Swapping out Hall Effect Lever for Potentiometer on Sewing Machine Servo Motor? - Page 1
Forum section: electronics / beginners

author: oceanslider
author_rank: Contributor
timestamp: December 28, 2022, 09:21:57 pm
content: Hello Group,First off, I am new here. Also, I am far from being an electronics expert. But over the years I have loved watching EEVblog YouTube videos on electronics.But now I find myself wanting to do an electronics modification on a sewing machine motor controller. And that is swapping out the Hall Effect Sensor lever for a Potentiometer control knob for speed control of the DC Servo motor.These motors are popular with the Mini Lathe guys. In fact there is even a guy that is has started up a business providing modified controllers and motors. Here is his websitehttps://www.servomotorkit.com/On the Facebook Mini Lathe groups guys are all over the place in what they come up with (differing valued potentiometers with differing resistor values inline) to swap out the Hall Effect Sensor (speed control lever) for a Potentiometer (control knob).It is hard to tell if some of these mods are guys that know just enough to get themselves in trouble.I do know that the capcitors on the control board have enough juice to zap you and that the Hall Effect Sensor has a Floating Ground.I'd love to hear some expert thoughts on this type of modification.Here is a sight I found that shows a Consew CSM1000 schematic (it should be noted that this drawing is from 2015 and they could have changed by now)http://www.vinland.com/Images/Consew-Schematic.pdfFavored brands of these motor are Consew, Velvor, and Mophorn. They are great little motors. Guys are using them for Mini Lathes, Belt Sanders, Band Saws, and many other applications.The ones I am interested in doing this mod to are the Mophorn CS1000 which is a 3/4hp version and a Consew CSM3000 which is a 1hp version.

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 30, 2022, 09:56:23 pm
content: Do you have the unit or only the picture? I guess the hall effect sensor is in the device on the left. I have never seen a hall effect sensor used that way so I think I would have to have a unit to play with to figure out.

author: oceanslider
author_rank: Contributor
timestamp: December 31, 2022, 05:36:56 am
content: Quote from: BeBuLamar on December 30, 2022, 09:56:23 pmThe schematic I attached is for the 3/4hp Consew CSM1000, I have the 1hp Consew CSM3000. But I think the Hall Effect lever they use are the same.A guy on one of the Facebook Mini Lathe groups posted this drawing attached

author: EPAIII
author_rank: Super Contributor
timestamp: December 31, 2022, 06:11:21 am
content: I have no experience with those motors or controllers.But I am curious as to why you or anyone would want to use a potentiometer, which will eventually wear out and become unreliable, in place of a Hall effect control which will probably outlast the machine. What advantage does the potentiometer offer that the Hall effect control does not?

author: Ian.M
author_rank: Super Contributor
timestamp: December 31, 2022, 09:40:19 am
content: * Panel mounting?* Reusing existing control?(Which in the case of mini-lathes and mini-mills is almost invariably a linear taper 4K7 potentiometer with an internal switch, closed in the Off/Zero speed, fully anticlockwise position, used for an interlock circuit that requires the speed control to be reduced to zero before starting the motor, preventing the motor starting at full power when the guard is closed and the zero volt release switch turned on. You cant substitute an ordinary switched pot as those have the switch off at zero, and usually a log law taper)

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 31, 2022, 11:34:29 am
content: I still don't know what the hall effect sensor does in the sewing machine. I think it's not for speed control but rather to detect the needle position and thus why it needs a servo motor for that. I see drawings but I do not see how the modification is made. The drawing with the hall effect sensor and the drawing with the potentiometer don't show the same connector.

author: Ian.M
author_rank: Super Contributor
timestamp: December 31, 2022, 12:25:11 pm
content: Sewing machines almost invariably use cams, gears and mechanical linkages to coordinate needle, shuttle hook, feed dog and foot movement. The stitch forming mechanism is typically an interference mechanism - if the needle is down at the wrong part of the cycle, stuff will jam or break. As such, unless the machine has programmable embroidery stitch patterns, with actuators for stitch length and width, there is typically no need for sensors to detect handwheel position i.e. where it is in the stitch cycle.The foot pedal, used to start/stop the machine and control the speed, would typically be connected by a simple rod linkage under tension to the lever arm of the hall sensor assembly.

