Data logger using PDA - advice needed

Hi there

I am looking for some advice as to where to start to put my iPaq 2200 to work as a datalogger.

As a person with little electronics knowledge and experience (but I am willing to learn), I want to connect the following:

signal -> voltage -> multiplexer -> RS232 (or USB) interface -> iPaq ->

CF card

I am looking to log about 10 channels at 5-10Hz. I can probably deal with the signal to voltage interfaces, some being frequency to voltage,

others temperature, others pressure etc.

I have downloaded the Microsoft eMbedded tools (VB and C++) which will (hopefully) allow me to write an application for the iPaq.

My question for you guys is; can anyone point me in the right direction

for circuit diagrams/designs for multiplexers that can connect via RS232 or USB? Or even a DIY project to do the whole job.

Thanks in advance

PP

Reply to
Pashlipops
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List the specific signals, with their extremes.

See first request.

I have previously coded for PalmOS. I have a friend who did as well. When he went to attempt Windows he gave up fairly quicky due to the tools. It may have changed, but look into it and give it a try before you get too deep w/ Windows.

You will get plenty of help here. I would suggest the CCS complier for PICs. It is free for some basic PICs (you should be able to work with them w/ a MUX instead of dedicating pins for each signal....

I would suggest starting w/ a development board from somewhere to get started with. That will ease the troubleshooting of the ENTIRE circuit. If you get problems, it will probably only be with your portion....

Until you give folks a better idea of what signals, it will be difficult to suggest specifics.

John

Reply to
jecottrell65

Thanks for your response.

The signals will be in the 0-12v range, measured from automobile instrumentation.

Reply to
Pashlipops

I would suggest a couple of MM74HC4051/2 (8 channels analog mux). They are cheaper than the high end micros for test burnings. You just need to down shift the input to 5V or less. I run my AVR and 4052 at 2.7V (two NiCd charged from a 12V switching regulator). When parked, my logger (and alarm) would drain from the NiCd, but not the car battery.

Reply to
linnix

Just in case you're not aware (please forgive me if you are), the nominal operating bus voltage will be about 13.5 VDC, not 12. During a load dump, though, expect up into the 60 to 100 V range; during alternator field collapse, down into -60 to -80 VDC.

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Rich Webb   Norfolk, VA
Reply to
Rich Webb

Yes, we have a 10:1 voltage divider and input clampings to 0V and 2.7V (VCC). The micro can only measure up to VCC anyway. We don't really care about the range outside, so two heavy duty diodes are good enough.

Reply to
linnix

The PIC 16F877 chip has A/D converters built in, 8 inputs. So, you could MUX 4 of the inputs to get to 12 inputs ( The PIC has a lot of pins you could use to control the MUX )

Sparkfun Electronics have development boards for PICs at reasonable prices and one of them has a built on PIC to USB converter. Or, another board has PIC to RS232.

Oh yeah, the PIC 16F877 can have a bootloader installed so it is easy to write a program and load the PIC. If there is a bug, just fix it and then upload the code again. Convenient.

There is enough program space in the PIC to allow the PIC to input and convert the A/D readings and then feed them to the computer fast enough to probably do everything you need with a lot of CPU time left over.

Jim Pennell

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21:05 Pacific Time Zone
Aug 21 2006
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Reply to
Jim

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