Motor Discussion

[AndriyPt]

Let's decide on motors. Requirement 6mm diameter of the shaft. What about this https://www.robotshop.com/en/12v-12rpm-2701-gear-motor-w---encoder.html ?

[LyubomyrD]

I am not sure that they will be able to drive the Leobot.

What about these? https://www.tme.eu/pl/details/df-fit0185/mikrosilniki-i-akcesoria/dfrobot/fit0185/

[vyosypenko]

http://arduino-kit.com.ua/motor-12v-dc-motor-83rpm-w-encoder.html http://smdua.in.ua/katalog/robototehnika-113324/mikrodvigateli-i-aksessuary-113329/fit0185_id223666 https://www.digikey.com/product-detail/en/dfrobot/FIT0185/1738-1105-ND/6588527

http://smdua.in.ua/dfrobot?page=6

[LyubomyrD]

@AndriyPt @nemo8 Seems like we have come to a final decision with the motor :) The only question now where they are in stock.

[vyosypenko]

There are 3 items on http://smdua.in.ua/katalog/robototehnika-113324/mikrodvigateli-i-aksessuary-113329/fit0185_id223666

[LyubomyrD]

@nemo8 have a look at the TME site. They also have only three of them. Either it is a neat coincidence, or SMDUA is just a TME reseller. (copy of the link from the prev.msg.) https://www.tme.eu/pl/details/df-fit0185/mikrosilniki-i-akcesoria/dfrobot/fit0185/

Delivery from Digikey will take us +/- two weeks.

[vyosypenko]

This motor can be fine as well: https://www.robotshop.com/en/12v-dc-motor-251rpm-encoder.html

Max current consumption for the motor 7A, we have 2 parts, so max = 14A. We need to have a power source with can supply at list 14A at the motor start. For power, we can use an ATX part from PC, or a battery.

[LyubomyrD]

I guess we need at least 3Nm (or 400 ozf-in) motor torque. The last motor is questionable. It may or may not work for us.

[LyubomyrD]

@nemo8 I believe that we have four motors, haven't we, @AndriyPt ?

[vyosypenko]

@LyubomyrD, where can I find the picture of the robot platform (where motors are located)?

[LyubomyrD]

@nemo8 not exactly what you are looking for, but some specification is given here https://github.com/ros-ukraine/leobot/issues/110

[vyosypenko]

@LyubomyrD , thanks. According to the spec "Number of wheels:4".

[LyubomyrD]

So we need Max 28A, however, I guess that a battery (or two of them) like the following may be OK, since 28A may be never needed in the real life https://rozetka.com.ua/ua/csb_10030112/p12603068/

The driveshields (4pcs) that I suggest: https://bit.ly/2Hyqyad

[vyosypenko]

28A it's a max current at the starting, working current should be about 14A or less. So 9Ah/14A = 0.64 hour (continuous running)

[vyosypenko]

@LyubomyrD, your driver looks fine, but optocoupler should be added. (this driver has not optocoupler in the board).

[LyubomyrD]

@nemo8

28A it's a max current at the starting, working current should be about 14A or less. So 9Ah/14A = 0.64 hour (continuous running)

The no load current is 350mA. The final current depends on the load. 30 min may be not enough, this why I proposed two batteries connected in parallel - to increase Ah.

your driver looks fine, but optocoupler should be added. (this driver has not optocoupler in the board).

Why do we need an optocoupler in this case?

[vyosypenko]

@LyubomyrD ,

Why do we need an optocoupler in this case?

yes:

1. if the driver is damaged it will damage our stm32 board and laptop.
2. Motors are inductive load, they make a lot of noise on signals lines

[LyubomyrD]

Let us add the optocouplers, however this may lead to PCB designing.

The pololu site states that the board has

built-in protection against reverse-voltage, over-voltage, under-voltage, over-temperature, and over-current

Although the pololu board has two more pins that are output pins in the fault modes.

[SystemDiagnosticss]

@LyubomyrD @nemo8 Its construction: I try lift it. His weight no less 12 kg. If added also laptop, battery and other ... His weight well be almost 18-20kg. I think 3Nm motors its bad idea. Friction force for mecanum wheels is much larger than ordinary wheels. I think we need more powerfull motors.

[LyubomyrD]

@SystemDiagnosticss the datasheet states that each DFROBOT FIT0185 provides 4.4Nm torque. What are Your suggestions on the model of the motor?

[SystemDiagnosticss]

@LyubomyrD I think for this guy we need 15-20Nm ...

[LyubomyrD]

@SystemDiagnosticss You mean 15-20 Nm for each motor?

[SystemDiagnosticss]

@LyubomyrD yes

[SystemDiagnosticss]

@LyubomyrD Sorry I'm confused Nm and kg.cm ... 45kg.cm in DFROBOT FIT0185 well be good :)

[MaxZhaloba]

Just to mention, parallel connection of batteries is not a good idea. It will cause self-discharge of batteries. The best option is just to take a single battery with higher power for all motors and (as an option) use a separate battery for electronic components for better stability. Other option with 2 batteries is to connect them in pairs to 2 motors, but this might lead to disbalance in movement, especially on mecanum wheels.