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 31, 2022, 12:56:29 pm
content: You're talking about ordinary sewing machine which doesn't have servo motor either. The Consew sewing machines are not the regular sewing machines.

author: Ian.M
author_rank: Super Contributor
timestamp: December 31, 2022, 01:07:56 pm
content: Certainly, but Comsew also do servo motors to drive 'dumb' third party machines:https://www.consew.com/list/machine-stands/servo-motorsSome *DO* have external position sensors, to be mounted on the machine, apparently to facilitate stopping with the needle up.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 01:15:35 am
content: Quote from: BeBuLamar on December 31, 2022, 12:56:29 pmThese motors have been very popular with the Mini Lathe guys. They are a major improvement. They have high torque at lower speeds. They are even popular to power other power tools. They have become popular to power the Harbor Freight 1" x 30" belt sander.There are other brand names for these also, Mophorn, Vevor, and many others.As I posted in my first post there is even a guy with a website doing modifications of these motor/controllers

author: jpanhalt
author_rank: Super Contributor
timestamp: January 01, 2023, 01:41:20 am
content: Have you considered that a linear (e.g., lever) controller might be useful for adjusting spindle speed to diameter? That is, save it and couple it to the crossfeed.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 01, 2023, 02:13:45 am
content: The schematic is not complete. There is a reference to a sheet marked "STM8S005k6", which I assume has a microcontroller and some supporting circuitry ( Probably including the HALL sensor) but the sheet itself is missing.I know there are HALL sensors that can be programmed to deliver a 0 to 5V output signal just as a potentiometer, but I do not know if such a HALL sensor is used.Two 1500uF capacitors in series, and then directly on mains has plenty of potential for a serious zap!Also, with 4 100k discharge resistors you've got an RC time of 4e5*750e-6 = 300.0 = 5 minutes. It would need 4 RC times to get to 50V (from a start of 300V), so that's 20 minutes, and even then it's still got some juice left. That sure is a quick way for beginners to learn real fast.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 04:33:20 am
content: Quote from: Doctorandus_P on January 01, 2023, 02:13:45 amRegretfully I'm not a electronics wizard :-( I know just enough to get me in trouble. In fact, I opened up the hall sensor while plugged in not even knowing what it was LOL. There has been no one showing that they have put a scope to the circuitry.And I'm thinking more and more some of the mods guys are doing are just guessing. Yeah a potentiometer might work to control the speed of the motor, but it seems for these controllers you got to have a better understanding of electronics.These are coming from China. No UL Listing on these babies.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 01, 2023, 10:40:35 am
content: Quote from: oceanslider on January 01, 2023, 04:33:20 amThat was also clear from the schematic.There is no common mode filter on the primary side, which would make it highly unlikely that these things would conform to EMC regulations.I've looked at some pictures of controllers for these things, and the mains capacitors tend to be a lot smaller such as 680uf, Combined with that there probably is some other leakage and wishful thinking, then theymaybe discharged by the time you have managed to open the box. But if you open any device that has big high voltage capacitors then the first thing you should always do before any other tinkering is to measure the voltage on them, and wait or discharge until they reach a safe voltage level.But it's quite common for the ignorant to ignore such things.

author: Ian.M
author_rank: Super Contributor
timestamp: January 01, 2023, 11:34:26 am
content: Quote from: jpanhalt on January 01, 2023, 01:41:20 amNot really. To maintain the same surface speed. one needs to make RPM proportional to 1/r, not to r. Also the tool adds a significant offset between the crossfeed position and the actual cutting radius.@oceanslider,It would be fairly simple to disconnect the whole hall effect lever assembly, and feed it safe isolated 5V e.g. from a USB charger, so you could safely measure and (manually) plot the relationship between lever position and output voltage. That would answer a *LOT* of questions about the circuit you need to build to replace it. Also, it may be possible to identify the hall sensor, and a datasheet for it would help answer any remaining questions.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 05:30:48 pm
content: Quote from: Ian.M on January 01, 2023, 11:34:26 amAttached are pictures of the Consew Hall Effect Lever. Just curious what would happen if the magnet on the lever touched that PCB?

