. Then there's "apple" method of attaching voltage dividers and thus voltage levels from VBUS to D+ and D-, then you also could add a certain resisitr from ID to GND, and finally there's ENUM (digital)
<whitequark> yeah that pdf lists them :)
<DocScrutinizer05> maxim? yes, has some good datasheets and whitepapers covering this madness
<whitequark> the chips tend to have obnoxious bugs though
<opbolt> every grateful
<opbolt> been blowing up china dc-dc +/- dc convters :( i see in exspensive ones on digkey there is a capacitive load column like 2000uf etc... hmm need to read up about this but i noted that on pwoer up the tone board needs more than a 1A as the 2000uf caps charge up then then goes down to under 100ma i think it was. wondering if the very high current demand on power up is what is frying these dc-dc converter boards
<opbolt> my higher power china dc-dc converter board has suvived but it seams to be adding noise to the audio signal :( so im scanning though digkey or rapid for something better to power these tones boards
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<opbolt> arrgh finding +/-15 dc-dc converters with 2000uf capacitive load is not easy!
<opbolt> most dont go above 500uf... more seaching to do
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<whitequark> you could just add an inductor
<whitequark> to limit inrush current
<whitequark> that'll also make the output cleaner
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<opbolt> whitequark, oow how?
<opbolt> the isolation would help with classic ground noise loop thingy type problem i’ve been having too
<opbolt> that or audio isolators but that risks audio fidelity
<opbolt> besides ive blow up the last china dc-dc converter i had. some odd thing happened when i connected it to the same power supply as the amp. blow it up, buble os smoke. so i give up. just feel like splashing on fancy thing that will do the job and call it a day.
<opbolt> worked fine when powered from another battery with dc-dc boost converter outputing 19v. meaning it was ok when i was isolated from amp power supply, which is 30v. max volt of tone board dc-dc convter was 40v. so idk why it blow up. need to learn a new deeper leave of detail to answer that. which means more time...
<opbolt> still interested to know how i could use an inductor :) i just cant try it out anymore
<opbolt> spend bloody £40 on many cheap dc-dc converts and a vu meter boards/modules that have gotten blow up. which is just silly. hench spending £25-£40 on a fancy isolated dc-dc is not sounding so bad... mmhhh
<whitequark> opbolt: try google
<opbolt> yea ok
<opbolt> thx
<whitequark> but you probably don't want these in a battery powered system
<opbolt> oh?
<opbolt> i was just larghing at the thought i could have spent a few pennys on a little thing that would have sovled the inrush problem
<opbolt> laughing
<opbolt> on 200ohm i see
<opbolt> oh
<opbolt> yea dont want that
<opbolt> hmm
<whitequark> opbolt: no
<whitequark> 200 ohm is the initial resistance
<whitequark> it's an NTC resistor
<opbolt> oh
<opbolt> then again at 200ohm maybe tis not so bad. the pre amp is under 100ma it seams. more like 40ma i think :/ feel i need to check that
<whitequark> sigh
<whitequark> please read the datasheet and understand how it works
<opbolt> sorry stupid idk what i talking about, i thank you for you time
<opbolt> ill have a look at the datasheet
<opbolt> thank you
<opbolt> time to read some books
<opbolt> youve been very helpful in pointing me in a direction
<whitequark> it offers a more complex but much more efficient solution
<whitequark> with a FET
<whitequark> fig 5
<opbolt> "Once the circuit is energized the resistance of the MF72 will decrease rapidly to a very low value, power consumption can be ignored and there will be no effect on normal operating current." ooh i see what ya mean :) i can use a cheaper dc-dc :) with one of these
<whitequark> yes
<opbolt> Yay!
<opbolt> having a look at fig 5 now