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Woohoo! It lives, Igor!

I did wonder why the tests to turn the motor an entire revolution weren’t actually turning the spindle very far until I remembered that it has a 27:1 gearbox on. Easily missed, that one 🙂 And I have the buttons cross-wired as compared with the LEDs, but that’s just a question of switching a connector around the other way on the pin header I think. And the buzzer now works, though I don’t recall actually doing anything to fix that.

So now I need to decide which telescope I’m going to put it on and make up a suitable bracket. Then probably re-balance everything thanks to hanging another half kilo of motor on the end of the OTA.

Oh, I almost forgot — need to adjust the current limiting resistor on the stepper driver board too.

I have some 24AWG cat5 patch cables that are no use to me any more, partly because they’re not good enough for gigabit ethernet and partly because they’re not assembled very well (they were supplied with Sun Microsystems kit, too; you’d think at the prices they used to charge they could afford to supply decent patch cables). I’ve chopped a length of about a metre out of one and soldered that into a DB9 plug. Looking at the tables for stranded 24AWG a single conductor should be good for 1.4A, but obviously the other wires and insulation in the sheath will lower that. I think it should at least be ok for testing whilst I find something else with larger conductors. I can’t tell what size the wires are on the motor body. No larger than 22AWG I’d say. Certainly not as big as 20AWG. Obviously they’re in free air though.

Finished the lid. No photos yet, but I’ve run some of the tests. The LEDs and pushbuttons appear to work fine, though the buzzer doesn’t. I wasn’t entirely happy about my connector for the buzzer though, so I may need to remake that.

Next I need to connect 12V power and rig up the motors to test them. There’s a bit more work involved there though as I’ve decided to move away from using 5.5/2.1mm power connector plugs and switch to two pin GX12 connectors. I don’t have anything with a GX12 plug on at my desk though, so I shall see if I have enough bits to make an inline 5.5/2.1mm socket to GX12 converter in which case I can just power it from a standard 12V wall-wart.

Then I need to find some suitable four-way cable to connect up the motors. I’d forgotten about this, I have to admit. I suspect cat5e might actually be sufficient. I think it should be good for an amp per conductor and the motors aren’t rated that high if I recall correctly. The only problem is that it’s so awkward to work with for soldering.

Mostly done and in a box now. Just need to finish making up the lid with the buttons and LEDs on.

I’ve just realised that I forgot to put in the current-limiting resistor for the buzzer (that’s what I assume it’s there for, anyhow). Probably because it doesn’t appear on the stripboard layouts which aren’t always kept up to date with the most recent changes to the design. I assume it was added later. Fortunately there’s room to move the pin header for connecting the buzzer further away from the Nano and I can just drop a resistor in across a break in the track.

This morning I grabbed a scribing tool from the workshop and ran it down all the “blank” sections of the stripboard on the first board a few times to try to clear out any tiny drops of solder that might have been bridging tracks. I also found one place where my soldering might have unintentionally bridged two tracks though I couldn’t tell for certain. If there was a bridge then it would have pulled the RESET (pin 3) input to ground. As that input is active low I imagine it could well have caused the behaviour I was seeing. I removed the solder using some braid, cleaned between the tracks and remade the join just to be sure. I now have a Nano sitting in the socket and behaving as I would expect 🙂

Now as if it’s not enough having to deal with my eyesight not being what it was in my youth, I can’t remember where I put my stepper drivers either 😀