Do you have a hundred bucks and some time to kill? [Peter Sripol] invites you to come along with him and build a remotely operated submarine with only the most basic, easily accessible parts, as you can see in the video below the break.
Using nothing more than PVC pipe, an Ethernet cable, and a very basic electrical system, [Peter] has built a real MVP of a submarine. No, not Most Valuable Player; Minimum Viable Product. You see, there’s not a microcontroller, motor controller, sensor, or MOSFET to be found except for that which might reside inside the knock-off GoPro style camera which is encased in a candle wax sealed enclosure.
Instead, simple brushed motors live right out in the open water. Single pole double throw switches are connected to 100 feet of Ethernet cable and control the relays powering the motors. The camera signal is brought back to the controller through the same cable. Simple is the key to the build, and we have to admit that for all of its Minimum Viability, the little ROV has a lot going for it. [Peter] even manages to use the little craft to find and make possible the retrieval of a crustacean encrusted shopping cart from a saltwater canal. Not bad, little rover, not bad.
Also noteworthy is that the video below has its own PVC ROV Sea Shanty, which is something you just don’t hear every day.
Underwater ROV builds are the sort of thing almost every hacker thinks about doing at least once, and some hackers even include Lego, magnets, and balloons in their builds! Continue reading “Low Buck PVC ROV IS Definitely A MVP” →
[dmalhar] was digging around in his bins for motors and found one with missing brushes. Being resourceful (and not able to find another motor), he managed to tear apart a SATA cable and form the pins into brushes with just the right amount of spring. Yes, this looks like a cheap motor, but in the moment of necessity availability wins, and this hack is truly commendable. If he had used a paperclip, MacGyver would have been proud, but the SATA cable pins make us proud.
Normally the brushes of DC motors are made with a graphite or some other material which provides a small amount of resistance so that when the motor is spinning the brushes will provide a gradual shift of current from one commutator to the next. Also, the softness of the carbon makes the brush wear down instead of the commutator, and in large motors the brushes are replaceable. In cheap motors the engineers design the brush material around the expected lifetime of the product. In [dmalhar’s] case, the motor just got its lifetime extended by a while.
Brushless DC motors, and their associated drive electronics, tend to be expensive and complicated. [Ottoragam] was looking for a cheaper alternative and built this Brushed DC motor servo controller and the results look pretty promising. Check out the video after the break.
He needed a low cost, closed loop drive for his home-brew CNC. The servo drive is able to supply a brushed DC motor with up to 7 A continuous current at up to 36 V which works out to about 250 W or 1/3 HP. It does closed loop control with feedback from a quadrature encoder. The drive accepts simple STEP and DIRECTION signals making it easy to interface with micro controllers and use it as a replacement for stepper motors in positioning applications. All of the control is handled by an ATmega328P. It takes the input signals and encoder data, does PID control, and drives the motor via the DRV8701 full bridge MOSFET driver. There’s also some error detection for motor over-current and driver under-voltage. Four IRFH7545 MOSFETs in H-bridge configuration form the output power stage.
This is still work in progress, and [Ottoragam] has a few features pending in his wish list. The important ones include adding a serial interface to make it easy to adjust the PID parameters and creating a GUI to make the adjustment easier. The project is Open Source and all source files available at his Github repository. The board is mostly surface mount, but the passives are all 0805, so it ought to be easy to assemble. The QFN footprint for the micro controller could be the only tricky one. [Ottoragam] would love to have some beta testers for his boards, and maybe some helpful comments to improve his design.
Continue reading “Brushed DC Servo Drive” →