I made a similar motor, but it has a physical driver built in. Speed is controlled by driver placement and direction by current polarity. Switching is accomplished by using a light source, a reflection device on the rotor, and a stationary light-recognition switch.
@AKIOTV9 ай бұрын
nice
@ws600211 күн бұрын
Some of the best videos on explanatory electrical engineering I have encountered here on KZbin.
@analoghardwaretops39769 ай бұрын
Switching the low side/s is like you are doing a "BOOST " MODE pwm whereby the DC link voltage can exceed the nominal rectified volts.. Whereas with pwm on the high side you have multiple benefits.. 1) now it's like a buck mode controller...just what we want when a lower speed than max.is required .. 2) it serves as an auto bootstrap for the upper gate drivers...even recharging the bt.strap caps during each pwm off time. 3) speed is directly prop.to ( d ) or (t-on). 4) B.E.M.F. can be sensed during the (off time) of the pwm.
@InfinionExperiments2 күн бұрын
4 is a misnomer. Pure iron SRM's do not have BEMF generated as a consequence of motion like typical BLDC generators. The EMF from the H-field collapse is what will be sensed, and is more akin to transformer action. This is why typical regen braking strategies aren't feasible with SRMs.
@AlejandroFernandezDaCosta7 ай бұрын
I am not a native english speaker but I know you are a excelent comunicator
@jonnafry10 күн бұрын
Delivery is perfectly fine .. keep up the great content.
@machineman89209 ай бұрын
It's better to do the pwm switching on the top transistor because it completely breaks the loop and it can't build up 'momentum' at low duty cycles, potentially damaging the bottom transistor with voltage spikes I think
@analoghardwaretops39769 ай бұрын
For Top side pwm ,most economical is the (1T & 3B) switch configuration...here you save two power switches & their related drive circuitry...
@AKIOTV9 ай бұрын
This is true, but the maximum output of such an n+1 circuit is lower, since current to all phases flows through that single mosfet.
@analoghardwaretops39769 ай бұрын
@@AKIOTV yes ..but one at (phase) at a time in sequence, & the top is like any continuous running pwm single switch..... there's no limitation on that single switch..if properly sized & controlled.
@Axman69 ай бұрын
So you’re saying you’ll have a SRM powered skateboard in two weeks? 😂 Another great vid, nice work.
@MyKharli9 ай бұрын
That was great ty . I am trying to imagine its ability as a diy ebike wheel hub motor .
@analoghardwaretops39769 ай бұрын
A bifilar wound flux switching motor is the simplest in this category..no complex electronics..& can be speciallywound to simulate a seriers dc motor with those benifits..
@ovidius200012 күн бұрын
whatDoYouMean?WhyBifilar?
@analoghardwaretops397611 күн бұрын
@@ovidius2000this is not exactly an SRM topology but a variant . Here there are only two coil windings , both are wound together but in anti- parallel (bi-filar)...and similar just like what's in a bi-filar push-pull switching transformer.... pls look up these terms on the web .if in doubt.
@MrTaddelie9 ай бұрын
Nicee, hoping for performance numbers at some point, but the build itself is already completly new to me
@keithminchin18179 ай бұрын
Once again - nice job 👍🏻 Switch the high side because you are boot strapping the high side MOSFET gates. The boot strap capacitors discharge quickly and require recharging. I’m guessing you are using high/low side gate driver IC’s?
@AKIOTV9 ай бұрын
100 points it is. The bootstrap capacitors for the top mosfets last about 0.25 seconds, so if the power stroke lasts longer than that, the motor can stall. (That's still quite long, I used quite large capacitors, so the driver is luckily still usable) I'm using some npn transistors for driving the mosfets, driver ics would be a better option.
@LimbaZero9 ай бұрын
@@AKIOTV Yep. Boost strap circuit was also what I think how this is now done. Also some driver IC have just integrated that. Maybe to use some chips also allow separated power source to do it. I think now it's only low side is connected to PWM pins and top side is controlled from GPIO. If all would have been PWM pins then it would just be SW update. When I design something I usually put some dummy resistors and place to cut traces If I think I need to swap some pins in future.
@benholroyd52219 ай бұрын
13:20 Heat? faster switching means more heat, and heat rises although 'bottom' and 'top' seem fairly arbitrary in this case.
@AKIOTV9 ай бұрын
Not the reason I was looking for but quite an interesting answer still, I suppose it could make a slight difference depending on the orientation of the board.
@toohardtowatch8 ай бұрын
Very cool. It's such a fascinatingly simple motor design. I'd be interested in seeing if it can be run at low RPM in conjunction with more accurate feedback. A multi-axis hall sensor perhaps, or a quadrature encoder. Or maybe holding arbitrary fixed positions, micro-step stepper-driver style. Regarding balancing, you might check out the setups to balance rc props for balancing the rotor. It's basically a levelled stand with two pair of low-resistance steel wheels for the shaft to run between. A similar arrangement of four cheap skate bearings with the shields removed might work as well? Although the shaft would probably be needed to be straitened out first. Or if you have a scope, there is a video on dynamically balancing a motor with a small speaker as a contact vibration sensor, that seems it could be applicable? Rather than referring it to a BLDC, since that seems ambiguous, perhaps call them PMSM, permanent magnet synchronous motor. That seems to be an accepted terminology. Also, if I understand correctly, the SRM stator and physical arrangement of poles are similar to a PMSM, and the relative magnetization forces between rotor and stator would seem to be functionally identical between them. Therefore the difference between SRM and PMSM is in how the process of inductively magnetizing the rotor for smooth rotation requires very different driver voltage waveform in the stators? Just to clarify.
