On watchdog timers

For many embedded software engineers, the watchdog timer is something that is designed in at the end. The thought is you just turn it on prior to shipping and “She’ll be right”. But this is a terrible travesty. Continue reading

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XBee radios

I had gotten a pair of 1 mW XBee radios a while ago. I had wanted to use them to communicate with my robot while it was running. Normally I use an RS-232 cable in the lab, but in the field a cable obviously is a ‘drag’.

Unfortunately, I was not very happy with them. They were able to run at the 115200 baud rate I needed, but the range was not what was specified.  When reading the fine print it does say under ideal circumstances. I guess 1 few inches on the ground is not idea.

So my wife just got me a pair of the 60 mW versions for my birthday. After a few screw ups on my part (you need to turn on their power source of all crazy things….) I got them working at home. I then took them out to the test area and found that they work over the entire parking lot (about +- 300 feet) without a single hiccup. Highly recommend.

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IMU heater

I am using a Pololu 9-DOF module as the IMU for my robot. Its a very small device (1.0*0.8″) using MEMS bases gyro, accelerometer, and magnetometers. The trouble is these sensors have some drawbacks. The first is that MEMS sensors are sensitive to temperature. Some make better thermometers than what they were designed to sense. So to get the best performance from them, you need to calibrate them for various temperatures or to stabilize the chip at a constant temperature. The second main issue is that the magnetometer is sensitive to (duh) magnetic fields. Not just that of the Earth, but those generated or distorted by ferrous metals or electric currents. Continue reading

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It has been a while

Life got in the way. I hate it when it does that. Why can’t things like work, taxes, dishes, and doctors appointments just take care of themselves? Why must I be involved?

But over the last few weeks I got back into the grove of things. I started working on my AVC robot. The first order of business was to learn Kicad. See (TBD)

The next learning experience was to fabricate a face plate for the sailboat project. For this I decided to try out Ponoko. You send them Cad files and they were laser cut your design from numerous flat sheet materials like paper, wood, fabric, or in my case a pretty blue acrylic. The results were fantastic, although possibly more expensive than I would like. See TBD

Next came schematic entry of my AVC design into Kicad with the idea to have a board fabricated for that. I hate the whole wirewrapped perfboard implementation. I worry about broken wires, and noise from the lack of a ground plane. I also took this opportunity to think hard about the the processor I want to use. I may start looking into the Atmel SAM-E70. See (TBD)

Over Christmas (yes four months ago) I got a Mojo FPGA development kit. Not like I needed any more projects, but I wanted to get a better understanding about them. We use them at work, and they were always a bit of a mystery to me. So I have set up the goal to include an FPGA in my AVC design and use it for various things including obstacle avoidance. See TBD

I also got the LIDAR-Lite (V2) around Christmas. I got it up and running quickly but had some small issues with it. By the time I got back to trying to figure things out, I discovered the company had been purchased by Garmin and has gone off the radar. The website it busted and the units are no longer for sale. So I will do the best I can and get it installed into my AVC entry. See TBD.

And lastly I got a small OLED display from Sparkfun. I want to use the display fold telemetry data into my Mobius action camera footage. This has been an interesting project combining optics, and electronics. See TBD.



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Incredible optical encoder

I was cleaning up my lab at work when I stumbled upon a contraction from a research project that never went anywhere. I got in touch with the researchers and asked them how they wanted me to disposition the equipment. “Don’t need it anymore, just toss the stuff” was the reply.

So I started to take this thing apart to do just that when I found a black box in the center with a rotating plate and electrical connections. I did a quick Google and found out the box was a motor with optical encoder. The resolution of the encoder is 500,000 counts per revolution! And this was the low resolution model at $5,000. The higher resolution model goes up to 2 million counts per revolution.

So obviously this did not go into the dumpster. I am now working with it at home to re purpose it for testing I need to do at work. Unfortunately we lost the controls for this rotary stage and the company will not buy them anew. So I am MacGyvering them at home. I can’t drive the motor simply as it requires 300 volts 3 phase power at 3 amps per phase. That is 2,700 watts for a motor the size of a paving brick. But I can use the encoder for feedback and a simple DC gear head motor with a friction drive on the outside rim of the round table. Add an Arduino and like Dave for EEVBLOG says “Bob’s your uncle” (or Robert’s your mother’s brother).

