Lockdown turntable and lathe - a DIY project

[A1beats]

40.jpg
The lathe, with the 'coin exciter' head mounted on its transport mechanism. When the head is fully lowered on to the disc, the stylus is at a very slight trailing angle (2 - 4 degrees from vertical).
41.jpg
Close-up of head transport. The counterweight is a collection of 'penny washers' held in place by two 6mm collars.

This post brings the 'project report' up to date (7 May) - I'll document my work henceforth in subsequent posts to this thread. Thanks to KNOP and Grooveguy in particular for their careful documentation of their own projects, and for making their findings public!

David

Hi David, Could u share info where u got the motor and linear pulley's and belt?
Thanks

Arnold

[pentlandsound]

Hi Arnold,

Here's some places where you might find what you require:

Pulleys: https://www.motionco.co.uk/grooved-pulley-20mm-round-belt-p-458.html
Depending on the diameter of the shafts of your linear rail and motor, you may need either or both of these:
https://www.motionco.co.uk/bore-reducer-bore-10mm-long-p-427.html
https://www.motionco.co.uk/bore-reducer-bore-10mm-long-p-430.html

Belts: https://www.ebay.co.uk/itm/394808486184
Endless 'O-rings' seem to work best. I don't think this was the exact listing on eBay, but it's very similar. You need a belt to fit your pulleys (3 mm CS), with the ID/OD (inner/outer diameter) chosen depending on how far apart your linear rail and motor are. Hint: don't make the belt too tight.

Motor: I have a Jugetek stepper, model 14HY0007-20B. I chose a NEMA-14 motor because it's fairly compact and sits more or less flush with the V-Slot rail, but there's no real reason that you couldn't use a NEMA-17 one - they are more common and easier to find.

Hope this helps!

David

[Fattcamp]

Hey guys,

I'm putting my Digikey order together and have a question on the capacitor values from the hand-drawn diagram (https://github.com/dn784533/lathe_guide/blob/main/LR_controller_circuit.png). Are these pF or nF? I doubt they are uF! These are for the 390 & 330 values on the bottom of the diagram:

Arnold: Sorry for the late reply. Had to take a break from the project for some family stuff. Appreciate Dave providing the links. I ended up getting the motionco stuff linked above and went with these O-rings on e-bay:https://www.ebay.ca/itm/335088185273?var=544315519791

Thanks guys,
Dave

[pentlandsound]

Hi Dave,

The 330 and 390 capacitors on the hand-drawn diagram are indeed uF. I had read somewhere that a 100 uF or so cap may be placed between 5V and GND to smooth out the supply to an Arduino; the 330 and 390 uFs were just two spare caps I happened to have that were near enough. Depending on your power supply and stepper motor, you might not need the capacitors. If memory serves, the Arduino in my system was being reset by spikes in the supply every time the stepper motor started up, and the capacitors were an attempt to get around this. It worked!

David

[Fattcamp]

Hi David,

Thanks very much for the reply. I can't seem to find non-polarized & non-smd/smt 330uF caps through my standard sources (Digikey/Mouser). Are these polarized or is there something I'm missing here? I was just looking for standard film or ceramic axial or radial caps but maybe I'm looking for the wrong thing. There's lots of SMD/SMT but I'm just going to be working with standard stripboard as per your build.

Thanks again,

Dave

[grooveguy]

Hey, Dave, not that familiar with this project, but looking at the perf-board layout it would appear that both those caps are across the power supplies, so you do want normal-old polarized electrolytics. I, personally, would also put a 0.1uF ceramic cap across the same points, as big 'lytics don't do that good a job at really high frequencies. And I question the need for the oddball-value 390uF, I would think that another 330uF would do just fine, or put in a 470uF if you feel so inclined. Caps across the power supply are simply noise-absorbers and oscillation-preventers for the most part. As with most electrolytics, be sure that the DC working voltage is higher than what they'll sit across; 50V for both would be my choice.

[Fattcamp]

Thanks for the info & explanation! Much appreciated. Onwards with my orders!