Hey guys, just looking for advice on what electronics to run for my welding turntable project.
I’m running a 60w brushed DC motor with a twin mechanical reduction. For this application my rpm range needs to be between 0.2rpm - 2rpm. Ideally I would like a digital display with good/accurate resolution and a Bluetooth on/off foot pedal.
I’m not very good with electronics so my question is what esc would you recommend for low rpm and also how would I go about getting a Bluetooth foot pedal and digital display tied in?
I’ll attach some pictures for reference, let me know if you need any more info.
Interesting project, just curious, how “Ready-To-Fly” of a solution are you after?
I could definitely see a potential solution using some ESP32s or similar microcontrollers set up with Bluetooth modules (one in the footpedal and another between a PSU and a motor driver with an OLED or similar acting as your display) with a fairly beefy Sabertooth motor driver or similar capable of driving that motor up towards its limits at stall.
Although that’s a pretty significant amount of work to design, test, and assemble given that there are likely some systems out there that already exist for this exact application that would be quite close to plug-and-play (although I’ve personally never looked into this exact use-case myself, although someone else in the community may have some suggestions if that’s what you’re after).
That looks like a heft motor, what is controlling it currently? Is it speed controller or just directly hooked up to power with an on/off switch?
We’ll need to know the motors operating voltage and stall current to be able to size up a motor driver/controller that could run it.
As for the Bluetooth control most microcontrollers with built-in Bluetooth should be able to handle that and Bryce’s suggestion of an ESP32 variant is probably going to be the most cost effective.
Hey guys thanks for the response. I have not currently used it as it’s still In the design phase. It did come with a controller but seems a bit cheap although I’m happy to use it if you guys think it’s good, I’ll attach some photos and a motor spec sheet.
As for plug-and -play I’m happy to do leg work myself, I’m not very good with electronics but If you point me in the right direction I can do some research. On the other hand I’m also happy to pay design fees depending on cost if it means getting a better results.
Anyways let me know what you think, thanks again for the response!
That looks like a pretty hefty controller as indicated by the Max 40A printed on the box.
I had dealings with an automatic TIG welding set up some 20 odd years ago and had one major problem. This set up was (is) for the welding of iron core laminations and bases on transformers, ballasts and other inductive components. This involved the precise and steady control of the welding torch traverse speeds (up to 6 welders simultaneously). This was somewhere between 1.5 and 5mm/Sec switch selectable with a variable option. But that is not where the problems arose.
The problem turned out to be the actual speed of the motor which was a pretty similar (in concept) to yours being a brushed electronically controlled unit. Due to several reasons the actual traverse speed was very hard to control with repeatability and reliability very poor and seemingly non linear. I think the main reasons were mechanical and motor response at very low speeds.
This was rectified by simply doubling the initial drive ratio to have the motor operating up into its linear region. This came at the expense of maximum traverse speed but as the traverse itself was non critical at full speed (welding speed was the critical criteria) we lived with this and all turned out OK.
The sensor reading, interlocking and function switching for the whole process (the smart work) is done with a PLC.
I post this in case you have any problems with operating this at very slow speeds. You may have to look at your gear ratios to get the motor spinning faster.
Hey Robert, thank you for the reply.
You are very correct. The issue I’m facing is very few small turntables on the market are made for what I’m doing (spinning large diameter thin stainless and aluminum tubes very slowly). Most are for mig and run very fast and if you try to run slower the results are unpredictable and almost imposable to get any kind of repeatability.
This is why I’m making my own the motor that Im using has a twin mechanical reduction, one orbital and another worm gear, giving me close to what I’m looking for which is ~0.2rpm to around 2rpm. The reduction sets are interchangable also so I can make mechanical adjustments if needed but would like to avoid
I did notice that the adjustment seems still a little touchy near stall and the digital display dosent work untill around 4 which I assume is volts as it only goes to 12. This is why Im thinking maybe a more precise controller is needed??
Thanks again Robert!
That is the sort of thing I was referring to. You may do better by increasing your gear ratio to increase the required motor speed. There are a lot of Mosfets etc on that board and even if the direction change is by reversing motor volts with the switch which it appears to be the case there could be a “H” bridge to do the PWM switching. If that is the case, depending on how the PWM is handled there could still be a problem creeping the motor from standstill. There is a reason and a bit long to go into here and would entail connecting an oscilloscope directly across the motor and observing the waveform as speed is slowly increased from standstill. A bit hard to do remotely I am afraid and you probably don’t have access to an oscilloscope.
I think you could be right and the display is powered by the voltage to be measured, 4V is probably minimum.
Thanks for posting some more images about the existing controller. That thing looks beefy indeed! Only the largest motor controllers we stock will get up to 40 Amps.
Do you know what voltage is being supplied to the existing motor controller? I can see it’s marked DC12-48V but it’s not super clear if that’s the supported input range, or if that’s what it is sending to the motor, I suspect the former.
Were you interested in trying to develop the Bluetooth trigger first and retrofitting it to your existing system, then tackling the new motor controller half of the project or were you looking to start fresh with a whole new rig and tackle both halves at once? Generally I prefer incremental upgrades and building things piece by piece so you have room to pivot as problems arise, but everyone has their own project flow.
Hey Trent, sorry for the late reply I’ve been flat out with work.
I’ll send through some photos of the power supply for the controller.
I think it’s a good idea to do incremental changes for sure. We can start with the Bluetooth foot switch and go from there
Thanks heaps for all the advice, it’s much appreciated!
The motor you pic’d would appear to be a 60W unit. Even if the motor is lightly loaded 12V @ 5A is 60W. you might not have enough headroom in that power supply for all you want to do.
As a point of interest why are you planning on a bluetooth foot switch. Surely a couple of wired from the switch to a controller would be simpler. I think Bluetooth is only adding a level of complexity which is not necessary.
If you need to or keen to go down this path I would suggest you leave this bit until last. Get the basic device working properly first and add the frills later. Believe me I have had many years of practice at this sort of thing. Not particularly Bluetooth foot switches but project (some very large) work in general. I think if you start with the Bluetooth bit you will finish up going in circles and we all know how that ends up.
Thanks for the photo, that confirms the 12-48V marking on your controller is definitely its input range and as Bob has said your motor power is currently matched to your power supplies maximum output.
Normally you’d want a bit of headroom in the power supply so if your motor is a bit inconsistent and jumpy at low speed it may be that the power supply is struggling to keep up with the start-up currents of the motor (peak current load is when the motor is first powered on).
It’s possible a bigger power supply might improve the performance of the existing setup but hard to know for sure without being able to measure what’s actually happening in the motor when it is acting jumpy.