Trouble with brush less motors and Power.

V

vortix

Well-Known Member
I have been having a problem with my motors. when i try to turn them on, i can increase all quad motors to about 30% or so and some of the motors would turn off. im using arduino nano.

this is the battery: https://www.amazon.com/gp/product/B07351J77T/ref=ppx_yo_dt_b_asin_title_o06_s01?ie=UTF8&psc=1
the ESC: https://www.amazon.com/gp/product/B07CXSGP4X/ref=ppx_yo_dt_b_asin_image_o09_s00?ie=UTF8&psc=1
the PDB:https://www.amazon.com/gp/product/B071K945GL/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
The motors: https://www.amazon.com/gp/product/B07KPDKV89/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

all motors get the same write. which is Servo.writeMicroseconds (**somee microseconds);

i think this a hardware issue. does this setup look right or is something missing? i also tried replacing the PDB and ESC with a 4 in 1. still same.
 
Dugdog47 said:
I'd say your setup looks good. Just guessing, maybe too much voltage for those tiny motors?
Click to expand...

they are rated for 7.4 volts 2S. i would be glad to give them a 3V battery since its lighter but thats not what the specification says. oh by the way, i switched the PDB with one that has a Led on it and when i reach that point where the motors shut off, the led of the PDB starts to dim. im not a hardware expert but im sure that would be helpful info.
 
Dugdog47 said:
Hmm, have you tried flying with props on yet? Sounds like your motors may be trying to pull more amps than your battery can supply. I found this thread in RC groups interesting on the subject:

Does a brushless motor have a rev limit? - RC Groups

Discussion Does a brushless motor have a rev limit? Electric Power Systems
www.rcgroups.com www.rcgroups.com
Click to expand...

but how do i fix that? Motors ask for 2S 7.4v. it seems strange that the battery that the motors asks for is too heavy to carry. right now, they turn off before getting to that point where they can take off. also, i remember that the issue was recent. im sure that at one point in my testing a few weeks back, i managed to get them to full power just fine.

also, the PDB says 3S minimum but the battery is 2S. i thought that might be the issue but i tried using a 4 in 1 ESC that takes 2S but no change.
 
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vortix said:
but how do i fix that? Motors ask for 2S 7.4v. it seems strange that the battery that the motors asks for is too heavy to carry. right now, they turn off before getting to that point where they can take off. also, i remember that the issue was recent. im sure that at one point in my testing a few weeks back, i managed to get them to full power just fine.
Click to expand...
Since you're using writeMicroseconds you're sending a servo or PWM signal to the ESC if the ESC calibration isn't correct for high and low values then it will incorrectly map the input signal to a throttle percentage. The light dimming does sound like whatever regulator is giving that led power is being stressed. If you can get some pictures of the setup and/or schematic that will help make sure your batteries voltage is good too (charged above 3.7V per cell don't let any cell get below 3.0V when being used, or under load, or it will damage them)
 
wafflejock said:
Since you're using writeMicroseconds you're sending a servo or PWM signal to the ESC if the ESC calibration isn't correct for high and low values then it will incorrectly map the input signal to a throttle percentage. The light dimming does sound like whatever regulator is giving that led power is being stressed. If you can get some pictures of the setup and/or schematic that will help make sure your batteries voltage is good too (charged above 3.7V per cell don't let any cell get below 3.0V when being used, or under load, or it will damage them)
Click to expand...

i dont know how to calibrate the ESC. when i was testing them, they seem to be syncing up on their own. not sure about that anymore.

here is the schematic.sche.png
 
wafflejock said:
Since you're using writeMicroseconds you're sending a servo or PWM signal to the ESC if the ESC calibration isn't correct for high and low values then it will incorrectly map the input signal to a throttle percentage. The light dimming does sound like whatever regulator is giving that led power is being stressed. If you can get some pictures of the setup and/or schematic that will help make sure your batteries voltage is good too (charged above 3.7V per cell don't let any cell get below 3.0V when being used, or under load, or it will damage them)
Click to expand...

ok i found some people talking about C-rating and Amps and honestly, i have no clue what they are talking about. hardware is a weakness of mine and i followed a few guides to get to this build so i thought i was good to go :S.

would getting a battery with higher mAh help ?
 
vortix said:
ok i found some people talking about C-rating and Amps and honestly, i have no clue what they are talking about. hardware is a weakness of mine and i followed a few guides to get to this build so i thought i was good to go :S.

would getting a battery with higher mAh help ?
Click to expand...

meh, ill just get another battery with more mAh. its cheap. thank you for your help. i just want to say you guys are much more helpful an chill than other forums. i appreciate it, thank you. stay rad! :D
 
Yah couple of issues. So the Arduino library won't necessarily write the PWM signal without delay so if you say 1500 microseconds it may send 1600 or more instead so you'll need to do the calibration or mess with those numbers a bit to get actual low or high values to use. Regarding the battery extra capacity (mAh) helps with time in the air and C rating is used in combo with capacity to tell max discharge 10C means 10 times capacity in Ah is max discharge (for example 1Ah or 1000mAh battery with 10C can discharge 10A continuous current, if it were 20C or it were 2Ah with 10C then can do 20A continuous discharge rate without damaging the cells). This has to do with how cells are made and internal resistance or resistance to current flow within the cell itself, higher amperage than tested for will result in hotter battery and more damage. Really though generally speaking watching the voltage on the cells is most important, if the C rating is "too low" you will see the voltage drop significantly when drawing amps from the battery/cells.
 
