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Chac Bolay
2012.07.03, 06:00 PM
Hi guys,
I was wondering if there is a simple method to measure torque from a motor and how can it be modified to adjust my driving style.

Does magnets have the most effect on torque?

I've troubled with this issue lately, but haven't found much information.

LED
2012.07.04, 03:29 AM
Hi

A couple of years ago Haco (also here on the forum but inactive in mini-z these days) made a simple motor tester.

http://www.slotracersleuven.be/minizblog/article.php?story=20090915194833421
http://www.youtube.com/watch?v=MksOqVi5ZGo&feature=player_embedded
Sorry its in dutch, but the movie says alot.

Chac Bolay
2012.07.04, 01:19 PM
Thanks Led, great info.

To customize a motor, I want to try to understand how the magnets and comm diameter, affect torque.

Any idea of what does a motor gain and lose, when you modify any of them or both?

color01
2012.07.04, 08:18 PM
Stronger magnets will increase the pull strength of the armature coils, thus increasing torque. However, they also increase the drag on the rotor, which lowers top speed. Similar things happen with comm diameter, increasing it will give you better electrical contact fire more torque but the drag reduces your top speed.

Magnets are by far the biggest factor in torque, and you can adjust spacing between magnet and rotor to tune even finer. All the other tricks are serious fine-tuning after that.

If you want more information look for older 1/10 touring car setup guides, they are a treasure trove for brushed motor tuning. :)

Chac Bolay
2012.07.06, 02:09 PM
Brian,
Thanks, your info helps me a lot to understand motors.

Based on your comments, if i change the magnets from a PN 39T (Neo Magnets i think), for ferrite magnets from a PN 70T, torque should decrease. Right?

But, what other changes could I expect:
1) More top end rpms?
2) Less acceleration, due to decrease in torque?
3) Less drag brake, when in neutral?
4) Amps, increase or decrease?

Chac Bolay
2012.07.09, 01:30 PM
Brian,
I did some simple tests on the weekend, based on your comments.

Here are the results:
1) 32T PN rotor in its original can: aprox. 41,000 rpm, 0.75A
3) 32T PN rotor with PN gold neo magnets: aprox. 42,500 rpm, 0.79A
2) 32T PN rotor with ferrite magnets: aprox. 46,000 rpm, 0.84A

I used four recently charged batteries, a laser tachometer and a multimeter to measure current. I plugged them directly to the motor.

But how do I measure the output torque?

It seems that current is also related to the mags. Is this correct?

Jshwaa
2014.12.26, 10:45 AM
Thanks Led, great info.

To customize a motor, I want to try to understand how the magnets and comm diameter, affect torque.

Any idea of what does a motor gain and lose, when you modify any of them or both?

Hello guys,

New to the boards, but I am working towards an electrical engineering degree, and taking all elective courses about motor control, and I have loved RC technology all of my life, so I have some insight on this topic I'd like to share...

The magnetic field produced by the 'stator's' magnets do indeed affect torque, but the torque is always produced by the current flowing through the rotor's coils. That being said, for the same current flowing through a rotor coil, you will net more torque from a stronger magnet. So the magnets are a freebie for power, in terms of upgrades, from there you have to find a way to get more current to flow through the rotor coil to get more power from the motor.

You can get more current to flow through the motor by reducing the number of turns of wire on the rotor, however you do so at the cost of torque, as torque is also a product of number of turns of wire on the coil. In fact, the 'electromotive force' (linear with torque) is a product of N (number of turns) and I (rotor current), or F = NI. That being said, the only real way to get more current through the rotor is to reduced the resistance of the wire in the coil. You can purchase silver magnet wire and rewind the rotor with the same number of turns, reduce the rotor resistance, which increases net current and net torque.

The other obvious way to get more current to flow through the rotor is to increase the applied voltage to the motor. Those topics, I'm sure, are thoroughly discussed in other threads, so I won't bore you with those details here. Cheers!

