Robotic Arm Redux

I made another modification to the robotic arm. First, to make sure a jack will trigger the lever switch, I covered the end of the arm with neoprene foam. That makes it more likely the robot will detect jacks when they are picked up off-center.

I saw a problem were the arm successfully picked up a jack, but then dropped it after rasing the arm. I'm going to need to add a line of code to the robot to check the switch at the end of the arm one more time after the arm is brought up. I only have three bytes of memory left, I hope I can shoehorn that in.

CheapBot Robotic Arm

I've started testing a robotic arm for my line of CheapBot robots. It's easy to make an arm raise and lower, but I've had difficulty designing an end effector for it. It has to be light weight and reliable. After reading about the wire snare used on the Space Shuttle robotic arm, I decided to give it a try for the CheapBot robotic arm. The arm prototype is attached to my CheapBot test bed in the image below.

You can see a lever switch attached to the nose of the arm. That's so the robot can detect that it has picked up an object

In the snare test video above, you can see the piano wire snare extend, the arm drop, the snare retract, and the arm raise with the toy jack.

Look for one or more arm kits (I'm working on a second design), a radio, and smart beacon kit early next year.

May all your holidays be robotic.

Squeak eToys

Squeak will be one of the installed applications for the One Laptop per Child program (http://laptop.org/en/). It's a neat application and a good way for kids to show what they have learned (it would go great in combination with a Power Point).

I just completed my CheapBot Squeak program for my Constructivist Philosophy class and will post the final program on my webpage (NearSys.com) under the catalog link this weekend. It's a work in progress and over the months, I hope to include programs that simulate more features of the CheapBot and even create simulations of a near space mission.

ARHAB Email Traffic

I've been looking into email traffic for ARHAB groups on Yahoo. I created the following chart in the hopes that I'd see email traffic increase for GPSL meetings. It looks like a weak correlation, but something is there. Next to apply some statistics, rather than rely just on looks.

Squeak eToys

My CT 871 class has me writing programs using eToys. It's a menu driven programming language and is pretty good at letting help kids write applications that demonstrate what they know. Kids can write games or simulate physcial systems, like orbiting planet or bouncing balls.

For my final project, I'm writing a simulator for the CheapBots. The simulator lets a person control the H-Bridges of the robot in order to drive it around. In other words, the user acts like the robot controller. Future abilities of the program will let users observe the responses of the CheapBot Line Follower as the robot drives around.

The software is free at www.squeakland.org

Near Space Horizon

(Click on image to see a larger image)

This is my first attempt to limb sound from near space. These images were taken every 10,000 feet and stitched together. I tried to select the best, where the camera was pointed in the same direction. As you can see, they don't all line up properly, but it is a start.

In the future, I'll fly a sun sensor to let the flight computer align the camera properly. I also need to calibrate the field of view of the camera so the horizons can be properly aligned in the images (the horizon is depressed in near space - my photo montage assumes the horizon is not).

I'll put an article together for Nuts and Volts on this line of work. I assume it will be useful for detecting haze layers, including volcanic ash, in the future.

CheapBot Radio Antenna

Today I'm planning to solder the antenna for the ChepaBot radio controller. I purchases a SMA to SMA extension cable from Jameco for this. I'll cut the coax cable in half, peel back the inner conductor adn outer jacket, and solder wires to them.

The radios opewrate at a frequency of 434 MHz. If I take that frequency and divide it into 486, I get the proper length of the antenna (which will be a dipole). That comes out to 1.078 feet, or 12.936 inches. Divided in half and I get each element should be 6.5" long.

You can find an antenna calculator at http://www.crompton.com/wa3dsp/hamradio/antcalc.html

RC for Robots

I'm soldering a test board for a robot radio. To use it, you program a robot to respond to one of eight messages sent by the hand controller. The robot has its own radio and will reply back to the messages you send it. The handheld controller will have an LCD so human readable messages can be displayed.

The hand controller communicates with your robot like we communicate with rovers on Mars. Messages sent to the rover are acted upon, but intelligently, not as an automatic reponse like an RC car. That way, if you send a message to drive off a cliff, the robot can analyze your message and refuse to comply. Not only will it refuse, it will also send a message back about why it isn't complying.

Robotic Arm

I'm working on a simple robotic arm design for the CheapBot robots. It uses two servos, one to lift the arm and the second to pul a wire lasso tighter. The wired lasso is made from piano wire, so it naturally wants to spring open when the smaller servo extends the wires. Both ends of the wire lasso attach to the servo horn, so when it moves the ends of the wires one inch, the lasso expands by two inches.

I want to try a thinner wire. To make it simple to use, the lasso must be really flexible to wrap around the target regardless of how sloppy the positioning between the arm and the target is. The wire lasso also keeps the end of the arm very light, an important issue when you have a six inch long arm (you can build up a lot of torque for the servo to lift).

Rubber stoppers take out some of the slop in holding the target. I need to find a lighter weight "cushion" for this purpose and an easy way to mount it. I'll look into a foam rubber shirt for the end of the arm as a replacement.

I'll post some pictures soon.

NearSys 09G and H

Here are some images taken on last Saturday's mission.


This one was taken shortly after balloon burst. From around 80,000 feet, we're looking at the cloud cover over Melvern(?) Lake.

