2017-01-19
So after …mumble.. years my Craftsman DMM died. It was very sad, but the meter did outlasted the brand so that’s gotta be worth something. To replace it I bought the Amprobe AM-510. Very nice meter. Allowed me to finish the current loop simulator and verified that the digital milliamp readout on my power supply is more or less fantasy. Now to be fair, it’s a 5 A supply and the readout was off by Read more…
2017-01-18
The 4-20mA current loop simulator is done. Pictures of the finished product below. Most of the parts I had on hand, but did have to buy a regulator (Texas Instruments LM317L) and a 500 Ohm 0.5 Watt pot. The pot was a shocker – approx $12. I usually buy quantity 10 of whatever I order just to have it on hand, but this was an exception. The above was designed (and boy do I Read more…
2017-01-10
Starting dabbling with creating the schematics for the project. Tried several open source 2D CAD packages. I think I’m going to stick with QCAD (https://qcad.org/en/). The most important feature that sets it apart from other free CAD packages I’ve tried is the distinct lack of corrupting of drawings and loss of said drawings. I’m definitely going to have purchase a “pro” license to support development. This is really my first foray into drawing circuits. I’m Read more…
2017-01-08
The Software So the next goal for this project was to get the BBB (Beagle Bone Black) to be able to drive digital output and to setup the reading of values from a 4-20mA current loop. Googling on configuring a GPIO pin to output with pull down resistors sent me down the rabbit hole of Device Tree overlays, kernel drivers, subsystems, SysFS, and so forth. Spent two days in the fuckery that is Linux documentation Read more…
2017-01-04
Got a chance to play with the Beagle Board. Installed the latest Debian Jessie IoT image[1]. Supposed to be an alternative distribution that removes all of the GUI stuff which sounds perfect for this project since all that this BBB is going to do is sit in a closet and pretend it’s a PLC. It’s certainly much more svelte than the default distribution with X11 and what not, but it’s still bloated in my opinion. Read more…