Can see some data here from my esk8 setup using lipos (10S or around 40V) and 6374 size motor

Main thing to note is blue line (voltage) dips as the red lines (amps at motor and battery) are high and voltage recovers when off the throttle (red lines flat then can see some voltage recovers)

Avg Speed 0kph, Distance 0.8km, Energy 4Wh

https://metr.at/r/6EGoI
metr.at metr.at
 
wafflejock said:
Can see some data here from my esk8 setup using lipos (10S or around 40V) and 6374 size motor

Main thing to note is blue line (voltage) dips as the red lines (amps at motor and battery) are high and voltage recovers when off the throttle (red lines flat then can see some voltage recovers)

Avg Speed 0kph, Distance 0.8km, Energy 4Wh

https://metr.at/r/6EGoI
metr.at metr.at
Click to expand...

i switched to a 250 mAh and 20C battery which is suppose to be weaker and the motors feel faster but they still turn off at some point.
to be more exact, they turn off at around 1250 Microseconds write up.
 
Yah would see if you can get the ESCs to calibrate to the high and low values the Arduino (or other mcu) is sending typically calibration is just send 2000 usec pulse with the ESC turned off (no power) then power the ESC (should hear motor beep once or twice) then send 1000usec pulses and should hear confirmation beep on the motor that will set high and low values. Also check if motors or ESC are getting hot to the touch (not just warm but hard to touch without pain) can make sure nothing is just shutting off from thermal cut off or the like.

Also if you can get a dso oscilloscope or access to any sort of oscilloscope can hook it up to the signal output pin on your MCU/controller board and see what the PWM signal looks like for yourself and if the width of it looks right (when you send 1000usec is it actually pulsing 1000usec on or is it more like 1100 or 1200)

Oscilloscope apps on phone using mic input as the scope wire might work too but can get DSO diy kit for around $35 too and not risk frying something in your phone :D
 
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wafflejock said:
Yah would see if you can get the ESCs to calibrate to the high and low values the Arduino (or other mcu) is sending typically calibration is just send 2000 usec pulse with the ESC turned off (no power) then power the ESC (should hear motor beep once or twice) then send 1000usec pulses and should hear confirmation beep on the motor that will set high and low values. Also check if motors or ESC are getting hot to the touch (not just warm but hard to touch without pain) can make sure nothing is just shutting off from thermal cut off or the like.

Also if you can get a dso oscilloscope or access to any sort of oscilloscope can hook it up to the signal output pin on your MCU/controller board and see what the PWM signal looks like for yourself and if the width of it looks right (when you send 1000usec is it actually pulsing 1000usec on or is it more like 1100 or 1200)

Oscilloscope apps on phone using mic input as the scope wire might work too but can get DSO diy kit for around $35 too and not risk frying something in your phone :D
Click to expand...

should i do this only one time? or every start up?
 
wafflejock said:
Should just be a one time thing think the ESCs have a bit of eeprom that stores whatever the calibration values are I believe.
Click to expand...

ill try that, thank you :D .
you know i asked that before but i haven't got an answer, i just wondering if you happen to know. How do i drive 4 DC motors that are brushed through the arduino? i wanted to try building a really tiny quad but im not sure how to do the PDB's work for these motors. i thought maybe i can get a 3.7v 1S PDB but i don't think they exist. i don't think i can just plug in the arduino directly either.
 
You'll have to buy a brushed fcb, banggood has them for cheap. They are easy to fry so when your soldering those in remember one thing: don't f@#k up lol.
 
Yeah for sure could just buy a brushed FC and use that definitely the easier/better option to just get something flying. For the sake of just experimentation/learning you could drive any DC motor fowards and backwards using an "H-bridge". Basically an H-Bridge takes DC power input from the lipo battery and has control signals from the arduino that when set to high or low in different combinations will cause the current to flow one way or another. Typically brushed FCs will just allow current to flow in one direction I believe so it's important to get the wiring correct or the motor will spin backwards but if using H-Bridges you can pretty easily control forward and backward motion

IMG_20180924_100143_2.jpg


I literally bolted the little bot together to run off a 2S lipo battery and uses an arduino to control the current to two geared motors to drive this little wooden platform thing around. It uses the ultrasound sensors you can see in front and on the sides and back to attempt to avoid things and just wanders around aimlessly otherwise.

