SPC900 LXmod yesyes style ;-)

[malc-c]

The switch you have is a double pole double throw (DPDT) one. Each group of three terminals is a changeover switch where toggling the switch changes the connection between a centre terminal and the ones on either side of it. So to use it in your circuit, just connect to one of the centre terminals and either one of the terminals on the same group of three.

IE between pins A & C or C and E or B & D or D & F

[Reggie]

As this is the main spc900/880 modding thread, I thought it would be the appropriate place to post it:

Cosmicshed: Sharpness Control for Philips Webcams and Derivatives

If the 'ears' as described are relatively random and a product of the cameras onboard processing, I wonder if this has a bearing on guiding at all? It seems that the sharpness setting at the very least introduces more software correction in post processing.

[NEM]

You have four possibilities, that is you can use A&C or C&E or B&D or D&F. The only difference between them is that A&C and B&D will be 'ON' when the switch is in one position and C&E and D&F 'ON' when it's in the other position.

Regards,

Noel

[Davie]

Thanks for the replies and confirming what my steam powered brain had thought.

Thanks malc for taking the time to make up the photo with the lettering :-)

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[Davie]

Hopefully one last question before I get to try this thing out once the USB to Serial adapter arrives.

As mentioned above I'm trying to do this mod with the logic chip rather than he vero board and because of this im now lost at the last hurdle.

I'm looking for the connections to the adapter and I "think" that it should be like this going from the drawing Chris has at the start of this thread

Pin 6 on the chip is the RTS line and therefore goes to pin 7 on the adapter

Pin 7 on the chip is the ground and goes to pin 5 on the adapter

and the last one from Q3 on the board , the DTR line goes to pin 4 on the adapter.

Am I speaking utter nonsense?

Thanks again

Davie

[yesyes]

Sounds alright, though I can't verify the pin numbers on the chip. Do you have the schematics you are using for the chip based mod or a link to it?

[Davie]

I've been moving between your thread here Chris and this one of Geppettos on post 6 theres a picture of the chip with the legs all marked off, sorry not much help with this as mentioned above im not much use with this electrical lark.

I was also going to ask about your one cable solution with the USB hub. Could you get away with using the original camera USB cable and then using the pins underneath the USB socket to connect to the USB to RS232? this would make it a little neater if you didn't require extra USB connections.

Thanks again for your patience

[yesyes]

OK, I've had a look at that other circuit. Indeed, pin 6 of the chip goes to the RTS pin 7 on the adapter. You may still need that resistor in-line that can be seen soldered to the DB25 plug. Hard to tell without a full circuit diagram.

Then you need to connect ground to USB ground and +5V on the chip to USB 5V.

Also, this circuit does not include the Amp Off mod. Do NOT just connect base of Q3 to DTR on the converter. You will need that lower part of the circuit I posted if you wanted the Amp Off mod.

As for you last question, no. You can't connect up 2 USB devices parallel to each other. You need to go to the USB hub first with the cable that comes in from the PC. Then connect up the camera to one USB port and the serial adapter to another. But there's nothing stopping you from using the original webcam USB cable. That's what I do ....

[Davie]

Thanks for the quick reply!

I'll get that done tonight.

[yesyes]

You're welcome. Do ask questions if you have any... ;-)

[Reggie]

Here is the circuit diagram for the chip mod (also known as 'the dead bug' method).

http://www.home.zonnet.nl/m.m.j.meijer/D_I_Y/pictures/spc900nc/4066.gif

link to the webpage it's on.

Philips SPC900NC uncovered

this circuit (like most of the others out there) has been built around a parallel port originally, I can confirm that it works with a 5volt ftdi dongle, with zero modification to the circuit, however you will still need to handle the voltages coming from an rs232 device, it won't appreciate > 5v, a simple voltage divider will do the trick:

Voltage Divider Calculator

[yesyes]

and more importantly, it won't appreciate negative voltages. So a diode in series as seen in the transistor based circuit would be a good idea...

