SPC900 LXmod yesyes style ;-)

[Gina]

Nice neat job, btw RS232 isn't 5v more like -12v to +12v.

That's correct and the reason for the diodes and resistors in the transistor base circuits. Most transistors are rated at around 5v

for the base for negative voltages. The diodes block the -12v from damaging the transistors. The 10K resistors limit the current

for the +12v signal to about a milliamp.

[yesyes]

Nice neat job, btw RS232 isn't 5v more like -12v to +12v.

THAT is a good point.

Real RS232 is +6V and -6V on the Tx and RX lines. But I think these USB to serial adapters have TTL levels on the serial port side.

But as far as I know the status / handshake lines are 5V TTL even on a real RS232.

I have to investigate this more....

[yesyes]

Oh, it's not that easy actually

Wikipedia says:

Voltage levels

The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines. Valid signals are plus or minus 3 to 15 volts; the ±3 V range near zero volts is not a valid RS-232 level. The standard specifies a maximum open-circuit voltage of 25 volts: signal levels of ±5 V, ±10 V, ±12 V, and ±15 V are all commonly seen depending on the power supplies available within a device. RS-232 drivers and receivers must be able to withstand indefinite short circuit to ground or to any voltage level up to ±25 volts. The slew rate, or how fast the signal changes between levels, is also controlled.

For data transmission lines (TxD, RxD and their secondary channel equivalents) logic one is defined as a negative voltage, the signal condition is called marking, and has the functional significance. Logic zero is positive and the signal condition is termed spacing. Control signals are logically inverted with respect to what one sees on the data transmission lines. When one of these signals is active, the voltage on the line will be between +3 to +15 volts. The inactive state for these signals is the opposite voltage condition, between −3 and −15 volts. Examples of control lines include request to send (RTS), clear to send (CTS), data terminal ready (DTR), and data set ready (DSR).

So it could be anything between +-3V and +-15V or even up to +-25V, even on the handshake lines...

The USB to serial probably does +-5V considering that USB provides 5V.

I'll have to connect my oscilloscope to it and see for myself...

Though now the 11V Zener makes even less sense...

[RogerTheDodger]

Aye, the zener only makes sense if the voltage on the transistor leg it connects to on the cam board has more than 12v or so on it... I'll be interested to see what you find.

[Gina]

So shall I

[Gina]

I've now almost completed the transistor circuit board. The other parts have been progressed a bit too. Here are a couple more photos attached.

1. Left - USB hub. Top - USB to RS232. Right/Bottom SPC900 split into it's two parts.

2. The transistor board placed in box with holes for switch plus CCD board of webcam mounted in hole in box.

[yesyes]

Looking great Gina. The serial adaptor board really is a bit smaller than mine.

You are attaching the nosepiece from outside? That's an option I hadn't thought of... ;-)

[NickRose2006]

I normally don't like to buy things on ebay from the UK but for the price it looks like I should. Has anyone from the forums had any problems with this guy?

[yesyes]

I normally don't like to buy things on ebay from the UK but for the price it looks like I should. Has anyone from the forums had any problems with this guy?

Which one are you referring to?

The seller of those hubs?

[NickRose2006]

The guy, I what to make sure I'm buying from someone that will not take my money and run with it. Ebay is a good place to buy stuff but sometimes you have to be careful who you buy from.

[Gina]

I haven't had any problems with thing I've bought off eBay, I have to say. Though I do try to buy from top rated sellers if I can. The USB hubs came very quickly, the USB to RS232 took a bit longer - a few days - but quite satisfactory. I have tested one hub but not the USB to RS232 as yet.

[starship trooper]

Plus if you buy with paypal you are covered.

[Gina]

Looking great Gina. The serial adaptor board really is a bit smaller than mine.