If anyone is interested, I am developing a design for a motor dynamometer to be used on motors with 2mm shafts (mabuchi 130, 180, 260, 270, 280, 370) to include mini z motors. I know what some of you are thinking, and that it's been done, or there have been plenty of ways to do this that have been discussed, but I would challenge someone to show me one where they got it right. What I mean is, every method of measuring motor data (for mini z's) that I have seen on any mini-z forum, is simply measuring motor speed, voltage and current draw. They may, at best, capture a no load speed and a stall current to draw a line of operation but I have yet to see any real method of capturing all parameters of input power and output power, to include 'real' torque.

So that is what I've come to the boards to share, which is my senior design project...a real motor dynamometer for mini-z tuners. It will utilize inertia and angular acceleration to determine real torque. There are even some applications of this out there, but they still don't actually determine and compute real-time torque. They still simply measure current draw while using an inertia wheel to produce a load to the motor, while calculating speed and current draw under a known voltage. For example... http://www.mcpappyracing.com/downloads/Dyno_Owners_Manual.pdf

http://www.rctech.net/forum/attachments/electric-road/109459d1136337111-rc-dyno-question-robitronic-dyno.jpg

Both of those devices have some decent implementations to them, but neither of them actually calculate the real-time torque output of either the motor or the complete car assembly.

My solution will provide all real time motor specs (torque vs rpm, speed, and current draw curves).

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/dynamometer.jpg

Here's a pic of the solidworks drawing I made of the apparatus. This was the easy part. The rest will require some savy electrical engineering to design the control and measurement portion of the dynamometer. The electrical portion of the control system has been thought out but needs construction, testing, and final revision. The programming can then begin.

I will be utilizing an AVR microcontroller to capture speed, current, and voltage information, as well as control applied motor voltage. The data collection will need to be fast and I plan on using all of the onboard and extended SRAM of the micro to capture dynamic data throughout the motor's test runs. Stay tuned for progress. As soon as I have something notable to share, I may open a thread on it. Happy Holidays.

cowboysir
2014.12.26, 11:37 AM
I'll be following data.....I remember Jshwaa from my days of xmodding and it is cool to see someone who has developed a career from electrical interests

Have you considered how to implement this for the growing trend of 130 sized brushless motors?

arch2b
2014.12.26, 12:44 PM
i eagerly await it's own thread and progress reports! :cool: thanks for sharing your project.

Jshwaa
2014.12.26, 01:48 PM
I'll be following data.....I remember Jshwaa from my days of xmodding and it is cool to see someone who has developed a career from electrical interests

Have you considered how to implement this for the growing trend of 130 sized brushless motors?

cowboysir,

Wow, nice to know I'm remembered. :) Yea, I have always had xmod/mini-z tuning interests. I don't even own an xmod or mini-z to date. All my stuff was burnt up in a house fire and I just haven't replaced it all yet. I only had a 2 year applied science degree when I was xmod'ing. I have come a long way since then, and am a senior at Northern Illinois University, studying electrical engineering. So, I understand what needs the hobby still has, and would like to finally be able to collect real data on motors, instead of just swapping and driving until it just 'feels' like you have an optimum setup. I know that is the 'fun part' for most people, but wouldn't it be nice to have scientific comparisons of your tune-ups? I'd like to know before I wear out the screws in my chassis assemblies that my motor is at peak efficiency for whatever drive application.

Jshwaa
2014.12.26, 02:16 PM
i eagerly await it's own thread and progress reports! :cool: thanks for sharing your project.

You bet. Don't expect too much too fast. I'm a busy guy, but this ultimately has to be finished by first week of December, 2015. I haven't even pitched the proposal to my professors yet, nor have I developed a 'team' to work on it with me, so this could still possibly be a solo venture. I will get it done one way or another, whether I do it for a grade, or I do it privately.

The progress to date is conceptual, but I have purchased and/or already own the AVR development equipment (ie. JTAG programmer, ATmega2560 board (Arduino Mega), Extended SRAM, Current Sensor, tachometer photo-interrupter, power supply, h-bridge drive module, inertia wheel bearings, op-amps, resistors, caps, wire, etc.), not to mention all of the bench EE equipment for development purposes (ie oscilloscope, multimeter, variable supply, breadboards). I have two sources for the machining of the dynamometer apparatus, and have already delivered the drawings to one of them for quotation. I will be delivering the drawings to the other source soon. I'm hoping to keep the cost low, of course, but not to compromise on the quality of output. The inertia wheel is the most critical component, and must be machined to exact specification and balanced, or it will create losses and noise in measurements.

