One of the things I’ve noticed about electronic devices is that they all, unequivocally, run on electricity. Microcontrollers and small motors and actuators and sensors and such are also fairly picky regarding the voltages they’re interested in using. Primarily, microcontrollers require either 5V or 3.3V of power with very little tolerance away from their ideal supply. The flow thus needs to be very regulated.
To do this efficiently a specialized power supply is often required. Hobbyists with too much money at their disposal opt for bench supplies that have perfect little power nubs at different voltages and lots of fancy meters.
I don’t have too much money so I decided to see what I could do to make my own:
You’ll note that by checking out the back of it, it’s actually just an ATX power supply I’ve re-purposed from an old PC. The wooden carriage for it is a few slabs cut from a desk that has long ago been retired. One of those ones that you have to put together yourself alone in the dark of your apartment while you wonder about what might have been as you scrawl through useless misdirections and absent hardware. The stain for the wood is called “Anything But Particle Board” and doesn’t match at all with the PCB mill I’m working on that’s positioned next to it. The front piece isn’t attached yet, so the wiring is a little exposed at the moment. Makes for a better picture/story.
The top of it has a power switch, a voltage supply indicator light, which is illuminated when the supply is able to maintain all regulated voltages given the current power draw on it. It’s basically an “all is well” light. Above that is a reset button, and to the left are 4 terminals, for 3.3V, 5V, 12V and ground.
A nice aspect of ATX supplies is that they are wired with a non-mechanical on/off feature that allows you to turn it on by sinking the power on one of it’s pins. It also has a constant standby 5V output. By grounding the power pin the supply is turned on with the switch I’ve installed. By shorting that with the standby output, the reset button allows it to power down and restart.
Another bonus feature of the ATX supply is that it will cut off its voltage if it detects a short circuit or an unsafe draw of power. This means that it will shut down as soon as it detects itself firing watt upon watt of electricity through your overweight, out of shape shell of forgotten dreams so that you can live another day to ponder the decisions in your life that led to this point.
The Dremel is one of my favorite tools. You can basically accomplish any cutting task with one if you’re patient enough or whatever. Having recently upgraded to a much more powerful model I had the battery-powered model seen here kicking around. Needing something capable of milling and etching for the CNC machine and not wanting to waste the expense to both my wallet and the environmental factors involved in shipping a DC motor overseas I decided to sacrifice the old model.
After disassembling, here’s what there is under the hood:
A hobby-grade DC motor with a chuck attached to it and rechargeable batteries. Interestingly the batteries were advertised to have “Lithium Ion Technology” but they’re actually standard Ni-Cd batteries… the original rechargeables that have been around for about 30 years. And suck.
The unit retailed for about $60… and the parts seen above can be purchased for about $8 total individually. The rest is just injection-molded plastic.
Not finishing projects is sort of my thing. Finishing them and taking them apart when I’m done is also my thing. But against all odds work as recommenced on the CNC mill. Primarily because I really actually need it to get done so I can put it to work manufacturing parts for other projects.
Now all three axis are running on balanced threaded rod, powered by three 1.8°/step stepper motors:
Back side with cat in background offering look of approval.
The z-axis has a ridiculous gear ratio to ensure that lifting the mechanism is pretty strain-free.
Each motor was tested, everything runs, and holy shit the thing is loud. Some dampening will be needed but for a prototype, no complaints. The motor is being readied for mounting. It is a 6.2v motor that will be cranked up to 12-14v for a little extra rage. Unfortunately, the actual area it has to work with is 7″x5″x1″, which isn’t huge. But this is a proof of concept and if it works I’ll make one that’s much (much) larger. A greater z-axis is going to prove critical I suspect.
To actually run this, I have a few stepper motor drivers from Texas Instruments. Or I might just make it run directly from a dozen or so transistors and some serious power switching that will be coupled with a computer’s USB port and special drivers (that I’ll have to make) to stream bits of data directly to shift registers.
One of the cells has split somewhat. Apparently the strain of panels against plexiglass, which I have learned tends to expand and contract more than I would have expected due to temperature, has cracked it. Being made of glass and <0.2mm thick, it’s not difficult to do.
The problem is that this single crack is limiting the output of this cell by ~30% of its output wattage. That’s causing the entire panel to lose 30%. Butts.
I’ll be repairing this.
In the meantime, I noticed this at 11pm:
I stuck the above LEDs into the circuit to see what they were doing and to my surprise they were flickering right along. But why flickering? I started trying to figure out if there was any way there was an odd capacitance in the circuit that I wasn’t understanding. But no, nothing. Even with the MCU entirely powered down it was still happening. And four LEDs drawing at least 20mA a piece wouldn’t be sustained by any capacitance.
What I did notice, however, was that the flickering matched the dancing of the flame of a tiki torch lit in the backyard that was near the panel. 3v and at least 80mA coming from a single torch in what would otherwise be pitch black. Surprising…
More interesting to come, tomorrow though.
Things to look for soon: Stirling engines, Peltier cell phone charger, my take on Mr Fusion.