Odd behavior in "MX-210V" forward/reverse/power switches

Tomzo

Tomzo

H-M Supporter - Silver Member
H-M Supporter - Silver Member
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Jul 27, 2021
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221
I know, I know - I bought a cheap Chinese lathe, but I am not dissatisfied with the machine overall. I am still tuning things up (when I get time) and I expect to have it performing as well as it can pretty soon. This model has a 1100W brushless DC motor and controller on it.

One thing that is odd is related to the power switch and the forward reverse switch. When I power the unit up it comes on and the RPM display and speed pot work fine. If I hit the red button, the display stays on for about 5 or 6 seconds, then flickers with a "tick, tick, tick" sound coming from the controller board. It then shuts off, but the fact that it does this kind of bothers me.

If I have the late on and in the forward position, if I turn the speed down to zero and then switch into reverse it does the same thing as if I had turned if off with the on/off switch. This is annoying as I am fitting an electronic leadscrew to the machine and it has no thread dial (metric leadscrew) and I will be running the leadscrew backwards to move the carriage back without disengaging the half nut.

The direction switch is one of these: https://www.aliexpress.com/item/33006912928.html

The power switch is one of these: https://www.ebay.com/itm/3332428042...z%2BbRFYoKNdGbsICbnc|ampid:PL_CLK|clp:2047675

Assuming the color conventions from the main power inlet to the lathe are correct, the common goes to the rotary switch as well as to the main power switch. Three leads from the direction switch go to the motor controller board and are plugged in there. On the power switch, two of the pins are jumpered together.

I have a couple of questions:

- Is the whole lathe supposed to lose power when in the "0" position in the forward reverse switch? I thought that would just kill power to the motor but leave the rest of the system functioning. I suppose if it just turned off instantly without the delay, ticking sound, and flashing display it might not be an issue, but I would rather not have to open up the little cover and hit the green button every time.
- It seems to me that there is some power discharging somewhere that keeps the display alive for a while - I presume one of the capacitors on the main board. There are two large and a number of smaller ones on there. I noticed that there is a ground wire from the main power that gets sandwiched between the back cover and the main body from one of the panel screws. Both surfaces were painted so I scraped off all the paint thinking that there was no ground to dissipate the cap - no change. My electronics experience is pretty weak so this was just an idea I had for something to try.
- There are no identification markings on this controller board and it has a number of unused connections on it so I am pretty sure this was some excess controller they had laying around so they plopped it into this frankenlathe - the paint color varies in some of the components so I know it was cobbled together from the parts bin. I have half a mind to find a BLDC motor controller and just replace all of this stuff, but would like to see if there is some reasonable fix first.

Anyway, thanks in advance for any information any of you might be willing to share with a newbie machinist.

Tom
 
After reading my post I figured more information is needed. The jumpered connections on the on/off/estop switch are the A1-14 terminals which, if my understanding is correct, is used to hold the contactor in when the green button is depressed - otherwise it is a momentary switch.

I looked a bit more closely at the board with the back panel off and found that it is (unsurprisingly) a relay that is clicking. There is an LED on the board that after power is cut stays full brightness and then flickers and dims with the relay. There is another LED on the board that stays lit for a long time (I waited about 5 minutes) - even with the entire lathe unplugged.

I think this tells me that the power is coming from the capacitors. My understanding is that most circuits have some sort of bleeder resistor to drain down the caps. If only this no-name board had some identifying information on it so I could get a circuit diagram....
 
I suspect that rather than a malfunction, the controller board may be mis-adjusted. What I would try is first putting a mark on each trimpot on the board then one at a time readjusting the pots and watching the effect of each. You can always return to the original settings
It sounds like the behavior you are seeing is some sort of safety feature, either for you, the motor, or the electronics but perhaps working too well?
Does the spindle stop instantly when you hit the red stop button or is there a delay and relay ticking? I would put more importance on how the spindle motor behaves rather than the rpm display
-Mark
It would be a simple affair to add a bleeder resistor across the main supply cap(s)- post some closeups of the board
 
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Tomzo said:
I know, I know - I bought a cheap Chinese lathe, but I am not dissatisfied with the machine overall. I am still tuning things up (when I get time) and I expect to have it performing as well as it can pretty soon. This model has a 1100W brushless DC motor and controller on it.

