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Motor drivers - will these work?


#1

So… yesterday my ardumoto shield went up in smoke.
I had measured the amps of the two cordless drill motors I am planning to use on my new robot. The meter said 1 amp per motor, but I believe that was not correct.

Anyway, my ardumoto went up in smoke. Now I am looking for more powerful drivers.

I came up with these 2 drivers:

http://www.watterott.com/en/Dual-Motor-Driver-9A-VNH3SP30-MD03A

http://www.watterott.com/en/Motor-Driver-9A-VNH3SP309

The first one is a dual motor controller and the second one is a single motor controller.

Both motor specs say that their voltage range is 5.5VDC-36VDC. Is this logic voltage or motor voltage?

The pololu website sais: 5.5VDC-36V* "*Manufacturer specification. In our experience, shoot-through currents make PWM operation impractical above 16 V. "

However, the batteries will have a voltage of ~ 14-19V DC (18v batteries, ~18,6V when charged)

Second, it can be controlled by PWM. Would it be easy to modify the motor shield driver to make this work?

Thank you! ;D


#2

I’m using vnh3sp30 for one of my robots. PCB is custom, but chip is the same.
Logic sits on 5v (3.3 could be too low. Datasheet says min voltage for high signal is 3.25) and main motor voltage on 4s1p Lipo (~16,8v when charged). Motors take about 4-6A of power. Driver stays cool. Probably the best motor drivers for hoby robotics.


#3

But will it work with 18V (~19V MAX) cordless drill batteries?
The voltage my main concern. Amperage is fine. 9 Amps should be enough, even under load.


#4

It will. Datasheet says 40V is absolutely maximum and 36V is safe max. So 18V is a half what it capable of.
Usualy main concern in motor driving circuits is amperage. Don’t see any reason why this couldn’t work with your setup.

Don’t see soldered capacitors in the midle of scheme. If you would need to solder them choose somthing from 60-90V range.


#5

Yes, I would like to add those capacitors. Which value would be best?

ok, but have you seen the warning with the boards?
I have added it as attachment. That is what is worrying me.


#6

In First robotics competitions we are provided with these Motor controllers.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=296-25445-ND
They have proven to be very durable, however we use 12 volt gell cell batteries for power. They are rated for 24 volts. The largest motors we use have 120 amp FLR draw at 12 volts. They have thermal and current protection. The hobby PWM servo control is good enough for allot of application. The CAN interface allows them to become true motion control devices. If there are any First Robotics teams in your area, they may allow you to add on to their order. Teams get them for 85$. They are NOT REVERSE POLARITY PROTECTED!! Our students have managed to kill them this way. They are locked anti-phase driven and this helps with the switching transients that hurt other low or high side switchers. I highly recommend them for higher power motors. If you look at the prices of other high power controllers and the capabilities you’ll find that these are a bargain. I have never tried to drive them with a 3.3 volt device. They work fine with most 5 volt micro’s.


#7

The bigger the better. It depends on how much place is in those boards.

I guess I’m lucky, but I hadn’t had any problems with voltage of 16,8V. Don’t have working setup now, so can’t try it for you :frowning:

If you like soldering, I can give you schematics of my dicrete h-bridge with optical isolation.


#8

well, 16,8 is not such a big difference comparing to 16V max. ~18,6 (unfortunately) is.

I have spoken with the German distributor (Watterott) of tinyclr. He said this:

[quote]Hello,

18V wil work, but I think in high current oparation it is not a good solution.
When you use it with max. 5A it should no problem.

Mit freundlichen Gruessen / Best Regards
Stephan Watterott[/quote]

Which is a problem. Because my dad and I tested the amps again yesterday. The motors indeed drew around 1 amp of power, but under load it’s 8,5 Amps.

So I am starting to believe that this motor controller might not work.

I have checked the watterott site again (since the dutch distributor is too pricey, it’s cheaper getting it from Germany :smiley: ) and I have found these:

14 amps: (16V max…)
http://www.watterott.com/en/Motor-Driver-14A-VNH2SP30-MD01B

15 amps: (50V max but specifications say 9amps instead of 15?)
http://www.watterott.com/en/Motor-Driver-15A-FDS5672-36v15

Specs:

25 amps: (30V max)
http://www.watterott.com/en/Motor-Driver-25A-IRF8734-18v25

Specs:

I need two of these boards then… :frowning:


#9

See if you can find theses. They are nice motor controllers.

http://www.trossenrobotics.com/store/p/6528-Sabertooth-dual-12A-motor-driver.aspx


#10

The problem with running this controller at higher voltages is that the switching transients are clamped by the intrinsic diode of the FETs. High frequency PWM, high voltage and high currents will stress that part of the FET. You may be able to use this board if you added bidirectional TVSs on both motor outputs to ground and across the main supply capacitor . Choose one with a clamping value around 30 volts. They do come in axial form which may help in adding them to the board. The other problem is that the PWM input high voltage graph shows that the chip really should be driven by a 5 volt device. The other high current Pololu drivers may be better choices. If you choose a serial controlled board, the 3.3 volts of the arm chips is not a factor.