author: Ian.M
author_rank: Super Contributor
timestamp: January 01, 2023, 05:33:47 pm
content: So what's the Hall IC (black three leg component in photo #3) marked as? If you can read a part number off it, we can probably find a datasheet . . .What happens if the magnet touches the PCB depends on where it touches the PCB. Anywhere away from tracks and pads, no problem. If it touches the pads, and the magnet has a conductive surface, bad things will happen.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 05:36:28 pm
content: Quote from: Ian.M on January 01, 2023, 11:34:26 amWell they are good motor for a few reasons. They have high torque at lower speeds and they use minimal watts compared to traditional AC motors of comparable HP using a VFD to adjust speeds.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 05:41:16 pm
content: Quote from: Ian.M on January 01, 2023, 05:33:47 pmSo there should be a marking on that little black block on the pcb where all three wires attach?

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 05:47:44 pm
content: Here is a video of a guy using this type of motor to modify a bandsaw. This is actually the guy who modifies these and has a website selling the modified units that I shared in my original post. And from this unit you can see he has added a Potentiometer right on the control unit. (I time stamped this YouTube video, as most of it is bandsaw related) thecustomcrafter.comhttps://youtu.be/6HhShd1n62k?t=952And attached is a picture I just took of the Hall on the lever that came with the Consew CSM3000

author: Ian.M
author_rank: Super Contributor
timestamp: January 01, 2023, 06:47:46 pm
content: https://www.diodes.com/assets/Datasheets/AH49E.pdfSeveral manufacturers make equivalent sensors under similar part numbers.Key things to note: Unlike a potentiometer, the sensor output is *NOT* rail to rail. Typically its output swing is going to stop 0.8V short of the rails and at worst 1V giving a swing of only 1V to 4V with a 5V supply. Its output is an emitter follower that can source an abs. max. of 10mA, but can only sink typ. 65uA.Next you need to determine the minimum voltage from the sensor to start the motor, and see if it will run down to a lower voltage, or whether it stops at pretty much the same voltage it starts at, and also what the full speed sensor voltage is. Also check if the speed control is reasonably linear with respect to lever position - there may be an adjustment for that on the control board.Also tell us what speed control characteristics you need once a pot is fitted.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 06:54:44 pm
content: Here are pictures of the MopHorn CS1000 Hall. So appears they use the same Hall Sensor regardless of the motor horsepower. Or controller PCB configuration.

author: Ian.M
author_rank: Super Contributor
timestamp: January 01, 2023, 06:59:13 pm
content: Yep, that's the same '49E' Hall IC, so if the magnet strength and movement range relative to the IC are similar, they'd be interchangeable. Its only a control input, so there's no reason whatsoever to use a different sensor.What would be different would be power semiconductors on the control board, which would need a higher current rating for a higher power motor, and any current sense resistor, which would need to be lower resistance and probably higher power. Otherwise the same basic controller design could well be used for a 10:1 range of motor powers.

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 01, 2023, 07:05:35 pm
content: Now that I saw the sensor and have the datasheet. It would be relativeley easy if you have the unit with you.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 07:14:04 pm
content: I do have the unit. I have both a Consew CSM3000 (1hp) and a MopHorn CS1000 (3/4hp). Here is the manual and pictures of the MopHorn CS1000 (labeled on the front as Vevor). None of us are using the synchronizer, that is a option for people that use this motor for sewing machines and need it.https://www.amazon.com/dp/B07HFTMR8Z