I'm just using the L293D chip for the Dual H-Bridge to control both DC motors in two directions but there are some nice breakout boards if you don't want to use a breadboard or "dead-bug" wiring to hook the IC up to your motors, power, and MCU

Qunqi 2Packs L298N Motor Drive Controller Board Module Dual H Bridge DC Stepper For Arduino - - Amazon.com

Qunqi 2Packs L298N Motor Drive Controller Board Module Dual H Bridge DC Stepper For Arduino - - Amazon.com
www.amazon.com

I don't think the breakout board with heatsink and all the extra weight is needed can get the chips themselves too though

Amazon.com: PIXNOR 10pcs L293D DIP 16-pin IC Stepper Motor Drivers Controllers (Black) : Industrial & Scientific

Amazon.com: PIXNOR 10pcs L293D DIP 16-pin IC Stepper Motor Drivers Controllers (Black) : Industrial & Scientific
www.amazon.com

learn.adafruit.com

Arduino Lesson 15. DC Motor Reversing

This is Lesson 15 in the Learn Arduino Adafruit series. In this lesson, you will learn how to control both the direction and speed of a small DC motor using an Arduino and the L293 motor driver chip.
learn.adafruit.com learn.adafruit.com

The voltage regulator on Arduino can step down voltage from 2S so think I just fed power into the VIN line don't go to 5V line unless feeding regulated 5V already (this bypasses the Arduino regulator before passing power to the Atmel chip itself which expects 5V for 16MHz operation).

---

Some additional thoughts... Can run off of 1S if using a Arduino Pro Mini 3.3V version at 8MHz it will work reliably until the battery is down to around 3.3V maybe less but complicates some things in terms of programming and working with other 5V things can cause problems. You can always use a "boost converter" to up the voltage or a "buck converter" (or less efficient linear regulator or voltage divider) to drop the voltage so you can always adjust the voltage (can also get a "buck/boost in one" that can up or down the voltage to some target from some source but always some losses)
 
wafflejock said:
Yeah for sure could just buy a brushed FC and use that definitely the easier/better option to just get something flying. For the sake of just experimentation/learning you could drive any DC motor fowards and backwards using an "H-bridge". Basically an H-Bridge takes DC power input from the lipo battery and has control signals from the arduino that when set to high or low in different combinations will cause the current to flow one way or another. Typically brushed FCs will just allow current to flow in one direction I believe so it's important to get the wiring correct or the motor will spin backwards but if using H-Bridges you can pretty easily control forward and backward motion

View attachment 5190


I literally bolted the little bot together to run off a 2S lipo battery and uses an arduino to control the current to two geared motors to drive this little wooden platform thing around. It uses the ultrasound sensors you can see in front and on the sides and back to attempt to avoid things and just wanders around aimlessly otherwise.

I'm just using the L293D chip for the Dual H-Bridge to control both DC motors in two directions but there are some nice breakout boards if you don't want to use a breadboard or "dead-bug" wiring to hook the IC up to your motors, power, and MCU

Qunqi 2Packs L298N Motor Drive Controller Board Module Dual H Bridge DC Stepper For Arduino - - Amazon.com

Qunqi 2Packs L298N Motor Drive Controller Board Module Dual H Bridge DC Stepper For Arduino - - Amazon.com
www.amazon.com

I don't think the breakout board with heatsink and all the extra weight is needed can get the chips themselves too though

Amazon.com: PIXNOR 10pcs L293D DIP 16-pin IC Stepper Motor Drivers Controllers (Black) : Industrial & Scientific

Amazon.com: PIXNOR 10pcs L293D DIP 16-pin IC Stepper Motor Drivers Controllers (Black) : Industrial & Scientific
www.amazon.com

learn.adafruit.com

Arduino Lesson 15. DC Motor Reversing

This is Lesson 15 in the Learn Arduino Adafruit series. In this lesson, you will learn how to control both the direction and speed of a small DC motor using an Arduino and the L293 motor driver chip.
learn.adafruit.com learn.adafruit.com

The voltage regulator on Arduino can step down voltage from 2S so think I just fed power into the VIN line don't go to 5V line unless feeding regulated 5V already (this bypasses the Arduino regulator before passing power to the Atmel chip itself which expects 5V for 16MHz operation).

---

Some additional thoughts... Can run off of 1S if using a Arduino Pro Mini 3.3V version at 8MHz it will work reliably until the battery is down to around 3.3V maybe less but complicates some things in terms of programming and working with other 5V things can cause problems. You can always use a "boost converter" to up the voltage or a "buck converter" (or less efficient linear regulator or voltage divider) to drop the voltage so you can always adjust the voltage (can also get a "buck/boost in one" that can up or down the voltage to some target from some source but always some losses)
Click to expand...


thank you. im still having the same issue with these motors. now they make weird sounds. sounds like static. they also spike every now and then. it almost feels like they jump to a higher speed randomly and then dip back down to their intended speed. no change in writeup. im confused as all hell. all parts seem to fit but its not working.
 
There's going to be some minimum value below which the motors just won't be turning over smoothly but above that minimum you should be able to throttle up or down and have roughly accurate speed changes accordingly, show some pics of your setup (good to see the battery and motor connections to the h-bridge board) and code you're using for now. I can dig up the code I used for the little bot too and compare with the setup on there since it's still wired up. With power going up and down it could be something with the connections so make sure everything has good contact and is well attached (give wires a little tug after hooking them up, don't pull hard but just make sure they aren't loose).
 
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