#garfield Logs

Jan 01 2018

12:16 AM rue_shop3: 5578
12:20 AM rue_shop3: 5578
12:20 AM rue_shop3: 5578
10:24 PM jennie_: hello
10:25 PM rue_mohr: hello....
10:25 PM rue_mohr: who are you?
10:26 PM jennie_: I am jennie, you helped me in making a driver circuit for HDD salvaged motor
10:27 PM rue_mohr: ... about 8 years ago?
10:27 PM jennie_: like 5/
10:27 PM rue_mohr: ok...
10:27 PM rue_mohr: dont know how I remember at all
10:27 PM jennie_: you are smart ;)
10:29 PM rue_mohr: did you see china is selling hdd motor driver boards now?
10:29 PM jennie_: really?
10:29 PM jennie_: did not see
10:29 PM rue_bed: yep
10:30 PM rue_bed: got one to play with, didn't like the motor (ok, it wasn't a hdd motor) I tried to set it up with
10:30 PM rue_bed: so, what have you been up to in the last 5 years?
10:30 PM jennie_: did it work?
10:30 PM rue_bed: yes, kinda, worked better with a smaller size motor
10:31 PM jennie_: cool
10:32 PM jennie_: rue_bed i have a simple question about a charging circuit
10:32 PM jennie_: do you mind looking at it?
10:32 PM rue_bed: go for it
10:33 PM jennie_: https://i.stack.imgur.com/NQSOa.png in this simple circuit
10:34 PM jennie_: so in this circuit, if i put two females USB DIP at the output with 1/2watt resistors
10:34 PM jennie_: and lets assume i plug in two devices which needs 1A each, so is one Voltage dividder going to work for two devices or i need dedicated voltage divider for each female USB DIP
10:35 PM rue_bed: because they are generating the data voltages per socket, you would want two dividers
10:35 PM jennie_: but this guy in ##electronics channel said this to me just now
10:36 PM jennie_: 23:32:38] <tawr> jennie_: omfg. read what i am saying. none of that matters.
10:36 PM jennie_: [
10:36 PM jennie_: [23:34:09] <tawr> you are NOT charging the batteries over usb. a dedicated power management IC and lithium polymer charging chip are doing EVERYTHING. they are SMART. the voltage at the data pins tells the CHARGING device how much power it can safely draw. that's it. the PMIC and charging chips then only pull that much power. they are smart.
10:36 PM jennie_: [23:35:23] <tawr> jennie_: chances are you don't even NEED any of that. if you just applied 5v, t would charge, but prolly default to 500ma.
10:36 PM jennie_: ["
10:37 PM rue_bed: it might work to use the same for each port, but I wouldn't advise it, if a hub asks a question on the usb bus, it shouldn't interfere with the other port
10:37 PM rue_bed: ...
10:37 PM jennie_: so this is what happened
10:38 PM jennie_: let me get to start
10:38 PM rue_bed: are you makeing a power supply or using another usb device as the power supply?
10:39 PM rue_bed: if the device you making is the supply, you dont need the resistors
10:39 PM rue_bed: actually, I have seen some devces that do need it...
10:39 PM rue_bed: hmm
10:41 PM jennie_: so
10:42 PM jennie_: 23:31:03] <jennie_> but i wonder if i can put two female usb DIP at output of that circuit and charge two devices
10:42 PM jennie_: [23:31:10] <tawr> jennie_: sure you can
10:42 PM jennie_: [23:31:38] <tawr> and you can set it to 2A. phones and tablets are 'smart'. they have dedicated chips for charging current. they arent dumb like a lightbulb or motor
10:42 PM jennie_: now
10:42 PM rue_bed: k
10:42 PM jennie_: i want to charge phone from dc bench power supply
10:42 PM rue_bed: you "shouldn't" need resistors
10:42 PM jennie_: i googled and found that iphone needs voltage dividers else it wont work
10:42 PM jennie_: wont charge
10:43 PM Tom_L: standard USB allows for 500ma unless it's a powered port
10:43 PM jennie_: so i ended up on stack exchange and found that circit
10:43 PM rue_bed: if you hook up the power and it wont doit, you need resistors
10:43 PM Tom_L: it's way abused though
10:43 PM rue_bed: k
10:43 PM jennie_: apple needs voltage dividers on data lines to charge any apple device
10:43 PM jennie_: https://electronics.stackexchange.com/questions/177788/how-do-i-design-a-2a-or-more-power-supply-for-my-consumer-usb-devices/177792
10:43 PM jennie_: here ^
10:44 PM rue_bed: so then I'd say you can use the same dividers for both ports
10:44 PM jennie_: yes
10:44 PM jennie_: how
10:44 PM rue_bed: oh, connect D- and D+ togethor on the two connectors
10:44 PM jennie_: because each phone has different charging chip and they are gonna decide?
10:44 PM rue_bed: they will just look at the voltages, they wont ask questions
10:45 PM jennie_: k
10:45 PM rue_bed: a usb controller asks questions and tries to talk so, the other way (usb male) wouldn't be happy
10:46 PM jennie_: I am only concerned about charging, thats it
10:46 PM Tom_L: those don't support wireless charging do they?
10:46 PM jennie_: as you said, i can connect D- D+ of both USB female DIP and connect them to one voltage divider right?
10:46 PM jennie_: and can charge 2 phones at same time
10:47 PM Tom_L: because it's a pretty cool thinkg
10:47 PM rue_bed: 4 resistors
10:47 PM rue_bed: gnd-gnd
10:48 PM rue_bed: D+ D+
10:48 PM rue_bed: D- D-
10:48 PM rue_bed: 5V 5V
10:48 PM jennie_: rue_bed , from that stack exchange article, here is a quote " Placing approximately 2.0V on the D- line, and 2.75V on the D+ line will signal 2A "
10:49 PM jennie_: how did tehy calculate this 2A
10:49 PM rue_bed: its a spec in a table
10:49 PM jennie_: whats the formula
10:49 PM jennie_: which table
10:49 PM rue_bed: dunno
10:49 PM rue_bed: coffeetable in apple
10:49 PM rue_bed: :)
10:49 PM jennie_: lol
10:49 PM Tom_L: https://www.electronicspoint.com/threads/resistor-values-for-a-usb-charger.283081/
10:51 PM Tom_L: http://blog.curioussystem.com/2010/08/the-dirty-truth-about-usb-device-charging/
10:56 PM jennie_: interesting
10:56 PM jennie_: thx
11:04 PM jennie_: rue_bed if i put 5vdc across those resistors of 1/2watt, the what do you think how much amps those 4 resistors are going to consume when there is no load on USB female
11:06 PM rue_bed: no current, 1/16w resistors are fine
11:08 PM jennie_: sorry its confusing, it must consume some mA right?
11:08 PM jennie_: and what difference its going to make with 1/16 or 1/2 or 1/4 watt resistors
11:09 PM rue_bed: rating of the resistors,
11:09 PM rue_bed: there is almost no current they dissiapte almost no power
11:12 PM jennie_: i <jennie_> and what difference its going to make with 1/16 or 1/2 or 1/4 watt resistors - I meant to ask here, on the output AMPS or any other change you can think of
11:23 PM rue_bed: it just generates a reference signal that the phone uses when charging, the resistors aren't used for anyting power related, just to idtentify
11:24 PM rue_bed: all resistors generate heat
11:24 PM rue_bed: the rating says the max amount of heat they can produce before burning up