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 08:57:34 pm
content: My wire coloring for the MopHorn CS1000 as was indicated by this Amazon review is different, my wires are colored Red, Yellow, and Black. As I have mentioned previously guys are all over the place on Potentiometer and Resistor values. Some are also using multi rotation Potentiometers.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 09:28:04 pm
content: If any of you real electronics experts who have scopes and all the good testing equipment wanted to check this motor out for those of us who don't have the equipment or skillset, maybe do a YouTube video on what you find out. You could buy a Harbor Freight 1x30 belt sander to install it on. Guys are using these for sharpening with that sander from Harbor Freight.https://www.harborfreight.com/1-in-x-30-in-belt-sander-61728.htmlswapping out the motor for the Mophorn CS1000 For around $150 you'd have a better sharpener than the Work Sharp Ken Onion Edition sharpener. I posted a picture of that setup earlier.

author: mikerj
author_rank: Super Contributor
timestamp: January 01, 2023, 09:35:23 pm
content: I see no sign of an isolated DC-DC converter on the control board, so it's probably safe to assume everything is at line voltage including the hall effect wiring. With that in mind ensure any potentiometer is rated for full mains voltage (I'd suggest a known quality item such as Bourns, sourced from a proper distributor rather than fake eBay junk), and either use a plastic knob and shield any metal parts from the user or ideally ground the body of the potentiometer.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 10:13:13 pm
content: Quote from: mikerj on January 01, 2023, 09:35:23 pmThere you go speaking that electronics mumbo jumbo LOL, thanks for educating the non-educated. I am to assume as was previously pointed out by Ian that the "full mains" is very substantial.

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 01, 2023, 10:25:43 pm
content: I would measure from the 3 connections of the pedal to ground and see what kind of voltage is there. If it's high then you have to be careful. But any way connect a 5000 ohms or 10000 ohms potentiometer between 5V and 0 V. The wiper goes to the pedal. The adjustment will be below 0 speed and above max speed. You would need to measure the voltage between 0 and the wiper (pedal) to see at which voltage the motor start to run and at which it reaches max speed. The you can calculater the resistors for min and max limit.

author: Ian.M
author_rank: Super Contributor
timestamp: January 01, 2023, 10:34:31 pm
content: Odds are the control circuit is connected to the negative side of the DC bus which will effectively be half-wave rectified mains, so will peak at about -170V with respect to earth ground. You should assume its mains live, so choose components with appropriately rated insulation, secure and insulate wiring as-if its mains and make sure the pot has either a plastic mounting bush and shaft or if metal, is mounted to a properly grounded metal panel and fitted with an insulating knob.

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 10:41:34 pm
content: Quote from: Ian.M on January 01, 2023, 10:34:31 pmThank you Ian, glad I choose to seek out a group of guys that know this stuff. For instance, this is one of the Potentiometers that have been recommendedhttps://www.amazon.com/gp/product/B071X4DKV7And just from the looks and price I would have to assume it is cheap and not of the quality you recommend.Also as mentioned shouldn't the hall effect lever also be grounded on its own

author: oceanslider
author_rank: Contributor
timestamp: January 01, 2023, 10:45:16 pm
content: Quote from: BeBuLamar on January 01, 2023, 10:25:43 pmAssuming it is high would there be any hesitation measuring this voltage with an inexpensive multimeter? Also, I would assume this voltage to be DC. So, the previously stated 300 and 170 volts are DC?

author: Ian.M
author_rank: Super Contributor
timestamp: January 01, 2023, 10:56:25 pm
content: Actually, its *probably* good enough. If there is 2mm creepage distance and clearance from any terminal, the track, and metal wiper contacts to the metal body and shaft, its OK for the application provided the panel is properly grounded, though I would advise adding sheet insulation between those terminal rivets and the panel! The problem with off-brand parts from Amazon etc. is you don't know if they are safe to use unless you buy two and tear one apart to check!For comparison, this is the pot typically fitted to mini-lathes (which also use a mains live control circuit) sold in the USA:https://littlemachineshop.com/products/product_view.php?ProductID=1282As you can see, its very similar, except it has a closed at Zero switch on the back to inhibit starting except from zero speed.*DON'T* attempt to measure the voltage with respect to ground with a cheap multimeter. The multimeter needs to be high input impedance (typically 10 Meg) and both it and its test leads need to be rated for Cat II or higher use. A low impedance meter could damage the controller and an lower category or unrated meter and /or leads (or ones with a fake rating) may fail dangerously while measuring mains, putting the user at risk of electrocution and/or severe burns.If you are tempted to use an cheap or unrated meter, switch off the mains supply, put it on the bench with the leads away from anything else, set the range, clip or otherwise fasten its leads to the points you are testing between, and only then switch on the mains supply. Take the measurement *WITHOUT* touching the meter or leads, and switch off the supply before disconnecting the leads.The voltage with respect to ground is pulsing at 60Hz. Expect to see a lot less on the meter than the -170V peak I previously mentioned - depending on the meter somewhere around -55V DC could well be 'in the ballpark'

