Shop lighting upgrade: T5 vs T8 fluorescent vs LED

I am in the process of upgrading the lighting in my shop. It currently has a number of 4-lamp and 2-lamp T12 4-foot fluorescent fixtures. The best solution is to replace the ballast in each of these fixtures with high-efficiency electronic ballast ($15), and replace the lamps with T8 high-CRI bulbs. This will save energy, and greatly improve the quality of the light. LEDs and T5 fluorescent are MUCH more expensive to install, and their energy savings are not nearly enough to justify the cost. Most LED systems actually use more energy than T5 or T8. Remember that running a T8 with an electronic ballast will provide more light than it's nominal rating, which is for magnetic ballasts. T5 are always rated for electronic ballasts, so it is not a fair comparison.

For new fixtures in my shop, the cheapest/best solution is to buy $10 "shop lights" and replace the ballast. The total fixture cost is $25, and efficiency is 96 lumens/watt for a total output of almost 6000 lumens. It can't be beat! Commercially-available T8 fixtures with electronic ballasts are more expensive, and the quality of the ballast is suspect.

National Instruments USB-6501 minimum sampling interval

I have a project where I need to collect some parallel digital data with a computer and store it in a plain text file. Ideally the file would look like this:

t (s) Value
0.000 130
0.005 127
0.010 126
0.015 127
0.020 200

Value is the decimal equivalent of 8 individual binary data lines.

This data collection could be achieved via the parallel port with custom software, however I'd rather use USB, and I'd also like to collect 2 separate 8-bit signals. I've used National Instruments products before, and figured the USB-6501 might be a good choice for this project. I called NI, and asked specifically about the sample rate. The technical salesperson did not have a clear answer. The best answer was "about 900Hz", but it was unclear whether this referred to the sample rate of a single digital line or all 24 lines that the device provides.


I bought the USB-6501 and tested it out with the included SignalExpress freeware from NI. As it turns out, the minimal sampling interval for two 8-bit signals is about 15ms (eg 67Hz) on my Core2Duo 2GHz with USB 2.0. Yeesh. I think that's pretty lousy, and it will not work for my application.

What's really annoying is that the program will not indicate what the minimal sampling interval is. You just have to take a guess and then run the data acquisition and test it. I also noticed that generating a CPU load on the machine will cause the data acquisition to halt if the minimal sampling interval cannot be reached. So, if you keep lowering the interval, keep retesting, and find that 15ms appears to work, you may find when you start another program or move a window, the CPU becomes ever-so-slightly more loaded and the acquisition will fail. Oops. Overall, the USB6501 is only good for very low-speed applications.

I will continue my project with an NI USB-6008 and use a digital-to-analog converter to convert my 8-bit signal into an analog voltage, then use the 6008 to record the voltage. It seems a little backward, but I cannot see any other low-cost high-speed digital USB devices from NI. Do you have any suggestions?