Recent Posts

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Projects, Designs, and Technical Stuff / Re: Control of 2 CAN Open DS402 motors on a single shaft

« Last post by Simon on Today at 02:30:57 pm »

Ok, i'm gonna ask another "stupid" question: Does the system actually NEED two seperate motors?  It's going to be cheaper, simpler, and more robust to just fit one motor to do the work if you can!

Ie, rather than have to invent some complex control archecture to suit some dynamic load you may never get a chance to properly validate, just simplify the system to one drive node!!

hahahahahahahahaha, you know me, if I could have, I would have. Various factors drove the 2 motor solution. It was mechanically simpler (yes I still have that problem where the electronics fixes the mechanics problem but I get some thanks now) and we struggled to get powerful enough motors, both single and dual have been used in the past, with hydraulic motors they are plumbed in series and yes I considered that electrically as well.

The drives have many settings and bits of information available. and looking around the internet I have seen some examples of how these sorts of drives are used to construct complicated machinery with the control being offloaded to the motor drives. For example conveyor belts is where I first heard of this speed control one motor and have one or more torque controlled helper motors. Our application is similar. another was a paper mill with one roll being unwound onto another with a motor winding and another holding back the unwinding roll with a torque that it calculates from the output of a pressure sensor on the paper connected directly to it rather than through a main controller.

So I realized that I have been missing a trick with these motors worrying about if my little 48MHz M0+ micro can keep up with all of the messages on the bus that I need to do really fast control, I should simply let the motors work for me and just send the sync message as fast as I like as I don't have to process much data coming back. The motor drivers have a 120MHz ARM M4 each.

At first I wondered why on earth I would want to know the motors target_torque, all I care about is that I sent it a torque_demand  and that it gives me what was demanded of it, if anything I would only use the actual_torque value to see what is happening. Now that I start to see how these drives can be used it makes sense.

If I can have the speed controlled motor change speed at a rate of 0-max in 5s that is well slow enough I think for a motor that is taking the target_torque of that motor to keep up would be easy enough. With sync messages sent every few ms long before the speed controlled motor has finished making an adjustment if it is transmitting it's target_torque the helper motor matches that. This should mean the speed motor now sees less load so adjusts to suit. I don't know how far into the future the tarqet_torque is but after a few cycles I would expect the two motors to work together quite well as the speed motor quickly gets used to the reduced load. It would really be about that first cycle where the torque motor has to come in and the speed motor gets a bit of a surprise. once both have a similar torque value I would hope that the speed motor would start to see half the load as the required change in load would be quit slow.

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Projects, Designs, and Technical Stuff / Re: Build or buy? Multi-level vessel temperature logger

« Last post by mag_therm on Today at 02:28:38 pm »

https://www.watlow.com/products/Sensors/Thermocouples/Multipoint-Thermocouples

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Beginners / Mobile Stepper Motor Driver Project / Use of membrane buttons

« Last post by Jasonkandefer on Today at 02:28:16 pm »

Hey! New here, I’ve been a lurker for a while and decided to make an account and ask a few questions.
About a year and a half ago, I came up with an idea for a tool that I could use at work (commercial HVAC technician) to be able to calibrate and diagnose issues with Electronic Expanion Valves. These “EEVs” use a stepper motor to open or close valves to meter refrigerant. I’ve dabbled with Arduino and breadboards before this, and was finally able to come up with a working prototype that used numerous premade pcbs (boost/buck converters, Arduino nano boards w/ breakout pcb, external battery life indicators etc) obviously having this many separate boards all being manually wired together was not a good option as it was fragile and buck/boost converters were melting if I hooked up to an EEV that drew a tad to much power. I dabbled with having guys on fiver make me some actual PCB prototypes, but after spending 5-700$ on having boards ordered an assembled through JLPCB, I still didn’t have a working prototype, which leads me to the old saying “if you want something done right do it yourself” so I downloaded kicad, started watching youtube videos, and began prototyping simple PCBs until I started getting the hang of it. Well, 7 months after downloading kicad I have a pretty complex PCB using an ATMEGA328P-AU & an A4988 stepper driver IC. The atmega chip produces a contact 330Hz square wave for the a4988, and also controls the button logic for enable/direction & speed controls MS1,2 & 3. The board is powered from a 3S AAA 3.7v battery pack delivering 12.4VDC to the PCB, an ATTINY and a low quiescent linear regulator is used for turning the device on an off, the ATTINY stays in sleep mode until the button connected to one of its pins is pressed and held for 1 Second, it then wakes up, and outputs 5v to the gate pin on a SOT223 2N2222 Transistor that makes contact between battery ground, and the ground plane on the PCB, enabling 12VDC to the rest of the board. Another 1 second press will then shut the board off.