Tonight I got it powered up, and sure enough the A and B channels are 90 degrees out and it generate very clean TTL signals. I have nothing that can decode the quadrature encoders nor count the pulses, but just from the large number of counts I get when I touch the table, I can believe the 500,000 counts per rotation.

I have parts on order that should allow me to do the decoding and counting. Then come on Monday so I will have all weekend to drool over the device.

Posted in Personal | 1 Comment

Sailboat start timer revisited

I have been stalled in my work on my robot. Current bug just seems insurmountable. I would come home and avoid the thing like the plague. So I decided to purposefully work on something else for a while. Continue reading

Posted in PIC, Sailboat Race Timer | Leave a comment

Microscope (AmScope SM-3T)

My eyes are getting old. I can no longer focus on close items. For the last few years I used a magnification visor for close up work. But in recent time, even that is not good enough. To get close enough to solder tiny parts you set your face on fire with the soldering iron.

So, I took a deep breath and purchased a 3D microscope. I have used them for years at work and loved the ability to work for long times in relative comfort and with little eye strain. But $500 seemed like a bit much for a hobby.

But the way my eyes are, I can’t solder a 1/2 watt through hole resistor to a protoboard let alone a small SMT part. So I ordered an SM-3T from AmScope with 1/2x and 2x barlow lenses. I also got the 80 LED ring light. I did not order the video or camera options. I will wait a bit to get those.

It arrived and the unboxing went smooth. The only hiccup was their idiocy in requiring a password to download the user manual. They told me it was printed on the box, but after trying 10 different numbers I called them and gave them a piece of my mind. Would it have killed them to print a copy and include it in the box, or make it publicly available on the web?

So now I find I am spending all kinds of time in my lab looking at things. I find myself reverse engineering random PCBs because I can. I am sure the novelty will wear off in time.


Posted in AmScope | 3 Comments

Radio Shack is dead to me

I know it is not news, but Radio Shack is dead. My local store did not shutter when they went bankrupt. It has now been remodeled to bring in a cell phone store in a good 1/4 of the store. This has forced the store to drop merchandise. And what did they drop? Most of the hobbyist stuff.

What they dropped floors me. They no longer have project boxes, and prototype boards. But they do still have the rub on decals for etching your own circuit boards. What is the sense in that? Who ever was in charge of selecting merchandise for the hobby area obviously never held a soldering iron.

So my goal now, is to never step foot in the store. I will start to stock up on basic supplies from DigiKey and Mouser. Stuff like switches, a few transistors, and wire. I already have a start on being independent. It will not take much to divorce myself completely from them.

It is a sad day. I remember as a kid going to the store to browse the parts and imagine having the knowledge to use them. I then remember going to the store to buy parts I did know how to use. Now I go to the store, and wonder who might really be still using rub on stickers to make a PCB.

Posted in Personal | 1 Comment

Saleae Logic-8

I just was given a Saleae Logic-8 logic analyzer probe as a birthday gift. I am in love with not only the giver (my wife), but the unit itself. Admittedly I have only had it for an hour, but everything I have tested it against has worked nearly flawlessly. I did have one small hickup where the Windows client indicated some fault in downloading the data from the pod. But I only saw that once when I was screwing around with settings.

What came as a huge (pleasant) shock is that this is not just a logic analyzer with various protocol anayzers built in, but also a oscilloscope. Obviously this will not compete against a purpose made scope in features or specifications, but for a quick probe in the field it can’t be beat.

So far 3 thumbs up.

Posted in Product reviews | 2 Comments

First 3D printed part

My employeer has graciously allowed employees to use their top of the line 3D printer for personal projects subject to a bunch of conditions. My SUNDAR project falls within the guidlines for using minimal amount of materials and time. So for the last few months (work has been grueling) I have been working on designing the various parts I need for the sensor head.

I had some issues with finding a CADD program that would do the job. I have in fact tried 7 different programs and have rejected them all. The best of the lot so far is Cubify Invent, but even that I am not fully happy with. But with that aside, I did design a part and had it printed last night.

I am frankly amazed at the quality. Admitedly this is a huge industrial SLA machine and this part was run with the finest tip. Although not glass smooth, it came out very nicely. I will try to attach a picture soon.

Now I am off to design the rest of the parts and get them printed. What JOY!

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