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 01, 2023, 11:02:03 pm
content: Quote from: oceanslider on January 01, 2023, 10:45:16 pmI have used the $5 Habor Freight DMM to measure 120VAC voltage but I probably shouldn't do that. All my others meters are safe to do so as I often work with 480VAC. Yes the voltage should be DC. But to be sure I would measure both DC and AC.

author: oceanslider
author_rank: Contributor
timestamp: January 02, 2023, 01:43:22 am
content: Quote from: BeBuLamar on January 01, 2023, 10:25:43 pmOn the controller you can also set the max RPM limit. That is, if you want to limit max RPM for the footpedal depressed all the way.But assume you would want to first know the actual max of the setup. I did find this graph for the Consew CSM1000 which is a 3/4hp motor

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 03, 2023, 05:26:56 pm
content: If you use the resistor values like the drawings on your second post. The one right after mine 3.3K, 10K, 6.8K then the potentiometer would vary the voltage from 1.69V to 4.17V which is close to what you have on your chart. You can just use those values and just be careful if you have high voltage. It's kind of a cheap system I think as all the drives I ever worked with the control system would have voltage of 24VDC max.

author: oceanslider
author_rank: Contributor
timestamp: November 18, 2023, 12:32:43 am
content: Just a follow up on these motors. I found one of the main manufacturers on Alibaba and bought a few units from them. So, during that transaction I asked for the 750 Watt version of their motor, what DC voltage is supplied to the motor from that little controller, and the rep said 0 to 300 volts. Could that little controller really send 300 volts DC?The 750-watt motor they rate as 3/4 HP, but they also make 1500-watt motors.https://szdianji.en.alibaba.com/They are great motors for tools because they have great torque and variable speed at a very low price compared to a traditional AC induction motor controlled by a VFD.Grizzly Tool Company just released a belt grinder using this type of DC servo motor.https://www.grizzly.com/products/grizzly-2-x-42-knife-making-belt-sander-grinder/t32459And the wiring diagram for the motor and controller is found here:https://cdn0.grizzly.com/manuals/t32459_m.pdf

author: Ian.M
author_rank: Super Contributor
timestamp: November 18, 2023, 06:58:40 am
content: Quote from: oceanslider on November 18, 2023, 12:32:43 amOf course it couldn't. We've already found the hall sensor IC's datasheet and seen its a 3V - 6.5V part, and its abs. max supply voltage is only 8V. 300V across it would blow it to bits faster than you could blink. Its not even correct to say its 300V with respect to ground as the control voltage is riding on top of a common that's got half wave rectified mains on it, so about 170V peak in North America and 310V - 340V peak in the rest of the world.However 310V is near enough 300V to a salesdroid picked for their English, not their technical knowledge!

author: Nitrous
author_rank: Newbie
timestamp: October 02, 2024, 01:57:11 am
content: Are the speed controllers regulating the Chinese servos all as simple as a linear Hall effect sensor and a moving magnet or are there some with more complicated circuitry?ThanksDoug