@AKIOTV8 ай бұрын
The motor can run as slow as you want, even with simple sensors like these, but because my controller uses the top mosfets for commutation, and these can only be turned on for about 1 second at most, making the slowest speed possible about 0.3RPM. (due to something called bootstrapping, which is needed to drive high side mosfets). This is why I recommended using the low side mosfets for this instead, it avoids this problem. (Potentially there is a workaround for my poor design, in which the top mosfets are briefly turned off during the power stroke to recharge the bootstrap capacitors) In a nutshell, the big difference with a permanent magnet motor is that in a PM motor, you can have say a magnet north pole on the rotor being attracted towards the next (south) stator pole, while being repelled by the previous (north) one. This push-pull action doesn't happen in an SR motor, since rotor poles can never be repelled, only attracted. This is why phases need to be driven independently, and why the direction of the current in the coils is irrelevant. It also means the drive waveform is not a pure sine wave. For the smoothest operation ideally you want the current to be as close as possible to an ideal square wave. (Which may require a very weird drive voltage waveform). I'll keep your idea for balancing in mind, it may be useful for my boat propeller too 👍
@beatlessteve10109 ай бұрын
Fine project , I too build Arduino projects, I have never built a project with this style motor however I wonder if this is the style motor in the DJI drones
@kaleygoode16818 ай бұрын
Norty putting magnets on the rotor! Must do the inductive version, minimised hardware and physical size, maximised control... Then you can sell the PCB! Home made pancakes motors are awesome for tiny and low power PTZ control of covert CCTV cameras, for example, so low-speed uses are interesting, especially if you create a design using an axial absolute position encoder, high precision servos etc... Turbine generator projects also interesting. I hope you keep this up long enough to do all the things!!!
@dimitritzer50285 ай бұрын
you really know your stuff mate, and have a great way of explaining it! subscribed! :)
@AKIOTV5 ай бұрын
@@dimitritzer5028 Thanks :)
@m0rtifiedpenguin7 ай бұрын
Definitely replicating that motor with PWM on the high side.
@torgjerde42836 ай бұрын
Well done, nice vid with great explanations.
@AKIOTV6 ай бұрын
@@torgjerde4283 thank you :)
@garbageman39928 ай бұрын
this is such an amazing and brilliant video. I have a few questions about this too. with these motors would they run more efficiently if they were dirven with a sinusoidal voltage rather than a constant pwm? with permanent magnet motors they benefit form sinusoidal voltage input but since this has no permanent magnets would it? it still seems so since the primary reason for sine wave is motor geometry and angular velocity but would you know? and i think its really awesome how you release all your code and diagrams, i could never design something like this myself but having some designs to copy, learn from, and tinker with is great. and would it be better to do fast switching on the high side mosfet for the same reason that the diodes are necessary? if you switch the mosfet that feeds the phase quickly then it doesnt experience the high voltage from inductance. im also a novist everything I sad here could be wrong. its a very good video though.
@AKIOTV8 ай бұрын
Due to the way the motor works, the ideal current waveform is a perfectly square wave. The drive voltage to obtain this, is usually some very weird shape. The reason doing PWM on the top mosfet is better, is because the top mosfet is driven using a so called "boot strap capacitor", which limits the amount of time the mosfet can remain on. That limits the length of the power stroke if the top mosfet is used for the slow switching. More info on the motor is on my other video about the motor itself. btw thanks for watching 👍
@Hi-zf4bn4 ай бұрын
@AKIOTV what do you mean the drive voltage to obtain a square wave current profile in the SRMs stator is some "weird shape"...what shape specifically? Also, how to use shunt resistors for closed current control (measuring the coils' inductances) and driving the motor as a generator?
@georgibodurov526721 күн бұрын
Hi, i have a little experience with the SRMs. Now I'm testing 16/8 1,2kW motor. I can't see the schematic of the proposed from you controller, but i think you have problem with first starting of the motor, am i right? I asked because this was one of my problems and the trick is to put 5 - 10 pulses on the bottom MOSFETs simultaneously to charge the bootstrap capacitors. Make this sequence before starting the motor, other way is to use dc isolated power supplies for top and bottom drivers.
@InfinionExperiments2 күн бұрын
Besides your suggestions, I would also include the use of P-channel MOSFETs and IGBTs which eliminates the need for high-side bootstrapping charge pumps entirely. It makes for much simpler control and can handle long on-times without the need to interrupt power to recharge the charge pumps. I also bought a 1.2kW SRM recently, but only have a single phase driver of my own design, so I must make a 3-phase driver to test it for my pump application..
