Circuit Simulation

My electronics projects have gotten complicated enough to give me a headache.  To surrender to this complexity I started using a circuit simulator application.  The one I downloaded is FREE and seems pretty good.  It is called LTspice (spice stands for Simulation Program with Integrated Circuit Emphasis).  The program is available for download by anyone at: http://www.linear.com/designtools/software/.

I also found a Java-based program available as a web applet here for very simple things: http://www.falstad.com/circuit/

Cheap(ish) Commutator for Tethered Recordings

A friend pointed me to a very useful product for those of us who connect wires to freely moving animals.  It is a slip ring commutator manufactured in china by Hangzhou Prosper Mechanical and Electrical Technology Co and sold here in the US by adafru.it.  This commutator moves quite freely and is available with many channel options (the 6 channel goes for $17.50).  I got my hands on a few and am now contemplating using this as my commutator for ephys recordings.  The company makes a 32 channel version which is sold for about $350.  I will first test the one I have with my sniff sensor.

Hacking Agama V-1325R IR Camera

As part of my research, I do experiments with rodents (rats).  I train rats to do a number of tasks that allow me to ask them how they perceive odors.  Rats like to work in the dark and I monitor them with an IR camera.  As a cheap IR camera, I bought an Agama V-135R cam with built-in IR LEDs.  However, one annoying thing about this camera is that the IR LEDs must be turned on via software and are programmed to shut off every 45 mins.  I just want them to be on all the time!  So I opened up the camera and found a way to keep those guys glowing!  The LEDs were wired as two garlands of 2 leds plus a 50 Ohm resistor.  This makes sense:

USB Vcc = +5VDC
IR LEDs drop = ~1.75 V Each
Leaving 1.5 V dropping over R=50 Ohms --> I = 30 mA

The two garlands go to ground through a transistor.  I simply shorted the transistor with a fine copper wire!

There are 4 LEDs on the Agama 1325R connected as two garlands.  They receive power from a 5V Regulator and go to ground through a transistor switch (right top).  I shorted this transistor with a fine copper wire.

Mass Flow Sensor: ~$100

Just a note, to measure the air flow through my MFC, I was using an independent mass flow sensor.  I bought it directly from a Honeywell sensor distributor for ~$100:

AWM5101
http://sensing.honeywell.com/honeywell%20sensing%20and%20control%20product%20search?sid=1361C81FF163&Ne=3025&N=3468

The sensor is very easy to use, but I just added on some ports for power in and a BNC.  If you already have a scope or a PC with a DAQ, this let's you measure flow and for much less than $1000.