Monday, June 30, 2014

Allegro 2917 Dual stepper shield

One day a came across a great find, a HeNe laser scanner/projector , a 2000W stroboscope with a color wheel, a Gobo/disco scanner,  a buch of HP printers and other various electronics.

I recently had aquired an Arduino UNO from cooking hacks and with the abundance of obtained stepper motors I wanted a small platform to easily control them. While disassembling the HP printers I noticed that they had a small IC to controll the motor. After a quick search of the part number I found out that they were dual H-bridge IC (45V 1.5A) with current controllable current limiting.
The project began! I found a template for the Arduino headers and got to work in Eagle. This was my first time using Eagle, and provably my third home made board, please forgive the horrible layout!

Not to mention that I placed many vias under the IC's... I had to make sure that they all made good contact and that they were flush with the board before placing the IC on top.
Solder, check, repeat. The same for the other IC.

 Things were going well, wrote some code in the Arduino IDE. Enable OK, phase OK, PWM... not ok. Motors would spin well with low supply voltages but would stutter with a higher supply voltage.
Re-check everything and find out that the stuttering only happened on one of each phase of each IC so I decided to sapw the chips over. The same behaviour on each phase of each IC. So basically the chips were damaged from the begining :(
For some reason I choose to take the board apart so I could stick it the oven pull the IC's off (pretty hard to do with a 25W soldering iron when 22 pins are part of the heatsink/ground plane).
Turns out the cheap boards I purchased were not FR4 material... well thats the end of that project!

For those that want the files they can find them here in Eagle's format.

1 comment:

Anonymous said...

Could you also provide the source code for the arduino?