We're getting closer.....

Webpage Updates

I've started posting updates from the last near space mission. I'll massage some of the student Balloonsat data, but want to let them work their data over before I post the results.

Since it was two flights, there are two webpages for the results.

http://nearsys.com/arhab/flightdata/2009/g/index.htm
and
http://nearsys.com/arhab/flightdata/2009/h/index.htm

The only bad thing to happen was nylon zip ties failing and dropping one of the trackers (it's battery was dead by then). So it looks like I'll start some testing of zip ties in cold temperatures to see what I can learn from the experience.

The Ft. Collins Balloon Story

I helped launch two weather balloons this weekend. They were for Univeristy of Kansas and Kansas Wesylan University students. Some of these students will become science teachers and because of this experience, they will launch BalloonSats for their students.

However, after listening to the Balloon Boy story out of Fort Collins, I can't help but wonder if this is going to impact amateur near space exploration. All it takes is for one irresponsible person to negatively change public perceptions of amateur science in general and near space ballooning in particular. If as a result, access to near space ballooning is stopped or limited, students who's only dream is to launch experiments into space will be denied the opportunity of reaching this dream by taking their first step into near space.

Gawker is carrying an expose on Mr. Heene from a former friend and it doesn't cast a favorable light on him. I can understand Mr. Heene's concern if the balloon got away from him and he wanted to get it back. That however, does not excuse reporting that his son was onboard as a way to get state and federal government to track it. Claiming your son is onboard also reflects a lack of forethought. What are you going to say once the balloon is recovered (and it will) and its discovered no one was onboard?

I hope the public realizes Mr. Heene is not the face near space exploration.

Tracking

Last chase I used a D7 and Garmin GPS V. They sat on the dash and did a lot of dancing around during the chase. Today my students are helping me make a dash-mounted platform to hold the radio and GPS. They are mounted so I can read the displays from both devices, but it would be better to have a navigator go along to read.

The system is simple and starts up as soon as you apply power. That means no waiting to boot a PC or load software.

NearSys 09F

We may be launching two near space missions this week. The flights are for the University of Kansas, School of Education and Kansas Wesylan Univeristy. The person who made this all possible is Pete Sias, the man who got me started in near space exploration 15 years ago.

The launch takes place Saturday at 8 AM from trhe KWU campus. You should be able to track the flight at one of this webpages.

map.findu.com/kd4sth-4
map.findu.com/kd4sth-8
map.findu.com/kd4sth-9

Onboard will be five KU BalloonSats and at least one experiment from the KWU Physics club.

I'll be flying the reuseable lunch bag tracker I'm developing for Popular Mechanics, an old backup tracker, and a module with a new flight computer. This module carries most of the science. It will measure cosmic rays, weather conditions, internal temperature, and several cameras, including still and video.

CheapBot MagArm

Using DALPro presensitized copper clad and ARES Lite, I created the magnetic robotic arm for my line of cheapBot robots. I used a Dremel drill and its drill stand to drill out the board. The PCB still has to be populated and I hope to do that this weekend. A reed relay (and anti-kick back diode) powers the electromagnet. The PCB has drilled holes for mounting the arm to a servo. The servo allows the arm to be raised and lowered. The lifting servo and arm can be mounted to a second servo to allow the arm to rotate. But for beginners, I recommend using the robot to rotate the arm instead.

The CheapBot MagArm will allow robots to pick up slightly modified ping pong balls. This gives students the challenge of programming the robot to pick up stuff without spending more time trying to make the system work mechanically.

Smart Proximity Detector

The Smart Proximity Detector I have developed uses a PICAXE-08M to control the blinking of two IREDs. The detector mounted in the middle of the PCB determines if there is a reflection from the IREDs. Since the PICAXE controls when and how fast each IRED blinks, it knows what condition created the reflection. The detector is most sensitive to 38 kHz IR and gradually gets less sensitive as the frequency gets off center. This gives the PICAXE a way to "estimate" a distance to the reflecting object and if it is located across the robot, or just on one side or the other. Not only can an object be detected across the robot, but if there is significant difference in the distance on the left and right side, that can also be determined.

The boards tested fine, so look for kits on Nearsys.com/catalog shortly.

Magnetic Robot Arm

Last night I came up with a solution for a lightweight, but inexpensive robot arm for CheapBots. The arm is 0.6 inches wide and 5 inches long. Its grasper will be switched for an electromagnet. A relay will control the current for the magnet since the robot controller cannot provide that level of current. The arm will be light enough that a small servo can raise and lower it. The servo and arm will be turned on side, but a second servo could be mounted below to allow the arm to rotate about the horizontal plain.

I'm looking into hall effect sensors now as a way for the robot to detect the presence of a magnetic field. That should help the robot align its arm, because the objects it will pick up will be ping pong balls with small neo magnets glued inside (the bottom of the ball will have a cut hole so it doesn't roll).

Perhaps I can shoot the PCB for the arm tomorrow.

NearSys 09F Winds Aloft

This chart was developed from APRS data (positionn reports) transmitted by the near spacecraft. As you can see, the winds aloft were preetty strong and the thickness of the high speed winds was pretty large. No wonder it recovered 112 miles away!

NearSys 09F

Here are a couple of images from my last mission.