@kotrinio78686 ай бұрын
Hi, I want to create my own SRM based on your videos (they are a great inspiration), but I have some questions. What is the purpose of D3, D2, and D1? Are these diodes preventing reverse current? What is the nominal power rating of the resistors before these diodes? How can I determine the current my motor will need? I want to use the DRV8300 to drive the MOSFETs. Is it a good choice, or do you recommend other MOSFET drivers? Are C1, C2, and C3 capacitors needed, or can I use one larger capacitor at the input?
@AKIOTV6 ай бұрын
@@kotrinio7868 C1, 2 and 3 are bootstrap capacitors to drive the top mosfets. They are charged through D1, 2 and 3. The drive voltage of the high side mosfets needs to be higher than the supply voltage, or thr mosfets will not turn on. Therefore, a capacitor (say C1) is charged up to the supply voltage (24v), then, when Q10 and Q6 are opened, C1 is disconnected from ground and instead connected to the source of the mosfet, pushing the voltage on the top of C1 above the supply voltage so that the mosfet can turn on. If diode D1 wasn't there, this wouldn't happen, the capacitor would immediately discharge. The need for a bootstrapping circuit like this could be eliminated by using P-mosfets for the high side instead.
@ShafaqIftikhar-pw9ld9 ай бұрын
Very nice indeed thankyou for a great upload!!!!!❤❤❤❤
@tomgeorge37269 ай бұрын
Hi, great video on a homemade device. However your schematics are in KiCad, can you also provide an EXPORTED jpg or png of your schematic? To make just a look an easy process.
@AKIOTV9 ай бұрын
good point. I'll upload one later today.
@chris9933619 ай бұрын
I would have thought switching the low side would be the better option as N type transistors tend to be more researched, available, and capable, and to me that means they should have better switching efficiencies. That being said, I have no idea why that thinking is wrong.
@AKIOTV9 ай бұрын
This is true, but on my board n-channel mosfets are also used for the high side.
@doodledum211926 күн бұрын
wil it work better adding more magnets?
@analoghardwaretops397612 күн бұрын
This motor design does not require magnets or any other external excitation field... therefore for it's magnetic circuits , in this , it is the cheapest
@kreynolds11239 ай бұрын
So cool. Have you tried to make to change your srm motor driver into a generator?
@AKIOTV9 ай бұрын
not yet
@boots_and_a_banjo9 ай бұрын
Have you ever considered building a radar device?
@AKIOTV9 ай бұрын
Yes, I want to make one some day. It's hard though haha.
@boots_and_a_banjo9 ай бұрын
@AKIOTV do you have any recommendations for where to start? I tried to do some research but ended up nearly getting my phone hacked in the process... I'd like to try to build a ground penetrating radar but it does seem pretty tough
@AKIOTV9 ай бұрын
@@boots_and_a_banjo maybe there are some off the shelf modules/kits around you could try. Otherwise I don't know, just start with a suitable transmitter?
@melodywave39 ай бұрын
With how low of a profile this is, it could potentially direct drive a horizontal weapon on a combat robot
@AKIOTV9 ай бұрын
You mean like in something like Battlebots? Those spinny things are insane haha.
@melodywave39 ай бұрын
@@AKIOTVprecisely! they have all sorts of weight classes. this kind of motor could potentially innovate in a weapon system
@AKIOTV9 ай бұрын
@@melodywave3 This type of motor does have the ability to achieve very high speeds. The back-emf is current dependent, so as the motor speeds up, the increase in emf is tempered by the decreasing current, allowing for the speed to climb further, similar to what happens in series wound dc motors. That would be excellent for some death-spinner. I do think you'd want a better mechanical design than my motor though.
@tomtankyou12822 ай бұрын
Please take this as constructive feedback. I think your topics are great and you have good information. I have you at 2x speed and I still think you are slow to get to your point. In a way it sounds like your talking to yourself to convince yourself of your point. The art of concision is so valuable in industry, it will serve you for years to come if you put the forethought into what you are saying before starting. Put up a text blob in the first 3 sec noting any assumptions made, and move past it. Unless your stretching for time to hit an algorithm. Talking faster could help you but its not just saying words faster.
@moses54079 ай бұрын
Brilliant! Design files for the motor available? Fee?
@AKIOTV9 ай бұрын
Haha those don't exist. I had a general idea of the design in mind but the exact dimensions etc I pretty much made up as I went along.
@moses54079 ай бұрын
Ah. Ok. Thanks for the reply. I'll see what I can do and it's in with the controller files you offer. Thanks!@@AKIOTV
@moses54079 ай бұрын
And great explanation on the controller method, btw.
@moses54079 ай бұрын
@@AKIOTV how does this relate to FOC/simplefoc/Fettec sfoc? I know those are geared to PM BLDC's but are those approaches, intended to provide more smoothly modifiable sinusoidal please current, possible?
@moses54079 ай бұрын
@@AKIOTVand what would be the cost to hire you to redesign and produce the modified controller inclusive of Regen braking?
@doodledum211926 күн бұрын
hey, lets make a scooter motor?
@Bandicoot8034 ай бұрын
Out of 20 minutes of talking, only 11 seconds are honorably dedicated to the motor. How generous - NOT!!!