Another EQ3 stepper mod

[Horwig]

Watching this with interest, I'm thinking of going EQastro on my old EQ5.

 

Huw

[m000c400]

Recently I refreshed my old EQ3 for wide fielding.  Although I had a previous version going on the EQ3, and have done a custom PCB version for my EQ5 I took a few moments to see what was new.  The board below is about 7cm x 6cm and takes an Arduino Nano and 3 stepsticks ( Obviously you only need to populate 2).  It seems to sell from about a fiver on the worlds favourite auction site( depending on how long you want to wait)  but makes a very quick, no soldering, almost "off the shelf" solution.  I couldn't find a nice case, but my 3D printer sorted that for me. The only real weakness is the low max stepping rates on 16Mhz processors, but mine is for wide field so the I can afford to step quite slowly. 

Search ebay for "cnc shield v4" if you are interested.  I took a few moments to make my software fully configurable, so now supports a whole spectrum of options and cpu types. One day I may even "finish" it, but we all know that day will never come!!!

 

 

[furrysocks2]

23 minutes ago, m000c400 said:

Recently I refreshed my old EQ3 for wide fielding  ... Search ebay for "cnc shield v4" if you are interested.

Nice - next time...

[furrysocks2]

Progress tonight.

Old 18V laptop power supply (actually puts out nearer 21).

 

 

 

I used the Big Easy Driver sample sketch and after quickly calculating how many microseconds per microstep I should use, I got the scope tracking pretty well.

 

 

I don't know how much of this is poor time keeping on the Arduino and how much is me not aligning the scope very well.

Regardless, I'll get the other axis connected this week sometime.

 

How exciting... never tracked before but it works!

[furrysocks2]

Current/voltage/heat etc is something I'm a bit sketchy on and a little nervous about, too. There's a mini pot on each board to set current - the silkscreen indicates the wrong rotation direction but I knew that before I turned it last night.  I'm using 18V supply but stepper datasheet says "2.8V" - I read somewhere if I limit the current I'm ok up to 20x rated voltage, so laptop power supply seems ok - it's >2A. I keep each stepper under 1A (hopefully much less, if I'm driving at 18V), power supply is good. Maybe even for focusser too. I can get little heatsinks for the driver chips on the boards, and I'll measure the current coming out of the laptop supply with just the RA.

 

Overall though, with two driver boards soldered up and two motors installed on the scope already, just few more wires, install OnStep, configure ASCOM and I'm into testing a full EQ "goto"... that's pretty exciting stuff!