DIY on yesyes DIY and astro

8 inch lightbox MK I

Mon, 01 Jan 0001 00:00:00 +0000

yesyes DIY and astro > DIY > 8 inch lightbox MK I

I wanted to get started with astro photography, so I needed a light box in order to shoot some flat frames. I’ve seen a few different designs around but I decided to see whether I could use the background lighting of an old 14" laptop TFT panel I had lying around. Some time ago I had already converted this display panel to work like a “regular” flat screen monitor.

The first thing to do was to check whether the actual TFT display can be separated from the background light. So I started taking the panel apart and found that this was indeed possible and rather easy to do.

Here is a picture of the background light with the TFT panel removed:

View from the back with the VGA controller board and the inverter board (power supply for the background lighting lamp):

This is the actual TFT panel that I removed:

It still works as well: ;-)

I think I’ll keep that somewhere safe. You never know when you might need a transparent TFT display… :D

The next step was to see whether the light still works.

This is when I discovered the first (small) obstacle. Since there was no video signal, the controller board, which also controls the power to the lamp, went into power safe mode a few seconds after switching it on. I had to be really quick taking the picture above.

So I checked the pin-out of the inverter board. Thanks to the Internet that was rather easy to find. It turned out that the inverter board requires 12V for generating the actual power for the lamp (which lies in the region of 600V, by the way). The inverter has another 2 inputs; one is the lamp enable pin and the other controls the brightness of the lamp. Luckily, no voltage on the brightness means maximum brightness and supplying higher voltages dims the light more and more. Since I wanted maximum brightness, I could just ignore that pin.

Not so lucky with the lamp enable. Unfortunately that input requires 5V to switch on the lamp. So I had to get 5Volt from somewhere in addition to the 12V for the lamp. I decided to do it properly and built a small circuit with a fixed voltage regulator (78LM05), a diode and 2 capacitors. This ended up looking like this:

Then I protected it with a bit of heat shrink:

A quick test shows that the light now stays on as long as I want:

OK, that’s the “electronics” sorted out.

The stuff that distributes the background light evenly behind the TFT panel was made up of several (more or less loose) sheets of plastic foil that needed to be protected. So I replaced the TFT panel with 2mm thick clear acrylic sheet that I had cut to size from ebay.

Then I put the metal frame back on. The 2mm acrylic was a bit thicker than the original TFT panel but the frame just fit fine.

Next step: design a case / housing for the panel that allows for easy mounting onto my 8" Newtonian telescope. I decided to use black 5mm thick acrylic sheet for the housing. That would look best, be cheap and easy to put together.

Here’s the “work sheet” where I designed the casing and calculated the dimensions of the acrylic pieces I would need.

I’ve ordered the acrylic on ebay and had them cut to size. Here’s what I got:

At this point I realised that, if I wanted the base sheet removable, I wouldn’t be able to build the box from the base sheet up as I had planned. I would have to start from the top and build it without the base attached. It was a bit awkward but I managed to do it. Lesson learned for next time…

In order to “glue” the bits together I use a method called solvent welding. You just hold the bits together at a right angle and apply a bit of solvent. This “melts” the acrylic of both pieces and dries up rather quickly again. A few moments later the 2 bits are basically one piece of plastic and the solvent has completely evaporated. No ugly glue bits remaining. Because this needs to be done very quickly before the solvent dries up I wasn’t able to take any pictures of that process. Here is a Youtube video that shows it nicely: How to glue Acrylic

Since I used very glossy black acrylic it turned out to be very difficult to take decent pictures of it. I hope you can recognise at least some of the shapes.

Here is the first part done:

The stains you see is what happens if solvent drops get onto the acrylic. So be careful!

Making progress:

The panel then fits in like this. My digital camera really had a hard time trying to get the lighting right.

Next day: Now that the glueing is definitely dried up and hardened I can drill some holes and glue some nuts in so that I can then attach and remove the acrylic sheet at the back with screws.

I’ve put the back plate on the box and drilled one hole (diameter just a little bigger than the screws that are to be used) in the right place through the back plate and about 1cm into the box walls. Then I put a long screw in to keep the holes aligned. I repeated that making 6 holes.

Then I used a bigger drill and widened the holes in the box walls.

The holes needed to be big enough so that I can glue in these….

… with that:

So I mixed the glue and filled some in each hole. I also put a screw in each nut. This makes it easier to hold the nut and move it so that it’s straight. It also prevents glue from getting inside the nut.

When the glue had set but not completely hardened yet, I used a standing knife to get rid of the excess glue.

