2DOF Seat Mover - First Build

70:16 would leave you about a 1.14° margin on either side of your +/-40° travel. If the pulleys are using set screws instead of something like a keyway, you might want to use some form of limit switch also. If one of your pulleys does start to slip, then that small margin doesn't leave a lot of room before the output from your sensor flips.

Limit switches are a good idea anyways. We tend to forget how much power these setups have until we see the amazing amount of damage they can cause when something runs out of control. I am very conscious of the fact that I've not installed any on my new seat every time I power it up. (They are in the works)

So I need to increase the number of teeth on the pot, that will reduce the amount of rotation. Limit switches sound like a good idea too. Im still searching for a PSU as ideally it would be easier with a single unit that I can add an emergency stop to.

An 18T pulley would give you about 6.25° of margin on either side without reducing your resolution too much. I don't think they make an 17T pulley.

I did look at the normal electronics distributors I use at work that have European branches but none of them seem to have the LRS supplies available for the U.K. Amazon might be an option.

Yeah I can get the 350 on Amazon but nothing higher I believe, and I dont want to go for a chinese unbranded supply.

How do you work out the angle in relation to the gears? If I need to go safer I can get a 24t too.

70:18 is ~3.89:1. 360° / 3.89 = ~92.545° so that is how far your axis would have to move to max out your sensor. Subtract the 80° your planning on your axis moving then divide by two and that is the amount of margin you have on either side of your range.

I did some more looking for the PSU. Try OMC-StepperOnline They are showing 4 of the LRS-350-24's in UK stock. lrs-350-24 don't forget to click on the ships from UK button.

Thank you bud, you have been a great help so far, as has @noorbeast and it really is appreciated. The final ally parts are arriving tomorrow so I will post up some progress pics.

I've just checked the link and they have the LRS 600, it would be nice to go single PSU but at 13.5A for each motor, I guess its not enough.

The LRS-600 ships from China, they were showing UK stock for the LRS-350 so you should be able to get them quicker (and hopefully without any issues with customs or extra taxes and such).

A single supply is nicer, but the dual supply will be more robust from the motor's peak demands.

Thanks Gefahren, I've placed an order for the 350s. Just the pulleys and motor arms to sort now!

Alloy arrived so I have been building to base to get a rough idea on layout. Ive 3D printed some arms for now ready to fabricate as needed. Next will be to get the top frame on and the bearing arms connected.

A quick query too, is there much difference in mounting the motors, more inside the frame than outside, given the arms start position will be the same? Just looking to make it as compact as possible.

Yeah @noorbeast I will take another look now it's pretty much all built, just didn't know if there was any other reason people mount them differently, maybe just personal choice etc.

A quick update then.

The PSUs are here and I've spent the morning bolting up the base frame, making sure it's all square and tight.

For the motors, I have added in a bracket either side for extra support, with some protective rubber on the top to just cushion them a little.

The motors are mounted, by calculation in the correct place for a 60mm CTC arm. I have also 3D printed a custom dual IBT mount that will have a fan then added over the top. This was taken from an existing design and I am now waiting for some M4 T Nuts to arrive to bolt it in place. THe PSUs will also use the M4 T Nuts, I will be printing the brackets for these over the weekend to get them tucked under the frame.

I am now just waiting on the CTC arms to be made, £220 I have been quoted by a friend, but his CNC work is amazing. For gears, I am still looking around, the 70t gear I found was MXL, which I believe is different to GT2.

Hi. I did similar design with my rig. Maybe you will find it usefull https://www.xsimulator.net/community/threads/simlab-gt2-to-2dof-conversion.13948/
Today I would not use the drivers I have used but the more powerful one also from aliexpress that are rated 40A or something. Have never had problems with tripping the power supply with my design with bridge rectifier.

Thanks @iLLuac4, your thread is one that this is based on roughly, the IBTs are rated at 43A I believe.

Am I right to assume that with the 3 outputs on PSU i can use one for motor and one for a 24v fan to cool the IBTs?

For fans I have used https://fr.aliexpress.com/item/1005006602105635.html that is 12v. So I have used step down converter to lower the voltage from 24v to 12v. like this https://fr.aliexpress.com/item/1005005870392716.html

I have only one power supply. So yes you can connect fans to the same terminals as motor.
And yes I have lowered the voltage output to like 22v and then also diode in between it makes it around 21v.

Just to clarify something, there is only one output from those PSU's. They have 3 terminals each for + and - but it's all just one output. I don't know what amount of current each screw terminal is rated for, but if you can, I would suggest using more than one for powering the motor drivers.

@Gefahren I have 2x of the LRS 350s from Stepper Online, they delivered really quick after your find so thank you!

I was looking at 1 motor per supply and 1x fan per supply to cool motor drivers if thats possible using 2 of the 3 terminals. Sorry, probably didnt explain that very well by saying 3 outputs.

What your explaining is completely workable, but what I was saying is to use two of the terminals to power the motor drivers. So, two wires for + and two for - going to the motor driver. Anything to help with power delivery.
Those screw terminals on the IBT's only can fit so much wire in them. I had used 14awg crimp on ferrules on driver end coming out to two 16awg wires going to the PSU. The two wires just fit in the ferrule and the ferrule just fit in the terminal on the IBT.
Maybe not necessary, but for power delivery I prefer the biggest total wire size I can get away with.