Hello Jan! > OP: original posting/poster. Okok, i see :-).
> Increasing the capacitors make things *worse*, not better! Empty capacitors > are like short circuits. You have to limit the current flowing into empty > capacitors by applying a resistor or (better) a choke coil to the supply > lines. But i think the usb power supply isn't switched on or off. So the Capacitors have to be loaded only if i plug in the device. And that's not the problem. The failure happens after a few successful transactions. If the power supply would be switched the choke coils would make bad things too. At least if they are large enough to store reasonable amounts of energy. (Wasn't there something like u_L=di_L/dt? At least there would be large voltage peaks then....) > USB circuits are powered on on detection/driver-reload, so this power-on > problem is more inconvenient than with other devices. Are you sure? Of course the peripheral device may be in some sort oft sleep mode until it's initialized by a driver. But the power supply on the usb-bus is on all the time. At least in my experiences. > Even a "quick melt" 100mA fuse (your other posting) sure doesn't melt if a 1A > current is flowing for a few µs. Melting is a energy -- not current -- > related process, and ~1A*0,1V*100µs=10µJ is too few energy to melt even a > thin stanniol wire .There are fuse deratings to calculate the neccessary > current for a given time. This is why melting fuses are useless as soon as > high-speed electronic switches should be protected. Your fuse protects the > onewire cable, not the interface circuit. The facts about burning the fuse are certainly right. But this current peaks should be blocked by the capacitors in the usb power supply lines (33pF, 100nF, 4,7uF). If this is not sufficient i guess i would need a choke coil instead which is larger than the whole circuit itself :-). But i will test your advice. > Most USB interfaces in desktop computers doesn't have appropiate current > limiting switches (MIC2075 or TPS2024) to limit the current to the specified > 500mA, but instead use a 1A fuse. Your laptop however, may use such a > switch -- because a molt fuse is inconvenient in a laptop -- and thus, cause > problems. Hm, at the weekend i will have access to some testing equipment and then i will check this. best wishes! Klaus ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