As far as programming, I am a learning AVR programmer, but have been developing small pieces of code required to gather the data of a motor test run. Specifically, after the test run, the microcontroller will have to spew out all the data in a controlled fashion, so as to allow a PC to structure it for calculating all data parameters at each point of the test run, and make sure it is all aligned and correct. I have just figured out how to get an AVR to pass the ascii character 'U' to a PC serial port, so I have a long way to go.

arch2b
2014.12.26, 02:26 PM
no worries, i've been around here for nearly 15 years and patient :)

on a club level, this would be awesome to finally be able to test batches of motors to provide a series with limited variation. much more limited than you would typically find blind purchasing at retail anyway.

lfisminiz
2014.12.26, 02:47 PM
Sounds good....

Jshwaa
2014.12.27, 11:11 AM
Notice the missing piece in the assembly drawing I posted. I'm in need of a decent motor mount. I found these on ebay...

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/picofmotorclip.jpg

I picked up a couple of them to try, but I was looking for something a little more on the metallic side, and that would allow the motor to breath a little more.

So, I need your guy's help on this. Can anyone find me a decent motor mount that I could fasten to the small platform of the dynamometer, that could universally hold 130's (small flat) or 280's (larger round) motors? I would also be happy with a 'decent' motor mount for each type, then I could design in a method of swapping the mounts for testing different motors. I've scoured the internet for them, but they all seem to be specialized for a specific RC platform and do not have screw mounts that accommodate a simple flat platform.

Anyway, you guys are more experienced with the market than I am. I go to ebay for most things, but I'm sure there are some obscure hole in the wall outlets out there too. Thanks.

arch2b
2014.12.27, 11:37 AM
check with any of the shapeways (http://mini-zracer.com/forums/showthread.php?t=39973) creator's into adapting their product. may be best to just have something made to your specs.

Jshwaa
2014.12.27, 12:01 PM
check with any of the shapeways (http://mini-zracer.com/forums/showthread.php?t=39973) creator's into adapting their product. may be best to just have something made to your specs.

Nice. Those do seem more elegant than the ones I found on ebay.

Looks like the idea of 'breaking in' motors has come a long way. I always use to take the wheels off of my xmod and connect the motor to a constant power supply at a low voltage and let it run overnight. This would also wear in the drive train quite nicely. Every couple hours or so, give the dog bone assemblies a squirt of some lube. I would also fix the steering to a hard-right or hard-left turn to wear in the AWD. You don't want to wear in your motor under too much of a load, or you will basically cook the rotor and unnecessarily wear out the brushes.

ianc
2014.12.27, 02:18 PM
Very very interesting project. While I was more actively racing a few years ago, I went through a period of winding my own motors and acquired some knowledge about building them, but lacking was a tester which could give quantitative results about the effects of various motors, gauges of wire, wrapping techniques, etc. In the absence of any real hard data on the effects of these variables, winding motors becomes a bit too nebulous to justify the large expenditure of time that it can consume. Definitely looking forward to reading about your progress,

ianc

Jshwaa
2014.12.27, 04:43 PM
Very very interesting project. While I was more actively racing a few years ago, I went through a period of winding my own motors and acquired some knowledge about building them, but lacking was a tester which could give quantitative results about the effects of various motors, gauges of wire, wrapping techniques, etc. In the absence of any real hard data on the effects of these variables, winding motors becomes a bit too nebulous to justify the large expenditure of time that it can consume. Definitely looking forward to reading about your progress,

ianc

Yes, I agree.

About your motor winding experience... Do you happen to know the magnet wire gauges used in various RC motors? I was looking for silver magnet wire, and found a source for some with 34 gauge. 1m costs $11. I wasn't sure what gauge was used, exactly, and I cannot find any definitive sources for that information. I could take apart a motor and measure, but I'm lazy.

ianc
2014.12.27, 07:35 PM
Do you happen to know the magnet wire gauges used in various RC motors?