Thanks Yes, it's really tiny

You are attaching the nosepiece from outside? That's an option I hadn't thought of... ;-)

Yes, I made a hole in the box to take the shank of the CCD housing - a close fit - and screw the nose piece in from outside. I'll take a photo or two later. The box I'm using is only about 23mm deep inside. But is about 80x50 so plenty of room to take the other bits. The transistor board and USB hub are going flat and the USB to RS232 is narrow enough to go on edge.

[Gina]

Plus if you buy with paypal you are covered.

Yes, and it's so quick and easy with PayPal - a great service. Watch your security though and use a strong password.

[JKB]

Gina,

just wondering on the orientation of the cam circuits in the box; looking at one of your photos it look like it is rotated 90deg from upright (if that makes sense) If so will it not make it more difficult to know what is where etc when looking at objects? (and controlling mount as dec/ra will all seem mixed up?)

Cheers

Jamie

[Gina]

Gina,

just wondering on the orientation of the cam circuits in the box; looking at one of your photos it look like it is rotated 90deg from upright (if that makes sense) If so will it not make it more difficult to know what is where etc when looking at objects? (and controlling mount as dec/ra will all seem mixed up?)

Cheers

Jamie

Yes, you're right. AAMOF it was a bit of a mistake - I just put the webcam the way it would fit best. Don't think it matters, I'll just rotate the box 90 degrees on the scope. But if there's any problem with that, I have another (same size) box I can use. There is enough room to move the webcam away from the end.

[Gina]

I decided to see if I could put the webcam in the "right" way round. I cut a bit off each plastic pillar to clear the webcam boards and got it to fit.

[Gina]

Here's a photo of the box showing the front with CCD housing just showing on the RHS. The hole on the left is for the switch.

[yesyes]

Looking good... ;-)

Actually a good idea to attach the nosepiece from outside if you can fix the webcam boards in the box somehow. This way you could still attach the original lens if you wanted to use it as a normal camera.

[Gina]

Looking good... ;-)

Actually a good idea to attach the nosepiece from outside if you can fix the webcam boards in the box somehow. This way you could still attach the original lens if you wanted to use it as a normal camera.

ATM it's just a friction fit but I think I'll look into providing a better fixing. I could glue it but I'd rather it was able to be taken out.

[yesyes]

ATM it's just a friction fit but I think I'll look into providing a better fixing. I could glue it but I'd rather it was able to be taken out.

I agree. I don't like gluing these kind of things in place. Stuff needs to be repairable... ;-)

You could use these 2 things that hold the 2 boards of the webcam together. Put 2 longer screws in from the back through the plastic.

[Gina]

I agree. I don't like gluing these kind of things in place. Stuff needs to be repairable... ;-)

You could use these 2 things that hold the 2 boards of the webcam together. Put 2 longer screws in from the back through the plastic.

Yes, that's a possibility. I also thought of using the original mounting holes and a couple of other ideas, but I can hold the camera secure with the nose piece and a thick washer (or two thin ones).

Here's a diagram (not to scale) :-

[Gina]

More photos showing progress - I think it's about finished now (but not tested).

I couldn't find a SPST switch but had a DP centre off (locking) toggle switch so used that. May change it later.

1. Webcam boards with wires attached.

2. Webcam reassembled and transistor board with switch in place.

3. All parts now connected together.

4. All parts in their places.

5 & 6. Exterior of completed unit, with nose piece screwed in ready for use on scope.

[Gina]

Decided to check out what I could... This webcam takes standard "board lenses" so I unscrewed the scope nose piece and screwed in one of my CCTV lenses. Then tried it out again on computer. The lid's gotta come off again... it's not working! I tried it before through the USB hub and it worked OK. Now the webcam software can't find it - "No Device Connected" error msg. With all the movement I think it's likely that a wire has broken off. And here I was thinking what I was going to build next!

[Gina]

Can't see any wires off. Diagnostic time!...

Test 1. USB recognition.

Result - 2 of the 3 USB devices detected. The USB hub and the USB to RS232 devices but NOT the Philips SPC900NC webcam! So closer look required.

Watch this space!