Here it is with all 6 nuts glued in, ready to attach the back plate:

Here it is closed:

Now all that was left to do was to insert the panel …

… tuck away the “electronics” …

… and switch it on:

Yay!! It works… ;-))

Next I got out my scope and tried the lightbox on the scope:

Looking through the focuser draw tube it looks like the lightbox would make a good collimation tool too.

Finally, I couldn’t resist taking a few flat frames to see what they would look like.

This is one of the unmodified flat frames:

OK, looks boring, I know. To show that there is indeed some information in it, I have stretched the histogram to exaggerate the subtle differences in the original image. Out came this:

Not had enough pictures yet? There are a lot more pictures of how I build the lightbox in my gallery here:
http://picasaweb.google.com/chris.yesyes/Lightbox#

Motor Focuser

Mon, 01 Jan 0001 00:00:00 +0000

yesyes DIY and astro > DIY > Motor Focuser

Motor Focuser

I can now remotely control almost all the functions of my telescope and its mount. But for focusing my DSLR attached to the telescope I need to go to the scope with the laptop and drag the USB cable with me just so I can see the LiveView image of the camera on the laptop while adjusting focus on the telescope.

So I need to motorise my focuser so that I can focus remotely. This is what this page is all about.

I have chosen to use the SGL_Observatory_Automation focuser project. This is an Arduino based motor focuser with ASCOM driver on the PC side. Links to the project are at the bottom of this page.

This is an ongoing project and I will document my progress on this page.

Here is what I have so far (as of 9 September 2011):

One stepper motor

A handful of timing belts and pulleys

and an EasyDriver stepper driver board

Here is the first test to drive the stepper from an Arduino. IT MOVED!!! :-)

First update 12 September 2011

Over the weekend I have worked on the mechanics. I made a bracket that allows the stepper motor to be attached to the focuser. Another bracket holds the EasyDriver board and the 4P4C connector socket.

Here is the stepper attached to the focuser. This also shows the timing belt and pulleys.

The next step was to make a bracket that will hold the EasyDriver board and the connector

This is the whole stepper and driver module

And here is everything put together

It does look a bit like a steam engine, doesn’t it?

I’ve had some problems with the stepper not being able to turn the focuser occasionally. The problem seems to be the 10:1 gearing on the other side of the shaft not going very smoothly. So I took that apart and cleaned and re-greased it. I was surprised by how that gearing actually works. I was expecting to see a few little gears. Instead I found this:

There were some metal bits/filings in there that probably got in between the metal piece on the left and the bearing balls preventing it from turning properly. I cleaned that out and applied new lithium grease. I think it was also put together too tightly requiring more torque when turning. This is OK when operated by hand but the stepper didn’t quite cope. I’ve left it a little more loose when I put everything back together. It is now turning much better but still has moments when the stepper doesn’t have enough force and slips.

I’ve ordered a bigger pulley for the focuser side and a longer belt. Hopefully a higher gear ratio will fix the remaining issue.

Regarding the EasyDriver board, I have been told that it would be rather dangerous if the stepper motor got disconnected while the EasyDriver was powered. Apparently this would instantly destroy the driver chip. That is why I decided to put the EasyDriver board right next to the stepper. I didn’t want to take the risk of accidentally unplugging the motor cable before powering down the driver. After a long night on the scope you never know…

The Arduino controlling the stepper will then be located in my Power and Data Box. I need 4 wires between the Arduino and the EasyDriver - 12V for the motor, Step and Direction signals and, of course, Ground.

Next update 14 September 2011

Yesterday the bigger pulley and longer belt have arrived. I installed them on the focuser and now everything is moving fine. There is no more slipping.

(There is a video of it moving on the Picasa gallery, see link at the bottom of this page)

The smaller pulley on the stepper has 32 teeth and the larger one on the focuser has 60 teeth. This almost gives a 2:1 gear ratio. The belt is a 100 teeth MXL belt. The shaft centres are 54mm apart.

Next update 16 September 2011

Last night I build the “controller board”. It consists of an Arduino Nano and a simple relay circuit. This is the test setup. The finished version will not feature sello tape to protect against short circuits!

The plug on the left is the input for the 12V supply for the stepper / EasyDriver. The 4 wires on the right go to the EasyDriver / focuser. The blue board is the Arduino Nano (it is even smaller than the already small EasyDriver board!!!). The stuff above the Nano is the relay and it’s circuitry (a NPN transistor, a 6k8 resistor and a protection diode). This relay switches the power to the EasyDriver on and off; controlled by software in the Arduino. The Arduino itself is powered from the USB port.

Here is it a little closer:

I have created a circuit diagram which is available for download at the bottom of this page.