I don't have experience with anything other than 130 motors, but for them I had settled on 30 gauge. Anything bigger and you simply couldn't get enough turns on a 130 armature. I don't think you'd want to go smaller; doesn't resistance vary as the square of the cross sectional area?

ianc

JesseT
2014.12.28, 01:12 PM
I made 1-2 years ago a flywheel dynamometer for Mini-z motors. The design was quite similar, but somewhat simpler. I'd like to courage you to also go simpler... Just a solid plastic disc directly on the motor shaft with approx 8mm thickness and 40mm diameter, must be in balance though. It had two slots through it for a led light and a detector to shine through. I had a constant voltage 5V power supply from ebay with a series resistor to mimic the batteries internal resistance and one fet to turn the power on.
Then an Arduino mega was used to read rotation speed and its derivetive, control the on/off fet, and measure the supply current through the series resistor.
A test takes only some 5s and can be repeated automatedly a number of times to average the results. All data curves (power, torque, current, efficiency) are finally transmitted to the computer via USB to be copy pasted to excel or wherever.

The most tricky part is to write a good algorith to the arduino to be fast enough and adaptive as the rpm rises rapidly. You need different parameters and algoriths for different rpms as the test progresses.

If you want to, I can adapt something like the brake-in stand for your needs.
https://www.shapeways.com/model/2833682/break-in-stand-for-mini-z-motors.html

Jshwaa
2014.12.28, 09:07 PM
I made 1-2 years ago a flywheel dynamometer for Mini-z motors. The design was quite similar, but somewhat simpler. I'd like to courage you to also go simpler... Just a solid plastic disc directly on the motor shaft with approx 8mm thickness and 40mm diameter, must be in balance though. It had two slots through it for a led light and a detector to shine through. I had a constant voltage 5V power supply from ebay with a series resistor to mimic the batteries internal resistance and one fet to turn the power on.
Then an Arduino mega was used to read rotation speed and its derivetive, control the on/off fet, and measure the supply current through the series resistor.
A test takes only some 5s and can be repeated automatedly a number of times to average the results. All data curves (power, torque, current, efficiency) are finally transmitted to the computer via USB to be copy pasted to excel or wherever.

The most tricky part is to write a good algorith to the arduino to be fast enough and adaptive as the rpm rises rapidly. You need different parameters and algoriths for different rpms as the test progresses.

If you want to, I can adapt something like the brake-in stand for your needs.
https://www.shapeways.com/model/2833682/break-in-stand-for-mini-z-motors.html

JesseT,

Nice post. I too am going to use an Arduino Mega, however I will be coding it directly in assembly, using a JTAGICE MKII programmer. I have done many projects with Arduino using the Arduino IDE, but I find it somewhat cumbersome, and the programming environment is very limited with next to zero debugging tools. Manipulating the ATmega2560's registers directly will inherently provide more speed for data gathering. For every half-rotation of the motor, I will be taking a snapshot of time between half-rotations, which will provide speed and acceleration information, and current. The voltage will be known, as well as the moment of inertia that the inertia wheel imposes on the motor's rotation. With these parameters, I can calculate the dynamics of the motor's run from zero to full speed. I don't plan on filling the entire 16K of SRAM with run data, but just in case I will be using an external SRAM chip to get full use of the 2560's external SRAM. Some of the motors spin pretty fast, so it's better to be safe than sorry as far as data storage, and the SRAM chip only costs $4. The 2560 has plenty of IO for connecting it too.

The trick to collecting motor data fast is to use interrupts ;)

Here's a pic of the humble beginnings...

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/IMG_5744.jpg (http://s83.photobucket.com/user/Jshwaa/media/Dynamometer/IMG_5744.jpg.html)

Got the motor voltage code figured out, so as to provide either a 4.8V, 6V, or 7.2V test run, because these are the most commonly used voltage levels used in the hobby, and what most mini-z motors are built for. As far as the power supply for the entire setup, I will be using a 750W gaming PC power supply, which has 12V and 5V outputs, to drive the digital and motor separately, and provide the motor with up to 27A.

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/picofpowersupply.jpg (http://s83.photobucket.com/user/Jshwaa/media/Dynamometer/picofpowersupply.jpg.html)

I bought the fastest photo-interrupters I could find on digikey, so I shouldn't reach a speed where there photo-interrupter's output cannot respond with sharp transitions.