My real question here is since I also dabble in Cad, (solidworks & shapr3d) I’ve designed a case for this project, but I want it to be sleek, and durable. So I’d like to implement the use of a custom membrane switch keypad. I’ve looked at some websites and seen I can have them prototyped for around 300 USD. Has anyone had a custom membrane keypad made? I have & can use photoshop to design the button graphics, and can design the schematics for the buttons aswell, would this cut down cost? What is the process of having these keypads made? Any suggestions for an easy to work with company for making these?

Thanks. 

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Beginners / Any off-the-shelf clock using DS3231?

« Last post by hap2001 on Today at 02:28:03 pm »

Hi.
I'm looking for a very accurate home clock, and many search results point to DIY projects using DS3231, they say it's the most accurate chip you can get without cost a leg.
I just want to know, is there any commercially available clock that have DS3231 as it's gut, or something else with equal or even greater accuracy?
Thanks.

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General Technical Chat / Re: piano switch

« Last post by reboots on Today at 02:27:28 pm »

This is an on-off switch, identical in function to a top-actuated DIP switch. The datasheet doesn't explicitly state that, but the listed typical applications are a clue: "Address switch for industrial controls" and "Logic switching for computers and peripherals" would not ordinarily use a momentary switch.

Datasheets will call out "momentary" or "MOM" for a momentary switch. Another convention is to use parentheses to denote a momentary function. For example OFF-ON and OFF-(ON) would indicate two switch variants, with the latter being momentary.

I have never seen a momentary switch of this type. The best I can suggest is a tactile pushbutton switch.

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Projects, Designs, and Technical Stuff / Re: Opamps - Die pictures

« Last post by magic on Today at 02:27:00 pm »

Would it be ok for you if I put your schematic on my website?

OK

By the way, I forgot to mention that there is one error here which I am not going to correct because I'm too lazy to use the full, four-terminal MOSFET symbol.
In integrated CMOS technology the bodies are often tied to one of the supply rails, not necessarily to the source, and this appears to be the case here.

I noticed that IC designers often use simplified symbols similar to NPN/PNP which don't even show the body at all, unless they are doing something unusual with the body of one particular transistor. Maybe I should add these symbols to my LTspcie...

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Projects, Designs, and Technical Stuff / Re: No interrupt from AS6501...

« Last post by Denge on Today at 02:26:06 pm »

Hi All,

Porting this code to the dsPIC33CK64MC105 MCU would take me ages I guess. On top of that I'm a novice in programming C.... So trying to port all this code would bring me further away than I'm now!
By now I checked and rechecked the hardware and found it should be ok, played with some different setups and added a 100 µs delay right after the power on reset and a 200 µs delay after the configuration write but still no interrupt going low! :-(
The config I use now is:
cfg0: 0x95, cfg1: #0x15, cfg2: #0x00, cfg3:4:5, 100000, cfg16, #0x04
The refclk is 10 MHz.
Conclusion: I'm lost

Greetings,

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3D printing / Re: could anyone please print me a microscope Head adaptor ring

« Last post by davebb on Today at 02:25:46 pm »

Hi Again, With the grub/Thumb screw on the stand to hold the ring from turning, This works well and does not mark the adaptor ring,
Thanks Dave 2E0DMB

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Microcontrollers / primitive serial CLI / Console for embedded systems - Ideas for implementation?

« Last post by Warhawk on Today at 02:25:02 pm »

Hi guys,
I am wondering if any of you could provide some inspiration. I have a small test system for the internal lab use. The system aquires ceratain digital data and prints them to the PC over a serial port.
I am going to implement a console/CLI. The interface shall be human readable but also needs to interact with python.

Typical commands would be:

Code: [Select]

reset
buffer_size xxxx // 0-1024
adc_filter  x //off, type-1, type-2
trigger... and many more

As you can see, some commands come with parameters, some don't.

I see that there are two possible methods. Using variable arguments and parse the string (A) or asking for the parameter separately (B).

Code: [Select]

(A.1) CMD>buffer_size 1024 <enter>
(A.2) OK
(A.3) CMD>

(B.1) CMD>buffer_size <enter>
(B.2) PRM>1024 <enter>
(B.3) OK
(B.4) CMD>
PS: I do not care much about the memory footprint, portability, or speed. However, readability and ease of use are important for me. Somebody else, or I, should be able to understand and modify the code base in future :-) I generally need the KISS principle.

What are your favorite options? Share links, github or just your ideas.

I will start:
https://dojofive.com/blog/embedded-command-line-interfaces-and-why-you-need-them/

https://interrupt.memfault.com/blog/firmware-shell

Thanks in advance!

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Projects, Designs, and Technical Stuff / Re: a high side load switch made from n channel and p channel mosfet working princip

« Last post by BennoG on Today at 02:23:33 pm »

Yes that is a possibility, myne had to work from 12V to 50V, so that made it a little more complex.

Benno