DFRobotShop Mecanum Rover 2.0 - Arduino Compatible Robot (Basic Kit)

I would start off by saying this is a review for the overall kit and that the controller board is excellent albeit with one issue I've found so far which I can identify as a defect with the one I received or maybe something that got past QA in general. Firstly, the highlights of the kit, the board controller board is exceptional and the expansion board provides more or less everything you need to at least get this up and moving quickly. The wheels are good quality so no issues there. The downsides, firstly the encoder discs shipped with the kit are plastic and the hex shaped hole for two I received was smaller than the shaft so slotting them in caused them to break easily, I quickly switched to cardboard cut outs for the wheels that I could not salvage. The next major issue is with the powering, the supplied resources suggests a 3.7V LiPo battery with at least 1000 mAh so I got one. I didn't see any issues while I was debugging and testing using the serial/usb interface with the LIPO connected and all 4 motors would spin properly. Then when I disconnected the USB the motors would spin for less than 1 second and then it would look like the board just stopped working, I began to worry I shorted something in the board but as soon as I plugged it back into the computer via the USB it was working normally again. That point on it was testing different configurations to figure out what was going wrong, which included powering multiple motors in different combinations to see if one was shorted and maybe just drawing too much power but that didn't result in any issues either. The issue only came up when I tried running all 4 motors at the same time. I thought it was a current draw issue (I didn't do the maths but it shouldn't have been) and maybe I was not supplying enough power to the system so I switched out the LiPo to 4xAA batteries and the battery pack so I removed the L1_SEL jumper while I was debugging and everything seemed to work while connected and not connected via USB. Just to cover all my bases I tried the LiPo again but with L1_SEL jumper not connected and now it seemed to work both connected and disconnected with the USB which was a bit confusing. Turns out that having the L1_SEL jumper connected and running all the motors led to some issues and I cannot figure out why. It's not a big issue since when I'm using it now I just pull out that jumper and the system works without issue but I cannot find this behaviour documented anywhere so I just wanted to make anyone aware of that.

Kit is of reasonable physical quality, except the USB port is only soldered down and quite weak. Major design flaw in the board is that the PWM output for the motors uses up all the timer pins on the arduino. ------------------------------------------------------------------------------------------------------------- Hi Joel, We are certainly sorry to hear that you had an issue with the USB connector, and assuming the product was under warranty, would have replaced the entire board free of charge. With regard to the pinout, we had to choose four pins to dedicate to the onboard dual motor controller. We did our bes tot choose pins which are as little used by other shields as possible. Unfortunately a Mecanum driven robot requires a total of four H-bridges (each needs one digital pin and one PWM pin), meaning a total of eight of the 13 digital pins on the Arduino are used. If you add encoders, those require a further four pins, leaving only the analog and either the Tx or Rx pin. The RobotShop Team