Monday, April 11, 2011

[Youtube] Nunchuk + DC Motor Controller demo

The motor controller now works in one direction. See the Youtube video below for a demonstration:

Saturday, April 9, 2011

Forward direction + brake works

The controller works in the forward direction. Speed control and braking works. Pictures and videos will be uploaded soon.

So far I have been following's h-bridge design. However, it requires AND gates. After attempting it in the lab today, I'm now abandoning that idea. It takes too many wires to do it, and the logic can be programmed in the Arduino. With this new philosophy, all of the logic will be handled by the Arduino. The number of output lines from the Arduino to the H-bridge will increase from 3 to 4, but the overall amount of wiring will decrease, and so will the overall footprint.

H-Bridge Controller Prototype

I've built a prototype program for controlling the H-Bridge. It should be able to do forward and reverse with braking and direction switching. There is no safety feature for direction switching, so you must manually slow down before you do it. Tomorrow everything will be hooked up. Something is guaranteed to blow up, but hopefully it's not the Arduino or the Nunchuk.

Friday, April 8, 2011

Youtube video and pictures

I finally have some pictures and stuff to post.

Here's a Youtube video of the Nunchuk, Arduino, and LED display working together:

Wednesday, April 6, 2011

7-Segment Serial Display from Sparkfun

The 7-Segment Serial Display from Sparkfun came in the mail today. Arunet has a good guide for this product: Here's some notes.

- After using it for about 4 minutes the brightness went down. Do this to get it back to maximum brightness:


- Changing the baud rate was a little tricky. Sending it "127" and then "4" doesn't work, nor does "1276." I did:


And finally it changed the baud rate to 19200.

- If it starts showing dots when you don't want them, do this:


and the dots should go away.

Monday, April 4, 2011

LED Display Ordered, Hardware assembled

Checked out a DC motor today from school, and got the H-bridge from my ex-lab partner. Also ordered the LED display from the previous post.

Saturday, April 2, 2011

LED Display and Over-current Protection Ideas

I am considering buying an LED display for this project. It would be used to display the value of the PWM signal sent to the H-bridge, as a percentage (i.e. the duty cycle). This would be good because I wouldn't have to use the Serial port on my computer to monitor this value. This 7-segment, 4-character LED display from Sparkfun looks good:

There's a good tutorial here: on how to use it. This particular display can use both NewSoftSerial and SPI, but apparently there is a bug in the SPI implementation:

Over-current protection is still a problem. I need some sort of feedback. Implementing it will cost money. It's not that expensive (Sparkfun sells one:, but I'm running out of cash to spend. I'll probably have to settle for some auto-delay function when you switch directions, that will automatically slow the motor down before you apply counter-current.

Friday, April 1, 2011

More Nunchuk Action

Test code up and running. Speed control, braking, and direction switching coded. Motor is not yet hooked up. Direction switching will have to be idiot proof.

You should to decelerate to zero (or close to it) before you switch, or else the motor literally jumps. it's hard to guarantee this without feedback from the motor. For now a delay/deceleration time of 3 seconds has been coded in. The applied voltage is slowly brought down to zero, and then the motor freewheels during this time. This time should be set to the worse-case scenario (initiating a direction switch while going full speed), which will be determined when the motor is hooked up.

The Nunchuk is working fine. I did have a problem where it wasn't communicating with the Arduino for a while. I discovered that the Nunchuk adapter must be soldered to wires or a header for the connection to be reliable. For now I just use my fingers to hold the header to the adapter, but eventually it needs to be soldered together. I might have to order another adapter in case I don't solder it right.