The balloon has burst and we're parachuting back to earth.

This is on ascent. The near spacecraft has just broken through the clouds.

NearSys 09F

NearSys 09F reached an altitude of 79,414 feet. It recovered 112 miles away, further than we were planning. That's because the jet stream was much faster than expected. That along with the traffic jam near the end of the turnpike made for a slightly frustrating recovery. Once we got everyone together, we drove to the last know location (4,000 feet AGL) and figured the near spacecraft drifted another 1/2 mile. Once we got close, we began picking up packets again.

The tracking modules based on the MicroTrak 300's had trouble getting packets to us during the chase. However, the APRS gateways put plenty of packets on the Internet. Um, this calls for some investigation. If you know of someone who can help me analyze the radiation pattern and strength of the transmitter, please let me know.

I'll post more information on Washburn's first near space flight in the next few days. There will be a full report on my website.

Washburn University Launch

This Saturday I'm helping Washburn launch their first near space mission. Since I completed the tracker for my Popular Mechanics article, I'm going to send it up for a real test. I'll add an additional two trackers as backup. I believe in using two trackers, in case one fails and since this will be the first flight of the Pop Mech tracker, I'm sending the two trackers as back up for it.

The three trackers are transmitting as KD4STH-4, -8, and -9. The frequency for all three is 144.390.

In addition, this mission will carry the thermopile telescope I designed. It also has a weather station like the kind I'm selling, two video cameras (one pointed up and the other pointed down), digital still camera recording horizontal pictures every 15 seconds, and an accelerometer.

I'm looking forward to a fun flight. If you're in the area, come on out.

Fisheye Photo

Here's an image!! The University of Nevada, Reno did a near space launch this week. Onboard their near spacecraft was a camera with a fisheye lens pointed down. Check their Flickr site for this impressive image.

http://www.flickr.com/photos/40137058@N07/3963101620/

Smart Proximity Detector

The PCBs I've designed for the Smart Proximity Detector are int eh mail. I expect them this week. The detector uses a PICAXE-08M to operate IREDs and a 28 kHz detector.

I'm starting to pack kits. I began by creating a spreadsheet with a list of the parts and costs. After that, I'll copy the list of parts into a word document and print that out. I follow what's int he document to pack the bag with parts. I also write the number of items that goes into each bag. That way, after I collect the parts on the list, I do a final count before packing them into their bag. However, before packing each bag, I now affix a label on the outside of the bag with teh name of the kit.

The bag for the prox detector is a sandwich bag, since the PCB is six inches wide.

The Smart Proximity Detector is for any robot that can receive serial data. Look for it under Catalog at the NearSys.com website shortly. I have a video demonstration of a robot using the detector that I am completing. That video along with directions and a copy of the code will be available online for free.

NearSpace UltraLight

I had a request for the NearSpace UltraLight flight computer. I've started soldering parts together for the board, but haven't completed it yet (or tested).

The flight computer is like a BalloonSat Easy with a built in radio and GPS Port. After building one, you just need to attach the antenna, batteries, and GPS receiver and you're ready to fly. The final kit will include memory (which the version 2.0 BalloonSat Easy doesn't) and a coax cable and wire for making the antenna. It will be my most expensive kit since it includes the $60 radio transmitter. But overall, it should be one of the least expensive ways to ow a flight computer suitable for near space missions.

One day, I hope to enter into the model rocetry field with a line of model satellite payloads.

Tuning a IR Beacon

I've developed a 38 kHz IR beacon for the CheapBot-08. It uses a 556 timer IC to create and combine two square waves. Half the 556 generates a 38 kHz square wave and must be adjusted for the proper frequency (this accounts for the tolerances in the resistors and cap). The second half of the 556 generates a roughly 10 Hz square wave. Combined, the output is a 10 hZ square wave of the 38 kHz beacon. Shutting off the 38 kHz beacon every 0.1 seconds prevents the robot's 38 kHz detector from losing senstitivity to 38 kHz.

I thought I'd just put the 556 on the o'scope in class and tune it up (adjust thwe PCB's pot to get the proper 38 kHz pulse). But I had forgotten that the o'scope would trigger on any signal, whether it was from the 10 hZ of the 38 kHz square wave.

I finally tapped into pin 5 of the 556 to see just the 38 kHz signal. It looks like on the next design, I'll add a test point to the PCB to make tuning the 38 kHz side easier.

BalloonSat Kits

I think I'd like to start a line of BalloonSat kits. This would be for the airframe and not just the flight computer. A kit would consist of seven sheets of Cellfoam 88, dowels, 1/4-20 nylon bolt, washers, black marker, tubes, plastic sheet, space blanket, and some tape. There would be enough material to make an airframe large enough to hold a video camera, flight computer, and and experiments.

This means I need to get the book together (see my Citizen Scientist articles) for directions and recommendations. The book I plan to publish through Create Space. However, I'll need an ediotor to read over the book first.

Now if there was a way to make a camera kit.

CheapBot-08 Radio Slave

Since the PICAXE-08M has such little capability for a robot, I'm incorporating a second into a robot to handle the radio communications. Using a serial port basically converts the two I/O ports required for the radios into one. Now to figure out the two way communication protocol between the nmaster and the slave.

