Switec X27.168 Breakout Board

Yet another breakout board for a Switec X27.168 stepper motor. It's just like the others except it's round! The board is tested and functions. It uses Fairchild/ON Semiconductor 1N4148 diode to protect the microcontroller.

UNI-T UT61E Auto Power Off, Part 3

It's tested and functional. I tested with just an IR LED hooked up to a power supply and the meter enabled and disabled the auto power off feature.

On the serial cable, I placed a jumper between pin 2 on the d-sub connector and R2 (red box). A 10k resistor was also put down (purple box). Oh yeah, and the IR emitter too (orange circle).

Again, all circuit diagrams used can be found here. Thanks Mr. Herbert!

To-Do's

-test serial cable

BOM

1x of LiteOn LTR-4206E phototransistor ... 3mm ... Digi-Key 160-1030-ND.
1x of LiteOn LTR-4206 IR Emitter ... 3mm ... Digi-Key 160-1988-ND
1x of 100k ohm resistor ... 0805 ... Digi-Key 311-100KCRCT-ND.

1x of 10k ohm resistor ... 0805 ... Digi-Key 311-10.0KCRCT-ND.
1x "UNI-T UT61E Auto Power Off v0.1" circuit board from OSHPark.
30 AWG wire similar to Digi_key K395-ND. 

UNI-T UT61E Auto Power Off, Part 2

I've been procrastinating a little because opening the meter means dealing with thin, delicate wires from the backlight mod.

With the meter splayed open, I located the trace that needed cutting. The IC is a CyrusTek ES51922 and the pin that needs isolating is pin 111 - RS232. It's the 9th pin down from the "top". The cut is highlighted with the blue line.

The jumper wire is then soldered to that pin and routes through the circled via to the "P" solder pad on my APO board. It's labeled "P" for some reason I've since forgotten about.

Placing the APO board - The IR windows on the case have a center to center spacing of about .65in (16.5mm). A little hot melt tacks it in place.

Power and ground were then routed around very carefully around that big hole, over the trimmer thingies and past the after-thought capacitor. After I did this, I realized I could have used much shorter wires and solder to the nearby caps for power and ground. A bit of heatshrink shrouds the receiver to avoid possible interference.

A bit more hot melt and it was ready to close up and test.

After assembling the meter and powering on, the PC icon was gone and a new timer icon showed up. At this point, my backlight mod stopped working and the meter was opened up again to investigate. Yup, a thin wire had broken off the backlight board. This has been fun but I think in the future I'm going to keep my meter in its stock condition :)

Continued in Part 3.

Little Stick Vise

A complete ripoff of the original stick vise by Alex Rich.

• Jaws open 4.25"
• Jaw width is 2.5"

Jaws and knob are from Protolabs.The blue jaws have a nice low profile, and the purple set allow boards with components on both sides. The ring is for hanging it on a hook. I'd like to share the design files but haven't decided which crowd/cloud system is the best.

Remote Temp

Remote Temp is a 2.4Ghz radio, battery operated microcontroller board or sensor node. This would be something you could hang in a tree outside or hide in the attic and gather environmental data. Some of the design ideas fermenting are ...

• Battery operated and therefore low power
• Use rechargeable AA's (3x) or alkaline (2x) and fit within the foot print of AA battery holder
• Have connections for the "regular" NRF24L01+ breakout board with the meandering PIFA antenna and the high power PA LNA style. 
• SPI-Flash because I'm borrowing design elements from Mr. Rusu's excellent Moteino line.
• ICSP and FTDI capable. FTDI for the base station.
• IO header.
• 2x LED's.
• 3x tactile switches for input and reset.
• Sensors: foot prints for Bosch BME280 and Microchip MCP9700.

And now some explanations of those ideas in order of listing.

The problem with rechargeable AA's is that their initial voltage after charging can be up to 1.8V but after use they plateau around 1.2V. So the rechargeables need regulation but the alkalines don't. So you have the option to populate the regulator and use whatever you want as a battery or solder a jumper and skip the regulator. I'm still deciding if I want over voltage protection built in. One power connection features is that you can't plug in an FTDI friend and battery connection at the same time. They share the same ground pin. I'll probably be fiddling with these two connections the most.

Two NRF headers is a device foot print thing as the high power radio is significantly longer. I want the overall device to fit both the regular and high power radios without a major redesign. If possible, the same enclosure should be used for either one. And the board is sized to fit within the dimensions of a 2-cell AA battery pack. Is having twice the traces for this a good idea? I guess I'll find out. It's 1.25" x 2.00".

On-board memory seems like a good idea. Who knows if I'll use it. Design wise, it is voltage constraining because its lowest operating voltage is 2.4V and the nearest appropriate brown out detection levels for the 328P is  2.7V and 1.8V. I'll probably want BOD enabled when using the flash memory. So while I can rely on the flash working with 2x rechargeables putting out 2.4V, I won't know when they dip below that near the end of their life. Contrast that with two alkalines putting out 3V and the 2.7V BOD level protection. What's the point of logging temps or events if you're just going to write garbage and lose your time investment?

Programming. Data received from remote units will most likely be routed serially to a host, hence the inclusion of the FTDI port. The ICSP is for setting fuses, bootloaders and the like. Most likely the "base station" will have an FTDI programmer hanging out of it.

General IO, switches, blinky ... nothing fancy here. The two hardware interrupts of the 328P are routed to one of the tactile switches and the other to the IO header. SDA and SCL are also present on the IO header in case I want to use an I2C sensor or OLED display.

To be continued ...

Oh and some other people have done it like here and here.