One thing that is odd is related to the power switch and the forward reverse switch. When I power the unit up it comes on and the RPM display and speed pot work fine. If I hit the red button, the display stays on for about 5 or 6 seconds, then flickers with a "tick, tick, tick" sound coming from the controller board. It then shuts off, but the fact that it does this kind of bothers me.

If I have the late on and in the forward position, if I turn the speed down to zero and then switch into reverse it does the same thing as if I had turned if off with the on/off switch. This is annoying as I am fitting an electronic leadscrew to the machine and it has no thread dial (metric leadscrew) and I will be running the leadscrew backwards to move the carriage back without disengaging the half nut.

The direction switch is one of these: https://www.aliexpress.com/item/33006912928.html

The power switch is one of these: https://www.ebay.com/itm/333242804243?_trkparms=amclksrc=ITM&aid=1110006&algo=HOMESPLICE.SIM&ao=1&asc=234710&meid=d5586addeada4affaa732f61a2c3945a&pid=101195&rk=4&rkt=12&sd=333245525815&itm=333242804243&pmt=1&noa=0&pg=2047675&algv=SimplAMLv9PairwiseUnbiasedWeb&_trksid=p2047675.c101195.m1851&amdata=cksum:333242804243d5586addeada4affaa732f61a2c3945a|enc:AQAGAAACAJ4RPt93TDkhPrTGRGKPM5E6oQosJO%2BZfk9HzQ%2FCoO4yLhzAdwtiJ7uXAQEG1o%2BOR7UJ06ccjwRKJo0m0Dn2X74lZGLnOhdv0%2BZ80eIbM1huik3qSibdqYuK898QamC1QGPmZ0GD5fWgNHSyqaGvo2hj2S15RDDEYqJ0ZEs8IqQgls7vWj9S%2FjCKojBbjKuv%2FR79zqspxVwL4zCx7szaRqVTuurzE%2BJwHULhs2fGXCqZcLGE0IloDRbufOIYRCA9%2FAx%2BKv2Ox7A9jRwk1s9LS9syHvc0sSekNQyfJlKHd05SvM5uUzXK8aIIKetQG4U%2Fbq7S0voT3H%2BLqdimAGkVt5pXbx4%2BC7Fz6wmRJ%2BQhmBTO9e%2FDqXTUE2Ci1mGIuvzB0nZaebMEJVJHXnI8Wmtjw8n6FBsMjgi1ytef7b8%2FjDbiRX1YG%2FdiinuarbuHAX61mhKg6tNxVj4TYIaT0CXpzM6RU0if5FwQ9BRS1Pu%2B2Wr17kA%2FMfpQF22WBFcIeQI%2FCcBel%2FHNTkMscmxEhlEr23XPjK8zZaSYf91RomfEq2QBHOBLSQMgqpD%2BkDcik3k6pDFbdUXwHu3fUPI8CiecphrX3AIhZWJLCy3W2bJkVp9a1v1BrIniHEchMPtdTR8EoAGo4I7RuuKjf2fhaXicDAwq6zz%2BbRFYoKNdGbsICbnc|ampid:pL_CLK|clp:2047675

Assuming the color conventions from the main power inlet to the lathe are correct, the common goes to the rotary switch as well as to the main power switch. Three leads from the direction switch go to the motor controller board and are plugged in there. On the power switch, two of the pins are jumpered together.