Find Me Spot

Find Me Spot is a GPS tracking system that communicates position reports through a satellite. If you attended GPSL 2008, you'll be familiar with this tracker, as Bill Brown gave a presentation on it. Bill is doing the coolest stuff, you should get to know him.

With all the talk about the MIT flight that used a cell phone for tracking, I'm wondering about writing an article on using Find Me Spot to track. This would allow someone who does not have an amateur radio license to launch near spacecraft. Of course, the tracking unit would have to go up as a back pack with a Tickle Me Elmo to create a Find Me Elmo.

CheapBot-08

The smallest, simpliest robot controller I have created is based on the PICAXE-08M. With only five I/O pins, it's a tough one to build a robot controller around. Of those those five I/o pins, only three are truely I/O. One is an input only and the other is only an output.

Problem number one was the H-Bridges. With a code space of only 256 bytes, it was important to incorporate two H-Bridges into the design. That way it only takes two short lines of code to drive or steer the robot and the PICAXE could do other tasks simultaneously. But it takes four I/O pins to operate two H-Bridges. What could a robot controller do with one I/O pin?

My solution was to double-up the function of one of the I/O pins. It controls the drive of two motors and therefore leaves the robot controller with two I/O free pins. So now the robot can walk and chew gum at the same time. However, it can't pivot about its center - it has to turn centered on one wheel.

The turning subroutine has the robot taking turns pivoting on the left and right wheels. I call it psuedo-zero turn radius. Since it takes so little memory to turn the robot, the extra code space required doesn't fully offset the gains in the extra I/O.

Electronic Supplies

What we need around here is an electronics supplier. I ran out of parts filling an order and had to order them online last night. Wouldn't be nice if enough people did hobby electronics to justify stores (like the old Radio Shack) carrying parts again.

It's up to small businesses like NearSys to specialize in types of electronics that hobbyists might like to purchase.

Do we have a problem in the US that not enough people are doing hobbies?

Smart Proximity Detector Movie

This weekend I plan to begin editing a movie on my Smart Proximity Detector. The detector is programmed to send range information from its left and right side sensors. The robot in the movie (a CheapBot-14 controller on a CheapBot body) is programmed to drive away from the nearest obstacle. It's fun to watch the robot steer away from the plastic wall I swing in front of it.

GPS Simulator, Part 2

The GPS Simulator only creates GPGGA sentences. That's because the memory in the PICAXE-08M is limited to 256 bytes. And it was tough to cram that much into that limited amount of space. Eventually I'll get around to creating a simulator that produces all the GPS sentences in a way that looks like a near spacecraft on a mission. That's the one I'd like to produce as a kit.

GPS Simulator

I've been building new GPS Simulators for a customer in Texas. The simulator uses a PICAXE-08M to send sentences that look like the GPGGA sentences of a balloon in flight. Eventually I'll move this to a larger micro and have it simulator all the sentences of a GPS receiver on a balloon flight. Using the simulator lets you test a flight computer's program on the ground.

A ground test like this lets you find errors without leaving the ground (where it's a lot cheaper to correct).

Line Follower and the Creation movie

I've updated my online catalog with a movie about the CheapBot line follower. It's a four inch wide PCB with two pairs of IR LEDs (IREDs) and phototransistors. The IREDs constantly emit IR. If the neighboring phototransistor detects a reflection, then the surface below the pair is white. No reflection detection means there's a black strip below that side of the robot and corrective action is necessary.

The phototransistor and its collector resistor behaves like a voltage divider. In the non-conducting state, conventional current flows from the positive supply, throught the resistor, and to the robot's I/O port. This means a positive five volts is detected by the robot controller (AKA a logic high). When the phototransistor is conducting, current from the collector resistor flows through the phototransistor to ground. This leaves no current (or more accurately, very little current) to flow to the robot controller. As a result, the controller see less than 1.4 volts, or a logic low.

I read earlier today that the movie, Creation, which is about Charles Darwin, can't get an American company to distribute it. Amazing, we live in the 21st century, but some throw-backs are going to make it too contraversal to show a movie about Darwin's most important contribution to science.

Thermal Test Results

After about a 45 minutes test, the interior of the lunch sack was 50* F warmer than the chamber's air temperature (-10 vs -60). And this was with one sheet of foam rubber missing and no power applied to the tracker. I did notice the antenna elements did get stiff. But they are silicon jacketed 14 gauge stranded wire, so it should be just fine.

I need to look up some information on Rocketman parachutes to finish this article for Popular Mechanics online.

Thermal Testing

The movie 9 wasn't that great, but it's animation was. The story had promise, however.

I built a thermal test chamber years ago that circulates cold air around a test subject with air fans. Dry ice is loaded into a metal in basket and then two smaller in baskets sit on top of the dry ice. The experiment sits on top the stacked baskets allowing cold air to flow around the experiment.

Right now the Popular Mechanics near space tracker is inside. I plan to let it chill for 30 minutes (at least) and compre the internal temperature of the reusable lunch sack to the outside air temperature. The dataloggers for this test are Hobos.

Popular Mechanics Tracker

Thanks to help from VHS Products, I have a current version of the MicroTraker 300 to use for my Popular Mechanics article. I was using their version 1.3 initially, but having trouble with it.