As far as your inertia wheel...I believe that a plastic disc of the dimensions you provided will not provide enough inertia to draw torque from the motor that can be measurable. You need mass, and radius to create the moment that will load the motor. The load that any imbalance and whatever bearings you used alone will become a loss and noise factor, not to mention the noise and inefficiencies of the motor itself, which cannot be greater than the factor of inertia in the system or it becomes too hard to measure and calculate. The signal to noise ratio would not be good enough. If you look around at inertia dynamometers, you will find that they use a solid metal disc of a decent radius, or large metal roller which has hella-mass. You also mentioned how quick your test runs were. This is partly due to how small the motors are, but again, if you were properly loading the motor with enough inertia, it would have taken a little longer for the motor to reach full RPM, thus prolonging the test run a little and making it easier to gather data of the motor's acceleration towards top speed. The wheel should be enough load to make the motor work, but not too much to hinder its potential top speed. Also, testing and retesting a motor, then averaging the results is a decent approach if the data is erratic and inconsistent due to timing constraints, but with each run the motor gets warmer, draws less current for the same voltage applied, and nets less torque output, so that requires letting the motor cool to same temp between each run which is a little time consuming. I am hoping to have a resolute data set with one run. We'll see.

I like this simple-h h-bridge though. Has a built in current sensor.

Jshwaa
2015.01.19, 08:53 PM
Just a little update...

Got a manufacturer making the inertia wheel for the dynamometer...

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/dynamometer.jpg

Designed the PCB for data collecting, to include the full 64KB of SRAM that the ATmega2560 can address, and implemented current sensing.

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/PCB.jpg

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/IMG_5749.jpg

And the assembled control and measurement unit...

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/IMG_5752.jpg

Also ordered one each of PN Racing 32T and 70T motors for testing. They are on the opposite sides of the spectrum from each other in terms of torque/speed, so testing should produce some noticeable differing results.

Still a lot of code work to do....stay tuned...

LED
2015.01.21, 12:35 AM
Hi

What kind of shunt resistor are you using to measure the current.
I am actually building my own rig. I am using a PIC for the brains.

Good luck, looking great!

Jshwaa
2015.01.21, 09:52 AM
Hi

What kind of shunt resistor are you using to measure the current.
I am actually building my own rig. I am using a PIC for the brains.

Good luck, looking great!

Thanks!

Yes, for the current sense resistor, I am using an 'Ohmite CS3 Series' resistor, which is 0.05 ohm, 3W, 1% power resistor.

Digikey Part #: CS3FR050E-ND
Cost: $14.06

How do you plan on collecting/processing/displaying your data?

Happy Designing! Please come back and share your progress.

LED
2015.01.21, 04:15 PM
Thanks!

Yes, for the current sense resistor, I am using an 'Ohmite CS3 Series' resistor, which is 0.05 ohm, 3W, 1% power resistor.

Digikey Part #: CS3FR050E-ND
Cost: $14.06

How do you plan on collecting/processing/displaying your data?

Happy Designing! Please come back and share your progress.

Thank you for the nr.
I am still in the "thinking about it" and research phase :-)
I want to use to the PIC to drive the motor with matching PWM as the mini-z. I will also be using the same FET's to drive it. I am going to use a shunt for current measurement, a laser or an IR pair for RPM measurement. And a shunt for current measurement. I don't really think of it as a motor dynamo, more as a motor compare tool. I will also be adding a second slave motor with different parallel resistors switched by the PIC. I want to measure all the parameters at different stages. For instance 30% power ==> measure current and RPM wih no load, load 1, load 2, load 3,....Then increase to 40 %, repeat all the measurements, etc...
I want to send all my measurements live via RS232 to excel which will then after everything is finished make a graph of it.
The RPM under different loads represents the torque the the motor has for a certain % of power.
Hence is why I call it a compare tool. Because no real torque is measured or calculated, but you are able to compare multiple motors with each other. And for instance choose a motor with alot of low power torque for small tracks, and a motor with more high end torque for a track with large straights.

