Saturday, October 29, 2016

Micro stepdown Buck converter

Fun project, pretty close to reaching my PCB making capabilities in terms of track size and clearances. Also testing my new built PCB drill which was posted earlier.
The brain of this project is the XL4001 IC which minimizes external components and provide excellent voltage regulation and current protection. Input voltage range is from 4.5V to 40V and output current up to 2A. Switching frequency is around 150khz+-25Khz for regulation. 
The schematic follows the basic application circuit from data sheet, with minor changes to allow an adjustable output voltage.
The current protection is defined by value of RS as follow
On the board shown, used a 0.3ohm resistor to set Iout max at about 500mA.
As seen, the schematic calls for a 4pin header connector while the board shown has only 3 pins. Since the ground for the load must be isolated from common ground of input power (isolated by RS), two pins input and 2 pins output are required. The shown board will need a layout correction.
Anyways, tested with 20Vdc input,  output adjustable from 3.3v to 18.5V. However, the max output voltage should not exceed input-3V(input-1.5v as per datasheet).
I also used this same IC for a constant current LED driver with very good results, to be posted in the future.

Sunday, October 16, 2016

Step Motor driver Allegro A3977

Running some tests on the A3977 step driver IC, schematic below. Have not been able to make it work yet, if ideas out there please chime in with comments.
Note that some resistors are 00(zero)ohms, used as jumpers since I didn't want to make via on this board (yet developing the drill press).

PCB drill press

Building a PCB drill out of a 12mm linear rail and other material sitting around. Thought of making the big jump to a complete CNC machine, but keeping budget lower for now.
The rails are 12mm diameter with two pillow blocks, the must have parts to achieve some level of precision, specially when making PCB's down to 10mils sizes.
The motor used for the drill is an old DC motor from a cordless drill that operates with around 2.A and the motor driving the slide was purchased from eBay. All is working out of a 12V regulated power supply.
The control circuit is as simple as it can gets, just a position switch to detect and stop the slide at idle position, a foot switch to trigger the drill and few components to provide lower speed on the drill motor while in idle state.
The slide is weight balance by both spring and counter weight system and target selection done with a camera and two mirrors made of a HD current in half.
Below some pics and video.