The Pop Mech article I'm writing explains how to build a near space tracker inside of a reuseable lunch sack. This is similar to designs by NSTAR and TVNSP. The goal is to keep it cheap, but leave room for expansion and flexibility.

This afternoon I'll watch the movie 9. It takes place in a post-human world were humans are destroyed by their technology. Ummm, should I be building robots?

CheapBot Beacon

I've started designing a smart beacon for robots. The beacon will flash one of four signitures in IR based on the setting of a jumper. It uses a PICAXE-08 that will measure the voltage generated by the jumper setting. The jumper portion of the circuit consists of four resistors in series to make a voltage divider. So a jumper setting creates either 1.25, 2.5, 3.75, or 5 volts for the PICAXE -ADC. When the PICAXE powers up, it will measure the ADC input voltage.

Now the PICAXE can't send enough current to all the IR LEDs (IREDs). So it triggers a transistor when then provides the power for the IREDs. A chromed ball above the IREDs (which are pointed inwards and up) will fan the IR out in all directions.

After completing this design, I'll build a PCB for a IR beacon detector that robots can use to locate beacons.

A beacon placed on a robot locates the robot. But a beacon can also be placed on a destination for the robot to find.

Smart Proximity Detector

A PICAXE-08M operates the proximity detector. It takes turns flashing two IR LEDs (IREDs) at six different frequencies. The detector between the pair of IREDs is most sensitive to 40 kHz flashes. So when the IREDs are flashed at a different frequency, its ability to detect reflections is reduced (it can't see obstacles as far away). So the PICAXE flashes an IRED and checks with the detector to see if it saw the reflection.

The PICAXE cycles through all six frequencies until there are detections on both the left and right IREDs (the only time it runs through all six frequencies is if the IR detector doesn't ever detect a reflection). The PICAXE then sends a serial message with the range to the obstacles as thety appeared to the left and right IREDs. The range of dfistance is from 1 to 6, with a value of 7 indicating there was no reflection or that the obstacles are infinity far away.

The robot reads the data from the proximity detector as it needs to and then acts on the results.

Here's the code as it is currently written.

symbol RightDetect = B0
symbol LeftDetect = B1
symbol distance = B2
symbol counter = B3
symbol RightDistance = B4
symbol LeftDistance = B5
symbol left = 1
symbol right = 4

Proximity_Detect:
RightDistance = 7
LeftDistance = 7
for counter = 1 to 6

CheckRight:
if RightDistance < 7 then CheckLeft
low right
high left
gosub Flash
RightDetect = pin3 '0 = detect, 1 = no detect
pwmout 2 off
pause 2
if RightDetect = 1 then CheckLeft
RightDistance = counter

CheckLeft:
if LeftDistance < 7 then FinishCheck
low left
high right
gosub Flash
LeftDetect = pin3 '0 = detect, 1 = no detect
pwmout 2 off
pause 2
if LeftDetect = 1 then FinishCheck
LeftDistance = counter

FinishCheck:
if LeftDistance < 7 then IsRight7
goto Repeat_Flash

IsRight7:
if RightDistance < 7 then Report

Repeat_Flash:
next

Report:
serout 0,T1200_4,(255,"L",LeftDistance,"R",RightDistance)
goto Proximity_Detect

Flash:
if counter > 1 then Check45
gosub kHz46
goto End_Flash

Check45:
if counter > 2 then Check44
gosub kHz45
goto End_Flash

Check44:
if counter > 3 then Check43
gosub kHz44
goto End_Flash

Check43:
if counter > 4 then Check42
gosub kHz43
goto End_Flash

Check42:
if counter > 5 then Check41
gosub kHz42
goto End_Flash

Check41:
if counter > 6 then Check40
gosub kHz41
goto End_Flash

Check40:
gosub kHz40
End_Flash: return

kHz40:
pwmout 2,24,50 ' 14 inches
return

kHz41:
pwmout 2,23,49 ' 10 inches
return

kHz42:
pwmout 2,23,48 ' 9 inches
return

kHz43:
pwmout 2,22,47 ' 6 inches
return

kHz44:
pwmout 2,22,45 ' 5 inches
return

kHz45:
pwmout 2,21,44 ' 3 inches
return

kHz46:
pwmout 2,21,43 ' 2 inches
return

Proximity Detector

I've developed a smart proximity detector for robotics. A PICAXE-08M flashes two IR LEDs at 40 kHz (one at a time). The 40 kHz IR detector between the IREDs determines if there is a reflection from the IREDs. The PICAXE monitors the output from the detector. Since it knows when it flashed each of the IREDs, it knows which of the IREDs caused the reflection. The IREDs are mounted on the extreme left and right sides of thePCB giving the smart proximity detector the ability to determine if a wall is located on the left side, right side, or across the front of the detector.

Eventually I'll flash the IREDs at different frequencies to determine if the wall is located farther away or closer.

but first, I have to set my wait period between left and right flashes. I don't know how long the detector "remembers" that it saw a reflection.

Easy Star Gazing

One of my hobbies is astronomy. Currently I'm giving introductary astronomy lessons quarterly at two public libraries. My latest presentation is available online at nearsys.com/easy/. There you will find a Power Point and supporting handouts.