author: perieanuo
author_rank: Frequent Contributor
timestamp: October 02, 2024, 08:30:04 am
content: Quote from: Nitrous on October 02, 2024, 01:57:11 ami worked in the industry and repaired sewing machines, for example Brother has the same hall linear sensor approach and optical barrier for back-pedal stop and trimming.so the speed is imposed by the hall approached by a moving magnet. they had this on regulated DC motors on older series and they switched to AC regulated motors before 2007 if i remember right, pedal control was almost the same, at least for general sewing machines.imho, i see no reason somebody replace a hall sensor (tolerant to all kind of dirt, best approach for this job) with optical or mechanical potentiometer unless he want to have future issues with the clientfor example, for speed and position detection of the sewing shaft we had thousands of sewing machines with optical sensors (brother mainly) and hall ones. which type was a pain in the ass, you guessed already.br, ovidiu

author: Ian.M
author_rank: Super Contributor
timestamp: October 02, 2024, 11:30:30 am
content: The only reason to use a pot is to satisfy the requirement for a panel mount 1/4" shaft speed control without having to find space for the hall sensor + moving magnet assembly + design mountings for it + a mechanism to operate it with a through-panel shaft. Everyone knows a pot is much less reliable even if you pay the premium for a wirewound or cermet element pot. OTOH unless you specify something crazy like the Chinese mini-mills and mini-lathes with a NC inhibit switch integrated with the pot (as opposed to the usual integrated power switch NO in the fully anticlockwise position), they are cheap and reasonably easy to replace when they fail.

author: Nitrous
author_rank: Newbie
timestamp: October 02, 2024, 02:26:37 pm
content: The other reason to switch is if you don’t have the speed regulator lever assembly. In that case there will be a controller error and no way to control the speed of the motor. That is the actual reason I’m inquiring.So, simply buying a linear Hall Sensor won’t help, because I don’t have the original controller. I’m just trying to get a functioning motor and controller.Thanks for your comment, though.

author: Bystander
author_rank: Newbie
timestamp: March 02, 2025, 12:38:01 pm
content: Just wondering if this issue was ever sorted by the OP as i have the same question. Operating a lever is not great where as a speed potentiometer would be great. Also the same type of controller box is now available with a potentiometer .

author: Bystander
author_rank: Newbie
timestamp: March 02, 2025, 03:19:58 pm
content: This was info given on a group for these mini lathes

author: Ian.M
author_rank: Super Contributor
timestamp: March 02, 2025, 04:17:11 pm
content: Try a circuit like Oceanslider posted *way* back in reply#2.As I noted back in reply#20, theAH49E Hall sensordatasheet tells us the speed control sensor output *cannot* be rail to rail, and I noted that it could typically swing from 0.8V to 4.2V assuming a 5.0V supply. However the actual sensor + magnet assembly is likely to have a lesser range - the magnet may not be strong or close enough to reach max. output, and with no magnet present the output should actually be midrange, i.e. 2.5V so anything below this is due to the far field of the magnet curving back to its other pole. Hence the 'endstop' resistors R2 and R3 in series with the ends of the potentiometer track in this circuit.A possibly easier approach to determining a good value for them would be to hook up a 10K pot without them, with a DMM on DC volts safely connected*between Vin and 'boosted GND', and measure the min. voltage when the motor just cuts out and the voltage at which the motor reaches max. speed (past which turning the pot further does not make any difference to the speed), then doing the math to calculate them and choosing the next lower preferred value.Note that there may be an internal 10K input resistor between Vin and 'boosted GND' inside the motor controller, which affects the calculation - you can confirm if that's the case by disconnecting the mains supply, and measuring resistance between those terminals with nothing connected to them. If there is one, a lower value pot may be desirable for better linearity, but not less than 1K, (which with endstop resistors, shouldn't pull more current than a AH49E).If math and basic circuit analysis aren't your strong points, post your measured voltages, total potentiometer track resistance, and measured input resistance of the controller here and I'll quite happily 'crunch the numbers' and suggest resistor values.* The whole control circuit is 'mains' LIVE and a serious electrical shock hazard, so use clip on probes and make sure they are securely connected *before* connecting the mains supply. If using a cheap DMM with a suspect or no CAT rating, don't touch it or its leads while mains is connected. Also, mount the pot to something or clamp it in a rubber jawed vice so you don't have to hold it, and put a plastic knob on it, don't try to turn its shaft directly with your fingers!