A poor man's Argo Navis

[alistairsam]

yep, just wrote to far circuits for the circuit board and programmed chip. not sure how long it takes to reach here though.
making a similar DSC was purely out of my own interest and newfound love of the picaxes.
since dave's ek box has its own ascom drivers, can it therefore be used with software such as CDS, phd, stellarium etc to drive the steppers, read position and control the scope? I know bartels system controls it, but wanted a windows based controller as well.

[bojan]

Yes, as long as there is ascom driver, you can use it with other apps.
I know it can be used with CdC.

Also, when buying components, you do not have to stick precisely to values..

As for 4MHz oscillator, you don't need one.. just a 4MHz crystal (or ceramic resonator) will work (with couple of pF load, of course).

[Rod]

Originally Posted by alistairsam

can it therefore be used with software such as CDS, phd, stellarium etc to drive the steppers, read position and control the scope? I know bartels system controls it, but wanted a windows based controller as well.

Hi Alistair,

Just to clarify. The Bartels system only uses the EK box so your encoders keep rack of the scope's position. Handy if you use clutches or if your scope gets knocked out of position or a motor stalls. But you can run the system without encoders quite successfully. Likewise to control your Bartels controlled scope with a planetarium program like Carte du ciel you don't need encoders just a serial connection between the laptop with the planetarium program and the laptop with the DOS based Bartels software. You can use a serial bluetooth adapter (for a PC or a PDA) or serial wifi adapter (for an iphone) to avoid using a cable connection.

I use carte du ciel (and astromist (PDA planetarium) to control my Bartels system. I don't have encoders. I will add them one day when I get around to building clutches. In the meantime I just move the scope either with the handpad or by sending goto commands from the laptop or PDA.

BTW you can also use a the old DOS version of Guide to control Bartels. No extra laptop is then needed. It looks a little basic by comparision but it works well.

Rod.

[alistairsam]

Hi Steve,

will a PS2 mouse work with the bartels system or does it have to be serial.
in your first post in this thread, you've drawn lines on where you've cut away the sensors. does this mean you're using the remaining circuitry and just joining the tracks that are cut?
also, do these sensor pairs have one or two led's and detectors, or just one led and two detectors, noticed that there is only one lens bubble in the image. so how do you get quadrature or direction?

if the ps2 mouse is compatible, do we just specify in the software to use the detected mouse as the encoder as I don't see any input in mels circuit to accept optical encoder signals.

[kinetic (Steve)]

Alistair,

you need to do more reading.
The Bartels system accepts a serial/PS2 mouse as encoders but you
have to enable it first in the config.dat file.

The detector (the black device in the pic attached) has 2 detectors.
It detects either a rising edge one one detector or a falling edge on
the other.
http://www.iceinspace.com.au/forum/a...se.php?a=54746
Whichever one it received first determines direction of the count.
That's quadrature detection. Read up a bit more on it.
This thread is quite clear and straightforward including the pics.
Mel's site is very easy to digest a step at a time too.

Steve

[alistairsam]

Steve, I have read through Mel's site several times and read on quadrature encoding principles and circuits a lot, but not through mice internals. i was looking for pinouts of the detectors that I later on found and realised that there are two detectors and one LED.
I must have missed crucial sections on Mel's site, so will go through it again.

[bojan]

As Steve pointed out, everything you need to know is on Mel's website (have a look at links as well).

As far as mice are concerned, of course you need quadrature input (otherwise there is no way computer can tell in which direction the mouse is moved.
So, at the sensor level, you have quadrature signals (two channels, one LED + two photo sensors.. or sometimes two LED and two photo-sensors, this depends on encoder design) for each axis.

At mouse interface level, you have the conversion of those quad inputs into serial data stream RS232 or PS2.

However, as I pointed out several times in my posts, I think there is a software bug somewhere (mouse driver or scope executable), sometimes resulting in overshots if telescope is unintentionally moved while scope.exe was in tracking mode. I had this problem with mouse driver in 30% of cases.. and even once per night I would consider one too many. The problem never occurred if I stopped the tracking, manually moved the telescope to a new position, and then turn on the tracking.
And, after switching to Ek's box, I never observed that problem again.
That is why I recommend using EK's box as an interface between quadrature signals generated by encoders and computer running Mel's software.

[alistairsam]

Originally Posted by bojan

At mouse interface level, you have the conversion of those quad inputs into serial data stream RS232 or PS2.

However, as I pointed out several times in my posts, I think there is a software bug somewhere (mouse driver or scope executable), resulting in overshots if telescope is moved while scope.exe is tracking mode.
That is why I recomment using EK's box as interface between quadrature signals generated by encoders and computer running Mel's software.

Hi Bojan,

i will look at the site and links again.
I was trying to figure out how the sensors in mice worked as I could then use Ek's box with sensors from the Mice rather than getting new sensors.
else will try the sensors you posted from jaycar.

just wanted the detector pinout which I later found was very simple, on three terminal detectors, middle pin is +5v, the two pins on either side are the channel outputs and are connected to ground by 10k resistors.
i connected a scope to the detector and was able to see the level move up with external light, but was'nt able to get the mouse LED to work adequately. interrupting the beam did cause some spikes but very low level spikes.

[bojan]

You have to be aware that the size of slots in mouse encoder wheel are suitable for the photo detectors separation (yes, you are right, those are just phototransistors with collectors connected to +V and emiters are outputs (via 10k pull-down resistors).
Mouse led is just a led.. (IR) there should not be a problem.. only you have to feed it with adequate current (10~20mA), otherwise it won't activate the transistors properly

[kinetic (Steve)]

Originally Posted by bojan

You have to be aware that the size of slots in mouse encoder wheel are suitable for the photo detectors separation

Absolutely right mate.
That's why the original choice for mice to salvage was limited to the finer
and higher resolution mice shown in the pics at the start of the thread.
These optical wheels and TX/RX pairs match the larger substitute
wheels. Some fine adjustment was needed to get the pairs lined up
exactly , see the adjustment plates? ( I checked with an oscilloscope
first and then watched the counts in Scope.exe.