[Reggie]

Doh, yup, I totally forgot about the diode

[Davie]

Well...... this afternoon I unsoldered the "dead bug" and decided to follow the amp off method on the vero board.

All put together but from what ive read the camera should now be very sensitive, mine on the other hand is very dark with a few vertical lines on it. The lines look like light stripes that are out of focus although they do get better and worse when using the lense to try and focus.

I've had a look at all the connections etc. and all looks ok but some things wrong somewhere :/

I'm using SharpCap to mess about with it and theres a settings menu for the LX mode and I've got the com port number for it but have no idea what settings to use for shutter, amp off and exposure.

any help would be gratefully appreciated as usual

[yesyes]

I'm using SharpCap to mess about with it and theres a settings menu for the LX mode and I've got the com port number for it but have no idea what settings to use for shutter, amp off and exposure.

any help would be gratefully appreciated as usual

These are the LX settings for this mod:

Exposure control: RTS

AmpOff: DTR

Shutter control: None

All with the "Inverted" checkbox off.

[Davie]

WoW an answer already!

settings now in but no difference. I'm going to make up a drawing of what ive got to see if anybody can see where ive cocked up

youll have to excuse the use of our daughters coloured pens and my sons "Cars" ruler

[Davie]

No need to show my handy work with colouring pens now as I found a wire in the wrong place. The cam is now working in normal mode but LX mode it captures the first frame and then they are all black.

off to abuse google again.

[Reggie]

Davie, humour me here, go to options, Serial LX configuration and tick the invert boxes, let me know what happens.

[Davie]

I think i might have it working but when i try a long exposure it seems to take long exposures but there are no hot pixels like id expect

Away from home at the minute but will try inverting them when i get home.

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[Reggie]

In general you will know whether it's working because with the lens in, your image should go brighter when you enable long exposure, difficult to spot dead pixels unless you have a lens cap on.

[Davie]

Right.....

Got some time with it tonight early on and have found that it's not working. It does show a very bright screen when the lense is in and in LX mode but when using sharpcap and in LX mode with the exposure set to say 20 seconds it looks like its taking a frame ever 20 seconds rather than a 20 second exposure if that makes sense.

Might be something ive missed in Sharpcap though.

[yesyes]

Davie, that is how it is supposed to work. SharpCap exposes for 20 seconds (see the progress bar at the bottom right). At the end of each exposure you get a new frame that contains the 20 sec worth of light.

With the webcam being a video source it does not stop sending frames during long exposures. It just keeps sending black frames. Then, when the exposure ends, the webcam sends the exposed frame in the next frame, then sends black frames again and so on and so on.... SharpCap hides these black frames from you because it knows that they don't contain any useful data. If you were to open the webcam in a different program (say, Skype), you would see lots of black video and one light frame flashing up at the end of each exposure.

I hope that makes a bit of sense... ;-)

[Davie]

Thanks for yet another reply and a very good explanation of how it works also (every day is a school day)

I didn't explain very well how I tested it. I might still be speaking rubbish, It's happened before beleive it or not

I tested it last night on Jupiter but what I did was this .... I have an EQ2 mount and a single tracking motor so once Jupiter was centred on the screen I started the capture but switched off the motor so that Jupiter would drift off the screen and I was hoping I would get a big long streak across the image as Jupiter gradually ran off the side of the screen from my FoV.

I'm doing this mod in preparation for when I eventually get around to upgrading my mount.

[yesyes]

hmmmm, what did you get instead? I would assume that you should get 20 seconds worth of streak with this method. Depending on your focal length this may or may not be a long streak but you should clearly see some elongation after 20 sec.

On the other hand, Jupiter is not the best object for long exposure. It is very bright and usually you would want LX mode off, the exposure time and gain turned down for Jupiter (if you wanted to see some detail on Jupiter).

Could you post a screenshot and/or a sample exposure?

[Davie]

Here are 2 of the pictures taken in sequence. I had the settings turned up so that Jupiter was very bright for the test rather than trying to get a proper image.

and 20 seconds or there abouts later

To me there should have been a streak of bright light between the two positions.

any ideas?