I have a couple of questions:

- Is the whole lathe supposed to lose power when in the "0" position in the forward reverse switch? I thought that would just kill power to the motor but leave the rest of the system functioning. I suppose if it just turned off instantly without the delay, ticking sound, and flashing display it might not be an issue, but I would rather not have to open up the little cover and hit the green button every time.
- It seems to me that there is some power discharging somewhere that keeps the display alive for a while - I presume one of the capacitors on the main board. There are two large and a number of smaller ones on there. I noticed that there is a ground wire from the main power that gets sandwiched between the back cover and the main body from one of the panel screws. Both surfaces were painted so I scraped off all the paint thinking that there was no ground to dissipate the cap - no change. My electronics experience is pretty weak so this was just an idea I had for something to try.
- There are no identification markings on this controller board and it has a number of unused connections on it so I am pretty sure this was some excess controller they had laying around so they plopped it into this frankenlathe - the paint color varies in some of the components so I know it was cobbled together from the parts bin. I have half a mind to find a BLDC motor controller and just replace all of this stuff, but would like to see if there is some reasonable fix first.

Anyway, thanks in advance for any information any of you might be willing to share with a newbie machinist.

Tom
Click to expand...
My lathe looks similar to yours. When I received my PM1022 I thought that certainly it was not working correctly. Stopping the machine would completely shut it down. When turning on the machine it would not start until moving the speed dial to minimum. That is a pain due to having to reset the speed at every start. Shutting off the power switch would stop the lathe but if the speed was set to minimum it would still be powered for about 8 rotations before shutting down completely (I believe that the capacitors are responsible for this). Not exactly ideal when threading to a shoulder. Moving the F-O-R switch to O would stop the lathe quickly and turn the machine completely off. I called PM and they said that it was normal. I have gotten used to the unusual setup but may someday dig in and see if I can make it behave as I want. I hope you find a solution. It really sucks for CNC.
 
Mark - I searched the board and there are no trim pots on there - likely due to the BLDC design. I did take it out completely and found what appeared to be a part number (EP-SM9088-C) but this returns no hits on Google. I have not powered it down while turning to see if it stops immediately but will try that - once I get it put back together.

Kevin - at least that is one bit of information that says this is "normal" for this class lathe - SMH.

The lathe works and all, but these little glitchy things bug me quite a bit. It really makes me want to build or buy a new controller setup if nothing else so I will know what I have. I have seen BLDC controllers for e-bikes and the like that look interesting to me but I am not sure if something like that would adapt to this application. I have a buddy who is an EE and will be pinging him shortly.

Thanks

Tom
 
I'm sure you could sub a different controller- BLDC motors are really just 3 phase ac motors with a permanent magnet rotor, but your system may use a speed encoder on the motor shaft which talks to the controller
If you think bleeding down the power supply would help I could give you a hand there- need to identify the main storage caps, and read the capacitance value in microfarads (uF) to select a suitable bleed resistor
Use care
 
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Thanks Kevin - much appreciated. The lag time in the control system turning off is annoying but I can probably live with it. I do want to figure out how I can get the direction switch not to kill all power when it gets to the 0 setting. It may cost me a round of golf but I think I will have my EE friend take a peek before I start really digging in to the controller. Also, if I do start soldering stuff on there I want to identify a source for a BLDC controller so I know I have a fallback before I turn this lathe into a very heavy brick....
 
 
Is your lathe still configured as the OEM lathe or has there been some modifications. The type of switch illustrated in your first link comes in many different configurations.

I used one with my sdc brush motor but I have mine wired between the controller output and the motor so that I reverse the leads going to the motor or break the circuit for FWD/REV and OFF. I use the red eStop button for the main power switch. I only shut it off when I am done machining as it kills the power to the controller. I have the Clough42 ELS but it is on a separate power supply and I generally don't shut it down.
 
Well if by OEM you mean it is wired the way it came from the manufacturer then yes it is. I am thinking that since the neutral basically gets cut off when the direction switch is on 0, I am thinking that the "latch" on the main power switch releases and kills all power. Since the off switch and estop should cut the hot wire I wonder if I wire the neutral to the main switch directly from the power source in addition to the selector switch. If my theory is correct this would keep the controller "live" without affecting the circuit that tells the motor which way to turn.

Sound plausible?


Sent from my iPhone using Tapatalk
 
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