First prototype of a work holding tool, in this case the base plate, for milling a set of off the shelf cases from Hammond Mfg (1455 series). This is done on a scrap of 1/4" 6061, about 8x6" (its an off cut scrap). The intent is to use a piece of MIC6 tooling cast aluminum. The bulk of the work was done with a 1/4" 3-flute 38 degree aluminum end mill. The detail work required a smaller tool - I had actually made a mistake and undersize the extra well, which meant I had to use a 2mm tool - however, it would be quite possible to use a 1/8" in the final version. Read more

A quick little project as a spin-off of a larger common shared design for an aquarium controller, I’ve knocked together a small inlet sensor and 12V driver with 4 channels, allowing you to hookup a float switch or attach a DC pump across all four channels. Programming is handled by USB, or a CAN bus attachment. It shares a common CPU design and firmware build with my upcoming Reef-Pi controller and power bar, just dramatically simplified and providing a simple, safe DC output option. Read more

Small design vignette for an LED driver design for freshwater LED lighting. In this example I’m using a 28 Yuji 5038 LEDs at 6500k and 98+ CRI. Since they are all in series, it offers about 100Vf, which is out of range for most of my LED drivers. However, it only needs 150mA maximum current, so becomes a tractable problem. Fitting in a 50x80mm space small case, this LED driver + controller uses some totally over-kill CPU (ATSAME51J20) featuring CAN, USB and dimming control, with a battery for RTC backup. Read more

Just a small vignette on the milling of a Hammond Aluminum Extrusion case cap. All I have is a CNC6040 based machine with a 2.2kW spindle, but it would probably serve the purposes fine as we’re not chewing through a lot of metal.

Some updates for products over at blueacro.com - mirroed from Reef2Reef I have basic power boards already designed up, and a few sample cases in house. The form-factor is nice, though slightly tall compared to your average power strip. Probably not a major issue, as its a fair bit less wide. I’ll report back when I have some first samples assembled. The power board has a number of provisions, including protection for the relay contacts with inductive loads, without using a plain MOV or other circuit which leaks power. This adds a few dollars of cost per outlet, but ensures the relay will continue working for its entire rated life, no matter what is plugged in, and that the relay fully switches off with light loads. Read more

Let’s talk temperature sensors, at least let’s talk about the guts of a temperature sensor and less about the housing, cables, etc. There are three main varieties you’ll find in your typical “probe” style sensor, and a fourth I’ll mention because its common for integrated circuits. I’m considering “relevant reefing temperatures” to be about 75F to 83F - sorry, I haven’t switched to metric on temperature just yet, even though I reference them below. Its a hard habit. Read more

I’ve been keeping aquariums of all flavors for a very long time, and have seen and first hand experienced what happens when our lovable basic heaters (and chillers) run amok and fail to do their jobs correctly. Even worse, we often decide to go whole hog into the aquarium controller systems, which promise us web graphs and e-mails, while also being in charge of critical functions such as temperature and top-off, mixing software and control domains that should never be mixed (e.g., https://www.reef2reef.com/threads/fixing-a-broken-apex-classic-main-unit.366496/ - I’ve had units just fail, and when your entire tank runs on it, you’re SOL). Even worse, a lot of hobby gear is designed down to a price (especially with imports, or to improve margins) because, well, a lot of us end up tossing the equipment in the trash after a year either because we found a new hobby, or hated the equipment we did have. Some equipment is of course a “wear item”, but the number of stuck mechanical thermostats, or miscalibrated heaters, or heaters with bad hystersis so your aquarium swings by several degrees, or broken controllers, or heaters which explode in your tank never seems to go down. Read more

With the ongoing poor air quality all over Central California due to the Camp Fire, the interest of providing fine grained and reliable air pollution measurements peaked. One of the interesting providers of data is the website PurpleAir.com. The data for PurpleAir is sourced from a series of sensors sold through the website

Ever felt like your board level MOSFETs were too large? Texas Instruments now has an answer! Measuring in it as small as 0.7mm x 0.6mm, these FETs are small for board, but most importantly retain a sane PCB layout: the gate is actually at one end! No more squishing a layout where the gate has to trapeze through either of the high current paths, now you can more easily use two layer boards where all of the control signals to the FET are kept on the logical end of the device and nearer the MCU or other controller. Read more

Controlling pressurized carbon dioxide (CO2) delivery into a Calcium reactor or into a planted tank with precision can be fraught with problems. The conventional mechanism is to use a needle valve after a pressure regulator - this design is very finicky to adjust for low flow rates and has a tendency to drift over time, meaning your carefully controlled delivery is now out of whack. In addition, if you use a pH controller driving an AC solenoid valve, the valve actuation can be quite audible. Read more