February 1, 2015 electronics



I’ve been meaning to build a benchtop power supply for some time. A while back I came across an old calculator that had 3 rechargeable (dead, leaky) AAs soldered in. That finally kicked me into gear, and I set about building something.

Requirements included 3.3 and 5 volt outputs, as well as a variable output. I wanted some kind of flash, so a microcontroller driving an LCD displaying the voltage of each rail had to go in too. I also wanted it to fit underneath my plastic parts/tools bins, and have a kinda retro look to it. Finally, I wanted to build it using as many parts on hand as possible.

When it was all said and done I ended up buying a PCB, 2200uF capacitor, 2 2k pots, 2 pair of binding posts, and a 2.1mm barrel jack and plug. All were acquired at the Radio Shack 50% off store closing sale (We actually bought a lot of stuff at half off, SWMBO approved!) Everything else was already in the stash.

A 15V former laptop power brick supplies the juice. From there it goes into a 5V, 3.5A switching regulator and an LM350 variable linear reg. The 3.3V 0.5A linear reg is powered by the 5V rail. An old ATMega168 (yes, with the arduino bootloader) drives the LCD and retrieves each rail’s voltage from a MCP3208 SPI 12 bit A/D converter.

The name, YRTL-T1, is because it’s the first tool built under the YRTLBots name. I’ll draw up a proper schematic and post it sometime later. A full writeup and photos will be posted at yrtlbots.com, and I’ll end up putting the code up (probably on github) as well.

Oh, and the old calculator lit up its old VFD and worked great. I’ll put up a pic soon.


January 10, 2015 electronics, robots


What’s this? Actual robot-ing going on at the new house? Finally!

Encoder board and motor controller

November 17, 2013 electronics, robots ,

These have been done and sitting for a couple weeks. Now I’m finally getting around to playing again.

imageWheel encoder board. Two QRD1114 and a 74LS14 to square up the signal.

imageMotor controller. Built on a leftover protoboard from Gadget Gangster with an ATMega328 at 16MHz (yes, running as an Arduino) and a Pololu TB6612FNG motor driver. The two wheel encoders go to the interrupt pins. The little surface mount chip still needs its connections soldered up, it’ll be the 3.3v-to-5v I2C translator between this and the BeagleBone Black.

Now it’s time to get to some coding to see this thing actually spin its wheels.

Wheel encoders

November 1, 2013 electronics, robots ,


Breadboarded wheel encoder. ATMega328 on the left, 74LS14 in the middle, QRD1114 on the right.


QRD1114 on a radio shack proto board. So far it seems to work as expected. Guess it’s time to build the second one.


October 30, 2013 electronics , ,


My first experience at soldering a surface mount part. Not as bad as I’d feared. Though it’s the only smt thing I needed to do. I imagine doing this a lot would get pretty tedious.

That’s an ADuM1250 from Analog, which is an I2C level converter. It’ll be the translator between the 3.3V BeagleBone Black and the 5V motor controller that I’ve yet to build.

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