Anyway, it's all just plans for now. But the motor drive an rpm measurement should be easy to do. The RS232 and current measurement I have never done.

JesseT
2015.01.21, 04:41 PM
Thank you for the nr.
I am still in the "thinking about it" and research phase :-)
I want to use to the PIC to drive the motor with matching PWM as the mini-z. I will also be using the same FET's to drive it. I am going to use a shunt for current measurement, a laser or an IR pair for RPM measurement. And a shunt for current measurement. I don't really think of it as a motor dynamo, more as a motor compare tool. I will also be adding a second slave motor with different parallel resistors switched by the PIC. I want to measure all the parameters at different stages. For instance 30% power ==> measure current and RPM wih no load, load 1, load 2, load 3,....Then increase to 40 %, repeat all the measurements, etc...
I want to send all my measurements live via RS232 to excel which will then after everything is finished make a graph of it.
The RPM under different loads represents the torque the the motor has for a certain % of power.
Hence is why I call it a compare tool. Because no real torque is measured or calculated, but you are able to compare multiple motors with each other. And for instance choose a motor with alot of low power torque for small tracks, and a motor with more high end torque for a track with large straights.

Anyway, it's all just plans for now. But the motor drive an rpm measurement should be easy to do. The RS232 and current measurement I have never done.

A brushed slave motor will never be stable in a long run because of commutator/brush wear and temperature. I would go for a brushless slave motor if you don't want to go the inertia dynamometer way. The downside is that you have three poles to load.

Also, keep in mind if you want to match the shunt resistor to the actual battery internal resistance. Otherwise you will get data that is far too optimistic.

Jshwaa
2015.01.21, 05:04 PM
I want to send all my measurements live via RS232 to excel which will then after everything is finished make a graph of it.

The RS232 and current measurement I have never done.

What actual PIC controller/board do you plan on using? Is it programmed via USB and provide RS232 serial via the same USB port?

That is the beauty of the Arduino Mega. Although I am not programming it with the Arduino IDE, rather Atmel Studio, I can use the on-board USB connection as a serial port which makes connecting to a PC no problem. I will probably find it more tedious to write the Microsoft Visual Studio application to receive the data, process it, and display in a useful format. I have already worked out a lot of what the Arduino will need to do to control the motor and collect the data.

I don't really think of it as a motor dynamo, more as a motor compare tool.

With my setup, I will allow the user to set the voltage to one of the 5 most popular 'micro' RC setup voltages (ie. 4.8V, 6.0V, 7.2V, 8.4V, or 9.6V). Whatever voltage it is set to will be constant throughout the test run. Every half turn of the motor will be timed to find speed, and the difference between the times will be calculated to acceleration. Also, every half turn a snapshot of current will be taken and logged with the speed. When the motor is no longer accelerating, the test run is done. Plotting the speed vs. current vs. torque with the known voltage will provide power and efficiency information.

Hence is why I call it a compare tool. Because no real torque is measured or calculated, but you are able to compare multiple motors with each other. And for instance choose a motor with alot of low power torque for small tracks, and a motor with more high end torque for a track with large straights.


I understand your objective, however your comparisons will only mean something to you, in terms of your setup instead of the universal language of SI units. Without any calculations in those terms, you are still comparing motors by swapping them in and out of an actual Mini-Z at best. I have dabbled in the slave motor approach...

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/Picture004.jpg

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/Picture007.jpg

Instead of dropping a static resistance across the load motor, I put a fet in series with the load motor and a power resistor. I would PWM the fet, and the higher the duty cycle the motor torque load the motor imposed on the motor under test, because it was like a fully loaded generator. The lesser the duty cycle, the lesser the motor was loaded, as the generator became less loaded and more 'free wheeling'. So, you could log the current drawn from the motor under test from 0% PWM to 100% PWM on the load motor and graph the results.

Here's a schematic of what I'm referring to.

http://i83.photobucket.com/albums/j314/Jshwaa/Dynamometer/torqueloadcurrentsense.jpg

A brushed slave motor will never be stable in a long run because of commutator/brush wear and temperature. I would go for a brushless slave motor if you don't want to go the inertia dynamometer way. The downside is that you have three poles to load.