BalloonSat Launch

I have a near space launch scheduled for September 26th. This will take place in Salina, KS with the help of Pete Sias, the guy who got me started in near space. The launch will carry five BalloonSats my CT442 class is assemblying. I also hope to carry the lunch sack tracking module I'm developing for my Pop Mechanics article.

Popular Mechanics Article

The PM online artcile I'm writing uses a MicroTrak 300 and Garmin GPS-18X. The container for the electronics is a insulated lunch sack. The lunch sack is an Artic Zone bag that should provide some insulation and cushioning.

The batteries recommended are photo lithiums. I've used them before in near space.

LabPro UVA and UVB

Two of the LabPro sensors I'm nmost interested in seeing operate are the UV sensors. They're mounted inside a thin tube, so I suspect they're direction sensitive. I'll recommend my students mount them inside a ping pong ball (acts as a diffuser) and point them up through the top of the BalloonSat.

LabPro Dataloggers

The latest datalogger I'm playing with is the LabPro by Vernier (http://www.vernier.com/). The logger/programmer is smart, it detects the sensors plugged into it. After collecting data, the programmer then processes the data appropriately for the sensor and displays the results in a chart. You can export your data into a text file for processing in a spreadsheet. That's great for incorporating GPS data. I'll post my notes on using the datalogger on my website alogn with some pictures on making a LabPro BalloonSat.

Vernier is popular in science classrooms.

Calculating Distance to the Horizon

You can calculate the distance to the horizon with a simple equation. The real equation involves trig, but this one gives a nearly identical answer.

Dist(in miles) = sqrt[height(in feet) X 1.5]

Multiple the altitude in feet by 1.5. Then take the square root of the answer. The distance to the horizon is in miles.

Since my eyes are 6 feet above the ground, I multiply 6 by 1.5 to get 9. The square root of 9 is 3. So the distance to the horizon for my eyes is three miles.

A near sapcecraft at 90,000 feet sees 367 miles to the horizon. Because of refraction, radio should reach a little bit further.

St. Louis Arch

The arch in St. Louis is welded stainless steel. I took this photo of it after my trip to the top. The ride to the top is inside a space age capsule that holds five. At 630 feet tall, I calculate I could see 30 miles to the horizon.

DALPro

DALPro is a physicaly small shop, but they sell around the world. The original company was called Kepro, after the owner. They went out of business in 2004 and D and L took over. A Kepro board was used onboard the first space shuttle launch. I'll have to find out where. It's it amazing that the PCB materials you can purchase today for your projects was good enough for a manned space launc in 1981?

Printed Circuit Board

I begin the process of making printed circuit boards (PCBs) by using a programm called Ares Lite. The file is printed as a copper mask and transferred to a presensitized sheet of copper clad. The copper clad is manufactured by a company named DALPro and they're based in St. Louis. This weekend I'll get a chance to pay them a visit and I'll post my impressions.

The product is great, I encourage everyone to try it out.

Smart Proxmity Detector

I'm soldering a smart proxmity detector PCB. It uses a PICAXE-08 and will communicate with the robot it is attached to. The idea is that its PICAXE flashes two IR LEDs in sequence and looks for a sign of a reflection from the 40 kHz IR detector. The result is sent to the robot controller as a serial message. The PICAXE can operate the IR LEDs at a range of frequencies, allowing the proximity detector to estimate distances to obstacles. Since there are two IR LEDs, the proximity detector determines whether the obstacle is on the left, right, or both sides.

NearSys Ultralight flight computer

I'm still plugging away at soldering the new flight computer together. It uses an I2C memory chip to store data in EEPROM. A MicroTrak 300 is the onboard transmitter. The goal is an affordable solder kit to help new groups get near spaceborne.

New Flight Computer

I just received a new flight computer PCB. This one uses a PICAXE-28X and reads GPS data in background. Its built-in radio is a 144.390 MHz transmitter by Lemos. The pads for the antenna connector are good but for one. I'll drill it out for this test, but will modify it for the production boards.

New Flight

Channels in Styrofoam

To avoid taking up volume inside the BalloonSat airframe, I cut channels into the walls of the Styrofoam and glue my tubes and dowels. It takes a little pre-thought when designing, but the result is a BalloonSat with the maximum interior volume.

Styrofoam

Lowes is selling sheets of 1/2 inch thick Styrofoam for $10. The sheets are four feet by eight feet and made from the "softer" blue Styrofoam. With 32 square feet of the stuff, you can make an entire fleet of BalloonSats.

Cellfoam 88

One of the nice things about Cellfoam 88 is the various thinknesses they make it in. The thinner sheets are useful for making sheves of compartment walls.

Of course its flat surfaces are another benefit.

The thickest it comes in is 10 mm. A 15 mm thick sheet would be great.

Hot Glue

Really hot hot glue can melt Styrofoam. If you can't adjust the temperature of your glue gun, try unplugging it on occasion. The glue, when it's too hot, metls into Styrofoam. The result is poor contact between sheets of foam.

Styrofoam for Airframes

I prefer the pink 3/4 inch thick Styrofoam sheet for constructing airframes for near spacecraft modules. It has a "harder" texture than the blue sheet.

Cutting Styrofoam

I've noticed a "grain" in Styrofoam. I suspect it extruded and that stretches out the polymer in the polystrene. When you cut Styrofoam with a dull blade, it creates chunks more readily if you cut across the grain.

