Monthly Archives: September 2009

Repair Ideas

Conductive Ink looks like a production grade solution to minor circuit board design errors that would normally be solved by green wiring.

See also: electrical tape.

Flexible copper laminates look a little expensive but I also don’t need 10 meters x 500 mm to make one replacement flex cable or some arbitrary new sensors.

These connectors are also pretty awesome.

The spice must flow

Sometimes you have analog problems, and unfortunately not every analog problem can be solved digitally in the Z-Domain. Therefore analog analysis tools like spice are useful when designing complex circuits.

If you want a book on spice I liked SPICE by Roberts and Sedra which you can get at Amazon.

Otherwise there is some good online documentation available.
ngspice manual
Spice3 User Manual

If you like the gEDA tool set you will love easy-spice. Personally, I think gschem needs some work before I can use it regularly. The main problems are that the drag and drop interface for manipulating nets is awkward and annoying to use and editing the values and attributes of components takes way too many steps.

gspiceui looks interesting but relies on Gwave for graphing waveforms. Unfortunately the version of Gwaves that comes with ubuntu is broken and painful to use.

So, the best bet seems to be editing the netlist with a text editor and running ngspice by hand, but at some point I should probably build the gEDA tools from source to see if they are any more usable.

Example Inverting 2:1 inverting opamp.cir

ngspice -b opamp.cir

opamp.cir
Op Amp Example
* ASCII Output setup
.opt nopage
.width in=72
.width out=80
* Ground is node 0
* Inverting Amplifier with Pseudo-Ideal Opamp
* Eopamp [Vout node] [Vin node] [V+ node] [V- node] [Gain]
Eopamp 1 0 0 2 1e6
* R# [input node] [output node] [value]
R1 3 2 5k
R2 2 1 10K
Rload 1 0 100
* Vi [V+ node] [V- node] DC [DC voltage] SIN ( [V0] [Va] [f] [delay] [damping]
Vi 3 0 SIN ( 0V 1V 10Hz 0 0 )
*
.op * Operating point analysis
.control * Execute these statements as commands after loading simulation
set hcopydevtype=postscript
set hcopyfont=DejaVuSans-Bold-ISOLatin1
set hcopyfontsize=32
set hcopypscolor=true
set color0=rgb:f/f/f * background color
set color1=rgb:0/0/0 * foreground color
* transient response
* tran [step] [stop] [start] [max step]
tran 0.250u 0.200 0.00 0.100u
plot tran v(1) v(3) * plot the transient response of the input and output
hardcopy opamp.ps v(1) v(3) * output plot to postscript
.endc * end control commands
.end * the end...

Super Random Roundup

Here is an extra random robotics related link roundup.

Maybe you need detailed topographic USGS Maps, from the Libre Map Project, for your next robotics project.

If you are American, your tax dollars also paid for these U.S. Army metalworking training manuals.

If you are tired of zeroing the Z axis every time you change tools on your CNC machine, perhaps these stop-rings would help.

This Kanban fastener management system allows you to quickly determine when your robotics startup needs to reorder #0-80 screws.

Notice the robot’s Ackermann steering setup in this video.

The original GeekPort specifications might be useful as a reference. A DSP class might be handy as well.

Let’s reuse financial data visualization techniques for robotics. This should be useful for monitoring data such as power usage.

An old Pro/CABLING tutorial for managing all those power cables and flexible solar panels for your solar powered UAV, or maybe you want to use an engine.

A quick lat/lon distance calculator.

Post Vacation Roundup

This how-to video makes fiberglass look really easy to work with.

I wish there was a how-to for removing spray paint from an LCD monitor screen. I need to find a solvent that dissolves the paint but does not dissolve the screen. so far the solution seems to be scraping the paint off with a super thin double sided razor blade. I do not recommend this or getting paint on your monitor. Screen protectors should probably be mandatory for lab computers.

Aside from the small minor fact that the nozzle ring does not prevent the nozzle from being depressed enough to spray paint on to your lab monitor, I strongly suggest Montana GOLD for all of your robot painting needs. Compared to Krylon there are no drips and it feels like there is more paint in the cans. Also the interchangeable caps work way better then the new Krylon ones. It also looks like Montana is popular with the professional users of spray paint.

On another note, I wonder how hard it would be to get robotic sailboats to swarm.