PC voltmeter / datalogger

Take a look at:

for $25 you couldn't built it for that. They also have a USB unit for $50

Don

On a sunny day (Fri, 22 Dec 2006 12:31:32 -0500) it happened "Don Cleveland" wrote in :

I have a Philips PCF8591 AD / DA chip via i2c on the parport. It gives me 4 channels analog in and one channel analog out. Connected via an audio 'diode cable' (2 x single screened). The ref is a LM317, and the thing runs on an AC / DC adapter, but you could just as well grab 5 V from the parport, that chip uses micro amps. It is is an 8 bit ADC, and I added input protection etc... It costs 6Euro30 or maybe 10 $.

has been working now for eeh 12 years and still going strong. I2C protocol via parport has the advantage that in a multitasking OS interruptions in the data or clock due to task switch delays have no effect and cause no errors. I also have some PCF8574 IO expanders to do digital IO on the same bus.

Don Cleveland wrote

Don, thanks for the link ..I hadn't found anything prepackaged for under $150

Stew

Be advised that the 194 has a fixed input range and a relatively low input impendence. It's fine for a lot of things (and may be great for your application), just know what you're getting.

A lot of supplemental info on the 194 and its relatives is available at

--
Rich Webb   Norfolk, VA

the analogue pins of the joystick port can be used as a crude ADC over a limited range.

V ---/\\/\\/\\---+---->|----+5V | `----------joystick input -----------------------0V response is inverse-linear - ish so it won't go all the way to 0V, a pull-up could probably be added parallel to the diode to fix that. for high voltage make the resistyor large. every system is different, so you'd have to characterise it yourself. precision will be no better than the stability of your PC's PSU.

Bye. Jasen

Jasen, is the diode in backwards? What does it do?

Regards,

Mike Monett

Antiviral, Antibacterial Silver Solution:

SPICE Analysis of Crystal Oscillators: Noise-Rejecting Wideband Sampler:

OK, never mind. I found some good sites that explain more how the game port works, and it doesn't appear to do what I need.

Just for reference, here's some info on this interface:

Tomi Engdahl has probably the best site:

Regards,

Mike Monett

Antiviral, Antibacterial Silver Solution:

SPICE Analysis of Crystal Oscillators: Noise-Rejecting Wideband Sampler:

over-voltage protection. the joystick input is basically current sensitive (on old hardware it was a LM558 or LM556 based monostable with the joystick being the 0..250K timing resistor to +5V )

Bye. Jasen

Thanks. As I found out, the game port is really slow and not very accurate. I listed some url's in another post. You can do a lot better on the parallel port.

I think I have an idea for sending binary data on the soundblaster. This would allow response to DC and give reasonable data transfer rates very inexpensively. Just encode the data in MFM. It has no DC component, and you can use illegal codes for the sync byte.

Regards,

Mike Monett

Antiviral, Antibacterial Silver Solution:

SPICE Analysis of Crystal Oscillators: Noise-Rejecting Wideband Sampler:

My first thought was an FPGA experimenters kit on USB for about $49, it even includes toolkits for doing almost anything with the on board ADC and DAC.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller