Dagu Rover 5 chassis robot demo

Thank you = ) At this point the encoders are excessive -I guess- for me. I won't use them for my current project. Buying that 4 channel would be more convenient however I have've limited time and if a delay happens during shipping it won't be good for me : ) If I get stuck I'll get some help from the driver's schematic : )

I have a Rover 5 with 4 motors/encoders and use the Dagu 4 channel motor controller. I use the current sensing feature of the motor controller. Powered from a 2S Lipo at full PWM the motors draw about 1A /motor when turning left/right (when going forwards/backwards the motors draw less current). Stalled these motors draw over 3A a piece. I have used a cheap L298 board from Ebay on another robot and have taken a good look at the datasheet of the L298 chip. There are some things you need to take in to account. If you are pulling 1A from one channel of an L298 you will have a voltage drop of 1.8 - 3.2V on the output. That also means that a serious amount of heat is wasted in the L298. You need a big heatsink to dissipate that heat. The Dagu 4 channel motor controller uses fets with a very low RDSon, so there is only a tiny voltage drop. So no power is wasted and a heatsink is not necessary. The Dagu controller was especially designed for the Rover 5 and is rated for 4A stall current / channel. Here is a photo of my Rover: http://www.bajdi.com/?attachment_id=623 It's my "development platform" :)

[quote author=Nick Gammon link=topic=82618.msg812149#msg812149 date=1338497566] I got mine here:

http://www.robotgear.com.au/Product.aspx/Details/554

I don't know if they have replacement tracks ... you could ask.

Mine tend to slip off, and I find it impossible to adjust the track height. Maybe I'm not doing it right. [/quote]

Mine did that in the beginning, then I just change them to the other side.

I would like to know if this Motor driver board will work with Arduino Due ? ( 3.3V Due)

I don't know for sure. I don't have a Due, so I suggest you email the makers (or suppliers) of the board.

The designer of most Dagu products posts on the letsmakerobots.com forum. You could ask him there...

Another question:

Any idea what is the type of 4 white JST connectors for motors? Got the board, trying to connect motors.

Not really. The motor and the driver board happened to have matching connectors.

Thank Nick you for the sample sketch!

I’ve manage to put together a small rover based on same motor control board and Leonardo.
Only one difference I have 4WD, so I will modify it in order to handle all 4 wheels, if you don’t mind.

I solve my problem with JST by just wrapping bare wire around prongs, no pretty by will work for now.

Looks good. :)

Hi Nick, This is quite a long lasting thread. Like the rest, I've recently bought a 2-motor Dagu 5 rover and I also have the motor shield you seem to be using. Firstly, I have a bit of a problem. Just to test out the Rover, I hooked up the rover to my Arduino Uno just like you have, also neglecting the encoders and I ran your code. When the rover drives, it favours the right rear motor (making it veer to the right). Any ideas on how to remedy this?

Secondly, my rover needs to navigate an obstacle course and hence needs to know approximately where it is. You mentioned above about using the encoders to determine the no. of revolutions of each wheel. Now, I'm what you would call a 'complete novice' when it comes to Arduino and the like and I was wondering how you would go about using the encoders for this purpose. If you had any instructions for me, or could point me in the direction for some help, I would be greatly appreciative. Cheers!

... it favours the right rear motor ...

I doubt the motors all have identical performance, so it is quite likely it would veer a bit. You could try to determine what factor to increase/decrease that motor by to compensate.

You mentioned above about using the encoders to determine the no. of revolutions of each wheel.

I have a snippet (small example program actually) in the section "Reading the rotary encoders". You could incorporate that to find out whether one wheel is moving faster than the other and perhaps use that as a motor compensation.

However this will be thrown out if the track spins, which it tends to a bit, because if one spins a bit as it comes up to speed the number of counts won't reflect which way it is going.

If you are negotiating an obstacle course a proximity sensors might help keep it going straight. For example, sideways mounted IR emitters/detectors could be used to make sure it is in the middle of the current lane. I haven't tried this, it's just a suggestion.

Compensate by adjusting the PWM value of a particular motor? That's a good idea!

What kind of battery would you recommend to power the motor shield? At the moment, whilst I'm getting my bearings I'm just playing around with 6 regular Alkaline AA batteries but what I've heard is that these may provide an unreliable current/ current drops off quite quickly. I looked at LiPo but they seemed quite expensive at JayCar (~$70 for 12V 3600mAh). Is a regular 9V battery ok for supplying power to the Arduino board?

Thanks for you're help!

I used the 7.4V 3300 mAH battery from JayCar.

Sure you can use AA batteries but don't expect them to last very long.

What do you mean by 9V battery exactly? Not the sort you put in smoke alarms?

Yep, the type you put in smoke alarms. They're no good?

Also, I seem to remember reading somewhere that you can't disconnect the power supply to the Arduino board whilst the power supply to the motor board is still connected. Will this damage my Arduino board?

Those smoke-alarm batteries certainly won't driver the motors. They might power the Arduino for a while.

I don't see any harm in turning the Arduino power off even if the motor board is on.

Yeah, I was just going to use (for now) a 9V smoke alarm battery to power the board and 6 AA batteries for the motor. So I was thinking to engage the Arduino board to cycle through the program I write I'd just slap a swith between the Arduino power supply and the Arduino board. So I would have a flip switch or something similar. Do you think this would suffice?

Yes, that is what I have. Not even a switch, I just plug the battery in.

Thanks Nick, I think that covers all of my concerns for this project (for now!). You've been a massive help! Doubtless I will have more questions arising in the future though. Cheers

Hi Nick, I just wanted to run some things past you and get your opinion. So for the power supply of our rover (the motor shield and the arduino uno board) I'm using a 12 V 1300 mAh Sla battery which is run through a voltage regulator and so the output is a steady 9 V. This is then wired into both the Arduino and into the motor shield.

We are only running the two motor dagu 5 rover and hence we have two channels on the 4 channel motor shield unoccupied. We need to run a third dc motor to raise an lower a bridge but the stall current for the dc motor we have is 6.18 A (this is the motor http://www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi?CAT_ID=fk_260sa). The manual for the shield says that a dc motor with stall current greater than 4.5 A should not be used, else we could damage the shield. My question is can we use this motor with the shield ensuring that we read the current pin for that channel and turning the dc motor off when the current exceeds, say 4 A? Or can we somehow just hook it up through the arduino chip, bypassing the shield? Or do we need to get a motor with a lower stall current?

Thanks for your help.