Quarters In My Change Jar

Written 2018-01-01

Tags:Statistics Math 


To evaluate the feasibility of an upcoming project, I needed to know the approximate distribution of quarters in circulation in the local area. Upon filling my change jar, I filtered out the quarters and counted them. There were 102 quarters.

Trial was repeated 5 days later with 400 quarters from a local bank, then another 400 quarters and results were summed.

By Year

102 Quarters502 Quarters901 Quarters
ByYear ByYear502 ByYear901
By year the data is a little hard to digest.

By Decade

102 Quarters502 Quarters901 Quarters
ByDecade ByDecade502 ByDecade901
By binning the data into a point per decade we can get a clearer picture. I think there are a few possible effects here, but the data is so noisy I wouldn't claim anything:

Other work

Rhett Allain at wired has a similar piece up.

Ernest James Zydeco

Written 2017-12-24

Tags:ErnestJamesZydeco Zydeco Music 

A few weeks ago, I had the pleasure of photographing Ernest James Zydeco at Kansas City Oasis. These are a few of my favorite shots from that Sunday.




Rooting your Televerge/BandLuxe K530S

Written 2017-12-10

Tags:BandLuxe Televerge Root SSH 


A seemingly defunct local telecom vendor, Televerge, sells cellular M2M connectivity solutions. They also dump their used prototype hardware at the thrift store. It turns out the OEM router at the center of their product is a BandLuxe K530S.

WebUI Access

I only need to turn this device into a router, so a hard reset brings it back to a state where username and password of admin can access the webui.

BandLuxe K530S


Download the configuration backup

Under system/backup you can download a configuration backup, and extract it to find it is a tarball of a bunch of files/etc.

BandLuxe K530S

Insert a backdoor

A simple second username mapped to uid 0 works great.





Assembly is the reverse of disassembly

Just tar up the files, and upload them, wait for the router to reboot, and:
rsaxvc@x220:~/code/bandluxe/etc$ ssh
rsaxvc@'s password: 

BusyBox v1.19.4 (2014-12-09 16:04:25 CST) built-in shell (ash)
Enter 'help' for a list of built-in commands.


Brushed ESC Overvoltage Failures

Written 2017-10-26

Tags:Motors ESC 

A brushed DC motor ESC(Electronic Speed Controller) is a relatively simple device with only a few things to do, so it is interesting to consider what might happen when one is taken outside of its designed operating parameters. Today I needed some cheap ESCs to run on higher voltage than designed, and one of them did not quite make it.

An ESC has at most a few subsystems:

They usually only fail from overvoltage in a few different ways:

Today we connected two ESC to first 12V, then 24V, and attempted to drive a 1980s industrial robot. The first ESC, a 10A Hobbypower Rc ESCa, is designed for up to 8.4V and uses an IRFS3006 H-bridge. At 12 volts, the little controller was able to smoothly accelerate our robot, though it was a bit slow. BEC output remained steady at 6V. The second ESC, a 60A Hobbywing Quicrun, is designed for 12V systems and performed admirably with little lag or ramp-up, however due to the larger current drivers it could brown out our test supply if the robot were commanded to move too quickly.

At 24V the plot thickens. The Quicrun ESC functions just fine. However the Hobbypower ESC failed catastrophically at 24V, destroying the ESC, receiver, and an innocent servomotor. Postmortem indicates that the BEC failed, shorting the 24 volt battery voltage into the BEC output. Once the BEC output rose above 6V, the failure cascaded to the reciever, which connects to more servos, destroying them as well.

Reviving an old Seiko TT4000SC

Written 2017-10-26

Tags:Motors TT4000SC Seiko 

Someone dropped off an old industrial robot at Hammerspace. After a while stored in the back, and a move to a new location, thisisradionick and I decided to get it running.

The Seiko TT4000SC consists of two major components, a 4-axis robot(Z,shoulder,elbow,wrist), and a control box. Our control box had a sticker noting that the RAM battery had been replaced about 10 years after it was manufactured, and never again. Our first plan was to set up the control box, but since our RAM battery was long dead, it simply reported a large number of errors, including being uncertain what model it was attached to. Since the robot model appears to have no semiconductors to speak of, I suspect the model number was a setting in the RAM, and bringing this robot back to full operation will require repeating some of the inital programming steps that had occured in the 1980s. Needless to say, spare TT4000SC factory programmers are in short supply. We do plan to work on the control box separately, but decided to crack open the robot case to see what was inside.

Each axis consists of a 24V motor, encoder, reduction gear box, encoder, end-stops, and linkage. After Craig was able to help us order a Japanese Airplane Electronics connector, we tapped directly into the motors:

Eventually we could design our own control boards or use OpenServo, but for today we used remote control boat ESCs, which should be good enough for getting a fruit ninja game ready for Maker Faire.