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Re: Power Supply Load Management

 by langwadt ¦  Sat Nov 24, 2012 2:10 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Power Supply Load Management ¦  Replies: 7 ¦  Views: 699

if you can live with the loss of a diode voltage you can just put a diode in series with each supply, the active switching is for when you cannot live with the voltage or power loss over a diode so it uses fets instead

Re: Polygon Pour Heatsink

 by langwadt ¦  Thu Nov 15, 2012 10:13 am ¦  Forum: PCB Design Questions ¦  Topic: Polygon Pour Heatsink ¦  Replies: 10 ¦  Views: 2904

several example in this:

but I don't think 5.5W is doable

Re: Where are stand-offs in Eagle?

 by langwadt ¦  Sun Nov 11, 2012 2:07 pm ¦  Forum: PCB Design Questions ¦  Topic: Where are stand-offs in Eagle? ¦  Replies: 6 ¦  Views: 2480

Thanks Lang, never knew that! Figured standoffs were pretty much standard size. That's what I get for building computers.. Used to the stand-offs being just one size. don't want to make it more complicated than it is, just putting a few 3mm hole on the pcb will work just fine. but sometimes you wan...

Re: Where are stand-offs in Eagle?

 by langwadt ¦  Fri Nov 09, 2012 6:17 pm ¦  Forum: PCB Design Questions ¦  Topic: Where are stand-offs in Eagle? ¦  Replies: 6 ¦  Views: 2480

Stand-offs are not part of the PCB. They are hardware for mounting PCBs. Stand-offs mount by the holes in your PCB. There is a standard library in Eagle for mounting holes called "hole." Sparkfun's library as a mounting hole as well, but just one size. often the right thing to do is to have standof...

Re: Solar Charger Diode/MOSFET Query

 by langwadt ¦  Sun Oct 28, 2012 6:54 am ¦  Forum: SparkFun Product Questions ¦  Topic: Solar Charger Diode/MOSFET Query ¦  Replies: 19 ¦  Views: 7513

you only need back to back if you really need to block in both directions(like for an AC switch), if you only need block in one direction like replacing a diode just reverse the mosfet, if you don't turn it on it work just like normal diode, turn it on and you get the reduced voltage drop if the sol...

Re: How to know motor drive current by EasyDriver

 by langwadt ¦  Sun Oct 21, 2012 3:39 pm ¦  Forum: SparkFun Product Questions ¦  Topic: How to know motor drive current by EasyDriver ¦  Replies: 3 ¦  Views: 440

uses schematic and datasheet to figure out relation between Vref and current, use a voltmeter to measure and set the reference voltage, there's even a test point for it

Re: can i do this

 by langwadt ¦  Tue Oct 02, 2012 7:03 am ¦  Forum: PCB Design Questions ¦  Topic: can i do this ¦  Replies: 3 ¦  Views: 631

I assume the LED are driven with some sort of constant current driver, shouldn't be too hard to trace the board to find the current sense resistor and parallel it with something to get the current you want

Re: 3.3 & 5V voltage reg OR 5V voltage reg to voltage divide

 by langwadt ¦  Thu Aug 09, 2012 1:15 pm ¦  Forum: PCB Design Questions ¦  Topic: 3.3 & 5V voltage reg OR 5V voltage reg to voltage divider? ¦  Replies: 12 ¦  Views: 4012

you'll need to find a real LDO, LD1117 has a drop out of ~1V typical so you can't get 5V out from 6V minus a diode drop in

Re: IDC vampire connectors for mating ribbon cables?

 by langwadt ¦  Thu Jul 19, 2012 4:10 pm ¦  Forum: SparkFun Product Questions ¦  Topic: IDC vampire connectors for mating ribbon cables? ¦  Replies: 3 ¦  Views: 752

you can get male idc connectors so you could just put female idcs on you main cable and plug short male-female onto cable to it

but why not use a longer main cable and just make a 90-180-90 degree turn at every "tap"

Re: Ribbon cable for larger connector

 by langwadt ¦  Wed Jul 18, 2012 4:51 am ¦  Forum: PCB Design Questions ¦  Topic: Ribbon cable for larger connector ¦  Replies: 3 ¦  Views: 796

you can get 2*25pin flat cable connector but I don't see much point for 10-12 connections one option is to put something like this: on your board and just plug the stm32 on top it like arduino and shields makes more sense and is more flexible to use somethi...

Re: two voltage switch with potentiometer?

 by langwadt ¦  Fri May 25, 2012 2:28 pm ¦  Forum: SparkFun Product Questions ¦  Topic: two voltage switch with potentiometer? ¦  Replies: 2 ¦  Views: 419

I'd but a large-ish resistor across the relay so the output always tied to something also when the relay changes state

Re: Looking for a certain keypad

 by langwadt ¦  Wed May 23, 2012 4:10 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Looking for a certain keypad ¦  Replies: 6 ¦  Views: 543

Re: man, i need a solder 101 stat!

 by langwadt ¦  Tue May 22, 2012 3:44 pm ¦  Forum: SparkFun Product Questions ¦  Topic: man, i need a solder 101 stat! ¦  Replies: 16 ¦  Views: 1448

here i was thinking the solder would definitly stick to any kind of metal. it doesn't. i've seen you tube videos, they don't tell the whole story, i need the why's as well as the how's and some when's would be cool too.. i have a solder tip refresher, a maintenance tip cake, a wet sponge, and a bra...

Re: what's a de-soldering iron?

 by langwadt ¦  Fri Apr 27, 2012 5:16 pm ¦  Forum: SparkFun Product Questions ¦  Topic: what's a de-soldering iron? ¦  Replies: 9 ¦  Views: 796

cut it apart and take one pin at a time, not worth ruining a pcb to save a header

Re: Spartan 3E - Can't decide...

 by langwadt ¦  Thu Apr 12, 2012 5:10 am ¦  Forum: SparkFun Product Questions ¦  Topic: Spartan 3E - Can't decide... ¦  Replies: 1 ¦  Views: 355

for glue logic a cpld might be better suited than an fpga it is instant on and doesn't need the external flash (most) fpga need.
unless the fpga is very full and/or you are running extremly fast I don't see why pin location is a big issue they are are to a large extend
"all the same"