71–80 of 104 posts
If you are looking for a super easy way to put a motor with closed loop motion control, I highly recommend Vertiq ( https://www.vertiq.co/ ) modules. They have a built-in position sensor and microcontroller. They have firmware based anti-cogging for smooth motion. I use them in making computer controlled musical instruments by just hooking up the serial interface to an ESP32 and using the Vertiq API to handle all the…
I feel like there's a gap in the hobbiest motor market. On the one hand there are stepper motors which can withstand lots of radial load thanks to steel shafts and bearings. They also provide some relative position control and no absolute position feedback (at hobbiest prices). On the other there are servos, which typically have weak components. Plastic gears, shafts and bushings which cannot withstand radial load. B…
It's worth distinguishing between two completely different types of "servos": RC hobby servos, and industrial-type servos which are robustly built like steppers but significantly more fast, accurate, efficient, and powerful. They are hard to find in Nema 14/17 sizes but not impossible. RC servos typically have an analog or PWM signal interface. That would usually not be accurate enough for an industrial servo in posi…
If you are looking for a super easy way to put a motor with closed loop motion control, I highly recommend Vertiq ( https://www.vertiq.co/ ) modules. They have a built-in position sensor and microcontroller. They have firmware based anti-cogging for smooth motion. I use them in making computer controlled musical instruments by just hooking up the serial interface to an ESP32 and using the Vertiq API to handle all the…
Another product in this vein, Teknik motors. They're fully integrated, give them power and Connect to them via USB amd program it. Once you program it you can just use the gpio pins on the motor to wire up switches or other types of control. Super easy
Contrast with Advanced Motion Controls where it took days of coding before I could even talk to the controller. Not to knock a-m-c: their product is very fast and precise, just far less software help to get going. Manuals are complete but extremely dense reading.
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Very good point about harmonic drives and backdriveability. I had forgotten that problem.
When we build actuators in the Leg Lab, every actuator had some electrical feedback element. For example, leg length actuator had a resistive strip that was as long as the leg's travel. A fixed 'wiper' allowed us to therefore have a potentiometer, giving a leg-length-proportional voltage on the wiper when top and bottom were driven by a constant current source. This was used in a 500Hz (sometimes 1 kHz) servo loop fo…
Yes. Which is why you see encoders for sale with a zillion points per rev. Not because the position is that precise, but so that you get enough events per second to calculate velocity. Actual tachometers, which are little DC generators, are sometimes used in servo systems, but not often. The last time I saw one, it was on a mainframe tape drive.
You do want velocity and force feedback if you're doing anything beyond pick and place in a totally controlled environment. Simple preprogrammed blind movement is most of industrial robotics, though. There are fancier systems, but most of them don't sell, because the engineering cost exceeds the value add. Sometimes you see a little force feedback to get something inserted properly, but more often you see some mechanical spring setup to get the same result.
I used to be into legged locomotion, but there's no profitable market. Many of the technical problems have been solved, though. The sensors and actuators are good enough. Electric motors finally are strong enough. (It's sad that Schaft went under. Google bought them and dumped them.)
I feel like there's a gap in the hobbiest motor market. On the one hand there are stepper motors which can withstand lots of radial load thanks to steel shafts and bearings. They also provide some relative position control and no absolute position feedback (at hobbiest prices). On the other there are servos, which typically have weak components. Plastic gears, shafts and bushings which cannot withstand radial load. B…
>However I can't find them anywhere at hobbiest prices. Might put this higher up in your comment. Dynamixel robotics servos exist, but at Dynamixel prices. Weird stuff has weird prices. If anyone made a useful home robot that sold millions of units then robotics servos would get rapidly cheaper, but that hasn't happened yet.
For someone wanting to get into "making",is there a good set of starter resources like this? Software I'm comfortable with, but I'm not really familiar with all of the physical components or how to put them together, when you might use each, etc...