The moral?
Cut only with a sharp blade and only along the grain if you absolutely must use that dull blade once more.

Hot Glue

Not only does hot glue do a good job assemblying the sides of an airframe, it's also great for covering copper traces. That's because the plastic in hot glue is a very good insulator. It tacks well and if it needs to be removed, you can work off (mostly by peeling it off).

Anderson Power Poles

If you use power poles for your battery connections, be sure to backk fill them with hot glue. This prevents anything small and pointy from creeping into the back of the connectors. Everything electrical in a near spacecraft needs protection from shorts. It's really bad news to have a short at 100,000 feet.

Battery Connectors

I don't use plastic battery holders for critical applications, it's too easy for a cell to pop out. Instead, I use battery "snaps", or plug in connectors. The battery can move around at the end of its cable, but since the cable is flexible, there's no strain on the connector (unless the battery falls out of the airframe (in which case, you've got a lot of other problems).

The kinds of connectors I've used are Anderson Power Poles and Dean's Connectors.

More Batteries

Rechargable lithiums from cell phones are available through surplus electronics catalogs. Be sure to purchase a recharger with them, since lithiums need their own charger to maintain their lifespan. You'll need to solder connectors to the batteries since there aren't battery holders made for them (the phone has its own set of tabs that connect to the contacts in the battery case). I've found three electrical contacts int eh batteries I've nmodified. Two are needed for charging, the third is a control circuit to prevent over charging or over heating.

Near Space Batteries

It can get cold inisde a BalloonSat. Alkaline batteries will have a problem providing current in high drain cases. Normally I use lithium batteries because they can handle -60 degree F temperatures. Good photo-lithium batteries are avilable at Walmart and Target in the camera department.

Packing BalloonSats

The launch and descent after balloon burst can be very chaotic. To prevent the BalloonSat's innards from being bounced to death, either bolt equipment into place or use a filling material.

Bolting can be done with #2-56 hardware to keep it light, but you'll want washers to make the head of the bolts larger. Try using plastic (20 mil thick?) that you can purchase from hobby shops that sell model trains (or other construction type hobbies).

Rubber Bands

Don't use really tight rubber bands to close a BalloonSat hatch. They'll pull too tight and deform the Styrofoam airframe. They're also too difficult to put back on (esspecially if it's cold and the launch crew is wearing gloves). It's bhetter to double up the rubber bands.

Dowels for Hatch Closures

Dowels protruding from the airframe are great for wrapping rubber bands around. The dowels should run through the back of the airframe and extend another 1/2 inch beyond the side of the airframe. Cut a channel as wide as the dowel's diameter and glue the dowl inside. That way the dowel doesn't take up any of teh volum inside the airframe.

Hatch Closures

It may be necessary to open a BalloonSat at the launch site (say to load an experiment or insert a battery). A hatch held closed by rubberbands is ideal for this. Rubberbands can be snapped on and off quickly and with no tools - ideal for the rush during launch prep. I've tested rubberbands on many flights and have discovered they hold up wel for the cold, vacuum, and ultraviolet of near space.

BalloonSat Link Lines

To keep BalloonSats from slipping down their link lines, tie knots in them and connect split rings through the knots. That way there is no force tugging on the BalloonSat. They're free to slide around on the link lines. If you physically restrain the BalloonSat, then the post-burst chaos could rip them apart or otherwise damage them.

Tubing for BalloonSats

Link lines are the cords that tie one or more BalloonSats to a near spacecraft. So they don't tear a Styrofoam BalloonSat apart, there must be a race way attached to the BalloonSat for the lines to run through. Some groups have used flexible vinyl tubing and others ink pens with the guts removed. I prefer to use styrene plastic tubes. They come in a variety of sizes and are available at many hobby stores that sell airplanes, cars, models, and rockets. A 1/4" diameter tube seems to be ideal. Best of all, the tubes are very long and can be cut to the proper length. That way your BalloonSat dictates its proper size, not the tubes you have on hand.

Multiple Lines in BalloonSats

I prefer having at least three lines running through a BalloonSat. A single line connecting the BalloonSat to the rest of the near spacecraft leaves it swinging and twisting around too much. The extra cords dampen out the motion leaving images with less blurring from motion.

Landing

Another simulation that's important is landing. A parachute landing has a speed of about 10 mph. That's the speed something dropped for 0.5 seconds will reach (10 mph is about 15 fps and that's close enough to 16 fps which is reached in 0.5 seconds at an acceleration of 32.2 feet per second squared). In 0.5 seconds, an object falls roughly four feet (distance = 1/2 * 32.2 * 0.5^2). So to simulate a parachute landing, drop the module (BalloonSat) from a height of four feet.

If it can land without blowing apart, then you'll probably get the experiment back in one piece.

Burst Simulation

A burst balloon in near space quickly deccelerates and starts its free fall down. In about five seconds, the near space craft will reach its maximum speed and have fallen 500 feet (based on data from flight NearSys 09D). Video footage shows the parachute opening and closing and the remains of the balloon whipping around. Its very traumatic and its accompanied by lots of jerk (changes in acceleration).

A BalloonSat not properly designed for the post-burst chaos is liable to open up or fall apart.

