PIC-AXE Controller

Posted: 2011/09/10 in Uncategorized

I opted to switch my BS-2SX based controller for a PIC-AXE based one.  I had several reasons to do so.  The hardware is much more compact, the processor is much less expensive, it offers a larger set of pre-built routines and the supplier provides a product that has a PIC-AXE 18 + XBee on the same small board.

 My biggest problem with the BS-2SX was how finicky the serial interface was to program.  My BeagleBoard needs to communicate with the controller and it took me forever to find documentation and good detailed examples to get the timing just right to get the data flowing in both directions reliably.

I’m hoping that this will not be the case with the PIC-AXE 18.  Now I’m have to change my RS-232 layer to account for the controller change, and have to translate my BS-2SX routines to PIC-AXE basic.  This should be interesting.


Redesigned Chassis

Posted: 2011/09/10 in Hardware

As I mentioned in my last post, I redesigned the rover mechanics to decouple the electronics from the chassis.  Here are a couple of pictures of the chassis and the electronics’ carrier.

I re-positioned the electronics to make better use of the space and provide better access to the electronics to test components.

The new power supply is based on 2 Parallax Lipo based units that contain all the necessary electronics to safely recharge the batteries and at the same time prevent the batteries from discharging too low.

In addition to these units I used a high-efficiency regulation module from SparkFun and stacked a voltage sensor to monitor the pre-regulated voltage and a temperature sensor to ensure everything stays relatively cool.

I had to perform some simple changes to the software running on the BeagleBoard to change the voltage thresholds to match the new power units.  Everything tested good.

Wow, it’s already the end of the summer, time goes by quick. The days are getting shorter now, it’s time to get back to indoor activities.

I had a couple of weeks of vacation and the weather was rather crummy, so I was able to visit the basement machine shop.  I redesigned (again) the base of my rover. Now the electronics can be easily removed from the body of the rover.

Rover MKIV

B.T.W. I replaced the power supply system with some very nice units from Parallax.  These have built-in battery chargers and monitors.  I also replaced the Basic Stamp controller with a PIC-AXE controller with a series 2 X-Bee module.  I’ll have to re-design part of my S/W but the PIC-AXE should prove more versatile and uses much less physical space.

I’ll provide details in future posts.

I managed to put some time on the controller this week.  I fabricated the plate that holds the accessory connectors.

Here’s the result.

The RJ45 connectors are used to connect to input circuits.  The top 4 ones are to be connected to the 4 axis home switches and the bottom connector is for the emergency switch/limit switch circuit

The amphenol 4 pins connectors are to be connected to relays controlling accessories.

I got the cables from the stepper motors to the controller done.

Here’s a picture of the stepper motor cables connected to the controller.  The cable will need to be longer once installed on the mill, but this is good for testing the system without the mill.

The next step will be to install the accessory connectors (for limit switches, etc…).  I plan to use RJ45 receptacles and pre-made 10BT ethernet cables for those as they carry very little power.

Then I’ll be able to create a cover for the enclosure.

CNC Controller

Posted: 2011/01/22 in CNC conversion

Well today I managed to spend some more time on the enclosure.  I finished making the custom brackets to mount the Gecko CNC controller in the same enclosure as the power supply.  By doing this, the power feeds are less than 6 inches long and eliminates virtually any loss.

I really dislike having stray wires in an enclosure, specially if they carry high current.  So I encased the various power and control wires to protect them.

Well I’m putting some old AT power supply enclosures to good use.  The power supply for the controller is too large to fit in a single enclosure so I took 2 enclosures, did some modifications, fitted some aluminium rails and things fit rather well into the new enclosure.

As you can see I kept both cooling fans, I just changed the direction of one of them to force air circulation over the power supply.