#11

[quote]See if you can find theses. They are nice motor controllers.

http://www.trossenrobotics.com/store/p/6528-Sabertooth-dual-12A-motor-driver.aspx[/quote]

I do like this controller, but I cannot get those from a EU supplier.

Are you referring to bstag’s motor controller or the one I mentioned?

What do you guys think of the 25A version I mentioned before?

http://www.watterott.com/en/Motor-Driver-25A-IRF8734-18v25

specs:


#12

I was referring to the ST Micro VNH3SP30 chip. The Trossen Robotics Board appears to be Locked anti-phase controlled. I believe this because it lists Synchronous regenerative drive,Ultra-sonic switching frequency. This will handle switching transients better with the down side of more heat generation. You don’t have to drive the motor with 18 volts. you could use a lower voltage battery pack with the loss of max power. The key to can motors is the mechanical reduction. The motors rpm needs to be kept up so the internal fan can provide cooling. Choose a drive reduction that keeps the motor near the peak efficiency point on the curve at full power. The Texas Instruments controller is a real value but, I think the availability in Europe and shipping costs are a problem. The Pololu board listed has 30 volt FETs. Again they would be better at 40 volt. May get away with locked anti-phase control. Some Pololu boards do have 40 volt fets.


#13

So would you advise the pololu board for my situation or not? I am kind of lost what to pick and what not… :-[

I do have other batteries. 2 LIPO batteries. But I would like to use the accu which came with the cordless drill. It can also provide some counter weight, to prevent flipping (because both cordless drill motors will be in front of the robot)

Thank you all for all your help so far.


#14

On the web site you listed there are Pololu driver boards that are listed for 5.5 to 40 volts. They have the 40 volt DS FETS. They would be better.


#15

That would be this one?

http://www.watterott.com/en/Motor-Driver-20A-IRF7842PBF-24v20


#16

The sabretooth I mentioned works fine for driving drill motors and Mattel motors. While it can produce heat that would be what the heat sink’s are for.


#17

Well…including shipping costs it costs me ~$127. In euros this is ~100 euros.
Which is not so bad, but:

I get twice this one for ~72 euros (incl. shipping)
http://www.watterott.com/en/Motor-Driver-20A-IRF7842PBF-24v20

Or twice this one for ~100 euros (incl. shipping)
http://www.watterott.com/en/Motor-Driver-25A-IRF8734-18v25

Which can provide more amps. I would like to be safe if it comes to amperage. I would not like to see a baked board again :smiley:

What kills me are the shipping costs :frowning:


#18

Speaking of motor controllers. I purchased the EasyStepperDriver from sparkfun other day to try out. I was wondering what pros/cons of stepper over normal motor on robot. My thinking was I could control Degrees of rotation with a stepper (e.g. nxt). The other approach, I guess, would be a feedback sensor in each wheel - which seems like a more complicated solution. Any ideas on this. Any downside to using stepper for wheels like this? tia


#19

William. Stepper motors are good for what you say. They are like dc motors with encoders. Except you can tell a stepper to turn but you don’t know if it did. Where if you tell a dc motor with encoders to turn and it doesn’t you know it.

Foekie I will ask ask the guys around here if they have used those controllers on a drill motor and how they performed.

Asked got answer already. they used a 18v25 version you mention. On a Segway style project. They found the drill motor amperage peaks higher then the non load readings you get.


#20

I think you need to fully check your motors locked rotor amps. That will help allot. You may be able to get the manufactures data sheet to. That will tell you what your worst case abuse of the motor controller will be. The Trosen controller is a good one but you will get killed on shipping. The Pololu controllers will also work. Pick one with 40 volt FETs. The pololu boards will most likely need some kind of thermal management. They leave it to you to figure out the heat sinking. You could also get one of the boards that can measure current and limit the current in code. You could also put a thermistor on the heat sink and do thermal management in code. The 24v20 looks OK. What is your robot going to do? Robots that do autonomous navigation rarely stress the drive train. Competitive robotic competitions with human drivers really stress the motors and controllers. Also be aware that these controllers are not reverse polarity protected. Hook the leads wrong and the magic smoke will be released. Also, If they really fry your FEZ may be also fried. Another poster mentioned optically isolated. A good thing with motor drivers. Digi-key does ship reasonably to Europe if in the future you want to step up to the TI Stelaris motor controller.