port from excessive input voltage. To learn more about the PC parallel port, there is a Parallel
Port FAQ located on our Web site.
Can I damage the A/D if I accidentally exceed the maximum input voltage?
The input to the A/D are protected by internal clamping diodes as well as a current limiting
resistor. It provides a fair amount of protection. We have tested the Mini Daq with a 9volt
analog input source without any problems for a short period of time.
How do I interface relays and other devices to the Mini Daq.
We have provided circuits on our web page in PDF format to do this. If you have further
questions feel free to email us.
How can I increase the A/D sample rate?
Sample speed varies with the speed of your PC. The faster your PC, the higher the sample rate.
Although the A/D chip is rated at 133 Khz sampling rate, sampling frequency is quite effected
by software overhead and by Windows itself. You can run in a Dos environment to get better
results. We have provided interface libraries to C and Quick Basic. In Labview, optimized loops
will significantly increase your sample rate.
I’m getting A/D fluctuations every time I control an output port
.
Connect unused A/D inputs to ground. You might be drawing too much current from the
parallel port, effecting the power input to the Mini Daq. Try switching to external power such as
a 9V battery.
Why does my Mini Daq not work with jumper JP4 set to INT power?
We have designed the Mini Daq with the option to get its supply voltage from the PC parallel
port. Some parallel port adapters may not be able to supply enough current to fully power the
Mini Daq. This is common with laptop computers that use low power 3.3 volt logic circuits. If
you are experiencing this problem, set jumper JP4 to the EXT setting and connect an external 6
to 12volt supply to Pin 13 of DB25 connector P2. A 9volt battery works quite well for this.
Trouble shooting
Check and make sure all components are installed and properly orientated.
Check diode polarity.
Check IC positions.
Check Tantalum capacitor polarities.
Check for shorts
Check for cold solder joints, especially around RP1 and U1.
Cable from PC to Mini Daq should be 6 foot or less. Shorter is better.
Try external power, PC port may not provide adequate power
