Posts Tagged ‘ electronics ’

Tricopter: Electronics

(Disclaimer: the photos are blurry because my cell phone camera can’t focus on anything closer than 3 feet.)

The underside of my Seeeduino Mega protoshield

This is the underside of my Seeeduino Mega protoshield that will hold most of my tricopter’s electronics together.

I wired up my accelerometer (BMA180) and gyro (ITG-3200) a few days ago without too much trouble using their respective datasheets. I also put together a basic integrator for the gyro outputs to calculate angles, although I discovered that since the gyro drifts at a variable rate depending on the chip’s temperature, I can’t use a constant calibration value. I’ll have to look at that later. For now, you can see my code on github.

SMD LEDs soldered to protoboard. Blurry, but they're there!

My little victory today was having successfully soldered surface-mount LEDs (1206) to the protoboard, resistors and all (they’re the four yellow smudges!). The lights will indicate power, RSSI, and data I/O. That was the easy half-hour.

I spent three hours figuring out the schematics of my XBee Explorer board from SparkFun so I could plug the XBee directly into my protoboard. I don’t want to wire the explorer board to the protoboard because 1) that would mean two boards to mount to the tricopter chassis and 2) I get higher current capacity on the protoboard that I will need when I eventually upgrade the 1mW XBees to the 100mW version.

Fail schematics

This is my rough draft of the circuitry before I started soldering. It’s evident I got confused. I also realize now that those schematics are full of errors, but it’s not like you can read the scribbles, anyway. BAH. I’ll post more helpful CADded schematics when I have everything finalized.

The XBee datasheet was of substantial help. The schematics and CAD files on SparkFun’s product page for the explorer board also helped.

At this point, I should make it clear that wireless communication through the protoboard is not yet working. Pretty good progress for three hours, though.

Fortunately, I didn’t fry any components, not even any of the rather delicate LEDs. I scavenged a diode off a scrap motherboard, though I realize I must have wired it in backwards, perhaps causing my data transmission (the lack thereof) woes. The RSSI lights turn on if I try to transmit data (using a USB Explorer board), so I think the XBees are fine. I must have messed something up between the XBee and Seeeduino, like the diode. It’s also possible that the LEDs are drawing too much current, though I don’t see how that could even be true since the data LEDs aren’t lighting up much anyway.

I probably shouldn’t have skipped the breadboarding stage.

Raiderbot X Meeting 7, 35 Days to Robot Ship

Meeting time: 15:00 to 19:00
Hours logged: 47.86

We attached our 2005 game arm to the kitbot. It works! It’s a pretty big arm even though it doesn’t quite reach 10 ft. I can’t wait to see our four-bar linkage arm finished.

Ordering parts… We need another cRIO, but I can’t find cRIO-FRC. NI has something that looks similar, but I’m not entirely sure it’s the right one.

ES and DP are building a battery cart. I’m surprised at how complex they are planning for it to be, at least in the electronics and software aspects. It sounds like a great project. That said, I will need to keep an eye on them to make sure they don’t go for too much. I think they can finish, though.

My first robot!

My first electronics project, for that matter. I am currently taking an electronics class at my high school, and as part of the course, we are required to order and build an electronics kit. Since the kits provided were, in my opinion, too easy for me, I decided to order my own parts and build a remote-controllable robot based around an Arduino. I will try to throw together a haphazard build log here.

My first task, I decided, was to design and build a DC motor driver capable of driving four motors. I designed the PCB using KiCAD (see the schematic here and the PCB here) and ordered it through BatchPCB.

I wanted an omnidirectional robot. Both to save cost and for the additional wow factor, I decided to make it three-wheeled (kiwi drive). It will be good experience for next year’s FIRST competition anyway.

The following is my bill of materials, including where I ordered the products and their prices. I ordered many extra parts from Digi-Key so I could get lower bulk prices. I ordered the USB cable because I had too few and the extra transwheel in case I messed up while drilling holes in them. As you can see, I also took advantage of samples offered by some companies. I actually ordered samples of accelerometers and many other components not listed here that I thought may be useful in the future. Extras are indicated by an asterisk.

STMicroelectronics – $0

  • 3x* L298HN motor drivers (sample)

Keystone Electronics – $0

  • 4x 2-terminal blocks (sample)
  • 2x* 3-terminal blocks (sample)

BatchPCB – $20.06

  • 1x Custom-made four-motor driver PCB

SparkFun Electronics – $24.75

  • 1x RF Link Transmitter – 315MHz
  • 1x RF Link 4800bps Receiver – 315MHz
  • 1x Resistor Kit – 1/4W
  • 1x Polarized Connectors – Crimp Pins
  • 1x Heatsink Compound – ST350

Pololu Robotics & Electronics – $77.41

  • 3x 35:1 Mini Metal Gearmotor
  • 2x Pololu Micro Metal Gearmotor Bracket Extended Pair
  • 2x Pololu Universal Aluminum Mounting Hub for 3mm Shaft Pair
  • 1x 0.100″ Breakaway Male Header: 1×40-Pin, Straight
  • 1x 0.1″ Crimp Connector Housing: 1×2-Pin 25-Pack

Kornylak Corporation – $15.20

  • 4x* FXA208B (2051-1/4BX) CAT-TRAK transwheels

Digi-Key – $18.90

  • 1x* USB A-B (Q361-ND)
  • 10x* CAP 470UF 50V ALUM LYTIC RADIAL (P5185-ND)
  • 10x* CAP CER .1UF 100V X7R 0603 (490-3285-1-ND)
  • 18x* DIODE SCHOTTKY 60V 2A SMA (497-2461-1-ND)
  • 50x* RES 270 OHM 1/10W 1% 0603 SMD (311-270HRCT-ND)
  • 10x* LED GREEN CLEAR 1206 SMD (160-1404-1-ND)
  • 10x* LED SUPER RED CLEAR 1206 SMD (160-1405-1-ND)

Subtotal: $156.32
Total S/H: $18.39
Total: $174.71

All orders except those from BatchPCB and SparkFun have arrived. I will elaborate in the next post.