Messages

1

5x00 Hardware / Homemade Car Charger

« on: July 27, 2004, 08:59:16 pm »

Potentiometer creep is kept from blowing up the z by the 1N4734A 5.6v zener diode, if the output voltage goes over 5.6v the worst that will happen is the zener will blow and short circuit the output section.  This will consequently blow the input fuse.  The circuit will need repair but the Z will be ok.

The ac adapter puts out 5.2v unloaded, so an absolute maximum of 5.6v shouldn't be enough to destroy the Z's internal charging circuitry.

2

5x00 Hardware / Homemade Car Charger

« on: July 25, 2004, 09:11:13 pm »

Actually I used an LM285Z for the voltage reference.  The to-92 package was easy to shoehorn onto the limited board space I had to work with.

I have an SL-5600 and it works perfectly well running off of a charger.  I would venture to guess that a 5500 would be the same way.

Thanks for the compliment, however most of the circuit design was scavenged from the page referenced.  The adaptations are fairly standard for introducing a circuit into an automotive environment.

3

5x00 Hardware / Homemade Car Charger

« on: July 21, 2004, 11:02:29 pm »

For anyone interested in building a car charger for their zaurus, this is a report on my experience in doing so.  My first attempt was to construct a reference design for a pair of LM7805 5 volt linear regulators in parallel.  Each LM7805 is rated for 1A, therefore I made the assumption that they would be able to handle the 2A draw that the sharp AC adapter is rated for.  The linear adapter showed excellent ripple rejection and load regulation.  However, after extended use the circuit overheated and the linear regulators went into thermal shutdown.

After that I realized that due to the lack of heat sink space and the current requirements of the zaurus, I had to implement a switch mode power supply.  I found a switch mode power supply implemented utilizing a pair of 555 timers.  It takes a minimum of components and can easily be adapted for the purposes of this adapter.  That circuit may be found here.

My adaptation of this circuit is as follows:

[img]http://www.moonpolysoft.com/circuit.png\" border=\"0\" class=\"linked-image\" /]

L1 is a supply choke to filter out ignition spikes and protect other electronics from ripple eminating from the switch mode power supply.  

U2 is a zener diode to protect the 556 and LM411 in case any spikes make it past the supply choke.  U2 is a 5W diode, so it should be able to handle anything short of tractor trailer 24v supply.  

I changed R5 from a fixed voltage divider to a 20k potentiometer.  I found that even 1% resistors were not accurate enough to regulate the supply to within 5% of 5v.  Therefore the potentiometer must be hand trimmed with an o-scope or multimeter.  This also acounts for any difference in the gain of the opamp, therefore different units can be switched out according to availability.  

Finally, I changed out the MOSFET to a ZXM64.  The ZX has an exceptionally low on resistance and a peak current rating of 13A.

If anyone has interest in making one of these, I will post a digikey part manifest and pictures of my board.  Thanks.

4

OpenZaurus/Opie/Qtopia / mediaplayer 2 and mp3 skipping

« on: June 27, 2004, 09:10:02 pm »

I am having trouble with mp3 playback in mediaplayer 2 on my sl-5600.  When playing mp3's mediaplayer2 will continually keep skipping forward within the song.

I have tried installing the original mediaplayer and xmms-e but both unfortunately give me segfaults.

Some preliminary searching around varied support forums has turned up mention of alsa-modules.  I cannot find alsa modules for oz in any of the feeds or on google.  Any help would be greatly appreciated.

System configuration:
opie v1.1.3
kernel 2.4.18-rmk7-pxa3-embedix-021129
oz 3.3.6-pre

5

Angstrom & OpenZaurus / windows usb connectivity: sl-5600 and openzaurus 3.3.5 rom

« on: June 17, 2004, 11:19:34 am »

my apologies, I should have read your script first.  Read it after my last post, and it worked like a charm.  My last question is, do I have to do that every time i plug in, or just once?  If so i\'ll have to devise a method to do it automatically on plug in.  Thank you very much for your help.

6

Angstrom & OpenZaurus / windows usb connectivity: sl-5600 and openzaurus 3.3.5 rom

« on: June 17, 2004, 10:12:35 am »

I tried to modprobe -r net_fd, however all I get from that is:

Code: [Select]

root@openzaurus:~# modprobe -r net_fd

net_fd: Device or resource busy

my lsmod looks as follows:

Code: [Select]

Module            Used by

usbdmonitor       0

sharp_mmcsd_m     1

pxa_bi            0

net_fd            1

usbdserial        0

usbdcore          0  [pxa_bi net_fd]

In addition, I tried to hook the zaurus up to my linux box using the usbnet module, and I\'m getting error messages in my /var/log/message

Code: [Select]

Jun 17 03:12:19 moonpolysoft kernel: usb 4-2: new full speed USB device using address 8

Jun 17 03:12:19 moonpolysoft kernel: usb 4-2: device not accepting address 8, error -71

Jun 17 03:12:19 moonpolysoft kernel: usb 4-2: new full speed USB device using address 9

Jun 17 03:12:20 moonpolysoft kernel: usb 4-2: device not accepting address 9, error -71

It will print those two error messages each time it is plugged in, incrementing the address each time.

Thanks for your help.

7

Angstrom & OpenZaurus / windows usb connectivity: sl-5600 and openzaurus 3.3.5 rom

« on: June 17, 2004, 02:22:27 am »

I just flashed my 5600 with the open zaurus 3.3.5 rom.  When connected to the docking station the windows drivers are no longer recognized.  XP keeps saying that the zaurus is an \"unknown device.\"  I\'ve tried installing the drivers manually, but windows will not accept them.  Does the openzaurus rom change the vid/pid of the zaurus connecting to usb?  Any help would be greatly appreciated.