My issue with motors is that all of their problems seem mechanical in nature to me. I don't think anyone will really have a problem wiring up an H-bridge or whatever to run a motor. I'm personally wondering how to use the physical properties of a motor to like, move Magic The Gathering cards around, or other real world tasks. It very quickly becomes a mechanical levers / pullies / motion kinda problem, rather than el…
Ah, the task of Singulation! The answer is "with a lot of difficulty" :-)
I used to work for a large corp whose specialty is building high-speed paper handling machines for offices and industry. It is a far harder task than it seems on the surface.
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My issue with motors is that all of their problems seem mechanical in nature to me. I don't think anyone will really have a problem wiring up an H-bridge or whatever to run a motor. I'm personally wondering how to use the physical properties of a motor to like, move Magic The Gathering cards around, or other real world tasks. It very quickly becomes a mechanical levers / pullies / motion kinda problem, rather than el…
A lot of that stuff is internal industry knowledge that people learn by working for a company that already does it. It probably started out with people experimenting. You don't learn that in a mechanical engineering degree. Though printers use rubber rollers on the top sheet in the pile so the friction between the rollers and sheet is greater than the friction between sheets and therefore only the top sheet is fed by…
One problem I always run into with rotary motion: gearing. Finding gears of the right diameter, thickness, and thread pitch is always such a stumbling block for me. Most sites that sell gears to fit their motors have a small selection, and sites that sell gears are very hard to navigate (only to find out they don't sell in quantities <1,000 units). I end up having them laser cut out of HDPE online. Wish there was an…
This was PRECISELY the problem that led me to get a 3D printer. I have successfully printed many gears using PETG for my projects. Now, they are physically bigger than metal gears for the same strength, but that hasn't been an issue in my applications. Using the wishbone-style gear teeth with 3D printing is remarkably sturdy. Of course the other way is: buy motors with (metal) gears that are close to your need - then…
Buy overpowered motors close to your need, and 'transform' them by software.
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If you are doing servos and not well versed in these things, I highly recommend clearpath servos from teknic. The wiring is easy and their tuning support is very good (if the auto tune doesn’t work). If you need more power, or AC servos, I suggest DMM Dyn4 drives and servos. Finally, if you need gearboxes, stepper online has good ones that have held up well for me. Source: have built/converted several CNCs.
I'll second DMM. Unlike most servo companies, they post their pricelist, making it easy to figure out which tradeoffs you need to make to stay on budget: https://dmm-tech.com/pricing.html
in a typical 3 axis mill with 3 motors of hobby scale, you might buy a teknic IPC5 power supply and a a power hub and a bundle of cables and a backup 24v din rail supply for about $370 after tax/shipping. for a DMM DYN 4 setup, you just run AC power to drives with standard wire and terminals.
If your control box is tight, it can also pay to use AC servos because then you don't have the power supplies in your box. They may be more expensive / motor but can be way easier to deal with later.
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It's worth distinguishing between two completely different types of "servos": RC hobby servos, and industrial-type servos which are robustly built like steppers but significantly more fast, accurate, efficient, and powerful. They are hard to find in Nema 14/17 sizes but not impossible. RC servos typically have an analog or PWM signal interface. That would usually not be accurate enough for an industrial servo in posi…
Thanks, lots of helpful links there. Much appreciated. Although quickly checking, I suspect they could be over an order of magnitude more expensive than the hobbiest equivalents.
The cheapest of RC servos have a lifetime of a couple hundred hours max, even at less than half of their max torque (if their manufacturers would even specify what is the rated torque). I have one fail after two days of operation with a full rotation every 15 seconds with very light load. There are of course properly built RC servos- with serial communication for feedback, metal gearbox, brushless motor- but those start at ~50EUR-100EUR.
IMO the best bet for hobbyist is NEMA17/14 motor with a driver that has rotary magnetic encoder on them- there are cheap and open source options for that.
Next best thing would probably be a BLDC motor (optionally- geared) with SimpleFOC.