Later that night I connected everything to the computer for the first time. After a few small problems I got everything working just fine. I also changed the Arduino program (called a sketch) so that the EasyDriver is powered down automatically after 20 seconds of inactivity.

Next update 18 September 2011

Over the last few days I have made more progress.

The Controller board has been installed inside the Power and Data Box. I used 4 5mm brass hex stand-offs to hold the board in place:

Here it is installed inside the Power and Data Box. It was a slight oversight to install it so the USB connector is at the top. I ordered a different cable with an angled mini-USB connector.

On the output side of the box I added a 4P4C (RJ10) connector for the cable going up to the focuser.

Next I mounted the focuser back onto the telescope.

Then I added the new cable to the “cable management”

So this project is almost done. All that is left to do ist to test it properly on a clear night…

Next steps:

- test during a proper imaging night

As usual, more pictures in my Picasa gallery here:

https://picasaweb.google.com/117034922665750406576/201109MotorFocuser

External links

The SGL Observatory Automation project

Yahoo! discussion group
http://tech.groups.yahoo.com/group/sgl_observatory_automation/

Project discussion on Stargazer’s Lounge (SGL) forums
http://stargazerslounge.com/diy-astronomer/106144-arduino-focus-control-cloud-sensor.html

EasyDriver information

http://schmalzhaus.com/EasyDriver/

**
Downloads**

Motor Focuser full scematics (PDF)

Observatory Clock

Mon, 01 Jan 0001 00:00:00 +0000

yesyes DIY and astro > DIY > Observatory Clock

Observatory Clock

Images of the testing phase and build phase of my Observatory Clock are here:
https://picasaweb.google.com/117034922665750406576/ObservatoryClock

The usual description will follow soon.

Features:

- 8 digit 3 inch 7-segment display
- 8 8x8 LED matrix displays for alphanumeric display
- Arduino Duemillanove (2009) microcontroller
- RTC (Real Time Clock) module (keeps track of time while clock is off)
- external NMEA GPS receiver (to get accurate time and local coordinates)
- IR remote control
- LDR (light sensor) automatically adjusts display brighness (software controlled)
- vibration alarm using rumble pad (game controller) motors
- 4 status LEDs

Observatory Clock Full Schematics (PDF)

Philips SPC900 webcam LX and AmpOff mod

Mon, 01 Jan 0001 00:00:00 +0000

yesyes DIY and astro > DIY > Philips SPC900 webcam LX and AmpOff mod

Philips SPC900 webcam LX and AmpOff mod

I have finally done the LX and amp off mod on one of my SPC900 webcams. With the LX mod the webcam can take L ong eX posures of several seconds controlled by a computer via serial port. Using a serial port status line (RTS) the computer can open and close the shutter of the camera.
The AmpOff mod disables the image amplifier; also controlled via another serial port status line (DTR). If left on, the image amplifier can cause a red-pink-ish glow on long exposures.

I wanted as few cables as possible, so I made a version that really only needs one USB cable to the modded cam. Most other mods I’ve seen required a separate serial cable between computer and camera.

Ingredients:

1 SPC900

One LX and amp off mod circuit

One 4 port USB hub circuit board

One Prolific PL-2303 based USB to serial converter

And one ABS project box of just the right size

Result: One LX and amp off modded SPC900 that only requires a single USB cable and is not that much bigger than the original webcam.

This is what Windows detected when the modded camera was first plugged in:

The switch disables the mod and puts the camera back in normal mode, as if nothing happened.

Choosing a USB to serial adapter can be a bit tricky. For these mods you need one that supports the handshake lines RTS and DTR, not only the serial data lines (we don’t even want to send any data). I also wanted one where Win 7 64bit drivers were available.

I found out that the Prolific PL-2303 chip fits the bill. So any USB to serial adapter cable with that chip will work fine.

The circuit board is in the serial plug of the cable. So I carefully cut it open and unsoldered the USB cable (make a note of which wire goes where). The most difficult part is to get rid of the DB9 plug without damaging the solder pads on the PCB. Once you got it off you got a nice small USB to serial PCB.

The USB hub board was obtained in a similar fashion. I specifically selected a USB hub model that had external USB plugs (see 3rd picture on this page). This makes the PCB a lot smaller as it does not have to accommodate the USB sockets. I just opened the hub and unsoldered the USB cables.

Here is the schematics for the mod:

Please note there is a mistake in the circuit diagram. The diodes are 1N4148, not 2N4148!