To test for this situation, tie cords to a broom handle and suspend your total BalloonSat (batteries included) from the cords just like it would be suspended from a near spacecraft. Hold the end of the broom handle away from your face and give the appartus a good shaking.

If your BalloonSat holds up, it's ready for the balloon burst and descent.

An easy aspect of near space to simulate is its intense cold. A styrofoam cooler packed with dry ice does a nice job. But don't let the experiment actually touch the dry ice. Use a cookie rack to hold the experiment above the dy ice. Even colder temperatures can be reached if you add a fan or two to circulate the air Run their power cables outside the enclosure as there's no need to chill the power source of the fans.

Expect temperatures to drop to at least -60 deg F on ascent to near space. Your dry ice chamber shuld be able to get close. Brrrrrr!!!

Nuts and Volts Article

I submitted an article to Nuts and Volts about the environmental test chamber I built. Read it to see how you can convert an airtight flour cannister into a ultra-cold and low pressure test volume for experiments.

Tape

After gluing an airframe together, wrap it in tape. I use a thin colored tape used to wrap styrofoam gliders. By wrapping the airframe, you put tension in it to keep the sides together. Glue can keep the sides from sliding relative to each other, but tape puts the inward force on them that helps keep them together.

Uline makes a wide selection of tapes.

Avoid aluminum duct tape as it adds unnecessary weight and creates a heat shink to draw heat out.

Extreme BalloonSat Flight Computer

I'm about to test an extreme version of a BalloonSat flight computer. It uses a BS2p and a MAX186 (12-bit ADC) and will run many more experiments than is normally on a BalloonSat. This is for a BalloonSat where multiple teams design experiments and share computing resources. It includes a GPS port for any experiment wanting to knowthe time/altitude All it needs is a radio/TNC to be a full up flight computer with tracking capability.

I envision tis being used by an entire classroom.

More on Cellfoam 88

Cellfoam 88 comes in multiple thicknesses. I found 3, 5, and 10 mm sheets at the Hobby Lobby. Not only that, but at least in Kansas, the store is having a sale. I got some wood for robot bodies at 50% off.

There's a tape for gluing Cellfaom 88 together. Don't use that for a BalloonSat airframe, instead use a bead of hot glue. Then cut out any ports and openings. Afterwards you can wrap the airframe in thin colored tape.

ARBONET has been recovered. It landed in Redfield, Kansas and is on it's way back home.

I've finished the initial design of a flight computer that incorporates a radio. Just plug the GPS in and you're ready to go. I hope to get a test board sent to BatchPCB within a week. I call the design the NearSys UltraLight.

Great Plains Super Launch

Well, GPSL was a success. At least nine balloons were launched from the courtyard/parking lot of my school. All but one were recovered. I'm hoping ARBONET receives a phone call about their capsule before long.



NearSys 09E reached an altitude of around 80,000 feet. The exact altitude if not known becuase the GPS was acting up. The backup tracker only produced five posits on descent. It transmits now, so I checked the battery and found it was 8.0 volts (nominal 7.2 V lithium). So I suspect the capsule was accidentally shut off or it has a bad power switch. I'll get this debugged before the next mission. This is why NearSys flies two independent trackers on every mission.



Recovery occured in Garnett, where at least three other capsules recovered. This has got to be the biggest news for this town!



A homeowner was setting his sprinkler when he heard a rustle in his tree. He turned around to see the capsule and parachute descend along the side of his tree. He was 10 feet away when this happened. It looks like the downward camera can see him shortly before landing.

This is the highest image, taken around 80,000 feet. That cumulonimbus cloud was on the horizon as the near spacecraft lifted off. At this altitude we're so high that we can see the horizon beyond the cloud.

So I'm looking for a another opportunity to fly. I have a thermopile telescope to test.

GPSL 2009

Tomorrow begins the ninth annual Great Plains Super Launch. I hosted the first two and am now doing it again. The first GPSL (in 2001) was a single day event and launched three weather balloons. This year is another first. It's three days old, we have a tour of Garmin, and we're watching the Topeka Premiere of the movie, Blast!

I'm launching a near spacecraft carrying the following experiments.
Thermopile Telescope
Weather Station
Geiger Counter
Accelerometer
Still Digital Camera
Two Digital Video Cameras

Mark Conner is predicting great weather for Saturday's launch. I'm really looking forward to GPSL this year. I'm the only person to attend them all.

Onwards and Upwards

Wiki's and Blog's

Now that I've created a Wiki and a Blog, I see a few difference between them.

Blog's have very much a single direction. I post updates to them for people to read. While people can make comments, their input is not as significant as my initial posts.

Wiki's are very bi-directional and collaborative. Regardless of who creates an entry, everyone is treated as an equal. in fact everyone is expected to add input equally.

How would I use Blogs and Wikis?
I would use a blog to post information, notes, link, and videos to my students. If they have a question, they could make a comment. But notice the blog is very teacher centered.

I would set up a wiki for teams of students to talk to each other. It allows them to collaborate and learn together.

Environmental Chamber Demonstration

Here's a short clip of my environmental chamber. It's a cheap way to test instruments and experiments for the cold, vacuum, and radiation in near space.

Demonstration of a CheapBot Robot

14 July 2009

First post. Look for news about astronomy, near space, and robotics from NearSys