[vyosypenko]

For power supply and battery charger we can use something like this: https://www.ebay.com/itm/100-220V-12V-10A-Sw-Power-Supply-W-Battery-backup-charging-CCTV-Security/331860436497?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D50544%26meid%3D4e0706fb1e334734b4aad984676eeae4%26pid%3D100005%26rk%3D1%26rkt%3D12%26sd%3D332334555149%26itm%3D331860436497&_trksid=p2047675.c100005.m1851

https://www.sea.com.ua/istochniki-pitaniya/s-funkciej-ups/

https://ru.aliexpress.com/item/12V-13-8V-Dual-Output-Uninterruptible-Power-Supply-400W-with-Battery-Charger-UPS-Function/32621605353.html?spm=a2g0v.search0104.3.44.4ce229c87q7YiO&ws_ab_test=searchweb0_0,searchweb201602_3_10152_5722916_10065_10709_10151_10344_10068_5722816_10342_10343_10340_10341_5711416_10697_10696_5722616_10084_10083_10618_10710_10307_5722716_5711216_10059_308_100031_10103_441_10624_5722516_10623_10622_10621_5711516_10620_5711316_10125-normal#cfs,searchweb201603_25,ppcSwitch_5&algo_expid=48197a5d-e76b-4d79-9667-b14c78639c06-6&algo_pvid=48197a5d-e76b-4d79-9667-b14c78639c06&priceBeautifyAB=0

[LyubomyrD]

Yes, these components are great. I used them, but they require a wire to the wall socket. I was hoping to use battery power for the robot.

[vyosypenko]

@LyubomyrD, a battery should be with the battery charger. Power supplies from my link support charging feature. As for me, it is not convenient to take the battery off from the robot for charging and then put it back.

[MaxZhaloba]

I’ve seen these power supply modules on our radio market in this shop https://www.rcscomponents.kiev.ua/ They specify the availability and price on their site, so we can check for the model we need.

[LyubomyrD]

@nemo8 I do agree with what You are saying. However, this is just an iteration and not a final product. So we have to decide whether to have a wire to the wall or several batteries that we will remove sequentially for charging them.

@MaxZhaloba Can You make any suggestions on the components that you recommend purchasing from Kosmodrom?

[MaxZhaloba]

@LyubomyrD, Haha 😄 I haven't heard this name. Not sure if you mean the radio market or the RCS shop, but anyways, I'm not an expert on motors. Neither I used any powerful batteries, so at the very most, we can calculate the necessary power of battery and choose one of the suitable items.

The only suggestion I have so far is that we need either to use a separate battery to supply power for electronic components or have a decent power stabilizer to prevent the power surge on electronics.

Actually, when I needed a powerful DC source for my homemade audio amplifier, I just bought a secondhand IT power supply block (with hardware switch) from an old PC over there on radio market. I remember it was quite cheap and serves me well by now. I've just had a look on its labels and they specify 150W total power output (which in theory corresponds to 12,5A max current) and different output options: 12V/16A, 12V/6A, 12V/5A, so it's hard to tell the actual power output, but it's probably somewhere within the limits of 5-10 amps.

[vyosypenko]

@MaxZhaloba, I will create block diagram for electrical part of our robot. It will make discussion simpler. I have experience in developing devices.

[AndriyPt]

We do not have 4 motors. I have only two possible options of motors with encoders. But unfortunately it is not possible to order three more for the one which I like :) So the question is still open and it will be nice if we make decision soon.

[vyosypenko]

@LyubomyrD , I've found this driver: https://diylab.com.ua/p503528464-drajver-monster-moto.html It has two IC which you had suggested. This solution will save place on the robot. (two boards instead four)

[LyubomyrD]

@nemo8 I doubt that we will get any significant gain in the area. The dimensions of the corresponding modules are given here https://bit.ly/2Kpn5Zo (55 x 28 x 12 (LxWxH) mm) https://bit.ly/2HEPX2f (60 x 54 x 12 (LxWxH) mm)

Besides, there will be more mess with wires, in my opinion.

However, we can try to follow You advise. I actually never used the Dual Moto Shield - it will be a new experience.

[AndriyPt]

@LyubomyrD and @nemo8 is this the same board https://www.aliexpress.com/item/1pcs-30A-Mini-VNH2SP30-Stepper-Motor-Driver-Monster-Moto-Shield-module-For-Arduino/32730453816.html Also I would prefer to have single board per motor to distribute heat better and also in case of damage you'll need to replace one PCB completely. Regarding motor it is this one https://www2.mouser.com/ProductDetail/DFRobot/FIT0185?qs=%2fha2pyFadugwqBDw%252bTmTALHo0nQTlFYnDuZ6aFXARpY=

[AndriyPt]

Heatsink for boards https://www.aliexpress.com/item/5pcs-Ultra-thin-Groove-Pure-Copper-Memory-MOS-Radiator-Notebook-Cooling-Copper-Heatsink-17-17-2/32810852271.html

[LyubomyrD]

@AndriyPt the motor and drive shield are same as we have spoken about

[LyubomyrD]

@AndriyPt the size of the heatsink is OK.

[vyosypenko]

PMW frequency calculation for DC motor: https://www.precisionmicrodrives.com/application-notes/ab-022-pwm-frequency-for-linear-motion-control

FIT0105 documentation: https://www.dfrobot.com/wiki/index.php/12V_DC_Motor_122_rpm_w/Encoder_SKU:_FIT0403 https://www.dfrobot.com/product-633.html https://www.amazon.com/12V-DC-Geared-Motor-Encoder/dp/B073QXQW5Y http://www.cqrobot.wiki/index.php/Metal_DC_Geared_Motor_w/Encoder,_CQRDJ-GL

[vyosypenko]

PMW signals for motor ( 51%, 25%, 12%, 6%):