Saturday, 31 August 2013

PCB Bench Tested

This morning was spent reassembling the PCBs back into the base - I wanted to power up again and verify everything is still working :


I've backed the voltage down to 12v - the prototype was designed around 12v source - not 15v as is the case with production models.

All the motors are still spinning, which is a result !   I might have buggered my computer interface, but at least I have manual control.  Yep, the pessimistic approach is always the best, and maybe I'll just be pleasantly surprised later...

The only part of the circuit I haven't traced is the hand controller itself - basically, it routes clock signals generated by the 555 timer (IC6) to the motor drive logic, and sets direction to be clockwise or counter-clockwise into IC1 and then onto the drive circuitry....


The toggle switch (top-center) switches between computer, or manual control.  The LED barely illuminates on my controller - suspect the current limiting resistor is not quite right, there is no mention of it in the original circuit diagrams.


The motor control switches are all double poll, double throw.... I labelled mine up before reading the manual and assigned numbers to each stepper when I started stripping things down... I will renumber these to match the suggested channel numbers later.

As you can see, the controller is quite busy, but I can assure you it's rather simplistic.  If your missing a controller (and you have a prototype model), it would be quite possible to make one of these boxes.   If there is enough interest later, I'll draft up a circuit diagram and bill of materials.

Last test for the day...   Check the power line on the computer interface is outputting 5v, and although I didn't have enough hands to take a picture of this... 5volts it was!


But, discovered a  problem with the gripper motor - it's certainly spinning all right, but always in the same direction, regardless which way I throw the switch.   Looking back at the videos made earlier this month, It's debatable this was working correctly then....   So, I think what I'm going to continue with my program of getting the mechanics sorted first, start work on computer interfacing and programming, and will come back and debug this later....

Last week I also bought a dedicated 12v power adapter, I'm going to chop off the power connector and solder up the GX-16 connector I have for plugging into the Armdroid.   The reason for doing this is because when fully restored, I want to demonstrate the robotic arm outside my home environment, and thought the bench power supply would be a tad finicky for this purpose.

Next, will be making up the computer interface cable, and am one step closer...