More pictures here:
https://picasaweb.google.com/chris.yesyes/201107SPC900LXAndAmpOffMods#

Discussion of this project on the Stargazers Lounge forums
http://stargazerslounge.com/diy-astronomer/148315-spc900-lxmod-yesyes-style.html

Larger version of the schematics image (JPG)

Power Supply

Mon, 01 Jan 0001 00:00:00 +0000

yesyes DIY and astro > DIY > Power Supply

4 Voltage Bench Power Supply

I’ve built myself my own universal, adjustable bench power supply.

The main reason I built it is to experiment with TFT backlight panels that I use for my lightboxes.
I needed 5V and 12V to play around with the inverter boards and figure out their pin-out. I considered buying a bench power supply. But prices were too high, especially for ones with adjustable voltages. So I decided to build my own.

This one has 4 outputs. One 5Volt, one 12V and two individually adjustable outputs going from about 1.5V to 19.5V. Each can draw up to 1.5Amp with a total of 3.5A for all together. The input is a standard replacement laptop power supply 20V, 3.5A. With a stronger external power supply the total output current can be higher, up to 1.5A per output. But currently the 3.5A is more than enough.

Each of the adjustable outputs has its own little voltmeter built in.
The fixed voltage regulators are based on a 7805 for the 5V and a 7812 for 12V. The two adjustable regulators are based on one LM317 each.

And of course I just had to built an acrylic case for it. Here is the pictures of the various stages of building and the finished product.

This is the board for the fixed 5V and 12V

Starting with the adjustable regulators.

Both regulator boards finished. The smaller board is what I call the Power Distribution Board. ;-) It has the power input, connectors for the main switch and two outputs that go to the two regulator boards. It also has another small 5V regulator that provides the voltage to run the voltmeters.

This is going to be the holder bracket for the two voltmeters and two potentiometers.

The rear view of the mounted voltmeters. These were ready. I ordered them on ebay for a few quid; from Hong Kong. These are blue displays!!! ;-)

At last the acrylic for the case has arrived

Here with the threads glued in.

The thinner wires go to the voltmeters.

Telescope Power and Data Box

Mon, 01 Jan 0001 00:00:00 +0000

yesyes DIY and astro > DIY > Telescope Power and Data Box

Telescope Power and Data Box

I have been busy again ( I just can’t stay away from the shed )

This time it’s a Power and Data Box for my telescope. It will be mounted on the pier once I have an obsy. Until then I’ll just hang it from the eyepiece tray under the tripod.

Features:

Output:
- 10x USB in 2 5x USB groups
- 6x 12V socket
- 4x 5V socket
- 2 channel PWM dew heater controller
- 1 serial port (USB to serial adapter)
added later:
- 7.4V power supply for my Canon EOS 1000D DSLR camera
- output for motor focuser

Input:
- kettle style mains socket
- 2x USB-B socket

The heart of the box is a 12Volt 20A switched power supply. It powers the 6x 12V sockets, the dew heaters and a 12V to 5V 5A voltage regulator. That 5V regulator powers the 2 USB hubs, the 4x 5V sockets and the fan.

There are 2 completely separate (apart from the power supply) 7 port USB hubs with separate input sockets. I have kept this separate in case I ever needed to connect 2 PCs (one guiding, one imaging for example). I hope the common power supply does not pose a problem.

This shall be sufficient for the forseeable future.
The only thing I know I forgot is a 7.4V power supply for the EOS 1000D. I’ll add that.

Here is the finished product:

And this is what it looks like inside:

This took me 18 hours to build (excluding planning time) ;-)

Update

I have added more functionality to the box. The 7.4Volt power supply for my EOS 1000D camera is now also in this box. The connector is a 6.5mm phono plug to avoid confusion with any of the other 5V and 12V outputs.

The power supply is at the bottom right on this picture:

I have also added the control circuitry for the motor focuser to the box.

This is the circuit:

And here it is installed in the box:

This shows the 2 extra connectors

Further, I improved the wiring on the main power supply and added a few more wires on the 12V rail to support higher currents.

Before:

After:

As usual, more pictures of the build in progress here:
https://picasaweb.google.com/chris.y…werAndDataBox#

DIY on yesyes DIY and astro

8 inch lightbox MK I

8" Lightbox MK I

Since I used very glossy black acrylic it turned out to be very difficult to take decent pictures of it. I hope you can recognise at least some of the shapes.

Motor Focuser

Motor Focuser

The SGL Observatory Automation project

Observatory Clock

Observatory Clock

Philips SPC900 webcam LX and AmpOff mod

Philips SPC900 webcam LX and AmpOff mod

Power Supply

4 Voltage Bench Power Supply

Telescope Power and Data Box

Telescope Power and Data Box