4 Motor Control – Arduino code to move four motors at the same speed

A member at Techshop had four motors and needed to use them to lift a heavy plate. He needed each motor to lift one corner; working in synch or else one corner of the plate would end up way to high.

The guy, a very talented woodworker & machinist, wanted a little help on the code. I wrote a simple Arduino program that implements a closed-loop position control algorithm. Because ultimately the mechanism was to be controlled with an Iphone / Bluetooth interface, I wrote it sort of like a “state machine”; implementing modes like “OFF”, “STOPPED”, “FORWARD”, “REVERSE”.

After a little debugging it actually works really good!

The software uses feedback from the encoders to keep each motor within a calibratable maximum angular displacement
The software uses feedback from the encoders to keep each motor within a calibratable maximum angular displacement

Continue reading 4 Motor Control – Arduino code to move four motors at the same speed

Detroit Metro Area Creative / Maker / Hacker Spaces

Detroit Metro Area is home to a huge pool of engineering & creative talent. Its probably got among the highest number of “makers of things” in all of the US. It also has great technical & art schools, and low rents.

There are a lot of people doing a lot of cool stuff.

I’ve visited the workspaces of some of these people, and belong to a couple myself.

All Hands Active – Ann Arbor, MI
District VII Detroit – Detroit, MI
I3 Detroit – Hazel Park, MI
Omni Corp Detroit – Detroit, MI
Techshop Detroit – Allen Park, MI


Laser Etched Tile Mural – Robocop vs Little shop of Horrors – Halloween 2012

I made a mural out of ceramic tiles using a laser cutter to etch in a design. The design is the abandoned & iconic Detroit Train station, with a little bit of Robocop & Seymour/Little Shop of Horrors thrown in. The idea was for it to be used as part of the Halloween display for Ragstock, a local clothing store. I used the tools at the hacker / maker space I go to, Techshop.

I etched each tile with the laser, and arranged them to form the total image. The laser only removes the glaze, it’s still white. To give it color / contrast, I spray painted each tile & then quickly wiped it off using a paper towel (actually… many paper towels). The paint only sticks to the parts of the tile that were etched by the laser.

UPDATE: If you’d like something like this for yourself, I’m now offering complete design & fabrication services

The laser settings are shown in a screen capture in the photo’s below, so is a shopping list in the form of a picture of my shopping cart. The total cost was about $120; a lot of which is the wood. The tiles themselves were quite cheap, I think 13 cents a piece from Home Depot.

The overall mural turned out pretty darn good !

Wifi with Arduino Duemilanova and WiFly Chip – cheap and easy!

Ever wanted to connect your electronics & Arduino to the web, via your home WiFi no less? Turns out it’s super easy with the WiFly chip by Roving Networks. I connected my Arduino Duemilanova to a network in a couple hours. It blows my mind how cool this is… connecting a 10$ micro controller to a wireless network?? That is really really sweet! I wanted this chip first for this home-automation project I’m working on, I didn’t do a lot of research ahead of time, but I was very pleasantly surprised with how easy it was to get it to work thanks to the great library & tutorials provided by the Arduino community.

Starting with this tutorial, I found a number of things that were out of date, and an ommision that is potentially DAMAGING to your chip. You need a voltage divider to convert the 5 volt pin’s of the Arduino to the 3.3V expected by the WiFly’s serial input. 

Advice :
1) Do it, it’s totally cool :-)
2) Read my updates to the tutorial below
2) Follow the tutorial, keeping the changes in mind

The build list is super short:
10K Ohm Resistor (2x), 20K Ohm Resistor (2x), 100 Ohm Resistor (3x), Arduino Duemilanova (1x, or similar), WiFly Chip (1x, from Sparkfun or similar, I used the RN-XV), generic LED’s (3x).

This already short build list could be further shortened; the status indicator circuit (100 Ohm Resisters & LED’s) isn’t really necessarily… as long as everything works the first time 😉 Also, the resistors used in the voltage divider (here 20K & 10K) could be altered so long as the ratio is between ~1.7:1 & ~2:1, and the values are in the 10’s of K Ohm’s.

Download my project code and wiring schematic here:
WiFly Arduino Project Example & Schematic (.zip)
I include a super easy Arduino project example, an updated version of the one given in the tutorial above (updated as of July 13 2012).

WiFly Arduino Wiring Schematic (.PDF)

Arduino WiFly, Wireless Arduino, How to, Project Page
How to connect your arduino to the internet using a WiFly chip


I just got this to work with my Arduino Duemilanove & RN-XV using Arduino 1.0 IDE; however, it took some changes from the tutorial:

Updates to the tutorial, a couple notes:
1) In initSettings():
use: wifi.SendCommandSimple….
instead of: WyFly.SendCommand….

Make sure you’re editing your “Credentials.h” file in your example folder for the ssid & passphrase

“Time” the library, is no longer posted on the main Arduino library page, however it is still available here: http://www.arduino.cc/playground/uploads/Code/Time.zip

For pin’s 3 & 4 of my Arduino Duemilanove & RovingNetworks RN-XV I put a 10k Resister in series, then connected a 20k resister in parallel with the Tx&Rx pins of the WiFly chip & Ground (see schematic above). Before I did this, it would not connect to the network (probably because it was not communicating properly with the Arduino). This is a voltage divider circuit, it is **needed** because the chip’s datasheet clearly says you can only use up to a 3.3 V +- 10%, not the 5 V which pins 3 & 4 of the Arduino output.

After these changes, it’s working great! Wahoo! Thanks for the great tutorial & happy hacking

Wall Art Via CNC ShopBot in MDF

Taco nights have become a pretty fantastic tradition at my place in Ann Arbor. I recently joined TechShop in Detroit and wanted to use their enormous ShopBot CNC router.

The two came together in this ridiculous Taco themed mural!

The skyline is Detroit as seen from Windsor ON, and the Taco pattern was based on a graphic I found online and then redrew to work with the 1/4″ router bit. I used Adobe Illustrator for the design and VCarve Pro 6.0 for the tool paths. I painted the 1/2″ MDF board with two coats of “Squash” yellow matte spray paint. I was very surprised at how even the color turned out, especially given how poorly it looked after the first round of paint. I cut the piece in one pass at 0.12 inches of depth, at a rate of 1.67 inches / second. Here’s a video of the cutting.