Precisely. I decided to drop this approach because of the thermal effects on the load motor and did not pick the coupled-motor approach back up. I made a small app where I could vary the torque load while monitoring the current generated by the load motor and it would vary quite a bit as the load motor heated up. The inertia wheel should provide a good mechanical platform to collect decent data as long as I can calculate the inertia of the wheel accurately and characterize the damping effect of the ball bearings I'm using.

LED
2015.01.22, 02:51 AM
I forgot to mention the most important part I think :-p
I am doing this because I only started using PIC's like 1 year ago. And I wanted a project with a challenge :). Also I am going for low budget.

I am very well aware of the limitations of using a slave motor. But like I said it is a comparing tool and it is not my intention to compare it to results from somebody else. Also it is not my intention to compare a motor I did 4 months ago with a new one.

I will be using a PIC 16F684. It does not have USB or RS232 suppport so I will be making my own routine. I only need to transmit from the PI to excel. No feedback needed.

Thx for the info, it is very interesting.

Jshwaa
2015.01.22, 08:08 PM
I forgot to mention the most important part I think :-p
I am doing this because I only started using PIC's like 1 year ago. And I wanted a project with a challenge :). Also I am going for low budget.

I am very well aware of the limitations of using a slave motor. But like I said it is a comparing tool and it is not my intention to compare it to results from somebody else. Also it is not my intention to compare a motor I did 4 months ago with a new one.

I will be using a PIC 16F684. It does not have USB or RS232 suppport so I will be making my own routine. I only need to transmit from the PI to excel. No feedback needed.

Thx for the info, it is very interesting.

Cheers, bro! Sorry if I sounded discouraging in my previous post. I just know that you're going to finish this project and be excited to share your results. The comparisons should be interesting nonetheless, especially when you are tuning.

I'm looking at the datasheet for the PIC you called out and I don't see that it supports any serial Tx/Rx UART ports. This will make communicating to a PC extremely difficult, as you will have to explicitly control a bit for transmitting and another bit for receiving, and the code work involved will be pretty daunting. Start reading up on your ASCII and RS232 protocols and how to create a format for pushing a byte out one bit at a time, with a specific timing(baud rate).

To get some really cool projects off the ground, fast, look into Arduino. Very easy to code, and plenty of I/O. You can literally get a program running that spews data to your PC serial port in minutes, and with minimal coding.

LED
2015.01.23, 12:15 PM
Cheers, bro! Sorry if I sounded discouraging in my previous post. I just know that you're going to finish this project and be excited to share your results. The comparisons should be interesting nonetheless, especially when you are tuning.

I'm looking at the datasheet for the PIC you called out and I don't see that it supports any serial Tx/Rx UART ports. This will make communicating to a PC extremely difficult, as you will have to explicitly control a bit for transmitting and another bit for receiving, and the code work involved will be pretty daunting. Start reading up on your ASCII and RS232 protocols and how to create a format for pushing a byte out one bit at a time, with a specific timing(baud rate).

To get some really cool projects off the ground, fast, look into Arduino. Very easy to code, and plenty of I/O. You can literally get a program running that spews data to your PC serial port in minutes, and with minimal coding.

I know it doesnt support UART but I have examples for it. it actually looks simpler then I tought. I dont need to receive anything, only transmit so that makes things alot simpler.
I know about Arduino, my brother has one. But I also make really small projects that need to be portable. And the arduino simply isn't suited for that. That is why I started with PIC's in the first place. My first was a light kit for the mini-z that reacts to throttle brake and the turn signals. Also a exhaust light was included with randomized patterns. The prototype worked, I just never made one for a car :-p

Jshwaa
2015.01.23, 02:30 PM
But I also make really small projects that need to be portable. And the arduino simply isn't suited for that. That is why I started with PIC's in the first place.

Well, what I should have said was that you should go with an AVR micro, instead of a PIC if you want UART support. Any Arduino at heart is simply an AVR microcontroller. That being said, AVR makes the smallest most powerful microcontrollers on the market. Look up the ATtiny13. 8-pin SOIC that supports interrupt driven PWM and UART, and an internal 20MHz clock.

We may be getting our wires crossed with 'development boards' vs. 'microcontrollers'.